JP2009171640A - Electric motor drive control device, drive control method, and electric vehicle - Google Patents

Abstract

An electric motor having a plurality of control modes is switched between control modes so as to suppress an increase in temperature of a permanent magnet while maintaining its operation.
A magnet temperature estimation unit 420 estimates a temperature of a permanent magnet mounted on a rotor of AC motors M1 and M2. Mode switching determination unit 400 determines each control mode switching of AC motors M1 and M2 between the rectangular wave voltage control mode and the PWM control mode using the determination value set by determination value setting unit 410. With respect to the determination value used in the mode switching determination unit 400, the determination value setting unit 410 has a relatively higher motor operation region to which the rectangular wave control mode is applied when the magnet temperature is increased than when the magnet temperature is not increased. Change to be widely set.
[Selection] Figure 11

Description

  The present invention relates to a motor drive control device, a drive control method, and an electric vehicle, and more particularly to a technique for preventing demagnetization of a permanent magnet in an electric motor having a permanent magnet in a rotor.

  In recent years, electric vehicles such as hybrid vehicles and electric vehicles have attracted a great deal of attention as environmentally friendly vehicles. Such an electric vehicle includes a power storage device including a secondary battery and an electric motor (motor generator) for receiving electric power from the power storage device and generating a driving force. The electric motor generates driving force when starting or accelerating, and generates electric power that converts kinetic energy of the vehicle into electric energy during braking or the like. This generated power is collected by the power storage device.

  In many cases, a permanent magnet synchronous machine is used as an electric motor mounted on such an electric vehicle because of high density of field magnetic flux and ease of power regeneration. In particular, an interior permanent magnet synchronous machine having an embedded structure that can be used in combination with a driving torque (reluctance torque) generated by the asymmetry of the magnetic resistance is frequently employed.

  In general, it is known that a permanent magnet changes its holding power in accordance with the environmental temperature. For example, if a ferromagnetic material that is the main component of a permanent magnet is exposed to a high environmental temperature that exceeds the Curie point that causes a phase transition, the holding power of the permanent magnet will decrease, causing irreversible demagnetization that cannot be restored. obtain.

  In addition, when an AC motor such as a permanent magnet synchronous machine is driven and controlled by an inverter, the motor current is generally controlled according to pulse width modulation (PWM) based on vector control in order to drive the motor with high efficiency. The Furthermore, in order to improve the motor output, the configuration is such that the AC motor is controlled by switching between the rectangular wave voltage phase control mode in which the rectangular wave voltage is applied to the AC motor for driving control and the PWM current control mode in accordance with the PWM control. It is known.

  For example, Japanese Patent Laid-Open No. 2006-311770 (Patent Document 1) discloses a magnet drive motor system that switches between a rectangular wave control mode based on torque feedback control and a PWM control mode based on motor current feedback control according to motor operating conditions. It is described that a control command value for motor current control is generated by reflecting a torque deviation so as to compensate for a change in motor output characteristics depending on temperature.

  Japanese Patent Laid-Open No. 2003-244990 (Patent Document 2) discloses a motor control device for smoothly switching between sine wave PWM control and rectangular wave control. It is described that a wave AC voltage is generated and applied to a motor.

Furthermore, in Japanese Patent Application Laid-Open No. 2007-166830 (Patent Document 3), a rectangular wave current energizing section and a current peak command value are determined based on a difference between a motor internal temperature and a predetermined motor allowable temperature. Japanese Patent Laid-Open No. 2006-223037 (Patent Document 4) prevents the demagnetization of the permanent magnet by blocking the gate signal when the temperature of the permanent magnet exceeds the allowable temperature. It is described. Japanese Patent Laid-Open No. 2004-166415 (Patent Document 5) describes a PWM control and an inverter loss in consideration of the motor loss and the inverter loss so that the temperature of the motor and the motor driving device (inverter) does not exceed the allowable value. It is described that the switching of the rectangular wave control is controlled.
JP 2006-31770 A JP 2003-244990 A JP 2007-166830 A JP 2006-223037 A JP 2004-166415 A

  If the temperature of the permanent magnet exceeds the permissible temperature as in Patent Document 4, if the gate signal is cut off, that is, if the motor operation is controlled to stop, the permanent magnet is excessive so that demagnetization occurs. The high temperature state can be prevented more reliably. However, in the permanent magnet type motor mounted on the above-mentioned electric vehicle for generating vehicle driving force, it is preferable to avoid the excessively high temperature while making the motor operable as much as possible.

  The present invention has been made to solve such problems, and an object of the present invention is to suppress an increase in temperature of a permanent magnet while maintaining the operation of an electric motor having a plurality of control modes. Thus, the control mode is switched.

  An electric motor drive control device according to the present invention is an electric motor drive control device having a permanent magnet in a rotor, and includes a magnet temperature estimation unit, a determination value setting unit, and a mode switching determination unit. The magnet temperature estimation unit estimates the temperature of the permanent magnet. The determination value setting unit sets a determination value used for switching the control mode of the electric motor according to the magnet temperature estimated by the magnet temperature estimation unit. The mode switching determination unit uses the determination value set by the determination value setting unit to apply a rectangular wave voltage to the stator winding of the motor, and to the stator winding according to the pulse width modulation control. The control mode switching between the second control mode for controlling the applied voltage is determined. The determination value setting unit sets the determination value used in the mode switching determination unit to the first determination value when the magnet temperature is not increased, while the first determination value is used when the magnet temperature is increased. In comparison, the second determination value is set such that the operating range of the electric motor to which the first control mode is applied is set relatively wide.

  An electric motor drive control method according to the present invention is an electric motor drive control method having a permanent magnet in a rotor, the step of determining the temperature state of the permanent magnet based on the temperature estimation of the permanent magnet, and the control mode switching of the electric motor. A step of setting a determination value used in accordance with the temperature state of the permanent magnet, a first control mode in which a rectangular wave voltage is applied to the stator winding of the motor using the set determination value, and a pulse width Determining a control mode switch between a second control mode for controlling a voltage applied to the stator winding according to the modulation control. In the setting step, the determination value is set to the first determination value when the temperature of the previous permanent magnet is not increased, and compared with the time when the first determination value is used when the temperature of the permanent magnet is increased. The second determination value is set such that the operating range of the electric motor to which the first control mode is applied is set relatively wide.

  According to the motor drive control apparatus and control method, the determination value used for switching between the first control mode (rectangular wave control) and the second control mode (PWM control) is used as the estimated temperature (magnet temperature) of the permanent magnet. By changing accordingly, when the magnet temperature rises, the operating range of the electric motor to which the first control mode is applied is expanded. When applying rectangular wave control, magnetic field fluctuations due to high-frequency components of motor current are smaller than when applying PWM control where switching control is performed at a high frequency, so the magnet temperature rise due to eddy current is relatively suppressed. Is done. For this reason, the control mode switching of the motor can be executed so as to suppress the temperature rise of the permanent magnet while maintaining the operation of the motor.

  Preferably, the drive control device further includes a load limiting unit. The determination value setting unit gradually changes the second determination value in a direction in which the operating range of the electric motor to which the first control mode is applied is set relatively wide when the magnet temperature is increased. The load limiting unit instructs load limiting of the electric motor when the second determination value is changed to a predetermined limit value by the determination value setting unit when the magnet temperature rises. Alternatively, in the setting step, when the temperature of the permanent magnet rises, the second determination value is gradually changed in a direction in which the operation range of the electric motor to which the first control mode is applied is set relatively wide. The drive control method further includes a step of instructing a load limit of the electric motor when the second determination value is changed to a predetermined limit value by the determination value setting unit when the temperature of the permanent magnet rises. .

