JP2015073408A - Power conversion system for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of brake torque caused by a motor generator, in a state where an inverter circuit stops.SOLUTION: A power conversion system for electric vehicle comprises: a booster circuit 3 which is connected to a DC power supply 2 and boosts a DC voltage; an inverter circuit 4 which converts the boosted voltage boosted by the booster circuit 3 to an AC voltage and outputs the AC voltage to a motor generator 5; and a control device 11 for controlling the booster circuit 3 and inverter circuit 4. The control device 11 comprises a booster control unit 111 for controlling the booster circuit 3, after the inverter circuit 4 stops, so that the boosted voltage Vboosted by the booster circuit 3 is equal to or larger than an induced voltage Vgenerated by the motor generator 5 rotating by receiving external force.

Description

  The present invention relates to a power conversion system for an electric vehicle used for an electric vehicle such as a hybrid vehicle or an electric vehicle.

  As shown in FIG. 3, in an electric vehicle (for example, a hybrid vehicle) having a power train configured such that the engine and the motor generator are not mechanically separated from each other, the inverter is stopped due to a failure such as a motor generator overheating failure. The system may stop.

  If the motor drive system is stopped and the vehicle operation is continued with the engine alone, the motor generator is rotated by the engine, an induced voltage is generated according to the rotation speed, and the main circuit is generated by the return diode of the inverter circuit. The rectified induced voltage is applied between the electrodes.

  Further, as shown in FIGS. 4 and 5, even in an electric vehicle (for example, a hybrid vehicle or an electric vehicle) having a power train configured such that the transmission and the motor generator are not mechanically separated from each other, a failure such as an overheat failure of the motor generator. In some cases, the inverter circuit stops and the motor drive system stops.

  When the electric vehicle is pulled by a towing vehicle or the like while the motor drive system is stopped, the motor generator is rotated by the transmission, an induced voltage corresponding to the number of rotations is generated, and the return diode of the inverter circuit Thus, the induced voltage rectified between the main circuit electrodes is applied.

  However, in the above situation, when the voltage value of the output stage of the booster circuit that boosts the DC voltage from the DC power source, that is, the output stage of the inverter circuit, is smaller than the rectified induced voltage (for example, the motor generator rotates at high speed). In this case, a regenerative current determined by the voltage difference and the resistance component of the closed circuit flows, and brake torque is applied by the motor generator.

  As shown in Patent Document 1, in a state where the motor drive system is operating, that is, in a state where the inverter circuit is operating, the boost voltage of the booster circuit is set to be higher than the drive voltage of the motor generator (motor required voltage). Although it is considered that the voltage is controlled to increase, the boosted voltage is not controlled when the inverter circuit is stopped.

JP 2006-320039 A

  Accordingly, the present invention has been made to solve the above-described problems, and a main intended problem is to suppress the generation of brake torque by the motor generator when the inverter circuit is stopped.

  That is, the electric power conversion system for an electric vehicle according to the present invention is connected to a DC power source, boosts a DC voltage from the DC power source, and converts the boosted voltage boosted by the boost circuit into an AC voltage, An inverter circuit that outputs to a motor generator; and a booster circuit and a control device that controls the inverter circuit, wherein the control device controls the booster circuit after the inverter circuit is stopped, and the boosted voltage by the booster circuit Is provided with a step-up control unit that makes the motor generator more than an induced voltage generated when the motor generator receives an external force and rotates.

  The control device for an electric vehicle power conversion system according to the present invention is connected to a DC power source, boosts a DC voltage from the DC power source, and converts the boosted voltage boosted by the boost circuit to an AC voltage. A control device for an electric vehicle power conversion system comprising an inverter circuit for conversion and output to a motor generator, wherein after the inverter circuit is stopped, the booster circuit is controlled, and the boosted voltage by the booster circuit is The motor generator includes a step-up control unit that makes the induced voltage equal to or higher than that generated when the motor generator receives an external force and rotates.

