JP2015211533A - Control device and control method for motor vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device and a control method for a motor vehicle capable of maintaining a safety measure for a DC short circuit or the like of an inverter of a motor for driving a vehicle, while assuring performance of 3-phase short circuit control by the inverter and contributing reduction in size of an inverter and increase in output of a motor.SOLUTION: A current value of a motor at the time of 3-phase short circuit is estimated, the estimated current value is set as a target value, and a current of the motor is controlled S2, S3, and then the inverter is controlled into a 3-phase short circuit state S4.

Description

  The present invention relates to a control device and a control method for an electric vehicle.

  In recent years, taking into consideration environmental problems and the like, development of electric vehicles such as electric vehicles and fuel cell vehicles that can be driven only by a motor (electric motor), and hybrid electric vehicles that use an engine and a motor as drive sources has been progressing. Electric vehicles mainly use a three-phase motor as a motor as a drive source, and electric power is supplied to the motor via an inverter that converts a direct current from a battery power source into an alternating current.

  In such an electric vehicle, three-phase short-circuit control may be performed for safety control or warm-up control (see, for example, Patent Document 1). For example, when three-phase short-circuit control is performed as safety control, when an abnormality such as insulation deterioration occurs in one phase of the high-voltage line between the inverter and the motor, the induced voltage due to the rotation of the motor does not appear on the AC power line to prevent electric shock Therefore, three-phase short-circuit control is performed in which all three phases are short-circuited by an inverter as safety control when an abnormality occurs.

  When such three-phase short-circuit control is started, a large current flows transiently as an inrush current when shifting from normal control to three-phase short-circuit control. There is no risk of serious damage to such devices.

JP 2009-292369 A

  However, on the other hand, in order to prevent a serious situation such as ignition mainly at the time of a failure such as a DC short circuit, all semiconductor elements are turned off when an overcurrent exceeding the limit of the inverter performance is detected. A hardware-side safety mechanism is also provided. This hardware-side safety mechanism can detect an abnormality for a very short time, and the inrush current at the start of the three-phase short-circuit control may be erroneously detected as a serious abnormality.

  The operation of the safety mechanism when an overcurrent on the hardware side is detected is an operation of turning off all semiconductor elements, contrary to the operation of the three-phase short-circuit control that short-circuits the AC side for three phases. There is a problem that short-circuit control cannot be performed properly.

  In recent years, in electric vehicles, there is an increasing demand for downsizing of the inverter from the viewpoints of lightening the system, reducing the cost, improving the mountability, and improving the electric efficiency. In order to reduce the size of the inverter, it is necessary to reduce the current capacity of the inverter and set the current threshold value at which the safety mechanism operates to be lower. That is, if the inverter is downsized, there is a problem that the possibility of detecting an overcurrent is further increased by the inrush current at the start of the three-phase short-circuit control. At the same time, there is a growing demand for higher motor output. When a high-power motor is used, the inrush current at the start of three-phase short-circuit tends to increase. There is a problem that the possibility of detecting an overcurrent is further increased.

  For this reason, conventionally, when designing an electric vehicle system, the inrush current at the start of the three-phase short-circuit control must be taken into consideration, and an inverter current capacity must be provided to prevent erroneous detection. Miniaturization, and consequently high motor output, has been impeded.

  The present invention has been made to solve at least a part of such problems. The object of the present invention is to reliably carry out three-phase short-circuit control while maintaining safety measures against DC short-circuit in the inverter. An object of the present invention is to provide a control device and a control method for an electric vehicle that can realize appropriate safety measures and contribute to downsizing of the inverter and high output of the motor. .

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

  (1) An electric vehicle control device according to this application example includes: an electric motor that is a driving source of the vehicle; a battery that can store electric power for driving the electric motor; and a direct current and an electric current between the battery and the electric motor. An inverter that performs AC conversion; a three-phase short-circuit control unit that controls the inverter to a three-phase short-circuit state; and a current value of the motor in the three-phase short-circuit state is estimated, and the estimation is performed before the three-phase short-circuit control is started. Pre-current control means for controlling the current of the motor for a predetermined time using the current value as a target value.