  If it does in this way, when it is difficult to raise magnet temperature by adjustment of control mode switching by change of judgment value, it can prevent more reliably that magnet temperature rises further by load restriction of an electric motor. In other words, the output of the electric motor can be ensured as compared with a control configuration that directly executes load limitation in response to a magnet temperature increase.

  Preferably, the determination value setting unit is configured to set the first determination value when the magnet temperature becomes a predetermined temperature or lower when the second determination value is set. Alternatively, the setting step sets the first determination value when the permanent magnet becomes a predetermined temperature or lower when the second determination value is set.

  In this way, when the magnet temperature once increased decreases due to the adjustment of the control mode switching, the drive efficiency of the electric motor can be improved by returning the application area of the second control mode to normal.

  Or preferably, a magnet temperature estimation part calculates a magnet temperature using at least one of the temperature of the refrigerant | coolant used for the circulation cooling system of an electric motor, and the stator temperature of an electric motor. Alternatively, the estimated temperature value of the permanent magnet used in the determining step is calculated using at least one of the temperature of the refrigerant and the temperature of the stator used in the circulating cooling system of the electric motor.

  In this way, the temperature of the permanent magnet, which is attached to the rotor of the electric motor and cannot be directly measured by the sensor, can be estimated easily and with high accuracy.

  An electric vehicle according to the present invention includes an electric motor having a rotor connected to wheels so as to be able to transmit a driving force, and any one of the drive control devices for controlling the electric motor.

  In the electric vehicle, the control mode of the electric motor can be switched so as to suppress an increase in the temperature of the permanent magnet while maintaining a state where the vehicle driving force can be generated by the operation of the electric motor.

  According to the present invention, for an electric motor having a plurality of control modes, by changing the control mode switching condition according to the permanent magnet temperature, the control is performed so as to suppress the temperature increase of the permanent magnet while maintaining its operation. Mode switching can be performed.

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

[overall structure]
FIG. 1 is a schematic block diagram showing an example of a hybrid vehicle equipped with a drive control apparatus for an electric motor according to an embodiment of the present invention.

  Referring to FIG. 1, a hybrid vehicle 200 shown as a representative example of an electric vehicle includes a hybrid vehicle drive device 100, a power split mechanism 210, a differential gear (DG) 220, and drive wheels 230. Hybrid vehicle drive apparatus 100 includes DC power supply B, system relays SR 1 and SR 2, converter 12, inverters 14 and 31, DC / DC converter 20, auxiliary battery 21, control apparatus 30, engine 60, and so on. And AC motors M1 and M2. The inverters 14 and 31 constitute an IPM (intelligent power module) 35. AC motors M <b> 1 and M <b> 2 both constitute “motors” to be controlled by the drive control device for the motor according to the embodiment of the present invention.

  AC motor M <b> 1 is coupled to engine 60 through power split mechanism 210. AC motor M <b> 1 starts engine 60 or generates electric power by the rotational force of engine 60. AC motor M <b> 2 drives drive wheel 230 via power split mechanism 210.

  As an example, AC motors M1 and M2 are constituted by permanent magnet type three-phase AC synchronous motors. That is, each of AC motors M1 and M2 is configured to rotate a rotor having a permanent magnet by a current magnetic field (rotating magnetic field) generated by a drive current flowing in a coil provided in the stator. In addition, as described above, the “motor” in the present application is described as confirming that it is a concept including what has a function of a so-called motor generator.

  The DC power source B is composed of a secondary battery such as nickel metal hydride or lithium ion. System relays SR1 and SR2 are turned on / off by signal SE from control device 30. More specifically, system relays SR1 and SR2 are turned on by H (logic high) level signal SE from control device 30, and are turned off by L (logic low) level signal SE from control device 30.

  Converter 12 boosts the DC voltage supplied from DC power supply B and supplies it to inverters 14 and 31. More specifically, when converter 12 receives signal PWMU from control device 30, converter 12 boosts the DC voltage and supplies it to inverters 14 and 31. When converter 12 receives signal PWMD from control device 30, converter 12 steps down the DC voltage supplied from inverter 14 (or 31) and supplies it to DC power supply B and DC / DC converter 20. Further, converter 12 stops the step-up operation and the step-down operation by signal STP1 from control device 30.

  When a DC voltage is supplied from converter 12, inverter 14 converts the DC voltage into an AC voltage based on control signal DRV1 from control device 30, and drives AC motor M1. Further, the inverter 14 converts the AC voltage generated by the AC motor M1 into a DC voltage based on the control signal DRV1 from the control device 30 during regenerative braking of the hybrid vehicle on which the hybrid vehicle drive device 100 is mounted. The supplied DC voltage is supplied to the converter 12.

  When the DC voltage is supplied from the converter 12, the inverter 31 converts the DC voltage into an AC voltage based on the control signal DRV2 from the control device 30, and drives the AC motor M2. The inverter 31 converts the AC voltage generated by the AC motor M2 into a DC voltage based on the control signal DRV2 from the control device 30 during regenerative braking of the hybrid vehicle on which the hybrid vehicle drive device 100 is mounted. The supplied DC voltage is supplied to the converter 12.

  Note that regenerative braking here refers to braking with regenerative power generation when a driver operating an electric vehicle such as a hybrid vehicle or the like does not operate regenerative power generation or does not operate the foot brake. It includes decelerating (or stopping acceleration) the vehicle while regenerating power by turning it off.

  The DC / DC converter 20 is driven by a control signal DRV from the control device 30, converts the DC voltage from the DC power supply B, and charges the auxiliary battery 21. The DC / DC converter 20 is stopped by a signal STP2 from the control device 30. The auxiliary battery 21 stores the electric power supplied from the DC / DC converter 20.

  Control device 30 includes control signal DRV1 for controlling inverter 14, control signal DRV2 for controlling inverter 31, signals PWMU and PWMD for controlling converter 12, stop signal STP1 for converter 12, and DC / A stop signal STP2 for the DC converter 20 is generated.

FIG. 2 is a schematic diagram of the power split mechanism 210 shown in FIG.
Referring to FIG. 2, power split mechanism 210 includes a ring gear 211, a carrier gear 212, and a sun gear 213. The shaft 251 of the engine 60 is connected to the carrier gear 212 via the planetary carrier 253, the shaft 252 of the AC motor M <b> 1 is connected to the sun gear 213, and the shaft 254 of the AC motor M <b> 2 is connected to the ring gear 211. The shaft 254 of the AC motor M2 is coupled to the drive shaft of the drive wheel 230 via the DG 220.

  AC motor M <b> 1 rotates shaft 251 via shaft 252, sun gear 213, carrier gear 212, and planetary carrier 253 to start engine 60. AC motor M1 receives the rotational force of engine 60 through shaft 251, planetary carrier 253, carrier gear 212, sun gear 213, and shaft 252, and generates electric power by the received rotational force.

  FIG. 3 is a diagram showing in detail a portion related to drive control of AC motors M1, M2 in hybrid vehicle drive apparatus 100 of FIG.

  Referring to FIG. 3, DC power supply B outputs a DC voltage. Voltage sensor 10 detects voltage Vb output from DC power supply B and outputs the detected voltage Vb to control device 30.

  When system relays SR1 and SR2 are turned on by signal SE from control device 30, DC voltage from DC power supply B is supplied to capacitor C1. Capacitor C1 smoothes the DC voltage supplied from DC power supply B through system relays SR1 and SR2, and supplies the smoothed DC voltage to converter 12. The voltage sensor 11 detects the voltage Vc across the capacitor C 1 and outputs the detected voltage Vc to the control device 30.

