JP2010105763A - Power converter and elevator using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power converter capable of executing the torque pulsation correction of a motor in a high band frequency by utilizing simple torque correction information, and an elevator using the device. <P>SOLUTION: A control arithmetic part for calculating a command value to control an inverter for driving the motor through a vector control includes a storage means storing torque-current conversion gain corresponding to the magnetic pole position of the motor and induced voltage compensation voltage corresponding to the magnetic pole position of the motor. The control arithmetic part calculates a current command value of a torque shaft from the torque-current conversion gain and torque command value read from the storage means corresponding to the detection value of the magnetic pole position of the motor, and corrects the voltage command value of each phase or voltage command values of magnetic flux shaft and torque shaft according to the induced voltage compensation voltage read from the storage means corresponding to the detection value of the magnetic pole position of the motor, when driving the motor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power converter and control for suppressing torque pulsation and torque ripple in an elevator using the power converter.

  In a conventional power conversion device using inverter control, a vector control method is generally used in which a rotating coordinate system is controlled separately on a magnetic flux axis (d axis) and a torque axis (q axis). Usually, the induced voltage of the load motor is considered as an ideal sine wave, and the induced voltage constant and torque constant are set to constant values, and simple control is performed. As a conventional technique, in a motor control device described in Japanese Patent Laid-Open No. 7-46878 (Patent Document 1), in order to compensate for torque ripple, a correction current value corresponding to a torque command, speed information, and a rotational position of the motor. Is previously stored in a memory as torque error data, and is added to a torque command calculated assuming a sine wave. As another conventional technique, in the torque pulsation control method and control device for a permanent magnet embedded motor described in JP-A-11-103588 (Patent Document 2), a correction waveform based on a torque pulsation correction pattern prepared in advance is used. A method of suppressing torque pulsation by multiplying the basic current is used.

JP 7-46878 A JP-A-11-103588

FIG. 7 is a configuration diagram of a conventional control system, in which a voltage converted into a direct current by a rectifier 2 and a rectifier 2 for converting a commercial alternating voltage of the power source 1 and the power source 1 into an alternating voltage of an arbitrary frequency is converted. The main circuit portion of the power converter is constituted by the inverter 3, the motor 4 driven by the inverter 3, and the rotary encoder 5 for detecting the rotational speed and magnetic pole position of the motor 4. The inverter 3 is driven by controlling the magnetic flux axis component and torque axis component of the rotating coordinate system based on the vector control of the electric motor. In the magnetic flux axis, the difference between the magnetic flux axis current command id * and the magnetic flux axis current id obtained by converting the output current of the inverter 3 to the rotational coordinate is input to the magnetic flux axis current control system block 6 to input the magnetic flux axis. Calculate the voltage command value of the component. On the torque axis, the torque command value τ * is obtained by inputting the difference between the speed command ω * of the motor 4 and the rotational speed ω obtained from the rotary encoder 5 to the speed control system block 7. Further, the torque shaft current command iq * is obtained by inputting the torque-current conversion gain block (Ka) 18. Here, the torque-current conversion gain block (Ka) is
Ka = 1 / Kit
Where Kit is a torque constant (unit [N · m / A]). The voltage command can be obtained by inputting the difference between the torque shaft current command iq * and the torque shaft current iq obtained by converting the output current of the inverter 3 to the rotation coordinate to the torque shaft current control system block 9. Further, the induced voltage compensation voltage obtained by integrating the rotational speed ω obtained from the rotary encoder 5 and the induced voltage constant Ke (unit V / rpm) which is the induced voltage compensation gain 19 is added to obtain the voltage of the torque shaft component. Calculate the command. The voltage command values vu *, vv *, and vw * for each phase of the inverter 3 are calculated by performing three-phase to two-phase conversion (10) between the voltage command for the magnetic flux axis component and the voltage command for the torque axis component.

  However, in the conventional control, when the induced voltage waveform of the load motor during constant speed operation is close to an ideal sine wave, the operation works well. However, the induced voltage waveform of the load motor shown in FIG. If the torque constant Kit and the induced voltage constant Ke are calculated as constant values under conditions including a strain component as in (), torque pulsation and torque ripple are caused. The distortion component included in the induced voltage waveform in FIG. 8 is generated depending on the magnet shape of the load motor. For this reason, for example, in an application such as an elevator where there is a high demand for suppressing deterioration in riding comfort such as vibration, an expensive motor in which the magnet shape is precisely processed to reduce torque pulsation and torque ripple is used.

