JP2019205245A - Motor controller and motor drive system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control device capable of ensuring good response performance even if a control deviation suddenly changes, and a motor drive system using the motor control device. A motor control device controls driving of a motor 200 by an inverter 100 and generates a control signal to the inverter 100 by pulse width modulation, and a carrier frequency in pulse width modulation according to a control deviation. When the control deviation is equal to or greater than a predetermined value, the carrier frequency calculation unit 70 sets the carrier frequency to the maximum value allowed in the pulse width modulation of the inverter 100. [Selection diagram] Figure 2

Description

  The present invention relates to a motor control device that controls driving of a motor, and a motor drive system in which the motor control device is used.

  A motor drive system mounted on an electric vehicle such as a hybrid vehicle or an electric vehicle is desired to have low loss and high response. On the other hand, a technique for changing the carrier frequency (frequency of the carrier signal) of pulse width modulation control (hereinafter referred to as “PWM control” (PWM)) in the control device according to the control deviation is known. ing.

  For example, in the prior art described in Patent Document 1, the control deviation is compared with the threshold value TH1 and the threshold value TH2 (<TH1), and when the control deviation is equal to or greater than the threshold value TH1, the carrier up value for increasing the carrier frequency fc (< 0) is integrated, and when the control deviation is equal to or less than the threshold value TH2, a carrier down value (> 0) for decreasing the carrier frequency fc is integrated. Then, the carrier frequency is determined according to the integration result. As a result, the larger the control deviation, the shorter the carrier period of the PWM control, so that the control response is improved. In addition, since the integration is used, the carrier frequency can be adjusted accurately even if a detection error occurs in the control deviation due to noise or the like.

JP 2016-111982 A

  In the above-described prior art, when the control deviation increases rapidly, for example, when the electric vehicle is suddenly accelerated, the adjustment of the carrier frequency is delayed, and there is a fear that sufficient response performance may not be obtained.

  Therefore, the present invention provides a motor control device capable of ensuring good response performance even when the control deviation changes suddenly, and a motor drive system using the motor control device.

  In order to solve the above problems, a motor control device according to the present invention controls driving of a motor by an inverter, and generates a control signal to the inverter by pulse width modulation, and according to a control deviation. A carrier frequency calculation unit that sets a carrier frequency in pulse width modulation, and the carrier frequency calculation unit sets the carrier frequency to a maximum value allowed in the pulse width modulation of the inverter when the control deviation is equal to or greater than a predetermined value. Set to.

  In order to solve the above problems, a motor driving system according to the present invention includes a motor, an inverter that supplies AC power to the motor, and a motor control device that controls driving of the motor by the inverter, The motor control device is the motor control device according to the present invention.

  According to the present invention, the responsiveness to the control deviation is improved.

  Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.

The structure of the motor drive system which is Example 1 is shown. 2 is a functional block diagram illustrating a configuration of Embodiment 1. FIG. 4 is a flowchart illustrating processing operations executed in a carrier frequency calculation unit according to the first embodiment. 6 is a flowchart illustrating a processing operation executed in a carrier frequency calculation unit according to the second embodiment. An example of the carrier frequency setting operation | movement of the carrier frequency calculation part in Example 2 is shown.

  Hereinafter, embodiments of the present invention will be described with reference to the following Examples 1 and 2 with reference to the drawings. In each figure, the same reference numerals indicate the same constituent elements or constituent elements having similar functions.

  FIG. 1 shows the configuration of a motor drive system that is Embodiment 1 of the present invention. The motor drive system is mounted on an electric vehicle such as a hybrid vehicle or an electric vehicle.

  The motor drive system includes a motor 200, a position sensor 210 that detects a rotor position of the motor 200, a current sensor 220 that detects a motor current, an inverter 100 that supplies AC power to the motor 200, and a motor 200 that uses the inverter 100. The motor control apparatus 1 which controls the drive of this is provided. As the motor 200, a three-phase synchronous motor such as a permanent magnet synchronous motor is used.

The motor control device 1 includes a torque command T ^* from the outside (for example, a host control device), three-phase motor currents i _u , i _v , i _w detected by the current sensor 220, and rotation detected by the position sensor 210. The inverter 100 is PWM controlled based on the child position θ.

