JP2010200527A - Control apparatus for motor drive system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control apparatus capable of leveling temperatures of an inverter and an AC motor, in a motor drive system having the AC motor capable of switching the control mode. <P>SOLUTION: The controller 30 calculates the modulation rate which is the ratio of a fundamental wave component of a motor applied voltage to an output voltage VH (DC link voltage of an inverter 14, that is, the system voltage) of a step-up/down converter 12, and determines the need for switching between a rectangular wave voltage control mode and a PWM control mode, based on the calculated modulation rate. According to the relative relation between the temperature of the inverter 14 and the temperature of the AC motor M1 detected by temperature sensors 20, 22, the controller 30 selects a control mode, in which either the rectangular wave voltage control mode or the PWM control mode is to be preferentially applied, and a voltage command value which is the target value of a system voltage VH is corrected so that the modulation rate lies within the range of the modulation rate of the control mode to be applied in priority. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor drive system control device, and more particularly to a motor drive system control device having an AC motor having a plurality of switchable control modes.

  A configuration for driving and controlling an AC motor by converting a DC voltage into an AC voltage by an inverter is generally used. In such a configuration, in order to drive the motor with high efficiency, the motor current is generally controlled according to pulse width modulation (PWM) based on vector control. In addition, in order to improve the motor output, there is a configuration in which the AC motor is controlled by switching between a rectangular wave voltage phase control mode in which a rectangular wave voltage is applied to the AC motor for drive control and a PWM current control mode in accordance with PWM control It is known.

  In Japanese Patent Application Laid-Open No. 2008-131851 (Patent Document 1), first switching means for switching between PWM control and rectangular wave control of an inverter based on the rotational speed or vehicle speed of an AC motor, and the amount of heat generated by the inverter during PWM control. A vehicle drive control device is disclosed that includes a heat generation determination unit that determines whether or not, and a second switching unit that switches between PWM control and rectangular wave control of the inverter based on the heat generation amount of the inverter determined by the heat generation determination unit. . According to Patent Document 1, when the heat generation determination unit determines that the heat generation amount of the inverter exceeds a predetermined value, the heat generation determination unit instructs the second switching unit to switch from PWM control to rectangular wave control. As a result, when the amount of heat generated by the inverter during PWM control is large, the switching frequency of the power element that constitutes the inverter can be lowered, so that the switching loss of the power element can be reduced.

JP 2008-131851 A JP 2004-166415 A Japanese Patent Laid-Open No. 2007-223451

  However, in the vehicle drive control device described in Patent Document 1, the rectangular wave voltage is applied to the AC motor during the rectangular wave control, and therefore, the energization time is increased as compared with the PWM control. This increases the amount of heat generated by the AC motor. As a result, the amount of heat generated by the inverter can be reduced by switching from PWM control to rectangular wave control. On the other hand, there is a possibility that the output torque of the AC motor will decrease due to the increase in the motor temperature, and the running performance of the vehicle will deteriorate.

  SUMMARY OF THE INVENTION Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to equalize the temperature of the inverter and the AC motor in a motor drive system having an AC motor capable of switching the control mode. Is to provide a simple control device.

  A control device for a motor drive system according to the present invention controls a motor drive system including an inverter that converts a DC voltage to be output into an AC voltage for driving an AC motor. The control device performs a feedback control for adjusting a phase of the rectangular wave voltage in accordance with a torque deviation with respect to a torque command value when the first control mode for applying the rectangular wave voltage to the AC motor is selected. And a second motor control unit for performing feedback control of the motor current when the second control mode for controlling the voltage applied to the AC motor according to the pulse width modulation control is selected, and the output voltage of the voltage converter and the AC motor. A mode switching determination unit that calculates a modulation rate of voltage conversion by the inverter based on the applied voltage, and determines whether or not switching between the first and second control modes is necessary based on the calculated modulation rate; A voltage conversion control unit that controls an output voltage of the voltage conversion device. The voltage conversion control unit is configured to generate a voltage command value that is a target value of the output voltage of the voltage converter based on an operation command to the AC motor, and a temperature that acquires the temperatures of the inverter and the AC motor. According to the acquisition means and the relative relationship between the temperature of the inverter and the temperature of the AC motor acquired by the temperature acquisition means, one of the first and second control modes is selected as a control mode to be preferentially applied. Along with the voltage command value correction means for correcting the voltage command value so that the modulation ratio is within the range of the modulation rate of the control mode to be applied with priority, and the voltage command value corrected by the voltage command value correction means, Voltage control means for controlling the output voltage of the voltage converter.

