CN101005262A - Ac generator sensor-less vector control method and control device thereof - Google Patents

Abstract

The invention provides a sensorless vector control method of an AC motor and a control device thereof, which can stably restart the AC motor in a free running state. In the present invention, when the AC motor (2) is restarted, the current flowing through the AC motor (2) continues for a set time at a state equal to or greater than the set current level, and it is judged as an estimation of the rotation direction or speed It is a wrong guess, and the rotation direction and speed of the AC motor (2) are estimated by applying a DC current or a DC voltage again.

Description

Sensorless vector control method and control device for AC motor

This application is a divisional application of an invention patent application with an application date of July 2, 2003, an application number of 03816326.8 (PCT/JP03/08423), and an invention title of "Sensorless Vector Control Method and Control Device for AC Motors" .

technical field

The present invention relates to a sensorless vector control method of an AC motor and a control device thereof, which are characterized in that, when starting the AC motor, the speed of the AC motor in a free running state is estimated, and by making it run at the estimated speed, a smooth ground to start the AC motor.

Background technique

The applicant proposed a control method for an AC motor in JP-A-2001-161094, which is used to control an AC motor equipped with a current control unit without a speed detector and a voltage detector. The control unit has a power converter that outputs power to the AC motor, and controls the output current of the power converter based on the deviation signal between the current command signal and the output current detection signal of the power converter. The control method includes a power converter that outputs power to the AC motor. The current control part of the converter, the current control part controls the output current of the power converter according to the deviation signal between the current command signal and the output current detection signal of the power converter, and when the AC motor is in a free running state, An arbitrary DC current is supplied only for a set time, a frequency component appearing in an output current detection signal of the power converter is detected, and the speed of the AC motor is fully estimated from the frequency.

In addition, the following control method is also disclosed. When the AC motor is in a free running state, the current command signal is forcibly set to zero to perform current control, so that the current of the AC motor is zero, and using this time Based on the output voltage command signal calculated from the output of the current control unit, the magnitude, phase, and angular velocity of the residual voltage of the AC motor are obtained, thereby estimating the rotation direction of the AC motor in a free running state. and speed, thereby smoothly starting the AC motor in the free running state.

Also disclosed is a control method in which, when the output voltage command signal calculated using the output of the current control unit when the current command signal is zero by current control is lower than an arbitrarily set voltage level, Stop the current control, apply a DC current command of any size to any direction at the set time, and then apply a current command of any size to a direction that changes 180° from the command direction of the DC voltage, and then apply a current command of any size at the set time Carry out current control, detect the frequency component and its phase relationship in the current detection value, estimate the frequency component as the speed of the AC motor, and estimate the rotation direction from the phase relationship.

However, in the method described in the aforementioned JP-A-2001-161094, when a large amount of residual voltage remains in the AC motor, the estimated speed may differ from the actual speed of the AC motor due to the influence of the residual voltage. . In this case, when starting at a frequency corresponding to the speed estimated by the power converter, a large current may flow through the AC motor to operate the AC motor at a speed close to the erroneously detected speed. Cannot start smoothly again.

When the responsiveness of the current controller is poor, it is difficult to reduce the current of the AC motor to zero, so that the power converter is brought into an overcurrent state, and smooth start cannot be performed.

In addition, when the AC motor is an induction motor, since the residual voltage gradually decreases during free running, it is easy to make the current of the induction motor zero. However, when the AC motor is a permanent magnet synchronous motor, When running freely at high speed, a large induced voltage is generated, and it is not easy to make the current of the permanent magnet synchronous motor zero.

In addition, when the AC motor is freely running at high speed, the detection resolution of the frequency appearing in the current detection value deteriorates, the signal amplitude of the frequency component appearing in the current detection value becomes small, and the frequency cannot be detected.

In addition, in the above-mentioned Japanese Patent Laid-Open No. 2001-161094, with regard to the control method of the AC motor described, it is only described that when the AC motor is in a free running state, an arbitrary DC current is supplied for a set time, but there is no A method of determining this set time will be specifically described.

In addition, in the control method of the AC motor described in Japanese Patent Application No. 2002-80891, the preset frequency and the detected rotation direction are set in the frequency adjustment circuit, and the torque current detection value is input. If the torque current detection value is Positive, then reduce the output frequency, if the torque current detection value is negative, then increase the output frequency, adjust the output frequency to make the torque current detection value close to 0, so that the AC motor and the power converter in the free running state The output frequency is the same, so as to start smoothly.

However, in this case, although the output frequency is adjusted so that the torque current detection value approaches zero, there may be cases where a smooth restart cannot be performed.

Contents of the invention

The present invention is proposed to solve these problems. Its first purpose is to provide a sensorless vector control method and control device for an AC motor, which can estimate the rotation direction or speed when the AC motor is restarted in a free state. In the case of an error, it can be quickly judged as a wrong guess, and the AC motor in the free running state can be restarted smoothly,

Also, by correctly setting the application time of the DC current applied to the AC motor when the AC motor in the free running state is restarted, the AC motor in the free running state can also be restarted smoothly.

In addition, the second object is to provide a sensorless vector control method and a control device for an AC motor. When the responsiveness of the current controller is poor, or the AC motor is not an induction motor but a permanent magnet synchronous motor Under certain conditions, it can continue to operate reliably and smoothly.

In addition, the third object is to provide a sensorless vector control method and a control device for an AC motor, which can realize current control by forcibly setting the current command signal to zero so that the current of the AC motor is zero, in this case, improve the responsiveness of the current controller, so that the power converter does not form an overcurrent state, and can continue to operate smoothly; when providing a DC current command to the AC motor, and estimating the speed of the AC motor In the case of free running of the AC motor at high speed, the frequency detection accuracy is improved; even in the case of free running of the AC motor at high speed, it can continue to run smoothly.

In order to achieve the above object, the sensorless vector control method of an AC motor according to one of the present invention is a sensorless vector control method for an AC motor without a speed detector and a voltage detector, including: outputting any power to the AC motor A power converter; a current detection circuit that detects the current supplied to the AC motor; a coordinate conversion circuit that converts the current supplied to the AC motor into an excitation current detection value and a torque current detection value and outputs them; controls the direction voltage of the excitation current an excitation current control circuit for making the excitation current command value consistent with the excitation current detection value; a torque current direction voltage control circuit for making the torque current command value consistent with the torque current detection value a torque current control circuit; a V/f conversion circuit for calculating an induced voltage of an AC motor based on a supplied output frequency command; a phase angle calculation circuit for calculating a phase angle obtained by integrating the supplied output frequency command; and Based on the voltage command output from the excitation current control circuit, the torque current control circuit and the V/f conversion circuit, the output voltage operation circuit calculates the magnitude and phase of the output voltage, and calculates the output voltage from the output voltage. The magnitude and phase of the voltage output by the circuit are added to the phase angle output from the phase angle calculation circuit, and the switch of the power converter is determined, and when the AC motor in the free running state is started, the AC DC current or DC voltage is applied to the motor, and the rotation direction and speed of the AC motor are estimated from the secondary current flowing at this time, and the rotation direction and the frequency corresponding to the speed are set in the frequency adjustment circuit and started, by The frequency adjustment circuit makes the output frequency coincide with the speed of the AC motor, and is characterized in that, based on the magnitude of the current flowing through the AC motor, it is estimated that the rotation direction and frequency set in the frequency adjustment circuit are different from those of the actual AC motor. There are deviations in the direction of rotation and speed.

The second aspect of the present invention is that, in the sensorless vector control method of an AC motor according to the first aspect of the present invention, it is estimated that the rotation direction and frequency set in the frequency adjustment circuit are different from the actual rotation direction and speed of the AC motor. The standard of the deviation is that the current flowing through the AC motor continues for a set time at a state equal to or greater than a set current level.

The third feature of the present invention is that in the sensorless vector control method of an AC motor according to the first or second invention, it is estimated that the rotation direction and frequency set in the frequency adjustment circuit are different from the actual rotation direction and frequency of the AC motor. If the speed deviates, then interrupt the restart of the AC motor, apply DC current or DC voltage to the AC motor again, and re-estimate the rotation direction and speed of the AC motor according to the secondary current flowing at this time. In the adjustment circuit, set the rotation direction and the frequency corresponding to the speed again, and start again.

The fourth aspect of the present invention is characterized in that, in the sensorless vector control method of an AC motor according to the third aspect of the present invention, after applying a DC current or a DC voltage to the AC motor, and re-estimating the current flow rate based on the secondary current flowing at this time. When the rotation direction and speed of the AC motor are mentioned above, the estimated value of the speed is estimated to be a value lower than the previously estimated speed by the set speed, or the final output value of the frequency adjustment circuit is set to the upper limit value. A frequency corresponding to this estimated value is set in the adjustment circuit and started.

