Discharge control device for vehicle high-voltage system and electric drive inverter

Abstract

This application relates to a discharge control device for a vehicle high-voltage system, comprising: a discharge circuit consisting of a discharge resistor and an electronic switch connected in series; a voltage acquisition unit for real-time acquisition of the voltage value across the bus capacitor; and a control unit configured to determine whether it is necessary to discharge the vehicle high-voltage system 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 selectively controlling the operation of the drive chip and / or the electronic switch when it is determined that the vehicle high-voltage system needs to be discharged, so as to cause the vehicle high-voltage system to enter a corresponding discharge mode. This application also relates to an electric drive inverter including the discharge control device.

Description

Technical Field

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

[0002] In recent years, with the widespread application of new energy vehicles, vehicle safety has become a major concern for automakers, manufacturers, and consumers. In particular, electric vehicles typically contain various high-voltage systems, and leaks in these systems can cause serious harm to humans.

[0003] As a crucial component of the electric drive system, the electric drive inverter typically operates at voltages of several hundred volts. Therefore, after the vehicle is powered off, it is essential to promptly discharge the high voltage in its bus capacitor to prevent electric shock. Furthermore, 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, exceeding the voltage withstand capability of the power devices in the inverter, it will damage the power devices.

[0004] Therefore, timely discharge of the high voltage across the bus capacitor is crucial for ensuring the safe operation of vehicles, especially electric drive inverters. Conventional high-voltage systems use dedicated discharge resistors; however, the repeated discharge from these resistors over a long period can severely impact the reliability and lifespan of electrical components in the electric drive inverter. Furthermore, systemic failures and random hardware malfunctions in the high-voltage system can also affect the safe implementation of the discharge strategy. In short, it is currently impossible to select an appropriate discharge method based solely on the specific circumstances and needs of the vehicle. Summary of the Invention

[0005] In view of the above-mentioned defects in the prior art, this application proposes a new discharge control device for vehicle high-voltage systems (especially electric drive systems). It 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 harm caused by systematic failures and random hardware failures in the electric drive inverter on the other hand, thereby achieving high circuit safety at low cost.

[0006] According to a first aspect of this application, a discharge control device for a vehicle high-voltage system is provided. The vehicle high-voltage system includes a motor, a DC power supply, a bus capacitor connected between the positive and negative terminals 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 driver chip and a power module composed of multiple power devices. The driver chip is used to control the operating state of the multiple power devices. The discharge control device includes:

[0007] A discharge circuit consisting of a discharge resistor and an electronic switch connected in series, wherein the discharge circuit is connected in parallel across the two ends of the bus capacitor.

[0008] A voltage acquisition unit, used to acquire the voltage value across the bus capacitor in real time; and

[0009] The control unit includes 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 drive chip, and a second control port connected to the electronic switch. The control unit is configured to determine whether it is necessary to discharge the vehicle's high-voltage system 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. When it is determined that the vehicle's high-voltage system needs to be discharged, the control unit selectively controls the operation of the drive chip and / or the electronic switch to cause the vehicle's high-voltage system to enter different discharge modes.

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

[0011] A first control signal is output to the driver chip via the first control port to cause 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 connects the discharge circuit.

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

[0014] A first control signal is output to the driver chip via the first control port to cause 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 connects the discharge circuit.

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

[0017] A third control signal is output to the drive chip via the first control port to discharge the vehicle's high-voltage system through the motor windings.

[0018] Advantageously, the drive chip is configured to, upon receiving the third control signal, adjust the three-phase current output from the power module such that only the D-axis current is applied to the motor windings and its Q-axis current is zero.

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

[0020] After a predetermined time has elapsed since the high-voltage system of the vehicle was discharged via the motor windings, it is determined whether the voltage across the bus capacitor has dropped below a predetermined value; and

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

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

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

[0024] Advantageously, the discharge control device is incorporated into the electric drive inverter.