  In the prior art described in Patent Document 1, in order to compensate for torque ripple, a torque command, speed information, and a correction current value corresponding to the rotational position of the motor are stored in advance in a memory as torque error data, and a correction amount is stored. Is added to the current command value. In this method, torque ripple can be compensated with high accuracy. However, since the number of prerequisite parameters is extremely large, the number of dimensions of the array stored in the memory is increased and complicated. Furthermore, the number of correction amounts that need to be implemented in advance is extremely large.

  In the prior art described in Patent Document 2, the information on the torque pulsation wave stored in the torque pulsation memory is converted into a torque correction waveform according to a torque pulsation correction pattern prepared in advance and integrated with the basic current. However, also in this case, it is necessary to perform a load test for detecting the torque ripple component in advance, and the pulsation correction pattern needs to be subjected to a complicated calculation.

  The present invention has been made in consideration of the above-described problems, and provides a power converter that can perform torque pulsation correction of a motor using simple torque correction information and an elevator using the same.

  In order to solve the above problems, a torque-current conversion gain corresponding to the magnetic pole position of the motor, a magnetic pole of the motor, and a control arithmetic unit for calculating a command value for controlling the inverter driving the motor by vector control Storage means for storing the induced voltage compensation voltage corresponding to the position is provided. The control calculation unit calculates the current command value of the torque shaft from the torque-current conversion gain and the torque command value read out from the storage means corresponding to the detected value of the magnetic pole position of the motor when the motor is driven, and Then, the voltage command value of each phase or the voltage command value of the magnetic flux axis and the torque axis is corrected according to the induced voltage compensation voltage read from the storage means corresponding to the detected value of the magnetic pole position of the motor.

  The other features of the present invention will become clear from the following description.

  According to the present invention, when calculating a command value for vector control, torque pulsation of a motor can be easily corrected by using a torque-current conversion gain and an induced voltage compensation voltage corresponding to the magnetic pole position of the motor. it can.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a power converter according to a first embodiment of the present invention and an elevator driven using the power converter. The main circuit portion of the power converter is composed of a power source 1, a rectifier 2 that converts commercial AC voltage of the power source 1 into DC voltage, an inverter 3 that converts the voltage converted into DC by the rectifier 2 into an AC voltage of an arbitrary frequency, and an inverter 3 The motor 4 is driven by the rotary encoder 5 that detects the rotational speed and magnetic pole position of the motor 4. The motor 4 is connected to a sheave 11 and a car 13 and a weight 14 are suspended in a hoistway (not shown) by a rope 12 wound around the sheave 11. When the motor 4 is driven by the power converter and the sheave 11 is rotationally driven, the rope 12 is driven, and the car 13 and the weight 14 are raised and lowered in opposite directions in the hoistway.

When the induced voltage waveform when the motor 4 is driven at a constant speed is an ideal sine wave, the voltage is given as a time derivative of the magnetic flux according to Faraday's law of electromagnetic induction. In this case, when the magnetic flux is converted into rotational coordinates, the magnetic flux axis (d-axis) component is zero, and the torque axis (q-axis) component is a constant DC value. On the other hand, when distortion is superimposed on the induced voltage waveform as shown in FIG. 8, the magnetic flux axis (d-axis) component and the torque axis (q-axis) component pulsate as the magnetic pole position θ of the motor changes. Here, the magnetic flux of the magnetic flux axis component is Φd (θ), the magnetic flux of the torque shaft component is Φq (θ), and the currents of the magnetic flux axis component and the torque shaft component are id, iq, the motor of the magnetic flux axis component and the torque axis component, respectively. When the inductance is Ld and Lq, respectively, the torque T is
T = (Ld−Lq) · id · iq + Φd (θ) · id + Φq (θ) · iq (1)
It becomes. In the equation (1), when the magnetic flux axis component current id is zero,
T = Φq (θ) · iq (2)
That means
iq = (1 / Φq (θ)) · T (3)
It becomes. Equation (3) indicates that even when a constant torque is given as a command value, the current of the torque axis component varies according to a gain (1 / Φq (θ)) that varies with the magnetic pole position θ as a parameter. In other words, even when a distortion component is superimposed on the induced voltage waveform, the torque-current conversion gain which is set to zero as the current command value id * of the magnetic flux axis component and is given as a constant value in the conventional method of FIG. Torque pulsation can be suppressed by using the block (Ka) 18 as the torque-current conversion gain block 8 with the magnetic pole position consisting of the gain (1 / Φq (θ)) that varies with the magnetic pole position θ as a parameter. In the first embodiment of FIG. 1, the gain (４1 / Φq (θ)) that varies with the magnetic pole position as a parameter is stored in advance in the storage means as the pulsation correction information table 17, and the motor 4 obtained from the rotary encoder 5 is stored. The gain (∝1 / Φq (θ)) is read out according to the magnetic pole position.

