JP4908327B2 - Electric vehicle control device and electric vehicle - Google Patents

Description

  The present invention relates to a control device for controlling an electric vehicle provided with a permanent magnet synchronous motor, and an electric vehicle controlled by the control device.

  Conventionally, induction motors have been widely used in electric vehicles such as railway vehicles equipped with AC motors. On the other hand, in order to reduce the size and weight of an electric motor, an electric vehicle using a permanent magnet synchronous motor has recently been proposed and put into practical use.

When driving the wheels of an electric vehicle with a permanent magnet synchronous motor, when the speed of the vehicle is large and the rotational speed of the permanent magnet synchronous motor is large, the electromotive force of the motor is proportional to the rotational speed, which is a problem. . When driving a permanent magnet synchronous motor using an inverter that converts DC voltage to AC voltage of variable voltage and variable frequency, if the electromotive force is higher than the DC voltage, the vehicle moves from the power running state or the regenerative state to the coasting state, When the operation of the reverse converter is stopped, a current flows from the permanent magnet synchronous motor to the DC voltage side via the reverse converter, and braking torque is generated in the permanent magnet synchronous motor. When braking torque is generated, coasting is lost, which is not preferable. As a method for preventing the generation of the braking torque, for example, as disclosed in Patent Document 1, a current for suppressing the magnetic flux of the permanent magnet is passed even in the coasting state to suppress the terminal voltage of the permanent magnet synchronous motor.
JP 2005-253264 A

  If a current that suppresses the magnetic flux generated by the permanent magnet is passed even in the coasting state, copper loss occurs in the winding resistance of the permanent magnet synchronous motor. Also, loss occurs in the inverse converter.

  An object of the present invention is to suppress a loss during coasting in an electric vehicle using a permanent magnet synchronous motor, even when the electromotive force of the permanent magnet synchronous motor is high, it is not necessary to flow a current that suppresses the magnetic flux by the permanent magnet. There is to be able to do it.

The present invention is applied to an electric vehicle including a permanent magnet synchronous motor. Further, the received AC voltage is stepped down, the stepped-down AC voltage is converted into a DC voltage, the converted DC voltage is converted into an AC voltage with a variable voltage and a variable frequency, and the permanent magnet is synchronized with the AC voltage with the variable voltage and the variable frequency. The present invention is applied to an electric vehicle that performs control for driving an electric motor to rotate wheels of the electric vehicle.
In the present invention, when the electric vehicle shifts from the power running state or the regenerative state to the coasting state, the operation of converting the DC voltage into the AC voltage of the variable voltage variable frequency is stopped, and the electromotive force of the permanent magnet synchronous motor is When the voltage is higher than the reference voltage that is the DC voltage in the state or the regenerative state, the DC voltage is controlled to be higher than the reference voltage, and the current of the permanent magnet synchronous motor is suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, even when the electromotive force by the magnetic flux of a permanent magnet is high, the control apparatus of the vehicle which does not flow an electric current through a permanent magnet synchronous motor is realizable.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a configuration of an example of the present embodiment.
A vehicle 1 configured as a railway electric vehicle receives AC voltage and rotates a wheel 3 by a permanent magnet synchronous motor 7 mounted on a carriage (not shown).

A configuration for receiving the AC voltage and driving the permanent magnet synchronous motor 7 will be described. The current collector 2 and the wheels 3 of the vehicle 1 receive AC voltage from the outside, and the transformer 4 performs step-down. The AC voltage to be received is a relatively high voltage such as 25000V, for example.
The AC voltage stepped down by the transformer 4 is converted into a DC voltage by the forward converter 5. When converting to DC voltage by the forward converter 5, the voltage value of the DC voltage is set based on the DC voltage command Vdc * from the control device 100. The DC voltage converted by the forward converter 5 is converted by the inverse converter 6 into an AC voltage of variable frequency and variable voltage. The frequency and voltage of the AC voltage are set based on the gate command signal G output from the control device 100. The AC voltage of the variable frequency variable voltage converted by the inverse converter 6 is supplied to the permanent magnet synchronous motor 7 to rotate the permanent magnet synchronous motor 7.

  A gear 8 is provided between the permanent magnet synchronous motor 7 and the wheel 3 to reduce the speed. However, as a configuration in which the gear 8 is not provided, the motor 7 may directly drive the wheels 3. The rotation of the wheel 3 is detected by the speed detector 9 and a vehicle speed VT that is the speed of the vehicle 1 is output. The speed detector 9 can be connected to the permanent magnet synchronous motor 6 instead of the wheel 3.