  (2) In the control apparatus for an electric vehicle according to the application example, the prior current control unit performs a three-phase short circuit according to a rotation speed and a temperature of the motor at the time of determining the execution of the three-phase short circuit control. The current value of the motor at the time may be estimated.

  (3) In the control apparatus for an electric vehicle according to the application example, the prior current control unit includes a map that stores a current value at the time of a three-phase short circuit according to a state of the electric motor, and is based on the map. The current value of the motor when the three-phase short circuit is performed may be estimated.

  (4) The control apparatus for an electric vehicle according to the application example further includes an abnormality detection unit that detects an abnormality related to energization in a power supply circuit including the electric motor, the inverter, and the battery, and the prior current control unit When an abnormality is detected by the abnormality detection means, the current value of the motor when a three-phase short circuit is caused in the state of the motor at the time of the abnormality is estimated, and the estimated current value is set as a target value. The electric current of the electric motor may be controlled.

  (5) In the control apparatus for an electric vehicle according to the application example, the inverter includes a safety mechanism that turns off all the semiconductor elements of the inverter when the current in the inverter becomes equal to or greater than a predetermined threshold. You may have.

  (6) An electric vehicle control method according to this application example includes: an electric motor that is a drive source of the vehicle; a battery that can store electric power for driving the electric motor; and a direct current and an electric current between the battery and the electric motor. An inverter that performs AC conversion, and a three-phase short-circuit control execution determination step that determines whether or not it is necessary to perform three-phase short-circuit control in the inverter; A pre-current control step of estimating a current value of the motor in a short-circuit state, and controlling the current of the motor for a predetermined time using the estimated current value as a target value; and the electric motor in the pre-current control step And a three-phase short-circuit control step for controlling the inverter to a three-phase short-circuit state after the current control.

  (7) In the method for controlling an electric vehicle according to the application example described above, in the preliminary current control step, a three-phase short circuit is performed according to a rotation speed and a temperature of the electric motor at the time of execution determination of the three-phase short circuit control. The current value of the motor at the time may be estimated.

  (8) In the control method for an electric vehicle according to the application example, in the preliminary current control step, a three-phase short circuit is performed based on a map storing a current value at the time of a three-phase short circuit according to the state of the motor. The current value of the motor at the time may be estimated.

  (9) The method for controlling an electric vehicle according to the application example further includes an abnormality detection step of detecting an abnormality relating to energization in a power supply circuit including the electric motor, the inverter, and the battery, and the abnormality detection step. When an abnormality is detected, the current value of the motor when a three-phase short circuit is caused in the state of the motor at the time of the abnormality is estimated, and the current of the motor is controlled using the estimated current value as a target value. May be.

  (10) In the method for controlling an electric vehicle according to the application example, the inverter includes a safety mechanism that turns off all the semiconductor elements of the inverter when the current in the inverter exceeds a predetermined threshold. You may do it.

  According to the present invention using any one of the above application examples, while ensuring safety measures against DC short-circuits in the inverter, the reliable implementation of the three-phase short-circuit control is ensured, and the inverter is downsized and the motor output is increased. Can help.

(A) It is a schematic block diagram of the electric vehicle provided with the control apparatus which concerns on one Embodiment of this invention, (b) It is a schematic block diagram of an inverter. It is a related figure of Id and Iq according to the number of rotations and temperature of a motor. It is the flowchart which showed the safety control routine which inverter ECU of the control apparatus which concerns on one Embodiment of this invention performs. It is a graph which shows a current waveform at the time of performing three-phase short circuit control, without performing prior current control. It is a graph which shows a current waveform at the time of performing three-phase short circuit control, after performing prior current control.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 (a) shows a schematic configuration diagram of a control device for an electric vehicle according to an embodiment of the present invention, and FIG. 1 (b) shows a schematic configuration diagram of an inverter.

