JP2010124566A - Device for controlling ac electric motor, and electric vehicle mounted with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve control stability by preventing a delay in the switching of rectangular wave voltage control to PWM control, in a device for controlling an AC electric motor. <P>SOLUTION: In the device for controlling the AC electric motor M1, a sampling current Isw is used for determining the necessity of the switching of the rectangular wave voltage control to the PWM control at timing at which an amplitude of a motor current is enlarged compared with a fundamental wave current, and a phase of the current is set at a delay side compared with the fundamental wave current. By this arrangement, the switching of the rectangular wave voltage control to the PWM control can be performed at an early stage, thereby the control mode switching of the rectangular wave voltage control to the PWM control becomes possible while current deviation is small. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an AC motor control device and an electric vehicle equipped with the control device, and more specifically, an AC motor to which rectangular wave voltage control and pulse width modulation (PWM) control are applied. Regarding control.

  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 rectangular wave voltage control is applied.

  In Japanese Patent Laid-Open No. 2005-218299 (Patent Document 1), when operating with rectangular wave voltage control, the absolute value | φi | of the actual current phase supplied to the AC motor is the absolute value of the predetermined switching current phase. When the value is less than | φ0 |, control for switching from rectangular wave voltage control to PWM control is described.

Further, according to Japanese Patent Laid-Open No. 2006-320039 (Patent Document 2), if the motor rotation speed changes suddenly when the rectangular wave voltage control or the overmodulation PWM control is applied, the reduction in the feedback control response is covered. Describes control for changing the voltage command value of the output voltage of the converter (that is, the input voltage of the inverter) in accordance with the change ratio of the motor rotation speed.
JP 2005-218299 A JP 2006-320039 A

  In overmodulation PWM control, in current feedback control for compensating for current deviations in the d-axis and q-axis, the waveform of the motor current is distorted, so it is necessary to appropriately deal with harmonic components of the current to improve controllability. . Further, in the control configuration in which the rectangular wave voltage control and the PWM control are switched according to the state of the AC motor, overmodulation PWM control is generally used when switching from the rectangular wave voltage control to the PWM control. It is desirable to reduce the current deviation at the time of mode switching.

  In the rectangular wave voltage control for controlling the voltage phase, the current is not directly feedback-controlled. Therefore, when the control mode is switched to the PWM control that is the current feedback control, a current deviation of the motor current is likely to occur with respect to the current command. Since the rectangular wave voltage control is used in a region where the motor rotation speed is high, it is necessary to process the control mode switching with a short control cycle.

  However, since the control cycle is limited by the capability of the control device, even if the motor current used for determining whether or not switching is required is not delayed and the motor current without delay is used, the switching of the control mode may be delayed. appear.

  When such a delay in switching the control mode occurs, the motor current is disturbed in the PWM control and current followability deteriorates by switching from the rectangular wave voltage control to the PWM control mode with a large current deviation. There is a possibility that. Therefore, when switching from rectangular wave voltage control to PWM control, it is necessary to determine whether switching is necessary so that the control mode is switched at an appropriate timing in consideration of suppressing disturbance of the motor current. .

  The present invention has been made to solve such problems, and an object of the present invention is to prevent a switching delay from rectangular wave voltage control to PWM control in a control device for an AC motor. It is to increase control stability.

  An AC motor control device of the present invention is an AC motor control device in which an applied voltage is controlled by an inverter, and includes a current detector, a rectangular wave voltage control unit, a pulse width modulation control unit, and a control mode selection unit. And. The current detector detects a motor current flowing between the inverter and the AC motor. The rectangular wave voltage control unit generates an inverter control command so that a rectangular wave voltage phase-controlled so as to operate the AC motor according to the torque command is applied to the AC motor. The pulse width modulation control unit generates an inverter control command by pulse width modulation control based on a comparison between the carrier wave and an AC voltage command for operating the AC motor in accordance with the torque command. Further, the control mode selection unit is configured to select one of rectangular wave voltage control by the rectangular wave voltage control unit and pulse width modulation control by the pulse width modulation control unit according to the operating state of the AC motor. Yes. Furthermore, the rectangular wave voltage control unit has the current detector at a first predetermined timing at which the amplitude and phase of the motor current are larger than those of the fundamental wave component, which is the fundamental wave component, and the phase is delayed. And a pulse width from the rectangular wave voltage control by the rectangular wave voltage control unit based on the first current sampled at the first predetermined timing and the current extraction unit configured to sample the motor current detected by A switching determination unit configured to determine whether or not switching to pulse width modulation control by the modulation control unit is necessary.

  According to the above AC motor control device, whether or not the switching from the rectangular wave voltage control to the PWM control is necessary is such that the amplitude and phase of the motor current are larger than the fundamental current and the phase is on the lag side. This can be determined using the current at the timing. Switching from rectangular wave voltage control to PWM control is made early by determining whether or not switching is necessary using a current having an amplitude and phase that makes it easy to determine that switching from rectangular wave voltage control to PWM control is necessary. Can be implemented. As a result, an increase in current deviation at the time of control mode switching can be suppressed, so that disturbance of motor current is suppressed in PWM control after switching. Thereby, it becomes possible to improve control stability at the time of switching from rectangular wave voltage control to PWM control.

  Preferably, the switching determination unit determines whether or not switching from the rectangular wave voltage control to the pulse width modulation control is performed based on the first current when the torque command value to the inverter is equal to or greater than a predetermined first torque reference value. Judgment is made.

  With such a configuration, in the high torque region where the motor current is relatively large, it is possible to prevent the switching delay of the control mode by using the first current to determine whether switching is necessary. As a result, current disturbance is likely to occur because the motor current becomes large, and in the high torque region where the influence on the electric equipment such as the motor is large when current disturbance occurs, the rectangular wave voltage control to PWM Control stability at the time of switching to control can be improved.

  Alternatively, preferably, the current extraction unit is configured to further sample the motor current at a second predetermined timing when the amplitude and phase of the motor current are smaller than the fundamental current and the phase is advanced. When the torque command value is less than the predetermined second torque reference value, the switching determination unit replaces the determination of necessity of switching based on the first current with the second sampled at the second predetermined timing. On the basis of the current, it is determined whether or not switching from rectangular wave voltage control to pulse width modulation control is necessary.

  By adopting such a configuration, in the low torque region, the second current at a timing such that the amplitude and phase of the motor current is smaller than the fundamental wave current and the phase is on the leading side. It is possible to determine whether or not switching is necessary. In the low torque region where the motor current is relatively small, when the first current is used, chattering in which switching between the rectangular wave voltage control and the PWM control is frequently repeated may occur. Therefore, the occurrence of chattering can be suppressed by determining whether or not switching is necessary using a current that is difficult to determine that switching from rectangular wave voltage control to PWM control is necessary.

  Preferably, the switching determination unit determines whether or not switching from rectangular wave voltage control to pulse width modulation control is necessary based on the magnitude of the first current. Preferably, the switching determination unit determines whether or not switching from the rectangular wave voltage control to the pulse width modulation control is necessary based on the phase of the first current.

