JP2018019460A - Inverter control device and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relax vehicle impact caused by a recognition error of an estimated speed that easily occurs in an inverter low frequency domain.SOLUTION: An inverter control device 10 comprises: an estimated speed calculation part 11 for estimating a rotor frequency that is a rotation frequency of a rotor of an induction motor 50 through arithmetic operation; an inverter frequency command generation part 12 for generating an inverter frequency command instructing a frequency of a voltage that an inverter 20 outputs, based on the rotor frequency; a frequency limit part 13 for generating a limit frequency command limiting the inverter frequency command so as not to be smaller than a lower limit threshold; and a torque control part 14 for outputting a voltage command instructing the voltage that the inverter 20 outputs, to the inverter 20 based on the limit frequency command.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inverter control device and a program for controlling an inverter mounted on an electric vehicle (railway vehicle).

  A squirrel-cage three-phase induction motor is generally adopted as a main motor constituting an inverter main circuit system of an electric vehicle (railway vehicle). The inverter control device can control the applied voltage and the rotational speed of the induction motor according to the command to be output by detecting the rotational speed of the induction motor by a speed sensor (PG sensor) arranged in the induction motor. However, the speed sensor is composed of electronic components and requires maintenance and inspection. In addition, since there are many cases where it becomes impossible to control the induction motor when the speed sensor breaks down, highly reliable parts are adopted for the speed sensor, which increases the cost.

  Therefore, an inverter control device that employs speed sensorless control that can control an induction motor without using a speed sensor has become widespread (see, for example, Patent Document 1). Speed sensorless control not only improves the performance of an electric vehicle by high-precision torque control, but also has the advantages of cost reduction due to the absence of a speed sensor and increased structural freedom of the induction motor. For this reason, speed sensorless control is currently used in many railway vehicles.

JP-A-11-69895

  In speed sensorless control, since there is no speed sensor input from the induction motor, the inverter control device must control the inverter while estimating the rotation speed of the induction motor. The secondary magnetic flux and torque of the induction motor are obtained by the primary voltage and current applied to the stator of the induction motor and the secondary current obtained by the slip generated by the rotation of the rotor by the primary magnetic flux from the stator. . At this time, the number of rotations of the rotor is estimated from a value obtained by coordinate conversion from magnetic flux calculation and torque calculation. However, if a detection error occurs in the voltage or current detected in this series of operations, a large calculation error is caused, and the accuracy of magnetic flux or torque is deteriorated, so that the induction motor cannot be normally controlled.

  In the speed sensorless control, the difference between the inverter frequency for controlling the stator and the rotor frequency for controlling the rotor, that is, the slip is recognized to recognize the excitation current and the torque current as the secondary magnetic flux component, and the d axis The rotational speed of the rotor is estimated as current (excitation current) and q-axis current (torque current), and the induction motor is controlled as the output voltage vector of the inverter.

  However, as described above, when a detection error occurs in the induced voltage or current detected by the rotation of the rotor, a calculation error is caused, and the estimated speed of the vehicle calculated by the secondary magnetic flux component obtained by the slip is normally set. It becomes difficult to recognize. In particular, in a situation where the vehicle that is in the low frequency region of the inverter is started from a stopped state, vehicle impulses may occur due to erroneous recognition of the estimated speed.

  As an improvement measure, in order to accurately capture the secondary magnetic flux component obtained by the slippage of the induction motor, it is conceivable to increase the excitation current input to the induction motor and increase the induced voltage of the induction motor. However, if the excitation current is increased for the safety signal equipment laid on the railroad track, the noise component is amplified and there is a concern about the influence on the induction failure, and the error improvement of the estimated speed calculation of the vehicle may be stopped. is there.