The gain stored in the pulsation correction information table 17 can be measured in advance as follows. First, the induced voltages (Vuv (θ), Vvw (θ), Vwu (θ)) between the lines are detected at a constant speed as in the induced voltage between lines (U-V phase) in FIG. next,
Vu = (Vuv (θ) −Vwu (θ)) / 3 (4)
Vv = (Vvw (θ) −Vuv (θ)) / 3 (5)
Vw = (Vwu (θ) −Vvw (θ)) / 3 (6)
The torque axis voltage Vq can be calculated by calculating the induced voltage of each phase and converting this to rotational coordinates. Since the torque shaft voltage Vq is given by the product of the magnetic flux component of the torque shaft and the angular velocity component (frequency component), a torque-current conversion gain using the magnetic pole position as a parameter can be calculated in advance by dividing by a constant speed.

  Next, in the conventional system shown in FIG. 7, the induction obtained by integrating the rotational speed ω and the induced voltage compensation gain (induced voltage constant Ke (unit: V / rpm)) 19 with the output of the torque shaft current control system block 9. The voltage command for the torque axis component is calculated by adding the voltage compensation voltage. However, in this case as well, when the induced voltage waveform during constant speed driving is not a sine wave as shown in FIG. 8, the compensation voltage itself becomes an error factor. In particular, an induced voltage waveform in which distortion is superimposed as shown in FIG. 8 has a frequency component (sixth harmonic component) that is six times the fundamental frequency, and causes torque pulsation. FIG. 2 is a diagram showing the relationship between the pulsation component and the control region of the current control system. As shown in FIG. 2A, when the sixth harmonic frequency (6f) is sufficiently lower than the crossover frequency of the current control system (frequency fc that crosses 0db), the error factor can be suppressed by the current control system. As the frequency approaches the crossover frequency, the control performance decreases. When the sixth harmonic frequency (6f) is higher than the crossover frequency (fc) of the current control system as shown in FIG. Cannot be suppressed, and torque pulsation occurs. Therefore, in the first embodiment of FIG. 1, instead of the induced voltage compensation gain 19 of FIG. 7, the phase voltage component of the induced voltage corresponding to the magnetic pole position θ is added to the output of the two-phase to three-phase conversion block. The phase voltage component of the induced voltage is also stored in advance in the pulsation correction information table 17 and converted according to the magnetic pole position of the motor 4 obtained from the rotary encoder 5. The phase voltage component of the induced voltage to be memorized is a value (reference voltage value) obtained by dividing the value that can be derived from the equations (4), (5), and (6) by the rotational speed (a constant speed amount) at the time of detection. At the time of control, the compensation voltage value can be derived by multiplying the value read from the pulsation correction information table 17 by the rotational speed or the rotational speed command value. Thereby, torque pulsation can be reduced in a wide frequency band.