  The electric vehicle 1 in the present embodiment shown in FIG. 1A is a so-called parallel hybrid truck that uses an engine 2 and a motor 3 (electric motor) as a travel drive source, and is simply referred to as a vehicle in the following description.

  A clutch 4 is connected to the output shaft of the engine 2, and an input side of the transmission 5 is connected to the clutch 4 via a rotating shaft of the motor 3. A differential device 7 is connected to the output side of the transmission 5 via a propeller shaft 6, and left and right drive wheels 9 are connected to the differential device 7 via a drive shaft 8.

  The motor 3 is a so-called three-phase motor, specifically, a synchronous generator motor including a rotor on which a permanent magnet is attached and a stator on which a three-phase coil is wound. The motor 3 is connected via an inverter 10 to a battery 11 that can store electric power for driving the motor 3.

  The inverter 10 performs direct current and alternating current conversion between the battery 11 and the motor 3. A power supply circuit including the motor 3, the inverter 10, and the battery 11 is specifically shown in FIG. As shown in FIG. 1B, the inverter 10 includes a pair of switching elements (semiconductor elements) 12a to 12f (for example, IGBT: insulated gate bipolar transistor) for each phase connected to the three-phase coil of the motor 3. This is a power converter that converts a direct current and a three-phase alternating current by a phase bridge circuit, or converts a voltage of supplied power. That is, the inverter 10 can convert DC power from the battery 11 into three-phase AC power and supply it to the motor 3, and can rectify and supply three-phase AC power from the motor 3 to the battery 11. .

  The inverter 10 includes a current control unit 13 that turns on and off the switching elements 12a to 12f. The current control unit 13 includes a drive circuit that controls ON and OFF of the switching elements 12a to 12f, and can control the phase of the current flowing through the inverter 10 and the like. Further, the current control unit 13 includes a safety mechanism that switches all the switching elements 12a to 12f to the OFF state as hardware when the current in the inverter 10 exceeds a predetermined safety threshold due to a DC short circuit or the like.

  The current control unit 13 is connected to the inverter ECU 14, calculates a target value of the current that the inverter ECU 14 flows to the motor 3, and sends a command to the current control unit 13. For example, the inverter ECU 14 monitors the state of the inverter 10 such as current and voltage flowing through the inverter 10 and is also connected to the motor 3 to detect and monitor the state of the motor 3 such as the rotation speed and temperature of the motor 3. Yes. Information about the state of the motor 3 is not limited to being obtained directly from the motor 3, and can be obtained from a motor ECU (not shown), for example. The inverter ECU 14 acquires various types of information and gives a command to the current control unit 13 to control the inverter 10 in accordance with the required operating state.

  The vehicle 1 configured as described above travels by transmitting the driving force generated by the engine 2 or the motor 3 by the transmission 5 and then transmitting it to the driving wheels 9. For example, when the vehicle 1 decelerates or travels on a downhill road, the motor 3 operates as a generator by reverse driving from the drive wheel 9 side. The negative driving force generated by the motor 3 is transmitted to the driving wheel 9 side as a braking force, and the AC power generated by the motor 3 is converted into DC power by the inverter 10 and charged to the battery 11.

  The inverter ECU 14 controls the inverter 10 according to the state of the motor 3, the required torque, etc., and also monitors whether there is an abnormality in the inverter 10, and has a function of executing safety control when an abnormality is detected. Yes.

  Moreover, the control device for the electric vehicle according to the present embodiment may include abnormality detection means for monitoring the presence or absence of abnormality related to energization in the electric power supply circuit including the battery 11, the inverter 10, and the motor 3.

  The abnormality detection means includes, for example, whether there is a leakage abnormality in the electric wire between the battery 11 and the motor 3 via the inverter 10, a conduction abnormality such as contactor fixation, and an electric conduction abnormality such as a short circuit in the AC electric wire between the inverter 10 and the motor 3. To monitor.