  The inverter 100 includes switching elements 110a to 110f. Switching element 110a and switching element 110b constitute a U-phase upper arm and a U-phase lower arm, respectively. Switching element 110c and switching element 110d constitute a V-phase upper arm and a V-phase lower arm, respectively. Switching element 110e and switching element 110f constitute a W-phase upper arm and a W-phase lower arm, respectively. In each arm, diodes are connected in antiparallel to the switching elements, but these diodes are so-called freewheeling (circulating) diodes.

  In the first embodiment, metal oxide field effect transistors (MOSFETs) are applied as the switching elements 110a to 110f. Note that insulated gate bipolar transistors (IGBTs) or the like may be applied as the switching elements 110a to 110f. Further, the freewheeling diode may be externally attached to the switching element or may be incorporated therein. When the switching element is a MOSFET as in this embodiment, a parasitic diode can be used as a freewheeling diode.

The inverter 100 is configured such that the switching elements 110a to 110f are turned on / off based on the switching signal S generated by the motor control device 1, thereby converting a DC voltage applied from a DC power supply (not shown) into an AC voltage. Convert. When the AC voltage output from the inverter 100 is applied to the stator coil of the motor 200, three-phase motor currents i _u , i _v and i _w flow. When a rotating magnetic field is generated in the motor 200 by the three-phase motor currents i _u , i _v , i _w , the rotor of the motor 200 rotates.

  The position sensor 210 detects the rotor position of the motor 200 and outputs the detected rotor position θ. As the position sensor 210, for example, a rotary encoder or the like is applied. Note that the rotor position θ may be estimated without using the position sensor 210 by applying a so-called position sensorless method.

The current sensor 220 detects a three-phase motor current flowing through the motor 200 and outputs the detected three-phase currents i _u , i _v and i _w . For example, CT (Current Transformer) is applied as the current sensor 220.

  FIG. 2 is a functional block diagram showing the configuration of the first embodiment shown in FIG.

  In FIG. 2, portions excluding the inverter 100, the motor 200, the position sensor 210, and the current sensor 220 show functional blocks of the motor control device 1 in FIG. The motor control device 1 is configured by a microcomputer, FPGA, ASIC, or the like. For example, a microcomputer operates as each functional unit by executing a predetermined program.

  As shown in FIG. 2, in the first embodiment, generally known vector control means is applied except for means for changing the carrier frequency described later (carrier frequency calculation unit 70 in FIG. 2). The

The current command calculation unit 10 calculates a dq-axis current command value ( _id ^* , _iq ^* ) in the rotating coordinate system based on the input torque command value T ^* , angular velocity (ω), and rotor position θ. To do.

dq-axis current control unit 20, dq-axis current command value _{^{(i d *, i q *}} ) and on the basis of a deviation between the dq axis current detection value _(i d, i _q), the proportional control gain command value is set The dq axis voltage command value (v _d ^* , v _q ^* ) is calculated by control, integral control, or the like.

The coordinate conversion unit 30 performs UVW phase voltage command values (v _u ^* , v _v ^* , v _w by coordinate conversion based on the dq axis voltage command values (v _d ^* , v _q ^* ) and the rotor position θ. ^* ) Is calculated.

The PWM signal generation unit 40 is a switching signal for performing on / off control of the switching elements 110a to 110f by PWM that compares the UVW phase voltage command values (v _u ^* , v _v ^* , v _w ^* ) with the carrier signal. S is generated. Here, the carrier frequency is set to a carrier frequency command value (f _c ^* ) calculated by a carrier frequency calculation unit 70 described later.

The dq conversion unit 50 converts the three-phase motor currents i _u , i _v , i _w detected by the current sensor 220 into a dq axis in the rotating coordinate system by coordinate conversion based on the rotor position θ detected by the position sensor 210. The current detection value (i _d , i _q ) is converted.

  Based on the rotor position θ detected by the position sensor 210, the speed conversion unit 60 calculates the angular velocity ω by time differentiation calculation.

