Discharge control device and electrically driven inverter for vehicle high-voltage system

Abstract

The invention relates to a discharge control device for a vehicle high-voltage system. The discharge control device comprises a discharge circuit formed by connecting a discharge resistor and an electronic switch in series; the voltage acquisition unit is used for acquiring voltage values at two ends of the bus capacitor in real time; the control unit is configured to judge whether a vehicle high-voltage system needs to be discharged or not on the basis of at least one of a sampling signal received from the voltage acquisition unit, a first communication signal received from the safety airbag module and a second communication signal received from the vehicle control unit; and when it is determined that the vehicle high-voltage system needs to be discharged, operation of the driving chip and / or the electronic switch is selectively controlled, so that the vehicle high-voltage system enters a corresponding discharging mode. The invention also relates to an electrically driven inverter comprising the discharge control device.

Description

Technical Field

[0001] The present application relates to the field of discharge control of a vehicle, and more specifically, to a discharge control device for a high-voltage system of a vehicle, and an electric drive inverter including the discharge control device. Background Art

[0002] In recent years, with the widespread use of new energy vehicles, vehicle safety has received strong attention from car manufacturers, vehicle manufacturers and consumers. In particular, electric vehicles usually have various high-voltage systems, which will cause serious harm to the human body if leaks.

[0003] As an important component of the electric drive system, the electric drive inverter usually has an operating voltage of several hundred volts. Therefore, the high voltage in the bus capacitor must be discharged in time after the vehicle is powered off to prevent electric shock. In addition, in order to ensure the normal operation of the motor and the electric drive inverter, the bus capacitor voltage must be maintained within a certain range. If the bus capacitor voltage is too high and exceeds the voltage withstand capacity of the power device in the inverter, the power device will be damaged.

[0004] Therefore, timely discharge of the high voltage at both ends of the bus capacitor is crucial to ensure the safe operation of the vehicle, especially the electric drive inverter. Conventional high-voltage systems use special discharge resistors for discharge. However, long-term repeated discharge of the discharge resistor will seriously affect the reliability and service life of the electrical components in the electric drive inverter. In addition, systematic failures and random hardware failures in the high-voltage system will also affect the safe implementation of the discharge strategy. In short, it is currently impossible to select an appropriate discharge method based on the specific situation and needs currently faced by the vehicle. Summary of the invention

[0005] In response to the above-mentioned defects existing in the prior art, the present application proposes a new discharge control device for a vehicle high-voltage system (especially an electric drive system), which aims to extend the reliability and service life of the discharge resistor in the electric drive inverter system on the one hand, and effectively reduce the hazards caused by systematic failures and random hardware failures in the electric drive inverter on the other hand, thereby achieving high circuit safety at a low cost.

[0006] According to a first aspect of the present application, a discharge control device for a vehicle high-voltage system is proposed, the vehicle high-voltage system comprising a motor, a DC power supply, a bus capacitor connected across the positive and negative electrodes of the DC power supply, and an electric drive inverter connected between the DC power supply and the motor, the electric drive inverter comprising a drive chip and a power module consisting of a plurality of power devices, the drive chip being used to control the working states of the plurality of power devices, the discharge control device comprising:

[0007] A discharge circuit composed of a discharge resistor and an electronic switch connected in series, wherein the discharge circuit is connected in parallel to both ends of the bus capacitor;

[0008] A voltage acquisition unit, the voltage acquisition unit is used to collect the voltage value at both ends of the bus capacitor in real time; and

[0009] A control unit, the control unit comprising a sampling port connected to the voltage acquisition unit, a first communication port connected to the vehicle's airbag module, a second communication port connected to the vehicle controller, a first control port connected to the driver chip, and a second control port connected to the electronic switch, wherein the control unit is configured to determine whether the vehicle's high-voltage system needs to be discharged based on at least one of a sampling signal received from the voltage acquisition unit, a first communication signal received from the airbag module, and a second communication signal received from the vehicle controller, and when it is determined that the vehicle's high-voltage system needs to be discharged, selectively control the operation of the driver chip and / or the electronic switch to enable the vehicle's high-voltage system to enter different discharge modes.