  According to the present invention, in the motor drive system having an AC motor that can switch the control mode, the temperatures of the inverter and the AC motor can be leveled.

1 is an overall configuration diagram of a motor drive system according to an embodiment of the present invention. It is a figure which illustrates schematically the control mode of AC motor M1 in the motor drive system by an embodiment of the invention. It is a figure which shows the correspondence of the operation state of an AC motor, and the control mode shown in FIG. It is a figure which shows the relationship between the switching frequency in an inverter, and the rotation speed of an alternating current motor about each of the control mode shown in FIG. It is a figure for demonstrating schematically the control mode applied preferentially according to the relative relationship of inverter temperature and motor temperature. It is a block diagram explaining the motor control structure by the motor drive system by embodiment of this invention. It is a figure explaining the correspondence of inverter temperature and motor temperature, and a control mode. It is a figure explaining operation | movement of the voltage command correction | amendment part in FIG. It is a flowchart explaining the switching determination process of the control mode according to the embodiment of the present invention.

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

(General configuration of motor control)
FIG. 1 is an overall configuration diagram of a motor drive system according to an embodiment of the present invention.

  Referring to FIG. 1, motor drive system 100 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 motor M1 generates torque for driving the driving 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 motor M1 may be configured to have a function of a generator driven by an engine, or may be configured to have both functions of an electric motor and a generator. Furthermore, AC motor M1 may operate as an electric motor for the engine, and may be incorporated in a hybrid vehicle so that the engine can be started, for example.

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

  The DC power 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.

  Buck-boost 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 one end of three U, V, and W phase coils is commonly connected 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.

  In the step-up operation, the step-up / down converter 12 boosts a DC voltage VH obtained by boosting the DC voltage Vb supplied from the DC power supply B (this DC voltage corresponding to the input voltage to the inverter 14 is hereinafter also referred to as “system voltage”). Supply to the inverter 14. More specifically, in response to switching control signals S1 and S2 from controller 30, switching element Q1 is turned on and switching element Q2 is turned on (or both switching elements Q1 and Q2 are turned off). ) Are alternately provided, and the step-up ratio is in accordance with the ratio of these ON periods. Alternatively, if switching elements Q1 and Q2 are fixed to ON and OFF, respectively, VH = Vb (step-up ratio = 1.0) can be obtained.

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

  Smoothing capacitor C0 smoothes the DC voltage from step-up / down converter 12, and supplies the smoothed DC voltage to inverter 14. The voltage sensor 13 detects the voltage across the smoothing capacitor C 0, that is, the system voltage 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 is switched in response to switching control signals S3 to S8 from control device 30 when a DC voltage is supplied from smoothing capacitor C0. The AC motor M1 is driven so as to convert a DC voltage into an AC voltage and output a positive torque by the switching operation of the elements Q3 to Q8. Further, when the torque command value of AC motor M1 is zero (Trqcom = 0), inverter 14 converts the DC voltage to the AC voltage by the switching operation in response to switching control signals S3 to S8, and the torque is zero. The AC motor M1 is driven so that Thus, AC motor M1 is driven to generate zero or positive torque designated by torque command value Trqcom.