  FIG. 3 is an experimental result showing the torque pulsation suppressing effect of this embodiment when the motor having the induced voltage characteristics shown in FIG. 8 is used. FIG. 3A shows the frequency characteristics of torque in the conventional control method, and the dotted line portion corresponds to the frequency component of the sixth harmonic. In this case, it can be confirmed that the 6th harmonic component is remarkably generated. FIG. 3B shows the result when only the torque-current conversion gain is adjusted according to the magnetic pole position as described above. In this case, the characteristics are almost the same as in the case of the conventional control method of FIG. 3A, and it can be seen that the frequency components of the sixth harmonic are remarkably generated. This is because the gain for the frequency component of the sixth harmonic component is at a small point in the current control system as shown in FIG. FIG. 3C shows the result when only the induced voltage compensation is adjusted according to the magnetic pole position as described above. Also in this case, the characteristics are almost the same as in the case of the conventional control method of FIG. 3A, and it can be seen that the frequency components of the sixth harmonic are remarkably generated. This is a pulsation component generated when the torque-current conversion gain is a constant value. In general, the control performance improves as the gain of the torque axis current control system increases. However, as the pulsating component increases, the error component becomes more prominent. FIG. 3 (d) shows the result when both the torque-current conversion gain and the induced voltage compensation are adjusted according to the magnetic pole position. In this case, it can be seen that the frequency component of the sixth harmonic surrounded by the dotted line portion can be greatly reduced. That is, it can be understood that in order to perform torque pulsation control in a wide band, it is necessary to perform pulsation correction corresponding to the magnetic pole position for both the torque-current conversion gain and the induced voltage compensation.

  In the pulsation correction information table 17 of the first embodiment, only the magnetic pole position of the motor 4 is sufficient as the parameter, and the object to be measured in advance is sufficient only with the induced voltage waveform. The amount of data prepared in advance can be reduced. In particular, in a target in which the target load uses the rotary encoder 5 such as an elevator that requires high position / speed accuracy, the magnetic pole position of the motor 4 can be accurately grasped, so that highly accurate correction can be performed. However, it goes without saying that the pulsation correction according to the present embodiment can be employed even when the magnetic pole position is estimated by position sensorless control or the like. In addition, the induced voltage compensation value of each phase is obtained as a table by reading the values for three phases from the data for one phase, taking into account the phase difference of 120 degrees using the symmetry of the three-phase motor. The amount of data prepared in advance can be reduced.

  In the first embodiment of FIG. 1, the position information θ is detected via the integrator 15 for the speed information obtained from the rotary encoder 5. However, when the control calculation is performed by a microcomputer or the like, phase advance may occur before the command is reflected on the detected position information θ. This is due to a dead time delay element of the control system, and the phase advance amount becomes large especially when the motor 4 rotates at a high speed. Therefore, the accuracy of pulsation correction can be improved by performing phase correction by the phase shift 16 in accordance with the rotational speed of the motor 4. That is, since the control delay time td of the microcomputer can be generally grasped at the time of design, the advance phase amount can be grasped by multiplying the detection speed ω [rad / s] by the control delay time td. By using θ ′ obtained by adding the advance phase amount to the position information θ, pulsation correction information at a magnetic pole position closer to the time of command reflection can be obtained, and the effect of reducing pulsation can be increased.

  In the first embodiment, although the torque pulsation component can be compensated, the output voltage range may be smaller than that in the conventional control. In particular, the amount of compensation increases when the amount of distortion superimposed on the induced voltage is large. Such a decrease in the output voltage range can be suppressed by limiting the control range of the torque pulsation compensation control. FIG. 4 is an example in which the control range of the torque pulsation compensation control for the vibration generation section is limited. In an elevator, if the spring constant element, which depends on the length and material of the rope, and the resonance frequency of the mechanical system, which is determined by the weight element of the car / weight part and the loader, match the frequency of the above harmonic components, Vibrates vigorously. In other words, torque ripple compensation control is performed in the section where the harmonic component of the motor's rotational frequency (rotational speed) is close to the resonance frequency of the mechanical system, and normal control is performed in other sections to suppress car vibration. In addition, the output voltage range can be prevented from decreasing.

  FIG. 5 is a flowchart of switching between pulsation compensation control and normal control. First, the presence / absence of an operation command is confirmed (step 20), and if there is no operation command, the process ends. If there is an operation command, it is determined whether or not the harmonic component of the rotational frequency (rotational speed) of the motor is in a vibration generation region near the resonance frequency of the mechanical system (step 21). In the case where the vibration generation region is generated, the operation is performed in the pulsation compensation control mode (step 22). On the other hand, if the vibration generation region is out of the region where the vibration is generated, the operation is performed in the normal control mode (step 23). The control mode can be switched by performing this operation at a constant period such as a control task for a speed command of the microcomputer.