  By adopting such a configuration, it is possible to determine whether or not switching from rectangular wave voltage control to PWM control is necessary according to the magnitude or phase of the first current, thereby preventing a delay in switching the control mode. Control stability at the time of switching from rectangular wave voltage control to PWM control can be enhanced.

  Preferably, the inverter includes a plurality of switching elements that perform power conversion in accordance with a control command, and the first current is a motor current at a timing corresponding to each drive switching timing of the plurality of switching elements of the inverter. is there.

  According to such a configuration, the motor current is sampled as the first current corresponding to the drive switching timing of the switching element of the inverter, which is the timing at which the voltage applied to the AC motor that is the inductive load changes in a stepped manner. can do. Therefore, the first current can be obtained such that the amplitude and phase of the motor current are relatively larger than the fundamental current and the phase is delayed.

  Further preferably, when the torque command value of the inverter is equal to or greater than the first torque reference value, the switching determination unit determines whether or not switching is necessary based on the magnitude of the first current, and the torque command value is equal to the second torque command value. If it is less than the torque reference value, the necessity of switching is determined based on the magnitude of the second current.

  With such a configuration, in the region where the torque command value to the inverter is high torque, it is determined whether or not switching from the rectangular wave voltage control to the PWM control is necessary according to the magnitude of the first current, and the low torque In this area, it is possible to determine whether or not switching from the rectangular wave voltage control to the PWM control is necessary according to the magnitude of the second current. The first current is a current that has a relatively large current amplitude as compared with the fundamental wave current, and is thus easily determined to be switched from the rectangular wave voltage control to the PWM control. On the other hand, the second current is a current that makes it difficult to determine that switching from the rectangular wave voltage control to the PWM control is necessary because the current amplitude is relatively small compared to the fundamental wave current. Therefore, the switching of the control mode from the rectangular wave voltage control to the PWM control is performed by switching the control mode early in the high torque region and suppressing the chattering generated by promoting the switching of the control mode in the low torque region. Control stability at the time can be improved.

  Alternatively, preferably, when the torque command value to the inverter becomes equal to or greater than the first torque reference value, the switching determination unit determines whether or not switching is necessary based on the phase of the first current, and the torque command value is When it is less than the second torque reference value, the necessity of switching is determined based on the phase of the second current.

  With such a configuration, it is determined whether or not switching from rectangular wave voltage control to PWM control is necessary based on the phase of the first current in the high torque region, and based on the phase of the second current in the low torque region. It is possible to determine whether or not switching from rectangular wave voltage control to PWM control is necessary. The first current is a current that easily determines that switching from the rectangular wave voltage control to the PWM control is necessary because the current phase is relatively delayed compared to the reference wave current. On the other hand, the second current is such that the current phase is relatively advanced compared to the fundamental current, so that it is difficult to determine that switching from rectangular wave voltage control to PWM control is necessary. . Therefore, by using such a phase of the current for determining whether or not to switch the control mode, the control mode is quickly switched in the high torque region, while the switching of the control mode is facilitated in the low torque region. By suppressing chattering to be performed, control stability at the time of switching from rectangular wave voltage control to PWM control can be improved.

  Alternatively, preferably, the inverter includes a plurality of switching elements that perform power conversion according to a control command, and the first current is a motor current at a timing corresponding to each drive switching timing of the plurality of switching elements of the inverter, The second current is a motor current at an intermediate timing between the sampling timings of the first current.

  According to such a configuration, the motor current is sampled as the first current corresponding to the drive switching timing of the switching element of the inverter, which is the timing at which the voltage applied to the AC motor, which is an inductive load, changes stepwise. By doing so, it is possible to obtain a current in which the amplitude and phase of the motor current are relatively larger than the fundamental current and the phase is on the lag side. Further, by sampling the motor current at the intermediate timing between the sampling timings of the first current as the second current, the amplitude and phase of the motor current are relatively smaller than the fundamental wave current and the phase Can be obtained such that the current becomes the leading side.

  Alternatively, preferably, the electric vehicle according to the present invention is equipped with an AC motor configured to generate a vehicle driving force and the AC motor control device as described above.

  By adopting such a configuration, it is possible to improve control stability when switching from rectangular wave voltage control to PWM control in an electric vehicle equipped with the above-described AC motor control device.

  According to the present invention, control stability can be improved by preventing a delay in switching from rectangular wave voltage control to PWM control.

  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.

[Embodiment 1]
(General configuration of motor control)
FIG. 1 is an overall configuration diagram of a motor drive control system to which an AC motor control device according to an embodiment 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.

  For example, AC electric motor M1 generates torque for driving drive wheels of an electric vehicle (referred to as a vehicle that generates vehicle driving force by electric energy such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle). This is an electric motor for driving. 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. 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 10 # includes a DC power supply B, system relays SR1 and SR2, a smoothing capacitor C1, and a converter 12.

  The DC power supply B is typically constituted by a secondary battery such as nickel metal hydride or lithium ion, or a power storage device such as an electric double layer capacitor. The DC voltage Vb output from the DC power supply B and the input / output DC current Ib are detected by the voltage sensor 10 and the current sensor 11, respectively.

  System relay SR 1 is connected between the positive terminal of DC power supply B and power line 6, and system relay SR 1 is connected between the negative terminal of DC power supply B and ground line 5. System relays SR1 and SR2 are turned on / off by signal SE from control device 30.

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

  In the embodiment of the present invention, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, or a power bipolar transistor is used as a power semiconductor switching element (hereinafter simply referred to as “switching element”). Etc. can be used. Anti-parallel diodes D1, D2 are arranged for switching elements Q1, Q2. Reactor L1 is connected between a connection node of switching elements Q1 and Q2 and power line 6. Further, the smoothing capacitor C 0 is connected between the power line 7 and the ground line 5.

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

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

  Converter 12 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 12 boosts DC voltage Vb supplied from DC power supply B to DC voltage VH (hereinafter, this DC voltage corresponding to the input voltage to inverter 14 is also referred to as “system voltage”). This step-up operation is performed by supplying the electromagnetic energy stored in reactor L1 during the ON period of switching element Q2 to power line 7 via switching element Q1 and antiparallel diode D1.

  Further, converter 12 steps down DC voltage VH to DC voltage Vb during the step-down operation. This step-down operation is performed by supplying the electromagnetic energy accumulated in the reactor L1 during the ON period of the switching element Q1 to the power line 6 via the switching element Q2 and the antiparallel diode D2. The voltage conversion ratio (ratio of VH and Vb) 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. If switching elements Q1 and Q2 are fixed to ON and OFF, respectively, VH = Vb (voltage conversion ratio = 1.0) can be obtained.

