JP2014128098A - Control system for ac motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately set a DC link voltage of an inverter for preventing a load of a power storage device from becoming excessive, in a power supply system for an AC motor in which a converter is disposed between the power storage device and the inverter.SOLUTION: A step-up converter 12 executes bidirectional DC power conversion so as to control a system voltage VH in accordance with a voltage command value between a power storage device B and a power line 7 at a DC link side of an inverter 14. The inverter 14 converts the system voltage VH on the power line 7 into an AC voltage to be applied to an AC motor M1. A control device 50 fundamentally sets the system voltage VH in accordance with states of the inverter 14 and the AC motor M1. Further, the control device 50 is configured to increase the system voltage VH higher than a preset value based on the states of the inverter 14 and the AC motor M1 in accordance with output allowance of the power storage device B.

Description

  The present invention relates to an AC motor control system, and more particularly to a control system that variably controls a DC link voltage of an inverter that drives the AC motor by a converter.

  In order to control an AC motor using a DC power source, a control system using an inverter is generally used. For example, Japanese Patent Laying-Open No. 2010-252488 (Patent Document 1) describes a configuration in which a DC link voltage of an inverter is variably controlled by a converter connected between a battery (power storage device) and the inverter.

  In the above-mentioned Patent Document 1, in the control of an AC motor that selectively applies pulse width modulation (PWM) control and rectangular wave voltage control, the motor is calculated based on the torque command value of the AC motor when the converter is in the non-boosting mode. There is described control for requesting the converter to start a boost operation when the degree of modulation obtained from the output voltage and the system voltage command value exceeds a predetermined value.

JP 2010-252488 A JP 2011-223719 A

  Patent Document 1 describes a configuration in which an output voltage of a converter, that is, a DC link voltage of an inverter, is variably controlled according to a modulation degree of DC / AC voltage conversion in the inverter, including the necessity of boosting in the converter. .

  However, if the output voltage of the converter (DC link voltage of the inverter) is set without considering the output state of the battery (power storage device), there is a possibility that the load on the battery becomes excessive in order to increase the output voltage. . As a result, the voltage of the battery may be excessively lowered, or the necessary electric power may not be supplied to the AC motor.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a power source for an AC motor having a configuration in which a converter can control a DC link voltage of an inverter using a power storage device as a power source. In the system, the DC link voltage of the inverter is appropriately set so that the load of the power storage device does not become excessive.

  In one aspect of the present invention, a control system for an AC motor mounted on an electric vehicle includes a power storage device, a boost converter, an inverter, and first and second control means. The boost converter is configured to perform bidirectional DC power conversion between the power storage device and the power line so that the DC voltage of the power line is controlled according to the voltage command value. The inverter is configured to convert a DC voltage on the power line into an AC voltage applied to the AC motor. The first control means sets the DC voltage according to the state of the AC motor and the inverter. The second control means sets the DC voltage higher than the voltage set by the first control means in accordance with the output margin of the power storage device.

  Preferably, in the non-boosting mode in which the step-up ratio indicated by the ratio of the DC voltage to the output voltage of the power storage device is fixed to 1, the first control means has a modulation factor indicated by the ratio of the AC voltage to the DC voltage or AC When the current phase of the electric motor advances from a predetermined phase, the boost converter is controlled to select a boost mode in which a voltage command value is set so that the boost ratio is higher than 1. When the output voltage of the power storage device falls below a predetermined voltage when the first control means selects the non-boosting mode, the second control means increases the DC voltage by shifting to the boosting mode.

  More preferably, the predetermined voltage is higher than the management lower limit voltage of the power storage device. The voltage difference between the predetermined voltage and the management lower limit voltage is set based on the amount of voltage drop that occurs in the power storage device at the maximum output of the AC motor.

  Preferably, the first control means sets the modulation degree indicated by the ratio of the AC voltage to the DC voltage as a target modulation in the boost mode in which the boost ratio indicated by the ratio of the DC voltage to the output voltage of the power storage device is greater than 1. Set the voltage command value of the boost converter so that it approaches. When the second control means detects an increase in the output of the AC motor, the voltage control value is set by the first control means according to the power margin that can be additionally output from the power storage device to the AC motor. Than to raise.

  More preferably, the second control means detects an increase in output in response to the accelerator opening degree of the electric vehicle exceeding a predetermined threshold, and increases the voltage command value by decreasing the target modulation degree.

  More preferably, the second control means detects an increase in output in response to the torque command value to the AC motor exceeding a predetermined threshold, and reduces the target modulation degree to reduce the voltage command value. Raise.

  According to the present invention, in the AC motor power supply system having a configuration in which the converter can control the DC link voltage of the inverter using the power storage device as a power source, the DC link voltage of the inverter is appropriately set so that the load of the power storage device does not become excessive. Can be set to

1 is an overall configuration diagram of an AC motor control system according to an embodiment of the present invention. FIG. It is a figure explaining the control mode for AC motor control. It is a functional block diagram explaining the control structure in PWM control in the control system of the AC motor according to the embodiment of the present invention. It is a functional block diagram explaining the control structure in the rectangular wave voltage control in the control system of the AC motor according to the embodiment of the present invention. It is a conceptual diagram for demonstrating the voltage phase-torque characteristic in rectangular wave voltage control. The conceptual diagram for demonstrating the relationship between the operating point of an AC motor and the control mode applied is shown. It is a figure which shows the change of the electric current phase of AC electric motor M1 accompanying switching of a control mode. It is a transition diagram for demonstrating mode switching between PWM control and rectangular wave voltage control. It is a conceptual diagram for demonstrating the behavior of the control system according to the change of the system voltage VH through three control modes. FIG. 6 is an operation waveform diagram for explaining problems that occur when shifting from the non-boosting mode to the boosting mode. FIG. 5 is a functional block diagram illustrating a control configuration for selecting a boost mode / non-boost mode in an AC motor control system according to the first embodiment of the present invention. 12 is a flowchart for illustrating a control processing operation by a first boost determination unit shown in FIG. 11. 12 is a flowchart for illustrating a control processing operation by a second boost determination unit shown in FIG. 11. It is a flowchart for demonstrating the control processing operation | movement by the arbitration process part shown by FIG. 12 is a flowchart for explaining a control processing operation by a minimum voltage setting unit shown in FIG. FIG. 11 is an operation waveform diagram illustrating a control operation when shifting from the non-boosting mode to the boosting mode when the selection of the boosting mode / boosting mode according to the first embodiment is applied. It is a functional block diagram for demonstrating the comparative example of the system voltage command value setting part for setting the voltage command value of the system voltage in a pressure | voltage rise mode. It is a conceptual diagram explaining the structural example of the Vr * map shown by FIG. It is a wave form diagram which shows the operation example according to the comparative example at the time of the output increase of the alternating current motor in pressure | voltage rise mode. It is a functional block diagram for demonstrating the system voltage command value setting part according to Embodiment 2 of this invention. It is a wave form diagram which shows the operation example according to Embodiment 2 at the time of the output increase of the alternating current motor in pressure | voltage rise mode. It is a functional block diagram for demonstrating the system voltage command value setting part at the time of rectangular wave voltage control application according to Embodiment 2 of this invention. It is a conceptual diagram explaining the structural example of the voltage deviation calculation map shown in FIG.

  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 the description thereof will not be repeated in principle.

[Embodiment 1]
(System configuration)
FIG. 1 is an overall configuration diagram of an AC motor control system according to an embodiment of the present invention.

  Referring to FIG. 1, control system 100 that controls AC electric motor M <b> 1 includes DC voltage generation unit 10, smoothing capacitor C <b> 0, inverter 14, and control device 30.

  AC motor M1 generates torque on the drive wheels of an electric vehicle (a vehicle that can generate vehicle driving force by electric energy such as a hybrid vehicle, an electric vehicle, and a fuel cell vehicle). It is the comprised electric motor for driving | running | working. Alternatively, AC electric motor M1 may be configured to have a function of a generator driven by an engine, or may be configured to have both functions of an electric motor and a generator. Further, AC electric motor M1 may operate as an electric motor for the engine, and may be incorporated in a hybrid vehicle as one that can start the engine, for example. That is, in the present embodiment, the “AC motor” includes an AC drive motor, a generator, and a motor generator (motor generator).

  The output torque of AC electric motor M1 is transmitted to drive wheels 50 by drive machine system 40 constituted by a speed reducer and a power split mechanism, thereby causing the electric vehicle to travel. The AC motor M1 can generate electric power by the rotational force of the drive wheels 50 transmitted via the drive machine system 40 during regenerative braking of the electric vehicle. Then, the generated power is converted into charging power for the power storage device B by the PCU 20.

  In a hybrid vehicle equipped with an engine (not shown) in addition to AC electric motor M1, a necessary vehicle driving force for the electric vehicle is generated by operating the engine and AC electric motor M1 in a coordinated manner. At this time, the power storage device B can be charged using the power generated by the rotation of the engine.

  That is, the electric vehicle refers to a vehicle equipped with an electric motor for generating vehicle driving force, and includes a hybrid vehicle that generates vehicle driving force by an engine and an electric motor, an electric vehicle not equipped with an engine, a fuel cell vehicle, and the like.

  DC voltage generation unit 10 includes a power storage device B, system relays SR1 and SR2, a smoothing capacitor C1, and a boost converter 12.

  The power storage device B provided as a DC power supply is typically configured by a rechargeable device such as a secondary battery such as a nickel metal hydride battery or a lithium ion battery, or an electric double layer capacitor. The power storage device B is provided with a monitoring sensor 11. Thereby, output voltage Vb, output current Ib, and temperature Tb of power storage device B are detected. A value detected by the monitoring sensor 11 is input to the control device 30.

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

  Boost converter 12 includes a reactor L1 and power semiconductor switching elements Q1, Q2. Power semiconductor switching elements Q 1 and Q 2 are connected in series between power line 7 and power 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 C0 is connected between the power line 7 and the power line 5.