  Further, during regenerative braking of an electric vehicle equipped with motor drive system 100, torque command value Trqcom of AC motor M1 is set to be negative (Trqcom <0). In this case, the inverter 14 converts the AC voltage generated by the AC motor M1 into a DC voltage by a switching operation in response to the switching control signals S3 to S8, and converts the converted DC voltage (system voltage) to the smoothing capacitor C0. To the step-up / down converter 12. 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 motor M <b> 1 and outputs the detected motor current to control device 30. Since the sum of instantaneous values of the three-phase currents iu, iv, and iw is zero, the current sensor 24 has a motor current for two phases (for example, a V-phase current iv and a W-phase current iw) as shown in FIG. It is sufficient to arrange it so as to detect.

  The rotation angle sensor (resolver) 25 detects the rotor rotation angle θ of the AC motor M1, and sends the detected rotation angle θ to the control device 30. The control device 30 can calculate the rotational speed (rotational speed) Nmt and the angular speed ω (rad / s) of the AC motor M1 based on the 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.

  Temperature sensor 20 detects the temperature (hereinafter referred to as “inverter temperature”) Tinv of switching elements Q <b> 3 to Q <b> 8 of inverter 14 and outputs the detected inverter temperature Tinv to control device 30. The temperature sensor 22 detects the temperature (hereinafter referred to as “motor temperature”) Tmot of the AC motor M <b> 1 and outputs the detected motor temperature Tmot to the control device 30. Note that the temperature sensor 22 is generally provided so as to measure the temperature of the coil winding part where there is a concern about the breakdown of the insulation coating due to the temperature rise and to output at least to the control device 30.

  The control device 30 is composed of an electronic control unit (ECU), and operates the motor drive system 100 by software processing by executing a pre-stored program by a CPU (not shown) and / or hardware processing by a dedicated electronic circuit. To control.

  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 operation of the step-up / down converter 12 and the inverter 14 is controlled. That is, the switching control signals S1 to S8 for controlling the buck-boost converter 12 and the inverter 14 as described above are generated and output to the buck-boost converter 12 and the inverter 14.

  During the step-up operation of buck-boost 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 ECU, switching control signals S3 to S3 convert the AC voltage generated by AC motor M1 into a DC voltage. S8 is 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 step-up / down converter 12.

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

(Description of control mode)
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 motor M1 in motor drive system 100 according to the embodiment of the present invention.

  As shown in FIG. 2, in motor drive system 100 according to the embodiment of the present invention, three control modes are switched and used for control of AC motor M <b> 1, that is, power conversion in inverter 14.

  The sine wave PWM control is used as a general PWM control, and controls on / off of each phase upper and lower arm elements according to a voltage comparison between a sine wave voltage command and a carrier wave (typically a triangular wave). . As a result, for a set of a high level period corresponding to the on period of the upper arm element and a low level period corresponding to the on period of the lower arm element, the duty is set so that the fundamental wave component becomes a sine wave within a certain period. Is controlled. As is well known, in the sine wave PWM control in which the amplitude of the sinusoidal voltage command is limited to a range below the carrier wave amplitude, the fundamental wave of the 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 sine wave voltage command is in the range of the carrier wave amplitude or less, 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. In this control method, a period in which the voltage command becomes higher than the carrier wave amplitude occurs due to the harmonic component. However, since the 3n-order harmonic component superimposed on each phase is canceled between lines, the line voltage is a sine wave. It will be maintained. In the present embodiment, this control method is also included in the sine wave PWM control.

  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 M1 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 larger 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 step-up / down converter 12, that is, the system voltage VH needs to be set higher than this motor required voltage. On the other hand, there is a limit value (VH maximum voltage) in the boosted voltage by the buck-boost converter 12, that is, the 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 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 motor M1 and the above-described control mode.
Referring to FIG. 3, schematically, sinusoidal PWM control is used in order to reduce the torque fluctuation in the low rotational speed range A1, overmodulation PWM control in the intermediate rotational speed range A2, and in the high rotational speed range A3. Square wave voltage control is applied. In particular, the output of AC motor M1 is improved by applying overmodulation PWM control and rectangular wave voltage control. 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.