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

  When the torque command value of AC motor M1 is positive (Trqcom> 0), inverter 14 responds to switching control signals S3 to S8 from control device 30 when a DC voltage is supplied from smoothing capacitor C0. AC motor M1 is driven so as to output a positive torque by converting a DC voltage into an AC voltage by switching operation of elements Q3 to Q8. Further, when the torque command value of AC electric motor M1 is zero (Trqcom = 0), inverter 14 converts the DC voltage to the AC voltage by the switching operation in response to switching control signals S3 to S8, and the torque is zero. The AC motor M1 is driven so that Thus, AC 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, torque command value Trqcom of AC electric motor M1 is set to a negative value (Trqcom <0). In this case, the inverter 14 converts the AC voltage generated by the AC motor M1 into a DC voltage by a switching operation in response to the switching control signals S3 to S8, and converts the converted DC voltage (system voltage) to the smoothing capacitor C0. To the converter 12 via 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 motor current MCRT flowing through AC electric motor M <b> 1 and outputs the detected motor current to control device 30. Since the sum of instantaneous values of the three-phase currents iu, iv, and iw is zero, the current sensor 24 has a motor current for two phases (for example, a V-phase current iv and a W-phase current iw) as shown in FIG. It is sufficient to arrange it so as to detect.

  The rotation angle sensor (resolver) 25 detects the rotation angle θ of the AC electric motor M1 and sends the detected rotation angle θ 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. Note that 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 (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 a representative function, the control device 30 includes the input torque command value Trqcom, the DC voltage Vb detected by the voltage sensor 10, the DC current Ib detected by the current sensor 11, and the system voltage detected by the voltage sensor 13. Based on VH, motor currents iv and iw from current sensor 24, rotation angle θ from rotation angle sensor 25, etc., AC motor M1 outputs torque according to torque command value Trqcom by a control method described later. The operations of the converter 12 and the inverter 14 are controlled. That is, switching control signals S1 to S8 for controlling converter 12 and inverter 14 as described above are generated and output to converter 12 and inverter 14.

  During the boost operation of converter 12, control device 30 performs feedback control of system voltage VH, and generates switching control signals S1 and S2 so that system voltage VH matches the voltage command value.

  When control device 30 receives a signal RGE indicating that the electric vehicle has entered the regenerative braking mode from an external control device, switching control signal S3 converts the AC voltage generated by AC motor M1 into a DC voltage. ~ S8 are generated and output to the inverter 14. Thereby, the inverter 14 converts the AC voltage generated by the AC motor M <b> 1 into a DC voltage and supplies it to the converter 12.

  Further, when control device 30 receives signal RGE indicating that the electric vehicle has entered the regenerative braking mode from an external control device, control device 30 generates switching control signals S1 and S2 so as to step down the DC voltage supplied from inverter 14. And output to the converter 12. As a result, the AC voltage generated by AC motor M1 is converted to a DC voltage, stepped down, and supplied to DC power supply B.

(Description of control mode)
The control of AC motor M1 by control device 30 will be described in further detail.

  FIG. 2 is a diagram schematically illustrating a control mode of AC electric motor M1 in the motor drive system according to the embodiment of the present invention.

  As shown in FIG. 2, in the motor drive control system 100 according to the embodiment of the present invention, three control modes are switched and used for control of the AC motor M1, that is, power conversion in the inverter.

  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 sinusoidal 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 applied voltage to the AC motor M1 (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, in this specification, the ratio of the fundamental component (effective value) of the motor applied voltage (line voltage) to the DC link voltage (that is, the system voltage VH) of the inverter 14 is referred to as “modulation rate”.

  In the sine wave PWM control, since the amplitude of the voltage command of the sine wave is in the range below the carrier wave amplitude, the line voltage applied to the AC motor M1 becomes a sine wave. Also proposed is a control method in which a voltage command is generated by superimposing a 3n-order harmonic component (n: a natural number, typically n = 1 third-harmonic) on a sine wave component in the range below the carrier wave amplitude. ing.

  On the other hand, in the rectangular wave voltage control, one pulse of a rectangular wave having 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 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 overmodulation PWM control, since the amplitude of the voltage command (sine wave component) is greater than the carrier wave amplitude, the line voltage applied to AC motor M1 is not a sine wave but a distorted voltage.

  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 voltage of the motor. On the other hand, there is a limit value (VH maximum voltage) in the boosted voltage by converter 12, that is, system voltage VH.

  Therefore, a PWM control mode by sine wave PWM control or overmodulation PWM control that controls the amplitude and phase of the motor applied voltage (AC) by feedback of the motor current according to the operating state of AC motor M1, and rectangular wave voltage One of the control modes is selectively applied. In the rectangular wave voltage control, since the amplitude of the motor applied voltage is fixed, the torque control is executed by the phase control of the rectangular wave voltage pulse based on the deviation between the actual torque value and the torque command value.

FIG. 3 shows the correspondence between the operating state of AC electric motor M1 and the control mode described above.
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 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 of the control modes shown in FIG. 2 is used is basically determined within the range of the modulation rate that can be realized.

(Configuration of control device)
FIG. 4 is a functional block diagram illustrating a control configuration of the AC motor control device 30 according to the present embodiment. Each functional block described in the block diagram described below including FIG. 4 is realized by hardware or software processing by the control device 30.

  Referring to FIG. 4, control device 30 includes a PWM control unit 280, a rectangular wave voltage control unit 400, and a control mode selection unit 490. The PWM control unit 280 includes a sine wave PWM control unit 200 and an overmodulation PWM control unit 201.

  The sine wave PWM control unit 200 receives the torque command value Trqcom, the motor currents iv and iw detected by the current sensor 24, and the rotation angle θ detected by the rotation angle sensor 25. The sine wave PWM control unit 200 then converts 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 detected by the current sensor 24 into the d-axis and q-axis. The deviation is calculated. By performing PI calculation on this current deviation, voltage command values Vd # and Vq # to be applied to the inverter 14 are generated.

  The sine wave PWM control unit 200 converts the voltage command values Vd # and Vq # into three phases U, V, and W, and performs switching control for driving the inverter 14 based on the obtained voltage command values for each phase. Command values S3 to S8 are generated. Further, the generated voltage command values Vd #, Vq # are output to the control mode selection unit 490. Thus, the sine wave PWM control unit 200 controls the AC motor M1 to generate the target torque by performing feedback control of the motor current detected by the current sensor 24.

  The overmodulation PWM control unit 201 receives the torque command value Trqcom, the motor currents iv and iw detected by the current sensor 24, and the rotation angle θ detected by the rotation angle sensor 25, and receives sinusoidal PWM control. Switching control command values S <b> 3 to S <b> 8 for driving the inverter 14 are generated by current feedback control similar to that of the unit 200. Further, overmodulation PWM control section 201 outputs generated voltage command values Vd # and Vq # to control mode selection section 490. Note that, as described above, the overmodulation PWM control unit 201 has a function of correcting the voltage amplitude in the sine wave PWM, and can increase the fundamental wave component of the voltage command value.

  The rectangular wave voltage control unit 400 receives the torque command value Trqcom, the motor currents iv and iw detected by the current sensor 24, and the rotation angle θ detected by the rotation angle sensor 25, and detects each phase detected. An estimated torque value is calculated from the motor current and the voltage applied to each phase of AC motor M1. Then, the rectangular wave voltage control unit 400 sets a voltage phase to be applied to the inverter 14 based on a deviation between the estimated torque value and the torque command value Trqcom, and the switching control command values S3 to S8 for driving the inverter 14 based on the voltage phase. Is generated. In this way, the rectangular wave voltage control unit 400 controls the AC motor M1 to generate the target torque by controlling the phase of the rectangular wave voltage applied to the AC motor M1 by torque feedback.