  The smoothing capacitor C0 smoothes the DC voltage of the power line 7. The voltage sensor 13 detects the voltage across the smoothing capacitor C0, that is, the DC voltage VH on the power line 7. Hereinafter, the DC voltage VH corresponding to the DC link voltage of the inverter 14 is also referred to as “system voltage VH”. On the other hand, the DC voltage VL of the power line 6 is detected by the voltage sensor 19. When system relays SR1 and SR2 are on, DC voltage VL corresponds to the output voltage of power storage device B. The DC voltages VH and VL detected by the voltage sensors 13 and 19 are input to the control device 30.

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

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

  Boost converter 12 operates in either a non-boosting mode or a boosting mode. In the non-boost mode, boost converter 12 is controlled such that switching elements Q1 and Q2 are turned on and off in a complementary manner according to PWM control. Boost converter 12 can control the boost ratio (VH / VL) by controlling the on-period ratio (duty ratio) of switching elements Q1, Q2. Therefore, on / off of switching elements Q1, Q2 is controlled in accordance with the duty ratio calculated according to the detected values of DC voltages VL, VH and system voltage command value VH *. Thus, in the boost mode, VH *> VL is set, and boost converter 12 controls system voltage VH by on / off control of switching elements Q1 and Q2.

  In addition, by switching on and off switching element Q1 complementarily with switching element Q2, it is possible to cope with both charging and discharging of power storage device B without switching control according to the current direction of reactor L1. That is, through control of system voltage VH according to system voltage command value VH *, boost converter 12 can cope with both regeneration and power running.

  At the time of low output of AC motor M1, AC motor M1 can be controlled in a state of VH = VL (boost ratio is 1) without boosting by boost converter 12. In this case, the non-boosting mode is selected, and switching elements Q1 and Q2 are fixed on and off, respectively, so that power loss in boost converter 12 is reduced.

  When the torque command value of AC motor M1 is positive (Tqcom> 0), inverter 14 responds to switching control signals S3 to S8 from control device 30 when a DC voltage is supplied from smoothing capacitor C0. AC motor M1 is driven so as to output a positive torque by converting a DC voltage into an AC voltage by switching operation of elements Q3 to Q8. Further, when the torque command value of AC motor M1 is zero (Tqcom = 0), inverter 14 converts the DC voltage into an AC voltage by the switching operation in response to switching control signals S3 to S8, and the torque is zero. The AC motor M1 is driven so that Thus, AC electric motor M1 is driven to generate zero or positive torque designated by torque command value Tqcom.

  Further, during regenerative braking of an electric vehicle equipped with control system 100, torque command value Tqcom of AC electric motor M1 is set to be negative (Tqcom <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 the converted DC voltage (system voltage VH) is a smoothing capacitor. The voltage is supplied to the boost converter 12 via C0.

  Note that regenerative braking here refers to braking with regenerative power generation when a driver operating an 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 a current (phase current) flowing through AC electric motor M <b> 1 and outputs the detected value to control device 30. Since the sum of instantaneous values of the three-phase currents iu, iv, and iw is zero, the motor currents for two phases (for example, the V-phase current iv and the W-phase current iw) are detected as shown in FIG. You may arrange in.

  The rotation angle sensor (resolver) 25 detects the rotor rotation angle θ of the AC electric motor M 1 and sends the detected rotation angle θ to the control device 30. Control device 30 can calculate rotation speed Nmt and rotation angular speed ω of AC electric motor M1 based on rotation angle θ. Note that the rotation angle sensor 25 may be omitted by directly calculating the rotation angle θ from the motor voltage or current by the control device 30.

The control device 30 is configured by an electronic control unit (ECU), and is controlled by software processing by executing a prestored program by a CPU (Central Processing Unit) (not shown) and / or hardware processing by a dedicated electronic circuit. Control the operation of the system 100.

  As a representative function, the control device 30 includes the input torque command value Tqcom, the DC voltage VL detected by the voltage sensor 19, the system voltage VH detected by the voltage sensor 13, and the motor detected by the current sensor 24. Based on the currents iu (iu = − (iv + iw)), iv, iw, the rotation angle θ from the rotation angle sensor 25, etc., the AC motor M1 outputs torque according to the torque command value Tqcom by a control method described later. In addition, the operation of boost converter 12 and inverter 14 is controlled.

  That is, control device 30 generates switching control signals S1 and S2 of boost converter 12 in order to control DC voltage VH as described above in accordance with system voltage command value VH *. Control device 30 generates switching control signals S3 to S8 for controlling the output torque of AC electric motor M1 in accordance with torque command value Tqcom. Switching control signals S <b> 1 to S <b> 8 are input to boost converter 12 and inverter 14.

(Control mode in motor control)
Next, the AC motor control for the AC motor M1 by the inverter 14 will be described in detail.

FIG. 2 is a diagram for explaining a control mode for AC motor control.
As shown in FIG. 2, in the control system for an AC motor according to the embodiment of the present invention, three control modes are switched and used for AC motor control by an inverter.

  The sine wave PWM control is used as a general PWM control, and controls on / off of the switching element in each phase arm according to a voltage comparison between a sine wave voltage command and a carrier wave (typically, a triangular wave). . The voltage command indicates an AC voltage (phase voltage) to be output from the inverter to the AC motor M1 calculated by a control calculation for controlling the output torque of the AC motor M1 according to the torque command value.

  With the PWM control, the fundamental wave component of 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 is a sine wave within a certain period. The duty ratio is controlled.

  Hereinafter, in this specification, the ratio of the AC voltage (effective value of the line voltage) output to the AC motor M1 to the DC link voltage (system voltage VH) in the DC / AC voltage conversion by the inverter is referred to as “modulation degree”. Define. The application of the sine wave PWM control is basically limited to a state where the AC voltage amplitude (phase voltage) of each phase becomes equal to the system voltage VH. That is, in the sine wave PWM control, the modulation degree can be increased only to about 0.61 times. Note that by superimposing the 3n-order harmonic on the sinusoidal voltage command, the maximum modulation degree in the sinusoidal PWM control can be increased to 0.70.

  The overmodulation PWM control is to perform the same PWM control as the above sine wave PWM control after expanding the amplitude of an AC voltage (sine wave shape) larger than the amplitude of the carrier wave. As a result, the modulation factor can be increased to a range of 0.61 (0.7) to 0.78 by distorting the fundamental wave component. As a result, the PWM control can be applied to a part of the region where the sine wave PWM control cannot be applied.

  In the sine wave PWM control and overmodulation PWM control, the voltage command is calculated by feedback control of the motor current flowing through the AC motor M1. Hereinafter, when both sine wave PWM control and overmodulation PWM control are included, they are also simply referred to as PWM control.

  On the other hand, in the rectangular wave voltage control, the inverter outputs one pulse of the rectangular wave whose ratio between the high level period and the low level period is 1: 1 within the period corresponding to the electrical angle of 360 degrees of the electric motor. Thereby, the modulation degree is increased to 0.78. In the rectangular wave voltage control, the modulation degree is fixed at 0.78.

(Description of control configuration in each control mode)
FIG. 3 is a functional block diagram illustrating a control configuration in PWM control in the control system for an AC motor according to the first embodiment of the present invention. Each functional block for motor control described in the functional block diagram described below including FIG. 3 is realized by hardware or software processing by the control device 30.

  Referring to FIG. 3, PWM control unit 200 includes a current command generation unit 210, coordinate conversion units 220 and 250, a voltage command generation unit 240, and a PWM modulation unit 260.

  Current command generation unit 210 generates a d-axis current command value Idcom and a q-axis current command value Iqcom according to torque command value Tqcom of AC electric motor M1 according to a map or the like created in advance. As will be described later, the current phase of AC electric motor M1 can be appropriately controlled by a combination of d-axis current command value Idcom and q-axis current command value Iqcom.

  The coordinate conversion unit 220 performs the v-phase current iv and the W-phase current detected by the current sensor 24 by coordinate conversion (3 phase → 2 phase) using the rotation angle θ of the AC motor M1 detected by the rotation angle sensor 25. Based on iw, a d-axis current Id and a q-axis current Iq are calculated.

  Deviation ΔId (ΔId = Idcom−Id) relative to the command value of the d-axis current and deviation ΔIq (ΔIq = Iqcom−Iq) relative to the command value of the q-axis current are input to the voltage command generation unit 240. The voltage command generation unit 240 obtains a control deviation by performing PI (proportional integration) calculation with a predetermined gain for each of the d-axis current deviation ΔId and the q-axis current deviation ΔIq, and a d-axis voltage command value corresponding to the control deviation. Vd # and q-axis voltage command value Vq # are generated.

  The coordinate conversion unit 250 converts the d-axis voltage command value Vd # and the q-axis voltage command value Vq # into the U-phase, V-phase, W-phase by coordinate conversion (2 phase → 3 phase) using the rotation angle θ of the AC motor M1. Each phase voltage command Vu, Vv, Vw of the phase is converted.

  At this time, the above-described modulation degree Kmd is expressed by the following equation (1) when the d-axis and q-axis voltage command values Vd # and Vq # and the system voltage VH are used.

Kmd = (Vd # ² + Vq # ² ) ^1/2 / VH (1)
The PWM modulator 260 controls on / off of the upper and lower arm elements of each phase of the inverter 14 based on a comparison between a carrier wave (not shown) and an AC voltage command (which comprehensively indicates Vu, Vv, Vw). A pseudo sine wave voltage is generated for each phase of AC electric motor M1. The carrier wave is constituted by a triangular wave or a sawtooth wave having a predetermined frequency. As described above, it is possible to superimpose a 3n-order harmonic on a sinusoidal AC voltage command.

  In the pulse width modulation in the inverter 14, the amplitude of the carrier wave corresponds to the DC link voltage (system voltage VH) of the inverter 14. Note that the amplitude of the carrier voltage used in the PWM modulator 260 can be fixed by converting the amplitude of the AC voltage command for PWM modulation into one obtained by dividing the amplitude of the original phase voltage commands Vu, Vv, Vw by the system voltage VH. .

  Note that, when the sine wave PWM is selected, the overmodulation PWM is applied when the modulation degree Kmd rises to a range of 0.61 (0.7 when the 3n-order harmonic is superimposed) to 0.78. In the overmodulation PWM control, the amplitude of each phase voltage command obtained by converting the voltage command values Vd # and Vq # into two-phase to three-phase is larger than the DC link voltage (system voltage VH) of the inverter 14. On the other hand, since a voltage exceeding system voltage VH cannot be applied from inverter 14 to AC electric motor M1, depending on PWM control according to each phase voltage command signal, the original corresponding to voltage command values Vd # and Vq # is required. The degree of modulation cannot be secured.