The carrier frequency calculator 70, dq-axis current command value _{^{(i d *, i q *}} ) and dq-axis current detection value _(i d, _{i q)} and deviation, based on the angular velocity omega, the carrier frequency command value ( f _c ^*) and calculates a control gain command value. The carrier frequency command value (f _c ^* ) and the control gain command value are sent to the PWM signal generation unit 40 and the dq axis current control unit 20, respectively.

  FIG. 3 is a flowchart showing processing operations executed in the carrier frequency calculation unit 70 in FIG.

First, in step A1, dq axis current command values _{^{(i d *, i q *}} ) or the dq axis current detection value _(i d, _{i q)} deviation, that is, the control deviation is equal to or greater than the predetermined value is determined . If the deviation is greater than or equal to a predetermined value (Yes in step A1), then step A2 is executed, and if the deviation is smaller than the predetermined value (No in step A1), then step A4 is executed. This predetermined value is set in advance based on a desired control response speed and stored in the motor control device 1. When the control response speed is increased, the predetermined value is reduced.

In step A2, the carrier frequency command value (f _c ^* ) is set to the maximum value allowed in the PWM control of the inverter 100. Thereby, the carrier frequency in the PWM signal generation unit 40 (FIG. 2) is set to the maximum value. This maximum value is set according to the processing speed of the control circuit constituting the motor control device 1, the allowable inverter switching speed (or switching loss), and the like. When step A2 is executed, next step A3 is executed.

In step A3, the value of the control gain of proportional control and integral control in the dq-axis current control unit 20 is changed to a value corresponding to the carrier frequency command value (f _c ^* ) (that is, the maximum value) set in step A2. . Here, the control gain and the carrier frequency are in a proportional relationship, and the value of the control gain is changed to a larger value when the carrier frequency command value becomes higher. Thereby, the response performance of the motor control device 1 is improved. In addition, when the dq-axis current vibration occurs due to the change in the control gain, the vibration can be suppressed by providing a limiter that limits the rate of change in the control gain.

In step A4, the carrier frequency command value (f _c ^* ) is calculated according to the rotational speed of the motor 200, and according to the angular velocity ω in this embodiment. Accordingly, the value of the carrier frequency is set to the calculated carrier frequency command value (f _c ^* ). Here, the carrier frequency command value (f _c ^* ) and the angular velocity ω are in a proportional relationship, and the carrier frequency command value (f _c ^* ) is set to a higher value as the angular velocity increases. For example, the carrier frequency command value (f _c ^* ) is set to a value that is an integral multiple (twice or more) of the output frequency (frequency of AC power output from the inverter 100) calculated from the angular velocity (ω). Once step A4 is executed, next step A5 is executed.

  In step A5, the control gain in the dq-axis current control unit 20 is changed as in step A3 described above.

  When step A3 or step A5 is executed, the process returns to step A1, and step A1 and subsequent steps are repeatedly executed.

As described above, according to the first embodiment, when the control deviation exceeds a predetermined value, the carrier frequency of the PWM control is set to a predetermined maximum value, so that the control response performance when the control deviation suddenly increases. Will improve. Furthermore, since the control gain is changed according to the set carrier frequency command value (f _c ^* ), the control response performance is improved.

  Next, a motor drive system that is Embodiment 2 of the present invention will be described. The configuration of the motor drive system is the same as that of the first embodiment (FIGS. 1 and 2).

  Hereinafter, a difference from the first embodiment, that is, an operation of the carrier frequency calculation unit 70 (FIG. 2) will be described.

  FIG. 4 is a flowchart illustrating processing operations executed in the carrier frequency calculation unit 70 in the second embodiment.

First, in step B1, the deviation of the Example 1 in the same manner (step A1 in FIG. 2), dq axis current command values _{^{(i d *, i q *}} ) and dq-axis current detection value _(i d, _{i q),} That is, it is determined whether the control deviation is equal to or greater than a predetermined value. If the deviation is greater than or equal to a predetermined value (Yes in step B1), then step B2 is executed. If the deviation is smaller than the predetermined value (No in step B1), then step B4 is executed.