Furthermore, a control program for an electric vehicle power conversion system according to the present invention is connected to a DC power supply, boosts a DC voltage from the DC power supply, and converts the boosted voltage boosted by the booster circuit to an AC voltage. A control program for an electric vehicle power conversion system comprising an inverter circuit for conversion and output to a motor generator, wherein after the inverter circuit is stopped, the booster circuit is controlled, and the boosted voltage by the booster circuit is The computer is provided with a function as a step-up control unit that makes the voltage more than an induced voltage generated when the motor generator receives an external force and rotates.
Here, the induced voltage generated when the motor generator is rotated by receiving an external force is a DC induced voltage generated by rectifying the AC induced voltage generated by the motor generator by the return diode bridge of the inverter circuit.

  According to the electric vehicle power conversion system configured as described above, its control device, or its control program, when the inverter circuit is stopped, the boosted voltage by the booster circuit is equal to or higher than the induced voltage generated by the motor generator. The regenerative current from can be reduced to zero, and the generation of brake torque by the motor generator can be suppressed. As a result, when the vehicle is driven by the engine alone or when it is towed by a towing vehicle, unnecessary energy consumption for canceling the brake torque by the motor generator can be avoided, and a decrease in vehicle running performance can be prevented.

It is desirable that the boost control unit sets the boosted voltage by the booster circuit to be equal to or higher than the induced voltage at the maximum motor generator rotational speed measured in advance in a stopped state of the inverter circuit. In particular, it is desirable that the boost control unit sets the boost voltage by the boost circuit to a constant value equal to or higher than the induced voltage at the maximum rotation speed.
In this case, it can be mounted on the control device relatively easily. In addition, the control is facilitated by setting the boosted voltage to a constant value equal to or higher than the induced voltage at the maximum rotation speed, but the switching by the relatively large on-duty value of the lower arm made of the power semiconductor constituting the booster circuit is It is continued during the control application time, and loss generation concentrates on the lower arm.

If the boosted voltage is set to a constant value equal to or higher than the induced voltage at the maximum rotational speed as described above, the heat burden on the lower arm is concentrated. Therefore, the rotation speed of the motor generator is set so that the boosting voltage by the boosting circuit is equal to or higher than the induced voltage for each rotation speed of the motor generator measured in advance when the inverter circuit is stopped. It is desirable to set every time.
In this case, since the voltage is boosted at a necessary timing by a necessary amount according to the induced voltage generated for each rotation speed of the motor generator, the concentration of the heat burden on the lower arm can be reduced.

  As a specific embodiment for controlling the boosted voltage for each rotation speed of the motor generator, the control device uses an induced voltage for each rotation speed of the motor generator in the stop state of the inverter circuit measured in advance. And a setting voltage data storage unit for storing a set boost voltage-rotation number data indicating a set boost voltage set for each rotation speed of the motor generator, wherein the boost control unit is configured to stop the inverter circuit after the inverter circuit is stopped. Controlling the booster circuit so as to obtain a set boost voltage obtained from a rotation speed data indicating the rotation speed of the motor generator and a set boost voltage-rotation speed data stored in the setting voltage data storage unit. desirable.

  According to the present invention configured as described above, since the boosted voltage generated by the booster circuit is equal to or higher than the induced voltage generated by the motor generator when the inverter circuit is stopped, the regenerative current from the motor generator can be reduced to zero. The generation of brake torque by the motor generator can be suppressed.

The figure which shows the circuit structure of the electric power conversion system for electric vehicles in this embodiment. The schematic diagram which shows the relational expression of the setting boost voltage-rotation speed in the embodiment. The figure which shows the powertrain example of the structure where the conventional engine and motor generator are not isolate | separated mechanically. The figure (hybrid vehicle) which shows the example of the power train of the composition where the conventional transmission and motor generator are not separated mechanically. The figure (electric vehicle) which shows the example of the power train of the structure where the conventional transmission and motor generator are not isolate | separated mechanically. The figure which mainly shows the circuit structure which connected the several booster circuit in deformation | transformation embodiment in parallel.

  Hereinafter, an embodiment of a power conversion system for an electric vehicle according to the present invention will be described with reference to the drawings.