  For this reason, in the overmodulation PWM control, a correction process for expanding the voltage amplitude (× k times, k> 1) so that the voltage application interval is increased with respect to the AC voltage command based on the voltage command values Vd # and Vq #. By doing so, it is possible to ensure the original degree of modulation by the voltage command values Vd # and Vq #. Such amplitude correction processing can be executed by adding a function in the voltage command generation unit 240 or the coordinate conversion unit 250 during overmodulation PWM control.

  When sine wave PWM control or overmodulation PWM control is applied, the inverter 14 is subjected to switching control according to the switching control signals S <b> 3 to S <b> 8 generated by the PWM control unit 200. Thereby, an AC voltage for outputting torque according to torque command value Tqcom is applied to AC electric motor M1. That is, torque control of AC motor M1 can be performed by feedback control of motor current using current command values Idcom and Iqcom that define the current phase as reference values.

  FIG. 4 is a functional block diagram illustrating a control configuration in rectangular wave voltage control in the AC motor control system according to the embodiment of the present invention.

  Referring to FIG. 4, rectangular wave voltage control unit 400 includes a power calculation unit 410, a torque calculation unit 420, a PI calculation unit 430, a rectangular wave generator 440, and a signal generation unit 450.

  The power calculation unit 410 uses the phase currents obtained from the V-phase current iv and the W-phase current iw by the current sensor 24 and the phase voltages Vu, Vv, Vw to supply power to the motor according to the following equation (2) ( An estimated value Pmt of (motor power) is calculated.

Pmt = iu · Vu + iv · Vv + iw · Vw (2)
The torque calculation unit 420 uses the motor power (estimated value) Pmt obtained by the power calculation unit 410 and the rotation angular velocity ω calculated from the rotation angle θ of the AC motor M1 detected by the rotation angle sensor 25 as follows ( 3) An estimated torque value Tqt is calculated according to the equation.

Tqt = Pmt / ω (3)
Note that a torque deviation ΔTq may be obtained based on a detection value of the torque sensor by arranging a torque sensor instead of the power calculation unit 410 and the torque calculation unit 420.

  Torque deviation ΔTq (ΔTq = Tqcom−Tq) with respect to torque command value Tqcom is input to PI calculation unit 430. PI calculation unit 430 performs PI calculation with a predetermined gain on torque deviation ΔTq to obtain a control deviation, and sets phase φv of rectangular wave voltage according to the obtained control deviation.

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

  FIG. 5 is a conceptual diagram for explaining voltage phase-torque characteristics in rectangular wave voltage control. FIG. 5 shows voltage phase-torque characteristics when the system voltage VH is changed under a constant rotational speed (constant ω).

  As understood from FIG. 5, the output torque increases as the system voltage VH increases with respect to the same voltage phase φv. Therefore, when a high torque is required, the output torque can be secured by raising the system voltage VH by the boost converter 12.

  FIG. 5 exemplifies characteristics during a power running operation (positive torque output). However, if the polarity of the voltage phase φv with respect to the q axis is reversed, the AC motor is similarly used during a regenerative operation (negative torque output). The output torque of M1 can be controlled.

  FIG. 6 is a conceptual diagram for explaining the relationship between the operating point of AC electric motor M1 and the applied control mode. The horizontal axis in FIG. 6 indicates the rotational speed of the AC motor M1, and the vertical axis in FIG. 6 indicates the output torque of the AC motor M1.

  In AC motor control system 100, sine wave PWM control, overmodulation PWM control, and rectangular wave voltage control shown in FIG. 2 are selectively applied in accordance with the state of AC motor M1. That is, even when the AC motor M1 has the same output, the modulation degree changes when the system voltage VH changes, so the applied control mode also changes.

  Referring to FIG. 6, in control system 100, when boost converter 12 is operated in the non-boosting mode, output voltage of power storage device B (that is, DC voltage VL) becomes system voltage VH as it is (VH = VL). When the output of AC motor M1 is low, AC motor M1 can be driven by applying one of the above three control methods in the non-boosting mode.

  The non-boosting maximum torque line LN1 shown in FIG. 6 is a set of maximum output torques that the AC motor M1 can output at each rotational speed when the boost converter 12 is in the non-boosting mode. The substantially trapezoidal region inside the non-boosting maximum torque line LN1 is distinguished into a sine wave PWM control region A1, an overmodulation PWM control region A2, and a rectangular wave voltage control region A3 according to the modulation degree described above. become.

  The boundary line LN2 between the sine wave PWM control region A1 and the overmodulation PWM control region A2 has a modulation degree of 0.61 (or 0) at which the modulation degree is the maximum value in the general sine wave PWM control at each rotational speed. .7) shows the set of output torques.

  Further, the boundary line LN3 between the overmodulation PWM control region A2 and the rectangular wave voltage control region A3 has an output torque when the degree of modulation becomes 0.78 that is the degree of modulation in the rectangular wave voltage control at each rotational speed. A set of

  When the boost converter 12 boosts the output voltage of the power storage device B to the upper limit voltage and sets the system voltage VH to the maximum value VHmax (for example, 650 V), the boosting maximum torque line LN4 indicated by a broken line in FIG. This is a set of maximum output torques that can be output by AC electric motor M1 at the rotational speed.

  As described above, in the non-boosting mode, the switching loss in boost converter 12 is reduced, so that the efficiency of the entire system is improved. For this reason, it is advantageous in terms of efficiency to expand application of the non-boosting mode. On the other hand, when the operating point (rotational speed and torque) of AC electric motor M1 is located outside of non-boosting maximum torque line LN1, if boost converter 12 does not operate in the boost mode, the torque command value is followed. Torque cannot be generated.

  Next, the change in the current phase of the AC motor when the output of the AC motor M1 changes with the switching of the control mode as described above will be described with reference to FIG.

  FIG. 7 is a diagram showing a change in the current phase of AC electric motor M1 accompanied by switching of the control mode. FIG. 7 exemplifies a locus of change in current phase when the output torque is gradually increased with respect to the same DC voltage VH. The horizontal axis in FIG. 7 indicates the d-axis current Id, and the vertical axis in FIG. 7 indicates the q-axis current Iq. The current phase φi is defined by the following equation (4).

  In the sine wave PWM control and the overmodulation PWM control, the current phase φi is determined to be on the optimum current phase line 42. The optimum current phase line 42 is drawn on the Id-Iq plane as a set of current phases where the output torque is maximum for the same amplitude of the motor current. That is, the optimum current phase line 42 corresponds to a set of current phase points to which the loss in the AC motor M1 on the equal torque line on the Id-Iq plane is a reference. The optimum current phase line 42 can be obtained in advance through experiments or simulations.

  The d-axis and q-axis current command values (Idcom, Iqcom) in the current feedback control in PWM control are the d-axis and q corresponding to the intersection of the equal torque line corresponding to the torque command value Tqcom and the optimum current phase line 42. Set to the current value of the axis. For example, a map for PWM control that determines the combination of the current command values Idcom and Iqcom on the optimum current phase line 42 corresponding to each torque command value may be created in advance and stored in the control device 30. it can.

  In FIG. 7, the trajectory in which the tip position (current phase) of the current vector resulting from the combination of Id and Iq starting from the zero point position changes according to the increase in output torque is indicated by an arrow. As the output torque increases, the current magnitude (corresponding to the magnitude of the current vector on the Id-Iq plane) increases. In the sine wave PWM control and overmodulation PWM control, the current phase is controlled on the optimum current phase line 42 by setting the current command values Idcom and Iqcom. When the torque command value further increases and the modulation degree reaches 0.78, rectangular wave voltage control is applied.

  In rectangular wave voltage control, in order to perform field weakening control, the absolute value of the d-axis current Id, which is a field current, increases as the output torque is increased by increasing the voltage phase φv. As a result, the tip position (current phase) of the current vector moves away from the optimum current phase line 42 to the left side (advance side) in the figure, and the loss of the AC motor M1 increases. Thus, in the rectangular wave voltage control, the inverter 14 cannot directly control the current phase of the AC motor M1.

  On the contrary, when the output torque is decreased by reducing the voltage phase φv under the same system voltage VH, the current phase φi changes to the right side (retard angle side) in the figure. When the current phase φi is retarded from the mode switching line 43 during the rectangular wave voltage control, a transition from the rectangular wave voltage control to the PWM control is instructed. For example, the mode switching line 43 is drawn as a set of current phase points where φi = φth (reference value). In other words, when current phase φi becomes smaller than φth (reference value), a transition from rectangular wave voltage control to PWM control is instructed.

  FIG. 8 shows a transition diagram for explaining mode switching between PWM control and rectangular wave voltage control.

  Referring to FIG. 8, when applying PWM control (sine wave PWM or overmodulation PWM control), the degree of modulation is calculated according to the amplitude of the AC voltage obtained by the current feedback control shown in FIG. For example, the modulation degree Kmd can be calculated according to the above equation (1).

  When applying the PWM control, if the modulation degree Kmd becomes larger than 0.78, a transition to the rectangular wave voltage control mode is instructed.

  In the rectangular wave voltage control, the current phase φi changes to the right side (retard side) in FIG. 7 as the output torque decreases. Then, when the current phase φi becomes smaller than the reference value φth, that is, when the current phase φi enters the phase region on the retard side of the mode switching line 43 shown in FIG. 7, the transition to the PWM control mode is instructed.

  When the system voltage VH is changed with respect to the same output of the AC motor M1, the modulation degree in the PWM control changes. In the rectangular wave voltage control, the current phase φi changes accompanying the change of the voltage phase φv for obtaining the output. Therefore, the loss in the control system changes according to the system voltage VH.

  FIG. 9 is a conceptual diagram for explaining the behavior of the control system according to the change of the system voltage VH through the three control modes. FIG. 9 shows the behavior when the system voltage VH is changed and the output (rotational speed × torque) of the AC motor M1 is the same.

  Referring to FIG. 9, the degree of modulation increases as system voltage VH is decreased for the same output. Sine wave PWM control, overmodulation PWM control, and rectangular wave voltage control are sequentially applied in accordance with the increase in the degree of modulation. In the rectangular wave voltage control, the modulation degree is constant at 0.78.

