JP2010166707A - Controller of ac motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of an AC motor capable of suppressing a delay in switching from square wave voltage control to PWM control. <P>SOLUTION: A control mode switching part 490 uses a current phase calculated from a predetermined switching determination torque for determining switching from square wave voltage control by a square wave voltage control part 400 to PWM control by a PWM control part 280, to switch from square wave voltage control to pulse width modulation control. Here, the control mode switching part 490 uses torque command value Trqcom as a switching determination torque when the absolute value of torque deviation ΔTrq from the torque command value Trqcom is equal to or less than a predetermined value, but uses a value available by adding a predetermined value to the torque command value Trqcom as the switching determination torque if the absolute value of the torque deviation ΔTrq is larger than a predetermined value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an AC motor control device, and more particularly, to an AC motor control device to which pulse width modulation (PWM) control and rectangular wave voltage control are applied.

  Japanese Patent Laying-Open No. 2005-51894 discloses a load driving device that controls an inverter so as to drive a motor generator in any one of a PWM control mode, an overmodulation control mode, and a rectangular wave control mode (Patent Document 1). reference).

  The PWM control mode in the above publication is a mode for controlling the inverter according to the sine wave PWM system, and the overmodulation control mode in the above publication is an overmodulation PWM system in which the amplitude of the fundamental wave component is larger than that in the sine wave PWM system. In this mode, the inverter is controlled. Hereinafter, the mode for controlling the inverter according to the sine wave PWM method is referred to as a sine wave PWM control mode, and the mode for controlling the inverter according to the overmodulation PWM method is referred to as an overmodulation PWM control mode. Are collectively referred to as a PWM control mode. The rectangular wave control mode (hereinafter referred to as “rectangular wave voltage control mode”) is a mode in which torque is controlled by controlling the phase of the rectangular wave voltage applied to the AC motor, and is an overmodulation PWM method. The amplitude of the fundamental wave component can be further increased.

JP 2005-51894 A

  When the determination from the rectangular wave voltage control to the PWM control is performed based on the current phase, if the torque deviation with respect to the torque command value (that is, the follow-up delay with respect to the torque command value) is large, the switching delay from the rectangular wave voltage control to the PWM control is large. There is a problem that current increases and current is disturbed.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide a control device for an AC motor capable of suppressing a switching delay from rectangular wave voltage control to PWM control.

  According to this invention, the control device for an AC motor is a control device for an AC motor driven by an inverter, and includes a pulse width modulation control unit, a rectangular wave voltage control unit, and a control mode switching unit. The pulse width modulation control unit generates an inverter control command in accordance with the pulse width modulation method. The rectangular wave voltage control unit generates an inverter control command so as to apply to the AC motor a rectangular wave voltage that is phase-controlled so as to operate the AC motor according to the torque command value. The control mode switching unit uses a current phase calculated from a predetermined switching determination torque to determine whether to switch from rectangular wave voltage control by the rectangular wave voltage control unit to pulse width modulation control by the pulse width modulation control unit. Switching from control to pulse width modulation control. Here, the control mode switching unit uses the torque command value as the switching determination torque when the absolute value of the torque deviation with respect to the torque command value is equal to or smaller than the predetermined value, and when the absolute value of the torque deviation is larger than the predetermined value, A value obtained by adding a predetermined value to the value is used as the switching determination torque.

  Preferably, the predetermined value is variably set according to at least one of the rotational speed of the AC motor, the system voltage applied to the inverter, and the torque of the AC motor.

  Preferably, the control mode switching unit uses a filter value obtained by subjecting the torque command value to delay filter processing as the torque command value used for setting the switching determination torque.

  Preferably, the pulse width modulation control unit includes a sine wave pulse width modulation control unit and a pulse width overmodulation control unit. The sine wave pulse width modulation control unit generates an inverter control command in accordance with the sine wave pulse width modulation method. The pulse width overmodulation control unit generates a control command for the inverter according to a pulse width overmodulation method in which the amplitude of the fundamental wave component is larger than that of the sine wave pulse width modulation method. Then, the control mode switching unit switches from the rectangular wave voltage control to the pulse width overmodulation control by the pulse width overmodulation control unit using the current phase calculated from the switching determination torque.

  In this AC motor control device, when the absolute value of the torque deviation with respect to the torque command value is larger than the predetermined value, a value obtained by adding the predetermined value to the torque command value is used as the switching determination torque. The deviation from the torque is suppressed. Therefore, according to this AC motor control device, it is possible to suppress a delay in switching from rectangular wave voltage control to PWM control.