  In step B2, similarly to the first embodiment (step A2 in FIG. 2), the carrier frequency is set to the maximum value. When step B2 is executed, next, step B3 is executed.

In step B3, as in the first embodiment (step A3 in FIG. 2), the control gain value in the dq-axis current control unit 20 is the carrier frequency command value (f _c ^* ) set in step B2 (ie, the maximum value). ).

  Since the above-described processing operations (steps B1 to B3) in the second embodiment are the same as those in the first embodiment, the effects thereof are the same as those in the first embodiment. On the other hand, the processing operation in the case where it is determined in step B1 that the control deviation is smaller than the predetermined value (No in step B1) is different from that in the first embodiment, as will be described below.

  In step B4, it is determined whether a predetermined time has elapsed since the carrier frequency was changed. Here, the predetermined time is set to the time required until the vibration that can occur in the dq-axis current immediately after the carrier frequency is changed, and is stored in the motor control device 1 in advance. This step B4 can suppress instability of control. If it is determined in step B4 that the predetermined time has not elapsed (No in step B4), the process returns to step B1, and step B1 and subsequent steps are repeatedly executed. If it is determined in step B4 that the predetermined time has elapsed (Yes in step B4), then step B5 is executed.

  In step B5, it is determined whether the current carrier frequency, that is, the value of the carrier frequency set last time (one time before the current time) is the maximum value. If the previous carrier frequency is the maximum value (Yes in Step B5), then Step B6 is executed. If the previous carrier frequency is not the maximum value (No in Step B5), then Step B8 is executed. .

In step B6, the carrier frequency command value (f _c ^* ) is set to 15 times the output frequency. Therefore, the value of the carrier frequency is set to a value that is 15 times the output frequency. Here, the carrier frequency magnification N with respect to the output frequency may be arbitrary, but is preferably set to 3n times (n is an odd number) in consideration of harmonics related to torque ripple and noise. Therefore, in step B6, the magnification is set to an odd multiple (5 times) of 3 (the same applies to steps B9 and B11 described later). When step B6 is executed, next step B7 is executed.

  In step B7, the control gain is changed as in step B3.

  In Step B8, it is determined whether or not the magnification N of the carrier frequency with respect to the output frequency is 15. When N is 15 (Yes at Step B8), Step B9 is executed next, and when N is not 15 (No at Step B8), Step B11 is executed next.

In step B9, the carrier frequency command value (f _c ^* ) is set to 9 times the output frequency. Therefore, the value of the carrier frequency is set to a value that is nine times the output frequency. In step B9, the carrier frequency magnification N with respect to the output frequency may be arbitrary, but is set to a value smaller than the magnification in step B6. In the second embodiment, similarly to step B6, the magnification is an odd multiple of 3 (three times). When step B9 is executed, next step B10 is executed.

  In step B10, the control gain is changed as in step B3.

In Step B11, the carrier frequency command value (f _c ^* ) is set to three times the output frequency. Therefore, the value of the carrier frequency is set to a value that is three times the output frequency. In step B11, the carrier frequency magnification N with respect to the output frequency may be arbitrary, but is set to a value smaller than the magnification in step B9. In the second embodiment, similarly to step B6, the magnification is an odd multiple (1) of 3. When step B11 is executed, next step B12 is executed.

  In step B11, the control gain is changed as in step B3.

  Note that when one of steps B3, B7, B10, and B12, that is, a change in control gain is executed, the process returns to step B1, and step B1 and subsequent steps are repeatedly executed.

  As described above, when the control deviation is smaller than the predetermined value, the value of the carrier frequency is changed stepwise (15 times, 9 times) according to the magnitude of the previous value by the processing operation of steps B4 to B12 in FIG. Therefore, switching shocks when changing the carrier frequency, for example, instantaneous but discontinuous speed fluctuations of the motor can be suppressed.

  FIG. 5 shows an example of the carrier frequency setting operation of the carrier frequency calculation unit 70 in the second embodiment. In this example, the motor control device 1 executes the processing operation shown in FIG. 4 at the time of valleys in the carrier signal (t0, t1, t2,... In FIG. 2).