  When the PWM control (sine wave PWM control and overmodulation PWM control) is applied, the current phase is controlled along the optimum current phase line 42 (FIG. 7) along with the current feedback control. When the system voltage VH is lowered, the motor current necessary for obtaining the same output increases, so that the current phase gradually changes to the advance side along the optimum current phase line 42. In the rectangular wave voltage control, when the system voltage VH is lowered, the voltage phase for outputting the same torque is increased. Accordingly, as shown in FIG. 7, the current phase changes to the advance side.

  The motor loss is suppressed when the PWM control is applied because the current phase is controlled along the optimum current phase line 42. On the other hand, when rectangular wave voltage control is applied, motor loss increases due to the influence of field weakening current. When the rectangular wave voltage control is applied, if the system voltage VH decreases with respect to the same output, the motor loss increases due to the increase of the field weakening current.

  On the other hand, since the inverter loss depends on the number of times of switching in the inverter 14, it is suppressed when the rectangular wave voltage control is applied, but increases when the PWM control is applied. When the system voltage VH rises, the loss power per switching increases, so that the inverter loss increases.

  From the characteristics of the motor loss and the inverter loss, it is understood that the sum of the motor loss and the inverter loss in the control system is minimized at the operating point 44 to which the rectangular wave voltage control is applied. As shown in FIG. 7, the current phase of the operating point 44 is located in the vicinity (retard side) of the optimum current phase line 42.

(Transition from non-boosting mode to boosting mode)
Here, consider the transition from the non-boosting mode to the boosting mode in boost converter 12. As described above, the loss in boost converter 12 is significantly reduced by applying the non-boost mode.

  However, when the rectangular wave voltage control is applied in the non-boosting mode, if the voltage phase increases in accordance with the increase in the output of AC motor M1, the loss in AC motor M1 increases due to the change in current phase φi. For this reason, even in the region inside the non-boosting maximum torque line LN1 shown in FIG. 7, the loss of the AC motor M1 increases as the current phase φi advances, so that the efficiency of the entire system decreases. There is. In such a region, operating the boost converter 12 in the boost mode to increase the system voltage VH suppresses the loss in the entire system rather than maintaining the non-boost mode in which the loss in the boost converter 12 is small. can do. Therefore, in the non-boost mode, when the current phase φi exceeds the boost request line 41 (FIG. 7) set in advance on the advance side with respect to the optimum current phase line 42, the transition to the boost mode is requested. Is done.

  Thus, from the aspect of the efficiency of the control system, that is, the energy efficiency (fuel consumption) of the electric vehicle, the non-boosting mode and the rectangular wave voltage control are directed so as to direct the operation at the operating point 44 in FIGS. Is preferably applied actively. Therefore, in the non-boosting mode, the sine wave PWM control, the overmodulation PWM control, and the rectangular wave voltage control are sequentially applied according to the increase in the output of the AC motor M1, and the current phase in the rectangular wave voltage control is the boost request line 41. In response to exceeding (FIG. 7), it is necessary to determine the transition from the non-boosting mode to the boosting mode.

  On the other hand, from the aspect of improving the torque controllability of AC electric motor M1, sine wave PWM control is preferably applied. Therefore, typically, in a scene where high torque controllability is required, such as when the torque of AC electric motor M1 is increased (for example, when accelerating in response to an accelerator opening increase in an electric vehicle), sinusoidal PWM Control needs to be applied continuously. In this case, it is necessary to increase the system voltage VH according to the increase in the output of the AC motor M1 so that the modulation degree does not exceed 0.61 (or 0.7). Therefore, in a scene where PWM control is required, it is necessary to determine the transition from the non-boosting mode to the boosting mode according to the degree of modulation in the non-boosting mode.

  As described above, in AC motor control system 100 according to the present embodiment, setting of system voltage VH, including selection of boost / non-boost in boost converter 12, determines the overall system efficiency and torque controllability of AC motor M1. Affects. In the first embodiment, attention is paid to the transition from the non-boosting mode to the boosting mode. In particular, a problem that occurs in the output of power storage device B when boosting operation of boosting converter 12 starts will be focused.

  FIG. 10 is an operation waveform diagram for explaining a problem that occurs at the time of transition from the non-boosting mode to the boosting mode.

FIG. 10 shows an operation in a scene where an output request (output torque) to AC electric motor M1 increases as the accelerator opening degree Accr in the electric vehicle increases. In this scene, the motor voltage Vr indicating the AC voltage (line voltage effective value) output from the inverter 14 to the AC motor M1 rises to output a torque according to the torque command value Tqcom. The motor voltage Vr can be expressed as Vr = (Vd ² + Vq ² ) ^1/2 using the d-axis voltage Vd and the q-axis voltage Vq.

  Prior to time t1, the boosting flag Fvup is off because of the non-boosting mode. Therefore, system voltage VH is equivalent to DC voltage VL corresponding to the output voltage of power storage device B (VH = VL).

  As the motor voltage Vr increases, the output current of the power storage device B increases. Thereby, in power storage device B, the voltage drop due to the internal resistance increases. In the non-boosting mode, since VH = VL, the DC voltages VL and VH decrease as the motor voltage Vr increases. As the motor voltage Vr increases, the degree of modulation Kmd (Kmd = Vr / VH) also increases. In FIG. 10, VH and VL are represented on the same scale, but the scale of Vr is different from VH and VL. That is, the voltage change amount of Vr in FIG. 10 is considerably larger than the voltage change amounts of VH and VL.

  Usually, at the time of acceleration, it is necessary from the aspect of drivability to improve the torque controllability of AC electric motor M1, and therefore torque control by sine wave PWM control is preferable. Therefore, FIG. 10 shows an example of transition from the non-boosting mode to the boosting mode according to the modulation degree Kmd in order to continuously apply the sine wave PWM control.

  When the modulation degree Kmd becomes higher than the boost threshold tKmd at time t1, the boost flag Fvup is turned on. Along with this, boost converter 12 starts a boost operation, and system voltage VH increases. At this time, the power storage device B further supplies boosted power Pc for increasing the voltage of the power line 7 to which the smoothing capacitor C0 is connected, in addition to the output power thus far. The step-up power Pc is proportional to the product of the voltage increase amount ΔVH (ΔVH> 0) per unit time and the capacitance value C of the smoothing capacitor C0.

  For this reason, the voltage drop due to the internal resistance in power storage device B is further increased by increasing the discharge current of power storage device B during boosting. As a result, the output voltage (DC voltage VL) of power storage device B is significantly reduced.

  As shown in FIG. 10, when the boost operation is started at a timing when the DC voltage VL is reduced to the vicinity of the lower limit voltage VLmin of the power storage device B and there is no output margin, the DC voltage VL <VLmin until the moment VL <VLmin. VL, that is, the output voltage of the power storage device B may be reduced. When such a phenomenon occurs, there is a concern that the power storage device B is overdischarged and deteriorates. It is assumed that lower limit voltage VLmin corresponds to a management lower limit voltage at the time of discharging, which is predetermined as a specification of power storage device B.

  After the time t1, the accelerator opening degree Accr further increases, but since the output power upper limit of the power storage device B has been reached, the output of the AC motor M1 does not increase any further. For this reason, the system voltage VH is also maintained constant so that the modulation degree Kmd≈tKmd is maintained. That is, in the example of FIG. 10, it is shown that there is a possibility that the voltage drop due to excessive output of the power storage device B at the start of boosting may not be able to be handled only by limiting the output power of the power storage device B. In the first embodiment, control in boosting mode / non-boosting mode of boosting converter 12 for suppressing such a voltage drop in power storage device B will be described.

  FIG. 11 is a functional block diagram illustrating control calibration for selection of the boosting mode / non-boosting mode in the control system for an AC motor according to the first embodiment of the present invention.

  Referring to FIG. 11, boost mode control unit 500 includes first boost determination unit 510, second boost determination unit 520, arbitration processing unit 530, minimum voltage setting unit 540, and PWM control request unit 560. Have.

  The PWM control request unit 560 turns on and off a PWM request flag Rpwm for requesting application of sine wave PWM control with high torque controllability according to the vehicle state of the electric vehicle. For example, the PWM request flag Rpwm is turned on while the acceleration request by the driver exceeds a certain level based on the accelerator opening degree Accr. Alternatively, when the driving mode can be designated by the driver, it is preferable to lower the constant level for turning on the PWM request flag Rpwm when selecting a sports mode in which acceleration response is important.

  First boost determination unit 510 turns on / off boost request flag Rvup1 based on the degree of modulation in inverter 14 or the current phase of AC electric motor M1. The boost request flag Rvup1 is set to a logic high level (hereinafter referred to as “H level”) when the first boost determination unit 510 requests boost from the boost converter 12, and otherwise to a logic low level (hereinafter referred to as “ "L level").

  Second boost determination unit 520 turns on / off boost request flag Rvup2 based on DC voltage VL corresponding to the output voltage of power storage device B. Boost request flag Rvup2 is set to H level when second boost determination unit 520 requests boost converter 12 to boost, and is set to L level otherwise.

  Arbitration processing unit 530 sets boosting flag Fvup for defining the non-boosting mode / boosting mode of boosting converter 12 based on boosting request flags Rvup1 and Rvup2. When boosting flag Fvup is at a low level, boosting converter 12 operates in a non-boosting mode in which switching element Q1 is fixed on and switching element Q2 is fixed off. In contrast, when boost flag Fvup is turned on, boost converter 12 operates in the boost mode and controls switching elements Q1 and Q2 to control system voltage VH according to system voltage command value VH *. To do.

  Minimum voltage setting unit 540 sets minimum voltage VHmin * of system voltage command value VH * in the boost mode according to boost request flag Rvup2 from second boost determination unit 520.

  FIG. 12 is a flowchart for explaining the control processing operation by the first boost determination unit, more specifically, on / off setting of the boost request flag Rvup1. The control device 30 executes the control process according to the flowchart process shown in FIG.

  Referring to FIG. 12, first boost determination unit 510 (control device 30) determines whether boost flag Fvup is currently turned off in step S100. When boosting flag Fvup is off, that is, when non-boosting mode is selected (when YES is determined in S100), first boost determination unit 510 proceeds to step S110 to determine whether PWM request flag Rpwm is turned on. Determine.

