JP2012244804A - Motor drive control system, vehicle loaded with the same, and control method of motor drive control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve control stability when switching from rectangular wave control to PWM control, in a motor drive control system for driving an AC motor.SOLUTION: A motor drive control system 100 drives an AC motor 200 by an inverter 140. An ECU 300 controls the inverter 140 by a control mode of either rectangular wave control mode or pulse width modulation control mode. The ECU 300 switches from the rectangular wave control mode to the pulse width modulation control mode as a current phase φimpressed to the AC motor 200 reaches a threshold φduring execution of the rectangular wave control mode. Then, the ECU 300 changes the threshold φof the current phase φon the basis of a change of a voltage phase φv impressed to the AC motor 200 during the execution of the rectangular wave control mode.

Description

  The present invention relates to a motor drive control system, a vehicle on which the motor drive control system is mounted, and a control method of the motor drive control system. More specifically, rectangular wave control and pulse width modulation (PWM) control are applied. The present invention relates to control of an AC motor.

  In order to drive and control an AC motor using a DC power supply, a driving method using an inverter is generally employed. The inverter is switching-controlled by an inverter drive circuit. For example, a voltage switched according to PWM control is applied to the AC motor.

  In addition, overmodulation PWM control is used as an AC motor control by a modulation method in which the fundamental component of the motor applied voltage is larger than the sine wave PWM control in order to improve the voltage utilization rate and obtain a high output in a region where the motor rotation speed is high. And square wave control may be applied.

  Japanese Patent Laid-Open No. 2005-218299 (Patent Document 1) discloses that when operating with rectangular wave control, the absolute value of the actual current phase supplied to the AC motor falls below the absolute value of the predetermined switching current phase. A configuration for switching from rectangular wave control to PWM control is described.

JP 2005-218299 A

  In the control of an AC motor to which PWM control and rectangular wave control are applied, so-called chattering in which two control modes are frequently switched when switching from rectangular wave control for controlling the voltage phase to PWM control by current feedback. In order to prevent this, control with hysteresis is sometimes performed so that the control mode is switched at an operation point slightly over the ideal switching point of the control mode.

  In such control, immediately after switching from rectangular wave control to PWM control, the current command in PWM control changes discontinuously, and the output voltage of the inverter applied to the AC motor changes stepwise. Therefore, the torque may fluctuate greatly in an instant.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide control stability at the time of switching from rectangular wave control to PWM control in a motor drive control system for driving an AC motor. Is to improve.

  A motor drive control system according to the present invention includes an inverter that controls a drive voltage of an AC motor and a control device that controls the inverter. The inverter is a rectangular wave control mode for driving the AC motor by controlling the voltage phase of the rectangular wave voltage applied to the AC motor, and a pulse width based on a comparison between an AC voltage command for operating the AC motor and a carrier wave. Control is performed in a pulse width modulation control mode in which the AC motor is driven by performing modulation control. During execution of the rectangular wave control mode, the control device executes switching from the rectangular wave control mode to the pulse width modulation control mode in response to the current phase applied to the AC motor reaching the threshold value. And a control apparatus changes a threshold value based on the change of the voltage phase applied to an alternating current motor during execution of rectangular wave control mode.

  Preferably, when the voltage phase changes in the acceleration direction, the control device sets the threshold value so that switching from the rectangular wave control mode to the pulse width modulation control mode is delayed compared to when the voltage phase does not change. To change.

  Preferably, the control device sets the threshold value so that the switching from the rectangular wave control mode to the pulse width modulation control mode is faster when the voltage phase is changing in the deceleration direction than when the voltage phase is not changing. To change.

  Preferably, the control device changes the threshold value when the magnitude of the temporal change in the voltage phase is larger than the first reference value.

  Preferably, the control device prohibits the change of the threshold value when the magnitude of the temporal change in the voltage command value applied to the AC motor is smaller than the second reference value.

  Preferably, the voltage phase is determined based on a d-axis voltage command value with respect to a q-axis voltage command value for a voltage command value applied to the AC motor.

  Preferably, the current phase is determined based on a d-axis current value with respect to a q-axis current value of a current flowing through the AC motor.

  A vehicle according to the present invention includes a power storage device, an AC motor, and any one of the motor drive control systems described above.

  The motor drive control system control method according to the present invention is a control method for a motor drive control system that drives an AC motor by an inverter. The control method includes: selecting a rectangular wave control mode for driving the AC motor by controlling the voltage phase of the rectangular wave voltage applied to the AC motor; and an AC voltage command for operating the AC motor and a carrier wave. The step of selecting a pulse width modulation control mode for driving the AC motor by performing pulse width modulation control based on the comparison, and the current phase applied to the AC motor reaches a threshold value during execution of the rectangular wave control mode. In response, the step of switching from the rectangular wave control mode to the pulse width modulation control mode, and the step of changing the threshold value based on a change in the voltage phase applied to the AC motor during execution of the rectangular wave control mode With.