The reverse converter 6 includes a capacitor C connected to the forward converter 5 and two arms connected in series with the valve device Q and the reverse blocking device D connected in series. Configured to generate a three-phase alternating current. A connection point of two arms connected in series is connected to the permanent magnet synchronous motor 7. As the valve device Q, a switching element such as IGBT or MOSFET is used, and as the reverse blocking device D, a diode is used.
Note that the processing in the transformer 4, forward converter 5 and reverse converter 6 described so far is processing when the vehicle 1 is in a power running state, and when the vehicle 1 is in a regenerative state, a permanent magnet synchronous motor. A regenerative operation is performed in which the AC voltage generated by the rotation of 7 is processed through the reverse path and is sent to the outside via the current collector 2 and the wheel 3. FIG. 1 shows a specific configuration of the reverse converter 6, and a specific configuration of the forward converter 5 is omitted. The forward converter 5 is similarly configured by connecting a valve device and a reverse blocking device. As described above, the conversion from AC to DC (or vice versa) is performed. The forward converter 5 can control the voltage value of the DC voltage to be converted, for example, by controlling the timing for turning on and off the valve device during conversion.

  The control device 100 includes a vehicle control unit 101, a voltage control unit 102, and a PWM (Pulse Width Modulation) control unit 103. A notch command N from a master controller (mass controller) 10 installed in the cab of the vehicle 1 or another vehicle (not shown) and a vehicle speed VT from the speed detector 9 are supplied to the control device 100. The notch command N is a command output when the driver operates the master controller 10 on the cab. The control device 100 generates and outputs a DC voltage command Vdc * and a gate signal G based on the supplied notch command N and vehicle speed VT.

Notch command N and vehicle speed VT are supplied to vehicle control unit 101 in control device 100. Based on the notch command N and the vehicle speed VT, the vehicle control unit 101 generates and outputs a DC voltage command Vdc *, a torque command T *, and a suppress command Sup. The DC voltage command Vdc * is supplied to the forward converter 5 to set a DC voltage to be converted by the forward converter 5. In this example, as described later, when a certain condition is satisfied, control is performed such that the DC voltage converted by the forward converter 5 is higher than the normal voltage (reference voltage). Details of the process for controlling the DC voltage will be described later.
Torque command T * is supplied from vehicle control unit 101 to voltage control unit 102.
Based on the supplied torque command T *, the voltage control unit 102 generates and outputs a motor voltage command V * so that the output torque of the permanent magnet synchronous motor 6 matches the torque command T *. The PWM control unit 103 performs pulse width modulation based on the voltage command V * so that the AC side voltage of the inverse converter 6 matches the voltage command V *. In order to perform this pulse width modulation, a gate signal G for controlling the valve device Q is output. However, when the suppress command Sup is valid, the gate signal G is output so that all the valve devices Q are opened regardless of the voltage command V *.

Next, the detail of the control state by the vehicle control part 101 is demonstrated using FIG.2 and FIG.3.
FIG. 2 is a state transition diagram of the vehicle control unit 101, and FIG. 3 is a table showing an output for each state. When the vehicle 1 is stopped, the vehicle control unit 101 is in a stopped state. As shown in FIG. 3, the DC voltage command Vdc * is a preset reference voltage V1, the torque command T * is 0, and the suppress command Sup is valid. Is output. When the notch command N changes to power running, the state of the vehicle control unit 101 transitions to the power running state, the DC voltage command Vdc * is determined in advance corresponding to the reference voltage V1, and the torque command T * is determined in advance corresponding to the notch command N and the vehicle speed VT. Outputs the power running torque. In addition, the suppress command Sup outputs invalid.

When the notch command becomes neutral in the power running state, the state changes to the low speed coasting state or the high speed coasting state according to the vehicle speed VT. When the vehicle speed VT is lower than the reference speed VT1, a transition is made to the low-speed coasting state, and the DC voltage command Vdc * is output as the reference voltage V1, the torque command T * is 0, and the suppress command Sup is enabled. The reference speed VT1 is set to a vehicle speed at which the electromotive force E of the permanent magnet synchronous motor 7 is lower than the DC voltage Vdc, which is the DC side voltage of the inverse converter.
Therefore, in the low-speed coasting state, when the suppression command Sup is enabled and all the valve devices Q are opened, the reverse electromotive force E is lower than the DC voltage Vdc. No current flows through the motor 7.