A sensorless vector control device for an AC motor according to a fifth aspect of the present invention includes: a power converter for outputting arbitrary power to the AC motor; a current detection circuit for detecting the current supplied to the AC motor; and converting the current supplied to the AC motor to A coordinate conversion circuit that outputs the detected value of the excitation current and the detected value of the torque current; an excitation current control circuit that controls the direction voltage of the excitation current so that the command value of the excitation current is consistent with the detection value of the excitation current; controls the direction of the torque current Voltage, the torque current control circuit that makes the torque current command value consistent with the torque current detection value; and the V/f conversion circuit that calculates the induced voltage of the AC motor according to the output frequency command provided; the calculation is passed A phase angle calculation circuit for a phase angle obtained by integrating the provided output frequency command; calculating an output voltage based on the voltage command output from the excitation current control circuit, the torque current control circuit and the V/f conversion circuit The magnitude and phase of the output voltage calculation circuit, the device is to add the magnitude and phase of the voltage output from the output voltage calculation circuit and the phase angle output from the phase angle calculation circuit to determine the power converter The control device of the switch, and the AC motor does not have the speed detector and the voltage detector for the processing, when starting the AC motor in the free running state, a DC current or a DC voltage is applied to the AC motor, according to which The rotation direction and speed of the AC motor are estimated from the secondary current flowing at the time, the rotation direction and the frequency corresponding to the speed are set in the frequency adjustment circuit and started, and the output frequency is set by the frequency adjustment circuit to match the AC motor. The speed of the motor is consistent, and it is characterized in that an incorrect setting estimation unit is provided to estimate the rotation direction and frequency set in the frequency adjustment circuit and the actual rotation of the AC motor based on the magnitude of the current flowing through the AC motor. There is a deviation in direction and speed.

According to a sixth aspect of the present invention, in the sensorless vector control device for an AC motor according to the fifth aspect of the present invention, the criterion for estimating an incorrect setting by the erroneous setting estimation unit based on the magnitude of the current flowing through the AC motor is: , the current flowing through the AC motor continues for a set time at a state equal to or greater than a set current level.

The seventh aspect of the present invention is characterized in that, in the sensorless vector control device for an AC motor according to the fifth or sixth aspect of the present invention, the incorrect setting estimation means interrupts the restart of the AC motor after estimating an incorrect setting, Apply DC current or DC voltage to the AC motor again, re-estimate the rotation direction and speed of the AC motor based on the secondary current flowing at this time, and set the rotation direction and the speed in the frequency adjustment circuit again. frequency and start again.

The eighth aspect of the present invention is that, in the sensorless vector control device for an AC motor according to the seventh aspect of the present invention, after applying a DC current or a DC voltage to the AC motor, and re-estimating the current flow rate based on the secondary current flowing at this time. When the rotation direction and speed of the AC motor are mentioned above, the estimated speed value is estimated to be a value lower than the previously estimated speed by the set speed, or the final output value of the frequency adjustment circuit becomes the upper limit value. Set a frequency corresponding to the estimated value in and start.

The ninth sensorless vector control method of an AC motor of the present invention is a sensorless vector control method for an AC motor without a speed detector and a voltage detector, comprising: a power converter that outputs arbitrary power to the AC motor; A current detection circuit that detects the current supplied to the AC motor; a coordinate conversion circuit that converts the current supplied to the AC motor into an excitation current detection value and a torque current detection value and outputs them; controls the excitation current direction voltage so that the An exciting current control circuit with an excitation current command value consistent with the excitation current detection value; a torque current control circuit that controls the torque current direction voltage so that the torque current command value is consistent with the torque current detection value; A V/f conversion circuit that calculates the induced voltage of the AC motor based on the supplied output frequency command; a phase angle calculation circuit that calculates the phase angle obtained by integrating the supplied output frequency command; The current control circuit, the voltage command output by the torque current control circuit and the V/f conversion circuit, the output voltage operation circuit that calculates the magnitude and phase of the output voltage, and the voltage output from the output voltage operation circuit The magnitude and phase are added to the phase angle output from the phase angle calculation circuit to determine the switch of the power converter, and when the AC motor in the free running state is started, the set voltage is applied to the AC motor. The direct current or direct voltage of time, estimate the rotation direction and speed of the AC motor according to the secondary current flowing at this time, set the rotation direction and the frequency corresponding to the speed in the frequency adjustment circuit and start it, by The frequency adjustment circuit makes the output frequency consistent with the speed of the AC motor, wherein the time for applying the DC current or the DC voltage is set to an estimated lower limit value of the AC motor or according to the setting of the time constant of the secondary circuit. The larger one of the values calculated by the fixed value.

A tenth aspect of the present invention is characterized in that, in the sensorless vector control method for an AC motor according to the ninth aspect of the present invention, if the frequency of the secondary current cannot be measured within the time period in which the direct current or direct voltage is applied, the The AC motor is in a stopped state, and the preset minimum frequency or zero frequency is input to the frequency adjustment circuit.

A sensorless vector control device for an AC motor according to an eleventh aspect of the present invention includes: a power converter that outputs arbitrary power to the AC motor; a current detection circuit that detects the current supplied to the AC motor; and converts the current supplied to the AC motor. A coordinate conversion circuit that outputs the detection value of the excitation current and the detection value of the torque current; an excitation current control circuit that controls the direction voltage of the excitation current so that the command value of the excitation current is consistent with the detection value of the excitation current; controls the torque current The direction voltage is a torque current control circuit that makes the torque current command value consistent with the torque current detection value; a V/f conversion circuit that calculates the induced voltage of the AC motor according to the output frequency command provided; the calculation is passed a phase angle calculation circuit for a phase angle obtained by integrating the supplied output frequency command; and based on the voltage command output from the excitation current control circuit, the torque current control circuit, and the V/f conversion circuit, calculate an output voltage calculation circuit for the magnitude and phase of the output voltage, which adds the magnitude and phase of the voltage output from the output voltage calculation circuit to the phase angle output from the phase angle calculation circuit to determine the electric power The control device of the switch of the converter, and the AC motor does not have the speed detector and the voltage detector for the processing, and when starting the AC motor in the free running state, a set time is applied to the AC motor DC current or DC voltage, the rotation direction and speed of the AC motor are estimated from the secondary current flowing at this time, the rotation direction and the frequency corresponding to the speed are set in the frequency adjustment circuit and started, and the frequency adjustment A circuit that makes the output frequency coincide with the speed of the AC motor, characterized in that the time for applying the DC current or DC voltage is set to an estimated lower limit value of the AC motor or a set value based on the time constant of the secondary circuit The larger of the calculated values.

The twelfth aspect of the present invention is characterized in that, in the sensorless vector control device for an AC motor according to the eleventh aspect of the present invention, if the frequency of the secondary current cannot be measured within the time period in which the direct current or the direct voltage is applied, it is determined that The AC motor is in a stopped state, and the preset minimum frequency or zero frequency is input to the frequency adjustment circuit.

The sensorless vector control method of an AC motor according to the thirteenth aspect of the present invention includes a current control unit having a power converter that outputs power to the AC motor, and controls the power based on the deviation signal between the current command signal and the output current detection signal of the power converter. The output current of the converter, the method is used to control an AC motor that does not have a speed detector and a voltage detector, and when the AC motor is in a free running state, the current command signal is forcibly set to zero for current control, The magnitude, phase, and angular velocity of the residual voltage of the AC motor are obtained from the output voltage command signal calculated using the output of the current control unit at this time so that the current of the AC motor is zero, and estimated The rotation direction and speed of the AC motor in a free running state are characterized in that the current command is determined based on the operating frequency of the power converter before free running and the secondary circuit time constant of the AC motor. The signal is set to zero for the waiting time before current control begins.

The fourteenth aspect of the present invention is that, in the sensorless vector control method for an AC motor according to the thirteenth aspect of the present invention, when the operating frequency of the power converter before free running is lower than an arbitrarily set frequency, the The current command signal is set to zero and the waiting time before starting the current control is set to zero.

The fifteenth aspect of the present invention is that, in the sensorless vector control method for an AC motor according to the thirteenth or fourteenth aspect of the present invention, it is difficult to control the current of the AC motor to zero when the induced voltage of the AC motor is large. In the case of , the control to set the current of the AC motor to zero is stopped, and the power converter is switched to short-circuit all three input phases of the AC motor within an arbitrarily set time to apply power to the AC motor. The braking force decelerates the AC motor, controls the current of the AC motor to zero again, and estimates the rotation direction and speed of the AC motor in a free running state.

The sensorless vector control device for an AC motor according to the sixteenth aspect of the present invention includes a current control unit, a power converter that outputs power to the AC motor, and controls the power based on a deviation signal between a current command signal and an output current detection signal of the power converter. The output current of the converter. The AC motor does not have a speed detector and a voltage detector. When the AC motor is in a free-running state, the current command signal is forcibly set to zero for current control, so that the AC The current of the motor is zero, and the magnitude, phase, and angular velocity of the residual voltage of the AC motor are obtained from the output voltage command signal calculated using the output of the current control unit at this time, thereby estimating the value in the free running state. The rotation direction and speed of the AC motor are characterized in that the current command signal is determined to be zero based on the operating frequency of the power converter before free running and the secondary circuit time constant of the AC motor. Waiting time before starting current control.