  When the sine wave PWM control is requested in the non-boosting mode (when YES is determined in S110), the first boost determination unit 510 advances the process to step S120 to determine the current modulation degree Kmd and the boost threshold tKmd. Based on the comparison, the boost request flag Rvup1 is set. Specifically, when modulation degree Kmd exceeds boost threshold tKmd (when YES is determined in S120), first boost determination unit 510 proceeds to step S170 and turns on boost request flag Rvup1. Note that, when the transition from the non-boosting mode to the boosting mode is determined based on the modulation degree Kmd, since the PWM request flag Rpwm is turned on, it is required to continuously apply the sine wave PWM control. Therefore, the boost threshold tKmd is set to a value equal to or less than the maximum modulation degree 0.61 (or 0.70) in the sine wave PWM control. For example, the boost threshold tKmd is set to about 0.5 to 0.6.

  On the other hand, when the degree of modulation Kmd has not reached the boost threshold value tKmd (NO determination in S120), the first boost determination unit 510 advances the process to step S180 and sets the boost request flag Rvup1 to the current value. maintain. Therefore, in the non-boosting mode, the boost request flag Rvup1 is maintained off.

  When the PWM request flag Rpwm is turned off (NO determination in S110), the first boost determination unit 510 actively performs the non-boost mode and the rectangular wave voltage control as described with reference to FIGS. In step S130, the boost request flag Rvup1 is set based on the current phase φi. In step S130, the current current phase φi of AC electric motor M1 is compared with a boost threshold tφvup indicating the current phase corresponding to boost request line 41 shown in FIG.

  As described with reference to FIG. 7, when the sine wave PWM control and the overmodulation PWM control are applied, the current phase φi changes on the optimum current phase line 42, so that φi ≦ tφvup is maintained. Then, after shifting from PWM control to rectangular wave voltage control as the degree of modulation increases, if the current phase φi changes to the retard side due to further increase in the output of the AC motor M1, φi> tφvup and step S130 is determined as YES.

  At this time, first boost determination section 510 advances the process to step S170 and turns on boost request flag Rvup1. On the other hand, when φi ≦ tφvup, that is, when current phase φi does not exceed boost request line 41 (NO determination in S130), first boost determination unit 510 proceeds to step S180 to perform boost The request flag Rvup1 is maintained at the current value. Therefore, in the non-boosting mode, the boost request flag Rvup1 is maintained off.

  In step S150, first boost determination unit 510 sets a non-boost threshold tKmd # related to the modulation degree in step S150 according to on / off of PWM request flag Rpwm.

  Specifically, the first boost determination unit 510 sets the non-boosting threshold tKmd # = K1 when the PWM request flag Rpwm is on, while setting the non-boosting threshold tKmd # = K2 when the PWM request flag Rpwm is off. It is set (K2> K1). When the PWM request flag Rpwm is on, the non-boosting threshold value K1 is set lower than the boosting threshold value tKmd in step S120. As described above, by providing hysteresis between the boost threshold tKmd and the non-boost threshold tKmd # when the sine wave PWM control is requested, it is possible to prevent frequent switching between the boost mode and the non-boost mode in a short time. .

  Further, in step S160, first boost determination unit 510 compares current modulation degree Kmd in the boost mode with non-boosting threshold tKmd # set in step S150. When the degree of modulation Kmd decreases below the non-boosting threshold tKmd # in the boosting mode (when YES is determined in S160), the first boost determining unit 510 proceeds to step S190 and turns off the boost request flag Rvup1.

  On the other hand, when the modulation degree Kmd is equal to or higher than the non-boosting threshold tKmd # in the boosting mode (when NO is determined in S160), the first boost determination unit 510 advances the process to step S180 to increase the boost request flag Keep Rvup1 at the current value. Therefore, in the boost mode, the boost request flag Rvup1 is kept on.

  Thus, the first boost determination unit 510 selects the non-boost mode / boost mode based on the degree of modulation in the inverter 14 and / or the current phase of the AC motor M1 in the torque control of the AC motor M1. Second boost determination unit 520 responds to the output of power storage device B with respect to the selection of the basic boost mode / non-boost mode based on the state of AC electric motor M1 and inverter 14 by first boost determination unit 510. It has a function for making corrections. That is, in the first embodiment, the first boost determination unit 510 corresponds to an example of “first control unit” in the present invention, and the second boost determination unit 520 corresponds to “second control unit” in the present invention. Corresponds to an embodiment of "."

  FIG. 13 is a flowchart for explaining the control processing operation by the second boost determination unit 520. The control device 30 executes a control process according to the flowchart process illustrated in FIG. 13, thereby realizing the function of the second boost determination unit 520.

  Referring to FIG. 13, second boost determination section 520 (control device 30) determines whether boost request flag Rvup2 is currently turned on in step S200. When boost request flag Rvup2 is off (NO determination in S200), second boost determination unit 520 advances the process to step S210 to set DC voltage VL corresponding to the output voltage of power storage device B as threshold voltage tVL1. Compare. On the other hand, when boosting flag Fvup is on, that is, when boosting mode is selected (YES determination in S200), second boosting determination unit 520 proceeds to step S220 and corresponds to the output voltage of power storage device B. The DC voltage VL to be compared is compared with the threshold voltage tVL2.

  When boost request flag Rvup2 is off, second boost determination unit 520 proceeds to step S250 and turns on boost request flag Rvup2 when VL <tVL1 (YES in S210). On the other hand, when VL ≧ tVL1 in the non-boosting mode (NO in S210), second boosting determination unit 520 advances the process to step S240 and maintains boosting request flag Rvup2 at the current value.

  On the other hand, when boost request flag Rvup2 is on, second boost determination unit 520 proceeds to step S230 and turns off boost request flag Rvup2 when VL> tVL2 (YES in S220). . On the other hand, when VL ≦ tVL2 in the non-boosting mode (NO determination in S220), second boosting determination unit 520 advances the process to step S240 and maintains boosting request flag Rvup2 at the current value.

  As described above, the second boost determination unit 520 turns on the boost request flag Rvup2 when the DC voltage VL, that is, the output voltage of the power storage device B is lower than the threshold voltage tVL1. The boost request flag Rvup2 once boosted is turned off when the DC voltage VL (the output voltage of the power storage device B) becomes higher than the threshold voltage tVL2. The threshold voltage tVL1 is set higher than the lower limit voltage VLmin shown in FIG. The threshold voltage tVL2 for turning off the boost request flag Rvup2 is set higher than the threshold voltage tVL1.

  FIG. 14 is a flowchart for explaining the control processing operation by the arbitration processing unit 530. The function of the arbitration processing unit 530 is realized by the control device 30 executing a control process according to the flowchart process shown in FIG.

  Referring to FIG. 14, arbitration processing unit 530 (control device 30) determines whether boost request flag Rvup1 is turned on in step S300. When boost request flag Rvup1 is not turned on (when NO is determined in S300), arbitration processing unit 530 determines in step S310 whether boost request flag Rvup2 is turned on.

  When at least one of the boost request flags Rvup1 and Rvup2 is on, one of steps S300 and S310 is determined as YES. At this time, the arbitration processing unit 530 proceeds with the process to step S340 and turns on the boost flag Fvup. Thereby, boost converter 12 is controlled to operate in the boost mode.

  When both boost request flags Rvup1 and Rvup2 are turned off, arbitration processing unit 530 proceeds to step S320 and compares system voltage VH with a determination value (VL + Vβ).

  Arbitration processing unit 530 turns off boost flag Fvup in step S330 when VH> (VL + Vβ) and the voltage difference between DC voltages VH and VL is smaller than Vβ (when YES is determined in S320). . Thereby, boost converter 12 is controlled to operate in the non-boosting mode.

  On the other hand, when the voltage difference between VH and VL is equal to or larger than Vβ (when NO is determined in S320), the arbitration processing unit 530 performs step-up by step S340 even if both of Rvup2 of the boost request flag Rvup1 are turned off. Turn on the flag Fvup. In the non-boosting mode, the boost converter 12 is in a state of VH = VL. Therefore, when the boosting mode is started when the voltage difference between VH and VL is large, the system voltage VH may change rapidly. For this reason, even when both of the boost request flags Rvup1 and Rvup2 are turned off, the voltage difference in the DC voltage VH and VL is reduced after the voltage difference in the boost mode to shift to the non-boost mode. A sudden change in VH can be prevented.

  FIG. 15 is a flowchart for explaining the control processing operation by the minimum voltage setting unit 540. The function of the minimum voltage setting unit 540 is realized by the control device 30 executing a control process according to the flowchart process shown in FIG.

  Referring to FIG. 15, lowest voltage setting unit 540 (control device 30) determines whether or not boost request flag Rvup2 is turned on in step S350. When the boost request flag Rvup2 is off, that is, when the boost request is not issued in response to the decrease in the output voltage of the power storage device B (NO determination in S350), minimum voltage setting unit 540 performs step S370. The minimum voltage VHmin * = VL of the system voltage command value in the boost mode is set.

  Thereby, system voltage command value VH * of boost converter 12 is controlled within a range of VL ≦ VH * ≦ VHmax. VHmax is a control upper limit value of system voltage VH and is, for example, about 650 V as described above.

  In contrast, minimum voltage setting unit 540 is turned on when boost request flag Rvup2 is on, that is, when a boost request is issued in response to a decrease in the output voltage of power storage device B (YES in S350). In step S360, the minimum voltage VHmin * = VL + Vα of the system voltage command value in the boost mode is set. Thus, system voltage command value VH * is set so that system voltage VH is forcibly increased from the voltage value (corresponding to DC voltage VL) in non-boosting mode in the boosting mode.

  FIG. 16 is an operation waveform diagram illustrating a control operation when the selection of the boost mode / boost mode according to the first embodiment is applied. FIG. 16 also shows the behavior when the output of the AC motor M1, that is, the motor voltage Vr, increases with the change in the accelerator opening degree Accr similar to FIG.