[0010] Advantageously, the control unit is further configured to: when it is detected that the voltage value across the bus capacitor exceeds a preset voltage threshold,

[0011] outputting a first control signal to the driving chip via the first control port to enable the power module to enter a safety protection state; and

[0012] A second control signal is output to the electronic switch via the second control port, so that the electronic switch turns on the discharge circuit.

[0013] Advantageously, the control unit is further configured to: when a collision signal from the airbag module is detected,

[0014] outputting a first control signal to the driving chip via the first control port to enable the power module to enter a safety protection state; and

[0015] A second control signal is output to the electronic switch via the second control port, so that the electronic switch turns on the discharge circuit.

[0016] Advantageously, the control unit is further configured to: when a discharge request signal from the vehicle controller is detected,

[0017] A third control signal is output to the driving chip via the first control port to discharge the vehicle high voltage system via the motor winding.

[0018] Advantageously, the driving chip is configured to adjust the three-phase current output from the power module when receiving the third control signal so that only the D-axis current is applied to the motor winding and the Q-axis current thereof is zero.

[0019] Advantageously, the control unit is further configured to:

[0020] After a predetermined time has passed since the high voltage system of the vehicle was discharged by means of the motor winding, determining whether the voltage value across the bus capacitor has dropped below a predetermined value; and

[0021] When the voltage value across the bus capacitor does not drop below a predetermined value, the electronic switch is controlled to turn on the discharge circuit.

[0022] Advantageously, the power module is formed as a bridge inverter, and the driving chip is configured to connect all lower bridge arms in the bridge inverter and disconnect all upper bridge arms, or connect all upper bridge arms in the bridge inverter and disconnect all lower bridge arms when receiving the first control signal.

[0023] Advantageously, the control unit is further configured to: when the voltage value across the bus capacitor drops below a safe value, disconnect the electronic switch to end the discharge process of the vehicle high-voltage system.

[0024] Advantageously, the discharge control device forms part of the electric drive inverter.

[0025] According to a second aspect of the present application, an electric drive inverter is also proposed, the electric drive inverter comprising:

[0026] A power module, the power module comprising a DC terminal connected to a DC power supply and an AC terminal connected to a motor;

[0027] A driving chip, the driving chip is used to control the working state of each power device in the power module to adjust the three-phase current output to the motor; and

[0028] As described above, the discharge control device is configured to monitor whether a high voltage fault occurs in the electric drive inverter, and to perform a discharge operation on the electric drive inverter when a high voltage fault is detected.

[0029] The discharge control device for the high-voltage system of a vehicle according to the present application can effectively cope with the working conditions such as normal power-off, collision, high-voltage power failure or load shedding of the whole vehicle. The combination of motor winding discharge and resistor discharge can effectively avoid the hazards caused by random hardware failure and system failure, and can extend the reliability and service life of the resistor. On the basis of not increasing the cost, it ensures the availability and safety of the active discharge function during the life cycle of the whole vehicle. In particular, in the discharge control strategy of the present application, the motor winding and the discharge group are used to work together to reduce the high voltage level of the electric drive inverter. The motor winding can release part or all of the high voltage for a period of time to reduce the voltage to a safe level, and then the discharge resistor is responsible for releasing the remaining high voltage. The advantage of this collaborative discharge control strategy is that the discharge resistor does not have to withstand extremely high voltages, which reduces the pressure on circuit components and reduces system costs; in addition, the high-voltage system of the vehicle can quickly reduce the bus capacitor voltage in the electric drive inverter after power-off, which improves the safety of the high-voltage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] By incorporating the accompanying drawings and Figure 1 With reference to the specific implementation methods used to illustrate certain principles of the present application, other features and advantages of the method of the present application will become clear or be described in more detail.

[0031] Figure 1 A circuit diagram showing one example of a vehicle high voltage system.

[0032] Figure 2 An exemplary embodiment of the present application is shown. Figure 1 The structural principle diagram of the discharge control device of the vehicle high voltage system is shown in FIG.