1 is an overall configuration diagram of a motor drive control system to which an AC motor control device according to Embodiment 1 of the present invention is applied. It is a figure explaining the control mode of the AC motor in the motor drive control system shown in FIG. It is a figure explaining the correspondence of the operation state of an AC motor, and the control mode shown in FIG. FIG. 2 is a functional block diagram functionally illustrating the configuration of the control device shown in FIG. 1. FIG. 5 is a functional block diagram functionally illustrating a detailed configuration of a sine wave PWM control unit illustrated in FIG. 4. FIG. 5 is a functional block diagram functionally illustrating a detailed configuration of an overmodulation PWM control unit illustrated in FIG. 4. FIG. 5 is a functional block diagram functionally illustrating a detailed configuration of a rectangular wave voltage control unit illustrated in FIG. 4. It is a figure which shows the delay of the actual torque with respect to a torque command value. It is a 1st figure explaining the switching delay from rectangular wave voltage control to PWM control (overmodulation PWM control). It is a 2nd figure explaining the switching delay from rectangular wave voltage control to PWM control (overmodulation PWM control). It is a figure explaining the switching determination torque used for switching determination from rectangular wave voltage control to PWM control (overmodulation PWM control). It is the figure which showed that the switching delay from rectangular wave voltage control to PWM control (overmodulation PWM control) was suppressed. FIG. 5 is a functional block diagram of a portion related to switching from rectangular wave voltage control to PWM control (overmodulation PWM control) in the control mode switching unit shown in FIG. 4. 3 is a flowchart showing a switching procedure from rectangular wave voltage control to PWM control (overmodulation PWM control) by the control device shown in FIG. 1. It is a figure which shows an example of the relationship between the rotation speed of an AC motor, and the upper limit used for the setting of switching determination torque. It is a figure which shows an example of the relationship between a system voltage and the upper limit used for the setting of switching determination torque. It is a figure which shows an example of the relationship between a torque command value and the upper limit used for the setting of switching determination torque. It is a figure explaining the switching determination torque in Embodiment 2. FIG. It is the figure which showed that the switching delay from rectangular wave voltage control to PWM control (overmodulation PWM control) was suppressed. 10 is a flowchart illustrating a switching procedure from rectangular wave voltage control to PWM control (overmodulation PWM control) by the control device according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
(overall structure)
1 is an overall configuration diagram of a motor drive control system to which an AC motor control apparatus according to Embodiment 1 of the present invention is applied. Referring to FIG. 1, motor drive control system 100 includes a DC voltage generation unit 10 #, a smoothing capacitor C0, an inverter 14, an AC motor M1, and a control device 30.

  AC electric motor M1 is an electric motor that generates torque for driving the driving wheels of an electric vehicle (such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle). is there. Alternatively, AC electric 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. Further, AC electric motor M1 may operate as an electric motor for the engine, and may be incorporated in a hybrid vehicle as one that can start the engine, for example.

  DC voltage generation unit 10 # includes a power storage device B, system relays SR1 and SR2, a smoothing capacitor C1, and a converter 12. The power storage device B is typically configured by a secondary battery such as nickel metal hydride or lithium ion, an electric double layer capacitor, or the like. Voltage Vb of power storage device B and current Ib input / output to power storage device B are detected by voltage sensor 10 and current sensor 11, respectively. System relay SR1 is connected between the positive terminal of power storage device B and power line 6, and system relay SR2 is connected between the negative terminal of power storage device B and power line 5. System relays SR1 and SR2 are turned on / off by signal SE from control device 30.

  Converter 12 includes a reactor L1, power semiconductor switching elements Q1, Q2, and diodes D1, D2. Power semiconductor switching elements Q <b> 1 and Q <b> 2 are connected in series between power line 7 and power line 5. On / off of power semiconductor switching elements Q1, Q2 is controlled by switching control signals S1, S2 from control device 30.

  As a power semiconductor switching element (hereinafter simply referred to as “switching element”), an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, a power bipolar transistor, or the like can be used. . Diodes D1 and D2 are connected in antiparallel to switching elements Q1 and Q2, respectively. Reactor L1 is connected between a connection node of switching elements Q1, Q2 and power line 6. Smoothing capacitor C 0 is connected between power line 7 and power line 5.

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

  The AC motor M1 is typically a three-phase permanent magnet type synchronous motor, and is configured by connecting one end of three U, V, and W phase coils to a neutral point. And the other end of each phase coil is connected to the midpoint of the switching element of each phase upper and lower arms 15-17.

  Converter 12 is basically controlled so that switching elements Q1, Q2 are turned on and off in a complementary manner in each switching period. During the boosting operation, converter 12 boosts voltage Vb supplied from power storage device B to voltage VH (this DC voltage corresponding to the input voltage to inverter 14 is also referred to as “system voltage” hereinafter). This boosting operation is performed by supplying electromagnetic energy accumulated in reactor L1 to switching line Q1 to power line 7 via switching element Q1 and diode D1.

  Converter 12 steps down voltage VH to voltage Vb during the step-down operation. This step-down operation is performed by supplying electromagnetic energy accumulated in reactor L1 to switching line Q1 to power line 6 via switching element Q2 and diode D2. The voltage conversion ratio (ratio of VH and Vb) in these step-up or step-down operations is controlled by the on-period ratio (duty ratio) of the switching elements Q1 and Q2 with respect to the switching period. Note that VH = Vb (voltage conversion ratio = 1.0) can be obtained by fixing the switching elements Q1, Q2 to ON and OFF, respectively.