  Since the resonance frequency of the mechanical system can be grasped at the time of design or installation, the control section can be set in advance. The spring constant determined by the rope length (the length of the rope 12 between the sheave 11 and the car 13 in the first embodiment of FIG. 1) can be grasped from the position information of the car, Using the information of the load sensor, it is possible to accurately grasp the weight element depending on the increase or decrease of passengers or the like. As a result, the resonance frequency of the mechanical system can be grasped at an instantaneous level, and the control range of torque pulsation compensation control can be minimized by comparing with the harmonic frequency that can be calculated from the rotational frequency command value of the motor. it can. In addition, torque pulsation compensation control is performed in the motor rotation frequency region and the car position region, where the car vibration is likely to occur, and in other areas, the output voltage can be easily adjusted by driving in the normal control system. The range reduction region can be reduced.

  FIG. 6 shows a power conversion apparatus according to a second embodiment of the present invention and an elevator driven thereby. The main circuit portion of the power converter and the form of the elevator are the same as those in the first embodiment of FIG. In the control system block, the correction means for the induced voltage compensation is different. That is, in the first embodiment of FIG. 1, the phase voltage component of the induced voltage corresponding to the magnetic pole position θ is added to the output of the two-phase to three-phase conversion block 10, whereas the second embodiment of FIG. Then, an induced voltage compensation component corresponding to the magnetic pole position θ is added to the output of the rotational coordinate system (flux axis, torque axis system) on the input side of the two-phase / three-phase conversion block 10. The compensation value added here is the magnetic flux axis voltage corresponding to the magnetic pole position θ obtained by rotating the phase voltage component of the induced voltage corresponding to the magnetic pole position θ of the first embodiment and the torque corresponding to the magnetic pole position θ. The shaft voltage is added to the magnetic flux axis and the torque axis, respectively. In this case, the information stored in the pulsation correction information table 17 is the rotational speed at the time of detection of the reference voltage values (values (4), (5), (6)) of the first embodiment. (Value divided by (a constant speed amount)) is a value obtained by converting the rotational coordinates, and during control, compensation corresponding to the magnetic pole position θ to be added by multiplying the rotational speed or the rotational speed command value as in the first embodiment. The voltage value can be calculated. In the second embodiment of FIG. 6, the same pulsation reducing effect as that of the first embodiment of FIG. 1 can be obtained.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea of the present invention.

It is a block diagram which shows the 1st Example of this invention. It is a figure showing the relationship between a pulsation component and a control area. It is an experimental result which shows a torque pulsation suppression effect. It is an example which limits the control range of torque pulsation compensation control with respect to a vibration generation area. It is a flowchart of switching of pulsation compensation control and normal control. It is a block diagram which shows the 2nd Example of this invention. It is a block diagram of the conventional control system. It is an example of the induced voltage waveform of a motor.

Explanation of symbols

1 Power Supply 2 Rectifier 3 Inverter 4 Motor 5 Rotary Encoder 11 Sheave 12 Rope 13 Ride Car 14 Weight

Claims (10)