[0033] Figure 3 Shown by Figure 2 Flow chart of the discharge control strategy executed by the discharge control device shown in FIG. DETAILED DESCRIPTION

[0034] The discharge control device for a vehicle high voltage system according to the present application will be described below with reference to the accompanying drawings and by way of example. In the following description, many specific details are set forth so that a person skilled in the art can more fully understand the present application. However, it is obvious to a person skilled in the art that the present application may be implemented without some of these specific details. Instead, it may be considered to implement the present application with any combination of the following features and elements, regardless of whether they relate to different embodiments. Therefore, the following various aspects, features, embodiments and advantages are for illustrative purposes only and should not be regarded as elements or limitations of the claims.

[0035] Figure 1The circuit diagram of an example of a vehicle high voltage system is shown. The high voltage system may be, for example, an electric drive system of a vehicle, which includes a motor, a DC power supply, a bus capacitor Cs connected between the positive and negative electrodes (BAT+, BAT-) of the DC power supply, and an electric drive inverter connected between the DC power supply and the motor. The electric drive inverter includes a drive chip ( Figure 1 The power module is composed of a plurality of power devices T1 to T6, and the driving chip can provide a PWM control signal to each power device in the power module to control the working state of each power device. Figure 1 As shown in , the power devices T1 to T6 form a three-phase H-bridge inverter circuit, which is connected to the three-phase winding of the motor in a star connection manner.

[0036] In order to discharge the voltage across the bus capacitor when necessary, a discharge circuit consisting of a discharge resistor R1 and an electronic switch S1 connected in series is provided in the electric drive system. The discharge circuit can be connected in parallel across the bus capacitor Cs.

[0037] against Figure 1 There are usually two types of discharge strategies for the electric drive system shown in:

[0038] - The first solution is to control the three-phase current output from the power module to the motor in a software-controlled manner, with the goal of making the Q-axis current flowing through the motor winding zero, thereby preventing the motor from generating torque; at the same time, applying a D-axis current to the motor winding, thereby converting high-voltage electrical energy into heat energy for discharge through the motor winding;

[0039] -The second solution is to discharge by controlling the electronic switch S1 to connect the discharge resistor R1. This solution can perform discharge by using software to send a level signal to control the electronic switch, or it can use the functional characteristics of the hardware circuit itself to perform rapid discharge in the event of a low-voltage fault. The control logic of this discharge solution is relatively simple, the circuit is easier to implement, and it has a wide range of applications.

[0040] However, the first discharge scheme mentioned above requires that the software and power module in the electric drive inverter can work normally, so it cannot be safely used in some scenarios. For example, in the case of high-voltage voltage failure or load shedding conditions, the switching of power devices (for example, IGBT) will generate spike voltages and cause breakdown; in addition, in the case of low-voltage power supply failure, the software function may fail and be unable to output control signals, so discharging through the motor windings cannot effectively reduce the hazards caused by systematic failures and random hardware failures, so that the high-voltage safety of the entire vehicle still has hidden dangers.

[0041] The second discharge scheme is affected by the complex use environment of the vehicle and the frequent power on and off requirements, and has very high requirements for the reliability of the discharge resistor. Long-term repeated discharge will seriously affect the reliability and service life of the electrical components in the electric drive inverter, and in severe cases will even burn the discharge resistor; in addition, the discharge resistor will generate serious heat after long-term operation, which will have a potential serious impact on the inverter power module and other system circuits, so it is necessary to add a temperature detection protection circuit, which leads to an increase in hardware costs.

[0042] In response to the defects in the above-mentioned discharge control strategy, the present application proposes a new discharge control device for a vehicle high-voltage system (especially an electric drive system), which aims to extend the reliability and service life of the discharge resistor in the electric drive inverter system on the one hand, and effectively reduce the hazards caused by systematic failures and random hardware failures in the electric drive inverter on the other hand, thereby achieving high circuit safety at a low cost.

[0043] Figure 2 An exemplary embodiment of the present application is shown. Figure 1 The structural principle diagram of the discharge control device of the vehicle high voltage system is shown in FIG. The discharge control device can be formed as a part of the electric drive inverter of the vehicle. Figure 2 The composition structure and control principle of the discharge control device are described in detail.