  Referring to FIG. 16, before time ta, boosting flag Fvup is turned off and boost converter 12 operates in the non-boosting mode, similarly to time t1 in FIG. For this reason, the DC voltages VH and VL (VH = VL) gradually decrease as the output of the AC motor M1 increases, that is, as the motor voltage Vr increases.

  In the control according to the first embodiment, step S210 in FIG. 13 is determined to be YES in response to the DC voltage VL dropping to the predetermined threshold voltage tVL1 at time ta earlier than time t1 in FIG. Boost request flag Rvup2 is turned on. At this time, since Kmd <tKmd, the boost request flag Rvup1 by the first boost determination unit 510 is turned off.

  Arbitration processing unit 530 sets boost flag Fvup in response to ON of boost request flag Rvup2 corresponding to the output state of power storage device B, while boost request flag Rvup1 based on the state of AC motor M1 and inverter 14 is turned off. Turn on. Thereby, boost converter 12 starts operation in the boost mode. Furthermore, by setting the minimum voltage VHmin * set by the minimum voltage setting unit 540 to VL + Vβ, the DC voltage VH is boosted from the voltage up to time ta after time ta.

  As a result, immediately after time ta, in addition to the power supplied to AC motor M1, power for boosting system voltage VH is output from power storage device B. Therefore, DC voltage VL corresponding to the output voltage of power storage device B is output. Decreases. However, as shown in FIG. 10, by setting threshold voltage tVL1 to have an appropriate margin with respect to lower limit voltage VLmin, the output voltage of power storage device B is reduced due to the voltage drop that occurs when boost converter 12 starts boosting. A drop to the lower limit voltage VLmin can be prevented. At least the voltage difference (tVL1-VLmin) of the threshold voltage tVL1 with respect to the lower limit voltage VLmin needs to be set so as to ensure the boost power for raising the system voltage VH to VHmax. Furthermore, it is preferable to set the voltage difference (tVL1−VLmin) so that the maximum torque output of AC motor M1 can be handled based on the amount of voltage drop that occurs in power storage device B when AC motor M1 has the maximum torque.

  In other words, in Embodiment 1, when the voltage difference up to the lower limit voltage VLmin of the output voltage of power storage device B is regarded as the output margin of power storage device B, the output margin is lower than the predetermined value (tVL1-VLmin). Instructed to forcibly shift to the boost mode.

  Even after time ta, the motor voltage Vr rises, whereby the modulation degree Kmd further rises. Then, at time tb, when the degree of modulation Kmd reaches the boost threshold tKmd, the boost request flag Rvup1 is also turned on. Thereby, the boost flag Fvup is turned on even after time tb. As in the example of FIG. 10, after time tb, accelerator opening degree Accr further increases, but since the upper limit of output power of power storage device B has been reached, the output of AC electric motor M1 does not increase any further. For this reason, the system voltage VH is also maintained constant so that the modulation degree Kmd≈tKmd is maintained.

  Thus, the control system for the AC motor according to the first embodiment is basically a system that selects the non-boosting mode / boost mode based on the state (modulation degree, current phase) of AC motor M1 and inverter 14. Under the setting of the voltage, the system voltage is forced by shifting the boost converter 12 to the boost mode according to the output margin of the power storage device B, in particular, the margin with respect to the lower limit voltage VLmin for the output voltage of the power storage device B. Can be raised. Specifically, by shifting to the boost mode while the output voltage of the power storage device B has a margin with respect to the lower limit voltage VLmin, the power storage is performed at the time of transition from the non-boost mode to the boost mode as shown in FIG. It can prevent that the output voltage of the apparatus B falls to the lower limit voltage VLmin.

  As a result, in the transition from the non-boosting mode to the boosting mode, the DC link voltage (system voltage) of the inverter 14 is prevented so that the load of the power storage device B does not become excessive and the output voltage falls below the lower limit voltage. VH) can be set appropriately.

[Embodiment 2]
In the first embodiment, the control of system voltage VH for preventing the load on power storage device B from becoming excessive when shifting from the non-boosting mode to the boosting mode has been described. In the second embodiment, control of system voltage VH for preventing the load on power storage device B from becoming excessive during the boost mode will be described. In the second embodiment, setting of system voltage command value VH * in the boost mode in the control system according to the first embodiment is shown. That is, the detailed description of the common parts with the first embodiment such as the selective application of the system configuration (FIG. 1) and the control mode (FIG. 2) will not be repeated.

  FIG. 17 is a functional block diagram for illustrating a basic configuration of a system voltage command value setting unit for setting system voltage command value VH * in the boost mode. System voltage command value setting unit 600 # shown in FIG. 17 is shown as a comparative example of system voltage command value setting unit 600 (FIG. 20) used in the control system for an AC motor according to the second embodiment of the present invention.

  Referring to FIG. 17, system voltage command value setting unit 600 # includes a modulation factor calculation unit 610, a target modulation factor setting unit 620, a base command value setting unit 630, a modulation factor feedback control unit 650, and a calculation unit. 660 and an arbitration processing unit 670.

  Based on the current system voltage VH (or system voltage command value VH *) and the motor voltage Vr (or the d-axis voltage and the q-axis voltage in PWM control), the modulation degree calculation unit 610 calculates the current modulation degree Kmd. Is calculated.

  Target modulation degree setting unit 620 sets modulation degree target value Kmd * based on the vehicle state of the electric vehicle. For example, the vehicle state includes a PWM request flag Rpwm. When the PWM request flag Rpwm is turned on in response to an accelerator operation by the driver, the modulation degree target value Kmd * is a value that can be handled by sine wave PWM control, for example, about 0.5 to 0.6. Set to On the other hand, when the PWM request flag Rpwm is turned off, the modulation degree target value Kmd * is set to about 0.78 in order to improve energy efficiency.

  Further, when the driving mode MD can be designated by the driver, the vehicle state can include the driving mode MD. For example, when a sports mode that emphasizes acceleration responsiveness is selected, sinusoidal PWM control is preferably applied in order to improve torque controllability. Therefore, the modulation degree target value Kmd * is set in the same manner as when the PWM request flag Rpwm is on. can do. Alternatively, when the economy mode in which fuel efficiency (energy efficiency) is emphasized is selected, the modulation degree target value Kmd * is set in order to direct the operation at the operating point 44 (FIG. 9) for suppressing the loss of the entire control system 100. Is set to about 0.78. Further, modulation degree target value Kmd * may be changed in accordance with torque command value Tqcom and / or rotational speed Nmt of AC electric motor M1. That is, the vehicle state may include a torque command value Tqcom and / or a rotational speed Nmt.

  The base command value setting unit 630 includes a Vr * map 632 and a calculation unit 635. Vr * map 632 sets base value Vr * of motor voltage Vr according to the map shown in FIG. 18 based on torque command value Tqcom and rotational speed Nmt of AC electric motor M1.

FIG. 18 is a conceptual diagram showing a configuration example of the Vr * map shown in FIG.
Referring to FIG. 18, in the Vr * map, the horizontal axis represents motor rotation speed Nmt, and the vertical axis represents torque command value Tqcom. In the example of FIG. 18, the operating point in the map is partitioned by four lines 45 to 48 corresponding to the system voltages VH = V1 to V4. The line 49 located on the outermost side in the drawing is a set of operating points corresponding to the maximum voltage VHmax (for example, 650 V) of the system voltage VH.

  The substantially fan-shaped region RB defined by the line 45 at VH = V1 is substantially an operation region in which the AC motor M1 can be driven with the boost converter 12 in the non-boosting mode without boosting the output voltage of the power storage device B. Correspond.

  More specifically, lines are further provided between the lines 45 to 49 for each predetermined voltage width (for example, 20 V). In the tVH map, the base value Vr * of the motor voltage Vr can be set according to the voltage value corresponding to the line close to the operating point specified by the torque command value Tqcom and the rotational speed Nmt.

  Referring again to FIG. 17, operation unit 635 divides base value Vr * obtained by Vr * map 632 by modulation degree target value Kmd * by target modulation degree setting unit 620 to obtain a system voltage command value. The base value VHr is set (VHr = Vr * / KMd *). Thus, base command value setting unit 630 sets base value VHr of the system voltage command value based on the operating state (torque and rotational speed) of AC electric motor M1 and modulation degree target value Kmd *.

  The modulation degree feedback control unit 650 includes a deviation calculation unit 652 and a feedback calculation unit 355.

  The deviation calculation unit 652 calculates a deviation ΔKmd between the current modulation degree Kmd calculated by the modulation degree calculation unit 610 and the modulation degree target value Kmd *. Feedback calculation unit 655 calculates correction value ΔVH * of the system voltage command value in accordance with deviation ΔKmd obtained by deviation calculation unit 652. For example, the correction value ΔVH * is obtained by PI (proportional integration) calculation with respect to the deviation ΔKmd. When deviation ΔKmd> 0 (Kmd> Kmd *), correction value ΔVH * is set to increase system voltage VH in order to decrease modulation degree Kmd. On the other hand, when the deviation ΔKmd <0 (Kmd <Kmd *), the correction value ΔVH * is set so as to decrease the system voltage VH in order to increase the modulation degree Kmd.

  Arithmetic unit 660 calculates voltage command value VHr * according to base value VHr by base command value setting unit 630 and correction value ΔVH * by modulation degree feedback control unit 650. Arbitration processing unit 670 sets the maximum value of voltage command value VHr * calculated by calculation unit 660 and minimum voltage VHmin * as final system voltage command value VH *.

  System voltage command value setting unit 600 # according to the comparative example uses system voltage based on the operating state (torque and rotational speed) of AC electric motor M1 so as to control modulation degree Kmd in inverter 14 to modulation degree target value Kmd *. Command value VH * is determined. That is, system voltage command value setting unit 600 # is configured to set system voltage command value VH * based on the states of inverter 14 and AC electric motor M1. Since system voltage command value setting unit 600 # is configured to variably control the modulation degree, it is used when applying PWM control (sine wave PWM control and overmodulation PWM control).

  FIG. 19 is a waveform diagram showing an operation example according to the comparative example when the output of the AC motor M1 is increased in the boost mode. FIG. 19 shows an operation when system voltage command value VH * is controlled in accordance with system voltage command value setting unit 600 # (comparative example) shown in FIG.

  Referring to FIG. 19, from time tx, torque command value Tqcom of AC electric motor M <b> 1 increases as accelerator opening degree Accr increases.

  On the other hand, system voltage command value setting unit 600 # controls motor voltage Vr corresponding to increase in torque command value Tqcom in order to control modulation factor Kmd corresponding to modulation factor target value Kmd * maintained at a constant value. The system voltage VH is gradually increased in response to the increase of.

  Therefore, after time tx, the power storage device B further supplies boosted power Pc for increasing the voltage of the power line 7 to which the smoothing capacitor C0 is connected, in addition to the power supplied to the AC motor M1.

  The maximum output power value Pmmax of AC motor M1 is a value according to output power upper limit value Wout of power storage device B before time tx, but decreases by the amount of boosted power Pc after time tx. Output power upper limit Wout is determined by the state of charge of power storage device B, temperature Tb, and the like in order to prevent overdischarge of power storage device B. Thereby, the marginal power ΔPm with respect to the maximum value Pmmax of the output power of the AC motor M1 decreases. It is understood that the margin power ΔPm indicates the margin of power that can be additionally output from the power storage device B in order to increase the output power of the AC motor M1. That is, the marginal power ΔPm is an aspect of the output margin of the power storage device B.

  While the output power Pm * of the AC motor M1 when outputting torque according to the torque command value Tqcom is lower than the maximum output power value Pmmax, the output torque Tq of the AC motor M1 is controlled according to the torque command value Tqcom. Can do.

  However, at time ty, output power Pm * for outputting torque command value Tqcom corresponding to further increase in accelerator opening degree Accr reaches maximum value Pmmax. For this reason, the output torque Tq also reaches its peak, and the output of the AC motor M1 is limited. That is, after time ty, the torque is limited to Pm = Pmmax, and thus it is impossible to output torque according to the driver's accelerator operation. This may impair the drivability of the electric vehicle.

  As shown in FIG. 19, when the system voltage VH is increased while the output of the AC motor M1 is increasing, the output power of the AC motor M1 may be limited due to the influence of the boost power Pc.

  FIG. 20 is a functional block diagram for illustrating a configuration of system voltage command value setting unit 600 according to the second embodiment of the present invention.

  20 is compared with FIG. 17, system voltage command value setting unit 600 according to the second embodiment is compared with system voltage command value setting unit 600 # (comparative example) shown in FIG. 700 in that it further includes 700. Since the configuration of other parts of system voltage command value setting unit 600 is the same as that of system voltage command value setting unit 600 # (FIG. 17), detailed description will not be repeated.

  System voltage increase unit 700 includes a target modulation degree correction unit 710 and a calculation unit 715. Target modulation degree correction unit 710 sets modulation degree correction value Kmdc based on margin power ΔPm indicating the output margin of power storage device B, accelerator opening degree Accr and / or torque command value Tqcom. Normally, the modulation degree correction value Kmdc is zero. The target modulation degree correction unit 710 sets the modulation degree correction value Kmdc to a positive value when detecting an increase in the output of the AC motor M1 in a scene where the surplus power ΔPm has the capacity to supply the boost power Pc due to the increase in the system voltage VH. To do.

  The calculation unit 715 corrects the modulation degree target value Kmd * by subtracting the modulation degree correction value Kmdc from the target modulation degree correction unit 710 from the modulation degree target value Kmd * from the target modulation degree setting unit 620. Therefore, when Kmdc = 0, the setting value by the target modulation factor setting unit 620 is directly used as the modulation factor target value Kmd *. On the other hand, when Kmdc> 0 is set by the target modulation degree correction unit 710, the modulation degree target value Kmd * is lowered from the original target value by the target modulation degree setting unit 620.

  Setting of system voltage command value VH * based on modulation degree target value Kmd * set in this way is equivalent to system voltage command value setting unit 600 # shown in FIG. Therefore, when the modulation degree target value Kmd * is decreased by the system voltage increase unit 700, the system voltage command value VH * increases as compared with the case where the modulation degree target value Kmd * by the target modulation degree setting unit 620 is not corrected. To be understood. That is, system voltage increase unit 700 acts to forcibly increase system voltage VH when an increase in the output of AC electric motor M1 is detected when marginal power ΔPm is secured at a predetermined level or more.

  FIG. 21 is a waveform diagram showing an operation example according to the second embodiment when the output of AC electric motor M1 is increased in the boost mode. FIG. 21 shows an operation when system voltage command value VH * is controlled in accordance with system voltage command value setting unit 600 shown in FIG.

  Referring to FIG. 21, after time tx, accelerator opening degree Accr and torque command value Tqcom rise in the same manner as in FIG. Along with this, the system voltage VH is raised in order to maintain the modulation degree target value Kmd *. As a result, in addition to the output power of AC electric motor M1, boost power Pc is supplied from power storage device B. As a result, the output power maximum value Pmmax decreases.

  At time tz1, an increase in output of AC electric motor M1 is detected in response to accelerator opening Accr exceeding threshold tAccr or torque command value Tqcom exceeding threshold tTq. At this time, on the condition that the marginal power ΔPm is larger than the predetermined value, the target modulation degree correction unit 710 shown in FIG. 20 sets the modulation degree correction value Kmdc to a positive value (Kmdc> 0). Thereby, the modulation degree target value Kmd * decreases. As shown in FIG. 21, the target modulation degree correction unit 710 preferably sets the modulation degree correction value Kmdc so that the modulation degree target value Kmd * gradually decreases. This is to prevent a sudden change in the system voltage VH.

  System voltage VH rises from time tz1 and reaches upper limit voltage VHmax at time tz2. For this reason, VH = VHmax is maintained after time tz2.

  Between times tz1 and tz2, boost power ΔPc corresponding to the power required for boosting system voltage VH to VHmax is further required. Therefore, at time tz1, it is necessary to determine whether or not the surplus power ΔPm is larger than ΔPc. Then, according to the output margin (ΔPm) of power storage device B, system voltage VH is preliminarily increased in order to cope with the increase in output of AC electric motor M1.

  After time tz2 when the boosting is completed, the boosted power Pc = 0 because the system voltage VH is constant. As a result, the output power maximum value Pmmax can be ensured as compared with the operation example shown in FIG. 19, and therefore an output for responding to the torque command value Tqcom corresponding to the further increase in the accelerator opening degree Accr. Power Pm * is continuously secured. Therefore, since the torque according to the accelerator operation of the driver can be output, the drivability of the electric vehicle is not impaired as shown in the operation example of FIG.

  Further, after the system voltage VH reaches the upper limit voltage VHmax, the actual modulation degree cannot be controlled to the modulation degree target value Kmd *, and therefore the modulation degree Kmd increases as the torque Tq increases. In this scene, the decrease of the modulation degree target value Kmd * may be stopped.

  Thus, according to the control system for an AC motor in accordance with the second embodiment, basically, under the setting of system voltage VH based on the state (degree of modulation) of inverter 14 and AC motor M1, power storage device B The system voltage can be forcibly increased according to the output margin, particularly the margin power ΔPm that can be further supplied from the power storage device B to the AC motor M1.

  As a result, by completing the boosting of the system voltage VH while there is a margin in the output power of the power storage device B, it is possible to cope with the high torque output of the AC motor M1. Therefore, the DC link voltage (system voltage VH) of the inverter 14 is set so that the load of the power storage device B is not excessive and the output power of the AC motor M1 is not insufficient in a scene where the output increase of the AC motor M1 is detected. ) Can be set appropriately.

  In the setting of system voltage command value by system voltage command value setting unit 600 according to the control of AC motor according to the second embodiment, the overlapping part with system voltage command value setting unit 600 # according to the comparative example shown in FIG. Corresponding to one embodiment of the “first control means” in the invention, the system voltage increase unit 700 added in FIG. 20 corresponds to one embodiment of the “second control means” in the present invention.

(When rectangular wave voltage control is applied)
Since system voltage command value setting unit 600 shown in FIG. 20 is based on the feedback control of the degree of modulation in inverter 14, it is used when PWM control is applied. On the other hand, since the modulation factor is fixed at 0.78 when the rectangular wave voltage control is applied, the system voltage command value VH * cannot be set by feedback control with respect to the modulation factor target value Kmd *.

  FIG. 22 is a functional block diagram for illustrating a configuration of system voltage command value setting unit 800 when the rectangular wave voltage control according to the second embodiment of the present invention is applied.

  Referring to FIG. 22, system voltage command value setting unit 800 includes target modulation degree setting unit 620, base command value setting unit 630, system voltage increasing unit 700, current phase feedback control unit 805, and calculation unit 860. And an arbitration processing unit 870.

  Even when the rectangular wave voltage control is applied, the modulation degree target value is set by the target modulation degree setting unit 620 similar to that in FIGS. Similarly to FIG. 20, the system voltage increasing unit 700 forcibly increases the system voltage VH when an increase in the output of the AC motor M1 is detected when the marginal power ΔPm is secured at a predetermined value or more. The modulation degree target value Kmd * is decreased. Therefore, even when the rectangular wave voltage control is applied, the modulation degree target value Kmd * is set in the same manner as when the PWM control is applied.

  Similarly to FIG. 20, base command value setting unit 630 sets system voltage command value base value VHr based on the operating state (torque and rotational speed) of AC electric motor M1 and modulation degree target value Kmd *.

  During application of the rectangular wave voltage control, the modulation degree is fixed to 0.78, but the modulation degree can be lowered by increasing the system voltage VH. Accordingly, even when the rectangular wave voltage control is applied, the shift from the rectangular wave voltage control to the PWM control can be promoted by setting the modulation degree target value Kmd *.

  On the other hand, during the application of the rectangular wave voltage control, the feedback control of the modulation degree as shown in FIG. 20 cannot be performed. Therefore, the current phase feedback control unit 805 uses the feedback of the current phase φi of the AC motor M1 to change the system voltage. Set command value correction value ΔVH *.

  The current phase feedback control unit 805 includes a coordinate conversion unit 810, a voltage deviation calculation map 820, and a feedback calculation unit 830.

  Similar to the coordinate conversion unit 220 in FIG. 3, the coordinate conversion unit 810 converts the v-phase current iv and the w-phase current iw detected by the current sensor 24 and the u-phase current iu (iu = − (iv + iw)), Conversion into d-axis current Id and q-axis current Iq.

  The voltage deviation calculation map 820 generates a voltage deviation ΔVH according to the current phase φi defined on the dq plane (FIG. 7) by the d-axis current Id and the q-axis current Iq.

FIG. 23 is a conceptual diagram for explaining a configuration example of the voltage deviation calculation map 820.
The target current phase line 51 is drawn as a set of current phases corresponding to the operating point 44 (FIGS. 7 and 9) on each equal torque line on the dq plane. The operating point 44 is set slightly ahead of the optimum current phase line 42. The target current phase line 51 can be set in advance based on actual machine tests and simulation results, as with the optimum current phase line 42 (FIG. 7).

  The current target current phase is indicated by the intersection 61 of the equal torque line corresponding to the current torque command value Tqcom and the target current phase line 51. Therefore, when the tip position of the current phase vector is indicated by reference numeral 61, the current current phase is on the target current phase line 51, so that the voltage deviation ΔVH = 0 is set so as to maintain the current system voltage VH. Is set.

  On the other hand, when the current current phase is located on the more advanced side than the target current phase line 51, the voltage deviation ΔVH> 0 is set so as to increase the current system voltage VH. In the advance side region, the voltage deviation ΔVH is set larger as the phase difference from the target current phase line 51 increases. FIG. 23 illustrates a phase line 52 which is a set of current phases where ΔVH = + 20V and a phase line 53 which is a set of current phases where ΔVH = + 40V.

  As shown in FIG. 23, when the tip position of the current phase vector is indicated by reference numeral 62, the current current phase is on the phase line 53, so that the voltage deviation ΔVH = + 40V is calculated from the voltage deviation calculation map 820. Is done.

  When the current current phase is located on the retard side with respect to the target current phase line 51, the voltage deviation ΔVH <0 is set so as to decrease the current system voltage VH. Even in the retarded region, the absolute value (| ΔVH |) of the voltage deviation is set to be larger as the phase difference from the target current phase line 51 becomes larger. FIG. 11 illustrates a phase line 54 which is a set of current phases where ΔVH = −20V and a phase line 55 which is a set of current phases where ΔVH = −40V.

  Depending on the current phase defined by the d-axis current Id and the q-axis current Iq by subdividing these phase lines or using linear interpolation together, the voltage deviation calculation map 820 includes the d-axis currents Id and q. Based on the shaft current Iq, the voltage deviation ΔVH can be calculated.

  Referring to FIG. 22 again, feedback calculation unit 830 calculates system voltage command value correction value ΔVH * by a control calculation based on voltage deviation ΔVH calculated by voltage deviation calculation map 820. For example, the correction value ΔVH * is obtained by PI (proportional integration) calculation with respect to the voltage deviation ΔVH. When voltage deviation ΔVH> 0, correction value ΔVH * is set to increase system voltage VH. On the other hand, when voltage deviation ΔVH <0, correction value ΔVH * is set so as to decrease system voltage VH.

  Calculation unit 860 calculates voltage command value VHr * according to base value VHr by base command value setting unit 630 and correction value ΔVH * by current phase feedback control unit 805. Arbitration processing unit 870 sets a maximum value among voltage command value VHr * calculated by calculation unit 860 and minimum voltage VHmin * as final system voltage command value VH *.

  Thus, even when rectangular wave voltage control is applied, system voltage command value VH * according to the second embodiment can be set by using current phase feedback instead of modulation degree feedback. That is, basically (when Kmdc = 0), system voltage VH can be set based on the state (modulation degree) of inverter 14 and AC electric motor M1. Furthermore, the system voltage increase unit 700 sets Kmdc> 0 in accordance with the output margin of the power storage device B, in particular, the surplus power ΔPm that can be further supplied from the power storage device B to the AC motor M1. The voltage can be forcibly increased.

  Therefore, even when the rectangular wave voltage control in the boost mode is applied, an effect equivalent to that of system voltage command value setting unit 600 shown in FIG. 20 can be obtained. As a result, the DC link voltage (system voltage) of the inverter 14 is prevented so that the load of the power storage device B does not become excessive and the output power of the AC motor M1 does not become insufficient in a scene where the output increase of the AC motor M1 is detected. VH) can be set appropriately.

  In setting system voltage command value by system voltage command value setting unit 800 according to the control of the AC motor according to the second embodiment, system voltage increasing unit 700 corresponds to an example of “second control means” of the present invention. The configuration of system voltage command value setting unit 800 excluding system voltage increase unit 700 corresponds to an example of “first control means” in the present invention.

  20 and FIG. 22 exemplify a configuration in which the system voltage increase unit 700 increases the system voltage VH by decreasing the modulation degree target value Kmd *. However, the system voltage increase unit 700 uses other methods. For example, the fact that the system voltage VH can be raised by directly correcting the voltage command value VH * will be described in a confirming manner.

  The application of the AC motor control system according to the present embodiment is not limited to the control of the travel motor of the illustrated electric vehicle. If the control system of the AC motor according to the present embodiment is configured to control the AC motor with the application of the rectangular wave voltage control by the inverter whose DC link voltage (system voltage VH) is variably controlled by the converter, the AC motor The present invention can be applied to any electric vehicle without limiting the number of electric motors and the configuration of the power train.

  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.

  5-7 power line, 10 DC voltage generator, 11 monitoring sensor, 12 step-up converter, 13, 19 voltage sensor, 14 inverter, 15-17 upper and lower arms for each phase, 24 current sensor, 25 rotation angle sensor, 30 control device, 40 driving machine system, 41 boosting request line, 42 optimum current phase line, 43 mode switching line, 44 operating point, 45-49 line, 50 driving wheel, 51 target current phase line, 52-55 phase line, 100 control system, 200 PWM controller, 210 Current command generator, 220, 250, 810 Coordinate converter, 240 Voltage command generator, 260 PWM modulator, 355, 830 Feedback calculator, 400 Rectangular wave voltage controller, 410 Power calculator, 420 Torque calculation unit, 430 PI calculation unit, 440 Rectangular wave generation , 450 signal generation unit, 500 boosting mode control unit, 510 first boosting determination unit, 520 second boosting determination unit, 530, 670, 870 arbitration processing unit, 540 minimum voltage setting unit, 550, 560 control request unit, 600, 600 #, 800 system voltage command value setting unit, 610 modulation degree calculation unit, 620 target modulation degree setting unit, 630 base command value setting unit, 632 Vr * map, 635, 660, 715, 860 calculation unit, 650 modulation degree feedback Control unit, 652 Deviation calculation unit, 700 System voltage increase unit, 710 Target modulation degree correction unit, 805 Current phase feedback control unit, 820 Voltage deviation calculation map, Accr accelerator opening, B power storage device, C0, C1 smoothing capacitor, D1 ~ D8 Anti-parallel diode, Fvup boost flag, Ib output current Power storage device), Id d-axis current, Idcom, Iqcom current command value, Iq q-axis current, tKmd boost threshold, tKmd # non-boost threshold, Kmd modulation factor, Kmd * modulation factor target value, Kmdc modulation factor correction value, L1 reactor , LN1 Non-boost maximum torque line, LN2, LN3 boundary line, LN4 Boost maximum torque line, M1 AC motor, Nmt rotation speed (AC motor), Pc boost power, Pm output power (AC motor), Pmmax maximum output power Value (AC motor), Pmt motor power (estimated value), Q1-Q8 power semiconductor switching element, Rpwm PWM request flag, Rvup1, Rvup2 boost request flag, S1-S8 switching control signal, SE signal (system relay), SR1 , SR1 system relay, b Temperature (power storage device), Tq output torque (AC motor), Tqt torque (estimated value), Tqcom torque command value (AC motor), VH DC voltage (system voltage), VH * system voltage command value, VHmax maximum voltage ( System voltage), VHr base value (system voltage command value), VL DC voltage, Vb output voltage (power storage device), Vr motor voltage, Vu, Vv, Vw Phase voltage command, iu, iv, iw Three-phase current (AC) Motor), tAccr, tTq threshold, tVL1 threshold voltage.

Claims (6)

An AC motor control system mounted on an electric vehicle,
A power storage device;
A boost converter configured to perform bidirectional DC power conversion between the power storage device and the power line such that a DC voltage of the power line is controlled according to a voltage command value;
An inverter configured to convert a DC voltage on the power line into an AC voltage applied to the AC motor;
First control means for setting the DC voltage according to the state of the AC motor and the inverter;
An AC motor control system comprising: second control means for setting the DC voltage higher than the voltage set by the first control means in accordance with an output margin of the power storage device. In the non-boosting mode in which the step-up ratio indicated by the ratio of the DC voltage to the output voltage of the power storage device is fixed to 1, the first control means has a modulation factor indicated by the ratio of the AC voltage to the DC voltage or When the current phase of the AC motor advances beyond a predetermined phase, the boost converter is controlled to select a boost mode for setting the voltage command value so that the boost ratio is higher than 1.
The second control unit increases the DC voltage by shifting to the boost mode when the output voltage of the power storage device is lower than a predetermined voltage when the non-boost mode is selected by the first control unit. The control system for an AC motor according to claim 1. The predetermined voltage is higher than a management lower limit voltage of the power storage device,
The AC motor control system according to claim 2, wherein the voltage difference between the predetermined voltage and the management lower limit voltage is set based on a voltage drop amount generated in the power storage device at the maximum output of the AC motor. The first control means targets a modulation degree indicated by a ratio of the AC voltage to the DC voltage in a boost mode in which a boost ratio indicated by a ratio of the DC voltage to an output voltage of the power storage device is greater than 1. Set the voltage command value of the boost converter to approach the modulation degree,
When the second control means detects an increase in the output of the AC motor, the voltage command value is set according to a power margin that can be additionally output from the power storage device to the AC motor. 2. The control system for an AC motor according to claim 1, wherein the control system is set higher than a set value by the control means.   The second control means detects the increase in output in response to the accelerator opening degree of the electric vehicle exceeding a predetermined threshold, and increases the voltage command value by decreasing the target modulation degree. The control system for an AC electric motor according to claim 4.   The second control means detects the increase in output in response to a torque command value to the AC motor exceeding a predetermined threshold, and increases the voltage command value by decreasing the target modulation degree. The control system for an AC electric motor according to claim 4.

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