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

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

  Further, during regenerative braking of an electric vehicle equipped with motor drive control system 100, the torque command value of AC electric motor M1 is set to be negative (Trqcom <0). In this case, inverter 14 converts the AC voltage generated by AC motor M <b> 1 into a DC voltage by a switching operation in response to switching control signals S <b> 3 to S <b> 8, and supplies the converted DC voltage to converter 12. The regenerative braking here refers to braking with regenerative power generation when the driver operating the electric vehicle performs a footbrake operation, or regenerative braking by turning off the accelerator pedal while driving, although the footbrake is not operated. This includes decelerating (or stopping acceleration) the vehicle while generating electricity.

  Current sensor 24 detects the motor current flowing through AC electric motor M <b> 1 and outputs the detected value to control device 30. Since the sum of instantaneous values of the three-phase currents iu, iv, iw is zero, the current sensor 24 is arranged to detect motor currents for two phases (eg, V-phase current iv and W-phase current iw). All you need is enough.

  The rotation angle sensor (resolver) 25 detects the rotation angle θ of the rotor of the AC motor M1, and outputs the detected value to the control device 30. Control device 30 can calculate the rotational speed (rotational speed) and angular speed ω (rad / s) of AC electric motor M1 based on rotational angle θ. The rotation angle sensor 25 may be omitted by directly calculating the rotation angle θ from the motor voltage or current by the control device 30.

  The control device 30 is constituted by an electronic control unit (ECU (Electronic Control Unit)), and performs motor processing through software processing by executing a program stored in advance by a CPU (not shown) and / or hardware processing by a dedicated electronic circuit. The operation of the drive control system 100 is controlled.

  As representative functions, the control device 30 includes a torque command value Trqcom, a voltage Vb detected by the voltage sensor 10, a current Ib detected by the current sensor 11, a system voltage VH detected by the voltage sensor 13, and a current sensor. Converter 12 and inverter so that AC motor M1 outputs torque according to torque command value Trqcom by a control method described later based on motor currents iv, iw from rotation angle 24, rotation angle θ from rotation angle sensor 25, and the like. 14 operations are controlled. That is, control device 30 generates switching control signals S <b> 1 to S <b> 8 for controlling converter 12 and inverter 14 and outputs them to converter 12 and inverter 14.

Next, control of AC electric motor M1 by control device 30 will be described in more detail.
(Description of control mode)
FIG. 2 is a diagram illustrating a control mode of AC electric motor M1 in motor drive control system 100 shown in FIG. Referring to FIG. 2, in motor drive control system 100, three control modes are switched and used for control of AC electric motor M1, that is, power conversion in inverter 14.

  In the sine wave PWM control, on / off of the upper and lower arm elements of each phase is controlled in accordance with a voltage comparison between a sine wave voltage command and a carrier wave (typically a triangular wave). 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. Is controlled. In this sine wave PWM control in which the amplitude of the sinusoidal voltage command is limited to a range below the carrier wave amplitude, the fundamental wave component of the voltage applied to AC motor M1 (hereinafter also simply referred to as “motor applied voltage”). Can only be increased to about 0.61 times the input voltage. Hereinafter, the ratio of the fundamental component (effective value) of the motor applied voltage (line voltage) to the input voltage of the inverter 14 (that is, the system voltage VH) is referred to as “modulation rate”.

  The overmodulation PWM control performs PWM control similar to the sine wave PWM control in a range where the amplitude of the voltage command (sine wave component) is larger than the carrier wave amplitude. In particular, the fundamental wave component can be increased by distorting the voltage command from the original sine wave waveform (amplitude correction), and the modulation rate is increased from the maximum modulation rate in the sine wave PWM control mode to a range of 0.78. Can do. In the overmodulation PWM control, since the amplitude of the voltage command (sine wave component) is larger than the carrier wave amplitude, the line voltage applied to the AC motor M1 is not a sine wave but a distorted voltage.

  On the other hand, in the rectangular wave voltage control, one pulse of a rectangular wave with a ratio of 1: 1 between the high level period and the low level period is applied to the AC motor within the predetermined period. Thereby, in the rectangular wave voltage control, the modulation factor is increased to 0.78.

  In the AC motor M1, the induced voltage increases as the rotational speed and output torque increase, so that the required drive voltage (motor required voltage) increases. The boosted voltage by the converter 12, that is, the system voltage VH, needs to be set higher than the required motor voltage. On the other hand, the system voltage VH has a limit value (VH maximum voltage). Therefore, the PWM control mode by sine wave PWM control or overmodulation PWM control and the rectangular wave voltage control mode are selectively applied according to the operating state of AC electric motor M1. In the rectangular wave voltage control, since the amplitude of the motor applied voltage is fixed, the phase control of the rectangular wave voltage pulse based on the torque deviation (the difference between the actual torque value (estimated value) and the torque command value) with respect to the torque command value. Thus, torque control is executed.