  Further, the rectangular wave voltage control unit 400 needs to switch from rectangular wave voltage control to PWM control based on the motor currents iv and iw detected by the current sensor 24 and the rotation angle θ detected by the rotation angle sensor 25. The control mode switching flag FLG is output to the control mode selection unit 490 according to the determination. Details of these functions will be described later.

  Control mode selection unit 490 detects system voltage VH, voltage command values Vd # and Vq # from PWM control unit 280, motor currents iv and iw detected by current sensor 24, and rotation angle sensor 25. And the control mode switching flag FLG from the rectangular wave voltage control unit 400 are input. Control mode selecting unit 490 determines whether or not switching from the PWM control mode to the rectangular wave voltage control mode is necessary based on the modulation factor calculated from system voltage VH and voltage command values Vd # and Vq #. In accordance with the control mode switching flag FLG from the rectangular wave voltage control unit 400, switching from the rectangular wave voltage control mode to the PWM control mode is performed.

(Control configuration of rectangular wave voltage control)
FIG. 5 is a block diagram illustrating a motor control configuration by rectangular wave voltage control that is executed when the rectangular wave voltage control mode is applied.

  Referring to FIG. 5, rectangular wave voltage control unit 400 includes power calculation unit 410, torque calculation unit 420, PI calculation unit 430, rectangular wave generator 440, signal generation unit 450, and current extraction unit 460. A storage unit 470 and a switching determination unit 480.

  The power calculation unit 410 supplies to the motor according to the following equation (1) based on each phase current obtained from the output of the current sensor 24 and each phase (U phase, V phase, W phase) voltage Vu, Vv, Vw. Electric power (motor electric power) Pmt is calculated.

Pmt = iu · Vu + iv · Vv + iw · Vw (1)
The torque calculation unit 420 uses the motor power Pmt obtained by the power calculation unit 410 and the angular velocity ω calculated from the rotation angle θ of the AC electric motor M1 detected by the rotation angle sensor 25, according to the following equation (2). Estimated value Tq is calculated.

Tq = Pmt / ω (2)
Torque deviation ΔTq (ΔTq = Trqcom−Tq) with respect to torque command value Trqcom is input to PI calculation unit 430. PI calculation unit 430 performs PI calculation with a predetermined gain on torque deviation ΔTq to obtain a control deviation, and sets phase φv of rectangular wave voltage according to the obtained control deviation. Specifically, the PI calculation unit 430 advances the voltage phase when the torque is insufficient when the positive torque is generated (Trqcom> 0), while delaying the voltage phase when the torque is excessive and when the negative torque is generated (Trqcom <0). While the voltage phase is delayed when the torque is insufficient, the voltage phase is advanced when the torque is excessive.

  Note that, when a phase change prohibition signal CSTP input from a switching determination unit 480 described later is ON, the PI calculation unit 430 prohibits the change of the voltage phase φv and holds the voltage phase φv set in the immediately preceding control cycle. To do.

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

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

  In addition, during power calculation (equation (1)) in the power calculation unit 410, filter processing for removing distortion components from the detected motor current (iv, iw) is also executed.

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

  The current extraction unit 460 determines the switching control commands S3 to S3 of the inverter 14 from each phase current obtained from the V phase current iv and the W phase current iw by the current sensor 24 and the rotation angle θ of the AC motor M1 by the rotation angle sensor 25. The motor current Isw at the switching timing 500 (FIG. 6) to be described later with respect to S8 is sampled.

  Similarly, the current extraction unit 460 samples the motor current Imid at the intermediate timing of the switching timing, and outputs the sampled motor currents Isw and Imid to the switching determination unit 480.

  The storage unit 470 stores in advance a current reference value, a switching phase reference value, a torque reference value, and the like that are used for determination by the switching determination unit 480. The reference value may be a fixed value or may be set by referring to a map set in advance through experiments or the like so as to be a variable value corresponding to the sampled current value.

  The switching determination unit 480 performs d-q axis conversion on the motor currents Isw and Imid sampled in the current extraction unit 460 using the rotation angle θ of the AC motor M1 by the rotation angle sensor 25. Then, the switching determination unit 480 sets the q-axis current reference value for determining the necessity of switching stored in the storage unit 470 based on the d-axis current value of the motor current Isw. Then, the switching determination unit 480 compares the q-axis current value of the motor current Isw and the q-axis current reference value to determine whether the q-axis current value is equal to or greater than the reference value, thereby determining the rectangular wave voltage. It is determined whether or not switching from control to PWM control is necessary.

  When the q-axis current value is equal to or greater than the reference value, the switching determination unit 480 turns on the control mode switching flag FLG to the control mode selection unit 490 and outputs it, and turns on the phase change prohibition signal CSTP to the PI calculation unit 430. Output. By this phase change prohibition signal CSTP, the PI calculation unit 430 holds the voltage phase φv used in the previous control cycle. Thus, the voltage phase φv is not changed until the switching from the rectangular wave voltage control mode to the PWM control mode is completed.

  On the other hand, when the q-axis current value is less than the reference value, switching determination unit 480 outputs control mode switching flag FLG and phase change prohibition signal CSTP as OFF. Thereby, the rectangular wave voltage control unit 400 performs torque feedback control using the torque estimation value Tq estimated by the torque calculation unit 420.

  Here, the operation of the control mode selection unit 490 is performed as part of a main loop that controls the entire AC motor control. On the other hand, since the rectangular wave voltage control mode is executed in the high rotational speed region of the AC motor M1, the rectangular wave voltage phase control period by the rectangular wave voltage control unit 400 is necessarily greater than the control period of the main loop. Shorter. Further, in order to obtain sufficient control response in such a high rotation speed region, rectangular wave voltage phase control is executed by subdividing one period (360 (deg)) of the electrical angle. For this reason, the rectangular wave voltage control unit 400 determines whether the switching from the rectangular wave voltage control to the PWM control is necessary or not and the control mode selection unit 490 completes the switching of the control mode. The control by the control unit 400 is executed a plurality of times.

  Therefore, the voltage phase φv between the time when the rectangular wave voltage control unit 400 determines whether or not the switching from the rectangular wave voltage control to the PWM control is necessary and the time when the control mode selection unit 490 actually completes the switching of the control mode. If there is a change, a voltage more than necessary may be applied to the AC motor M1 or the current may be instantaneously disturbed at the timing when the control mode is actually switched. In order to prevent these, the rectangular wave voltage control unit 400 prohibits the change of the voltage phase φv until the completion of the switching of the control mode.

(Explanation about sampling current)
Next, the sampling current in the current extraction unit 460 will be described with reference to FIGS.

  The difference in the property of the motor current due to the difference in sampling timing during the rectangular wave voltage control will be described with reference to FIG.