  Converter 12 includes a reactor L1 and power semiconductor switching elements (switching elements) Q1, Q2. In the present embodiment, an IGBT (Insulated Gate Bipolar Transistor) is typically used as the switching element, but any power semiconductor element that can be on / off controlled by a control signal is applicable. Further, anti-parallel diodes D1 and D2 that flow current from the emitter side to the collector side are connected to the switching elements Q1 and Q2, respectively.

  The converter 12 boosts the DC voltage from the DC power source B and outputs it to the capacitor C2, and also converts the voltage of the capacitor C2 and supplies it to the DC power source B during regenerative braking of the hybrid vehicle. It is configured as a bidirectional buck-boost converter capable of both.

  Capacitor C2 smoothes the DC voltage supplied from converter 12, and supplies the smoothed DC voltage to inverters 14 and 31. Voltage sensor 13 detects the voltage on both sides of capacitor C2, that is, output voltage VH of converter 12.

  When the DC voltage is supplied from the capacitor C2, the inverter 14 converts the DC voltage into an AC voltage based on the control signal DRV1 from the control device 30, and drives the AC motor M1. As a result, AC motor M1 is driven so as to generate torque specified by torque command value TR1. Further, the inverter 14 converts the AC voltage generated by the AC motor M1 into a DC voltage based on the control signal DRV1 from the control device 30 during regenerative braking of the hybrid vehicle on which the hybrid vehicle drive device 100 is mounted. The supplied DC voltage is supplied to the converter 12 via the capacitor C2.

  When the DC voltage is supplied from the capacitor C2, the inverter 31 converts the DC voltage into an AC voltage based on the control signal DRV2 from the control device 30, and drives the AC motor M2. As a result, AC motor M2 is driven so as to generate torque specified by torque command value TR2. The inverter 31 converts the AC voltage generated by the AC motor M2 into a DC voltage based on the control signal DRV2 from the control device 30 during regenerative braking of the hybrid vehicle on which the hybrid vehicle drive device 100 is mounted. The supplied DC voltage is supplied to the converter 12 via the capacitor C2.

  Rotation angle detectors 32A and 32B are arranged in AC motors M1 and M2, respectively. The rotation angle detectors 32A and 32B are connected to the rotation shafts of the AC motors M1 and M2, and detect and detect the rotation angles θ1 and θ2 based on the rotation positions of the rotors (rotors) of the AC motors M1 and M2. The rotation angles θ1 and θ2 are output to the control device 30.

  Control device 30 receives torque command values TR1 and TR2 and motor rotational speeds MRN1 and MRN2 from an externally provided electronic control unit (ECU). Control device 30 further receives voltage Vb from voltage sensor 10, voltage Vc from voltage sensor 11, and voltage VH from voltage sensor 13 in addition to rotation angles θ 1 and θ 2 from rotation angle detectors 32 A and 32 B. The motor current MCRT1 is received from the current sensor 24, and the motor current MCRT2 is received from the current sensor 28.

  Control device 30 performs control for switching control of switching elements included in inverter 14 when inverter 14 drives AC motor M1 based on voltage VH, motor current MCRT1, torque command value TR1, and rotation angle θ1. Signal DRV1 is generated and output to inverter 14. Similarly, control device 30 performs switching control of switching elements included in inverter 31 when inverter 31 drives AC motor M2 based on voltage VH, motor current MCRT2, torque command value TR2, and rotation angle θ2. Control signal DRV2 is generated and output to inverter 31.

  When inverter 14 (or 31) drives AC motor M1 (or M2), control device 30 is based on voltages Vb and VH, torque command value TR1 (or TR2) and motor rotational speed MRN1 (or MRN2). A control signal PWMU for switching control of switching elements Q1 and Q2 of converter 12 is generated and output to converter 12.

  Control device 30 generates control signals DRV 1 and 2 so as to convert the AC voltage generated by AC motor M 1 or M 2 into a DC voltage during regenerative braking of hybrid vehicle 200. Control device 30 outputs control signals DRV1, DRV2 to inverters 14, 31. Thereby, the inverter 14 converts the AC voltage generated by the AC motor M1 into a DC voltage and supplies it to the converter 12, and the inverter 31 converts the AC voltage generated by the AC motor M2 into a DC voltage and converts it into a converter. 12 to operate.

  Further, control device 30 generates control signal PWMD so as to step down the DC voltage supplied from inverter 14 (or 31), and outputs it to converter 12. As a result, the AC voltage generated by AC motor M1 or M2 is converted into a DC voltage, stepped down, and supplied to DC power supply B.

  FIG. 4 is a schematic diagram illustrating the configuration of the inverters 14 and 31. As shown in FIG. 4, each of inverters 14 and 31 constitutes U-phase arm 15, V-phase arm 16 and W-phase arm 17 provided in parallel between power supply line 1 and earth line 2. And switching elements Q5 to Q8. Anti-parallel diodes D3 to D8 are connected to the switching elements Q3 to Q8, respectively. As shown in the figure, the intermediate point of each phase arm is connected to each phase end of the stator coil of the corresponding AC motor M1 or M2.

  FIG. 5 is a diagram illustrating a configuration example of a main part of a permanent magnet type rotating electrical machine used for AC motors M1 and M2.

  Referring to FIG. 5, in the rotor of the permanent magnet type synchronous machine, a plurality of holes 52 are formed in rotor core 50, and permanent magnets 54 are inserted and disposed in holes 52 to form poles. In the stator 40, a plurality of coils (not shown) are arranged so as to surround the rotor core 50. The rotor is rotationally driven based on a rotating magnetic field formed by energizing a plurality of coils.

  Here, since the magnetic flux generated by the coil of the stator 40 penetrates the permanent magnet 54, an eddy current is generated in the permanent magnet 54. The problem of heat generation and loss of the eddy current generated in the magnet becomes conspicuous as the electric motor is reduced in size, speeded up and increased in output. That is, the heat generation leads to demagnetization of the magnet and causes a failure of the motor.

  FIG. 6 is a diagram schematically showing a cross section of AC motors M1 and M2. In FIG. 6, the cross-sectional directions of AC motors M1 and M2 are parallel to the rotation axes of AC motors M1 and M2.

  Referring to FIG. 6, AC motors M <b> 1 and M <b> 2 are housed in case 65. AC motor M1 includes a rotor core 50.1 and a permanent magnet 54.1. The permanent magnet 54.1 is inserted into the rotor core 50.1. AC motor M1 further includes a stator core 40.1 and a stator coil 46.1 wound around stator core 40.1. Stator core 40.1 (and stator coil (46.1) are provided around rotor core 50.1.

  AC motor M2 includes a rotor core 50.2 and a permanent magnet 54.2. Permanent magnet 54.2 is inserted into rotor core 50.2. AC motor M2 further includes a stator core 40.2 and a stator coil 46.2 wound around stator core 40.2. Stator core 40.2 (and stator coil 46.2) is provided around rotor core 50.2.

  The number of permanent magnets 54.1 and the number of permanent magnets 54.2 are not particularly limited.

  An axis X is a rotating shaft of the AC motor M1 and a rotating shaft of the AC motor M2. As shown in FIG. 6, the length of the rotor core 50.1 in the axis X direction is longer than the length of the rotor core 50.2 in the axis X direction. Thus, AC motor M1 and AC motor M2 have different structures.