  FIG. 3 is a diagram for explaining the correspondence between the operating state of the AC motor and the control mode shown in FIG. Referring to FIG. 3, generally, in the low rotation speed range R1, sine wave PWM control is used to reduce the torque fluctuation, and in the middle rotation speed range R2, overmodulation PWM control and high rotation speed range R3 are used. Then, rectangular wave voltage control is applied. In particular, application of overmodulation PWM control and rectangular wave voltage control can improve the output of AC electric motor M1. As described above, which one of the control modes shown in FIG. 2 is used is basically determined within the range of the realizable modulation rate.

(Configuration of control device)
FIG. 4 is a functional block diagram functionally illustrating the configuration of the control device 30 shown in FIG. Referring to FIG. 4, control device 30 includes a PWM control unit 280, a rectangular wave voltage control unit 400, and a control mode switching unit 490. PWM control unit 280 includes a sine wave PWM control unit 200 and an overmodulation PWM control unit 201.

  Sine wave PWM control unit 200 receives torque command value Trqcom, motor currents iv and iw detected by current sensor 24, and rotation angle θ detected by rotation angle sensor 25. Based on these signals, the sine wave PWM control unit 200 generates voltage command values Vd # and Vq # to be applied to the inverter 14 by current feedback control, and generates the generated voltage command values Vd # and Vq #. Based on this, switching control signals S3 to S8 for driving inverter 14 are generated and output to control mode switching unit 490.

  The overmodulation PWM control unit 201 also generates switching control signals S3 to S8 for driving the inverter 14 by current feedback control similar to the sine wave PWM control unit 200, and controls the generated switching control signals S3 to S8. Output to the mode switching unit 490. The overmodulation PWM control unit 201 has a function of correcting the voltage amplitude in addition to the sine wave PWM control by the sine wave PWM control unit 200, and can increase the fundamental wave component of the voltage command value.

  Rectangular wave voltage control unit 400 receives torque command value Trqcom, motor currents iv and iw, and rotation angle θ. Then, the rectangular wave voltage control unit 400 sets the phase of the voltage to be applied to the inverter 14 based on these signals by torque feedback control, and drives the inverter 14 based on the set voltage phase. Switching control signals S3 to S8 are generated and output to control mode switching unit 490. In addition, rectangular wave voltage control unit 400 outputs torque deviation ΔTrq (calculated in the torque feedback control calculation) indicating the difference between actual torque (estimated value) with respect to torque command value Trqcom to control mode switching unit 490.

  Control mode switching unit 490 receives voltage command values Vd # and Vq # from sine wave PWM control unit 200, and receives system voltage VH from voltage sensor 13 (FIG. 1). Control mode switching unit 490 switches from the PWM control mode to the rectangular wave voltage control mode based on the modulation factor calculated from system voltage VH and voltage command values Vd # and Vq #. Specifically, control mode switching section 490 switches from PWM control mode to rectangular wave voltage control mode when the modulation factor reaches 0.78. Control mode switching section 490 selects the sine wave PWM control mode when the modulation rate is 0.61 or less, and selects the overmodulation PWM control mode when the modulation rate exceeds 0.61. Therefore, more specifically, control mode switching section 490 switches from overmodulation PWM control mode to rectangular wave voltage control mode when the modulation factor reaches 0.78.

  On the other hand, since the modulation factor is constant at 0.78 in the rectangular wave voltage control mode, switching from the rectangular wave voltage control mode to the PWM control mode (overmodulation PWM control mode) is performed based on the current phase. That is, control mode switching unit 490 receives torque deviation ΔTrq from rectangular wave voltage control unit 400, and further receives motor currents iv and iw and rotation angle θ. Control mode switching unit 490 switches from the rectangular wave voltage control mode to the PWM control mode (overmodulation PWM control mode) based on the current phase using these signals by the method described later.

(Configuration of each control mode)
FIG. 5 is a functional block diagram functionally illustrating the detailed configuration of the sine wave PWM control unit 200 shown in FIG. Referring to FIG. 5, sine wave PWM control unit 200 includes a current command generation unit 210, coordinate conversion units 220 and 250, a voltage command generation unit 240, and a PWM modulation unit 260.

  Current command generation unit 210 generates a d-axis current command value Idcom and a q-axis current command value Iqcom corresponding to torque command value Trqcom of AC electric motor M1 based on a previously created map or the like. The coordinate conversion unit 220 converts the v-phase current iv and the W-phase current iw detected by the current sensor 24 into the d-axis currents Id and q by coordinate conversion using the rotation angle θ of the AC motor M1 (uvw 3 phase → dq 2 phase). It converts into shaft current Iq.

  Voltage command generation unit 240 calculates a control deviation by performing a PI (proportional integration) operation on each of d-axis current deviation ΔId (ΔId = Idcom−Id) and q-axis current deviation ΔIq (ΔIq = Iqcom−Iq). Then, d-axis voltage command value Vd # and q-axis voltage command value Vq # corresponding to the control deviation are generated.