  The lower part of FIG. 6 is a diagram illustrating an ON / OFF driving state of the switching element of each UVW phase of the inverter 14. For example, one of the switching elements of the UVW phase is turned on or off every electrical angle 60 (deg). The The timing at which the switching element is turned on / off is referred to as switching timing 500, and the intermediate timing between the switching timings is referred to as intermediate timing 510.

  The waveforms of the upper and middle symbols W10 in FIG. 6 show examples of one-phase (for example, U-phase) motor current waveforms.

  In the upper part of FIG. 6, an example of current sampling at the switching timing 500 is shown. At the switching timing 500, the surge current generated when the switching element is turned on or off tends to have a relatively large amplitude relative to the fundamental current of the motor current. Also, the current phase tends to be relatively delayed with respect to the phase of the fundamental current. The current waveform based on these sampling current values is W11.

  On the other hand, the middle part of FIG. 6 shows an example of current sampling at the intermediate timing 510. The current waveform indicated by the symbol W12 is a current waveform based on the motor current value sampled at the intermediate timing 510. At the intermediate timing 510, no surge current is generated as at the switching timing 500, so that the amplitude of the current at the intermediate timing 510 is smaller than the fundamental wave current for one cycle. Also, the current phase tends to be on the leading side as opposed to the current phase at the switching timing 500.

  Note that the switching timing 500 does not strictly indicate only the time when the switching element is turned on or off, but the timing within a range in which the amplitude is relatively large with respect to the fundamental current and the phase tends to be delayed. Shall be included. Further, the intermediate timing 510 is not limited to an exact intermediate point between the switching timings 500, and includes timings in a range in which the amplitude is relatively small with respect to the fundamental current and the phase tends to be on the advanced side. .

  Hereinafter, the motor current sampled at the switching timing 500 will be referred to as “switching current”. The motor current at the intermediate timing 510 is referred to as “intermediate timing current”.

  Next, the state when the above sampled motor current is dq-axis converted will be described with reference to FIG.

  Referring to FIG. 7, DM1 to DM3 show examples of motor current distributions in a high torque region (DM1), a middle torque region (DM2), and a low torque region (DM3), respectively. This current distribution is distributed in an elliptical shape in which the major axis is in the q-axis direction in the high torque region, and the major axis is in the d-axis direction as the torque decreases.

  In the current distributions DM1 to DM3, a1 to a3 indicate distributions of sampling values of switching currents in respective torque ranges, and b1 to b3 indicate distributions of sampling values of intermediate timing currents. I1 to I3 indicate average currents in the respective torque ranges. The average currents I1 to I3 are values approximate to the fundamental current (waveform W1) of the motor current.

  Accordingly, the sampling values a1 to a3 of the switching current are currents having a larger amplitude and a phase lagging with respect to the fundamental current (W1) of the motor current. Further, the sampling values b1 to b3 of the intermediate timing current are currents whose amplitude is smaller and whose phase is on the leading side than the fundamental wave current (W1).

  In general, when switching from rectangular wave voltage control to PWM control, PWM control is performed on the side where the current phase is delayed with respect to the reference current vector that is the boundary between rectangular wave voltage control and PWM control. It becomes. On the other hand, the side on which the current phase is advanced with respect to the reference current vector is the rectangular wave voltage control.

  In terms of the magnitude of the current, in the quadrant where the d-axis current is negative and the q-axis current is positive as shown in FIG. 7, the q-axis current of a certain current is more positive than the q-axis current of the reference current vector. The side that increases in the direction, that is, the side that increases the current amplitude is PWM control. On the other hand, the side on which the q-axis current is reduced, that is, the side on which the amplitude is reduced is rectangular wave voltage control.

  Similarly, in the other quadrants of the dq axis plane, the current phase delaying side and the amplitude increasing side are PWM control with respect to the current vector serving as the boundary of the control mode, and the current phase leading side and amplitude The side on which becomes smaller is rectangular wave voltage control.

  Therefore, since the sampling values a1 to a3 of the switching current have a larger amplitude and a phase lag compared to the average currents I1 to I3, currents that facilitate switching from rectangular wave voltage control to PWM control are used. Become. Therefore, the switching from the rectangular wave voltage control to the PWM control can be performed at an early stage by using the switching current for determining whether or not the switching from the rectangular wave voltage control to the PWM control is necessary.

  On the other hand, the sampling values b1 to b3 of the intermediate timing current are smaller in amplitude and more advanced in phase than the average currents I1 to I3, so that it is difficult to switch from the rectangular wave voltage control to the PWM control. Current. Therefore, the switching of the control mode can be delayed by using the intermediate timing current for determining whether or not to switch from the rectangular wave voltage control to the PWM control.

(Problems when switching from rectangular wave voltage control to PWM control)
Next, problems of the motor control configuration when switching from rectangular wave voltage control to PWM control will be described with reference to FIG. In particular, a problem in terms of control stability when the control mode shifts from rectangular wave voltage control to overmodulation PWM control to sine wave PWM control when the output of the AC motor M1 decreases from the high output region will be described.

  Referring to FIG. 8, in the rectangular wave voltage control, the amplitude of each phase voltage is fixed to inverter input voltage VH. Therefore, on the dq axis plane, the voltage command vector indicated by the combination of the voltage command values Vd # and Vq # is located on the circumference centered on the origin. The radius of this circle corresponds to the inverter input voltage (system voltage VH). Then, phase φv of the voltage command vector is controlled in accordance with the torque deviation according to the configuration shown in FIG. The voltage command vector V1 in FIG. 8 corresponds to the final value of the AC voltage command by the rectangular wave voltage control at the time of switching from the rectangular wave voltage control to the overmodulation PWM control.

  When the control mode is switched from the rectangular wave voltage control to the overmodulation PWM control, an AC voltage command corresponding to the voltage command vector V2 is generated by the control calculation by the overmodulation PWM control unit 201. Here, voltage command vector V2 corresponds to voltage command values Vd # and Vq # after the amplitude correction processing.

  By switching from rectangular wave voltage control to overmodulation PWM control, the content of the control calculation is changed from voltage phase control to current feedback control. Since current feedback control is not performed in the rectangular wave voltage control, current deviation is likely to occur when the voltage command vector V1 changes to the voltage command vector V2 when the control mode is switched. In particular, since the rectangular wave voltage control mode is used in a high-rotation region, in order to reduce the current deviation at the time of switching the control mode, the motor current used for determining whether switching is necessary is sampled at a very short cycle. Therefore, it is necessary to determine whether or not switching is necessary. However, since there is a limit to the control cycle of the control device, a control mode switching delay occurs even if it is determined whether or not switching is necessary based on a motor current without delay. If the mode is switched to the PWM control in a state where the current deviation is large due to the delay in switching the control mode, the motor current is disturbed in the PWM control and current followability is deteriorated.