  The oil 70 accumulated at the bottom of the case 65 is scraped by the rotation of the rotor cores 50.1 and 50.2. Rotor core 50.1 and stator (stator core 40.1 and stator coil 46.1) are cooled by oil 70. Similarly, rotor core 50.2 and stator (stator core 40.2 and stator coil 46.2) are cooled by oil 70. In this way, a “circulation cooling system” of AC motors M1, M2 using oil 70 as a cooling medium is configured.

  The oil 70 is specifically an automatic transmission fluid (ATF) of an automatic transmission. According to the present embodiment, the rotor and the stator can be cooled by the cooling oil that is liquid. Furthermore, in this embodiment, the rotor and the stator can be cooled by ATF. In this embodiment, the cooling medium is oil, but for example, the cooling medium may be gas.

  A temperature sensor 72 for detecting the temperature of the oil 70 is provided at the bottom of the case 65. Further, a temperature sensor 74 is provided in the vicinity of the stator coil 46.2 in order to detect the temperature of the stator of the AC motor M2.

[Motor control mode]
Next, drive control of AC motors M1 and M2 by inverters 14 and 31 will be described in detail.

  In FIG. 7, in the drive control apparatus for an electric motor according to the embodiment of the present invention, the following three control modes are switched and used for control of AC motors M <b> 1 and M <b> 2, that is, power conversion in inverters 14 and 31.

  Sine wave PWM (Pulse Width Modulation) control is used as a general PWM control, and on / off of each phase upper and lower arm elements is compared with the voltage of a sine wave voltage command and a carrier wave (typically triangular wave). Control according to. As a result, for a set of a high level period corresponding to the on period of the upper arm element and a low level period corresponding to the on period of the lower arm element, the duty is set so that the fundamental wave component becomes a sine wave within a certain period. The ratio is controlled. As is well known, in the sine wave PWM control mode in which the correlation waveform of the voltage command is a sine wave, the amplitude of the fundamental wave component can be increased only to about 0.61 times the inverter input voltage.

  On the other hand, in the rectangular wave voltage control, one pulse of a rectangular wave whose ratio between the high level period and the low level period is 1: 1 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 after distorting the amplitude of the voltage command. In the overmodulation PWM control, the modulation factor can be increased from the maximum modulation rate in the sine wave PWM control mode to a range of 0.78 by distorting the fundamental wave component. Thus, the sine wave PWM control and the overmodulation PWM control are included in the “PWM control mode”. Note that the “PWM control mode” may be configured only by the sine wave PWM control without applying the overmodulation PWM control.

  FIG. 8 is a waveform diagram for explaining generation of the switching control signal of the inverter in the PWM control mode.

  Referring to FIG. 8, curve W1 represents a voltage command signal in each phase calculated by a method described later. A curved line W2 is a carrier wave composed of a triangular wave and a sawtooth wave having a predetermined frequency. In the PWM control mode, pulsed switching control signals corresponding to the control signals DRV1 and DRV2 in FIG. 3 are generated according to the voltage level relationship between the voltage command signal W1 and the carrier wave W2. The corresponding phase switching elements in the inverters 14 and 31 perform a complementary switching operation in the upper and lower arms in response to the switching control signal.

  In general, the frequency of the carrier wave corresponding to the switching frequency of the switching element is set to a high frequency of about 5 to 10 kHz in order to avoid an audible frequency band. For this reason, during one rotation of AC motors M1 and M2, the switching operation by the switching element of the inverter is executed many times.

  As a result, as shown in FIG. 9, a harmonic component (ripple current) corresponding to the switching frequency is generated in the inverter output current WV1 in the PWM control mode. Note that the order of the harmonic component is not particularly limited.

  As the harmonic component increases, the fluctuation of the magnetic field penetrating the permanent magnet 54 increases, and the eddy current generated in the permanent magnet 54 increases. As a result, the magnet temperature is likely to rise.

  On the other hand, in the rectangular wave control mode, the switching control signal is a rectangular wave signal having a frequency corresponding to the rotational speed of AC motors M1 and M2. For this reason, the inverter output current WV2 in the rectangular wave control mode does not generate a high frequency component like the inverter output current WV1 in the PWM control mode. As a result, the temperature rise of the permanent magnet 54 due to the eddy current is increased during the PWM control mode, but is relatively decreased during the rectangular wave control mode.

  As shown in FIG. 10, in order to correspond to the induced voltage generated in AC motors M1 and M2, generally, sinusoidal PWM control mode is used to reduce torque fluctuation in operation region A1 at a relatively low rotational speed. Is used, and the over-modulation PWM control mode is applied in the operation region A2 at the medium rotational speed, and the rectangular wave control mode is applied in the operation region A3 at the high rotational speed. In particular, the output of AC motor M1 is improved by applying the overmodulation PWM control mode and the rectangular wave control mode.

  Next, control mode setting of AC motors M1 and M2 according to the motor control device and control method according to the present embodiment will be described in detail.

  FIG. 11 is a functional block diagram illustrating a motor control configuration by the drive control apparatus for an electric motor according to the present embodiment. Each functional block for motor control shown in FIG. 11 can be realized by hardware or software processing by the control device 30. Since the control configuration of each AC motor M1, M2 is the same, FIG. 11 representatively describes the control configuration of AC motor M1.

  Referring to FIG. 11, rectangular wave voltage control unit 300 generates a rectangular wave voltage having a voltage phase such that AC motor M1 outputs torque according to torque command value TR1 when rectangular wave control mode is selected. As described above, the control signal DRV1 for controlling the switching operation of the inverter 14 is generated. The rectangular wave voltage control unit 300 includes a calculation unit 305, a torque detection unit 310, a voltage phase control unit 320, and a rectangular wave generation unit 330.

  PWM control unit 350 generates control signal DRV1 for switching operation in inverter 14 according to pulse width modulation (PWM) control so that AC motor M1 outputs torque according to torque command value TR1 when PWM control mode is selected. To do. The PWM control unit 350 includes a current command generation unit 360, a current control unit 370, and a PWM circuit 380.

  Magnet temperature estimating section 420 estimates the temperature of permanent magnet 54 based on the operating state parameter of AC motor M1. As shown in the figure, the operation state parameters include a torque command value TR1, a rotational speed MRN1, a stator coil temperature Ts, a motor cooling oil temperature Ta, and the like. Details of the temperature estimation method of the permanent magnet 54 will be described later in detail. Magnet temperature estimating section 420 outputs magnet temperature TMG1 calculated by the estimation calculation.

  Determination value setting unit 410 sets a determination value used for mode switching determination of AC motor M1 in mode switching determination unit 400 based on magnet temperature TMG1 from magnet temperature estimation unit 420.

  Mode switching determination unit 400 determines the mode switching between the PWM control mode and the rectangular wave control mode shown in FIG. 3 using the determination value set by determination value setting unit 410. Furthermore, the mode switching determination unit 400 has a function of determining switching between the sine wave PWM control mode and the overmodulation PWM control even during the PWM control mode. When overmodulation PWM control is selected, the control signal OM is turned on. Details of the mode switching determination by the mode switching determination unit 400 will also be described in detail later.

  The changeover switch 405 is set to either the I side or the II side according to the control mode selected by the mode change determination unit 400.

  When the PWM control mode is selected, the changeover switch 405 is set to the I side, and a pseudo sine wave voltage is applied to the AC motor M1 according to the control signal DRV1 set by the PWM control unit 350. On the other hand, when the rectangular wave control mode is selected, the changeover switch 405 is set to the II side, and the rectangular wave voltage is applied to the AC motor M1 by the inverter 14 in accordance with the control signal DRV1 set by the rectangular wave voltage control unit 300. The

Next, the details of the function of each block will be described.
In the rectangular wave voltage control unit 300, the torque detection unit 310 detects the output torque of the AC motor M1. The torque detector 310 can be configured using a known torque sensor, but can also be configured to detect the output torque Tq according to the calculation shown in the following equation (1).

Tq = Pm / ω
= (Iu · vu + iv · vv + iw · vw) / ω (1)
Here, Pm represents the power supplied to AC motor M1, and ω represents the angular velocity of AC motor M1. Further, iu, iv, and iw represent respective phase current values of AC motor M1, and vu, vv, and vw represent respective phase voltages supplied to AC motor M1. The voltage command signal of the inverter 14 may be used for vu, vv, and vw, or an actual value supplied from the inverter 14 to the AC motor M1 may be detected by a voltage sensor. Further, since the output torque Tq is determined by the design value of the AC motor M1, it may be estimated from the amplitude and phase of the current.

  The calculation unit 305 calculates a torque deviation ΔTq that is a deviation of the output torque Tq detected by the torque detection unit 310 with respect to the torque command value TR1. Torque deviation ΔTq generated by calculation unit 305 is supplied to voltage phase control unit 320.

  Voltage phase control unit 320 generates voltage phase φv in accordance with torque deviation ΔTq. This voltage phase φv indicates the phase of a rectangular wave voltage to be applied to AC motor M1. Specifically, the voltage phase control unit 320 uses the input voltage VH of the inverter 14 and the angular velocity ω of the AC motor M1 as well as the torque deviation ΔTq as parameters when generating the voltage phase φv, and converts them into a predetermined arithmetic expression. The necessary voltage phase φv is generated by substituting or performing equivalent processing.

  The rectangular wave generator 330 generates the control signal DRV1 of the inverter 14 so as to generate a rectangular wave voltage according to the voltage phase φv from the voltage phase controller 320. In this manner, the rectangular wave voltage control unit 300 performs feedback control that adjusts the phase of the rectangular wave voltage in accordance with the torque deviation of the AC motor M1. That is, the rectangular wave control mode corresponds to the “first control mode” in the present invention.

  On the other hand, in PWM control unit 350, current command generation unit 360 generates current amplitude | I | and current phase φi based on torque command value TR1. For example, based on proportional integral (PI) control, current control unit 370 determines the difference between motor current MCRT1 detected by current sensor 24, current amplitude | I | generated by current command generation unit 360, and current phase φi. In response, a command value (voltage command signal) for the voltage applied to AC motor M1 is generated. The voltage command signal is represented by its voltage amplitude | V | and voltage phase φv. Here, the voltage phase φv is an angle of a voltage vector with respect to the q axis.

  When the overmodulation PWM control mode in which the control signal OM is turned on is selected, the current control unit 220 distorts the voltage amplitude | V | of the voltage command so that the modulation rate becomes larger than 0.61. Is generated.

  As shown in FIG. 8, the PWM circuit 380 is configured based on a voltage comparison between the voltage command signal W1 and the carrier wave W2 indicated by the voltage amplitude | V | and the voltage phase φv from the current control unit 370. A switching control signal for controlling on / off of the upper and lower arm elements of the phase is generated. In accordance with this switching control signal, a pseudo sine wave voltage is applied to each phase stator coil of AC motor M1.

  In this way, the PWM control unit 350 executes feedback control for making the motor current MCRT1 of the AC motor M1 coincide with the motor current command set by the current command generation unit 360. That is, the PWM control mode corresponds to the “second control mode” in the present invention.

  Here, the details of the mode switching determination by the mode switching determination unit 400 will be described with reference to FIGS. 12 and 13.

  As shown in FIG. 11, for example, the control device 30 executes the program for realizing the control processing according to the flowchart shown in FIG. Is done.

  Referring to FIG. 13, first, control device 30 determines whether or not the current control mode is the PWM control mode in step S100. When the current control mode is the PWM control mode (when YES is determined in S100), control device 30 causes voltage amplitude | V | and voltage phase φv of the voltage command according to PWM control mode, and voltage phase φv in step S110, and Based on the inverter input voltage VH, the modulation factor for converting the input voltage VH of the inverter 14 into a voltage command (AC voltage) to the AC motor M1 is calculated.

  Then, in step S120, control device 30 determines whether or not the modulation factor obtained in step S110 is greater than or equal to determination value kr. When modulation factor ≧ kr (YES in S120), control device 30 advances the process to step S150 and switches the control mode so as to select the rectangular wave control mode.

  As shown in FIG. 7, theoretically, kr = 0.78 is set. That is, when the modulation factor ≧ 0.78, an appropriate AC voltage cannot be generated in the PWM control mode, so it is necessary to switch the control mode so as to select the rectangular wave control mode. Here, if the determination value is changed to kr # (<0.78), the operation region of AC motor M1 to which the rectangular wave control mode is applied is relatively compared with the normal time of determination value kr = 0.78. Can be expanded.

  On the other hand, when the determination in step S120 is NO, that is, when the modulation factor obtained in step S110 is less than kr (when the determination in step S120 is NO), control device 30 continuously selects the PWM control mode in step S160. To do.

  On the other hand, when the current control mode is the rectangular wave control mode (when NO is determined in S100), control device 30 causes AC current phase (actual current phase) supplied from inverter 14 to AC motor M1 in step S130. ) Monitor whether or not the absolute value of φi is smaller than the absolute value of determination value φ0. It should be noted that determination value φ0 may be set to a different value when AC motor M1 is driven (powering) and during regeneration.

  Control device 30 determines that the control mode should be switched from the rectangular wave control mode to the PWM control when the absolute value of actual current phase φi is smaller than the absolute value of determination value φ0 (YES in S130). At this time, control device 30 proceeds to step S160 to select the PWM control mode.

  On the other hand, when step S110 is NO, that is, when the absolute value of actual current phase φi is greater than or equal to the absolute value of determination value φ0, control device 30 maintains the control mode in the rectangular wave control mode in step S150.

  Thereby, as shown in FIG. 12, switching from the rectangular wave control mode to the PWM control mode is determined by comparing the voltage phase φv of the rectangular wave voltage with the determination value φ0. Therefore, if the determination value used in step S130 is changed to φ0 # (| φ0 # | <| φ0 |), compared with the normal value of determination value φ0, AC motor M1 to which the rectangular wave control mode is applied is applied. The operation range can be relatively widened.

  When the PWM control mode is selected, control device 30 determines in step S170 whether the modulation factor is 0.61 or less. The control device 30 selects the sine wave PWM control mode in step S180 when the modulation factor ≦ 0.61, while the control device 30 selects step S190 when the modulation factor> 0.61 (NO in S170). To select the overmodulation PWM control mode. Note that when the PWM control mode is configured only by the sine wave PWM control, steps S170 to S190 are omitted.

  FIG. 14 is a flowchart for explaining the control process by the determination value setting unit 410 of FIG. A program for executing a series of control processes according to the flowchart shown in FIG. 14 is also executed by the control device 30 at predetermined intervals.

  Referring to FIG. 14, control device 30 determines whether or not the temperature of permanent magnet 54 is increasing based on magnet temperature TMG <b> 1 from magnet temperature estimation unit 420 in step S <b> 200. In brief, the determination in step S200 can be executed by comparing the magnet temperature TMG1 with a predetermined threshold value Tth. For example, the threshold value Tth has a margin with respect to a temperature region where irreversible demagnetization occurs in consideration of the magnetic characteristics of the permanent magnet 54, and demagnetization occurs when the temperature rises beyond that. What is necessary is just to set to temperature.

  If magnet temperature TMG1 is equal to or lower than threshold value Tth and it is determined that the temperature increase of permanent magnet 54 does not occur (NO determination in S200), control device 30 proceeds to step S210 and proceeds to the mode. As determination values used in the switching determination unit 400, kr (= 0.78) and φ0, which are normal values, are set.

  On the other hand, when it is determined that magnet temperature TMG1 is higher than threshold value Tth and the temperature of permanent magnet 54 has risen (at the time of YES determination in S200), control device 30 proceeds to step S220, The determination value used in the mode switching determination unit 400 is changed from the normal value to kr # (<0.78) and φ0 # (| φ0 # | <| φ0 |).

  FIG. 15 shows the relationship between the operation range of the AC motor and the applied control mode when the above-described determination value to be compared with FIG. 10 is changed from the normal time.

  Referring to FIG. 15, by changing the determination value from the normal value, for example, the rectangular wave control mode is set to be selected in operation region A2 of AC motor M1 to which the overmodulation PWM control mode is normally applied. it can. Since such an operation region is a relatively high output region, by applying the rectangular wave control mode, it is possible to suppress the temperature rise of the permanent magnet 54 by cutting the high frequency component of the motor current. Alternatively, as shown in the figure, the determination value can be changed so that the application of the rectangular wave control mode is expanded to the operation region to which the sine wave PWM control mode is normally applied.

  Referring to FIG. 14 again, when the temperature rise of permanent magnet 54 occurs once and the determination value is changed to suppress the temperature rise of permanent magnet 54, AC motor M1 shown in FIG. Due to the effect of the circulating cooling system of M2, the magnet temperature TMG1 is expected to return to the threshold value Tth or lower. Thus, when magnet temperature TMG1 falls, step S200 is determined as NO, and the determination value in mode switching determination unit 400 returns to the normal value (kr, φ0). Thereby, the operation region to which the PWM control mode is applied can be returned to the normal range, and the AC motor can be driven with high efficiency. It should be noted that the threshold value at the transition from the non-occurrence state of the permanent magnet 54 to the occurrence state is different from the threshold value at the opposite transition, and hysteresis is provided between the judgments of both transitions. Also good. In this way, it is possible to prevent the setting of the determination value of the mode switching determination unit 400 from being frequently changed in the temperature region near the threshold value.

  FIG. 16 shows a variation of control processing by the determination value setting unit 410 of FIG. A program for executing a series of control processes according to the flowchart shown in FIG. 16 is also executed by the control device 30 at predetermined intervals.

  Referring to FIG. 16, control device 30 determines whether or not the temperature of permanent magnet 54 has increased in step S <b> 200 similar to FIG. 14. When it is determined that the temperature increase of the permanent magnet 54 does not occur (NO determination in S200), the control device 30 determines the determination value used by the mode switching determination unit 400 in step S210 similar to FIG. Is set to a normal value (kr, φ0).

  On the other hand, if it is determined that the temperature of permanent magnet 54 has risen (YES in S200), control device 30 sets the determination value used in mode switching determination unit 400 to the current value in step S222. To a predetermined value in the direction in which the operating range of the AC motor to which the rectangular wave control mode is applied is expanded. In addition, the process by step S222 may introduce | transduce a count value separately, and you may comprise so that it may be performed when the YES determination in step S200 continues predetermined times. By step S222, the determination value used in mode switching determination unit 400 is changed so that the operating range of the AC motor to which the rectangular wave control mode is applied is gradually expanded.

  Further, in step S224, control device 30 determines whether or not the determination value changed in step S222 has reached a preset limit value. If the determination value after the change has reached the limit value (when YES is determined in S224), the temperature increase of the permanent magnet 54 cannot be suppressed only by expanding the application of the rectangular wave control mode. In step S230, the determination value used in mode switching determination unit 400 is maintained at the current value, and a flag for executing load limitation of AC motor M1 is generated.

  Referring to FIG. 11 again, load limiting unit 430 generates a load limiting instruction in response to flag FLM set by determination value setting unit 410 at the time of YES determination in step S224. When this load limit instruction is generated, the temperature rise of the permanent magnet 54 is suppressed in consideration of the magnet temperature TMG1 and the like. Predetermined limits are set for the torque command value and current value of AC motor M1. This degree of restriction may be variable according to the magnet temperature, the vehicle operating condition, or the like.

  Referring to FIG. 16 again, control device 30 uses mode switching determination unit 400 according to step S222 when the changed determination value has not reached the limit value (NO in S224). The judgment value to be changed is changed.

  In this case, the operation range of the AC motor to which the rectangular wave control mode is applied when the temperature of the permanent magnet 54 is increased is executed in stages, and only the application of the rectangular wave control mode cannot be expanded. In addition, the temperature increase of the permanent magnet 54 can be suppressed by the load limitation of the AC motor.

[Estimation of permanent magnet temperature]
Next, the temperature estimation of the permanent magnet by the magnet temperature estimation unit 420 shown in FIG. 11 will be described in detail.

  Since the rotor of the AC motor is configured to be rotatable, if it is attempted to directly detect the temperature of the permanent magnet provided in the rotor using a temperature sensor or the like, the rotor between the rotating rotor and the stationary stator side is used. It is necessary to configure the sensor wiring by a rotary joint or the like. This complicates the structure of the motor.

  FIG. 17 is a diagram for explaining eddy currents generated in a permanent magnet. Referring to FIG. 17, eddy current I is generated in permanent magnet 54 when the magnetic field passing through permanent magnet 54 fluctuates in the direction indicated by the dashed arrow. The eddy current I flows only near the surface of the permanent magnet 54. Since Joule heat is generated by the eddy current I, the temperature of the permanent magnet 54 rises. As the fluctuation of the magnetic field increases, the eddy current I increases. As a result, the temperature of the permanent magnet 54 increases. When the magnetic field penetrating the permanent magnet 54 is constant in time, Joule heat due to eddy current is not generated.

  Based on the difference in structure between AC motors M1 and M2, control device 30 sets first and second parameters corresponding to each of AC motors M1 and M2 from among a plurality of parameters related to the states of AC motors M1 and M2. select. As will be described later, in the present embodiment, the first parameter is the temperature Ta of the oil 70, and the second parameter is the temperature Ts of the stator coil 46.2. Control device 30 estimates the temperature of permanent magnet 54.1 included in AC motor M1 based on temperature Ts, and estimates the temperature of permanent magnet 54.2 included in AC motor M2 based on temperature Ts. By selecting an appropriate parameter from among a plurality of parameters according to the structure of the AC motor, the temperature of the permanent magnet can be estimated more accurately.

  FIG. 18 is a thermal model diagram for explaining the temperature estimation method of magnet temperature estimation section 420 according to the present embodiment.

  As shown in FIG. 18, it is assumed that the magnet temperature, calorific value, and heat capacity are Tm, Qm, and Mm, respectively. Similarly, the rotor temperature, heat generation amount, and heat capacity are assumed to be Tr, Qr, and Mr, respectively. The stator temperature, calorific value, and heat capacity are Ts, Qsm, and Ms, respectively. Let the temperature of the atmosphere (oil) be To. The thermal resistance between the magnet and the rotor, the thermal resistance between the rotor and the stator, the thermal resistance between the stator and the atmosphere, and the thermal resistance between the rotor and the atmosphere are R1, R2, R3, R4, respectively. To do. These parameters used in the thermal model shown in FIG. 18 correspond to a plurality of parameters related to the states of AC motors M1 and M2.