  An electric vehicle power conversion system 100 according to the present embodiment is mounted on an electric vehicle such as a hybrid vehicle or an electric vehicle, and causes the motor generator 5 to perform a power running operation or a regenerative operation. In addition, as shown in FIGS. 3 to 5, the electric vehicle according to the present embodiment has an electric vehicle or a transmission and a motor generator having a power train configured such that the engine and the motor generator are not mechanically separated. This is an electric vehicle having a power train that is not separated.

  As shown in FIG. 1, this electric vehicle power conversion system 100 boosts a DC voltage from a DC main power supply 2 by a booster circuit 3, converts it to a three-phase AC voltage by an inverter circuit 4, and outputs it to a motor generator 5. And a regenerative operation of supplying regenerative power from the motor generator 5 to the DC main power source 2, the vehicle auxiliary device 6 and the DC auxiliary power source 7 through the inverter circuit 4 and the booster circuit 3. .

  Specifically, the electric vehicle power conversion system 100 includes a DC main power supply 2 (for example, a 48V lithium ion battery) and an electric circuit switch 8 (DC contactor) that opens and closes an electric circuit connected to the output terminal of the DC main power supply 2. And a first smoothing capacitor 9 (DC link capacitor) provided downstream of the electric circuit switch 8 and the first smoothing capacitor 9 to connect each auxiliary machine (for example, electric power steering, air conditioner) , ECU, etc.) 6 and a DC auxiliary power source (for example, 12V / 24V battery) 7 are connected in parallel with the auxiliary power system S1 via the first smoothing capacitor 9 and the auxiliary power system S1 that supplies power. The motor generator 5 is provided with a motor drive power system S2 that performs a power running operation or a regenerative operation of the motor generator 5. Note that the first smoothing capacitor 9 is included in the motor drive power system S2.

  The auxiliary power system S1 includes a DC / DC converter 10, and each auxiliary machine 6 and DC auxiliary power source 7 of the vehicle are connected in parallel to the output stage of the DC / DC converter 10. .

  The motor drive power system S2 includes a booster circuit 3 that performs voltage conversion of a DC voltage from the DC main power supply 2, and an inverter circuit that converts the DC voltage output from the booster circuit 3 into an AC voltage and outputs the AC voltage to the motor generator 5. 4 is provided.

  The booster circuit 3 includes power semiconductors 31 a and 31 b such as IGBTs and MOSFETs, a reactor 32, and a second smoothing capacitor 33. Specifically, the booster circuit 3 has an upper arm 31a and a lower arm 31b made of a directly connected power semiconductor, and a positive input of the inverter circuit 4 is input to a semiconductor terminal (for example, a collector terminal or a drain terminal) of the upper arm 31a. A terminal is connected, and a negative terminal of the DC main power supply 2 is connected to a semiconductor terminal (for example, an emitter terminal or a source terminal) of the lower arm 31b. A second smoothing capacitor 33 is connected in parallel to the upper arm 31a and the lower arm 31b between the semiconductor terminal of the upper arm 31a and the semiconductor terminal of the lower arm 31b, that is, at the output stage of the booster circuit 3. Yes. Furthermore, one terminal of the reactor 32 is connected between the other terminal (emitter terminal or source terminal) of the upper arm 31a and the other terminal (collector terminal or drain terminal) of the lower arm 31b (series connection point). In addition, the other terminal of the reactor 32 is connected to the positive terminal of the DC main power supply 2. It should be noted that the upper arm 31a and the lower arm 31b of the booster circuit 3 may be configured by connecting freewheeling diodes in antiparallel.

  The booster circuit 3 configured as described above is provided with a drive circuit 34 for driving the upper arm 31a and the lower arm 31b. The drive circuit 34 alternately switches the upper arm 31a and the lower arm 31b with a predetermined duty ratio, thereby charging and discharging the reactor 32 to supply power in the power running direction (step-up) and the regeneration direction (step-down). Carry. Note that a drive command signal (control signal) is input to the drive circuit 34 by a booster circuit control unit 111 of the control device 11 described later.

  Further, the second smoothing capacitor 33 provided in the booster circuit 3 is configured to function as a smoothing capacitor in the input stage of the inverter circuit 4. That is, the booster circuit 3 and the inverter circuit 4 share the second smoothing capacitor 33.