(Description of Control Mode Selection Method of Embodiment 1)
Next, control mode selection between PWM control and rectangular wave voltage control in the control mode selection unit 490 of the control block diagram shown in FIG. 4 will be described in detail with reference to FIG. Starting with FIG. 9, each step in the flowchart shown below is realized by executing a program stored in advance in the control device 30 at a predetermined cycle. Alternatively, for some steps, it is also possible to construct dedicated hardware (electronic circuit) and realize processing.

  Referring to FIG. 9, control device 30 determines in step (hereinafter abbreviated as “S”) 10 whether or not the current control mode is the PWM control mode. When the current control mode is the PWM control mode (YES in S10), control device 30, based on voltage command values Vd # and Vq # according to PWM control mode and system voltage VH, in S11. Then, a modulation rate when the input voltage VH of the inverter 14 is converted into a motor applied voltage to the AC motor M1 is calculated.

For example, the modulation rate FM is calculated by the following equation (3).
FM = (Vd # ² + Vq # ² ) ^1/2 / VH (3)
Then, in S12, the control device 30 determines whether or not the modulation factor obtained in S11 is 0.78 or more. When the modulation factor ≧ 0.78 (YES in S12), an appropriate AC voltage cannot be generated in the PWM control mode. Therefore, control device 30 advances the process to S15 and performs rectangular wave voltage control mode. The control mode is switched to select.

  On the other hand, in the case of NO in S12, that is, when the modulation factor obtained in S11 is less than 0.78, control device 30 continuously selects the PWM control mode in S14.

  On the other hand, when the current control mode is the rectangular wave voltage control mode (NO in S10), control device 30 switches the control mode generated by switching determination unit 480 of rectangular wave voltage control unit 400 in S13. The state of the flag FLG is determined.

  If mode switching flag FLG is on (YES in S13), control device 30 determines that the control mode needs to be switched from the rectangular wave voltage control mode to the PWM control mode. At this time, the control device 30 selects the PWM control mode in S14.

  On the other hand, when NO in S11, that is, when the control mode switching flag FLG is OFF, control device 30 continuously selects the rectangular wave voltage control mode in S15.

  When the PWM control mode is selected (S14), control device 30 further determines whether to apply sine wave PWM control or overmodulation PWM control in S16. This determination can be performed by comparing the modulation factor FM with a predetermined threshold (for example, 0.61 which is the theoretical maximum value of the modulation factor suitable for sinusoidal PWM control).

  When the modulation factor is less than or equal to the threshold value, sine wave PWM control is applied. On the other hand, when the modulation rate is larger than the threshold value, overmodulation PWM control is applied.

  As described above, the motor current MCRT (iv, iw) detected by the current sensor 24, the input voltage (system voltage) VH of the inverter 14 detected by the voltage sensor 13, the sine wave PWM control unit 200 or the overmodulation PWM control unit. Based on the voltage command values Vd #, Vq # generated by 201 and the control mode switching flag FLG generated by the switching determination unit 480, control mode selection can be executed.

  Next, the necessity of switching from rectangular wave voltage control to PWM control in the rectangular wave control unit 400 shown in FIG. 5 will be described in detail with reference to the flowchart of FIG.

  Referring to FIG. 10, control device 30 detects rotation angle θ from rotation angle sensor 25 installed in AC electric motor M1 in S700. Then, the control device 30 samples the inverter switching current Isw and the intermediate timing current Imid as the motor current for determining necessity of switching from the rotation angle θ (S710). Moreover, the control apparatus 30 calculates the average value of these sampled motor currents as the motor current for rectangular voltage control (S720).

  Thereafter, in S730, control device 30 performs dq axis conversion processing of switching current Isw and intermediate timing current Imid.

  Next, the control device 30 calculates a q-axis current reference value corresponding to the d-axis current value of the switching current Isw from the reference value for determining whether or not switching is stored in advance in the storage unit 470 (S740). . The reference value may be set by referring to a map based on experiments or the like, or may be calculated by a predetermined relational expression.

  Then, in S750, control device 30 determines whether or not the q-axis current value of switching current Isw is less than the current reference value calculated in S740.

  If q-axis current value of switching current Isw is equal to or greater than the current reference value (NO in S750), that is, if there is an indication of switching from rectangular wave voltage control to PWM control, control device 30 is urgent. In step S820, it is determined that switching from the rectangular wave current control mode to the PWM control mode is necessary. Then, the control device 30 outputs the control mode switching flag FLG used in the control mode selection processing step S13 shown in FIG. 9 (S820).

  Then, in S830, control device 30 performs a phase change prohibition process so as not to change voltage phase φv. Thereafter, control device 30 outputs voltage phase command φv set in the previous control cycle in S800. Then, control device 30 generates drive output commands S3 to S8 for the switching elements of inverter 14 in accordance with this voltage phase command φv, and outputs them to inverter 14 (S810).

  On the other hand, when q-axis current value of switching current Isw is less than the current reference value (YES in S750), control device 30 determines that there is no need to switch the emergency control mode, and performs steps S760 to S810. A normal rectangular wave voltage control process is performed.

  Specifically, first, in step S760, the control device 30 performs a filtering process for smoothing the control average current in the time axis direction in order to remove the distortion component of the control average current calculated in step S720. . Then, control device 30 determines whether or not the absolute value of current phase φi of the average current after filtering is smaller than the absolute value of predetermined switching current phase φ0 (S770). Note that switching phase current φ0 may be set to a different value during powering and regeneration of AC electric motor M1.

  When the absolute value of the current phase φi of the average current is equal to or larger than the absolute value of the switching phase reference value φ0 (that is, on the leading side with respect to the reference current vector) (NO in S770), the control device 30 is rectangular. Maintaining the wave voltage control mode, in S780, the estimated torque value is calculated from the current of each phase of the average current, the voltage of each phase, and the angular velocity ω calculated from the rotation angle θ detected by the rotation angle sensor 25. Tq is calculated. Then, control device 30 performs a torque feedback calculation from calculated torque estimated value Tq and torque command value Trqcom to calculate voltage phase command φv (S790). Thereafter, in S800, control device 30 outputs voltage phase command φv calculated in S790, and generates and outputs drive output commands S3 to S8 to inverter 14 based on voltage phase command φv (S810). .

  On the other hand, control device 30 determines that the absolute value of current phase φi of the average current is smaller than the absolute value of switching phase reference value φ0 (that is, on the delay side with respect to the reference current vector) (YES in S770). The control device 30 determines that switching from the rectangular wave voltage control mode to the PWM control mode is necessary, and then the process proceeds to S820.

  Then, similarly to the emergency control mode switching described above, the control device 30 turns on and outputs the control mode switching flag FLG (S820), and prohibits the change of the voltage phase command φv (S830). Thereafter, the control device 30 generates and outputs drive output commands S3 to S8 to the inverter 14 through the processes of S800 to S810 as described above.

  By performing such processing, switching of the control mode from rectangular wave voltage control to PWM control using a switching current that is a current whose current amplitude is larger than the fundamental wave current of the motor current and whose current phase is delayed. Necessity determination can be performed. As a result, even when the driving state of AC electric motor M1 is suddenly changed, it is possible to suppress an increase in current deviation at the time of switching the control mode by switching the control mode at an early stage. As a result, it is possible to stabilize the control when switching the control mode from rectangular wave voltage control to PWM control.