  ADVANTAGE OF THE INVENTION According to this invention, in the motor drive control system which drives an AC motor, the control stability at the time of switching from rectangular wave control to PWM control can be improved.

1 is an overall block diagram of a motor drive control system according to an embodiment of the present invention. It is a figure which illustrates roughly the control mode of the AC motor in the motor drive system by this Embodiment. It is a figure explaining the correspondence of the operation state of an AC motor, and each control mode by this embodiment. It is a functional block diagram which shows the control structure of the motor drive system by this Embodiment. It is a conceptual diagram which shows the change of the d-axis and q-axis current command value on the dq-axis plane in rectangular wave control and PWM control. It is a conceptual diagram which shows the change of the d-axis and q-axis current command value on a dq-axis plane at the time of switching from rectangular wave control to PWM control. It is a 1st figure for demonstrating the outline | summary of the mode switching control in this Embodiment. It is a 2nd figure for demonstrating the outline | summary of the mode switching control in this Embodiment. It is a 3rd figure for demonstrating the outline | summary of the mode switching control in this Embodiment. In this Embodiment, it is a flowchart for demonstrating the detail of the mode switching control process performed by ECU. It is a flowchart for demonstrating the detail of the process in FIG.10 S150.

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

(General configuration of motor control)
FIG. 1 is an overall block diagram of a vehicle 10 equipped with a motor drive control system 100 according to an embodiment of the present invention.

  Referring to FIG. 1, vehicle 10 includes a motor drive control system 100, an AC motor 200, and drive wheels 210. Motor drive control system 100 includes a DC voltage generation unit 105, a capacitor C <b> 1, an inverter 140, and a control device (hereinafter also referred to as ECU “Electronic Control Unit”) 300.

  AC motor 200 is a drive motor that generates torque for driving drive wheels 210 in a vehicle that generates a vehicle driving force by electric energy such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle. Alternatively, AC electric motor 200 may be configured to have a function of a generator driven by an engine (not shown), or may be configured to have both functions of an electric motor and a generator. Furthermore, AC electric motor 200 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. That is, in the present embodiment, the “AC motor” includes an AC drive motor, a generator, and a motor generator (motor generator).

  DC voltage generation unit 105 includes a DC power supply 110, system relays SR1 and SR2, a capacitor C2, a converter 120, voltage sensors 150 and 170, and a current sensor 160.

  The DC power supply 110 is typically configured by a secondary battery such as a nickel metal hydride battery or a lithium ion battery, or a power storage device such as an electric double layer capacitor. Voltage sensor 150 detects DC voltage VB output from DC power supply 110. The current sensor 160 detects a direct current IB that is input to and output from the direct current power source 110. These detected values are output to ECU 300.

  System relay SR1 is connected between a positive terminal of DC power supply 110 and power line PL1. System relay SR2 is connected between the negative terminal of DC power supply 110 and ground line NL1. System relays SR <b> 1 and SR <b> 2 are controlled by a control signal SE from ECU 300, and switch between supply and interruption of power between DC power supply 110 and converter 120.

  Converter 120 includes a reactor L1, switching elements Q1, Q2, and diodes D1, D2. Switching elements Q1, Q2 are connected in series between power line PL2 and ground line NL1. Switching elements Q1, Q2 are controlled by a switching control signal PWC from ECU 300.

  In the present embodiment, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, a power bipolar transistor, or the like can be used as the switching element. Anti-parallel diodes D1 and D2 are arranged for switching elements Q1 and Q2. Reactor L1 is connected between a connection node of switching elements Q1, Q2 and power line PL1.

  Capacitor C2 is connected between power line PL1 and ground line NL1, and reduces voltage fluctuation between power line PL1 and ground line NL1. Voltage sensor 170 detects voltage VL across capacitor C2, and outputs the detected value to ECU 300.

  Converter 120 is basically controlled such that switching elements Q1 and Q2 are turned on and off in a complementary manner in each switching period. During the boosting operation, converter 120 boosts DC voltage VL supplied from DC power supply 110 to DC voltage VH (this DC voltage corresponding to the input voltage to inverter 140 is also referred to as “system voltage” hereinafter). This boosting operation is performed by supplying the electromagnetic energy accumulated in reactor L1 during the ON period of switching element Q2 to power line PL2 via switching element Q1 and antiparallel diode D1.