  In motor drive system 100 configured as described above, when switching elements Q3 to Q8 of inverter 14 perform a switching operation in response to switching control signals S3 to S8, switching loss occurs and the temperature of switching elements Q3 to Q8 rises. To do. Note that this switching loss increases as the switching frequency increases so that the number of times of switching increases.

  FIG. 4 shows the relationship between the switching frequency in inverter 14 and the rotational speed of AC motor M1 for each of the control modes described above. The line L1 in the figure shows the relationship between the switching frequency and the motor speed in the PWM control mode, and the line L2 in the figure shows the relation between the switching frequency and the motor speed in the rectangular wave voltage control mode.

  Referring to FIG. 4, in the PWM control mode, generally, pulsed switching control signals S3 to S8 are generated according to the level relationship between the voltage of the carrier wave (carrier wave) and the voltage command signal in each phase. . Therefore, the switching frequency of the switching elements Q3 to Q8 depends on the frequency of the carrier wave. The frequency of the carrier wave 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 motor M1, the switching operation by switching elements Q3 to Q8 of inverter 14 is executed many times.

  On the other hand, in the rectangular wave voltage control mode, the switching control signals S3 to S8 are rectangular wave signals having a frequency corresponding to the rotational speed of the AC motor M1. Therefore, in the rectangular wave voltage control mode, the switching frequency is proportional to the rotational speed of AC motor M1, and is relatively lower than the switching frequency in PWM control mode. Therefore, the switching loss that occurs in the rectangular wave voltage control mode is relatively smaller than the switching loss that occurs in the PWM control mode. Therefore, when the temperature of the inverter 14 rises during the PWM control mode, the amount of heat generated by the inverter 14 can be relatively reduced by switching the control mode from the PWM control mode to the rectangular wave voltage control mode. It becomes.

  However, on the other hand, in the rectangular wave voltage control mode, since the rectangular wave voltage is applied to the AC motor M1, the energization time to the AC motor M1 increases as compared with the PWM control mode. As a result, the amount of heat generated in AC motor M1 is relatively increased, and there is a possibility that the output torque of AC motor M1 is reduced due to an increase in motor temperature.

  Therefore, in order to appropriately suppress the temperature rise of inverter 14 and AC motor M1, control device 30 according to the embodiment of the present invention uses relative values of inverter temperature Tinv and motor temperature Tmot detected by temperature sensors 20 and 22, respectively. Depending on the relationship, either the PWM control mode or the rectangular wave voltage control mode is preferentially applied.

  FIG. 5 is a diagram for schematically explaining a control mode applied with priority in accordance with the relative relationship between the inverter temperature Tinv and the motor temperature Tmot.

  Referring to FIG. 5, in the relative relationship between the inverter temperature and the motor temperature, a region where the rectangular wave voltage control mode is prioritized and a region where the PWM control mode is prioritized are provided. Specifically, the rectangular wave voltage control mode is preferentially applied in a region where the inverter temperature is high while the motor temperature is low (corresponding to region A4 in the figure). That is, when it is determined that the temperature rise of the inverter 14 needs to be suppressed, the rectangular wave voltage control is preferentially applied. Thereby, since the switching loss which generate | occur | produces in the inverter 14 reduces, the emitted-heat amount of the inverter 14 can be reduced.

  On the other hand, in a region where the motor temperature is high and the inverter temperature is low (corresponding to region A5 in the figure), the PWM control mode is preferentially applied. That is, when it is determined that the temperature increase of AC motor M1 needs to be suppressed, PWM control is preferentially applied. Thereby, since the energization time of AC motor M1 becomes short, the calorific value of AC motor M1 can be reduced.

  As described above, according to the embodiment of the present invention, the heating element (inverter 14 or AC motor M1) that is determined to be required to suppress the temperature rise according to the relative relationship between the inverter temperature Tinv and the motor temperature Tmot. The control mode is switched so as to reduce the amount of heat generated. Thereby, the temperature of inverter 14 and AC motor M1 can be leveled.