[Modification of Embodiment 1]
In the first embodiment, the switching current is used to determine whether or not the urgent switching from the rectangular wave voltage control mode to the PWM control mode is necessary. In the modification of the first embodiment, a method of switching the current used for the necessity determination of switching according to the magnitude of the torque command value Trqcom will be described.

  As described in the explanation of the sampling current in FIG. 7, in the low torque range, the motor current approaches an elliptical distribution in which the major axis is in the d-axis direction. Therefore, the deviation between the q-axis current value of the switching current and the q-axis current value of the average current is small, and when it is determined to facilitate switching from the rectangular wave voltage control to the PWM control by using the switching current, There is a possibility that so-called chattering occurs, in which the control mode is frequently changed.

  Therefore, in the modified example, in order to suppress the occurrence of chattering, in the high torque region where the torque command value Trqcom is equal to or higher than the predetermined first torque reference value, the switching current is changed to the same as in the first embodiment. Based on the description of FIG. 7, the motor current used for the switching necessity determination is determined in the low torque range where the torque command value Trqcom is less than the predetermined second torque reference value. As described above, the occurrence of chattering is suppressed by determining whether or not switching is necessary based on an intermediate timing current that is a direction of delaying switching of the control mode. In the low torque region, since the motor current is originally small, the occurrence of overcurrent due to current disturbance is small. Note that the switching current or the intermediate timing current used in the determination of whether or not switching is necessary will be collectively referred to as “determination current” below.

  Note that the first torque reference value and the second torque reference value may be the same value, and in the following modification, the first torque reference value and the second torque reference value are the same value. Will be described. Further, when the first torque reference value and the second torque reference value are different, in the middle torque range (that is, when the torque command value Trqcom is greater than or equal to the second torque reference value and less than the first torque reference value). For example, the necessity of switching may be determined using an average current of the switching current and the intermediate timing current.

  With reference to the flowchart of FIG. 11, the necessity determination of switching from rectangular wave voltage control to PWM control in the control mode selection unit 490 of the control block diagram shown in FIG. 4 according to the modification of the first embodiment will be described.

  Referring to FIG. 11, in FIG. 11, steps S731, S732, and S733 are added to the processing in FIG. The description of the same steps as in FIG. 10 will not be repeated.

  The controller 30 performs dq axis conversion of the sampled switching current and intermediate timing current in S730, and then determines whether or not the torque command value Trqcom is smaller than a predetermined torque reference value in S731. .

  If torque command value Trqcom is smaller than the predetermined torque reference value (YES in S731), in S732, control device 30 sets an intermediate timing current as the determination current, and the process proceeds to S740. .

  On the other hand, when torque command value Trqcom is equal to or greater than a predetermined torque reference value (NO in S731), control device 30 sets a switching current as a determination current, and the process proceeds to S740.

  Thereafter, similarly to the description of the processing in FIG. 10, the control device 30 sets a q-axis current reference value corresponding to the d-axis current value of the determination current in S740. In S750, the control mode switching necessity determination is performed by comparing the q-axis current reference value with the q-axis current value of the control mode determination current. The subsequent processing is the same as in the first embodiment.

  By adopting such a configuration, it is possible to quickly switch from rectangular wave voltage control to PWM control in the high torque range while suppressing chattering occurrence at the time of control mode switching in the low torque range. Control stabilization at the time of switching the control mode from rectangular wave voltage control to PWM control can be achieved.

[Embodiment 2]
In the first embodiment and the modification thereof, the q-axis current value of the determination current is used, and the necessity of switching the control mode is determined by comparing the q-axis current value with the reference value. In the second embodiment, instead of this, a method for determining the switching of the control mode using the phase of the current for determination will be described.

  In the first embodiment and the modification thereof, the q-axis current reference value of the control mode determination current is set corresponding to the d-axis current value of the sampled determination current. It can also be expressed as a phase. That is, based on the d-axis current value of the determination current, control device 30 calculates current phase reference φ0 # corresponding to the q-axis current reference value of the determination current. Further, the control device 30 calculates the phase φi # of the determination current from the d-axis and q-axis current values of the determination current.

  Then, whether or not the control mode needs to be switched from the rectangular wave voltage control to the PWM control is determined based on whether or not the absolute value of the phase φi # of the determination current is smaller than the absolute value of the current phase reference φ0 #. Thereby, control device 30 can perform the same determination as in the first embodiment and its modification.

  In the process of step S770 in the flowcharts shown in FIGS. 10 and 11, the average value current subjected to the filter process is used, but here, the raw value of the sampling current that is not subjected to the filter process is used. .

  Next, a method of determining whether or not switching from rectangular wave voltage control to PWM control according to Embodiment 2 in control mode selection unit 490 of the control block diagram shown in FIG. 4 will be described using the flowchart of FIG. To do.

  Referring to FIG. 12, in FIG. 12, steps S740 and S750 in the processing of the first embodiment in FIG. 10 are replaced with S741 and S751, respectively. The description of the same steps as in FIG. 10 will not be repeated.

  The control device 30 calculates the phase reference value φ0 # corresponding to the d-axis current value of the determination current (here, the switching current Isw) that has been dq-axis converted in S730 (S741).

  Thereafter, in S751, control device 30 compares the absolute value of current phase reference value φ0 # calculated in S741 with the absolute value of phase φi # of the current for determination, thereby determining phase φi # of the current for determination. Is smaller than the absolute value of the current phase reference value φ0 #.

  When the absolute value of phase φi # of determination current is equal to or larger than the absolute value of current phase reference value φ0 # (that is, the leading side) (NO in S751), control device 30 operates in rectangular wave voltage control mode. Is continuously selected, and the process proceeds to S760.

  On the other hand, when the absolute value of phase φi # of the determination current is smaller than the absolute value of current phase reference value φ0 # (that is, on the delay side) (YES in S751), control device 30 causes rectangular wave voltage It is determined that switching from the control mode to the PWM control mode is necessary, and the process proceeds to S820. The subsequent processing is the same as in the first embodiment.

  By adopting such a configuration, the switching from the rectangular wave voltage control to the PWM control can be performed at an early stage according to the phase of the determination current, as in the first embodiment. As a result, the control can be stabilized when the control mode is switched from the rectangular wave voltage control to the PWM control.

  Further, in the modified example of the first embodiment, similarly to the above, the process of S740 and S750 in the flowchart of FIG. 11 is replaced with S741 and S751, respectively, so that the torque command value Trqcom is increased. The control mode switching necessity determination can be performed using the phase of the determination current set accordingly. Note that the detailed description of each step will not be repeated.

  As a result, similar to the modification of the first embodiment, the chattering at the time of control mode switching is suppressed in the low torque range, and the switching from the rectangular wave voltage control to the PWM control can be performed early in the high torque range. Therefore, it is possible to stabilize the control when the control mode is switched from the rectangular wave voltage control to the PWM control.