  Converter 120 steps down DC voltage VH to DC voltage VL during the step-down operation. This step-down operation is performed by supplying the electromagnetic energy stored in reactor L1 during the ON period of switching element Q1 to ground line NL1 via switching element Q2 and antiparallel diode D2. The voltage conversion ratio (the ratio of VH and VL) in these step-up and step-down operations is controlled by the on-period ratio (duty ratio) of the switching elements Q1 and Q2 in the switching period. Note that VH = VL (voltage conversion ratio = 1.0) can be obtained by switching the switching element Q1 on and fixing the switching element Q2 off.

  Capacitor C <b> 1 smoothes the DC voltage from converter 120 and supplies the smoothed DC voltage to inverter 140. Voltage sensor 130 detects the voltage across capacitor C1, that is, system voltage VH, and outputs the detected value to ECU 300.

  Inverter 140 includes a U-phase upper and lower arm 141, a V-phase upper and lower arm 142, and a W-phase upper and lower arm 143 that are provided in parallel between power line PL2 and ground line NL1. Each phase upper and lower arm includes a switching element connected in series between power line PL2 and ground line NL1. For example, U-phase upper and lower arms 141 include switching elements Q3 and Q4, V-phase upper and lower arms 142 include switching elements Q5 and Q6, and W-phase upper and lower arms 143 include switching elements Q7 and Q8. Antiparallel diodes D3 to D8 are connected to switching elements Q3 to Q8, respectively. Switching elements Q3 to Q8 are controlled by a control signal PWI from ECU 300.

  AC motor 200 is typically a three-phase permanent magnet synchronous motor, and one end of three coils in U, V, and W phases is commonly connected to a neutral point. Furthermore, the other end of each phase coil is connected to the connection node of the switching element in each phase upper and lower arms 141-143.

  Inverter 140, when the torque command value of AC electric motor 200 is positive (Trqcom> 0), DC voltage supplied from capacitor C1 by the switching operation of switching elements Q3-Q8 in response to control signal PWI from ECU 300 AC motor 200 is driven so as to convert AC to AC voltage and output a positive torque. Further, when the torque command value of AC electric motor 200 is zero (Trqcom = 0), inverter 140 converts the DC voltage to the AC voltage so that the torque becomes zero by the switching operation in response to control signal PWI. AC motor 200 is driven. As a result, AC electric motor 200 is driven to generate zero or positive torque designated by torque command value Trqcom.

  Further, during regenerative braking of a vehicle equipped with motor drive control system 100, torque command value Trqcom of AC electric motor 200 is set to be negative (Trqcom <0). In this case, the inverter 140 converts the AC voltage generated by the AC motor 200 into a DC voltage by a switching operation in response to the control signal PWI, and converts the converted DC voltage (system voltage VH) via the capacitor C1. To the converter 120. Note that regenerative braking here refers to braking that involves regenerative power generation when the driver operating the vehicle performs a footbrake operation, or regenerative power generation by turning off the accelerator pedal while driving, although the footbrake is not operated. Including decelerating (or stopping acceleration) the vehicle while moving.

  Current sensor 240 detects motor current MCRT flowing through AC electric motor 200 and outputs the detected motor current to ECU 300. Since the sum of instantaneous values of the three-phase currents iu, iv, iw is zero, the current sensor 240 has two-phase motor currents (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) 250 detects the rotation angle θ of the AC electric motor 200 and outputs the detected rotation angle θ to the ECU 300. ECU 300 can calculate rotational speed MRT and angular speed ω (rad / s) of AC electric motor 200 based on rotational angle θ. Note that the rotation angle sensor 250 may be omitted by directly calculating the rotation angle θ from the motor voltage or current in the ECU 300.

  The ECU 300 is configured by an electronic control unit (control device), and the motor drive control system 100 is implemented by software processing by executing a program stored in advance by a CPU (not shown) and / or hardware processing by a dedicated electronic circuit. To control the operation.

  As representative functions, the ECU 300 detects the input torque command value Trqcom, the DC voltages VB and VL detected by the voltage sensors 150 and 170, the DC current IB detected by the current sensor 160, and the voltage sensor 130. Based on system voltage VH, motor currents iv, iw from current sensor 240, rotation angle θ from rotation angle sensor 250, etc., converter 120 and AC motor 200 output torque according to torque command value Trqcom. The operation of the inverter 140 is controlled. That is, ECU 300 generates control signals PWC and PWI for controlling converter 120 and inverter 140, and outputs them to converter 120 and inverter 140.

  During the boosting operation of converter 120, ECU 300 performs feedback control of system voltage VH and generates control signal PWC so that system voltage VH matches the voltage command value.

  When ECU 300 receives a regenerative signal RGE indicating that the vehicle has entered the regenerative braking mode from an external control device, ECU 300 generates control signal PWI so as to convert the AC voltage generated by AC motor 200 into a DC voltage. Output to the inverter 140. Thereby, inverter 140 converts the AC voltage generated by AC motor 200 into a DC voltage and supplies it to converter 120. ECU 300 generates control signal PWC so as to step down the DC voltage supplied from inverter 140, and outputs it to converter 120. As a result, the AC voltage generated by the AC motor 200 is converted to a DC voltage, stepped down, and supplied to the DC power supply 110.

