JP7377650B2 - power converter - Google Patents

Description

The present invention relates to a power conversion device, and particularly to a power conversion device for driving an electric vehicle.

Electric vehicles such as hybrid vehicles include an inverter device (power conversion device) for supplying alternating current power to a drive motor. Such power converters operate on power supplied from a high-voltage power source (battery) of several tens to hundreds of volts, while the control circuit for controlling the inverter operates on relatively high voltage power of about 12 volts. Operated by low voltage power supply.

For example, Patent Document 1 describes a power conversion device that has redundant power supply paths such as a power source and a power generation circuit, and performs a protective operation when an abnormality occurs in the system. The power conversion device according to Patent Document 1 includes a backup power source that generates a low voltage from a high voltage power source and supplies power to a protective operation circuit in order to perform a protective operation of the device even when a low voltage power source is lost. An example of the protective operation by the protective operation circuit is control to short-circuit three phases of either the upper or lower arm of the inverter circuit so that the voltage on the high-voltage power supply side does not exceed a predetermined threshold (for example, 60 V).

International Publication No. 2018/030381 pamphlet

The voltage of the high voltage power supply is monitored by an HV sensor circuit. A power supply circuit is provided that supplies power from a low voltage power supply to the HV sensor circuit so that a state where the high voltage power supply is 0V can also be detected. Furthermore, the power supply circuit can also be powered by a backup power source that generates low-voltage power from the high-voltage power source so that the device can be protected even when the low-voltage power source is lost.

Here, when the motor rotates due to the vehicle being towed when the low-voltage power supply is lost, the voltage on the high-voltage power supply side increases due to the motor electromotive force. For safety reasons, it is necessary to perform a protective operation by a protective operation circuit so that the voltage on the high-voltage power supply side does not exceed a predetermined threshold value when an abnormality occurs. That is, even when the low-voltage power supply is lost, the protection operation circuit is required to be supplied with the power necessary for driving from the backup power supply, and the protection operation according to the voltage on the high-voltage power supply side is reliably executed.

However, during low-speed traction, the voltage increase caused by regeneration is low, and it may not be possible to stably supply power to the backup power source. Therefore, the HV sensor circuit whose supply voltage is unstable may malfunction. Malfunction of the HV sensor circuit may cause, for example, unintentional execution of three-phase short circuit control, which is one of the protection operations, resulting in a high voltage exceeding a predetermined threshold.

The main purpose of the present invention is to prevent unintentional HV sensor malfunction even in situations where the high voltage value is low, such as during low-speed towing.

The power conversion device according to the present invention includes: an inverter circuit that converts DC power from a high voltage power source into AC power and outputs the converted AC power to a motor; a drive circuit that controls driving of the inverter circuit; A smoothing capacitor smoothes a high voltage applied to the circuit, and a first power supply voltage and a second power supply voltage are obtained by converting the DC power from the high voltage power supply or the power accumulated in the smoothing capacitor. a booster circuit that boosts the first power supply voltage supplied from the backup power supply circuit or the voltage supplied from the low voltage power supply to supply a third power supply voltage; and the backup power supply circuit. a power supply switching circuit that selectively outputs the second power supply voltage supplied from the booster circuit or the third power supply voltage supplied from the booster circuit; a voltage sensor that operates using power from the third power supply voltage and detects a high voltage applied to the inverter circuit; and a control circuit that controls the drive circuit ; If the high voltage power supply is not supplied and the connection between the high voltage power supply and the inverter circuit is cut off, the backup power supply circuit uses the power accumulated in the smoothing capacitor to supply power to the first power supply. voltage and the second power supply voltage that is higher than the first power supply voltage, the voltage sensor operates using power from the second power supply voltage, and the voltage sensor operates by using the power from the second power supply voltage, and the voltage sensor operates from the motor to the inverter circuit. detects an induced voltage applied to the high voltage as the high voltage, the drive circuit starts activation when the first power supply voltage exceeds a predetermined first voltage value, and the control circuit detects that the drive circuit If the inverter has already been activated and the induced voltage detected by the voltage sensor is equal to or higher than a predetermined value, the drive circuit is controlled to perform three-phase short-circuit control of the inverter circuit.