  Hereinafter, the control mode switching process of AC motor M1 according to the control device for the motor drive system according to the embodiment of the present invention will be described in detail.

  FIG. 6 is a block diagram illustrating a motor control configuration by the motor drive system according to the embodiment of the present invention. Each functional block for motor control shown in FIG. 6 can be realized by hardware or software processing by the control device 30.

  Referring to FIG. 6, PWM control unit 300 switches inverter 14 according to pulse width modulation (PWM) control so that AC motor M1 outputs torque according to torque command value Trqcom when PWM control mode is selected. Control signals S3 to S8 are generated.

  Specifically, PWM control unit 300 includes a current command generation unit 302, a current control unit 304, and a PWM circuit 306.

  Current command generator 302 generates current amplitude | I | and current phase φi based on torque command value Trqcom. The current control unit 304 is based on the difference between the motor current MCRT detected by the current sensor 24 and the current amplitude | I | and the current phase φi generated by the current command generation unit 302 based on, for example, proportional integral (PI) control. In response, a command value (hereinafter also simply referred to as a voltage command) for the voltage applied to AC motor M1 is generated. The voltage command 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 in which the control signal OM is turned on is selected, the current control unit 304 distorts the voltage amplitude | V | of the voltage command so that the modulation factor becomes larger than 0.61. Generate directives.

  The PWM circuit 306 controls on / off of the upper and lower arm elements of each phase of the inverter 14 based on the comparison between the voltage command indicated by the voltage amplitude | V | and the voltage phase φv from the voltage control unit 304 and the carrier wave. Thus, a pseudo sine wave voltage is generated in each phase of AC motor M1.

  In this manner, the PWM control unit 300 performs feedback control for matching the motor current MCRT of the AC motor M1 with the motor current set by the current command generation unit 302. That is, the PWM control unit 300 corresponds to the “second motor control unit” in the present invention, and the PWM control mode corresponds to the “second control mode” in the present invention.

  When the rectangular wave voltage control mode is selected, the rectangular wave voltage control unit 400 generates a rectangular wave voltage having a voltage phase such that the AC motor M1 outputs a torque according to the torque command value Trqcom. Switching control signals S3 to S8 are generated.

  Specifically, the rectangular wave voltage control unit 400 includes a calculation unit 404, a torque detection unit 402, a voltage phase control unit 406, and a rectangular wave generation unit 408.

  Torque detector 402 detects the output torque of AC motor M1. The torque detection unit 402 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. A voltage command set in 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.

  Calculation unit 404 calculates a torque deviation ΔTq, which is a deviation of output torque Tq detected by torque detection unit 402 with respect to torque command value Trqcom. Torque deviation ΔTq generated by calculation unit 404 is supplied to voltage phase control unit 406.

  The voltage phase control unit 406 generates a voltage phase φv according to the 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 406 uses the input voltage (system voltage) VH of the inverter 14 and the angular velocity ω of the AC motor M1 together with the torque deviation ΔTq as parameters when generating the voltage phase φv, and sets them as predetermined. The necessary voltage phase φv is generated by substituting into the above equation or performing equivalent processing.

  The rectangular wave generator 408 generates the switching control signals S3 to S8 of the inverter 14 so as to generate a rectangular wave voltage according to the voltage phase φv from the voltage phase controller 406. In this manner, the rectangular wave voltage control unit 400 performs feedback control for adjusting the phase of the rectangular wave voltage in accordance with the torque deviation of the AC motor M1. That is, the rectangular wave voltage control unit 400 corresponds to the “first motor control unit” in the present invention, and the rectangular wave voltage control mode corresponds to the “first control mode” in the present invention.

  Voltage conversion control unit 200 determines whether AC motor M1 is torque based on torque command value Trqcom and rotation speed Nmt of AC motor M1, DC voltage Vb detected by voltage sensor 10, and system voltage VH detected by voltage sensor 13. The operation of the step-up / down converter 12 is controlled so as to output a torque according to the command value Trqcom.