(Description of control mode)
The control of AC electric motor 200 by ECU 300 will be described in further detail. FIG. 2 schematically illustrates a control mode of AC electric motor 200 in motor drive control system 100 according to the embodiment of the present invention.

  As shown in FIG. 2, in motor drive control system 100 according to the embodiment of the present invention, there are three control modes (sine wave PWM control, overmodulation PWM control) for control of AC electric motor 200, that is, power conversion in inverter 140. , Square wave control).

  The sine wave PWM control is used as a general PWM control, and controls on / off of each phase upper and lower arm elements according to 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. As is well known, in the 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 of the voltage applied to the AC motor 200 (hereinafter also simply referred to as “motor applied voltage”). The component can only be increased to about 0.61 times the DC link voltage of the inverter. Hereinafter, the ratio of the fundamental wave component (effective value) of the motor applied voltage (line voltage) to the DC link voltage of the inverter 140 (that is, the system voltage VH) is referred to as “modulation rate”.

  In the sine wave PWM control, since the amplitude of the voltage command of the sine wave is within the range of the carrier wave amplitude, the line voltage applied to the AC motor 200 becomes a sine wave.

  In the rectangular wave 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. As a result, the modulation rate is increased to 0.78.

  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 amplitude correction that distorts the voltage command from the original sine wave waveform, and the modulation rate can be increased from the maximum modulation rate in the sine wave PWM control mode to a range of 0.78. In overmodulation PWM control, the voltage command (sinusoidal component) has a larger amplitude than the carrier wave amplitude, so the line voltage applied to AC motor 200 is not a sine wave but a distorted voltage.

  In AC electric motor 200, 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 converter 120, that is, system voltage VH needs to be set higher than this motor required voltage. On the other hand, there is a limit value (VH maximum voltage) in the boosted voltage by converter 120, that is, system voltage VH.

  Therefore, a PWM control mode (sine wave PWM control or overmodulation PWM control) for controlling the amplitude and phase of the motor applied voltage (AC) by feedback of the motor current according to the operating state of AC motor 200, and rectangular wave control. One of the modes is selectively applied. In the rectangular wave control, since the amplitude of the motor applied voltage is fixed, the only controllable parameter is the phase of the motor applied voltage. In rectangular wave control, when executing torque feedback control that directly controls the phase of the rectangular wave voltage pulse based on the deviation between the target torque command value and the actual torque value, and in the same way as PWM control, The phase of the motor applied voltage may be controlled by feedback.

  FIG. 3 shows a correspondence relationship between the operation state of AC electric motor 200 and the above-described control mode. Referring to FIG. 3, schematically, sinusoidal PWM control is used in order to reduce the torque fluctuation in the low rotational speed range A1, overmodulation PWM control in the intermediate rotational speed range A2, and in the high rotational speed range A3. Square wave control is applied. In particular, the output of AC motor 200 is improved by applying overmodulation PWM control and rectangular wave control. 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 showing a control configuration of ECU 300 in the present embodiment. Each functional block described in the block diagram illustrated in FIG. 4 is realized by hardware or software processing by ECU 300.

  Referring to FIG. 4, ECU 300 includes a PWM control unit 310, a rectangular wave control unit 320, and a control mode selection unit 330. The PWM control unit 310 includes a sine wave PWM control unit 312 and an overmodulation PWM control unit 314. As described with reference to FIGS. 2 and 3, the sine wave PWM control and the overmodulation PWM control are performed according to the modulation rate. Is selectively executed.

  An outline of the control operation in the PWM control mode and the rectangular wave control mode will be described. The details of the control in each control mode are well known to those skilled in the art and will not be described here.

  First, the case where the PWM control mode is selected will be described. PWM control unit 310 receives torque command value Trqcom, motor currents iv and iw, and rotation angle θ from a higher-level control device (not shown). Then, the PWM control unit 310 uses the d-axis and q-axis current command values calculated from the torque command value Trqcom and the current detection value obtained by converting the motor current detection value into the d-axis and q-axis. To generate voltage command values Vd # and Vq # to be applied to the inverter 140. The generated voltage command values Vd # and Vq # are output to the control mode selection unit 330. Further, PWM control unit 310 generates control signal PWI for driving inverter 140 based on voltage command values Vd # and Vq # and outputs the control signal PWI to inverter 140.

  Further, when the PWM control unit 310 selects overmodulation PWM control, the overmodulation PWM control unit 314 is selected. The overmodulation PWM control unit 314 has a function of correcting the voltage amplitude in addition to the sine wave PWM control described above, thereby enhancing the fundamental wave component of the voltage command value and generating a larger output than the sine wave PWM control. To do.