  On the other hand, when the vehicle speed VT is equal to or higher than the reference speed VT1, a transition is made to the high-speed coasting state, and the torque command T * is output as 0 and the suppress command Sup is enabled. When the DC voltage Vdc is lower than the electromotive force E, the reverse converter 6 can output only a voltage lower than the electromotive force E, so that the reverse blocking device D becomes conductive and current flows, and the motor current of the permanent magnet synchronous motor 7 I cannot be 0. Therefore, in this example, the DC voltage command Vdc is gradually increased from the reference voltage V1 so that the motor current I becomes zero. When the DC voltage command Vdc * becomes higher than the electromotive force E, the reverse blocking device D does not become conductive, so the motor current I can be set to zero. The voltage that makes the DC voltage higher than the reference voltage V1 in this high-speed coasting state is, for example, a voltage value that is about 10% to 20% higher than the reference voltage V1.

In the low-speed coasting state, when the notch command N becomes the power running, the state transits to the power running state, and when the notch command N becomes the regeneration, the state transits to the regeneration state. In the regenerative state, the DC voltage command Vdc * outputs a reference voltage V1, and the torque command T * outputs a predetermined regenerative torque corresponding to the notch command N and the vehicle speed VT. In addition, the suppress command Sup outputs invalid.
When the notch command N changes to power running or regeneration in the high-speed coasting state, the DC voltage command Vdc * is reduced to the reference voltage V1. When the DC voltage command Vdc * coincides with the reference voltage V1, the state transits to the power running state or the regenerative state according to the notch command N.
In the regenerative state, when the vehicle 1 stops, the state transits to the stopped state. In the regenerative state, when the notch command becomes neutral, as in the power running state, when the vehicle speed VT is lower than the reference speed VT1, a transition is made to the low speed coasting state, and when the vehicle speed VT is equal to or higher than the reference speed VT1, the high speed coasting state. Transition to.

Next, a specific operation example according to the first embodiment of the present invention will be described with reference to FIG.
The horizontal axis of the graph of FIG. 4 is time, and the vertical axis of FIG. 4A is the notch command N, FIG. 4B is the control state of the vehicle control unit 101 (ie, the traveling state of the vehicle 1), and FIG. ) Is the DC voltage command Vdc * and the electromotive force E of the permanent magnet synchronous motor 7, FIG. 4 (d) is the torque command T *, FIG. 4 (e) is the suppress command Sup, and FIG. 4 (f) is the permanent magnet synchronous motor 7. 4 is the vehicle speed VT detected by the speed detector 9.

Referring to FIG. 4, the vehicle 1 is initially stopped, the notch command N is neutral, the vehicle control unit 101 is stopped, the DC voltage command Vdc * is the reference voltage V1, and the electromotive force E is stopped. Therefore, 0, the suppress command Sup is valid, and the torque command T *, the motor current I, and the vehicle speed VT are all 0.
At time T1, when the notch command N becomes power running, the state of the vehicle control unit 101 changes to a power running state. At this time, the DC voltage command Vdc * remains at the reference voltage V1, the torque command T * commands the power running torque, and the suppress command Sup becomes invalid. As a result, motor current I flows, vehicle 1 accelerates, and vehicle speed VT increases. Further, the electromotive force E also increases according to the vehicle speed VT.
When the vehicle speed VT exceeds the reference speed VT1 at time T2, the electromotive force E also exceeds the reference voltage V1.
When notch command N changes to neutral at time T3, the state of vehicle control unit 101 transitions to the high-speed coasting state because vehicle speed VT is equal to or higher than reference speed VT1. At this time, the torque command T * becomes 0, and the suppress command Sup becomes valid at time T4 immediately after time T3. However, since the electromotive force E is larger than the DC voltage command Vdc *, a current flows from the permanent magnet synchronous motor 7 to the DC side via the reverse blocking device D of the reverse converter 6, so that the motor current I becomes 0 as it is. Don't be.
Here, in the case of this example, a process for increasing the DC voltage command Vdc * so that the motor current becomes zero is performed. In the example of FIG. 4, at time T5, when the DC voltage command Vdc * becomes larger than the electromotive force E, no current flows through the reverse blocking device D, and the motor current I becomes zero.