  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, and W-phase by coordinate conversion using the rotation angle θ of the AC motor M1 (dq2 phase → uvw3 phase). Each phase voltage command Vu, Vv, Vw of the phase is converted. The PWM modulation unit 260 generates switching control signals S3 to S8 for driving the inverter 14 based on the comparison between the phase voltage commands Vu, Vv, Vw and the carrier wave. The carrier wave is constituted by a triangular wave or a sawtooth wave having a predetermined frequency.

  FIG. 6 is a functional block diagram functionally illustrating the detailed configuration of the overmodulation PWM control unit 201 shown in FIG. 6, overmodulation PWM control unit 201 further includes a current filter 230 and a voltage amplitude correction unit 270 in the configuration of sine wave PWM control unit 200 shown in FIG. 5.

  The current filter 230 executes a process of smoothing the d-axis current Id and the q-axis current Iq calculated by the coordinate conversion unit 220 in the time axis direction. Thereby, the actual currents Id and Iq based on the sensor detection values are converted into the filtered currents Idf and Iqf. In the overmodulation PWM control unit 201, the current deviations ΔId and ΔIq are calculated using the filtered currents Idf and Iqf. That is, ΔId = Idcom−Idf and ΔIq = Iqcom−Iqf.

  Voltage amplitude correction unit 270 performs correction processing for expanding the amplitude of the motor applied voltage with respect to original d-axis voltage command value Vd # and q-axis voltage command value Vq # calculated by voltage command generation unit 240. Execute. Then, based on the voltage command subjected to the correction processing by the voltage amplitude correction unit 270, the coordinate conversion unit 250 and the PWM modulation unit 260 generate the switching control signals S3 to S8 of the inverter 14.

  When the overmodulation PWM control is applied, the amplitude of each phase voltage command obtained by converting the voltage command values Vd # and Vq # into two-phase to three-phase becomes larger than the inverter input voltage (system voltage VH). This state corresponds to a state in which the amplitude of the AC voltage command is larger than the amplitude of the carrier wave. However, since the inverter 14 cannot apply a voltage exceeding the system voltage VH to the AC motor M1, the original modulation rate corresponding to the voltage command values Vd # and Vq # can be secured in the above state. Disappear.

  Therefore, the voltage command value is obtained by performing a correction process for enlarging the voltage amplitude (× k times, k> 1) so that the voltage application interval is increased with respect to the AC voltage command using the voltage command values Vd # and Vq #. The original modulation rate by Vd # and Vq # can be secured. The voltage amplitude expansion ratio k by the voltage amplitude correction unit 270 can be theoretically derived based on this original modulation rate.

  FIG. 7 is a functional block diagram functionally illustrating the detailed configuration of the rectangular wave voltage control unit 400 shown in FIG. Referring to FIG. 7, rectangular wave voltage control unit 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.

  The power calculation unit 410 uses each phase current obtained from the V-phase current iv and the W-phase current iw detected by the current sensor 24, and each phase (U-phase, V-phase, W-phase) voltage Vu, Vv, Vw. Then, power supplied to the motor (motor power) Pmt is calculated according to the following equation (1). At this time, filter processing for removing distortion components from the detected motor current (iv, iw) is also executed.

Pmt = iu · Vu + iv · Vv + iw · Vw (1)
Torque calculation unit 420 shows actual torque using motor power Pmt calculated by power calculation unit 410 and angular velocity ω calculated from rotation angle θ of AC electric motor M1 detected by rotation angle sensor 25. Torque estimated value Trq is calculated according to the following equation (2).

Trq = Pmt / ω (2)
PI calculation unit 430 calculates a control deviation by performing PI calculation on torque deviation ΔTrq (ΔTrq = Trqcom−Trq) with respect to torque command value Trqcom, and sets phase φv of the rectangular wave voltage according to the 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 based on the phase voltage command values Vu, Vv, and Vw. Then, 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.

  Note that a torque deviation ΔTrq may be obtained based on a detection value of the torque sensor by disposing a torque sensor instead of the power calculation unit 410 and the torque calculation unit 420.

(Switching from rectangular wave voltage control to PWM control)
FIG. 8 is a diagram showing an actual torque delay with respect to the torque command value Trqcom. Referring to FIG. 8, curve k1 represents a time transition of torque command value Trqcom, and curve k2 represents a time transition of actual torque Trq (hereinafter also referred to as “actual torque” or “torque estimated value”). . It is assumed that the control mode is switched from rectangular wave voltage control to PWM control (overmodulation PWM control) in accordance with this torque change.

  As shown in FIG. 8, a follow-up delay (torque deviation) of the actual torque Trq occurs with respect to the torque command value Trqcom so that the actual torque Trq is A2 when the torque command value Trqcom is A1 at a certain time t. . Then, a switching delay from rectangular wave voltage control to PWM control (overmodulation PWM control) occurs due to this torque tracking delay. For example, when there is no torque tracking delay, the rectangular wave voltage control is overmodulated at point A1. When switching to PWM control, when a follow-up delay of torque occurs, switching from rectangular wave voltage control to overmodulation PWM control at point B occurs.