According to the present invention, even in a situation where the high voltage value is low, it is possible to prevent malfunction of safety operation due to malfunction of the HV sensor.

FIG. 2 is a configuration diagram of a power conversion device. FIG. 7 is a diagram showing a power supply line in a normal state in a power supply configuration according to a comparative example. FIG. 7 is a diagram showing a power supply line when low voltage power is lost in a power supply configuration according to a comparative example. It is a time chart during low-speed towing in a power supply configuration according to a comparative example. 1 is a diagram showing a power supply configuration according to the present invention. FIG. 3 is a diagram showing a power supply line in a normal state in the power supply configuration according to the present invention. FIG. 3 is a diagram showing a power supply line when a low voltage power supply is lost in the power supply configuration according to the present invention. It is a time chart at the time of low-speed traction in the power supply configuration according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a power conversion device according to the present invention will be described with reference to the drawings. In each figure, the same elements are denoted by the same reference numerals, and overlapping explanations will be omitted.

FIG. 1 shows the configuration of a motor drive power conversion device 200, which is an example of a power conversion device. A high voltage battery 901 is connected to the input side of the power conversion device 200, and a motor 900 is connected to the output side. A contactor 902 is provided between high voltage battery 901 and power converter 200.

The power conversion device 200 includes a controller 100a, a driver circuit 100b, a semiconductor device 300 for power conversion, and a voltage smoothing capacitor 500. A higher-level controller (not shown) gives commands for driving the motor, such as torque and rotation commands, to the controller 100a. The controller 100a provides a PWM signal according to the command to the driver circuit 100b. The driver circuit 100b controls the switching of the semiconductor device 300 for power conversion according to the PWM signal, and converts the direct current voltage (DC voltage) from the high voltage battery 901 into an alternating current voltage (AC voltage) for driving the motor 900. It has the ability to convert. The voltage smoothing capacitor 500 smoothes applied voltage that varies during power conversion.

The alternating current output from the semiconductor device 300 to the motor 900 is detected by the current sensor 20. Power conversion device 200 performs current feedback control based on the current value detected by current sensor 20, and controls the torque of motor 900.

Furthermore, a GD power supply 110 is provided that generates power for driving the driver circuit 100b. The GD power supply 110 generates power using the voltage (12V) supplied from the low voltage battery 10 via the controller 100a. Further, a redundant power supply 120 is provided in case the supply from the low voltage battery 10 is stopped. The redundant power supply 120 converts the voltage supplied from the high voltage battery 901 and supplies power to the controller 100a.

The discharge circuit 130 is a circuit for discharging the high voltage battery 901 in the device using the discharge resistor 131 when the power conversion device 200 is stopped, and lowering the voltage to a safe value. HV sensor circuit 140 is connected to high voltage battery 901 and detects voltage. The detected information is transmitted to the controller 100a.

Below, before showing the configuration of the power supply, which is a feature of the present invention, a power supply configuration as a comparative example will be explained.

FIG. 2 shows a power supply system as a comparative example. The gate driver circuit that drives the switching elements of the semiconductor device 300 in FIG. 1 is driven by power supplied from a 12V low-voltage battery power source. By outputting a drive signal based on PWM control to the inverter circuit, the gate driver circuit converts DC power from the high-voltage battery power supply into AC power and supplies it to the motor, or vice versa, converts the DC power from the high-voltage battery power supply into AC power and supplies it to the motor, or conversely, converts the regenerative power based on motor rotation to the high-voltage battery. or charge it to a power source. Furthermore, if the contactor 902 is turned off while the regenerated energy is large, three-phase short-circuit control is performed to turn on the upper arm or lower arm of the inverter circuit in all phases to protect the smoothing capacitor from excessive voltage being applied. controlled by a safety control circuit.

Further, the discharge circuit 130 is driven by power generated by an active discharge power source. The active discharge power supply boosts the voltage supplied from the low voltage battery power supply and supplies power for driving the discharge circuit in the high voltage circuit section. Note that although the active discharge power supply in this embodiment is a power supply circuit that converts low voltage to high voltage using a flyback method, the method of the power supply circuit is not particularly limited to this. Further, the discharge operation by the discharge circuit is controlled based on the HV voltage detected by the HV sensor circuit 140. The driving power for the HV sensor circuit is also supplied by the active discharge power supply. The HV voltage detection value detected by the HV sensor circuit is output to the safety control circuit via the isolator. The safety control circuit performs calculations based on the detected value of the HV sensor circuit, and outputs a control signal to the gate driver circuit or the discharge circuit.

For example, if the HV voltage value detected by the HV sensor circuit is equal to or higher than a predetermined threshold, a signal instructing the discharge circuit to discharge is output, and if the HV voltage value falls below the predetermined threshold, the discharge is stopped. You can instruct it to stop. Alternatively, a three-phase short-circuit instruction is issued to the gate driver circuit on the upper arm side or the lower arm side, and a protection operation of the power conversion device is executed. Note that the safety control circuit arranged in the circuit on the low voltage side is driven by the power supplied from the low voltage battery power source, similarly to the gate driver circuit.

Here, if the power supply from the 12V low-voltage battery power source is lost, the contactor 902 is opened, a protective operation is performed to disconnect the high-voltage battery power source and the power converter, and then active discharge is immediately performed. Active discharge is to discharge the high voltage stored in the smoothing capacitor 500 by controlling the discharge circuit 130 and causing current to flow through the discharge resistor 131. For safety reasons, the discharge must be carried out such that it is below 60V within 5 seconds, for example.

In order to reliably drive the discharge circuit 130 and perform the protective operation even when the low-voltage battery power supply is lost, the active discharge power supply is configured to also be supplied with power from the redundant power supply 120. The redundant power supply 120 supplies power on the LV side by stepping down the voltage from the high-voltage battery 901 or the voltage remaining in the smoothing capacitor 500 when the contactor 902 is open. Note that the redundant power supply in this embodiment is configured by a flyback type power supply circuit. A flyback power supply circuit uses a control IC to turn on and off a switching element connected in series to the primary winding of an isolated transformer, thereby controlling the current flowing through the transformer and supplying power to the secondary circuit of the transformer. Communicate. Further, the transformer of the redundant power supply includes a tertiary winding, and after the redundant power supply starts up, it supplies power to the power supply circuit itself, and the output is shown as VCC_FB. The power supply system when low voltage battery power is lost is shown in FIG.

Here, consider a case where the vehicle is towed at low speed in a state where there is no power supply from the low voltage battery power source and the high voltage battery power source 901 and inverter 200 are not connected because the contactor 902 is open. When traction starts, an induced voltage is generated due to the rotation of the motor, and the voltage of the smoothing capacitor 500 gradually increases from 0V. Note that the motor may rotate and generate an induced voltage not only when the vehicle is being towed, but also when the vehicle is coasting or when going downhill. As described above, when the low-voltage battery power supply fails, active discharge is performed by power supply from the redundant power supply, but when the voltage of the smoothing capacitor 500 is still low, the redundant power supply 120 cannot supply stable power. I can't. If a sufficient voltage cannot be supplied to the active discharge power source, the power necessary to drive the HV sensor circuit will not be supplied, so the operation of the HV sensor circuit may become unstable and malfunction. If the HV sensor circuit, which is a criterion for safe operation, malfunctions, the gate drive circuit may malfunction below the voltage at which a three-phase short circuit should be performed, resulting in an unintended voltage increase.

This will be explained in detail using FIG. 4. FIG. 4 shows a time chart of each power supply voltage during low-speed traction when the supply of low-voltage battery power is stopped and the contactor is in an open state.

When the speed of traction increases from a stopped state, the voltage (HVDC) of the voltage smoothing capacitor of the inverter increases due to the electromotive force of the motor in accordance with the rotational speed (speed) of the motor. As described above, the redundant power supply 120 generates (converts) the LV voltage based on HVDC. When the HVDC exceeds 10V, voltage is input to the control IC power supply of the redundant power supply 120. When the input voltage of the control IC of the redundant power supply 120 exceeds 5V, the redundant power supply 120 starts operating and starts outputting the voltage on the LV side. In the process of rising the output voltage of the redundant power supply 120, the GD power supply and the HV sensor voltage rise.

The power input to the HV sensor is supplied from the active discharge power supply shown in Fig. 3, but the active discharge power supply starts when the input voltage, that is, the output voltage of the redundant power supply exceeds 5V, and increases the voltage. Start outputting. Note that the hatched area in FIG. 4 indicates an area where the operation is unstable due to low voltage. The GD power supply starts up when the output voltage of the redundant power supply exceeds 4V.

Power to the HV sensor circuit begins to be supplied from time t4 in FIG. 4, and until time t5 when a voltage that allows stable operation is obtained, operation is unstable due to insufficient power supply voltage. It becomes. Therefore, during this period, an erroneous judgment may occur that a threshold value for a three-phase short circuit has been exceeded (for example, the safety control circuit is configured to control the gate driver circuit so that a three-phase short circuit is performed when the HVDC voltage exceeds 39 V). ). If the voltage input to the GD power supply has risen to a certain level at the time an erroneous determination occurs, the gate driver circuit will drive the switching elements of the upper arm or lower arm of the inverter circuit to perform a three-phase short circuit. A signal is output. As a result, the capacitor voltage (HVDC) may jump up instantaneously, and there is a possibility that the capacitor voltage may exceed 60V.

In the present invention, as a countermeasure to the above problem, a power supply configuration shown in FIG. 5 is adopted. A change from the comparative example power supply configuration shown in Figure 2 is that the HV sensor circuit operates not only with the active discharge power supply from the LV side, but also with the power supply from the tertiary winding of the transformer of the redundant power supply. I made it possible to do this. Here, the input stage of the HV sensor circuit is connected via a diode so that power can be supplied from either the active discharge power source or the redundant power source.

When the low voltage battery power supply is operating normally, power is supplied to the HV sensor circuit via the active discharge power supply, similar to FIG. 2 (see FIG. 6). In addition, even if the low-voltage battery power supply is lost, if the HVDC is sufficiently stable (HVDC>40V), the active discharge power supply can be activated by power supply from the redundant power supply, as in Figure 3. (See FIG. 7).

If the vehicle is towed at low speed with no power supplied from the low-voltage battery power supply and the contactor 902 is open, the redundant power supply that is the active discharge power supply and the power supply to the gate drive circuit, as explained in FIG. The output voltage does not stabilize until HVDC reaches about 30V. Here, in the present invention, focusing on the fact that the output voltage of the tertiary winding of the redundant power supply reaches 5V at time t3 and enters a stable region relatively early, the output power of the tertiary winding of the redundant power supply is applied to the HV sensor circuit. The configuration is such that the input is input to the power supply of the A time chart in this case will be explained using FIG. 8.

Similar to FIG. 4, HVDC gradually increases from 0V due to the traction operation. Then, when the input voltage to the control IC power supply of the redundant power supply exceeds 5V, voltage begins to be output from the tertiary winding of the redundant power supply. This tertiary winding output voltage is input to the HV sensor circuit starting from the power supply switching circuit and the diode shown in FIG. While the power supply voltage input to the HV sensor is still low (in the region below 5V), the operation of the HV sensor circuit is unstable, so the HVDC voltage value may be incorrectly detected and the three-phase short circuit threshold may be exceeded. It may be judged. However, at this point, sufficient voltage is not yet supplied from the redundant power supply, and the GD power supply has not started up. Therefore, even if the HV sensor circuit incorrectly detects that the three-phase short circuit threshold has been exceeded, the three-phase short circuit control by the gate driver circuit is not executed.

After time t3, sufficient power is supplied to the HV sensor power supply for operation, and the sensor enters a stable operation region. Since the GD power source starts rising after the operation of the HV sensor becomes stable, according to the present invention, it is possible to prevent malfunctions due to three-phase short circuits. As a result, three-phase short circuits due to malfunctions do not occur, and safe operation before 60V functions normally.

Note that after time t5, the voltage supplied to the GD power supply is also stabilized. In other words, even if the low-voltage battery power source is lost, the system can successfully transition to the backup state using the redundant power source. When the motor rotation speed continues to rise and the HVDC reaches around 40V, the HV sensor power supply normally detects that it is at the three-phase short circuit threshold, and the gate driver circuit executes the three-phase short circuit control. Excessive rise in HVDC can be prevented.

As described above, the power conversion device according to the present invention operates with the inverter circuit 300 that converts DC power from the high voltage battery power source 901 into AC power, and the power supplied from the low voltage battery power source 10. A gate driver circuit that controls driving, a redundant power supply 120 that can convert DC power from a high-voltage battery power supply 901 and supply it to the gate driver circuit, and an HV sensor circuit that detects the high voltage applied to the inverter circuit 300. 140, when the voltage supplied from the low voltage battery power source to the gate driver circuit is equal to or higher than a predetermined value (when the low voltage battery power source is normal), the HV sensor circuit 140 supplies voltage from the low voltage battery power source via the active discharge power source. It operates on the power supplied, and when the voltage supplied to the gate driver circuit from the low-voltage battery power supply is less than a predetermined value (when the low-voltage battery power supply is lost), it can operate on the power supplied from the redundant power supply 120. It is configured so that it can be done.

Furthermore, the safety control circuit, which operates with power supplied from the low-voltage battery power supply and controls the gate driver circuit, uses power supplied from the redundant power supply when the voltage supplied from the low-voltage battery power supply is less than a predetermined value. Operate. The safety control circuit can control the gate driver circuit in response to the HVDC detected by the HV sensor circuit to perform a three-phase short circuit operation.

10: Low voltage battery 20: Current sensor 100a: Controller 100b: Driver circuit 110: GD power supply 120: Redundant power supply (backup power supply)
130: Discharge circuit 131: Discharge resistance 140: HV sensor circuit (voltage sensor)
200: Power conversion device for motor drive 300: Semiconductor device for power conversion 500: Voltage smoothing capacitor 900: Motor 901: High voltage battery 902: Contactor

Claims (4)

an inverter circuit that converts DC power from a high-voltage power supply into AC power and outputs it to the motor;
a drive circuit that controls driving of the inverter circuit;
a smoothing capacitor that smoothes the high voltage applied to the inverter circuit from the high voltage power supply;
a backup power supply circuit that converts DC power from the high voltage power supply or power accumulated in the smoothing capacitor to supply a first power supply voltage and a second power supply voltage;
a booster circuit that boosts the first power supply voltage supplied from the backup power supply circuit or the voltage supplied from the low voltage power supply to supply a third power supply voltage;
a power supply switching circuit that selectively outputs the second power supply voltage supplied from the backup power supply circuit or the third power supply voltage supplied from the booster circuit;
a voltage sensor that operates using power from the second power supply voltage or the third power supply voltage output from the power supply switching circuit and detects a high voltage applied to the inverter circuit;
A control circuit that controls the drive circuit,
When no voltage is supplied from the low voltage power supply and the connection between the high voltage power supply and the inverter circuit is cut off,
The backup power supply circuit uses power stored in the smoothing capacitor to supply the first power supply voltage and the second power supply voltage higher than the first power supply voltage,
The voltage sensor operates using power from the second power supply voltage output from the power supply switching circuit, and detects an induced voltage applied from the motor to the inverter circuit as the high voltage ;
The drive circuit starts activation when the first power supply voltage exceeds a predetermined first voltage value,
The control circuit controls the drive circuit to perform three-phase short circuit control of the inverter circuit when the drive circuit has been activated and the induced voltage detected by the voltage sensor is equal to or higher than a predetermined value. power conversion equipment . The power conversion device according to claim 1 ,
The voltage sensor is a power conversion device that shifts to a stable operating state when the second power supply voltage reaches a predetermined second voltage value that is larger than the first voltage value. The power conversion device according to claim 1 or 2 ,
The booster circuit is a power conversion device that starts activation when the first power supply voltage exceeds a predetermined third voltage value that is larger than the first voltage value. The power conversion device according to claim 1,
a discharge resistor connected in parallel with the smoothing capacitor between the high voltage power supply and the inverter circuit;
a discharge circuit that causes a current to flow through the discharge resistor to discharge the smoothing capacitor,
The discharge circuit is a power conversion device that is driven using power from the third power supply voltage supplied from the booster circuit.

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