Next, when the notch command N is regenerated at time T6, the DC voltage command Vdc * is decreased to the reference voltage V1. Thereby, since DC voltage command Vdc * becomes smaller than electromotive force E, motor current I flows. When the DC voltage command Vdc * becomes the reference voltage V1 at time T7, the state of the vehicle control unit 101 becomes the regenerative state, the torque command commands the regenerative torque, the suppress command Sup is invalidated, and the permanent magnet synchronous motor 7 is controlled. Resumed.
In addition, in the example of FIG. 4, although the example which changed to the regenerative state from the high-speed coasting state is shown, as shown in the state transition diagram of FIG. Control is performed.

  As described above, even when the notch command N is set to neutral at a speed equal to or higher than the reference speed VT1, it is possible to control the motor current to 0 by increasing the DC voltage command Vdc *. Note that, when the speed is lower than the reference speed VT1, the same control as in the prior art is performed, so that the motor current is zero as in the prior art. Therefore, no current that suppresses the magnetic flux generated by the permanent magnet flows during the ellipse, and no copper loss occurs in the winding resistance of the permanent magnet synchronous motor. Also, no loss occurs in the inverse converter. For this reason, it is possible to suppress loss during coasting. Further, since the DC voltage is increased only during coasting, the load on the forward converter and the reverse converter can be reduced.

  In the present embodiment, after the suppression command Sup is validated, the DC voltage command Vdc * is increased and changed. However, after the DC voltage command Vdc * is first increased and becomes equal to or higher than the electromotive force E, It is also possible to validate the suppress command Sup. In this case, it is necessary to operate the inverter while the DC voltage command Vdc * is high, but it is possible to suppress the generation of braking torque while increasing the DC voltage command Vdc *.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 5 to 8, members having the same configurations as those in FIGS. 1 to 4 described in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

5 differs from the configuration of FIG. 1 described in the first embodiment in that a control device 200 is different and a load breaker 11 is provided. The load breaker 11 is installed between the inverter 6 and the permanent magnet synchronous motor 7 and is opened and closed based on the load breaker signal SWl.
Based on the notch command N from the main controller 10 and the vehicle speed VT from the speed detector 9, the control device 200 outputs the load circuit breaker signal SWl in addition to the DC voltage command Vdc * and the gate signal G. Based on the notch command N and the vehicle speed VT, the vehicle control unit 201 outputs a DC voltage command Vdc *, a suppress command Sup, a torque command T *, and a load breaker signal SWl. The state transition of the vehicle control unit 201 is the same as that of the vehicle control unit 101 shown in FIG. 2 described in the first embodiment, but the output of the load breaker signal SWl and the operation in the high-speed coasting state are different.

An outline of the output of each state of the vehicle control unit 201 is summarized in FIG.
As shown in FIG. 6, the load circuit breaker signal SWl is in a short circuit state in which the reverse converter 6 and the permanent magnet synchronous motor 7 are connected except in the high speed coasting state. Next, the operation in the high-speed coasting state will be described. In the high-speed coasting state, the torque command T * is first set to 0 and the suppress command Sup is made valid. Next, the DC current command Vdc * is increased so that the motor current I becomes zero. When the DC voltage command Vdc * becomes equal to or higher than the electromotive force E and the motor current becomes 0, the load circuit breaker signal SWl is switched to open, and the inverse converter 6 and the permanent magnet synchronous motor 7 are disconnected. Thereafter, the DC voltage command Vdc * is returned to the reference voltage V1. When the notch signal N changes to powering or regeneration in this state, the DC voltage command Vdc * is increased to the electromotive force E or more, and the load breaker signal SWl is short-circuited. Next, the DC voltage command Vdc * is reduced and returned to the reference voltage V1. When the DC voltage command Vdc * reaches the reference voltage V1, if the notch signal is a power running, the state transits to a power running state.

Next, the specific operation of the second embodiment will be described with reference to FIG.
The horizontal axis of the graph of FIG. 7 is time, the vertical axis is notch command N, FIG. 7B is the state of the vehicle control unit 201, and FIG. 7C is the DC voltage command Vdc * and permanent. The electromotive force E of the magnet synchronous motor 7, FIG. 7 (d) is the torque command T *, FIG. 7 (e) is the suppress command Sup, FIG. 7 (f) is the load circuit breaker signal SW1, and FIG. 7 (g) is the motor current. I, FIG. 7 (h) is the vehicle speed VT. Note that the notch signal N is basically the same as that in FIG. 4, and the description of the same operation as in the first embodiment is omitted.