  The inverter circuit 4 includes a three-phase bridge circuit (not shown) configured by connecting in parallel three switching circuits made of power semiconductors such as IGBTs and MOSFETs, and power semiconductors (upper arm and lower arm) of the respective switching circuits. It is comprised by the drive circuit (not shown) for driving. A drive command signal (control signal) is input to the drive circuit by an inverter circuit control unit 112 of the control device 11 described later.

  The auxiliary power system S1 and the motor drive power system S2 configured as described above are controlled by the control device 11. This control device 11 performs optimal operation of the booster circuit 3 and the inverter circuit 4 on the basis of an operation command required from a general controller (for example, a host ECU) in order to perform power running / regenerative power control necessary for driving the electric vehicle. Each power semiconductor drive command signal is generated while the power is linked, and the power semiconductor drive command signal is given to each drive circuit as a switching command. Thus, the electric vehicle power conversion system 100 boosts the DC voltage from the DC main power supply 2 by the booster circuit 3, converts the DC voltage to the AC voltage by the inverter circuit 4, and outputs the AC voltage to the motor generator 5, and the motor generator. A regenerative operation is performed in which the regenerative power from 5 is supplied to the DC main power source 2, the vehicle auxiliary machine 6 and the DC auxiliary power source 7 via the inverter circuit 4 and the booster circuit 3. The control device 11 can be configured to be physically separated corresponding to each of the booster circuit 3 and the inverter circuit 4. However, the control device 11 may be shared and integrated in order to reduce the number of parts. Is desirable.

The control device 11 of this embodiment controls the booster circuit 3 immediately after the stop of the inverter circuit 4 due to the failure detection of the motor drive system, and the motor generator 5 outputs the boosted voltage _Vboost by the booster circuit 3 to the external force. And has a boosting control function that makes the induced voltage V _induced or more generated by rotating by receiving. Here, the induced voltage V _induced is a DC induced voltage generated by rectification by the freewheeling diode bridge of the inverter circuit 4.

  Specifically, the control device 11 is a dedicated or general-purpose computer circuit including a CPU, a memory, an input / output interface, an AD converter, and the like, and the boost circuit control unit 111 and the inverter described above according to a control program stored in the memory. In addition to the circuit control unit 112, functions such as a boost control unit 113, a setting voltage data storage unit 114, and a rotation speed detection unit 115 are exhibited.

Immediately after the inverter circuit 4 is stopped, the boost control unit 113 controls the booster circuit 3 so that the boosted voltage _Vboost generated by the booster circuit 3 is equal to or higher than the induced voltage V _induced generated by the motor generator 5 receiving external force and rotating. It is what. The boost control unit 113 acquires a system failure detection signal from the system failure detection circuit constituting the inverter circuit control unit 112, sets the set boost voltage V _{boost_set} to be output by the boost circuit 3, and sets the set boost voltage The booster circuit 3 is controlled so as to be V _{boost_set} . Here, the step-up control unit 113 is provided between the step-up circuit 3 and the inverter circuit 4, and acquires a voltage detection signal from the voltage detection unit 12 that detects the voltage across the smoothing capacitor 33 (step-up voltage V _boost ). The detected inter-terminal voltage (boosted voltage V _boost ) is controlled to be the set boosted voltage V _{boost_set} . Specific control contents will be described later.

The setting voltage data storage unit 114 stores setting voltage data for setting the set boost voltage _{Vboost_set} . The setting voltage data of the present embodiment is set voltage V _boost determined based on the induced voltage V _boost at each rotation speed in the motor generator 5 in the rotating state, which is measured in advance when the inverter circuit 4 is stopped. _This is data indicating _{boost_set} . More specifically, the set boost voltage V _{boost_set} is set as a value larger than the induced voltage V _boost measured at each rotation speed of the motor generator 5, and the setting voltage data is the rotation of the motor generator 5. This is set boost voltage-rotational speed data indicating the relationship between the number and the set boost voltage V _{boost_set} (see FIG. 2).

  The rotational speed detection unit 115 calculates the rotational speed from the rotor position detection signal acquired from the motor generator 5.

  Then, using these setting voltage data and rotation speed data, the boost control unit 113 controls the boost circuit 3 as follows.