  The abnormality detection means is not limited as long as it can cause the inverter ECU 14 to perform safety control accompanying abnormality detection when an abnormality occurs in the electric wire. For example, as shown in FIG. 1B, the inverter ECU 14 itself may monitor the presence or absence of abnormality in the electric wire between the battery 11 and the motor 3 via the inverter 10. Although not shown, a host ECU or BCU other than the inverter ECU 14 monitors the presence or absence of an abnormality, notifies the inverter ECU 14 of an abnormality by CAN communication or transmits a trigger signal for safety control described later. May be.

  Further, the inverter ECU 14 according to the present embodiment can perform three-phase short-circuit control that short-circuits all phases (three-phase short-circuit control means). The control purpose of the three-phase short-circuit control is not particularly limited. For example, three-phase short-circuit control may be performed as safety control when an energization abnormality occurs. Moreover, you may implement three-phase short circuit control as warm-up control which used the emitted-heat amount at the time of a three-phase short circuit as a heat source.

  More specifically, in the three-phase short-circuit control, all the element groups including one switching elements 12d to 12f among the pair of switching elements of each phase of the inverter 10 shown in FIG. The inverter 10 is brought into a three-phase short-circuit state by turning off all the element groups consisting of ˜12c. On the contrary, the inverter 10 may be in a three-phase short circuit state by setting all of the element groups including the switching elements 12d to 12f to the OFF state and setting all the element groups including the other switching elements 12a to 12c to the ON state.

  When the inverter ECU 14 according to the present embodiment executes the three-phase short circuit control, the current phase and the current value of the inverter 10 are set in advance to the current phase and the current value of the motor 3 at the time of the three-phase short circuit before starting the three-phase short circuit control. Prior current control to be shifted is performed (prior current control means). In the prior current control, the current value of the motor 3 in the three-phase short-circuit state is estimated, and the current of the motor 3 is controlled for a predetermined time using the estimated current value as a target value before starting the three-phase short-circuit control.

  The inverter ECU 14 stores, as a map, the value of a current that flows through the motor 3 during a three-phase short circuit according to the rotation speed and temperature of the motor 3 in order to perform pre-current control. Thereby, the prior current control means can estimate the current value of the motor 3 when the three-phase short-circuit is performed according to the state (the number of revolutions and the temperature) of the electric motor at the time of execution determination of the three-phase short-circuit control.

  Specifically, for example, the prior current control unit according to the present embodiment controls the inverter 10 by a map of Id and Iq using dq conversion, and the map shows a tendency as shown in FIG. 2 as an example. It becomes. As shown in FIG. 2, the value of Id increases as the motor rotational speed increases, and the value of Iq shows a peak at a predetermined motor rotational speed, and tends to decrease when the rotational speed is higher than the peak. Further, Id has a higher value when the motor temperature is lower, and Iq has a tendency that the lower the motor temperature is, the lower the number of revolutions is at a peak. These tendencies depend on the motor characteristics and can be obtained by measurement.

  For example, when an abnormality is detected by the above-described abnormality detection means, the prior current control means refers to a map corresponding to the state of the motor 3 at the time of occurrence of the abnormality, so that the current of the motor 3 when the three-phase short circuit occurs The value can be estimated, and the current of the motor 3 can be controlled using the estimated current value as a target value.

  For example, when it is desired to perform the three-phase short-circuit control for the purpose of warm-up control, the prior current control means refers to the three-phase by referring to a map corresponding to the state of the motor 3 at the time of performing the three-phase short-circuit control. The current value of the motor 3 when short-circuited can be estimated, and the current of the motor 3 can be controlled using the estimated current value as a target value.

  Here, FIG. 3 is a flowchart showing a three-phase short-circuit control start routine executed by the inverter ECU 14, and the control of the inverter 10 performed by the inverter ECU 14 will be described below along the flowchart.

  First, as step S1, the inverter ECU 14 determines whether or not the inverter 10 needs to perform the three-phase short-circuit control (three-phase short-circuit control execution determination step). For example, it may be determined whether or not an abnormality relating to energization that requires execution of three-phase short-circuit control is detected (abnormality detection step), and intentional three-phase short-circuit control is performed in the host ECU regardless of whether there is an abnormality. Judgment may be made. While the determination result is false (No), the step S1 is repeated. On the other hand, if it is determined that the three-phase short-circuit control needs to be performed, the determination result is true (Yes), and the process proceeds to the next step S2.