In a power conversion device including an inverter that drives a motor and a control calculation unit that calculates a command value for controlling the inverter by vector control.
The control calculation unit includes a storage unit that stores a torque-current conversion gain corresponding to the magnetic pole position of the motor and an induced voltage compensation voltage corresponding to the magnetic pole position of the motor, and from the storage unit when the motor is driven, A torque shaft current command value is calculated from the torque-current conversion gain and torque command value read in correspondence with the detected value of the magnetic pole position of the motor, and the detected value of the magnetic pole position of the motor is stored from the storage means. A voltage conversion value for each phase is corrected in accordance with the induced voltage compensation voltage read in correspondence with the power conversion device. In a power conversion device including an inverter that drives a motor and a control calculation unit that calculates a command value for controlling the inverter by vector control.
The control calculation unit includes a storage unit that stores a torque-current conversion gain corresponding to the magnetic pole position of the motor and an induced voltage compensation voltage corresponding to the magnetic pole position of the motor, and from the storage unit when the motor is driven, A torque shaft current command value is calculated from the torque-current conversion gain and torque command value read in correspondence with the detected value of the magnetic pole position of the motor, and the detected value of the magnetic pole position of the motor is stored from the storage means. A voltage conversion value for the magnetic flux axis and the torque axis of the rotating coordinate system is corrected in accordance with the induced voltage compensation voltage read out in accordance with the power conversion device.   2. The torque-current conversion gain according to claim 1, wherein the torque-current conversion gain has a magnitude that is inversely proportional to the amount of magnetic flux generated by the magnet inside the motor, which varies depending on the magnetic pole position, and the induced voltage compensation voltage corresponding to the magnetic pole position of the motor is different for each motor. A power conversion device having a value similar to an induced voltage waveform of a phase.   3. The torque-current conversion gain according to claim 2, wherein the torque-current conversion gain has a magnitude that is inversely proportional to the amount of magnetic flux generated by a magnet inside the motor that varies depending on the magnetic pole position, and the induced voltage compensation voltage corresponding to the magnetic pole position of the motor is different for each motor. A power converter characterized by having a value similar to a waveform obtained by rotating coordinate transformation of a phase induced voltage waveform.   2. The value obtained by adding a phase advance amount proportional to the rotational speed of the motor to the detected value of the magnetic pole position as a second magnetic pole position according to claim 1, and when the motor is driven, the storage means changes the value to the second magnetic pole position. A current command value of the torque axis is calculated from the torque-current conversion gain and the torque command value read correspondingly, and according to the induced voltage compensation voltage read corresponding to the second magnetic pole position And correcting the voltage command value of each phase.   3. The value obtained by adding a phase advance amount proportional to the rotational speed of the motor to the detected value of the magnetic pole position as a second magnetic pole position according to claim 2, and when the motor is driven, the storage means changes the value to the second magnetic pole position. The current command value of the torque shaft is calculated from the torque-current conversion gain and the torque command value read correspondingly, and the induction is read from the storage means corresponding to the second magnetic pole position. A power converter that corrects the voltage command values of the magnetic flux axis and the torque axis according to a voltage compensation voltage.   3. The torque-current conversion gain and the induced voltage from the storage means when the harmonic frequency of the motor rotation frequency is close to the mechanical resonance frequency of the elevator during operation of the elevator. A power converter that reads a compensation voltage.   8. The mechanical resonance frequency of the elevator according to claim 7, wherein the mechanical resonance frequency of the elevator is calculated from position information of the car, information of a load sensor in the car or position information of the car, and information of a load sensor in the car. The power converter characterized by this. In an elevator comprising a car and a weight suspended by a rope, a sheave around which the rope is wound, a motor that rotationally drives the sheave, and a power converter that drives the motor,
The power conversion device includes an inverter that drives the motor, and a control calculation unit that calculates a command value for driving the inverter by vector control,
The control calculation unit includes a storage unit that stores a torque-current conversion gain corresponding to the magnetic pole position of the motor and an induced voltage compensation voltage corresponding to the magnetic pole position of the motor. From the torque-current conversion gain and the torque command value read in correspondence with the detected value of the magnetic pole position of the motor, and the current command value of the torque axis is calculated from the storage means. An elevator that corrects a voltage command value of each phase in accordance with the induced voltage compensation voltage read in correspondence with a detected value. In an elevator comprising a car and a weight suspended by a rope, a sheave around which the rope is wound, a motor that rotationally drives the sheave, and a power converter that drives the motor,
The power conversion device includes an inverter that drives the motor, and a control calculation unit that calculates a command value for driving the inverter by vector control,
The control calculation unit includes a storage unit that stores a torque-current conversion gain corresponding to the magnetic pole position of the motor and an induced voltage compensation voltage corresponding to the magnetic pole position of the motor. From the torque-current conversion gain and the torque command value read in correspondence with the detected value of the magnetic pole position of the motor, and the current command value of the torque axis is calculated from the storage means. An elevator that corrects voltage command values of a magnetic flux axis and a torque axis of a rotating coordinate system in accordance with the induced voltage compensation voltage read in correspondence with a detected value.

Images