The seventeenth aspect of the present invention is that, in the sensorless vector control device for an AC motor according to the sixteenth aspect of the present invention, when the operating frequency of the power converter before free running is lower than an arbitrarily set frequency, the The current command signal is set to zero and the waiting time before starting the current control is set to zero.

The eighteenth aspect of the present invention is that, in the sensorless vector control device for an AC motor according to the sixteenth or seventeenth aspect of the present invention, it is difficult to control the current of the AC motor to zero because the induced voltage of the AC motor is large. In the case of , the control to set the current of the AC motor to zero is stopped, and the power converter is switched to short-circuit all three input phases of the AC motor within an arbitrarily set time to apply power to the AC motor. The braking force decelerates the AC motor, controls the current of the AC motor to zero again, and estimates the rotation direction and speed of the AC motor in a free running state.

The sensorless vector control method of an AC motor according to the nineteenth aspect of the present invention includes a current control unit having a power converter that outputs power to the AC motor, and controls the power based on the deviation signal between the current command signal and the output current detection signal of the power converter. The output current of the converter. The AC motor does not have a speed detector and a voltage detector. When the AC motor is in a free-running state, the current command signal is forcibly set to zero for current control, so that the AC The current of the motor is zero, and the magnitude, phase, and angular velocity of the residual voltage of the AC motor are obtained from the output voltage command signal calculated using the output of the current control unit at this time, thereby estimating the value in the free running state. The rotational direction and the speed of the AC motor are characterized in that, when performing the process of making the current of the AC motor zero, the scan time of the current control process is made shorter than that of the normal control.

A twentieth aspect of the present invention is characterized in that, in the sensorless vector control method of an AC motor according to the nineteenth aspect of the present invention, when performing the process of making the current of the AC motor zero, the scan time of the current control process is set to be shorter than Usually the control time is short, and the carrier frequency of the power converter is increased.

The sensorless vector control device for an AC motor according to claim 21 of the present invention includes a current control unit, a power converter that outputs power to the AC motor, and controls the current command signal and the deviation signal of the output current detection signal of the power converter The output current of the power converter. The AC motor does not have a speed detector and a voltage detector. When the AC motor is in a free-running state, the current command signal is forcibly set to zero for current control, so that the The current of the AC motor is zero, and the magnitude, phase, and angular velocity of the residual voltage of the AC motor are obtained from the output voltage command signal calculated using the output of the current control unit at this time, thereby estimating the value in the free running state. The rotation direction and speed of the AC motor are characterized by having means for making the scan time of the current control process shorter than that of the normal control when performing the process of making the current of the AC motor zero.

The twenty-second aspect of the present invention is characterized in that, in the sensorless vector control device for an AC motor according to the twenty-first aspect of the present invention, when performing the process of making the current of the AC motor zero, a process of controlling the current is provided. A unit that increases the carrier frequency of the power converter with a scan time shorter than normal control.

The sensorless vector control method of an AC motor according to claim 23 of the present invention includes a current control unit having a power converter that outputs power to the AC motor, and controls the The output current of the power converter. The AC motor does not have a speed detector and a voltage detector. When the AC motor is in a free-running state, the current command signal is forcibly set to zero for current control, so that the The current of the AC motor is zero, and at the same time, when the output voltage command signal calculated using the output of the current control part at this time is lower than an arbitrarily set voltage level, the current control is stopped, and the set time is applied in an arbitrary direction. Direct current command of arbitrary magnitude, and then apply a current command of arbitrary magnitude in a direction in which the phase is changed by 180° relative to the command direction of the DC voltage, and then perform current control for a set time, and the speed estimation circuit detects the occurrence of the current detection value A frequency component and its phase relationship, the frequency component is estimated as the speed of the AC motor, and its rotation direction is estimated based on the phase relationship, characterized in that, when a DC current command is applied to the AC motor, the speed and rotation of the AC motor are estimated In the direction, the scan time of the current control processing is shorter than that of the normal control.

A twenty-fourth aspect of the present invention is characterized in that, in the sensorless vector control method for an AC motor according to the twenty-third aspect of the present invention, when a DC current command is applied to the AC motor and the speed and rotation direction of the AC motor are estimated , make the scan time of the current control process shorter than the normal control, and increase the carrier frequency of the power converter.

The twenty-fifth aspect of the present invention is that, in the sensorless vector control method of an AC motor according to the twenty-third or twenty-fourth aspect of the present invention, the speed of the AC motor is estimated when a DC current command is applied to the AC motor. In the rotation direction, the scan time of the current control process is shorter than that of the normal control, and a high-sensitivity current detector that can detect a smaller current than the normal control is used.

A sensorless vector control device for an AC motor according to claim 26 of the present invention includes a current control unit, a power converter that outputs power to the AC motor, and controls the current command signal based on the deviation signal between the current command signal and the output current detection signal of the power converter. The output current of the power converter. The AC motor does not have a speed detector and a voltage detector. When the AC motor is in a free-running state, the current command signal is forcibly set to zero for current control, so that the The current of the AC motor is zero, and when the output voltage command signal calculated using the output of the current control section at this time is lower than an arbitrarily set voltage level, the current control is stopped, and the set time is applied in an arbitrary direction. Direct current command of arbitrary size, and then apply current command of arbitrary size in the direction of changing the phase by 180° relative to the command direction of the DC voltage, and then perform current control for a set time. At this time, the current detection is detected by the speed estimation circuit The frequency component and its phase relationship appearing in the value, the frequency is fully estimated as the speed of the AC motor, and the direction of rotation is estimated based on the phase relationship, it is characterized in that, when a DC current command is applied to the AC motor, the AC motor is estimated This unit shortens the scan time of the current control process compared to the normal control for the speed and rotation direction of the motor.

The twenty-seventh aspect of the present invention is characterized in that, in the sensorless vector control device for an AC motor according to the twenty-sixth aspect of the present invention, the speed and the direction of rotation of the AC motor are estimated when a DC current command is applied to the AC motor. A unit that shortens the scan time of the current control process compared to normal control and increases the carrier frequency of the power converter.

The twenty-eighth aspect of the present invention is that, in the sensorless vector control method for an AC motor according to the twenty-sixth or twenty-seventh aspect of the present invention, the speed of the AC motor is estimated when a DC current command is applied to the AC motor. In the rotation direction, the scan time of the current control process is shorter than that of the normal control, and a high-sensitivity current detector that can detect a smaller current than the normal control is used.

Description of drawings

FIG. 1 is a block diagram showing the configuration of a first embodiment of a sensorless vector control device for an AC motor according to the present invention.

FIG. 2 is a graph showing changes in the torque current detection value iqfb of the AC motor when a DC current is applied during forward free running.

3 is a graph showing changes in the torque current detection value iqfb when the AC motor is subjected to a DC current during reverse free running.

FIG. 4 is a graph showing changes in the torque current detection value iqfb when a DC current is applied during low-speed free running of the AC motor.

5 is a graph showing changes in torque current detection value iqfb when a DC current is applied in an example in which the secondary circuit time constant of the AC motor is long.

FIG. 6 is a flowchart showing the configuration of the first embodiment.

7 is a block diagram showing a configuration of a second embodiment of sensorless vector control of an AC motor according to the present invention.

Fig. 8 shows the operating frequency before free running and the waiting time before restarting.

9 is a block diagram showing the configuration of a third embodiment of the sensorless vector control of an AC motor according to the present invention.

10 is a block diagram showing the configuration of a fourth embodiment of the sensorless vector control device for an AC motor according to the present invention.

Explanation of symbols in the figure: 1 power converter; 2 AC motor; 3 current detector; 4 current coordinate conversion circuit; 5 torque current control circuit; 6 excitation current control circuit; 7 phase operation circuit; 8V/f conversion circuit; 9 output voltage calculation circuit; 10 switching pattern generation circuit; 11 frequency adjustment circuit; 12, 13, 14, 17 switches; 15 speed estimation circuit (third embodiment); 15B speed estimation circuit (fourth embodiment); 16 addition device.

Detailed ways

Hereinafter, the present invention will be described with reference to the drawings.

First, a first embodiment of the present invention will be described.

In the first embodiment, when the AC motor is restarted, when the current flowing through the AC motor remains at or above the set current level for a set time, it is determined that the rotation direction or speed is If the guess is wrong, DC current or DC voltage is applied again, and the rotation direction and speed of the AC motor are guessed.

FIG. 1 is a block diagram showing a configuration of a first embodiment of sensorless vector control of an AC motor according to the present invention. The sensorless vector control device of the motor in this embodiment has: a power converter 1; an AC motor 2; a current detector 3; a current coordinate conversion circuit 4; a torque current control circuit 5; an exciting current control circuit 6; a phase calculation circuit 7 ; V/f conversion circuit 8; output voltage calculation circuit 9; switching pattern generation circuit 10; frequency adjustment circuit 11.

The power converter 1 converts the three-phase AC into a DC voltage through power elements, and converts the DC voltage into an AC of any frequency and voltage through PWM control, and supplies it to the AC motor 2 .

The current detector 3 detects the current supplied to the AC motor 2 .

The current coordinate conversion circuit 4 decomposes the current detected by the current detector 3 into a torque current detection value iqfb and an excitation current detection value idfb.