  In step S2, the inverter ECU 14 estimates the current value (Id, Iq) of the motor 3 at the time of the three-phase short circuit based on the map corresponding to the rotation speed and temperature of the motor 3, and the estimated current value (Id, Iq). ) Is set as the target current value.

  In subsequent step S3, the inverter ECU 14 instructs the current control unit 13 based on the set target current value, and executes the pre-current control for a predetermined time by controlling the current of the inverter 10 to the target current value (pre-current control step). ).

  After the current of the inverter 10 shifts to the current at the time of the three-phase short-circuit by the prior current control, the inverter ECU 14 executes the three-phase short-circuit control (three-phase short-circuit control step) in the next step S4 and ends the routine.

  Here, referring to FIGS. 4 and 5, FIG. 4 is a graph showing a current waveform when the three-phase short-circuit control is executed without executing the pre-current control, and FIG. The graph which shows the current waveform at the time of performing three-phase short-circuit control is shown, The effect of this embodiment is demonstrated, comparing these figures.

  First, as shown in FIG. 4, when the three-phase short-circuit control is executed at the time t1 ′ without performing the pre-current control, an inrush current is generated in the inverter 10, the current waveform is disturbed, and temporarily increases. Current will flow. FIG. 4 shows a state in which the three-phase short-circuit control is maintained. For example, if the safety threshold provided in the current control unit 13 of the inverter 10 is a value indicated by a one-dot chain line, this temporary large current is When the safety threshold is exceeded, the safety mechanism is activated at time t2 ′, and the switching elements 12a to 12f of the inverter 10 are all turned off and the three-phase short-circuit control cannot be maintained.

  On the other hand, as shown in FIG. 5, in the control apparatus for the electric vehicle in the present embodiment, the pre-current control is performed at a time before the time t1 when the inverter ECU 14 executes the three-phase short-circuit control. That is, under the control of the inverter ECU 14, the current value (Id, Iq) at the time of the three-phase short circuit is actively given to the motor 3 in advance on the software side, and then the three-phase short circuit is executed.

  The current command values (Id, Iq) given to the current control unit 13 by the inverter ECU 14 at this time are estimated based on a map corresponding to the rotation speed and temperature of the motor 3 and the current value of the motor 3 when the three-phase short circuit is caused. Therefore, even when the three-phase short circuit is actually executed, it is possible to shift to the three-phase short circuit state without generating an inrush current.

  Since the inrush current does not occur, the safety threshold of the same value as that of FIG. 4 indicated by the dotted line in FIG. 5 is not exceeded, and the three-phase short circuit is maintained while maintaining the safety measures against the DC short circuit in the inverter 10. The control can be reliably performed.

  And since it can prevent that the inrush current at the time of three-phase short circuit control arises, as shown with the dashed-dotted line of FIG. 5, the safety threshold value in the current control part 13 can be set low. Thereby, the current capacity of the inverter 10 can be reduced, and as a result, the inverter 10 can be downsized.

  In addition, the current value at the time of three-phase short-circuit is estimated according to the characteristics of the motor 3 and prior current control is performed, so that no inrush current at the time of three-phase short-circuit control can be generated regardless of the output of the motor 3. The output of the motor 3 can be increased without considering the increase of the inrush current accompanying the increase in the speed.

  From the above, according to the control device and the control method for the electric vehicle according to the present embodiment, the three-phase short-circuit control can be surely performed while maintaining the safety measures against the DC short-circuit or the like in the inverter 10. As a result, appropriate safety measures can be implemented, and the inverter 10 can be miniaturized and the motor output can be increased.

  Although the description about the embodiment of the control device for an electric vehicle according to the present invention is finished above, the embodiment is not limited to the above embodiment.