Next, a case where the rectangular wave control mode is selected will be described. Rectangular wave control unit 320 receives torque command value Trqcom, motor currents iv, iw, and rotation angle θ. Then, the rectangular wave control unit 320 performs torque feedback control by comparing the torque command value Trqcom with the torque calculated from the motor current detection values iv and iw and the current voltage command value of each phase, and Voltage command values Vd # and Vq # to be applied are generated. In the rectangular wave control, the amplitude (VR = (Vd # ² + Vq # ² ) ^1/2 ) of the voltage command is fixed to that corresponding to the system voltage VH, and as a result, only the phase φv of the voltage command is obtained. Current and voltage command values are generated so that is controlled.

  Regarding the generation of the current command values Id # and Iq #, for example, only the q-axis current value is set by feedback control, while the d-axis current is calculated backward so that the magnitude of the voltage command becomes a predetermined magnitude. Can also be calculated. The rectangular wave control unit 320 outputs the current command values Id # and Iq # thus generated to the control mode selection unit 330.

  Thus, when the rectangular wave control mode is applied, motor torque control can be performed by torque feedback control. However, in the PWM control mode, the amplitude and phase of the motor applied voltage are the manipulated variables, whereas in the rectangular wave control mode, only the phase of the motor applied voltage is the manipulated variable. For this reason, when the rectangular wave control mode is applied, the control responsiveness is lower than when the PWM control mode is applied.

Control mode selection unit 330 includes system voltage VH, voltage command values Vd # and Vq # from PWM control unit 310, current command values Id # and Iq # from rectangular wave control unit 320, and motor currents iv and iw. And the rotation angle θ. Then, control mode selection unit 330 determines whether or not it is necessary to switch from the PWM control mode to the rectangular wave control mode based on the modulation factor calculated from system voltage VH and voltage command values Vd # and Vq #. In addition, control mode selection unit 330 uses rectangular wave control mode based on AC current phase (actual current phase) φi _# supplied from inverter 140 to AC electric motor 200 calculated from current command values Id # and Iq _#. To determine whether or not to switch to the PWM control mode.

(Problems when switching from rectangular wave control to PWM control)
Next, problems of motor control when switching from rectangular wave control to PWM control will be described. In particular, a problem in control stability when the control mode shifts from the rectangular wave control to the PWM control when the output of the AC motor 200 decreases from the high output region will be described. In the following description, the case of a power running operation will be described as an example for easy understanding.

  FIG. 5 shows an example of changes in the d-axis and q-axis current command values on the dq-axis plane in rectangular wave control and PWM control. Referring to FIG. 5, the horizontal axis and the vertical axis in the figure indicate current command values for d-axis and q-axis, respectively. W10 indicates a current command line in PWM control. The current command line in the PWM control represents a locus of a current vector indicating a current phase at which the torque is maximum for the same current on the dq axis plane. Therefore, by driving the motor with a current command along the current command line, torque can be generated most efficiently with respect to the motor current. W20 is a line indicating a locus of a current command determined so that a voltage phase for outputting the target torque can be achieved in the rectangular wave control.

  In switching from rectangular wave control to PWM control, in the rectangular wave control mode, the current command changes in the direction indicated by arrow AR10 in the drawing along the current command line of W20 as the output decreases. Ideally, when the intersection point P1 between W10 and W20 is reached, the control mode is switched from the rectangular wave control to the PWM control, and thereafter the current command changes along W10.

  When the output increases, it changes in the direction opposite to the arrow AR10 in the figure. That is, the control mode is switched from PWM control to rectangular wave control when the current command changes along W10 by the PWM control and reaches the intersection P1. Then, rectangular wave control is executed along W20.

  However, in the case of such switching, there is a possibility that so-called chattering, in which switching between both the rectangular wave control mode and the PWM control mode is frequently repeated, occurs near the intersection P1. Therefore, in actual control, in order to prevent this chattering, as shown in FIG. 6, when rectangular wave control is being executed, when the operating point P20 is slightly over the intersection P1 along W20, There is a case in which a method of adding hysteresis that switches the control mode from wave control to PWM control is employed.

This operating point P20 for switching from rectangular wave control to PWM control is determined by setting a threshold value for the phase φ _{i #} of the current command value. Specifically, assuming that the current phase threshold when the current command value becomes the operating point P20 is φ _th0 , the magnitude of the phase φ _{i #} of the current command value is smaller than the threshold φ _th0 . In response, the control mode is switched from rectangular wave control to PWM control.