The torque current control circuit 5 calculates the first q-axis voltage command value V'qref such that the supplied torque current command value iqref matches the torque current detection value iqfb.

The exciting current control circuit 6 calculates the d-axis voltage command value dref such that the supplied exciting current command value idref matches the exciting current detected value idfb.

The phase calculation circuit 7 calculates the phase θ by integrating the supplied frequency f1.

The V/f conversion circuit 8 calculates a voltage Eref corresponding to the induced voltage of the AC motor from the supplied frequency f1.

The output voltage operation circuit 9 adds the output of the torque current control circuit 5, that is, the first q-axis voltage command value V'qref, and the output of the V/f conversion circuit 8, that is, the voltage Eref, to calculate the second q The axis voltage command value Vqref outputs an output voltage command value Vlref and its voltage phase θv from the second q-axis voltage command value Vqref and the d-axis voltage command value dref.

The switching pattern generating circuit 10 determines the switching pattern of the power converter 1 based on the power converter output phase θdeg obtained by adding the output voltage command value Vlref and the voltage phase θv to the phase θ.

The frequency adjustment circuit 11 adjusts the frequency output from the power converter 1 when restarting the AC motor 2 in the free-running state, thereby enabling a smooth start.

In order to estimate the rotation direction and speed of the AC motor 2 in the free running state, after providing a DC current command for an arbitrarily set time to the excitation current command value idref, the sign and magnitude of the DC current command are changed to perform current control, The change in the torque current detection value iqfb is estimated.

In the present invention, when starting an AC motor in a free running state, DC current or DC voltage is applied to the AC motor, and the rotation direction and speed of the AC motor are estimated from the secondary current flowing at this time. FIG. 2 shows a situation where the AC motor 2 is free running in the forward direction, and FIG. 3 shows a situation where the AC motor 2 is free running in the reverse direction. In each figure, (a) shows the time of the excitation current detection value idfb of the AC motor 2. (b) shows the temporal change of the torque current detection value iqfb of the AC motor 2 .

In FIG. 2 , at time t1 shown in (a), when the excitation current detection value idfb of a negative rectangular wave flows through the AC motor 2, a waveform is generated as in the case (b) of the AC motor 2 performing forward free running. The torque current detection value iqfb rising in the positive direction.

Conversely, as shown in Figure (3), when the excitation current detection value idfb of the negative rectangular wave flows through the AC motor 2 at the time t1 shown in (a), as in the case of the AC motor 2 performing reverse free running (b ) likewise, the torque current detection value iqfb whose waveform is in the negative direction is generated similarly.

Therefore, by focusing on this point, the direction of rotation can be detected from the time change of the detected torque current detection value iqfb, and by measuring the frequency of the torque current detection value iqfb, the speed of the AC motor can be estimated. .

The rotation direction and speed estimation value of the AC motor 2 thus estimated are set in the frequency adjustment circuit 11 and used. The frequency adjustment circuit 11 adjusts the frequency so that the torque current detection value iqfb is 0, and the speed in the free running state of the AC motor 2 is consistent with the output frequency of the power converter, so that the AC motor 2 can be started smoothly.

In the present invention, when an erroneous detection of the speed estimation value or the rotation direction occurs, it is automatically detected, and the direct current is applied again, and the torque current detection value iqfb of the time change of the AC motor is estimated. Rotation direction and speed. That is, according to the magnitude of the current flowing through the AC motor, it is estimated that the rotation direction and frequency set in the frequency adjustment circuit deviate from the actual rotation direction and speed of the AC motor. The state of the current level lasted for a set time as the main condition. And, when the main condition is satisfied, the restart of the AC motor is stopped, a DC current or a DC voltage is applied to the AC motor again, and the rotation direction and the direction of rotation of the AC motor are re-estimated from the secondary current flowing at this time. speed. When this re-estimation is performed, the estimated value of the speed is a value lowered by the set speed than the previously estimated speed, or the final output value of the frequency adjustment circuit is estimated as an upper limit value. In the frequency adjustment circuit Set the frequency corresponding to the estimated value and start.

Next, the operation of this embodiment for restarting the AC motor in the free running state will be described in detail with reference to FIGS. 1 and 6 .

When the AC motor 2 is in the free running state, the three switches S1 to S3 in FIG. 1 change from the normal running state on the A side to the free running starting state on the B side. Therefore, the torque current DC value iqref=0, the excitation current command is output from the V/f conversion circuit 8 , and the output frequency f1 becomes the output of the frequency adjustment circuit 11 . However, zero frequency is set as an initial value in the frequency adjustment circuit 11 . In this way, an arbitrary DC current (see FIG. 2 or FIG. 3( a )) is supplied to the AC motor 2 for a set time (step S1 ). Based on the torque current detection value iqfb flowing at this time (see FIG. 2 or FIG. 3( b )), the frequency and the direction of rotation are estimated (step S2 ). Based on the estimation result, the frequency and the rotation direction are reset in the frequency adjustment circuit 11 (step S3).

When the frequency adjustment circuit 11 resets the frequency and the direction of rotation, the V/f conversion circuit 8 calculates the excitation current command to make the magnetic flux rise according to the time constant of the secondary circuit, and according to the magnetic flux and the setting With a given frequency f1, the voltage Eref equivalent to the induced voltage of the AC motor is calculated and output.

In the frequency adjustment circuit 11, the following adjustment is performed so that the torque current detection value iqfb is close to 0, that is, if the torque current detection value iqfb is positive, the frequency is reduced, and if the torque current detection value iqfb is negative, the output is increased frequency.

After the magnetic flux reaches the level during normal operation, when the torque current detection value iqfb reaches a set level close to 0 (that is, when the current flowing through the AC motor is no longer in a state greater than or equal to the set level for any time, ( No)) in step S4, it is judged that normal start is possible, and the three switches S1 to S3 are switched to the A side (step S7).

However, when the frequency adjustment circuit 11 adjusts the frequency, if the current flowing through the AC motor remains equal to or greater than an arbitrary set level for an arbitrary time (YES in step S4), according to the present embodiment, it is judged that Obvious abnormal state (step S5). This state indicates that the rotation direction of the AC motor is different from the rotation direction set in the frequency adjustment circuit 11, or that the speed of the AC motor deviates greatly from the frequency setting value set in the frequency adjustment circuit 11. Condition.

When this state is detected, temporarily stop the power converter (step S6), return to step S1 where the DC current is applied again, re-estimate the rotation direction and speed of the AC motor, and re-execute the frequency adjustment circuit. set up.

Here, as the upper limit value of the estimated speed value of the AC motor, a value obtained by decreasing an arbitrary level value from the previously estimated frequency, or a frequency at which the frequency adjustment current is last output is used. Thereby, false detection at the time of reestimation can be suppressed.

In addition, in the above-mentioned embodiments, the electric power conversion device that decomposes the current flowing through the AC motor 2 into the torque current and the exciting current and performs vector control for independent control is described. The present invention can be implemented with exactly the same processing as long as a current control circuit that decomposes the current flowing through the AC motor at the time of free-running start into torque current and excitation current and independently controls each is added to the conversion device.

Next, a modified example of the first embodiment of the present invention will be described.

The modified example of the first embodiment relates to a method of setting an arbitrary time for supplying a DC current command to the excitation current command value idref, by setting an arbitrary DC current application time as the lower limit value or the second limit value of the estimated speed of the AC motor. The larger one of the secondary circuit time constants can reliably estimate the rotation direction and speed of the AC motor.

As a method of measuring the frequency of the torque current detection value, there is a method of measuring the period between the positive peak and the negative peak or the period between zero crossing points.

However, as shown in FIG. 4 , if the period T1 between the positive peak and the negative peak or the period T2 between zero crossing points cannot be measured, the frequency cannot be detected. Therefore, in order to be able to detect the frequency, it is necessary to continuously flow a direct current.

However, even if the power converter is started from zero frequency or the lowest frequency that can be output when the AC motor is running at low speed, it can be started smoothly with little shock. The limit value is an estimated speed value when the AC motor is free running, and it is judged to be stopped when the speed is less than this speed, and the estimated speed value is set in the frequency adjustment circuit as a preset value or zero frequency.

In addition, in an AC motor with a large secondary circuit time constant, the torque current detection value iqfb has the waveform shown in FIG. 5 due to the influence of the residual voltage, and the rotation direction may not be detected correctly. Therefore, in order to eliminate the influence of the residual voltage, only a direct current is applied for a time corresponding to the time constant of the secondary circuit or a time proportional to the time constant of the secondary circuit.

In this way, the residual voltage is eliminated by the applied direct current, and the waveform shown in FIG. 5 becomes an easily detectable waveform as shown in FIG. 2 (or FIG. 3 ), so that the direction of rotation can be accurately estimated.

Therefore, the setting method of an arbitrary time for providing a DC current command is preferably set to the time calculated based on the lower limit value of the preset speed estimation value, the time corresponding to the time constant of the secondary circuit, or the time corresponding to the time constant of the secondary circuit. The longer of the constant proportional times.

The operation when restarting the AC motor in the free-running state has been described in detail in the first embodiment, and is omitted here.