Referring to FIG. 7, the vehicle is initially stopped, the notch command N is neutral, the vehicle control unit 201 is stopped, the DC voltage command Vdc * is the reference voltage V1, and the electromotive force E is stopped. 0, the suppress command Sup is valid, the load circuit breaker signal SWl is short-circuited, and the torque command T *, the motor current I, and the vehicle speed VT are all zero.
At time T11, the notch command N becomes power running, and the state transitions to the power running state. The load circuit breaker signal SWl maintains the short circuit state, and the other operations are the same as those at time T1 in FIG. At time T12, the vehicle speed VT exceeds the reference speed VT1.
At time T13, the notch command N changes to neutral. The state of the vehicle control unit 201 transitions to a high-speed coasting state because the vehicle speed VT is equal to or higher than the reference speed VT1. At this time, the torque command T * becomes 0, and the suppress command Sup becomes valid at time T14. However, since the electromotive force E is larger than the DC voltage command Vdc *, a current flows from the permanent magnet synchronous motor 7 to the DC side via the reverse blocking device D of the reverse converter 6, so the motor current I does not become zero.

  In this state, when the DC voltage command Vdc * is increased so that the motor current becomes zero, when the DC voltage command Vdc * becomes larger than the electromotive force E, no current flows to the reverse blocking device D, and at time T15. The motor current I becomes zero. When the motor current I becomes 0, the vehicle control unit 201 switches the load circuit breaker signal SWl to the circuit break, disconnects the inverse converter 6 and the permanent magnet synchronous motor 7, and returns the DC voltage command Vdc * to the reference voltage V1. . At this time, the DC voltage command Vdc * is smaller than the electromotive force E, but since the load circuit breaker 11 is opened, the motor current I does not flow. The motor current I when the load circuit breaker signal SWl is interrupted may be a current value set in advance in a current range that can be interrupted by the load circuit breaker 11.

  At time T16, when the notch command N is regenerated, the DC voltage command Vdc * is increased to the electromotive force E or more, and the load circuit breaker signal SWl is short-circuited. At this time, the motor current I does not flow. Next, the DC voltage command Vdc * is reduced and returned to the reference voltage V1. As a result, the DC voltage command Vdc * becomes smaller than the electromotive force E, so that the motor current I begins to flow. When the DC voltage command Vdc * becomes the reference voltage V1 at time T17, the state of the vehicle control unit 201 becomes the regenerative state, the torque command instructs the regenerative torque, the suppress command Sup becomes invalid, and the permanent magnet synchronous motor 7 is controlled. Is resumed.

  As described above, even when the notch command N is set to neutral at a speed equal to or higher than the reference speed VT1, by increasing the DC voltage command Vdc *, the load breaker 11 can be opened and closed with the motor current being zero. The load on the contact of the load circuit breaker is small, and the frequency of inspection and replacement can be reduced. Since the load circuit breaker 11 is opened during coasting, the motor current I can be set to zero. Furthermore, since the DC voltage during coasting can be used as a reference voltage, the voltage applied to the forward converter and the reverse converter can be suppressed, and the stress on the device used can be reduced.

In the example of the second embodiment shown in FIG. 7, the load circuit breaker is short-circuited after the DC voltage command Vdc * is increased when transitioning from the high-speed coasting state to the powering state or the regenerative state. However, it is also possible to short-circuit the load circuit breaker signal Swl in a state where the DC voltage command Vdc * is held at the reference voltage V1.
That is, as shown in FIG. 8, when changing from the high-speed coasting state to the regenerative (or powering) state at times T16 and T17, as shown in FIG. 8C, the DC voltage command Vdc * is changed to the reference voltage V1. The motor breaker signal Swl may be short-circuited to generate the motor current I as shown in FIG. The other parts of FIG. 8 are the same as those of FIG.
When the control is performed as shown in FIG. 8, an inrush current may flow when the load breaker 11 is short-circuited, but the time until the regenerative torque is generated can be shortened.