  First, when the system failure detection circuit of the inverter circuit control unit 112 detects a failure such as an overheat failure of the motor generator 5 as a system failure, the inverter circuit control unit 112 turns off the upper and lower arms of all three phases to the inverter circuit 4. An inverter stop command (OFF signal) is output. At this time, the boost control unit 113 acquires a system failure detection signal from the system failure detection circuit of the inverter circuit control unit 112.

The boost control unit 113 that has acquired the system failure detection signal acquires the rotational speed data of the motor generator 5 from the rotational speed detection unit 115 and also acquires the set boosted voltage-rotational speed data from the setting voltage data storage unit 114. Then, a set boost voltage V _{boost_set} corresponding to the actual rotational speed of the motor generator 5 is set from these data. Then, the boost control unit 113 uses the boost circuit control unit 111 based on the calculated installation boost voltage V _{boost_set} and the inter-terminal voltage (boost voltage V _boost ) obtained by the voltage detection unit 12. Control is performed so as to output the set boost voltage V _{boost_set} .

According to the electric vehicle power conversion system 100 configured as described above, when the inverter circuit 4 is stopped, the boosted voltage _Vboost generated by the booster circuit 3 is equal to or higher than the induced voltage V _induced generated by the motor generator 5. The regenerative current from 5 can be made zero, and the generation of brake torque by the motor generator 5 can be suppressed. Thereby, when the vehicle is driven by the engine alone or when it is towed by a towing vehicle, unnecessary energy consumption for canceling the brake torque by the motor generator 5 can be avoided, and a decrease in vehicle running performance can be prevented.

The present invention is not limited to the above embodiment.
For example, the boost control unit 113 of the embodiment is configured to set the set boost voltage V _{boost_set} according to the rotation speed of the motor generator 5 using the set boost voltage-rotation speed data. The boosted voltage V _{boost_set} may be _{equal to} or higher than the induced voltage V _{induced_max} at the maximum rotation speed of the motor generator 5 measured in advance when the inverter circuit 4 is stopped. Specifically, the boost control unit 113 may set the set boost voltage V _{boost_set} to a constant value _{equal to} or higher than the induced voltage V _{induced_max} at the maximum rotation speed. In this case, the setting voltage data storage unit 114 stores voltage data indicating a constant value equal to or higher than the induced voltage V _{induced_max} at the maximum rotation speed.

Further, as the setting voltage data stored in the setting voltage data storage unit 114, voltage data indicating the induced voltage V _induced for each actually measured rotation speed or the induced voltage V _{induced_max} at the actually measured maximum rotation speed is used. The boost control unit 113 may set the set boost voltage V _{boost_set} by performing a predetermined calculation on the voltage data.

  Furthermore, as shown in FIG. 6, a plurality of booster circuits 3 are connected in parallel to the DC main power supply 2, and a drive circuit 34 is provided independently for each of the booster circuits 3 connected in parallel. When at least one booster circuit 3 fails, the control circuit 11 that outputs a control signal to the drive circuit 34 stops the operation of the failed booster circuit 3, and power according to the number of remaining normal booster circuits. A control value may be set, and the remaining normal booster circuit 3 and inverter circuit 4 may be controlled based on the power control value.

  In this case, since a plurality of booster circuits 3 are provided in parallel, the redundancy of the power conversion system 100 can be improved. At this time, by providing a plurality of booster circuits 3 in parallel in a configuration in which the alternator is omitted, it is possible to ensure power supply to the DC main power supply 2, the vehicle auxiliary machine 6 and the DC auxiliary power supply 7. Further, by providing a plurality of booster circuits 3 in parallel, the current can be distributed to each booster circuit 3, and it is possible to improve the performance of the booster circuit 3, such as high efficiency, miniaturization of parts, and long life. it can. Further, when at least one booster circuit 3 fails, a power limit value that can be processed by the number of remaining normal booster circuits is set, and the remaining normal booster circuit 3 and inverter circuit 4 are controlled by the power limit value. Therefore, even after some of the booster circuits 3 fail, the motor generator is continuously operated in a power-limited manner so that the regenerative power to the DC main power source 2, the vehicle auxiliary device 6 and the DC auxiliary power source 7 is reduced. Charging becomes possible. As a result, a limp home mode system can be constructed, and the vehicle occupant can be safely evacuated by driving or the vehicle can be moved to a repair shop.