  In this thermal model, the unit of temperature is [° C.]. In this thermal model, the “heat generation amount” is a heat generation amount per second, and its unit is [W] (= [J / second]). Furthermore, the unit of heat capacity is [J / ° C.], and the unit of heat resistance is [° C./W].

When this thermal model is in a steady state, the following relationships (2) to (4) are established.
Qm = (Tm−Tr) / R1 (2)
Qm + Qr = (Tr−Ts) / R2 + (Tr−To) / R4 (3)
Qs = (Ts−To) / R3− (Tr−Ts) / R2 (4)
The following formula (5) is obtained from the above formulas (2) to (4).
Tm = (R1 + R4) Qm + R4 (Qr + Qs) − (R4 / R3) Ts + (1 + R4 / R3) To (5)
Equation (5) indicates that the temperature Tm is a linear function determined by the calorific value and the temperature. Next, the validity of equation (5), that is, the validity of the thermal model in FIG. 18 will be described.

FIG. 19 is a diagram showing a result of applying the thermal model of FIG. 18 to AC motor M1.
Referring to FIG. 19, in the graph, the magnet temperature Tm is an objective variable, and the heat value Qm of the magnet, the heat value Qr of the rotor core, the heat value Qs of the stator, the stator temperature Ts, and the oil temperature To are N explanatory variables. = 36 represents the result of multiple regression analysis. The temperature is an actually measured value, and the calorific value is a calculated value. As a result, in the AC motor M1, a high correlation was obtained between the heat value Qm of the magnet and the oil temperature To.

In the graph of FIG. 19, the horizontal axis indicates the estimated value of the magnet temperature obtained by the regression equation, and the vertical axis indicates the measured value of the magnet temperature. As a result of the multiple regression analysis, the contribution ratio (R ² ) was 0.9059.

  The contribution rate is a value indicating the degree of coincidence between the actually measured value and the estimated value, and is a value in the range of 0 to 1. The closer the contribution rate is to 1, the smaller the difference between the estimated value and the actually measured value. As shown in FIG. 19, a plurality of points indicating the relationship between the estimated value and the actually measured value are distributed in the vicinity of a straight line indicating that the estimated value and the actually measured value are equal.

FIG. 20 is a diagram illustrating a result of applying the thermal model of FIG. 18 to the AC motor M2.
Referring to FIG. 20, the graph uses magnet temperature Tm as an objective variable, N == magnet heat value Qm, rotor core heat value Qr, stator heat value Qs, stator temperature Ts, and oil temperature To as explanatory variables. The results of 36 multiple regression analyzes are shown. As in the case of AC motor M1, the temperature is an actually measured value, and the heat generation amount is a calculated value. As a result, in AC motor M2, a high correlation was obtained between the calorific value Qm of the magnet and stator temperature Ts.

In the graph of FIG. 20, the horizontal axis indicates the estimated value of the magnet temperature obtained by the regression equation, and the vertical axis indicates the measured value of the magnet temperature. As a result of the multiple regression analysis, the contribution ratio (R ² ) was 0.9699. Similarly to FIG. 19, in the graph of FIG. 20, a plurality of points indicating the relationship between the estimated value and the actually measured value are distributed in the vicinity of a straight line indicating that the estimated value and the actually measured value are equal.

  From FIG. 19, it is derived that the AC motor M1 has a high correlation between the magnet temperature and the oil temperature. From FIG. 20, it is derived that the AC motor M2 has a high correlation between the magnet temperature and the stator temperature. The reason why such a result can be obtained is considered as follows.

  In FIG. 6, the temperature of the oil 70 is the ambient temperature of the AC motors M1 and M2. Therefore, if the AC motor continues to be used without changing the operating point of the AC motor, the ambient temperature and the temperature of the permanent magnet are considered to be substantially equal. For this reason, it is thought that the temperature of AC motor M1 and oil temperature have a correlation.

  However, AC motor M2 has a longer axial length than AC motor M1. For this reason, the stator (stator core 40.2 and stator coil 46.2) of AC motor M2 receives a large amount of heat generated from the rotor (the heat receiving area increases). On the other hand, the temperature of the oil 70 reflects the average temperature of the AC motors M1 and M2. Therefore, it is considered that the temperature of the stator coil 46.2 is closer to the temperature of the permanent magnet 54.2 than the temperature of the oil 70.

  In the present embodiment, magnet temperature estimation unit 420 in FIG. 11 stores a map that associates the operating state of AC motor M1 with the magnet temperature, and refers to this map to indicate a permanent magnet included in the rotor of AC motor M1. Estimate the temperature.

FIG. 21 is a diagram showing a map stored in the magnet temperature estimation unit 420.
Referring to FIG. 21, each of maps MP1 to MP4 defines the correspondence between the magnet temperature and the operating point of AC motor M1 determined by the torque and rotational speed of AC motor M1. The oil temperature (temperature Ta) condition differs between maps MP1 to MP4.

  The magnet temperature estimation unit 420 stores a plurality of maps (maps MP1, MP2, MP3, MP4, etc.) that differ for each oil temperature (temperature Ta). The number of maps is not particularly limited, but the larger the number of maps, the more accurately the temperature of the permanent magnet included in the rotor of AC motor M1 can be estimated.

  The magnet temperature estimation unit 420 receives the temperature Ta from the temperature sensor 72 and selects a map corresponding to the temperature Ta from a plurality of maps. Next, magnet temperature estimation unit 420 refers to the map and calculates magnet temperature TMG1 from the operating point on the map determined by torque command value TR1 and motor rotation speed MRN1. FIG. 21 shows 110 ° C., 150 ° C., and 190 ° C. as examples of magnet temperatures defined in the map.

  On the other hand, the method for estimating the magnet temperature of AC motor M2 by magnet temperature estimating section 420 is as follows. The magnet temperature estimation unit 420 stores a correlation expression between the stator temperature and the magnet temperature, which is obtained in advance. Magnet temperature estimating section 420 calculates magnet temperature TMG2 of AC motor M2 based on stator temperature Ts obtained by temperature sensor 74 and its correlation equation.

  Alternatively, the magnet temperature estimation unit 420 can also estimate the temperature of the permanent magnet 54 based on the operation state parameter of the AC motor M1 based on a method other than the above. For example, the temperature change amount of permanent magnet 54 of AC motors M1 and M2 is successively estimated based on torque command value TR1 and rotation speed MRN1, and magnet temperature is calculated based on the integration of the estimated temperature change amount. TMG1 and TMG2 may be calculated.

  As described above, according to the drive control device and the drive control method for an electric motor according to the embodiment of the present invention, the determination value used for switching determination between the rectangular wave control mode and the PWM control mode of AC motors M1 and M2 is a permanent magnet. Motor operating region to which a rectangular wave control mode is applied that can suppress an increase in magnet temperature due to eddy current when the magnet temperature rises by changing the estimated temperature (magnet temperature) of Is expanded. Therefore, the control mode can be switched so as to suppress the temperature increase of the permanent magnet while maintaining the operation of AC motors M1 and M2.

  Furthermore, when the increase of the magnet temperature is difficult due to the adjustment of the control mode switching due to the change of the determination value, it is possible to more reliably prevent the magnet temperature from further rising due to the load limitation of the AC motors M1 and M2. . In other words, the output of AC motors M1 and M2 can be ensured as compared with a control configuration that executes load limitation in direct response to a rise in magnet temperature.