  At this time, the voltage conversion control unit 200 selects a control mode to be prioritized according to a preset map according to the relative relationship between the inverter temperature Tinv and the motor temperature Tmot detected by the temperature sensors 20 and 22. Voltage conversion control unit 200 corrects voltage command value VH # of the system voltage so that the modulation factor calculated by mode switching determination unit 500 falls within the modulation factor range of the selected control mode.

  Specifically, voltage conversion control unit 200 includes a voltage command generation unit 202, a voltage command correction unit 204, and a converter PWM circuit 206.

  Based on torque command value Trqcom and motor rotation speed Nmt, voltage command generation unit 202 calculates a target value of system voltage VH, that is, voltage command value VH #, and corrects the calculated voltage command value VH # to voltage command correction. Output to the unit 204.

  Voltage command correction unit 204 corrects voltage command value VH # (calculated value) according to inverter temperature Tinv detected by temperature sensor 20 and motor temperature Tmot detected by temperature sensor 22. Then, the corrected voltage command value VH # is output to converter PWM circuit 206.

  At this time, as described above, the voltage command correction unit 204 selects a control mode to be prioritized according to the relative relationship between the inverter temperature Tinv and the motor temperature Tmot. FIG. 7 shows a correspondence relationship between the inverter temperature Tinv and the motor temperature Tmot and the control mode. Referring to FIG. 7, when inverter temperature Tinv is lower than predetermined value A and motor temperature Tmot is lower than predetermined value B, both the PWM control mode and the rectangular wave voltage control mode should be prioritized. Not selected for mode. In this case, voltage command correction unit 204 outputs voltage command value VH # (calculated value) to converter PWM circuit 206 without correcting it.

  On the other hand, when the motor temperature Tmot is equal to or higher than the predetermined value A and the inverter temperature Tinv is lower than the predetermined value B, the PWM control mode is selected as the control mode to be prioritized. In this case, as shown in FIG. 8, voltage command correction unit 204 corrects voltage command value VH # to be a voltage value higher than voltage command value VH # (calculated value). The correction amount of voltage command value VH # is such that the modulation factor calculated based on corrected voltage command value VH # is within the modulation factor range in the PWM control mode (for example, a range of 0 to 0.78). It is adjusted to become.

  Further, when the motor temperature Tmot is lower than the predetermined value A and the inverter temperature Tinv is equal to or higher than the predetermined value B, the rectangular wave voltage control mode is selected as the control mode to be prioritized. In this case, as shown in FIG. 8, voltage command correction unit 204 corrects voltage command value VH # so as to be a voltage value lower than voltage command value VH # (calculated value). The correction amount of voltage command value VH # is such that the modulation factor calculated based on corrected voltage command value VH # is within the modulation factor range (for example, 0.78 or more) in the rectangular wave voltage control mode. To be adjusted.

  When the motor temperature Tmot is equal to or higher than the predetermined value A and the inverter temperature Tinv is equal to or higher than the predetermined value B, the deviation of the motor temperature Tmot relative to the predetermined value A and the deviation of the inverter temperature Tinv from the predetermined value B Depending on the magnitude relationship, either the PWM control mode or the rectangular wave voltage control mode is selected as the priority control mode.

  Referring again to FIG. 6, voltage command correction unit 204 outputs corrected voltage command value VH # to converter PWM circuit 206 when voltage command value VH # is corrected in accordance with the control mode to be prioritized. Converter PWM circuit 206 sets system voltage VH to voltage command value VH # based on DC voltage Vb from voltage sensor 10, voltage command value VH #, and system voltage VH from voltage sensor 13. And the switching control signals S1 and S2 for on / off control of the switching elements Q1 and Q2 of the step-up / down converter 12 are generated based on the calculated duty ratio and output to the step-up / down converter 12. .