  In each of the embodiments described so far, it is determined whether or not the voltage generated by the permanent magnet synchronous motor exceeds the reference voltage from the speed of the vehicle when the high-speed coasting state is entered. If the voltage of the magnet synchronous motor or the DC voltage between the forward converter 5 and the reverse converter 6 can be directly measured, the measured voltage may be compared with the reference voltage for determination.

It is a block diagram which shows the structural example by the 1st Embodiment of this invention. It is a state transition diagram according to the first embodiment of the present invention. It is explanatory drawing which showed the output for every state of the vehicle control part by the 1st Embodiment of this invention. It is explanatory drawing which shows the example of the control state by the 1st Embodiment of this invention on a time-axis. It is a block diagram which shows the structural example by the 2nd Embodiment of this invention. It is explanatory drawing which showed the output for every state of the vehicle control part by the 2nd Embodiment of this invention. It is explanatory drawing which shows the example of the control state by the 2nd Embodiment of this invention on a time-axis. It is a timing chart which shows the example of the control state by the modification of the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Current collector, 3 ... Wheel, 4 ... Transformer, 5 ... Forward converter, 6 ... Reverse converter, 7 ... Permanent magnet synchronous motor, 8 ... Gear, 9 ... Speed detector, 10 ... Main trunk Control unit, 11 ... Load circuit breaker, 100 ... Control device, 101 ... Vehicle control unit, 102 ... Voltage control unit, 103 ... PWM control unit, 200 ... Control device, 201 ... Vehicle control unit

Claims (8)

An electric vehicle control device including a permanent magnet synchronous motor,
The received AC voltage is stepped down, the stepped-down AC voltage is converted into a DC voltage, the converted DC voltage is converted into an AC voltage of variable voltage and variable frequency, and the permanent magnet synchronous motor is converted by the AC voltage of the variable voltage and variable frequency. In an electric vehicle control device that controls driving and rotating wheels of an electric vehicle,
When an electric vehicle moves from a power running state or a regenerative state to a coasting state,
Stops the operation to convert DC voltage to AC voltage with variable voltage and variable frequency,
When the electromotive force of the permanent magnet synchronous motor becomes higher than a reference voltage that is a DC voltage in a power running state or a regenerative state, the DC voltage is controlled to be higher than the reference voltage, and the current of the permanent magnet synchronous motor is suppressed. A control device for an electric vehicle. The control apparatus for an electric vehicle according to claim 1,
The determination that the electromotive force of the permanent magnet synchronous motor is higher than the reference voltage is made according to the speed of the vehicle when moving from the power running state or the regenerative state to the coasting state. Control device. The control apparatus for an electric vehicle according to claim 1,
In the coasting state, when the current of the permanent magnet synchronous motor becomes smaller than a preset value, control is performed to open the AC supply path of the variable voltage variable frequency to the permanent magnet synchronous motor. Electric vehicle control device. The control device for an electric vehicle according to claim 3,
A control apparatus for an electric vehicle, wherein after the opening, control is performed to return the DC voltage to the reference voltage from a state in which the DC voltage is controlled to be higher than the reference voltage. In an electric vehicle equipped with a permanent magnet synchronous motor,
A transformer that steps down the received AC voltage;
A forward converter that converts the AC voltage stepped down by the transformer into a DC voltage;
A DC converter converted by the forward converter into an AC voltage of variable voltage and variable frequency, and an inverter that drives the permanent magnet synchronous motor with the converted AC voltage of variable voltage and variable frequency.
When an electric vehicle moves from a power running state or a regenerative state to a coasting state,
Stop the operation of the inverse converter,
When the electromotive force of the permanent magnet synchronous motor is higher than a reference voltage that is a DC voltage in a power running state or a regenerative state, the DC voltage converted by the forward converter is made higher than the reference voltage, and the permanent magnet synchronization An electric vehicle characterized by suppressing an electric current of an electric motor. The electric vehicle according to claim 5, wherein
The determination that the electromotive force of the permanent magnet synchronous motor becomes higher than the reference voltage is made in accordance with the speed of the vehicle when moving from the power running state or the regenerative state to the coasting state. The electric vehicle according to claim 5, wherein
In the coasting state, when the current of the permanent magnet synchronous motor becomes smaller than a preset value, the circuit breaker provided between the inverse converter and the permanent magnet synchronous motor is opened. vehicle. The electric vehicle according to claim 7, wherein
An electric vehicle that returns the reference voltage from a state in which the DC voltage is controlled to be higher than the reference voltage after opening the circuit breaker.

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