In addition, in the description of the present invention, the electric power conversion device that decomposes the current flowing through the AC motor 2 into the torque current and the exciting current and performs vector control for independent control is described. However, when V/f constant control is performed, The present invention can be implemented with exactly the same processing by adding a current control circuit that decomposes the current flowing through the AC motor during free-running start into a torque current and an exciting current, and controls each independently.

In addition, in the description of the present invention, a method of measuring the period between the positive peak and the negative peak or the period between zero crossing points was described as a method of measuring the frequency, but it can be estimated that The speed of the AC motor.

7 is a block diagram showing the configuration of a second embodiment of the sensorless vector control device for an AC motor according to the present invention. The sensorless vector control device of the motor in this embodiment has: a power converter 1; an AC motor 2; a current detector 3; a current coordinate conversion circuit 4; a torque current control circuit 5; an exciting current control circuit 6; a phase calculation circuit 7 ; V/f conversion circuit 8 ; output voltage calculation circuit 9 ; switch pattern generation circuit 10 ; switches 12 , 13 , 14 ;

Power converter 1 sequentially converts three-phase AC into DC voltage through power components, and converts the DC voltage into AC of any frequency and voltage by controlling the switch of power components in the main circuit according to PWM control mode, and supplies the AC motor 2 . The current detector 3 detects the current supplied to the AC motor 2 . The current coordinate conversion circuit 4 decomposes the current detected by the current detector 3 into a torque current detection value iqfb and an excitation current detection value idfb. The torque current control circuit 5 calculates the first q-axis voltage command value V'qref such that the supplied torque current command value iqref matches the torque current detection value iqfb. The exciting current control circuit 6 calculates the d-axis voltage command value Vdref so that the supplied exciting current command value idref and the aforementioned exciting current detection value idfb match.

The phase calculation circuit 7 calculates the phase θ by integrating the supplied frequency f1. The V/f conversion circuit 8 calculates a voltage Eref corresponding to the induced voltage of the AC motor from the supplied frequency f1.

The output voltage operation circuit 9 adds the output of the torque current control circuit 5, that is, the first q-axis voltage command value V'qref, and the output of the V/f conversion circuit 8, that is, the voltage Eref, to calculate the second The q-axis voltage command value Vqref outputs the output voltage command value Vlref and its voltage phase θV based on the second q-axis voltage command value and the d-axis voltage command value. The switching pattern generation circuit 10 determines the switching pattern of the power converter 1 based on the output voltage command value Vlref and the power converter output phase θdeg obtained by adding the voltage phase θV to the phase θ.

The speed estimation circuit 15 is a circuit for estimating the speed fr of the AC motor 2 in the free running state. The switch 12 is a switch for switching the torque current command value iqref to the zero side, ie, the B side, or the A side, which is an input of the torque current control circuit 5 . The switch 13 is a switch for switching the exciting current command value idref to the zero side, that is, the B side, or the A side, which is an input of the exciting current control circuit 6 . The switch 14 is a switch for switching the frequency f1 to the zero side, that is, the B side, or the A side which becomes the input of the V/f conversion circuit 8 .

Next, the operation when restarting the AC motor in the free running state will be described in detail. When the AC motor 2 is in the free running state, the three switches 12 , 13 , 14 in FIG. 7 change from the normal running state on the A side to the free running starting state on the B side. Accordingly, the torque current command value iqref=0, and the excitation current command value idref=0. In addition, during normal control, since the AC motor is free-running and has no reference phase, the current flowing through the AC motor is controlled to be zero. This is because when the AC motor is in a free-running state, an induced voltage corresponding to the rotation speed is generated, and the induced voltage rotates at the rotation speed of the AC motor 2, so if it is different from the rotation speed of the AC motor 2 When the power converter 1 is started to operate regardless of the magnitude of the induced voltage, a current flows between the AC motor 2 and the power converter 1 . If the current is controlled to be zero by using the torque current control circuit 5 and the excitation current control circuit 6, the magnitude, phase and frequency of the induced voltage of the AC motor 2 and the output voltage of the power converter can be made consistent. This operation of controlling the current flowing through the AC motor to zero is called zero current control.

The outputs of the torque current control circuit 5 and the excitation current control circuit 6 during the zero current control, that is, the first q-axis voltage command value V'qref and the d-axis voltage command value Vqref, have the frequency and the rotation speed of the AC motor 2 Consistent sine wave voltage command value. The output voltage calculation circuit 9 receives the first q-axis voltage command value V'qref and the d-axis voltage command value as inputs, and outputs the output voltage command value Vlref and its voltage phase θV. The output voltage command value Vlref represents the magnitude of the induced voltage of the AC motor, and the voltage phase θV represents the phase of the induced voltage. Therefore, the speed estimation circuit 15 measures the frequency of the induced voltage by measuring the temporal change of the phase of the induced voltage at regular intervals. The frequency of the induced voltage matches the rotation speed of the AC motor 2 as described above. Therefore, the rotation speed of the AC motor 2 in the free running state can be estimated. When the AC motor reverses, the rate of change of the phase is negative, so it can be estimated whether the AC motor in the free running state is rotating forward or reverse. In this way, by observing the induced voltage of the AC motor using zero current control, it is possible to estimate the rotation speed including the rotation direction of the AC motor.

Next, a method of setting the estimated rotation direction and speed in the power converter when the zero-current control is stopped and switched to the normal control will be described. When switching from the zero-current control state to normal operation, if the power converter 1 is started only by matching the frequency, an excessive current flows through the AC motor, and smooth start may not be possible. In order to prevent this, the magnitude and phase of the induced voltage in zero current control must be continuous even at the moment of transition to normal control. Therefore, it is necessary to set initial values for the output voltage command value Vlref of the power converter, the power converter output phase θdeg, and the output frequency f1. Specifically, under normal operating conditions, the power converter output phase θdeg is controlled to take the magnetic flux phase of the AC motor 2 as a reference, but in zero current control, the output phase θdeg is induced by the AC motor 2 Phases with consistent voltages. Therefore, in zero-current control, the phase advances by 90° in forward rotation and lags by 90° in reverse rotation relative to the phase of normal control. Therefore, the initial value of the power converter output phase θdeg is set to be the rotation speed of the AC motor 2 output from the speed estimation circuit 15 after correcting the phase by 90° from the last phase of the zero current control corresponding to the rotation direction. The estimated value fr is converted to phase and the corrected value is added. In this way, the continuity of the phase is ensured.

Furthermore, if the output voltage command value Vlref output during the zero current control is set as the induced voltage, the continuity of the output voltage is maintained. In this way, it is possible to smoothly transfer from zero current control to normal control.

When the AC motor is an induction motor, the induced voltage attenuates according to the time constant of the secondary circuit, so at the point in time when the induced voltage matches the normal V/f level according to the time constant of the secondary circuit, it is judged that it can be started normally. For an AC motor in a free running state, the three switches 12, 13, 14 are switched to the A side.

When the AC motor is a permanent magnet synchronous motor, since the induced voltage does not attenuate, it is judged that the free running state can be started normally at the time point when the process for ensuring the continuity of the phase and the continuity of the output voltage is performed. AC motor, 3 switches 12, 13, 14 are switched to A side.

Next, the method of determining the waiting time before restarting the power converter according to the present invention will be described.

In order to estimate the speed of the AC motor in the free running state, the outputs of the torque current control circuit 5 and the excitation current control circuit 6 during zero current control, that is, the first q-axis voltage command value V'qref, the d-axis voltage command value The value Vqref must correspond to the induced voltage of the AC motor in question. Here, there is no problem if the torque current control circuit 5 and the exciting current control circuit 6 function sufficiently to control the current flowing through the AC motor to zero.

However, when the gains of the torque current control circuit 5 and the excitation current control circuit 6 are low or the AC motor rotates at high speed, a large induced voltage will flow immediately after starting the power converter. With high current, the power converter trips and smooth starting cannot be performed. In order to prevent this situation, if the responsiveness of the torque current control circuit 5 and the excitation current control circuit 6 is known in advance, so that the voltage level generated by the AC motor in the free running state is lower than any value, zero current control can be realized , the velocity can be inferred. That is, it is only necessary to make the induced voltage of the AC motor smaller than an arbitrarily set voltage level.

As one of the methods, it can be realized by controlling the time until the power converter is restarted. Since the induced voltage of the AC motor is determined by the operating frequency before the free-running state, no waiting time is required when operating at a frequency at which the induced voltage is lower than the arbitrarily set voltage level. On the other hand, when operating at this frequency or higher, waiting time is required, but the calculation can be performed based on the operating frequency before the free running state and the secondary circuit time constant of the AC motor. The longest necessary waiting time is calculated by using the secondary circuit time constant of the AC motor, and when this time is reached, as shown in FIG. Can.