  Mode switching determination unit 500 determines mode switching between the PWM control mode and the rectangular wave voltage control mode. Furthermore, mode switching determination unit 500 has a function of determining switching between sine wave PWM control and overmodulation PWM control even in the PWM control mode. When overmodulation PWM control is selected, the control signal OM is turned on.

  The changeover switch 510 is set to either the I side or the II side according to the control mode selected by the mode change determination unit 500. Specifically, when the PWM control mode is selected, the changeover switch 510 is set to the I side, and the pseudo sine wave voltage is changed to the AC motor M1 according to the switching control signals S3 to S8 set by the PWM control unit 300. To be applied. On the other hand, when the rectangular wave voltage control mode is selected, the changeover switch 510 is set to the II side, and the rectangular wave voltage is changed by the inverter 14 according to the switching control signals S3 to S8 set by the rectangular wave voltage control unit 400. Applied to M1.

  Here, as shown in FIG. 6, the mode switching determination unit 500 includes a motor current MCRT detected by the current sensor 24, a system voltage VH detected by the voltage sensor 13, and a voltage command generated by the current control unit 304. Based on the voltage amplitude | V | and the voltage phase φv, the mode switching determination is executed. For example, the mode switching determination by the mode switching determination unit 500 is realized by the control device 30 executing a control process according to the flowchart shown in FIG.

  Referring to FIG. 9, first, control device 30 calculates a target value (voltage command value VH #) of system voltage VH based on torque command value Trqcom and rotation speed Nmt of AC motor M1 (step S01).

  Next, when the inverter temperature Tinv and the motor temperature Tmot detected by the temperature sensors 20 and 22 are acquired (step S02), the control device 30 performs control to be prioritized according to the relative relationship between the inverter temperature Tinv and the motor temperature Tmot. Select a mode. Then, voltage command value VH # is corrected so that the modulation rate when system voltage VH is converted into a voltage command to AC motor M1 is within the modulation rate range of the selected control mode (step S03). Then, control device 30 feedback-controls system voltage VH, and generates switching control signals S1 and S2 so that system voltage VH matches corrected voltage command value VH # (step S04).

  Next, the control device 30 determines whether or not the current control mode is the PWM control mode (step S05). When the current control mode is the PWM control mode (when YES is determined in step S05), control device 30 determines voltage amplitude | V | and voltage phase φv of the voltage command according to PWM control mode, and system voltage VH. Based on the above, the modulation factor for converting the system voltage VH into a voltage command to the AC motor M1 is calculated (step S06).

  And the control apparatus 30 determines whether the modulation factor calculated | required by step S06 is 0.78 or more (step S07). When the modulation factor ≧ 0.78 (when YES is determined in step S07), since the appropriate AC voltage cannot be generated in the PWM control mode, the control device 30 advances the process to step S10 to generate a rectangular wave. The control mode is switched to select the voltage control mode.

  On the other hand, when NO is determined in step S07, that is, when the modulation factor obtained in step S06 is less than 0.78, control device 30 continuously selects the PWM control mode. At this time, although not shown, the control device 30 further determines whether or not the modulation rate is 0.61 or less. Control device 30 selects sine wave PWM control when the modulation factor ≦ 0.61, while selecting overmodulation PWM control when modulation factor> 0.61.

  On the other hand, when current control mode is rectangular wave voltage control mode (when NO is determined in step S05), control device 30 provides AC current phase (actual current phase) φi supplied from inverter 14 to AC motor M1. It is monitored whether the absolute value of becomes smaller than the absolute value of the predetermined switching current phase φ0. Switching current phase φ0 may be set to a different value when AC motor M1 is driven (powering) and during regeneration.

  When the absolute value of actual current phase φi is smaller than the absolute value of switching current phase φ0 (when YES is determined in step S09), control device 30 determines that the control mode should be switched from the rectangular wave voltage control mode to the PWM control mode. Then, the PWM control mode is selected (step S08). When the PWM control mode is selected, it is determined which of the PWM control modes, sine wave PWM control or overmodulation PWM control should be selected.