  9 and 10 are diagrams for explaining the switching delay from rectangular wave voltage control to PWM control (overmodulation PWM control). Referring to FIGS. 9 and 10, a curve k5 shows a current vector locus during rectangular wave voltage control, and a curve k6 shows a current vector locus during overmodulation PWM control. A curve k7 (FIG. 10) shows a switching determination value (current phase) for switching from rectangular wave voltage control to overmodulation PWM control. During the rectangular wave voltage control, the current vector moves on the curve k5, and when the current phase reaches the switching determination value, the rectangular wave voltage control is switched to the overmodulation PWM control.

  In conventional switching control, torque command value Trqcom is used as a switching determination value for switching from rectangular wave voltage control to overmodulation PWM control. Therefore, even when the torque command value Trqcom reaches the curve k6 (point A1), the current phase of the actual torque (point A2) has not yet reached the switching determination value due to the follow-up delay of the torque. Switching to control is not performed (FIG. 9).

  When torque command value Trqcom reaches a switching determination value indicated by curve k7 (point B), switching from rectangular wave voltage control to overmodulation PWM control is performed. Thus, if there is essentially no torque tracking delay, switching from rectangular wave voltage control to overmodulation PWM control is performed at the intersection of curve k5 and curve k6 shown in FIG. As shown in FIG. 10, there is a delay in switching from rectangular wave voltage control to overmodulation PWM control. This switching delay causes current disturbance and makes torque control unstable.

  Therefore, in the first embodiment, when the absolute value of the difference (torque deviation ΔTrq) between the actual torque Trq (estimated value) and the torque command value Trqcom is larger than the predetermined value, the predetermined value is added to the torque command value Trqcom. The switching value is set as the switching determination torque, and switching from the rectangular wave voltage control to the PWM control (overmodulation PWM control) is performed using the current phase calculated from the switching determination torque as the switching determination value. Thereby, the difference between the actual torque and the switching determination torque can be reduced, and the switching delay from the rectangular wave voltage control to the overmodulation PWM control can be suppressed.

  FIG. 11 is a diagram illustrating a switching determination torque used for switching determination from rectangular wave voltage control to PWM control (overmodulation PWM control). Referring to FIG. 11, curve k3 is a switch when the absolute value of the difference between actual torque Trq (curve k2) and torque command value Trqcom (curve k1) exceeds a predetermined value, that is, when torque deviation ΔTrq is large. Indicates the judgment torque. The switching determination torque indicated by the curve k3 is obtained by adding the predetermined value to the torque command value. When torque deviation ΔTrq is less than or equal to a predetermined value, torque command value Trqcom is set as the switching determination torque as before.

  FIG. 12 is a diagram illustrating that a switching delay from rectangular wave voltage control to PWM control (overmodulation PWM control) is suppressed. Referring to FIG. 12, curve k8 indicates a switching determination value (current phase) calculated from the switching determination torque of curve k3 shown in FIG. As shown in FIG. 12, the switching delay from the rectangular wave voltage control to the overmodulation PWM control is suppressed as compared with the case where the switching determination value (curve k7) calculated from the torque command value Trqcom is used.

  FIG. 13 is a functional block diagram of a portion related to switching from rectangular wave voltage control to PWM control (overmodulation PWM control) in control mode switching section 490 shown in FIG. Referring to FIG. 13, control mode switching unit 490 includes a switching determination torque setting unit 510, a switching determination value calculation unit 520, an actual current phase calculation unit 530, and a switching determination unit 540.

  Switch determination torque setting unit 510 receives torque command value Trqcom and torque deviation ΔTrq. Then, the switching determination torque setting unit 510 compares the absolute value of the torque deviation ΔTrq with a preset upper limit value. If the absolute value of the torque deviation ΔTrq is larger than the upper limit value, the switching determination torque setting unit 510 adds the upper limit value to the torque command value Trqcom. A value obtained by adding the value is set as the switching determination torque Trqc. On the other hand, when the absolute value of torque deviation ΔTrq is less than or equal to the upper limit value, torque command value Trqcom is set as switching determination torque Trqc.

  The switching determination value calculation unit 520 calculates a current phase from the switching determination torque Trqc set by the switching determination torque setting unit 510, and changes the calculated current phase from rectangular wave voltage control to PWM control (overmodulation PWM control). The switching determination value φic of The actual current phase calculation unit 530 calculates an actual current phase φi indicating an actual current phase based on the V phase current iv, the W phase current iw, and the rotation angle θ. Then, the switching determination unit 540 compares the actual current phase φi with the switching determination value φic, and switches the control mode from rectangular wave voltage control to overmodulation PWM control when the actual current phase φi becomes smaller than the switching determination value φic.

  FIG. 14 is a flowchart showing a switching procedure from rectangular wave voltage control to PWM control (overmodulation PWM control) by the control device 30 shown in FIG. The process of this flowchart is called from the main routine and executed every certain time or every time a predetermined condition is satisfied.

  Referring to FIG. 14, control device 30 determines whether or not the current control mode is a rectangular wave voltage control mode (step S5). If it is determined that the current control mode is not the rectangular wave voltage control mode (NO in step S5), control device 30 proceeds to step S80 without executing a series of subsequent processes.