Next, a countermeasure against the case where the induced voltage of the AC motor becomes large and it is difficult to control the current of the AC motor to zero, which is one aspect of the present invention, will be described. When the AC motor is an induction motor or a permanent magnet synchronous motor having a long secondary circuit time constant, as described above, the induced voltage may not be lower than an arbitrarily set voltage level even after the waiting time has elapsed. In this case, the zero-current control is stopped midway, and the power converter is switched to short-circuit all three phases of the AC motor, and the three-phase short-circuit is continued for an arbitrarily set time. In this way, a braking force is generated in the AC motor, and the AC motor is decelerated.

Accordingly, the induced voltage of the AC motor is reduced. After an arbitrary time elapses, the zero current control is restarted, and after the induced voltage becomes lower than an arbitrarily set voltage level, the estimated speed can be estimated by the zero current control. However, when the induced voltage is not lower than an arbitrarily set voltage level, the switching operation of the three-phase circuit is performed again for an arbitrarily long time. In this way, this process is repeated until the induced voltage of the AC motor is lower than an arbitrarily set voltage level, thereby preventing excessive current from flowing, preventing the power converter from tripping, and restarting the AC motor smoothly. .

In addition, in the above-mentioned embodiments, the electric power conversion device that decomposes the current flowing through the AC motor 2 into the torque current and the exciting current and performs vector control for independent control is described. The present invention can be implemented with exactly the same processing as long as a current control circuit that decomposes the current flowing through the AC motor at the time of free-running start into torque current and excitation current and independently controls each is added to the conversion device.

9 is a block diagram showing the configuration of a third embodiment of the sensorless vector control device for an AC motor according to the present invention.

The sensorless vector control device of the motor in this embodiment has: a power converter 1; an AC motor 2; a current detector 3; a current coordinate conversion circuit 4; a torque current control circuit 5; an exciting current control circuit 6; a phase calculation circuit 7 ; V/f conversion circuit 8 ; output voltage calculation circuit 9 ; switching pattern generation circuit 10 ; speed estimation circuit 15 ; adder 16 . The power converter 1 converts the DC voltage obtained by the three-phase AC conversion by the power element into an arbitrary frequency and AC voltage by means of PWM control, and supplies it to the AC motor 2 .

The current detector 3 detects the current supplied to the AC motor 2 and inputs the current detection signal to the current coordinate conversion circuit 4 .

The current coordinate conversion circuit 4 decomposes the current detected by the current detector 3 into a torque current detection value iqfb and an exciting current detection value idfb, and inputs the separated torque current detection value iqfb to the torque current control circuit 5, and sends The excitation current control circuit 6 inputs the separated excitation current detection value idfb. The torque current control circuit 5 calculates the first q-axis voltage command value V'qref so that the supplied torque current command value iqref matches the torque current detection value iqfb.

The exciting current control circuit 6 calculates the d-axis voltage command value Vdref such that the supplied exciting current command value idref matches the exciting current detected value idfb.

The phase calculation circuit 7 calculates the phase θ by integrating the supplied frequency f1 , and inputs the phase θ to the current coordinate conversion circuit 4 and the adder 16 .

The V/f conversion circuit 8 calculates a voltage Eref corresponding to the induced voltage of the AC motor based on the input frequency f1. This voltage Eref is preset so that Eref/f1=constant value.

The output voltage operation circuit 9 adds the output of the torque current control circuit 5, that is, the first q-axis voltage command value V'qref, and the output of the V/f conversion circuit 8, that is, the voltage Eref, to calculate the second The q-axis voltage command value Vqref outputs an output voltage command value Vlref and its voltage phase θV from the second q-axis voltage command value Vqref and the d-axis voltage command value dref.

Vlref＝[(Vdref)2+(Vqref)2]1/2 ......(1)

θV＝tan-1(Vqref/Vdref) ……(2)

The switching pattern generation circuit 10 determines the switching pattern of the power converter 1 based on the power converter output phase θdeg obtained by adding the output voltage command value Vlref and the voltage phase θV to the phase θ.

The speed estimation circuit 15 is a circuit for estimating the speed fr and the rotation direction of the AC motor 2 in the free running state based on the change of the voltage phase θV per unit time.

Next, the operation when restarting the AC motor in the free running state will be described in detail. When the AC motor 2 is in the free running state, the three switches 12 , 13 , 14 in FIG. 9 change from the normal running state on the A side to the free running starting state on the B side. Accordingly, the torque current command value iqref=0, and the exciting current command value idref=0. In addition, during normal control, since the AC motor is free-running and has no reference phase, the current flowing through the AC motor is controlled to be zero. This is because when the AC motor is in a free-running state, an induced voltage corresponding to the rotation speed is generated, and the induced voltage rotates at the rotation speed of the AC motor 2, so if it is different from the rotation speed of the AC motor 2 When the power converter 1 is started to operate regardless of the magnitude of the induced voltage, a current flows between the AC motor 2 and the power converter 1 . If the current is controlled to be zero by using the torque current control circuit 5 and the excitation current control circuit 6, the magnitude, phase and frequency of the induced voltage of the AC motor 2 and the output voltage of the power converter can be made unanimous. This operation of controlling the current flowing through the AC motor to zero is called zero current control.

The outputs of the torque current control circuit 5 and the excitation current control circuit 6 during zero current control, that is, the first q-axis voltage command value V'qref and the d-axis voltage command value Vqref, are set to match the rotation speed of the AC motor 2. The frequency of the sine wave voltage command value. The output voltage calculation circuit 9 receives the first q-axis voltage command value V'qref and the d-axis voltage command value Vdref as input, and outputs the output voltage command value Vlref and its voltage phase θV. The output voltage command value Vlref represents the magnitude of the induced voltage of the AC motor, and the voltage phase θV represents the phase of the induced voltage. Therefore, the speed estimation circuit 15 measures the frequency of the induced voltage by measuring the temporal change of the phase of the induced voltage at regular intervals. The frequency of the induced voltage matches the rotation speed of the AC motor 2 as described above. Therefore, the rotation speed of the AC motor 2 in the free running state can be estimated. When the AC motor reverses, the rate of change of phase is negative, so it can be estimated whether the AC motor in the free running state is rotating forward or reverse. In this way, by observing the induced voltage of the AC motor using zero current control, the rotation speed including the rotation direction of the AC motor can be estimated.

Next, a method of setting the estimated rotation direction and speed in the power converter when the zero-current control is stopped and switched to the normal control will be described.

When switching from the zero-current control state to normal operation, if the power converter 1 is started only by matching the frequency, an excessive current will flow to the AC motor, and smooth start may not be possible. In order to prevent this, the magnitude and phase of the induced voltage in zero current control must be continuous even at the moment of transition to normal control. Therefore, it is necessary to set initial values for the output voltage command value Vlref of the power converter, the power converter output phase θdeg, and the output frequency f1. Specifically, under normal operating conditions, the power converter output phase θdeg is controlled to be based on the magnetic flux phase of the AC motor 2, but in zero-current control, the output phase θdeg is the same as the induced voltage of the AC motor 2 consistent phase. Therefore, in zero-current control, the phase advances by 90° in forward rotation and lags by 90° in reverse rotation relative to the phase of normal control. Therefore, the initial value of the power converter output phase θdeg is set to be the rotational speed of the AC motor 2 output from the speed estimation circuit 15 after correcting the phase by 90° from the last phase of the zero current control according to the rotational direction. The estimated value fr is converted to phase and the corrected value is added. In this way, the continuity of the phase can be ensured.

Furthermore, if the output voltage command value Vlref output during the zero current control is set as the induced voltage, the continuity of the output voltage is maintained. In this way, it is possible to smoothly transfer from zero current control to normal control.

At the point in time when the induced voltage of the AC motor increases slightly with the time constant of the secondary circuit and is consistent with the normal V/f level, it is judged that the AC motor in the free running state can be started normally, and the three switches Switch to side A.

Next, a method of improving the current responsiveness in zero current control according to the present invention will be described. In order to estimate the speed of the AC motor in the free running state, the outputs of the torque current control circuit 5 and the excitation current control circuit 6 during zero current control, that is, the first q-axis voltage command value V'qref, the d-axis voltage command value The value Vqref must correspond to the induced voltage of the AC motor.

Here, there is no problem if the torque current control circuit 5 and the exciting current control circuit 6 function sufficiently to control the current flowing through the AC motor to zero. However, when the gains of the torque current control circuit 5 and the excitation current control circuit 6 are low or the AC motor rotates at a high speed, since a large induced voltage is generated, it flows immediately after starting the power converter. Excessive current trips the power converter and prevents smooth starting. In order to prevent this, it is necessary to improve the responsiveness of the torque current control circuit 5 and the excitation current control circuit 6 . If the scan time for processing current control is shortened, the hysteresis disappears correspondingly, and the current can be controlled according to the command. Therefore, if other calculations are omitted during zero-current control, the scan time for current control can be shortened for normal control, so that the responsiveness of current control can be improved. Also, if the current control scan time is shortened during zero current control, the effect of shortening the current control scan time is halved if the generation of the switching pattern of the power converter lags. Therefore, in order to enable the power converter to operate quickly even when performing zero-current control, the responsiveness of current control can be improved by increasing the carrier frequency used as a reference.

In this way, during normal control, by shortening the scan time of current control in zero current control, or increasing the carrier frequency of the power converter, the responsiveness of current control can be improved, preventing excessive current from flowing in zero current control, and preventing the The power converter is tripped, and the AC motor is restarted smoothly.