  However, in such a switching method, since the current command changes discontinuously from P20 to P10 in FIG. 6, the current deviation immediately after switching of the control mode may increase. An excessive torque is output by performing current feedback in PWM control with respect to the current deviation. As a result, torque shock and vibration may occur, and control stability may be impaired. In particular, when the output torque is large, the fluctuation range of this current becomes large, so the influence becomes remarkable.

(Description of mode switching control)
Therefore, in the present embodiment, as shown in FIG. 7, a threshold for switching from rectangular wave control to PWM control in consideration of the direction of fluctuation of the current command value after the control mode is switched to PWM control. The mode switching control for changing the value _φth is executed.

More specifically, when the current command value transitions in the acceleration direction (output increase direction) as indicated by the arrow AR11 after the control mode is switched from rectangular wave control to PWM control and the operating point shifts to P10. Will return the control mode from PWM control to rectangular wave control again. In this case, the PWM control from the rectangular wave control, and, since the control mode to the rectangular wave control from the PWM control frequent switching switched, possibly chattering keep the size smaller threshold phi _th occurs Is expensive. Therefore, in such a case, priority is given to prevention of chattering over the occurrence of torque shock, and the threshold φ _th is made smaller, in other words, switching from rectangular wave control to PWM control is delayed. _Is set to the threshold value φth. As a result, since the hysteresis can be increased, the occurrence of chattering can be suppressed.

On the other hand, when the current command value transitions in the deceleration direction (output decreasing direction) as indicated by the arrow AR12 after the operating point shifts to P10, the PWM control is continued. In this case, since there is little possibility of chattering, priority is given to suppression of the occurrence of torque shock and vibration, and the magnitude of the threshold φ _th is increased, in other words, the switching operating point is represented by the curve W10. The threshold value _φth is set so that the switching from the rectangular wave control to the PWM control is accelerated near the point P1 that is the intersection with W20.

  At this time, as described above, since the control parameter in the rectangular wave control is the voltage phase, it is correctly determined whether the operating point is changing in the acceleration direction or the deceleration direction when the current phase changes. Can not. Therefore, in this embodiment, the transition direction of the operating point is determined based on the voltage phase change state in the rectangular wave control.

  FIG. 8 shows changes in voltage command values on the dq axis plane when PWM control and rectangular wave control are performed. In FIG. 8, a curve W30 shows a locus of voltage command values in PWM control, and a curve W31 moving on the circumference shows a locus of voltage command values in rectangular wave control. When the accelerator of the vehicle is depressed and accelerates, the voltage command value changes in the direction indicated by the solid arrow AR31 in FIG. 8, and the control is switched from PWM control to rectangular wave control at point P30. On the other hand, when the brake is depressed and decelerates, the voltage command value changes in the direction indicated by the broken arrow AR32 in FIG. 8, and the rectangular wave control is switched to the PWM control.

  At this time, in PWM control, the voltage phase φv also increases (decreases) as the voltage command value increases (decreases). On the other hand, in the rectangular wave control, since the magnitude of the voltage command value is fixed at VH, only the voltage phase φv changes. The voltage phase φv increases, ie, changes in the advance direction when in the acceleration direction, and decreases, that is, changes in the return angle direction, when in the deceleration direction.

Therefore, when the direction of change of voltage phase φv changes in the direction of arrow AR31 in FIG. 8, that is, in the acceleration direction, the current phase for switching from rectangular wave control to PWM control as indicated by point P21 in FIG. to set the threshold value φ _th small (φ _th1 <φ _th0). On the other hand, when the change direction of the voltage phase φv changes in the direction of the arrow AR32 in FIG. 8, that is, in the deceleration direction, the current phase threshold _φth is set to be large as indicated by a point P22 in FIG. (Φ _th2 > φ _th0 ).

In this way, by considering the change direction of the voltage phase φv in the rectangular wave control, by changing the threshold value φ _th of the current phase for switching the control mode, the rectangular wave control is performed again after switching to the PWM control. When there is a high possibility of switching, priority is given to chattering prevention, and when there is a high possibility that PWM control will continue after switching to PWM control, torque fluctuation can be suppressed.

  8 is a diagram in the case where the system voltage VH has a specific value. If the system voltage VH adjusted by the converter 120 in FIG. 1 varies, the radius of the circumference in FIG. 8 varies. End up. Then, even if the operating point of the vehicle is the same, the voltage phase φv may change. Therefore, the mode switching control described above is more preferably performed when the magnitude (absolute value) of the temporal change (ΔVH / Δt) of the system voltage VH (hereinafter also referred to as “voltage command rate”) is small. It is desirable to apply when the command rate is zero.

As for the change in the voltage phase .phi.v, gently accelerate or even when such deceleration, the thus changing the threshold phi _th current phase as described above, the threshold phi _th itself frequently It will change, and it may end up hindering control stability. Therefore, it is desirable to apply the mode switching control when the temporal change (Δφv / Δt) of voltage phase φv (hereinafter also referred to as “voltage phase rate”) is large to some extent.