[0044] The difference from the conventional discharge strategy is that the discharge control device of this embodiment is provided with a voltage acquisition unit for real-time acquisition of the voltage value across the bus capacitor Cs. The voltage value is fed back to the sampling port of the control unit. The control unit is the core control element of the discharge control device. It can execute different active discharge control strategies according to the sampling signal provided by the bus voltage acquisition unit and in combination with the indication signal provided by the airbag and the vehicle controller VCU.

[0045] In addition to the sampling port connected to the voltage acquisition unit, the control unit also includes a first communication port connected to the airbag module of the vehicle, a second communication port connected to the vehicle controller, a first control port connected to the driver chip, and a second control port connected to the electronic switch C1. The control unit is configured to determine whether the vehicle high-voltage system needs to be discharged based on at least one of the sampling signal received from the voltage acquisition unit, the first communication signal received from the airbag module, and the second communication signal received from the vehicle controller, and selectively control the operation of the driver chip and / or the electronic switch C1 when it is determined that the vehicle high-voltage system needs to be discharged, so that the vehicle high-voltage system enters a corresponding discharge mode.

[0046] Figure 3 Shown by Figure 2Specifically, the discharge strategy executed by the discharge control device, especially the control unit thereof, mainly includes the following three situations:

[0047] 1) When the voltage value across the bus capacitor Cs exceeds a preset voltage threshold, the control unit can output a first control signal to the driver chip via the first control port to put the power module into a safety protection state. At the same time, the control unit also outputs a second control signal to the electronic switch C1 via the second control port to turn on the discharge circuit, that is, to discharge the capacitor Cs using the discharge resistor R1.

[0048] Here, the safety protection state may be, for example, an ASC (active short circuit) state. Figure 1 In the example of an electric drive inverter, the power module is formed as a bridge inverter composed of six IGBTs. When receiving the first control signal, the driver chip can connect all the lower bridge arms T4, T5, T6 in the bridge inverter and disconnect all the upper bridge arms T1, T2, T3 (or connect all the upper bridge arms T1, T2, T3 in the bridge inverter and disconnect all the lower bridge arms T4, T5, T6) to make the motor enter the ASC state. This is because the IGBT itself has limited overvoltage resistance. If a spike voltage is generated during the shutdown process due to the stray inductance in the inverter circuit, it is easy to cause breakdown damage. Therefore, this discharge strategy can effectively protect the inverter power module under abnormal high-voltage power supply or load shedding conditions.

[0049] 2) When a collision signal from the airbag module (ABM) is detected, the control unit can output a first control signal to the driver chip via the first control port to put the power module into a safety protection state (e.g., ASC). At the same time, the control unit can also output a second control signal to the electronic switch C1 via the second control port to connect the electronic switch C1 to the discharge circuit so as to use the discharge resistor for active discharge until the discharge is completed. For example, when the voltage value across the bus capacitor Cs drops below a safe value (e.g., 60V), the electronic switch C1 can be disconnected to end the discharge process of the vehicle's high-voltage system.

[0050] When a vehicle collides while traveling at high speed, since the vehicle is in a starting state, after the collision, due to reasons such as damage to the high-voltage circuit, leakage of electricity or even generation of sparks may occur, resulting in the body being electrified, which poses a great danger to the personal safety of the passengers in the vehicle. In particular, when an electric vehicle collides during driving, since the motor in the vehicle is still running at high speed, a back electromotive force will be generated. At this time, the excessive back electromotive force will cause overvoltage in the electric drive system, thereby damaging various electrical components in the electric drive system, especially the power devices in the inverter. In response to this, the discharge control strategy can quickly identify the vehicle collision signal from the airbag and can respond to it in a timely manner as a safety protection device, especially for ensuring the safety of the vehicle motor during a collision to reduce the impact caused by a collision accident.

[0051] 3) When a discharge request signal from the vehicle control unit VCU is detected, the control unit can output a third control signal to the drive chip via the first control port to discharge the vehicle high-voltage system by means of the motor winding. When receiving the third control signal, the drive chip can adjust the three-phase current output from the power module so that only the D-axis current is applied to the stator winding of the motor and its Q-axis current is zero.

[0052] In this article, the "D-axis current" refers to the current component along the rotation axis of the motor (usually the rotor axis of the motor), also known as the direct-axis current. The change of the D-axis current will cause the motor winding to heat up. The "Q-axis current" refers to the current component along the quadrature axis perpendicular to the D-axis. It is usually used to adjust the magnetic field position of the motor. The change of the Q-axis current will cause the change of the magnetic field position of the motor, thereby affecting the output torque and speed of the motor.

[0053] In this discharge strategy, when a discharge request sent by the vehicle control unit is detected, the VCU can send a PWM signal in software mode to apply the D-axis current, so that the motor discharges through the stator winding, and within a certain time (for example, 500 ms), 90-95% of the electrical energy is converted into heat energy and released through the motor winding. During the discharge process of the motor winding, discharge monitoring is carried out through the bus voltage acquisition module (for example, monitoring the change of the slope of the voltage curve). If an abnormality is found, the discharge resistor is triggered for active discharge. For example, after a predetermined time from the start of the motor winding discharge, the control unit can collect and judge whether the voltage value across the bus capacitor Cs drops below a predetermined value. If it does not drop below the predetermined value, the control electronic switch C1 is turned on to connect the discharge circuit to switch to the discharge resistor for discharge.

[0054] Since the discharge of the motor winding needs to be carried out by driving the power tube, and the power supply of the power tube driving circuit usually comes from a high-voltage switching power supply or a linear power supply, due to the requirements and limitations of the operating voltage range of the driving power supply, discharging only through the motor winding may not ensure that the high-voltage energy in the system is completely released below the safe voltage. Therefore, as another optional expansion scheme of the discharge control strategy, if the abnormal change of the bus capacitor voltage is not detected during the entire discharge process of the motor winding, the discharge resistor can be automatically switched after a certain period of time (for example, 500ms) to continue discharging to below 60V. Therefore, this control scheme is compatible with various hardware circuit designs and effectively ensures the high-voltage safety when the vehicle is powered off.

[0055] In this discharge control strategy, the motor winding and the discharge group work together to reduce the high voltage level of the electric drive inverter. The motor winding can release part or all of the high voltage for a period of time to reduce the voltage to a safe level, and then the discharge resistor is responsible for releasing the remaining high voltage. The benefits of this coordinated discharge control strategy are: the discharge resistor does not have to withstand extremely high voltage, which reduces the pressure on circuit components and reduces system costs; in addition, the vehicle's high-voltage system can quickly reduce the bus capacitor voltage in the electric drive inverter after power is off, improving the safety of the high-voltage system.

[0056] The discharge control device for the vehicle high-voltage system according to the present application can effectively cope with operating scenarios such as normal power-off of the vehicle, collision, high-voltage power supply failure or load shedding. The combination of motor winding discharge and resistor discharge can effectively avoid the hazards caused by random hardware failure and system failure, and extend the reliability and service life of the resistor. Without increasing costs, the availability and safety of the active discharge function are ensured during the life cycle of the vehicle.

[0057] An optional embodiment of the present application also relates to an electric drive inverter, which includes: a power module, the power module includes a DC terminal connected to a DC power supply and an AC terminal connected to a motor; a drive chip, the drive chip is used to control the working state of each power device in the power module to adjust the three-phase current output to the motor; and Figure 2 The described discharge control device is configured to monitor whether a high voltage fault occurs in the electric drive inverter, and to perform a discharge operation on the electric drive inverter when a high voltage fault is detected.

[0058] It will be appreciated by those skilled in the art that the various steps of the method of the present application are not limited to being implemented in the order listed above. Although the present application has been disclosed as above with preferred embodiments, the present application is not limited thereto. Any changes and modifications made by any person skilled in the art without departing from the spirit and scope of the present application shall be included in the protection scope of the present application, and therefore the protection scope of the present application shall be subject to the scope defined by the claims.

Claims

1. A discharge control device for a vehicle high-voltage system, the vehicle high-voltage system comprising a motor, a DC power supply, a bus capacitor (Cs) connected across the positive and negative electrodes of the DC power supply, and an electric drive inverter connected between the DC power supply and the motor, the electric drive inverter comprising a drive chip and a power module composed of a plurality of power devices (T1-T6), the drive chip being used to control the working states of the plurality of power devices, It is characterized in that The discharge control device comprises: A discharge circuit composed of a discharge resistor (R1) and an electronic switch (S1) connected in series, wherein the discharge circuit is connected in parallel to both ends of the bus capacitor (Cs); A voltage acquisition unit, the voltage acquisition unit is used to collect the voltage value across the bus capacitor (Cs) in real time; and A control unit, the control unit comprising a sampling port connected to the voltage acquisition unit, a first communication port connected to the vehicle's airbag module, a second communication port connected to the vehicle controller, a first control port connected to the driver chip, and a second control port connected to the electronic switch (S1), wherein the control unit is configured to determine whether the vehicle's high-voltage system needs to be discharged based on at least one of a sampling signal received from the voltage acquisition unit, a first communication signal received from the airbag module, and a second communication signal received from the vehicle controller, and when it is determined that the vehicle's high-voltage system needs to be discharged, selectively control the operation of the driver chip and / or the electronic switch (S1) to enable the vehicle's high-voltage system to enter different discharge modes.

2. The discharge control device according to claim 1, It is characterized in that The control unit is further configured to: when it is detected that the voltage value across the bus capacitor (Cs) exceeds a preset voltage threshold, Outputting a first control signal to the driving chip via the first control port to enable the power module to enter a safety protection state; and A second control signal is output to the electronic switch (S1) via the second control port, so that the electronic switch (S1) turns on the discharge circuit.

3. The discharge control device according to claim 1, It is characterized in that The control unit is further configured to: when a collision signal from the airbag module is detected, Outputting a first control signal to the driving chip via the first control port to enable the power module to enter a safety protection state; and A second control signal is output to the electronic switch (S1) via the second control port, so that the electronic switch (S1) turns on the discharge circuit.

4. The discharge control device according to claim 1, It is characterized in that The control unit is further configured to: when a discharge request signal from the vehicle controller is detected, A third control signal is output to the driving chip via the first control port to discharge the vehicle high voltage system via the motor winding.

5. The discharge control device according to claim 4, It is characterized in that The driving chip is configured to adjust the three-phase current output from the power module so that only the D-axis current is applied to the motor winding and the Q-axis current is zero when receiving the third control signal.

6. The discharge control device according to claim 4 or 5, It is characterized in that The control unit is further configured as: After a predetermined time period from when the high voltage system of the vehicle is discharged by means of the motor winding, determining whether the voltage value across the bus capacitor (Cs) drops below a predetermined value; and When the voltage value across the bus capacitor (Cs) does not drop below a predetermined value, the electronic switch (S1) is controlled to turn on the discharge circuit.

7. The discharge control device according to claim 2 or 3, It is characterized in that The power module is formed as a bridge inverter, and the driving chip is configured to connect all lower bridge arms in the bridge inverter and disconnect all upper bridge arms, or connect all upper bridge arms in the bridge inverter and disconnect all lower bridge arms when receiving the first control signal.

8. The discharge control device according to claim 2 or 3, It is characterized in that The control unit is further configured to disconnect the electronic switch (S1) to end the discharge process of the vehicle high voltage system when the voltage value across the bus capacitor (Cs) drops below a safe value.

9. The discharge control device according to any one of claims 1 to 5, It is characterized in that The discharge control device forms part of the electric drive inverter.

10. An electric drive inverter, It is characterized in that The electric drive inverter includes: A power module, the power module comprising a DC terminal connected to a DC power supply and an AC terminal connected to a motor; A driving chip, the driving chip is used to control the working state of each power device in the power module to adjust the three-phase current output to the motor; and According to any one of claims 1 to 9, the discharge control device is configured to monitor whether a high voltage fault occurs in the electric drive inverter, and perform a discharge operation on the electric drive inverter when a high voltage fault is detected.

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