  When it is determined in step S5 that the current control mode is the rectangular wave voltage control mode (YES in step S5), control device 30 determines the difference (torque deviation ΔTrq) between estimated torque value Trq and torque command value Trqcom. It is determined whether or not the absolute value is larger than a preset upper limit value (step S10). When it is determined that the absolute value of torque deviation ΔTrq is equal to or smaller than the upper limit value (NO in step S10), control device 30 sets torque command value Trqcom as a switching determination torque (step S20). On the other hand, when it is determined in step S10 that the absolute value of torque deviation ΔTrq is larger than the upper limit value (YES in step S10), control device 30 sets a value obtained by adding the upper limit value to torque command value Trqcom as a switching determination torque. (Step S30).

  Next, control device 30 calculates switching determination value φic (current phase) from rectangular wave voltage control to PWM control (overmodulation PWM control) from the switching determination torque set in step S20 or S30 (step S40). . Furthermore, the control device 30 calculates the actual current phase φi based on the actual current (V-phase current iv, W-phase current iw) detected by the current sensor 24 and the rotation angle θ detected by the rotation angle sensor 25 ( Step S50). Then, control device 30 determines whether or not actual current phase φi is smaller than switching determination value φic calculated from the switching determination torque (step S60).

  When it is determined that actual current phase φi is smaller than switching determination value φic (YES in step S60), control device 30 switches the control mode from rectangular wave voltage control to overmodulation PWM control (step S70). On the other hand, when it is determined that actual current phase φi is greater than or equal to switching determination value φic (NO in step S60), control device 30 does not switch the control mode from rectangular wave voltage control to overmodulation PWM control, but in step S80. Transfer processing to.

  As described above, in the first embodiment, when the absolute value of the difference (torque deviation ΔTrq) between actual torque Trq and torque command value Trqcom is larger than a predetermined value, a predetermined value is added to torque command value Trqcom. Since the value is used for the switching determination torque, the deviation between the switching determination torque and the actual torque is suppressed. Therefore, according to the first embodiment, the switching delay from the rectangular wave voltage control to the PWM control can be suppressed.

[Modification]
In rectangular wave voltage control, the lower the motor rotation speed (rotational speed), the worse the control response and the more likely the torque follow-up delay occurs. Therefore, as shown in FIG. 15, the upper limit value for setting the switching determination torque may be variable according to the motor rotation speed. Specifically, the upper limit value may be reduced as the rotational speed is lower, and the switching delay compensation may be more actively performed.

  Further, in the rectangular wave voltage control, the lower the system voltage VH, the worse the control response and the more likely the torque follow-up delay occurs. Therefore, as shown in FIG. 16, the upper limit value may be variable according to the system voltage VH. Specifically, the upper limit value may be decreased as the system voltage is lower, and the switching delay compensation may be more actively performed.

  Further, in the rectangular wave voltage control, the control response is worse as the torque is larger, and the follow-up delay of the torque is likely to occur. Therefore, as shown in FIG. 17, the upper limit value may be made variable in accordance with the torque command value Trqcom. Specifically, the upper limit value may be decreased as the torque command value Trqcom is increased, and the switching delay compensation may be more actively performed.

[Embodiment 2]
In the second embodiment, a filter value obtained by subjecting the torque command value Trqcom to delay filter processing is used as the switching determination torque. Thereby, the deviation between the switching determination torque and the actual torque is suppressed more than in the first embodiment, and the switching delay from the rectangular wave voltage control to the PWM control (overmodulation PWM control) can be further suppressed.

  FIG. 18 is a diagram illustrating the switching determination torque in the second embodiment. Referring to FIG. 18, curve k4 represents a filter value obtained by subjecting torque command value Trqcom indicated by curve k1 to delay filter processing. Note that the time constant of this filter processing can be calculated from, for example, the cutoff frequency ωc of the transfer characteristic to be controlled in the rectangular wave voltage control shown in FIG.

  FIG. 19 is a diagram illustrating that a switching delay from rectangular wave voltage control to PWM control (overmodulation PWM control) is suppressed. Referring to FIG. 19, curve k9 represents a switching determination value (current phase) calculated from the switching determination torque of curve k4 illustrated in FIG. As shown in FIG. 19, the switching delay from the rectangular wave voltage control to the overmodulation PWM control is significantly suppressed as compared with the case where the switching determination value (curve k7) calculated from the torque command value Trqcom is used.

  FIG. 20 is a flowchart showing a switching procedure from rectangular wave voltage control to PWM control (overmodulation PWM control) by control device 30 in the second embodiment. The processing of this flowchart is also called from the main routine and executed every certain time or every time a predetermined condition is satisfied.

  Referring to FIG. 20, control device 30 determines whether or not the current control mode is a rectangular wave voltage control mode (step S105). If it is determined that the current control mode is not the rectangular wave voltage control mode (NO in step S105), control device 30 proceeds to step S190 without executing a series of subsequent processes.