Next, the configuration of a fourth embodiment of the sensorless vector control device for an AC motor according to the present invention will be described with reference to FIG. 10 .

The sensorless vector control device of the motor in this embodiment has: a power converter 1; an AC motor 2; a current detector 3; a current coordinate conversion circuit 4; a torque current control circuit 5; an exciting current control circuit 6; a phase calculation circuit 7 ; V/f conversion circuit 8; output voltage calculation circuit 9; switching pattern generation circuit 10; speed estimation circuit 15B. Since everything is the same except for the speed estimation circuit 15B, only the speed estimation circuit 15B will be described.

The speed estimation circuit 15B is a circuit for estimating the speed and rotation direction of the AC motor 2 in the free running state based on the torque current detection value iqfb and the excitation current detection value idfb when the DC current is applied.

Next, the operation at the time of restarting the AC motor in the free running state will be described in detail. In the third embodiment, when the output voltage command value Vlref output from the output voltage calculation circuit 9 is lower than a set arbitrary level during zero current control, the AC motor in the free running state almost stops or The time constant of the secondary circuit is short, so it cannot be judged whether the residual voltage disappears. Therefore, in this state, the operation of the third embodiment is stopped, and the operation of the fourth embodiment is switched.

The 3 switches (12, 14, 17) in Fig. 10 change from the normal running state on the A side to the free running starting state on the B side. Accordingly, the torque current command value iqref=0. In addition, during normal control, since the AC motor is free-running and has no reference phase, the current flowing through the AC motor is controlled to be zero. Also, since the speed and rotation direction of the AC motor are estimated using the torque current detection value iqfb when the AC motor is in a free-running state, the second q-axis voltage command value Vqref is set to zero.

In order to excite the AC motor, the excitation current command value idref is provided with a certain set value, and the excitation current control circuit 6 controls only the set time so that the excitation current detection value idfb matches the excitation current command value idref. Then, the sign and magnitude of the exciting current command value idref are changed, and the control of the set time is performed.

At this time, magnetic flux is generated by applying a DC current to the AC motor in a free running state. At this time, the secondary current excessively flowing through the rotor of the AC motor is detected using the torque current detection value iqfb. Then, the speed and rotation direction of the AC motor are estimated by detecting the frequency of the torque current detection value iqfb and the phase information when the DC current is applied.

When the AC motor 2 is rotating in the forward direction, the detected torque current value iqfb changes as shown in FIG. 2 . When the sign of the excitation current detection value idfb is negative, the torque current detection value iqfb becomes a sine wave whose phase starts from 0°, and when the sign of the excitation current detection value idfb is positive, the torque current detection value iqfb becomes a phase A sine wave starting at 180°. The frequency of the sine wave of the detected torque current value iqfb matches the speed of the AC motor 2 in free running, so the speed of the AC motor 2 can be detected by measuring the frequency of the detected torque current value iqfb. And, when the AC motor reverses, it changes as shown in Figure 3, when the sign of the excitation current detection value idfb is negative, the torque current detection value iqfb becomes a sine wave whose phase starts from 180°, and the excitation current When the sign of the detection value idfb is positive, the torque current detection value iqfb becomes a sine wave whose phase starts from 0°.

Thus, by detecting the phase relationship between the excitation current detection value idfb and the torque current detection value iqfb and the frequency of the torque current detection value iqfb when a DC current is applied to the AC motor, the speed and the direction of rotation can be estimated.

Next, a method of setting an estimated rotation direction and speed in the power converter when the DC current application state is switched to normal control after an arbitrary time elapses will be described. In this case, unlike the third embodiment, since there is almost no residual induced voltage in the AC motor, it is only necessary to regenerate the magnetic flux, and it is only necessary to start the power converter 1 by matching the rotation direction and frequency. At the point in time when the induced voltage of the AC motor increases slightly with the time constant of the secondary circuit and is consistent with the normal V/f level, it is judged that the AC motor in the free running state can be started normally, and the three switches Switch to side A.

Next, a method of improving the detection accuracy when estimating the speed by detecting the frequency of the torque current detection value iqfb during the application of the DC current according to the present invention will be described.

When the AC motor is freely running at high speed, the frequency of the torque current detection value iqfb in FIGS. 2 and 3 increases. As one method of measuring the frequency of the torque current detection value iqfb, there is a method of measuring the period between the positive peak value and the negative peak value or the period between zero crossing points. When measuring the period between the positive peak value and the negative peak value or the period between zero crossing points, if the sweep of the current control is slow, the measurement accuracy of the period deteriorates, so the detection accuracy of the frequency also deteriorates. In addition, during free running at high speed, the frequency difference of the AC motor with respect to the direct current becomes large, and the impedance becomes large due to the frequency difference, so that the current flowing through the rotor side becomes small. Therefore, the torque current detection value iqfb becomes small, and it is difficult to measure the period between the positive peak and the negative peak of the torque current detection value iqfb or the period between zero crossing points.

Therefore, if other calculations are omitted during the application of DC current, the scan time for current control can be shortened for normal control, so the resolution of the period between the positive side peak value and the negative side peak value or the period between zero crossing points can be improved, and the Improve frequency detection accuracy. In addition, the responsiveness of current control can be improved by shortening the scan time of current control or increasing the carrier frequency of the power converter during application of DC current, so that the excitation current detection value idfb can be controlled into a rectangular wave shape. The AC motor All of the secondary currents appear in the torque current detection value iqfb. Moreover, the higher the speed of the AC motor in the free running state, the smaller the torque current detection value iqfb, which is difficult to detect by the usual current detection method, so when applying a DC current, as long as the detection sensitivity of the current detection circuit is increased Several times, so that it can detect small currents, even in high-speed free running, it is also possible to measure the period between the positive side peak value and the negative side peak value or the period between zero crossing points.

In this way, during normal control, the responsiveness of current control can be improved by shortening the scan time of current control in the process of applying DC current, or increasing the carrier frequency of the power converter, so that the positive value of the measured torque current detection value iqfb can be improved. The measurement resolution of the period between the side peak value and the negative side peak value or the period between the zero crossing points can accurately measure the speed of the AC motor in free running. During normal control, by improving the detection sensitivity of the current detection circuit during the application of DC current , the speed can be detected even during free running at high speed, and the AC motor can be restarted smoothly.

In addition, in the above-mentioned embodiments, the electric power conversion device that decomposes the current flowing through the AC motor 2 into the torque current and the exciting current and performs vector control for independent control is described. The present invention can be implemented with exactly the same processing as long as a current control circuit that decomposes the current flowing through the AC motor at the time of free-running start into torque current and excitation current and independently controls each is added to the conversion device.

Above, the present invention has been described in detail with reference to specific embodiments, but it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

This application is based on the Japanese patent application (Japanese patent application No. 2002-198712) filed on July 08, 2002, the Japanese patent application (Japanese patent application No. 2002-315177) filed on October 30, 2002, and the Japanese patent application filed on April 25, 2003. Based on the patent application (Japanese Patent Application No. 2003-121733), the content thereof is described in this application as a reference.

As described above, according to the first embodiment of the present invention, when the current flowing through the AC motor remains at or above the set current level for a set period of time when the AC motor is restarted, it is determined that the rotation is not correct. If the estimation of the direction or speed is wrong, the rotation direction and speed of the AC motor can be estimated by reapplying the DC current or DC voltage, so the AC motor in the free running state can be restarted smoothly.

Furthermore, according to the modified example of the first embodiment of the present invention, by setting the time for applying an arbitrary DC current to the lower limit value of the estimated speed of the AC motor or the time constant of the secondary circuit, whichever is larger, since The rotation direction and speed of the AC motor can be accurately estimated from the optimum DC current application time, so that the AC motor in the free running state can also be restarted smoothly.

According to a second embodiment of the present invention, it is a sensorless vector control method for an AC motor, including a current control unit having a power converter that outputs power to the AC motor, and detecting The deviation signal of the signal controls the output current of the power converter. The AC motor does not have a speed detector and a voltage detector. When the AC motor is in a free running state, the current command signal is forcibly set to zero for current control so that the current of the AC motor becomes zero, and obtain the magnitude, phase, and angular velocity of the residual voltage of the AC motor based on the output voltage command signal calculated using the output of the current control unit at this time, thereby Estimating the rotation direction and speed of the AC motor in a free-running state, and determining the current until zero is used based on the operating frequency of the power converter before free-running and the secondary circuit time constant of the AC motor. The waiting time for the command signal to start current control can provide reliable and smooth continuous operation even when the response of the current controller part is poor, or the AC motor is not an induction motor but a permanent magnet synchronous motor. A method and device for controlling an AC motor.

According to the third embodiment of the present invention, when the current command signal is forcibly set to zero and the current control is performed so that the current of the AC motor is zero, the responsiveness of the current controller is improved so that the The power converter does not become in an overcurrent state, and can continue to operate smoothly.