  Further, in the electric vehicle equipped with the drive control device for the electric motor according to the embodiment of the present invention, the temperature increase of the permanent magnet is suppressed while maintaining the situation in which the vehicle driving force can be generated by the operation of AC motors M1 and M2. Thus, control mode switching can be executed.

  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 a schematic block diagram showing an example of a hybrid vehicle equipped with a drive control device for an electric motor according to an embodiment of the present invention. It is a schematic diagram of the power split mechanism shown in FIG. It is a figure which shows the part regarding the drive control of an AC motor in detail in the hybrid vehicle drive device of FIG. It is the schematic explaining the structure of the inverter of FIG. It is a figure which shows the structural example of the principal part of the permanent magnet type motor used for an alternating current motor. It is a figure which shows the cross section of an AC motor typically. It is a key map explaining a plurality of control modes of an AC motor. It is a wave form diagram explaining the production | generation of the switching control signal in a PWM control mode. It is a wave form diagram which shows typically the output current of the inverter in each of PWM control mode and rectangular wave control mode. It is a conceptual diagram which shows roughly the relationship between the driving | operation area | region of an AC motor, and the control mode applied. It is a functional block diagram explaining the motor control structure by the drive control apparatus of the electric motor by this Embodiment. It is a conceptual diagram explaining the control mode switching based on an electric current phase. It is a flowchart explaining the control processing by the mode switching determination part shown in FIG. It is a 1st flowchart explaining the control processing by the judgment value setting part shown in FIG. It is a conceptual diagram which shows roughly the relationship between the driving | operation area | region of the alternating current motor at the time of magnet temperature rise, and the applied control mode. It is a 2nd flowchart explaining the control processing by the determination value setting part shown in FIG. It is a figure for demonstrating the eddy current which arises in a permanent magnet. It is a thermal model figure for demonstrating the temperature estimation method. It is a figure which shows the result of applying the thermal model of FIG. 18 to AC motor M1. It is a figure which shows the result of applying the thermal model of FIG. 18 to AC motor M2. It is a figure which shows the map which the magnet temperature estimation part of FIG. 11 memorize | stores.

Explanation of symbols

  1 Power line, 2 Ground line, 10, 11, 13 Voltage sensor, 14, 31 Inverter, 15 U-phase arm, 16 V-phase arm, 17 W-phase arm, 20 DC / DC converter, 21 Auxiliary battery, 24, 28 Current sensor, 30 control device, 32A, 32B rotation angle detector, 40 stator, 40.1, 40.2 stator core, 46.1, 46.2 stator coil, 50, 50.1, 50.2 rotor core, 52 holes , 54, 54.1, 54.2 Permanent magnet, 60 engine, 65 case, 70 oil (cooling oil), 72, 74 temperature sensor, 100 hybrid vehicle drive device, 200 hybrid vehicle, 210 power split mechanism, 211 ring gear, 212 carrier gear, 213 sun gear, 220 current control unit, 230 drive wheel, 25 , 252, 254 shaft, 253 planetary carrier, 300 rectangular wave voltage control unit, 305 calculation unit, 310 torque detection unit, 320 voltage phase control unit, 330 rectangular wave generation unit, 350 PWM control unit, 360 current command generation unit, 370 Current control unit, 380 PWM circuit, 400 mode switching determination unit, 405 changeover switch, 410 determination value setting unit, 420 magnet temperature estimation unit, 430 load limiting unit, A1, A2, A3 operation region (AC motor), B DC power supply , C1, C2 capacitors, D1-D8 diodes, DRV1, 2 control signal (inverter), FLM flag (load limit), kr, kr # judgment value (modulation factor), L1 reactor, M1, M2 AC motor, MCRT1, MCRT2 Motor current, MP1, MP2, MP3, MP4 , MRN1, MRN2 Motor speed, PWMD, PWMU control signal (converter), Q1-Q8 power semiconductor switching element, SE signal (relay), SR1, SR2 system relay, Ta temperature (cooling oil), TMG1, TMG2 Magnet temperature , TR1, TR2 Torque command value, Ts stator coil temperature, Tth threshold value (magnet temperature), Vb, Vc voltage, VH converter output voltage (system voltage), W1 voltage command signal, W2 carrier wave, WV1, WV2 inverter output Current, θ1, θ2 rotation angle, φ0 judgment value (current phase), φi current phase, φv voltage phase.

Claims (9)

A drive control device for an electric motor having a permanent magnet in a rotor,
A magnet temperature estimator for estimating the temperature of the permanent magnet;
A determination value setting unit for setting a determination value used for switching the control mode of the electric motor according to the magnet temperature estimated by the magnet temperature estimation unit;
A first control mode in which a rectangular wave voltage is applied to the stator winding of the electric motor using the determination value set by the determination value setting unit, and an applied voltage to the stator winding in accordance with pulse width modulation control A mode switching determination unit that determines control mode switching between the second control mode and the second control mode.
The determination value setting unit sets the determination value used in the mode switching determination unit to the first determination value when the magnet temperature is not increased, while the first determination value is set when the magnet temperature is increased. An electric motor drive control device that sets the second determination value such that an operation range of the electric motor to which the first control mode is applied is set to be relatively wide compared to when in use. The determination value setting unit gradually changes the second determination value in a direction in which an operating range of the electric motor to which the first control mode is applied is set relatively wide when the magnet temperature is increased. Let
The drive control device includes:
A load limiting unit for instructing load limitation of the electric motor when the second determination value is changed to a predetermined limit value by the determination value setting unit when the magnet temperature rises. The drive control apparatus for an electric motor according to claim 1.   The determination value setting unit is configured to set the first determination value when the magnet temperature becomes equal to or lower than a predetermined temperature when the second determination value is set. Motor drive control device.   The magnet temperature estimation unit calculates the magnet temperature using at least one of a temperature of a refrigerant used in a circulating cooling system of the electric motor and a stator temperature of the electric motor. The drive control device for the electric motor according to item. The electric motor connected so that the rotor can transmit a driving force to and from wheels;
An electric vehicle comprising the drive control device for an electric motor according to any one of claims 1 to 4. A drive control method for an electric motor having a permanent magnet in a rotor,
Determining a temperature state of the permanent magnet based on temperature estimation of the permanent magnet;
Setting a determination value used for switching the control mode of the electric motor according to a temperature state of the permanent magnet;
A first control mode for applying a rectangular wave voltage to the stator winding of the motor using the set determination value, and a second for controlling the applied voltage to the stator winding according to pulse width modulation control. Determining a control mode switch between the control modes of
The setting step sets the determination value to the first determination value when the temperature of the previous permanent magnet is not increased, and compares the determination value with the use of the first determination value when the temperature of the permanent magnet is increased. Then, the motor drive control method is set to a second determination value such that an operation range of the electric motor to which the first control mode is applied is set relatively wide. In the setting step, when the temperature of the permanent magnet rises, the second determination value is gradually changed in a direction in which an operation range of the electric motor to which the first control mode is applied is set relatively wide. Let
The drive control method includes:
The step of instructing a load limit of the electric motor when the second determination value is changed to a predetermined limit value by the determination value setting unit when the temperature of the permanent magnet is increased. 6. A drive control method for an electric motor according to 6.   8. The motor drive control method according to claim 6, wherein the setting step sets the first determination value when the permanent magnet becomes a predetermined temperature or less when the second determination value is set. 9. .   The estimated temperature value of the permanent magnet is calculated using at least one of a temperature of a refrigerant used in a circulating cooling system of the electric motor and a temperature of the stator. Motor drive control method.

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