  In the present embodiment, as a preferred configuration example, a configuration is shown in which DC voltage generation unit 10 # of the motor drive system includes converter 12 so that the input voltage (system voltage VH) to inverter 14 can be variably controlled. However, as long as the input voltage to inverter 14 can be variably controlled, DC voltage generation unit 10 # is not limited to the configuration exemplified in the present embodiment. Further, it is not essential that the inverter input voltage is variable, and the present invention is also applied to a configuration in which the output voltage of the DC power supply B is directly input to the inverter 14 (for example, a configuration in which the converter 12 is omitted). Is possible.

  Further, with regard to the AC motor serving as a load of the motor drive system, in the present embodiment, a permanent magnet motor mounted for driving a vehicle in an electric vehicle (hybrid vehicle, electric vehicle, etc.) is assumed. The present invention can also be applied to a configuration in which an arbitrary AC motor used in is used as a load.

  The switching current Isw corresponds to the “first current” of the present invention, and the intermediate timing current Imid corresponds to the “second current” of the present invention. The current sensor 24 corresponds to the “current detector” in the present invention.

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

1 is an overall configuration diagram of a motor drive control system to which an AC motor control device according to an embodiment of the present invention is applied. It is a figure which illustrates schematically the control mode of AC electric motor M1 in the motor drive system by embodiment of this invention. It is a figure which shows the correspondence of the operation state of AC electric motor M1, and each control mode. It is a functional block diagram which shows the control structure of the control apparatus of the alternating current motor of this Embodiment. It is a block diagram explaining the motor control structure by the rectangular wave voltage control of this Embodiment. It is a figure for demonstrating the sampling current in the current extraction part of this Embodiment. It is a figure for demonstrating the example of distribution in the dq-axis plane of the sampling current in the current extraction part of this Embodiment. It is a figure explaining the example of the change of alternating voltage command at the time of switching from rectangular wave voltage control to PWM control. It is a flowchart explaining the control mode selection process between PWM control and rectangular wave voltage control by this Embodiment. 4 is a flowchart for explaining a necessity determination process for switching from rectangular wave voltage control to PWM control according to the first embodiment. It is a flowchart explaining the necessity determination process for switching from rectangular wave voltage control to PWM control according to a modification of the first embodiment. It is a flowchart explaining the necessity determination process for switching from rectangular wave voltage control to PWM control according to the second embodiment.

Explanation of symbols

  5 Ground wire, 6, 7 Power line, 10 # DC voltage generator, 10, 13 Voltage sensor, 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 control system, 200 sine wave PWM control unit, 201 overmodulation PWM control unit, 280 PWM control unit, 400 rectangular wave voltage control unit, 410 power calculation unit, 420 torque Calculation unit, 430 calculation unit, 440 rectangular wave generator, 450 signal generation unit, 460 current extraction unit, 470 storage unit, 480 switching determination unit, 490 control mode selection unit, 500 switching timing, 510 intermediate timing, B DC power supply, C0, C1 smoothing capacitors, D1 to D8 antiparallel diodes, LG control mode switching flag, FM modulation factor, Ib DC current, CSTP phase change prohibition signal, Isw, Imid motor sampling current, L1 reactor, M1 AC motor, MCRT (iu, iv, iw) motor current, Pmt motor power, Q1-Q8 Power semiconductor switching element, RGE regenerative braking mode signal, S1-S8 switching control signal, SE system relay drive signal, SR1, SR2 system relay, Tq torque estimated value, Trqcom torque command value, V1, V2 voltage command vector , Vb DC voltage, Vd #, Vq # Voltage command value (d, q axis), VH inverter input voltage, Vu, Vv, Vw Motor phase voltage command value, ΔTq Torque deviation, θ rotation angle, φ0 switching phase reference value , Φ0 # current phase reference value, φi, φi # Flow phase, φv voltage phase, ω angular velocity.

Claims (10)

An AC motor control device in which an applied voltage is controlled by an inverter,
A current detector for detecting a motor current flowing between the inverter and the AC motor;
A rectangular wave voltage control unit that generates a control command for the inverter so that a rectangular wave voltage phase-controlled to operate the AC motor according to a torque command is applied to the AC motor;
A pulse width modulation control unit for generating a control command for the inverter by a pulse width modulation control based on a comparison between a carrier wave and an AC voltage command for operating the AC motor according to a torque command;
A control mode selection unit configured to select one of rectangular wave voltage control by the rectangular wave voltage control unit and the pulse width modulation control by the pulse width modulation control unit according to the operating state of the AC motor. And
The rectangular wave voltage control unit
The motor current detected by the current detector at a first predetermined timing when the amplitude and phase of the motor current are larger than the fundamental wave current, which is a fundamental wave component, and the phase is delayed. A current extractor configured to sample;
A switching determination unit configured to determine whether to switch from the rectangular wave voltage control to the pulse width modulation control based on the first current sampled at the first predetermined timing. AC motor control device.   The control of the AC motor according to claim 1, wherein the switching determination unit determines whether the switching is necessary based on the first current when the torque command value is equal to or greater than a predetermined first torque reference value. apparatus. The current extraction unit is configured to further sample the motor current at a second predetermined timing in which the amplitude and phase of the motor current are smaller than the fundamental current and the phase is advanced. And
The switching determination unit performs sampling at the second predetermined timing instead of determining whether the switching is necessary based on the first current when the torque command value is less than a predetermined second torque reference value. The control apparatus for an AC motor according to claim 1, wherein the necessity of switching is determined based on the second current that has been performed.   The control device for an AC motor according to any one of claims 1 to 3, wherein the switching determination unit determines whether or not the switching is necessary based on a magnitude of the first current.   The control device for an AC motor according to claim 1, wherein the switching determination unit determines whether or not the switching is necessary based on a phase of the first current. The inverter is
Including a plurality of switching elements that perform power conversion in accordance with the control command;
6. The AC motor according to claim 1, wherein the first current is the motor current sampled at a timing corresponding to a drive switching timing of each of the plurality of switching elements of the inverter. Control device.   The switching determination unit determines whether the switching is necessary based on the magnitude of the first current when the torque command value is greater than or equal to the first torque reference value, and the torque command value is the second torque command value. The control device for an AC motor according to claim 3, wherein when the torque is less than a torque reference value, the necessity of the switching is determined based on the magnitude of the second current.   When the torque command value is equal to or greater than the first torque reference value, the switching determination unit determines whether the switching is necessary based on the phase of the first current, and the torque command value is the second torque. 4. The control apparatus for an AC motor according to claim 3, wherein when it is less than a reference value, the necessity of switching is determined based on a phase of the second current. The inverter is
Including a plurality of switching elements that perform power conversion in accordance with the control command;
The first current is the motor current at a timing corresponding to a drive switching timing of each of the plurality of switching elements to the inverter, and the second current is between sampling timings of the first current. The control apparatus for an AC motor according to claim 3, 7 or 8, wherein the motor current is sampled at an intermediate timing. The AC motor configured to generate a vehicle driving force;
The electric vehicle carrying the said control apparatus of the said AC motor of any one of Claims 1-9.

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