According to the fourth embodiment of the present invention, when the DC current command is given to the AC motor and the speed and rotation direction of the AC motor are estimated, the frequency detection accuracy during high-speed free running of the AC motor is improved. It has the effect of being able to run smoothly and continuously even when the AC motor is free running at high speed.

Claims (16)

1. the sensor-less vector control method of an alternating current motor, it comprises current control division, has electric power converter to the alternating current motor output power, deviation signal according to the output current detection signal of current command signal and electric power converter, the output current of control electric power converter, this method is used to control the alternating current motor that does not possess speed detector and voltage detector, when described alternating current motor is in free operating condition, forcibly current command signal is made as zero and carries out Current Control, so that the electric current of described alternating current motor is zero, the output voltage instruction signal that calculates according to the output of the described current control division that uses this moment, obtain the size of the residual voltage of described alternating current motor, phase place and angular speed, infer the direction of rotation and the speed of the described alternating current motor under the free operating condition with this, it is characterized in that

According to the operating frequency of the described electric power converter before freely turning round and the secondary circuit time constant of described alternating current motor, decision is made as zero with described current command signal and begins to carry out the Current Control stand-by period before.

2. the sensor-less vector control method of alternating current motor according to claim 1, it is characterized in that, when the operating frequency of the described electric power converter before freely turning round is lower than the frequency of any setting, will be made as for zero stand-by period that begins to carry out before the Current Control to described current command signal and be set at zero.

3. the sensor-less vector control method of alternating current motor according to claim 1 and 2, it is characterized in that, induced voltage at described alternating current motor is big, being difficult to the Current Control of described alternating current motor is under zero the situation, stop the electric current of described alternating current motor is made as zero control, by in the time of setting arbitrarily, switching to the equal short circuit of input three-phase that makes described alternating current motor by electric power converter, described alternating current motor is applied braking force, after described alternating current motor is slowed down, be the Current Control of described alternating current motor zero once more, infer the direction of rotation and the speed of the described alternating current motor under the free operating condition.

4. the no sensor vector control device of an alternating current motor, it comprises current control division, it has the electric power converter to the alternating current motor output power, deviation signal according to the output current detection signal of current command signal and electric power converter, the output current of control electric power converter, this alternating current motor does not have speed detector and voltage detector, when described alternating current motor is in free operating condition, forcibly described current command signal is made as zero and carries out Current Control, so that the electric current of described alternating current motor is zero, the output voltage instruction signal that calculates according to the output of the described current control division that uses this moment, obtain size and the phase place and the angular speed of the residual voltage of described alternating current motor, infer direction of rotation and the speed that comes from by the described alternating current motor under the operating condition with this, it is characterized in that

According to the operating frequency of the described electric power converter before freely turning round and the secondary circuit time constant of described alternating current motor, decision is made as zero with described current command signal and begins to carry out the Current Control stand-by period before.

5. the no sensor vector control device of alternating current motor according to claim 4, it is characterized in that, when the operating frequency of the described electric power converter before freely turning round is lower than the frequency of any setting, will be made as for zero stand-by period that begins to carry out before the Current Control to described current command signal and be set at zero.

6. according to the no sensor vector control device of claim 4 or 5 described alternating current motors, it is characterized in that, induced voltage at described alternating current motor is big, being difficult to the Current Control of described alternating current motor is under zero the situation, stop the electric current of described alternating current motor is made as zero control, by in the time of setting arbitrarily, switching to the equal short circuit of input three-phase that makes described alternating current motor by electric power converter, described alternating current motor is applied braking force, after described alternating current motor is slowed down, be the Current Control of described alternating current motor zero once more, infer the direction of rotation and the speed of the described alternating current motor under the free operating condition.

7. the sensor-less vector control method of an alternating current motor, it comprises current control division, has electric power converter to the alternating current motor output power, deviation signal according to the output current detection signal of current command signal and electric power converter, the output current of control electric power converter, this alternating current motor does not have speed detector and voltage detector, when described alternating current motor is in free operating condition, forcibly described current command signal is made as zero and carries out Current Control, so that the electric current of described alternating current motor is zero, the output voltage instruction signal that calculates according to the output of the described current control division that uses this moment, obtain size and the phase place and the angular speed of the residual voltage of described alternating current motor, infer direction of rotation and the speed that comes from by the described alternating current motor under the operating condition with this, it is characterized in that

When the electric current that makes described alternating current motor is zero processing, the sweep time of processing that makes Current Control the weak point during than control usually.

8. the sensor-less vector control method of alternating current motor according to claim 7, it is characterized in that, when the electric current that makes described alternating current motor was zero processing, the sweep time of processing that makes Current Control, the weak point during than control usually and improved the carrier frequency of electric power converter.

9. the no sensor vector control device of an alternating current motor, it comprises current control division, has electric power converter to the alternating current motor output power, deviation signal according to the output current detection signal of current command signal and electric power converter, the output current of control electric power converter, this alternating current motor does not have speed detector and voltage detector, when described alternating current motor is in free operating condition, forcibly described current command signal is made as zero and carries out Current Control, so that the electric current of described alternating current motor is zero, output voltage instruction signal according to the output computing of using described current control division at this moment, obtain size and the phase place and the angular speed of the residual voltage of described alternating current motor, infer direction of rotation and the speed that comes from by the described alternating current motor under the operating condition with this, it is characterized in that

Described no sensor vector control device has when the electric current that makes described alternating current motor is zero processing, makes the unit that compares the weak point when controlling usually sweep time of the processing of Current Control.

10. the no sensor vector control device of alternating current motor according to claim 9, it is characterized in that, described no sensor vector control device has when the electric current that makes described alternating current motor is zero processing, the sweep time of processing that makes Current Control, the weak point during than common control and improved the unit of the carrier frequency of electric power converter.

11. the sensor-less vector control method of an alternating current motor, it comprises current control division, has electric power converter to the alternating current motor output power, deviation signal according to the output current detection signal of current command signal and electric power converter, the output current of control electric power converter, this alternating current motor does not have speed detector and voltage detector, when described alternating current motor is in free operating condition, forcibly described current command signal is made as zero and carries out Current Control, so that the electric current of described alternating current motor is zero, when the output voltage instruction signal that calculates in the output of using described current control division at this moment is lower than the voltage level of any setting simultaneously, stop Current Control, apply the direct current instruction of any size of the time of setting to any direction, the direction that changes 180 ° of phase places to the command direction of described relatively direct voltage applies the current-order of any size then, the Current Control of the time of setting again, speed is inferred frequency content and the phase relation thereof that occurs in the electric circuit inspection current detection value, this frequency content is speculated as the speed of alternating current motor, infer its direction of rotation according to phase relation, it is characterized in that

Applying direct current instruction to described alternating current motor, when inferring the speed of described alternating current motor and direction of rotation, the sweep time of processing that makes Current Control the weak point during than control usually.

12. the sensor-less vector control method of alternating current motor according to claim 11, it is characterized in that, applying the direct current instruction to described alternating current motor, when inferring the speed of described alternating current motor and direction of rotation, the sweep time of processing that makes Current Control, the weak point during than common control and improved the carrier frequency of electric power converter.

13. sensor-less vector control method according to claim 11 or 12 described alternating current motors, it is characterized in that, applying the direct current instruction to described alternating current motor, when inferring the speed of described alternating current motor and direction of rotation, the sweep time of processing that makes Current Control, the weak point during than common control and used the highly sensitive current detector that can detect the less electric current when being different from normal control.

14. the no sensor vector control device of an alternating current motor, it comprises current control division, has electric power converter to the alternating current motor output power, deviation signal according to the output current detection signal of current command signal and electric power converter, the output current of control electric power converter, this alternating current motor does not have speed detector and voltage detector, when described alternating current motor is in free operating condition, forcibly described current command signal is made as zero and carries out Current Control, so that the electric current of described alternating current motor is zero, and when the output voltage instruction signal that the output of using described current control division at this moment calculates is lower than the voltage level of any setting, stop Current Control, apply the direct current instruction of any size of the time of setting to any direction, the direction that changes 180 ° of phase places to the command direction of described relatively direct voltage applies the current-order of any size then, the Current Control of the time of setting again, at this moment, infer frequency content and the phase relation thereof that occurs in the electric circuit inspection current detection value by speed, this frequency fully is speculated as the speed of alternating current motor, infer its direction of rotation according to phase relation, it is characterized in that

Have and applying direct current instruction to described alternating current motor, when inferring the speed of described alternating current motor and direction of rotation, the sweep time of processing that makes Current Control the weak point during than control usually the unit.

15. the no sensor vector control device of alternating current motor according to claim 14, it is characterized in that, described no sensor vector control device has and is applying direct current instruction to described alternating current motor, when inferring the speed of described alternating current motor and direction of rotation, the sweep time of processing that makes Current Control, the weak point during than common control and improved the unit of the carrier frequency of electric power converter.

16. no sensor vector control device according to claim 14 or 15 described alternating current motors, it is characterized in that, applying the direct current instruction to described alternating current motor, when inferring the speed of described alternating current motor and direction of rotation, the sweep time of processing that makes Current Control, the weak point during than common control and used the highly sensitive current detector that can detect the less electric current when being different from normal control.

Images