  If it is determined in step S105 that the current control mode is the rectangular wave voltage control mode (YES in step S105), control device 30 calculates a filter value obtained by subjecting torque command value Trqcom to a delay filter process (step S105). S110). Then, control device 30 determines whether or not the absolute value of the difference between estimated torque value Trq and the filter value is greater than a preset upper limit value (step S120).

  If it is determined that the absolute value is equal to or lower than the upper limit value (NO in step S120), control device 30 sets the filter value calculated in step S110 as the switching determination torque (step S130). On the other hand, if it is determined in step S120 that the absolute value is larger than the upper limit value (YES in step S120), control device 30 determines to switch the value obtained by adding the upper limit value to the filter value calculated in step S110. Torque is set (step S140).

  Since subsequent steps S150, S160, S170, and S180 are the same as steps S40, S50, S60, and S70 in the flowchart shown in FIG. 14, the description thereof will not be repeated.

  As described above, in the second embodiment, the filter value obtained by performing the delay filter process on the torque command value Trqcom is used as the switching determination torque, and therefore, the difference between the switching determination torque and the actual torque is different from that in the first embodiment. Is also suppressed. Therefore, according to the second embodiment, the switching delay from the rectangular wave voltage control to the PWM control (overmodulation PWM control) can be further suppressed.

  In each of the above-described embodiments, as a preferable configuration example, DC voltage generation unit 10 # of motor drive control system 100 controls converter 12 so that the input voltage (system voltage VH) to inverter 14 can be variably controlled. Although the configuration including the DC voltage generation unit 10 # is not limited to the configuration illustrated in FIG. 1, the DC voltage generation unit 10 # is not limited as long as the input voltage to the inverter 14 can be variably controlled. Further, it is not essential that the inverter input voltage (system voltage VH) is variable, and also for a configuration in which the output voltage of power storage device B is directly input to inverter 14 (for example, a configuration in which arrangement of converter 12 is omitted). The present invention is applicable.

  Furthermore, with respect to the AC motor serving as a load of the motor drive control system 100, in each of the above embodiments, a permanent magnet motor mounted for driving a vehicle in an electric vehicle (such as a hybrid vehicle or an electric vehicle) is assumed. The present invention can also be applied to a configuration in which an arbitrary AC motor used for other devices is used as a load.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  5-7 Power line, 10, 13 Voltage sensor, 10 # DC voltage generator, 11, 24 Current sensor, 12 Converter, 14 Inverter, 15 U phase upper and lower arm, 16 V phase upper and lower arm, 17 W phase upper and lower arm, 25 rotation Angle sensor, 30 control device, 100 motor drive system, 200 sine wave PWM control unit, 201 overmodulation PWM control unit, 210 current command generation unit, 220, 250 coordinate conversion unit, 230 current filter, 240 voltage command generation unit, 260 PWM modulation unit, 270 voltage amplitude correction unit, 280 PWM control unit, 400 rectangular wave voltage control unit, 410 power calculation unit, 420 torque calculation unit, 430 PI calculation unit, 440 rectangular wave generator, 450 signal generation unit, 490 control Mode switching unit, 510 switching determination torque setting unit, 520 switching determination value (current Phase) calculation unit, 530 actual current phase calculation unit, 540 switching determination unit, B power storage device, SR1, SR2 system relay, C0, C1 smoothing capacitor, Q1-Q8 switching element, D1-D8 diode, L1 reactor, M1 AC motor .

Claims (4)

A control device for an AC motor driven by an inverter,
A pulse width modulation control unit for generating a control command for the inverter according to a pulse width modulation method;
A rectangular wave voltage control unit that generates the control command so as to apply a rectangular wave voltage phase-controlled to operate the AC motor according to a torque command value, to the AC motor;
Using the current phase calculated from a predetermined switching determination torque for switching determination from rectangular wave voltage control by the rectangular wave voltage control unit to pulse width modulation control by the pulse width modulation control unit, from the rectangular wave voltage control to the A control mode switching unit for switching to pulse width modulation control,
The control mode switching unit uses the torque command value as the switching determination torque when the absolute value of the torque deviation with respect to the torque command value is less than or equal to a predetermined value, and A control device for an AC electric motor using a value obtained by adding the predetermined value to the torque command value as the switching determination torque.   The control apparatus for an AC motor according to claim 1, wherein the predetermined value is variably set according to at least one of a rotational speed of the AC motor, a system voltage applied to the inverter, and a torque of the AC motor.   The AC motor according to claim 1, wherein the control mode switching unit uses a filter value obtained by subjecting the torque command value to delay filter processing as a torque command value used for setting the switching determination torque. Control device. The pulse width modulation control unit
A sine wave pulse width modulation control unit for generating the control command according to a sine wave pulse width modulation method;
A pulse width overmodulation control unit that generates the control command according to a pulse width overmodulation scheme that increases the amplitude of the fundamental wave component than the sine wave pulse width modulation scheme;
The control mode switching unit switches from the rectangular wave voltage control to pulse width overmodulation control by the pulse width overmodulation control unit using a current phase calculated from the switching determination torque. The control apparatus for an AC motor according to claim 3.

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