  On the other hand, control device 30 maintains the control mode in the rectangular wave voltage control mode when step S09 is NO, that is, when actual current phase φi is greater than or equal to the absolute value of switching current phase φ0 (step S10).

  As described above, according to the control device for the motor drive system according to the present embodiment, in the configuration in which the input voltage (system voltage VH) to inverter 14 can be variably controlled, the temperature is determined according to the relative relationship between the inverter temperature and the motor temperature. A control mode to be prioritized is selected in order to reduce the amount of heat generated by the heating element (inverter 14 or AC motor M1) for which it is determined that suppression of the increase is necessary. Then, switching to the selected control mode is performed by correcting voltage command value VH # of the system voltage. Thereby, the temperature of inverter 14 and AC motor M1 can be leveled.

  In the present embodiment, the inverter temperature Tinv and the motor temperature Tmot are acquired by the temperature sensors 20 and 22 as means for acquiring the inverter temperature Tinv and the motor temperature Tmot, respectively. The inverter temperature and the motor temperature may be estimated based on this.

  Further, as a preferred configuration example, a configuration has been shown in which DC voltage generation unit 10 # of motor drive system 100 includes buck-boost converter 12 so that the input voltage (system voltage VH) of inverter 14 can be variably controlled. DC voltage generation unit 10 # is not limited to the configuration exemplified in this embodiment as long as the input voltage to 14 can be variably controlled.

  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.

  5 Ground wire, 6, 7 Power line, 10 # DC voltage generator, 10, 13 Voltage sensor, 11, 24 Current sensor, 12 Buck-boost converter, 14 Inverter, 15 U phase upper and lower arm, 16 V phase upper and lower arm, 17 W Phase upper and lower arms, 20, 22 Temperature sensor, 25 Rotation angle sensor, 30 Control device, 100 Motor drive system, 200 Voltage conversion control unit, 202 Voltage command generation unit, 204 Voltage command correction unit, 206 PWM circuit for converter, 300 PWM Control unit 302 current command generation unit 304 voltage control unit 304 current control unit 306 PWM circuit 400 rectangular wave voltage control unit 402 torque detection unit 404 calculation unit 406 voltage phase control unit 408 rectangular wave generation unit , 500 mode change determination unit, 510 changeover switch, B DC power supply, C0, First smoothing capacitor, D1 to D8 anti-parallel diode, L1 reactor, M1 AC motor, a semiconductor switching element for Q1~Q8 power, SR1, SR2 system relay.

Claims (1)

Control device for motor drive system comprising DC power supply, voltage converter capable of boosting output of DC power supply, and inverter for converting DC voltage output from voltage converter into AC voltage for AC motor drive Because
A first motor control unit that performs feedback control for adjusting a phase of the rectangular wave voltage in accordance with a torque deviation with respect to a torque command value when a first control mode for applying a rectangular wave voltage to the AC motor is selected;
A second motor control unit for performing feedback control of motor current when selecting a second control mode for controlling the voltage applied to the AC motor according to pulse width modulation control;
Based on the output voltage of the voltage converter and the voltage applied to the AC motor, the modulation rate of the voltage conversion by the inverter is calculated, and based on the calculated modulation rate, between the first and second control modes. A mode switching determination unit that determines whether or not switching is required;
A voltage conversion control unit for controlling the output voltage of the voltage converter,
The voltage conversion controller is
Voltage command value generating means for generating a voltage command value that is a target value of the output voltage of the voltage converter based on an operation command to the AC motor;
Temperature acquisition means for acquiring temperatures of the inverter and the AC motor;
Depending on the relative relationship between the temperature of the inverter acquired by the temperature acquisition means and the temperature of the AC motor, one of the first and second control modes is preferentially selected as the control mode to be applied. And voltage command value correction means for correcting the voltage command value so that the modulation rate falls within the range of the modulation rate of the control mode to be applied with priority.
And a voltage control means for controlling an output voltage of the voltage converter according to the voltage command value corrected by the voltage command value correction means.

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