Further, smoothing capacitors 33 may be provided at the output stages of the booster circuits 3 connected in parallel, and each of the smoothing capacitors 33 may function as a smoothing capacitor at the input stage of the inverter circuit 4. In this case, since the smoothing capacitors 33 are provided at the output stages of the booster circuits 3 connected in parallel, the ripple current in charging / discharging of the smoothing capacitors 33 when exchanging power with the inverter circuit 4 is reduced by current distribution. Therefore, the smoothing capacitor 33 can be reduced in size and loss compared to the conventional case, and the performance can be improved. Further, it is possible to reduce the ripple of the boosted voltage _{V boost} from a parallel connection of a plurality of boosting circuit 3, a step-up control to the boosted voltage _{V boost} the induced voltage _{V induced} or can be facilitated.

  In addition, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

100: Electric vehicle power conversion system 2: DC main power supply (DC power supply)
DESCRIPTION OF SYMBOLS 3 ... Boosting circuit 4 ... Inverter circuit 5 ... Motor generator 11 ... Control circuit 113 ... Boosting control part 114 ... Setting voltage data storage part 115 ... Rotation speed detection part

Claims (7)

A booster circuit connected to a DC power supply and boosting a DC voltage from the DC power supply;
An inverter circuit that converts the boosted voltage boosted by the booster circuit to an AC voltage and outputs the AC voltage to the motor generator;
A control device for controlling the booster circuit and the inverter circuit;
The control device includes a boost control unit that controls the booster circuit after the inverter circuit is stopped so that a boosted voltage by the booster circuit is equal to or higher than an induced voltage generated when the motor generator receives an external force and rotates. Electric vehicle power conversion system.   The boost control unit sets the boosted voltage by the booster circuit for each rotation speed of the motor generator so as to be equal to or higher than an induced voltage for each rotation speed of the motor generator measured in advance when the inverter circuit is stopped. The electric power conversion system for an electric vehicle according to claim 1. A set boost voltage that indicates a set boost voltage set for each rotation speed of the motor generator using the induced voltage for each rotation speed of the motor generator measured in advance when the inverter circuit is stopped. A voltage data storage unit for setting for storing the rotation speed data;
The set boost voltage obtained from the rotation speed data indicating the rotation speed of the motor generator after the inverter circuit is stopped and the set boost voltage-rotation speed data stored in the setting voltage data storage section. The electric power conversion system for an electric vehicle according to claim 2, wherein the booster circuit is controlled so that   2. The electric power conversion system for an electric vehicle according to claim 1, wherein the boosting control unit sets the boosted voltage by the booster circuit to be equal to or higher than an induced voltage at the maximum motor generator rotational speed measured in advance when the inverter circuit is stopped.   5. The electric power conversion system for an electric vehicle according to claim 4, wherein the boost control unit sets a boosted voltage by the booster circuit to a constant value equal to or higher than an induced voltage at the maximum rotation speed. An electric vehicle comprising: a booster circuit connected to a DC power supply and boosting a DC voltage from the DC power supply; and an inverter circuit that converts the boosted voltage boosted by the booster circuit into an AC voltage and outputs the AC voltage to a motor generator A control device for a power conversion system,
Electric vehicle power provided with a boost control unit that controls the booster circuit after the inverter circuit is stopped so that the boosted voltage by the booster circuit is equal to or higher than the induced voltage generated when the motor generator receives external force and rotates. Control device for the conversion system. An electric vehicle comprising: a booster circuit connected to a DC power supply and boosting a DC voltage from the DC power supply; and an inverter circuit that converts the boosted voltage boosted by the booster circuit into an AC voltage and outputs the AC voltage to a motor generator A control program for a power conversion system,
After stopping the inverter circuit, the booster control circuit controls the booster circuit so that the boosted voltage by the booster circuit is equal to or higher than the induced voltage generated by the motor generator receiving external force and rotating. A control program for a power conversion system for an electric vehicle, comprising: