JP4604820B2 - Control device for motor drive system - Google Patents

Description

  The present invention relates to a motor drive system control device, and more particularly to a motor drive system control device that converts a DC voltage into an AC voltage by an inverter and supplies the AC voltage to an AC motor as a load.

  Generally, a motor drive system that converts a DC voltage into an AC voltage by an inverter and controls driving of a three-phase AC motor is used. In such a motor drive system, generally, in order to drive the motor with high efficiency, the motor current is controlled according to sine wave PWM (Pulse Width Modulation) control based on vector control.

  However, in a motor drive system in which the load is a permanent magnet motor, in particular, a motor composed of a ferrite magnet generally used as a permanent magnet, if the magnet temperature rises due to heat generated by energization of the motor, There was a problem that the output torque decreased. In order to cope with this point, a control device for a permanent magnet motor that suppresses torque fluctuation due to a change in magnet temperature has been proposed as a control configuration for correcting the current command value according to the magnet temperature by arranging the magnet temperature sensor (for example, Patent Document 1).

In addition to the general sine wave PWM, in addition to the general sine wave PWM, the rectangular wave drive control with the PWM duty fixed to the maximum value and the rectangular wave system and sine A configuration in which a motor drive system that further employs an “overmodulation PWM method” using an intermediate voltage waveform of a wave PWM method is applied to a hybrid vehicle is disclosed (Non-Patent Document 1). In this motor drive system, three control methods of sine wave PWM control, overmodulation PWM control, and rectangular wave control are appropriately switched and used according to motor operating conditions (typically, torque / rotation speed) (for example, Non-Patent Document 1).
JP-A-11-18496 “Toyota's motor control technology that balances ecology and power”, Nikkei Monozukuri August 2004 issue, p. 89-95

  However, in the motor control device disclosed in Patent Document 1, it is necessary to accurately detect the temperature of the permanent magnet mounted on the rotating body by arranging a magnet temperature sensor. For this reason, it is difficult to prevent torque fluctuation from the viewpoint of reliability of permanent magnet temperature detection.

  Further, as shown in Non-Patent Document 1, torque feedback control is performed during rectangular wave control, while motor current feedback control is performed for high-precision control during PWM control (sine wave PWM control / overmodulation PWM control). In the control configuration, there is a possibility that torque fluctuation depending on the magnet temperature may occur at the time of switching between the two control methods according to the change in the motor operation status, particularly when shifting from torque feedback control to motor current feedback control.

  The present invention has been made to solve such problems, and an object of the present invention is to combine a rectangular wave control system based on torque feedback control and a PWM control system based on motor current feedback control on motor operating conditions. In the control device of the motor drive device used by switching according to the above, it is to suppress the occurrence of torque fluctuation due to the magnet temperature change during the PWM control method.

  The motor drive system control apparatus according to the present invention controls a motor drive system including an inverter that converts a DC voltage into an AC voltage for driving an AC motor. The control device includes a current detection unit, a control method selection unit, a first motor control unit, and a second motor control unit. The current detection means detects the motor current supplied to the AC motor. The control method selection means selectively sets the voltage conversion control method in the inverter according to the operating condition of the AC motor. When the control method selection unit selects the first control method for applying a rectangular wave voltage to the AC motor, the first motor control unit is configured to output a phase of the rectangular wave voltage according to a torque deviation with respect to a torque command value in torque control. Torque control is performed by feedback control that adjusts. When the control method selection means selects the second control method for controlling the voltage applied to the AC motor in accordance with the pulse width modulation method based on vector control, torque control is performed by feedback control of the motor current. Further, the second motor control means includes torque estimation means, torque command correction means, current command generation means, and motor voltage control means. The torque estimating means estimates the output torque of the AC motor. The torque command correcting means corrects the torque command value according to the deviation between the torque command value in torque control and the estimated output torque by the torque estimating means. The current command generation means generates a motor current command value according to the torque command value corrected by the torque command correction means. The motor voltage control means converts the voltage applied by the inverter so that the voltage applied to the AC motor is controlled according to the deviation between the motor current command value by the current command generation means and the detected motor current value by the current detection means. To control.

According to the control device of the motor drive system, when the second control method (sine wave PWM control method / overmodulation control method) is selected, the same torque as when the first control method (rectangular wave control method) is selected. Feedback control of the motor current can be performed by adding feedback control according to the deviation. Therefore, since the motor current control can be performed so as to compensate for the change in the motor output characteristic depending on the temperature or the like, the occurrence of torque fluctuation can be prevented without providing a temperature sensor or the like. In addition, since feedback control according to the torque deviation is performed in both the first control method and the second control method, it is possible to prevent the occurrence of torque fluctuation when switching between these control methods.

  Preferably, the control device for a motor drive system according to the present invention further includes motor position detection means for detecting the rotation angle of the AC motor. In particular, the second motor control means further includes a rotation speed calculation means and a power calculation means. The rotation speed calculation means calculates the rotation speed of the AC motor based on the detection value of the motor position detection means. The power calculation means calculates the power supplied to the AC motor based on the product of the motor current detected by the current detection means and the voltage applied to the AC motor controlled by the motor voltage control means. Further, the torque estimating means calculates an estimated output torque based on the rotational speed of the AC motor calculated by the rotational speed calculating means and the power supplied to the AC motor calculated by the power calculating means.

  According to the control device for the motor drive system, a sensor other than the current detection means (current sensor) and the motor detection unit (rotation angle sensor: resolver) required for general motor control is not required. The output torque of the AC motor can be estimated.

  Preferably, in the motor drive system control device according to the present invention, the second control method includes a sinusoidal pulse width modulation method in which the modulation factor is in the range of 0 to 0.61, and a modulation factor of 0.61 to 0. And an overmodulated pulse width modulation method in which the fundamental wave component is distorted so as to be in the range of .78.

  According to the control device of the motor drive system, a general sinusoidal pulse width modulation (PWM) control method and overmodulation PWM control are performed in accordance with the operating conditions (typically, torque and rotation speed) of the AC motor. By switching between the method and the rectangular wave control method (first control method), it is possible to improve the output in the medium speed range and the high speed range of the AC motor.

  More preferably, in the control device for a motor drive system according to the present invention, the AC motor is a permanent magnet motor having a permanent magnet attached to the rotor.

  According to the control device for the motor drive system described above, in a configuration in which a permanent magnet motor suitable for miniaturization and high efficiency is used as a load, torque fluctuations are generated by compensating for changes in motor output characteristics depending on the permanent magnet temperature. Can be prevented.

  According to the control device for a motor drive device of the present invention, in a control configuration in which a rectangular wave control method based on torque feedback control and a PWM control method based on motor current feedback control are switched according to motor operating conditions, It is possible to suppress the occurrence of torque fluctuation due to the magnet temperature change at.

  Hereinafter, a detailed description will be given with reference to the description of the embodiment of the present invention. In the following, the same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated in principle.

FIG. 1 is an overall configuration diagram of a motor drive system according to an embodiment of the present invention.
Referring to FIG. 1, motor drive system 100 according to the embodiment of the present invention includes a DC voltage generation unit 10 #, a smoothing capacitor C0, an inverter 14, and an AC motor M1.

  AC motor M1 is, for example, a drive motor for generating torque for driving drive wheels of a hybrid vehicle or an electric vehicle. Alternatively, AC motor M1 may be configured to have a function of a generator driven by an engine, or may be configured to have both functions of an electric motor and a generator. Furthermore, AC motor M1 may operate as an electric motor for the engine, and may be incorporated in a hybrid vehicle so that the engine can be started, for example.

  DC voltage generation unit 10 # includes a DC power supply B, system relays SR1 and SR2, a smoothing capacitor C1, and a step-up / down converter 12.

  The DC power source B is composed of a secondary battery such as nickel metal hydride or lithium ion. The DC voltage Vb output from the DC power source B is detected by the voltage sensor 10. Voltage sensor 10 outputs detected DC voltage Vb to control device 30.

  System relay SR 1 is connected between the positive terminal of DC power supply B and power line 6, and system relay SR 1 is connected between the negative terminal of DC power supply B and ground line 5. System relays SR1 and SR2 are turned on / off by signal SE from control device 30. More specifically, system relays SR1 and SR2 are turned on by H (logic high) level signal SE from control device 30, and are turned off by L (logic low) level signal SE from control device 30. Smoothing capacitor C <b> 1 is connected between power line 6 and ground line 5.

  Buck-boost converter 12 includes a reactor L1, power semiconductor switching elements Q1, Q2, and diodes D1, D2.

  Power switching elements Q 1 and Q 2 are connected in series between power line 7 and ground line 5. On / off of power switching elements Q1 and Q2 is controlled by switching control signals S1 and S2 from control device 30.

  In the embodiment of the present invention, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, or a power bipolar transistor is used as a power semiconductor switching element (hereinafter simply referred to as “switching element”). Etc. can be used. Anti-parallel diodes D1, D2 are arranged for switching elements Q1, Q2.

  Reactor L1 is connected between a connection node of switching elements Q1 and Q2 and power line 6. Further, the smoothing capacitor C 0 is connected between the power line 7 and the ground line 5.

  Inverter 14 includes a U-phase arm 15, a V-phase arm 16, and a W-phase arm 17 provided in parallel between power line 7 and ground line 5. Each phase arm is composed of a switching element connected in series between the power line 7 and the ground line 5. For example, U-phase arm 15 includes switching elements Q3 and Q4, V-phase arm 16 includes switching elements Q5 and Q6, and W-phase arm 17 includes switching elements Q7 and Q8. Further, antiparallel diodes D3 to D8 are connected to switching elements Q3 to Q8, respectively. Switching elements Q3 to Q8 are turned on / off by switching control signals S3 to S8 from control device 30.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of AC motor M1. In other words, AC motor M1 is a three-phase permanent magnet motor, and is configured by commonly connecting one end of three coils of U, V, and W phases to a midpoint. Furthermore, the other end of each phase coil is connected to the midpoint of the switching elements of each phase arm 15-17.

  The step-up / step-down converter 12 inverts a DC voltage obtained by boosting the DC voltage Vb supplied from the DC power supply B (hereinafter, this DC voltage corresponding to the input voltage to the inverter 14 is also referred to as “system voltage”) during the boosting operation. 14 is supplied. More specifically, in response to switching control signals S1 and S2 from control device 30, an ON period of switching element Q1 and an ON period of Q2 are alternately provided, and the step-up ratio is equal to the ratio of these ON periods. It will be a response.

  Further, during the step-down operation, the step-up / down converter 12 steps down the DC voltage (system voltage) supplied from the inverter 14 via the smoothing capacitor C0 and charges the DC power source B. More specifically, in response to switching control signals S1 and S2 from control device 30, a period in which only switching element Q1 is turned on and a period in which both switching elements Q1 and Q2 are turned off are alternately provided, The step-down ratio is in accordance with the duty ratio during the ON period.

  Smoothing capacitor C0 smoothes the DC voltage from step-up / down converter 12, and supplies the smoothed DC voltage to inverter 14. The voltage sensor 13 detects the voltage across the smoothing capacitor C 0, that is, the system voltage, and outputs the detected value VH to the control device 30.

  When the torque command value of AC motor M1 is positive (Trqcom> 0), inverter 14 is switched in response to switching control signals S3 to S8 from control device 30 when a DC voltage is supplied from smoothing capacitor C0. The AC motor M1 is driven so as to convert a DC voltage into an AC voltage and output a positive torque by the switching operation of the elements Q3 to Q8. Further, when the torque command value of AC motor M1 is zero (Trqcom = 0), inverter 14 converts the DC voltage to the AC voltage by the switching operation in response to switching control signals S3 to S8, and the torque is zero. The AC motor M1 is driven so that Thus, AC motor M1 is driven to generate zero or positive torque designated by torque command value Trqcom.

  Further, during regenerative braking of a hybrid vehicle or electric vehicle equipped with motor drive system 100, torque command value Trqcom of AC motor M1 is set to be negative (Trqcom <0). In this case, the inverter 14 converts the AC voltage generated by the AC motor M1 into a DC voltage by a switching operation in response to the switching control signals S3 to S8, and converts the converted DC voltage (system voltage) to the smoothing capacitor C0. To the step-up / down converter 12. Note that regenerative braking here refers to braking with regenerative power generation when the driver driving a hybrid vehicle or electric vehicle performs foot braking, or turning off the accelerator pedal while driving, although the foot brake is not operated. This includes decelerating the vehicle (or stopping acceleration) while generating regenerative power.

  Current sensor 24 detects a motor current flowing through AC motor M <b> 1 and outputs the detected motor current to control device 30. Since the sum of instantaneous values of the three-phase currents iu, iv, and iw is zero, the current sensor 24 has a motor current for two phases (for example, a V-phase current iv and a W-phase current iw) as shown in FIG. It is sufficient to arrange it so as to detect.

  The rotation angle sensor (resolver) 25 detects the rotor rotation angle θ of the AC motor M1, and sends the detected rotation angle θ to the control device 30. The control device 30 calculates the rotational speed (rotational speed) of the AC motor M1 based on the rotational angle θ.

  The control device 30 includes a torque command value Trqcom input from an electronic control unit (ECU) provided outside, a battery voltage Vb detected by the voltage sensor 10, a system voltage VH detected by the voltage sensor 13, and a current sensor 24. Based on the motor currents iv and iw from the rotation angle sensor 25 and the rotation angle θ from the rotation angle sensor 25, the step-up / down converter 12 and the inverter 14 so that the AC motor M1 outputs torque according to the torque command value Trqcom by a method described later. To control the operation. That is, the switching control signals S1 to S8 for controlling the buck-boost converter 12 and the inverter 14 as described above are generated and output to the buck-boost converter 12 and the inverter 14.

  During the step-up operation of the step-up / down converter 12, the control device 30 feedback-controls the output voltage VH of the smoothing capacitor C0, and generates the switching control signals S1 and S2 so that the output voltage VH becomes a voltage command value.

  Further, when receiving a signal RGE indicating that the hybrid vehicle or the electric vehicle has entered the regenerative braking mode from the external ECU, the control device 30 performs switching control so as to convert the AC voltage generated by the AC motor M1 into a DC voltage. Signals S3 to S8 are generated and output to inverter 14. Thereby, the inverter 14 converts the AC voltage generated by the AC motor M <b> 1 into a DC voltage and supplies it to the step-up / down converter 12.

  Further, when receiving a signal RGE indicating that the hybrid vehicle or the electric vehicle has entered the regenerative braking mode from the external ECU, the control device 30 switches the switching control signals S1, S2 so as to step down the DC voltage supplied from the inverter 14. Is output to the step-up / down converter 12. As a result, the AC voltage generated by AC motor M1 is converted into a DC voltage, stepped down, and supplied to DC power supply B.

  Furthermore, control device 30 generates signal SE for turning on / off system relays SR1, SR2 and outputs the signal SE to system relays SR1, SR2.

  Next, power conversion in the inverter 14 controlled by the control device 30 will be described in detail.

  As shown in FIG. 2, in motor drive system 100 according to the embodiment of the present invention, three control methods are switched and used for power conversion in inverter 14.

  The sine wave PWM control method is used as a general PWM control, and the switching element in each phase arm is turned on / off by comparing the voltage between a sine wave voltage command value and a carrier wave (typically a triangular wave). Control according to. As a result, for a set of a high level period corresponding to the on period of the upper arm element and a low level period corresponding to the on period of the lower arm element, the duty is set so that the fundamental wave component becomes a sine wave within a certain period. The ratio is controlled. As is well known, in the sine wave PWM control system, the fundamental wave component amplitude can be increased only up to 0.61 times the inverter input voltage.

  On the other hand, in the rectangular wave control method, an AC motor is applied to one pulse of a rectangular wave whose ratio between the high level period and the low level period is 1: 1 within the predetermined period. As a result, the modulation rate is increased to 0.78.

  The overmodulation PWM control system performs the same PWM control as the sine wave PWM control system after distorting the carrier wave to reduce the amplitude. As a result, the fundamental wave component can be distorted, and the modulation factor can be increased to a range of 0.61 to 0.78.

  In AC motor M1, when the number of rotations and output torque increase, the induced voltage increases and the required voltage increases. The boosted voltage by the converter 12, that is, the system voltage VH needs to be set higher than this motor required voltage (induced voltage). On the other hand, there is a limit value (VH maximum voltage) in the boosted voltage by the converter 12, that is, the system voltage.

  Therefore, in the region where the required motor voltage (induced voltage) is lower than the maximum value of the system voltage (VH maximum voltage), the maximum torque control by the sine wave PWM control method or the overmodulation PWM control method is applied and the vector control is followed. The output torque is controlled to the torque command value Trqcom by the motor current control.

  On the other hand, when the required motor voltage (induced voltage) reaches the maximum value of the system voltage (VH maximum voltage), a rectangular wave control method according to field weakening control is applied while maintaining the system voltage VH. In the rectangular wave control method, since the amplitude of the fundamental wave component is fixed, torque control is executed by voltage phase control of the rectangular wave pulse based on the deviation between the actual torque value obtained by power calculation and the torque command value.

  As shown in the flowchart of FIG. 3, the control device 30 receives the torque command value Trqcom of the AC motor M1 calculated from the vehicle request output based on the accelerator opening etc. by an ECU (not shown) (step S100). Based on the preset map or the like, the required motor voltage (induced voltage) is calculated from the torque command value Trqcom and the rotational speed of AC motor M1 (step S110), and further, the maximum motor required voltage and system voltage ( In accordance with the relationship with the VH maximum voltage), it is determined which of the field-weakening control (rectangular wave control method) and the maximum torque control (sine wave PWM control method / overmodulation PWM control method) is to be applied (step) S120). Whether to use the sine wave PWM control method or the overmodulation PWM control method when applying the maximum torque control is determined according to the modulation rate range of the voltage command value according to the vector control. According to the control flow, an appropriate control method is selected from the plurality of control methods shown in FIG. 2 according to the operating condition of AC motor M1.

  As a result, as shown in FIG. 4, the sine wave PWM control method is used to reduce the torque fluctuation in the low rotational speed range A1, and the overmodulation PWM control method and the high rotational speed range A3 are used in the middle rotational speed range A2. Then, a rectangular wave control method is applied. In particular, the output of AC motor M1 is improved by applying the overmodulation PWM control method and the rectangular wave control method. As described above, which one of the control methods shown in FIG. 2 is used is determined within the range of the realizable modulation rate.

  FIG. 5 is a control block diagram of the sine wave PWM control method and the overmodulation PWM control method executed by the control device 30.

  As shown in FIG. 5, the PWM control block 200 includes a current command value generation unit 210, coordinate conversion units 220 and 250, a rotation speed calculation unit 230, PI calculation units 240d and 240q, and a PWM signal generation unit 260. A control mode determination unit 270, a power calculation unit 300, a torque estimation unit 310, and a torque command correction unit 320.

  Current command value generation unit 210 generates a d-axis current command value Idcom and a q-axis current command value Iqcom according to torque command value Trqcom # from torque command correction unit 320 according to a table or the like created in advance.

  The coordinate conversion unit 220 performs a V-phase current iv and a W-phase current detected by the current sensor 24 by coordinate conversion (3 phase → 2 phase) using the rotation angle θ of the AC motor M1 detected by the rotation angle sensor 25. Based on iv, the d-axis current id and the q-axis current iq are calculated. The rotation speed calculation unit 230 calculates the rotation speed Nmt of the AC motor M1 based on the output from the rotation angle sensor 25.

  Deviation ΔId (ΔId = Idcom-id) with respect to the command value of the d-axis current is input to the PI calculation unit 240d, and deviation ΔIq (ΔIq = Iqcom-iq) with respect to the command value of the q-axis current is input to the PI calculation unit 240q. Is entered. The PI calculation unit 240d performs a PI calculation with a predetermined gain on the d-axis current deviation ΔId to obtain a control deviation, and generates a d-axis voltage command value Vd # according to the control deviation. PI calculation unit 240q performs PI calculation with a predetermined gain on q-axis current deviation ΔIq to obtain a control deviation, and generates q-axis voltage command value Vq # according to the control deviation.

  The coordinate conversion unit 250 converts the d-axis voltage command value Vd # and the q-axis voltage command value Vq # into the U-phase, V-phase, W-phase by coordinate conversion (2 phase → 3 phase) using the rotation angle θ of the AC motor M1. Each phase voltage command value Vu, Vv, Vw of the phase is converted. The system voltage VH is also reflected in the conversion from the d-axis and q-axis voltage command values Vd # and Vq # to the phase voltage command values Vu, Vv and Vw.

  When the maximum torque control (sine wave PWM control method / overmodulation PWM control method) is selected according to the flowchart shown in FIG. 3, the control mode determination unit 270 performs the sine wave PWM control method according to the following modulation factor calculation. One of the overmodulation PWM control methods is selected.

  Control mode determination unit 270 uses line d voltage command value Vd # and q axis voltage command value Vq # generated by PI operation unit 240 to calculate line voltage amplitude Vamp according to the following equations (1) and (2). calculate.

Vamp = | Vd # | .cosφ + | Vq # | .sinφ (1)
tan φ = Vq # / Vd # (2)
Further, the control mode determination unit 270 calculates the modulation factor Kmd, which is the ratio of the line voltage amplitude Vamp by the above calculation to the system voltage VH, that is, according to the following equation (3).

Kmd = Vamp / VH # (3)
The control mode determination unit 270 selects one of the sine wave PWM control method and the overmodulation PWM control method according to the modulation factor Kmd obtained by the above calculation. As mentioned above,
The selection of the control method by the control mode determination unit 270 is reflected in the carrier wave switching in the PWM signal generation unit 260. That is, in the overmodulation PWM control method, the carrier wave used in the PWM modulation in the PWM signal generation unit 260 is switched from the general one in the sine wave PWM control method.

  The PWM signal generation unit 260 generates the switching control signals S3 to S8 shown in FIG. 1 based on the comparison between the voltage command values Vu, Vv, Vw in each phase and a predetermined carrier wave. The inverter 14 is subjected to switching control according to the switching control signals S3 to S8 generated by the PWM control block 200, so that torque according to the torque command value Trqcom # input to the current command value generation unit 210 is output. An alternating voltage is applied.

  As described above, the current command value generation unit 210, the coordinate conversion units 220 and 250, the rotation speed calculation unit 230, the PI calculation unit 240, and the PWM signal generation unit 260 allow the current command value (Idcom) corresponding to the torque command value Trqcom # to be set. , Iqcom) to form a closed loop for controlling the motor current.

  Furthermore, in the motor drive system control apparatus according to the present embodiment, the torque (power) feedback control loop configured by the power calculation unit 300, the torque estimation unit 310, and the torque command correction unit 320 is replaced with the motor current feedback control loop. Added.

  The power calculation unit 300 uses the phase currents obtained from the V-phase current iv and the W-phase current iw obtained by the current sensor 24 and the voltages Vu, Vv, and Vw (U-phase, V-phase, and W-phase) as follows ( 4) Motor supply power Pmt is calculated according to the equation.

Pmt = iu · Vu + iv · Vv + iw · Vw (4)
Torque estimation unit 310 uses angular velocity ω calculated from motor supply power Pmt obtained by power calculation unit 300 and rotation angle θ of AC motor M1 detected by rotation angle sensor 25, according to the following equation (5). A torque estimated value Trq is calculated.

Trq = Pmt / ω (5)
Torque command correction unit 320 includes addition points 322 and 324 and a PI calculation unit 325. The addition point 432 obtains a torque deviation ΔTrq (ΔTrq = Trqcom−Trq) between the original torque command value Trqcom and the estimated torque value Trq of AC motor M1. The PI calculation unit 325 performs a PI calculation with a predetermined gain on the torque deviation ΔTrq to obtain a control deviation. The torque command value Trqcom # corrected by the torque feedback control in the torque command correction unit 320 is obtained by subtracting the control deviation obtained by the PI calculation unit 325 from the original torque command value Trqcom at the addition point 324 as the torque correction amount ΔTrqc. Is obtained.

  As described above, torque command value Trqcom # corrected by torque command correction unit 320 is input to current command value generation unit 210. Therefore, d-axis current command value Idcom generated by current command value generation unit 210 and The q-axis current command value Iqcom reflects the deviation between the original torque command value Trqcom and the estimated torque value Trq based on power calculation.

  Therefore, the current command value in the motor current control can be generated so as to compensate for the change in the motor output characteristic depending on the magnet temperature. As a result, it is possible to prevent the occurrence of torque fluctuation depending on the magnet temperature during PWM control based on motor current control.

  Next, a control block diagram in the rectangular wave control method will be described with reference to FIG. As described above, in the rectangular wave control method, the modulation rate is fixed, and thus the modulation rate control as shown in FIG. 6 is not configured.

  Referring to FIG. 6, rectangular wave control block 400 includes a power calculation unit 410, a torque calculation unit 420, a PI calculation unit 430, a rectangular wave generator 440, and a signal generation unit 450.

  Similarly to the power calculation unit 300 in FIG. 5, the power calculation unit 410 includes each phase current obtained from the V-phase current iv and the W-phase current iw by the current sensor 24 and each phase (U phase, V phase, W phase). The motor supply power Pmt is calculated from the voltages Vu, Vv, and Vw according to the above equation (4).

  Similar to the torque estimation unit 310 in FIG. 5, the torque calculation unit 420 is calculated from the motor supply power Pmt obtained by the power calculation unit 410 and the rotation angle θ of the AC motor M1 detected by the rotation angle sensor 25. Using ω, a torque estimation value Trq is calculated according to the above equation (5).

  Torque deviation ΔTrq (ΔTrq = Trqcom−Trq) with respect to torque command value Trqcom is input to PI calculation unit 430. PI calculation unit 430 performs PI calculation with a predetermined gain on torque deviation ΔTrq to obtain a control deviation, and sets phase φv of the rectangular wave voltage according to the obtained control deviation. Specifically, when positive torque is generated (Trqcom> 0), the voltage phase is advanced when torque is insufficient, while when the torque is excessive, the voltage phase is delayed, and when negative torque is generated (Trqcom <0), the voltage phase is increased when torque is insufficient While delaying, the voltage phase is advanced when the torque is excessive.

  The rectangular wave generator 440 generates each phase voltage command value (rectangular wave pulse) Vu, Vv, Vw according to the voltage phase φv set by the PI calculation unit 430. The signal generator 450 generates switching control signals S3 to S8 according to the phase voltage command values Vu, Vv, and Vw. When inverter 14 performs a switching operation according to switching control signals S3 to S8, a rectangular wave pulse according to voltage phase φv is applied as each phase voltage of the motor.

  Thus, in the rectangular wave control method, the motor torque control can be performed by the feedback control of the torque (electric power). However, since the operation amount of the motor applied voltage is only the phase in the rectangular wave control method, the control responsiveness is lowered as compared with the PWM control method in which the amplitude and phase of the motor applied voltage can be the operation amount.

  As understood from the comparison between FIG. 5 and FIG. 6, the torque (power) feedback control loop constituted by the power calculation unit 300, the torque estimation unit 310, and the torque command correction unit 320 in the PWM control block (FIG. 5) is The same torque calculation as that of the rectangular wave control block 400 is performed. As a result, it is possible to prevent the occurrence of torque fluctuation at the time of switching between the PWM control method (sine wave PWM control / overmodulation control method) and the rectangular wave control method.

  The correspondence relationship between the configuration shown in FIGS. 1 to 6 and the configuration of the present invention will be described. The current sensor 24 and the rotation angle sensor 25 are respectively included in the “current detection unit” and the “motor position detection unit” of the present invention. Correspondingly, the functional part that executes the flowchart shown in FIG. 3 corresponds to the “control method selection means” of the present invention. 5 corresponds to the “first motor control unit” of the present invention, and the rectangular wave control block 400 of FIG. 6 corresponds to the “second motor control unit” of the present invention. Further, in the configuration of FIG. 4, a set of coordinate conversion units 220 and 250, PI calculation units 240d and 240q, and a PWM signal generation unit 260 corresponds to “motor voltage control means” of the present invention.

  In the present embodiment, as a preferred configuration example, DC voltage generation unit 10 # of the motor drive system includes buck-boost converter 12 so that the input voltage (system voltage VH) to inverter 14 can be variably controlled. showed that. However, in the application of the present invention, it is not essential that the inverter input voltage is variable, and even for a configuration in which the input voltage to the inverter 14 is fixed (for example, a configuration in which the step-up / down converter 12 is omitted). The present invention can be applied. That is, the present invention does not particularly limit the configuration on the input side to the inverter, and in an inverter that converts a DC voltage into an AC voltage applied to an AC motor, a rectangular wave control method based on torque feedback control and a motor current feedback The present invention can be commonly applied to various motor drive devices that are used by switching the PWM control method based on the control according to the motor operating conditions.

  Furthermore, in the present embodiment, a permanent magnet motor is illustrated as an AC motor serving as a load of the motor drive system, where torque fluctuation depending on the magnet temperature is likely to be a problem. However, the application of the present invention is limited to such a case. It is not something. That is, as long as an AC motor whose motor output characteristics change depending on changes in temperature or the like is used as a load, it is possible to prevent occurrence of torque fluctuation by applying the present invention.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is an overall configuration diagram of a motor drive system according to an embodiment of the present invention. It is a figure explaining the control system used with the motor drive system according to the embodiment of the present invention. It is a flowchart explaining the selection method of a control system. It is a figure explaining the switching of the control system corresponding to a motor condition. It is a control block diagram in a sine wave PWM control system and an overmodulation PWM control system. It is a control block diagram at the time of a rectangular wave control system.

Explanation of symbols

  5 ground wire, 6, 7 power line, 10 # DC voltage generator, 10, 13 voltage sensor, 12 converter (buck-boost converter), 14 inverter, 15-17 each phase arm (U phase, V phase, W phase), 24 current sensor, 25 rotation angle sensor, 30 control device, 100 motor drive system, 200 PWM control block, 210 current command value generation unit, 220 coordinate conversion unit (3 phase → 2 phase), 230 rotation speed calculation unit, 240 PI Calculation unit, 250 coordinate conversion unit (2 phase → 3 phase), 260 PWM signal generation unit, 270 control mode determination unit, 300 power calculation unit, 310 torque estimation unit, 320 torque command correction unit, 322, 324 addition point, 325 PI calculation unit, 400 rectangular wave control block, 410 power calculation unit, 420 torque calculation unit, 430 PI calculation unit, 432 Addition point, 440 square wave generator, 450 signal generator, A1 low rotation speed range, A2 medium rotation speed range, A3 high rotation speed range, B DC power supply, C0, C1 smoothing capacitor, D1-D8 anti-parallel diode, id d-axis current, Idcom d-axis current command value, iq q-axis current, Iqcom q-axis current command value, iu, iv, iw Motor current (U phase, V phase, W phase), L1 reactor, M1 AC motor, Nmt motor Rotational speed, Pmt motor supply power, Q1-Q8 power semiconductor switching element, S1-S8 switching control signal, SR1, SR2 system relay, Trq torque estimated value, Trqcom torque command value (original value), Trqcom # torque command value ( Correction value), Trqc torque correction amount, Vb DC voltage (battery voltage), Vdd d-axis voltage command value, V H System voltage (inverter input voltage), Vq # q-axis voltage command value, Vu, Vv, Vw Phase voltage command values (U-phase, V-phase, W-phase), ΔId d-axis current deviation, ΔIq q-axis current deviation, ΔTrq Torque deviation, θ rotor rotation angle, φv voltage phase (rectangular wave voltage).

Claims (4)

A motor drive system control device comprising an inverter for converting a DC voltage into an AC voltage for driving an AC motor,
Current detection means for detecting a motor current supplied to the AC motor;
Depending on the operating conditions of said AC motor, a control mode selection means for selectively setting a control method of put that voltage conversion in said inverter,
When the control method selection unit selects the first control method for applying a rectangular wave voltage to the AC motor, the control method selection unit executes an estimation calculation of the output torque of the AC motor, and also calculates a torque command value and the estimated output torque. First motor control means for performing torque control by feedback control for adjusting the phase of the rectangular wave voltage according to the torque deviation of
A second motor that performs torque control by feedback control of the motor current when the control method selection means selects a second control method for controlling the voltage applied to the AC motor according to a pulse width modulation method by vector control Control means,
The second motor control means includes
Torque estimation means for estimating the output torque of the AC motor by an estimation calculation common to the estimation of the output torque by the first motor control means ;
Torque command correcting means for correcting the torque command value according to a deviation between a torque command value in the torque control and an estimated output torque by the torque estimating means;
Current command generating means for generating a motor current command value according to the torque command value corrected by the torque command correcting means;
Voltage conversion in the inverter so that an applied voltage to the AC motor is controlled in accordance with a deviation between the motor current command value by the current command generation unit and a detection value of the motor current by the current detection unit. And a motor voltage control means for controlling the motor. A motor position detecting means for detecting a rotation angle of the AC motor;
The second motor control means includes
A rotational speed calculation means for calculating the rotational speed of the AC motor based on a detection value of the motor position detection means;
Power calculating means for calculating power supplied to the AC motor based on the product of the motor current detected by the current detecting means and the voltage applied to the AC motor controlled by the motor voltage control means; Further including
The torque estimation means calculates the estimated output torque based on the rotation speed of the AC motor calculated by the rotation speed calculation means and the power supplied to the AC motor calculated by the power calculation means. The control device for a motor drive system according to claim 1. The second control method, the sinusoidal pulse width modulation scheme modulation rate is in the range of 0 to 0.61, the modulation rate is the fundamental wave component to be in the range of 0.61 to 0.78 The motor drive system control device according to claim 1, comprising a distorted overmodulation pulse width modulation method.   The control device for a motor drive system according to any one of claims 1 to 3, wherein the AC motor is a permanent magnet motor having a permanent magnet attached to a rotor.

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