  Although the electric vehicle 1 of the above embodiment is a hybrid vehicle using the engine 2 and the motor 3 as drive sources, the present invention can be similarly applied to an electric vehicle and a fuel cell vehicle using only the motor as a drive source.

  In the above embodiment, the inverter 10 is controlled by Id and Iq using dq conversion. However, the inverter control method is not limited to this, and another control method may be used.

1 Vehicle 2 Engine 3 Motor (electric motor)
DESCRIPTION OF SYMBOLS 10 Inverter 11 Battery 12a-12f Switching element 13 Current control part 14 Inverter ECU (Abnormality detection means, prior current control means, three-phase short-circuit control means)

Claims (10)

An electric motor as a drive source of the vehicle;
A battery capable of storing electric power for driving the electric motor;
An inverter that performs direct current and alternating current conversion between the battery and the electric motor;
Three-phase short-circuit control means for controlling the inverter to a three-phase short-circuit state;
Pre-current control means for estimating a current value of the motor in the three-phase short-circuit state, and controlling the current of the motor for a predetermined time using the estimated current value as a target value before the start of the three-phase short-circuit control;
The control apparatus of the electric vehicle provided with.   2. The electric motor according to claim 1, wherein the preliminary current control unit estimates a current value of the electric motor when the three-phase short circuit is caused in accordance with a rotation speed and a temperature of the electric motor at the time of execution determination of the three-phase short circuit control. Vehicle control device.   The prior current control means has a map storing current values at the time of a three-phase short circuit according to the state of the motor, and estimates a current value of the motor when the three-phase short circuit is made based on the map. The control apparatus of the electric vehicle of Claim 1 or 2. An abnormality detecting means for detecting an abnormality relating to energization in a power supply circuit including the electric motor, the inverter, and the battery;
The prior current control means estimates the current value of the motor when a three-phase short circuit is caused in the state of the motor at the time of the abnormality when the abnormality is detected by the abnormality detection means, and the estimated The control apparatus for an electric vehicle according to any one of claims 1 to 3, wherein the current of the electric motor is controlled using a current value as a target value.   The said inverter has a safety mechanism which makes all the semiconductor elements of the said inverter OFF state when the electric current in the said inverter becomes more than a predetermined threshold value. Electric vehicle control device. An electric vehicle control method comprising: an electric motor that is a driving source of a vehicle; a battery that can store electric power for driving the electric motor; and an inverter that converts direct current and alternating current between the battery and the electric motor. Because
Three-phase short-circuit control execution determination step for determining whether or not it is necessary to perform three-phase short-circuit control in the inverter;
A pre-current control step of estimating a current value of the motor when the inverter is in a three-phase short circuit state, and controlling the current of the motor for a predetermined time with the estimated current value as a target value;
Three-phase short circuit control step for controlling the inverter to a three-phase short circuit state after current control of the electric motor in the prior current control step;
An electric vehicle control method comprising:   7. The electric motor according to claim 6, wherein in the preliminary current control step, the electric current value of the electric motor when the three-phase short circuit is short-circuited is estimated according to a rotation speed and a temperature of the electric motor at the time of execution determination of the three-phase short circuit control. Vehicle control method.   8. The current value of the electric motor when the three-phase short circuit is estimated is estimated based on a map in which the current value at the time of the three-phase short circuit corresponding to the state of the electric motor is stored in the preliminary current control step. Method for controlling an electric vehicle. An abnormality detection step of detecting an abnormality relating to energization in a power supply circuit including the electric motor, the inverter, and the battery;
When an abnormality is detected in the abnormality detection step, the current value of the motor when a three-phase short circuit is caused in the state of the motor at the time of the abnormality is estimated, and the estimated current value is used as a target value. The method for controlling an electric vehicle according to any one of claims 6 to 8, wherein the electric current of the electric motor is controlled.   The said inverter has a safety mechanism which makes all the semiconductor elements of the said inverter OFF state when the electric current in the said inverter becomes more than a predetermined threshold value. Control method of electric vehicle.

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