  In addition, it is considered that the recognition error of the estimated speed is caused by the detection error of the voltage and current of the induction motor and the change of the equivalent circuit constant due to the temperature change of the induction motor. In addition, dead time is required to control the induction motor, and a voltage error occurs during this period. Voltage error due to dead time causes distortion in the current and induces vehicle impulses by torque ripple. In particular, this event tends to occur in a situation where the vehicle is started from a state where the vehicle is stopped, which is a low frequency region of the inverter. In order to improve these, it is thought that the equivalent circuit constant of the induction motor can be optimized by constantly monitoring the temperature of the induction motor and the optimization control that corrects the voltage error due to the dead time can be improved. It is very difficult to establish an algorithm corresponding to the entanglement.

  An object of the present invention made in view of such circumstances is to provide an inverter control device and a program capable of alleviating vehicle impulses due to a recognition error of an estimated speed that is likely to occur in an inverter low frequency region.

  In order to solve the above problems, an inverter control device according to the present invention is an inverter control device that controls an inverter and generates a slip in a rotor of the induction motor by applying an excitation current to the induction motor, An estimated speed calculation unit that estimates a rotor frequency that is a rotation frequency of the rotor by calculation, and an inverter frequency command generation unit that generates an inverter frequency command that indicates the frequency of the voltage output by the inverter based on the rotor frequency A frequency limiting unit that generates a limited frequency command that is limited so that the inverter frequency command does not become lower than a lower threshold, and a voltage command that indicates a voltage output from the inverter based on the limited frequency command. And a torque control unit that outputs to the motor.

  Furthermore, in the inverter control device according to the present invention, when the inverter frequency command is smaller than a lower limit threshold, the frequency limiting unit sets the limit frequency command as the lower limit threshold, and the inverter frequency command is equal to or higher than the lower limit threshold. In some cases, the limiting frequency command is the same as the inverter frequency command.

  Further, in the inverter control device according to the present invention, the frequency limiting unit raises the limit frequency command after lowering it to near zero when the rotor frequency is smaller than a reverse activation control threshold value that takes a negative value. It is characterized by that.

  Moreover, in order to solve the said subject, the program which concerns on this invention makes a computer function as said inverter control apparatus, It is characterized by the above-mentioned.

  According to the present invention, it is possible to mitigate vehicle impulses caused by recognition errors of estimated speeds that are likely to occur in the inverter low frequency region.

It is a figure which shows the structural example of the inverter main circuit system containing the inverter control apparatus which concerns on one Embodiment of this invention. It is a state transition diagram which shows control of the inverter control apparatus which concerns on one Embodiment of this invention. It is a figure explaining the starting from the stop in the inverter control apparatus which concerns on one Embodiment of this invention. It is a figure explaining reverse starting in the inverter control device concerning one embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the frequency and the angular frequency can be converted into each other only by different units, and any of them may be used in the calculation. Therefore, in this specification, the frequency is included in the notation of frequency.

  FIG. 1 shows a configuration example of an inverter main circuit system 1 including an inverter control device according to an embodiment of the present invention. The inverter main circuit system 1 includes an inverter control device 10, an inverter 20, a current detector 30, a voltage detector 40, and an induction motor 50.

The inverter 20 applies to the induction motor 50 a voltage v corresponding to a voltage command v ^* input from the inverter control device 10 and instructing an output voltage to the induction motor 50.

  The current detector 30 detects the current i flowing through the induction motor 50 and outputs the detection result to the inverter control device 10.

  The voltage detector 40 detects the voltage v applied to the induction motor 50 and outputs the detection result to the inverter control device 10.

The inverter control device 10 controls the inverter 20 and applies an exciting current to the induction motor 50 to cause the rotor of the induction motor 50 to slip. Further, the inverter control device 10 performs speed sensorless control. That is, without using the speed sensor, the rotation frequency (hereinafter referred to as “rotor frequency”) ω _m of the rotor of the induction motor 50 is obtained by calculation, and the torque control of the induction motor 50 is performed according to the torque command T ^* . The rotor frequency ω _m means the estimated speed of the vehicle. By transmitting the torque of the induction motor 50 to the wheel shaft of the vehicle, the vehicle can be accelerated or decelerated. The inverter control device 10 includes an estimated speed calculation unit 11, an inverter frequency command generation unit 12, a frequency limiting unit 13, and a torque control unit 14.

The estimated speed calculator 11 estimates the rotor frequency ω _m by calculation and outputs it to the inverter frequency command generator 12. For example, the rotor frequency ω _m is calculated using the current i detected by the current detector 30 and the voltage v detected by the voltage detector 40. In the case of performing control in the backward activation mode described later, the rotor frequency ω _m is also output to the frequency limiting unit 13.

Specifically, the estimated speed calculation unit 11 calculates the magnetic flux vector φ ₂ by the equation (1). Here, R ₁ is a primary resistance of the induction motor 50, and L ₁ , L ₂ , and M are a primary self-inductance, a secondary self-inductance, and a mutual inductance, respectively.

Instead of the voltage v, a voltage command v ^* output from the inverter control device 10 may be used. In that case, the inverter main circuit system 1 may not include the voltage detector 40.

Angular frequency omega _c of the magnetic flux vector phi _2, using the phi _2q is phi _2d and the q-axis component of the magnetic flux vector phi ₂ is a d-axis component of the magnetic flux vector phi _2, represented by the formula (2).

Further, the slip frequency ω _sc is calculated by the equation (3) using the magnetic flux vector φ ₂ and the current i detected by the current detector 30.

Then, the rotor frequency ω _m of the induction motor 50 is obtained by the equation (4).

The inverter frequency command generator 12 generates an inverter frequency command ω _i ^* that indicates the frequency of the voltage output from the inverter 20 based on the rotor frequency ω _m obtained by the estimated speed calculator 11, and the frequency limiter 13 Output to. The inverter frequency command generation unit 12 includes a slip frequency command calculation unit 121 and an addition unit 122.

The slip frequency command calculation unit 121 generates a slip frequency command ω _s ^* using the following equation (5) based on the input torque command T ^* and the secondary magnetic flux command φ ₂ ^*, and sends it to the adder 122. Output.

The adding unit 122 adds the rotor frequency ω _m calculated by the estimated speed calculating unit 11 and the slip frequency command ω _s ^* generated by the slip frequency command calculating unit 121, and outputs the voltage output from the inverter 20. An inverter frequency command ω _i ^* for instructing the frequency is generated and output to the frequency limiting unit 13.

The frequency limiter 13 generates a limit frequency command ω _iL ^* that is limited so that the inverter frequency command ω _i ^* generated by the adder 122 does not become smaller than a predetermined frequency lower limit threshold ω _iLMT , and the torque control unit 14 Output to. That is, when the frequency command ω _i ^* is _{equal to} or higher than the frequency lower limit threshold ω _iLMT , ω _iL ^* = ω _i ^*, and when the frequency command ω _i ^* is smaller than the frequency lower limit threshold ω _iLMT , ω _iL ^* = _Let ω _iLMT .

The torque control unit 14 receives the torque command T ^* , the secondary magnetic flux command φ ₂ ^* , the current i detected by the current detector 30, and the limited frequency command ω _iL ^* generated by the frequency limiting unit 13. Is done. Based on these inputs, the torque control unit 14 generates a voltage command v ^* indicating a voltage output from the inverter 20 so that the torque of the induction motor 50 follows the torque command T ^*, and outputs the voltage command v ^* to the inverter 20. .

Although FIG. 1 shows an example in which the torque command T ^* and the secondary magnetic flux command φ ₂ ^* are input to the torque control unit 14, the present invention is not limited to this. For example, the torque control unit 14 may calculate the secondary magnetic flux command φ ₂ ^* based on the input torque command T ^* .

Next, control of the inverter control device 10 will be described. FIG. 2 is a state transition diagram showing the control of the inverter control device 10. When starting from a stop, it is operated in the inverter frequency limit mode (state A). In the inverter frequency limit mode, the frequency limiter 13 sets the limit frequency command ω _iL ^* to a frequency lower limit threshold ω _iLMT that is a constant value.

When the inverter frequency command ω _i ^* input from the adder 122 exceeds the frequency lower limit threshold ω _{i LMT} after the state A, the operation is performed in the normal operation mode (state B). In the normal operation mode, the frequency limiter 13 sets the limit frequency command ω _iL ^* as the inverter frequency command ω _i ^* input from the adder 122.

When the reverse is detected when starting from the stop, the frequency limiting unit 13 operates in the reverse start mode (state C). For example, the inverter control device 10 determines that the vehicle is moving backward when the vehicle speed becomes −2 km / h. In the reverse activation mode, in the speed sensorless control, the rotor of the induction motor 50 is controlled, and the vehicle is operated to reverse, stop, and advance. At the time of reverse, the frequency limiter 13 lowers the limit frequency command ω _iL ^* to near zero. Then, when stopping, the phase sequence of the inverter current is switched, and the limit frequency command ω _iL ^* is increased so as to move forward.

After the state C, when the inverter frequency command ω _i ^* input from the adding unit 122 exceeds the frequency lower limit threshold ω _{i LMT} , the operation is performed in the normal operation mode (state B).

FIG. 3 is a diagram illustrating the control of the frequency limiting unit 13 when starting from the stop state. At the time of start-up from the stop, by applying an excitation current to the induction motor 50 to operate the rotor and causing the induction motor 50 to slip, the inverter control device 10 estimates the rotor frequency ω _m and performs torque control. carry out. However, when the rotor frequency ω _m is low, an error is likely to occur in the estimation. Therefore, the frequency limiter 13 sets the limit frequency command ω _iL ^* as the frequency lower limit threshold ω _iLMT (time t ₀ ), and starts the vehicle in the inverter frequency limit mode. Thereby, the vehicle impulse by the detection error of the estimated speed in an inverter low frequency area | region can be relieved.

When the inverter frequency command ω _i ^* input from the adder 122 exceeds the frequency lower limit threshold ω _iLMT , the control mode is switched to the normal operation mode, and the estimated speed based on the rotor frequency ω _m is recognized. Perform torque control. That is, the limit frequency command ω _iL ^* is set as the inverter frequency command ω _i ^* input from the adder 122. Note that the rotor frequency ω _m is always calculated by the estimated speed calculator 11 in order to accurately switch the control mode.

Here, immediately after starting from the stop (around time t ₀ ), the slip frequency, which is the difference between the frequency lower limit threshold ω _iLMT and the rotor frequency ω _m , becomes larger than the rated slip frequency ω _s (rated point). . For this reason, the induction motor torque is not stable, and some vehicle impulses may occur. Therefore, when the vehicle impulse occurs, the vehicle impulse may be reduced by adjusting the torque change amount of the induction motor 50 to be changed or a variable value.

FIG. 4 is a diagram for explaining the control of the frequency limiting unit 13 when the vehicle moves backward when starting from a stopped state. When starting the vehicle, as described in FIG. 3, first, the frequency limiting unit 13 sets the limiting frequency command ω _iL ^* as the frequency lower limit threshold ω _iLMT and starts the vehicle in the inverter frequency limiting mode.

When the vehicle is started from a state where the state and retracted stopped in upward gradient, when you start the vehicle at a frequency lower threshold omega _ILMT limit frequency command omega _iL ^* (around the time t _0), the frequency lower threshold omega _ILMT And the negative value of the rotor frequency ω _m is greatly different from the rated slip frequency ω _s (rated point). In this state, since the induction motor torque does not follow the limit frequency command ω _iL ^* , the gradient starting performance and the vehicle performance are affected.

Therefore, the rotor frequency omega _m recognizes that less than retraction activation control threshold omega _open as a negative value, that is, detecting the backward (time t _1), by starting the vehicle in backward startup mode, stop the vehicle And then move forward. To that end, the frequency limiting section 13 lowers the limit frequency command omega limit frequency command so _iL ^* passes through zero omega _iL ^* to near zero. Then, when stopping, the phase sequence of the inverter current is switched, and the limit frequency command ω _iL ^* is increased so as to move forward. Here, the vicinity of zero is a value that is greater than or equal to the reverse activation control threshold value _open and less than or equal to zero.

When the vehicle speed increases during the reverse activation mode and the inverter frequency command ω _i ^* input from the adder 122 exceeds the frequency lower limit threshold ω _iLMT , the control mode is switched to the normal operation mode, and the rotor frequency ω _m Torque control that recognizes the estimated speed is performed. That is, the limit frequency command ω _iL ^* is set as the inverter frequency command ω _i ^* input from the adder 122.

  Note that a computer can be preferably used to cause the above-described inverter control device 10 to function, and such a computer stores a program describing processing contents for realizing each function of the inverter control device 10. This program can be realized by reading out and executing this program by the CPU of the computer. This program can be recorded on a computer-readable recording medium.

As described above, the inverter control device 10 and the program thereof _{provide the} frequency lower limit threshold value ω _iLMT in advance in the inverter frequency command ω _i ^*, and the rotor of the induction motor 50 rotates below the frequency lower limit threshold value ω _iLMT. Separately from the process of recognizing the estimated speed and causing the inverter output, the inverter frequency command ω _i ^* is set as the frequency lower limit threshold ω _iLMT that is the lowest limit value. Therefore, it is possible to suppress the vehicle impulse that occurs when the estimated speed is erroneously recognized when the driving command is input and the vehicle is started from the stopped state.

In the present invention, the inverter frequency is output and the vehicle is started without going through the process of recognizing the estimated speed at the time of starting from the stop, but it is necessary to always recognize the estimated speed of the vehicle. The reason for this is that when this control is operated while the vehicle is moving backward, the rotor frequency ω _m is a negative value, so the larger the reverse speed, the larger the frequency lower threshold ω _iLMT, and the smaller the rotor torque for slipping. This is because the starting performance such as the gradient may be affected. If the vehicle is retracted, to recognize the estimated speed that is retracted, is retracted activation control threshold omega _open below (i.e., retracting speed be affected gradient starting performance at the inverter output by the frequency lower limit threshold omega _ILMT) and If this happens, it is necessary to operate in reverse start mode.

  The present invention is useful for an electric vehicle that performs speed sensorless control.

DESCRIPTION OF SYMBOLS 1 Inverter main circuit system 10 Inverter control apparatus 11 Estimated speed calculating part 12 Inverter frequency command generation part 13 Frequency limiting part 14 Torque control part 20 Inverter 30 Current detector 40 Voltage detector 50 Induction motor 121 Slip frequency command calculating part 122 Adder part

Claims (4)

An inverter control device that controls an inverter and generates a slip in a rotor of the induction motor by applying an excitation current to the induction motor,
An estimated speed calculator for estimating a rotor frequency, which is a rotation frequency of the rotor, by calculation;
Based on the rotor frequency, an inverter frequency command generator that generates an inverter frequency command that indicates the frequency of the voltage output by the inverter;
A frequency limiting unit that generates a limited frequency command limited so that the inverter frequency command is not smaller than a lower threshold;
Based on the limit frequency command, a torque control unit that outputs to the inverter a voltage command that indicates a voltage output by the inverter;
An inverter control device comprising:   When the inverter frequency command is smaller than a lower limit threshold, the frequency limiting unit sets the limited frequency command as the lower limit threshold, and when the inverter frequency command is equal to or higher than the lower limit threshold, The inverter control device according to claim 1, wherein the inverter control device is the same as the inverter frequency command.   The frequency limiting unit raises the limiting frequency command to a value close to zero when the rotor frequency is smaller than a reverse activation control threshold value that is a negative value, according to claim 1 or 2. The inverter control device described in 1. The program for functioning a computer as an inverter control apparatus as described in any one of Claim 1 to 3.

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