  First, at time t0 in FIG. 5, the carrier frequency is set to 9 times the output frequency. After t0, the control deviation E increases, and at time t1, the control deviation E exceeds a predetermined value E0. For this reason, the carrier frequency is changed to the maximum value.

  The control deviation E decreases after the time t1, but at the time t2, the deviation E is less than the predetermined value E0 but exceeds the predetermined value E1 (<E0). For this reason, the carrier frequency is set to the maximum value without being changed.

  After time t2, the control deviation E decreases, and at time t3, the control deviation falls below a predetermined value E1. However, since the predetermined time T1 has not elapsed since the time t1 when the carrier frequency was changed, the carrier frequency is set to the maximum value without being changed.

  After time t3, the control deviation E decreases, and at time t4, the control deviation falls below the predetermined value E1. Further, at the time t4, since the predetermined time T1 has elapsed since the time t1 when the carrier frequency was changed, the carrier frequency is set to 15 times the output frequency.

  As shown in FIG. 5, when the control deviation E increases, a predetermined value E0 of the control deviation for determining whether to change the carrier frequency to the maximum value, and when the control deviation E decreases, the carrier frequency is an integer multiple of the output frequency. By setting a predetermined value En (one or more (n is a natural number): one (E1) in FIG. 5) of the control deviation for determining whether to change, the change of the carrier frequency is repeated in an unstable manner. Can be prevented.

  As described above, according to the second embodiment, as in the first embodiment, when the control deviation exceeds a predetermined value, the carrier frequency for PWM control is set to a predetermined maximum value, so that the control response performance is improved. To do. Also, when the control deviation is smaller than a predetermined value at the present time, the carrier frequency is set to a value that decreases stepwise according to the magnitude of the carrier frequency set at the previous time point, so the carrier frequency is changed. The switching shock at the time can be suppressed. Further, when the control deviation is smaller than a predetermined value at the present time, the carrier frequency is not changed unless the predetermined time has elapsed from the time when the carrier frequency is changed, so that the control operation is stabilized.

  In addition, this invention is not limited to embodiment mentioned above, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  For example, the motor drive system of the above-described embodiment is not limited to an electric vehicle, and may be mounted on various electric devices.

DESCRIPTION OF SYMBOLS 1 Motor control apparatus 10 Current command calculating part 20 dq axis current control part 30 Coordinate conversion part 40 PWM signal generation part 50 dq conversion part 60 Speed conversion part 70 Carrier frequency calculation part 100 Inverters 110a, 110b, 110c, 110d, 110e, 110f Switching element 200 Motor 210 Position sensor 220 Current sensor

Claims (7)

In the motor control device that controls the drive of the motor by the inverter,
A signal generator for generating a control signal to the inverter by pulse width modulation;
A carrier frequency calculation unit that sets a carrier frequency in the pulse width modulation according to a control deviation;
With
The carrier frequency calculation unit sets the carrier frequency to a maximum value allowed in the pulse width modulation of the inverter when the control deviation is greater than or equal to a predetermined value. The motor control device according to claim 1,
The carrier frequency calculation unit sets the carrier frequency to an integer multiple of an output frequency when the control deviation is smaller than the predetermined value. The motor control device according to claim 2,
When the control deviation is smaller than the predetermined value at the present time, the carrier frequency calculation unit sets the carrier frequency to a value that decreases stepwise according to the magnitude of the carrier frequency set at the previous time point. A motor control device. The motor control device according to claim 2,
When the control deviation is smaller than the predetermined value at the present time, the carrier frequency calculating unit does not change the carrier frequency unless the predetermined time has elapsed from the change of the carrier frequency to the current time. A motor control device. In the motor control device according to claim 1 or 2,
The carrier frequency calculating unit sets a control gain according to the carrier frequency to be set. The motor control device according to claim 5,
The carrier frequency calculation unit includes a limiter that limits a rate of change of the control gain. A motor,
An inverter that provides AC power to the motor;
A motor control device for controlling driving of the motor by the inverter;
In a motor drive system comprising:
The motor control device according to claim 1, wherein the motor control device is a motor control device according to claim 1.

Images