  FIG. 10 is a flowchart for illustrating the details of the mode switching control process executed by ECU 300 in the present embodiment. Each step in the flowchart shown in FIG. 10 and FIG. 11 described later is realized by executing a program stored in advance in ECU 300 at a predetermined cycle. Alternatively, for some steps, it is also possible to construct dedicated hardware (electronic circuit) and realize processing.

  Referring to FIGS. 1 and 10, ECU 300 determines in step (hereinafter abbreviated as S) 100 whether or not the current control mode is the PWM control mode.

  If the control mode is the PWM control mode (YES in S100), the process proceeds to S110, and ECU 300 performs, for example, the following based on voltage command values Vd #, Vq # and system voltage VH according to the PWM control mode. The modulation factor FM is calculated by the equation (1).

FM = (Vd # ² + Vq # ² ) ^1/2 / VH (1)
In S120, ECU 300 determines whether or not the modulation factor obtained in S110 is 0.78 or more.

  When the modulation factor is equal to or greater than 0.78 (YES in S120), ECU 300 determines that an appropriate AC voltage cannot be generated in the PWM control mode, proceeds to S170, and performs rectangular wave control mode. Select.

  If the modulation factor is smaller than 0.78 (NO in S120), the process proceeds to S130, and ECU 300 continuously selects the PWM control mode.

  When PWM control mode is selected, ECU 300 further determines which of sine wave PWM control and overmodulation PWM control is applied in S140. This determination can be performed by comparing the modulation factor FM with a predetermined reference value (for example, 0.61 which is the theoretical maximum value of the modulation factor of the sine wave PWM control). When the modulation rate is equal to or less than the reference value, sine wave PWM control is applied, and when the modulation rate is greater than the reference value, overmodulation PWM control is applied.

On the other hand, when the current control mode is the rectangular wave control mode (NO in S100), the process proceeds to S150, and ECU 300 starts the PWM from the rectangular wave control mode as described in more detail in FIG. A current phase threshold φ _th for switching to the control mode is set.

Then, ECU 300, at S160, the current command value Id # in the rectangular wave control, Iq absolute value of the current phase phi _{i #} of # is either less or not than the absolute value of the set threshold phi _th at S150 Determine.

If the absolute value of current phase φ _{i #} is smaller than the absolute value of threshold value φ _th (YES in S160), ECU 300 determines that the control mode needs to be switched from the rectangular wave control mode to the PWM control mode. . Then, the process proceeds to S130, and ECU 300 selects the PWM control mode.

On the other hand, when the absolute value of current phase φ _{i #} is equal to or larger than the absolute value of threshold value φ _th (NO in S160), the process proceeds to S170 and ECU 300 continuously selects the rectangular wave control mode. To do.

  FIG. 11 is a flowchart for explaining details of the process in step S150 of FIG.

  Referring to FIGS. 1 and 11, when it is determined in S100 of FIG. 10 that the current control mode is rectangular wave control, ECU 300 determines in S151 the voltage command rate (ΔVH / Δt) and the voltage phase. The rate (Δφv / Δt) is acquired. The voltage command rate and the voltage phase rate may be calculated, for example, as changes from the system voltage VH and the voltage phase φv in the previous control cycle, respectively. Or it is good also as a moving average of each value calculated by the latest several control cycle.

  In S152, ECU 300 determines whether or not the absolute value of the voltage command rate is smaller than a predetermined reference value α (α> 0) (| ΔVH / Δt | <α).

If the absolute value of the voltage command rate is equal to or greater than a predetermined reference value α (NO in S152), the process proceeds to S157, and ECU 300 sets φ as the current phase threshold value _φth , which is the default value φ Select _th0 .

  If the absolute value of voltage command rate is smaller than predetermined reference value α (YES in S152), the process proceeds to S153, and ECU 300 then sets voltage phase rate to predetermined value β1 (β1 <0). It is determined whether or not it is smaller, that is, whether or not the operating point has shifted to a deceleration direction with a certain size.

If voltage phase rate is smaller than predetermined value β1 (YES in S153), the process proceeds to S155, and ECU 300 sets current phase threshold value φ _th as a point in FIG. 9 to suppress torque fluctuation. Φ _th2 (φ _th2 > φ _th0 ) that reduces (narrows) the phase difference from the current phase of P1 is selected.

  On the other hand, when the voltage phase rate is equal to or higher than predetermined value β1 (NO in S153), the process proceeds to S154, and ECU 300 determines whether or not the voltage phase rate is greater than predetermined value β2 (β2> 0), that is, Then, it is determined whether or not the operating point has transitioned in the acceleration direction with a certain size.

If voltage phase rate is greater than predetermined value β2 (YES in S154), the process proceeds to S156, and ECU 300 sets current phase threshold value φ _th as a current phase threshold value φ _th to prevent chattering of control mode switching. 9 selects φ _th1 (φ _th1 <φ _th0 ) that increases (expands) the phase difference from the current phase at point P1.

On the other hand, when the voltage phase rate is equal to or less than predetermined value β2 (NO in S154), voltage phase rate is β1 ≦ Δφv / Δt ≦ β2, and ECU 300 determines that it is in a steady state or a slow acceleration / deceleration state, The process proceeds to S157, and the default value φ _th0 is selected as the current phase threshold φ _th .

After setting current phase threshold value φ _th by such processing, ECU 300 proceeds to S160 in FIG. 10 to determine whether or not to switch the control mode from rectangular wave control to PWM control as described above. To do.

  Note that the magnitudes (absolute values) of β1 and β2 may be the same value or different values.

  By performing control according to the above processing, chattering is prevented while switching the control mode frequently during the switching of the control mode from rectangular wave control to PWM control in the motor drive control system. In a state where it is difficult to occur, torque fluctuation at the time of control mode switching can be reduced. Thereby, control stability in switching of the control mode from rectangular wave control to PWM control can be improved.

  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.

  DESCRIPTION OF SYMBOLS 10 Vehicle, 105 DC voltage generation part, 100 Motor drive control system, 110 DC power supply, 120 Converter, 130 Voltage sensor, 140 Inverter, 141 U-phase upper / lower arm, 142 V-phase upper / lower arm, 143 W-phase upper / lower arm, 150, 170 Voltage sensor, 160, 240 Current sensor, 200 AC motor, 210 Drive wheel, 250 Rotation angle sensor, 300 ECU, 310 PWM control unit, 312 Sine wave PWM control unit, 314 Overmodulation PWM control unit, 320 Rectangular wave control unit, 330 Control mode selection unit, C1, C2 capacitor, D1-D8 diode, L1 reactor, NL1 ground line, PL1, PL2 power line, Q1-Q8 switching element, SR1, SR2 system relay.

Claims (9)

A motor drive control system for driving an AC motor,
An inverter for controlling the drive voltage of the AC motor;
A control device for controlling the inverter;
The inverter has a rectangular wave control mode for driving the AC motor by controlling a voltage phase of a rectangular wave voltage applied to the AC motor, and a comparison between an AC voltage command for operating the AC motor and a carrier wave. Controlled by a pulse width modulation control mode for driving the AC motor by performing pulse width modulation control based on
The control device switches from the rectangular wave control mode to the pulse width modulation control mode in response to the current phase applied to the AC motor reaching a threshold during execution of the rectangular wave control mode. Execute switching
The said control apparatus is a motor drive control system which changes the said threshold value based on the change of the voltage phase applied to the said AC motor during execution of the said rectangular wave control mode.   When the voltage phase is changing in the acceleration direction, the control device is configured so that switching from the rectangular wave control mode to the pulse width modulation control mode is slower than when the voltage phase does not change. The motor drive control system according to claim 1, wherein the threshold value is changed.   The control device is configured so that when the voltage phase is changing in the deceleration direction, switching from the rectangular wave control mode to the pulse width modulation control mode is faster than when the voltage phase is not changing. The motor drive control system according to claim 1, wherein the threshold value is changed.   4. The motor drive control system according to claim 2, wherein the control device changes the threshold value when the magnitude of the temporal change in the voltage phase is larger than a first reference value. 5.   The said control apparatus prohibits the change of the said threshold value when the magnitude | size of the time change of the voltage command value applied to the said AC motor is smaller than a 2nd reference value. A motor drive control system according to claim 1.   The motor drive control system according to claim 1, wherein the voltage phase is determined based on a d-axis voltage command value with respect to a q-axis voltage command value with respect to a voltage command value applied to the AC motor.   The motor drive control system according to claim 1, wherein the current phase is determined based on a d-axis current value with respect to a q-axis current value of a current flowing in the AC motor. A power storage device;
The AC motor;
A vehicle comprising the motor drive control system according to claim 1. A control method of a motor drive control system for driving an AC motor by an inverter,
Selecting a rectangular wave control mode for driving the AC motor by controlling the voltage phase of the rectangular wave voltage applied to the AC motor;
Selecting a pulse width modulation control mode for driving the AC motor by performing a pulse width modulation control based on a comparison between an AC voltage command for operating the AC motor and a carrier wave;
Switching from the rectangular wave control mode to the pulse width modulation control mode in response to the current phase applied to the AC motor reaching a threshold during execution of the rectangular wave control mode;
And a step of changing the threshold value based on a change in a voltage phase applied to the AC motor during execution of the rectangular wave control mode.

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