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

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

[0027] A driver chip, used to control the operating state of each power device in the power module to regulate the three-phase current output to the motor; and

[0028] The discharge control device described above 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 a vehicle high-voltage system according to this application can effectively handle various operating conditions such as normal vehicle power-off, collision, high-voltage power supply failure, or load shedding. By combining motor winding discharge and resistor discharge, it 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, it ensures the availability and safety of active discharge function throughout the vehicle's lifecycle. Specifically, in the discharge control strategy of this application, the motor winding and 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, reducing the voltage to a safe level, and then the discharge resistor is responsible for releasing the remaining high voltage. The advantages of this collaborative discharge control strategy are: the discharge resistor does not have to withstand extremely high voltage, which reduces the stress on circuit components and lowers system costs; in addition, the vehicle's high-voltage system can quickly reduce the bus capacitor voltage in the electric drive inverter after power-off, improving the safety of the high-voltage system. Attached Figure Description

[0030] By incorporating the figures in this article and subsequently the appendix Figure 1 The specific embodiments used to illustrate certain principles of this application will make other features and advantages of the methods of this application clearer or more specific.

[0031] Figure 1 A circuit diagram of an example of a vehicle's high-voltage system is shown.

[0032] Figure 2 An exemplary embodiment of the present application is shown for use with Figure 1 The diagram shows the structural principle of the discharge control device for the vehicle's high-voltage system.

[0033] Figure 3 It shows the result of Figure 2 The flowchart shows the discharge control strategy executed by the discharge control device. Detailed Implementation

[0034] The discharge control device for a vehicle high-voltage system according to this application will now be described with reference to the accompanying drawings and embodiments. In the following description, numerous specific details are set forth to enable those skilled in the art to gain a more complete understanding of this application. However, it will be apparent to those skilled in the art that implementation of this application may not include some of these specific details. Instead, this application may be practiced with any combination of the following features and elements, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments, and advantages are for illustrative purposes only and should not be construed as elements or limitations of the claims.

[0035] Figure 1A circuit diagram of an example high-voltage system for a vehicle is shown. This high-voltage system could be, for example, the vehicle's electric drive system, including a motor, a DC power supply, a bus capacitor Cs connected between the positive and negative terminals (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 driver chip. Figure 1 (Not shown in the image) and a power module composed of multiple power devices T1 to T6. The driver chip can provide PWM control signals to each power device in the power module to control the operating state of each power device. For example... Figure 1 As shown, a three-phase H-bridge inverter circuit is formed by power devices T1 to T6, and the circuit is connected to the three-phase windings of the motor in a star connection.

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

[0037] against Figure 1 The discharge strategies of the electric drive systems shown typically fall into two categories:

[0038] - The first approach is to control the three-phase current output from the power module to the motor using software control. The goal is to make the Q-axis current flowing through the motor windings zero, thereby preventing the motor from generating torque. At the same time, D-axis current is applied to the motor windings, so that the high-voltage electrical energy is converted into heat energy for discharge through the motor windings.

[0039] - The second approach is to discharge by controlling the electronic switch S1 to connect the discharge resistor R1. This approach can be implemented by using software to send a level signal to control the electronic switch, or by utilizing the hardware circuit's own functional characteristics to perform rapid discharge during low-voltage faults. The control logic of this discharge approach is relatively simple, the circuit is easy to implement, and it has wide applicability.

[0040] However, the first discharge scheme mentioned above requires both the software and power modules in the electric drive inverter to function properly. Therefore, it cannot be safely applied in certain scenarios. For example, in the event of a high-voltage fault or load shedding, the switching of power devices (e.g., IGBTs) may generate voltage spikes that could lead to breakdown. In addition, in the event of a low-voltage power supply fault, the software function may fail and be unable to output control signals. Therefore, discharging through the motor windings cannot effectively reduce the hazards caused by systemic failures and random hardware failures, leaving the high-voltage safety of the entire vehicle still at risk.

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

[0042] To address the shortcomings of the aforementioned discharge control strategies, this application proposes a new discharge control device for vehicle high-voltage systems (especially electric drive systems). This device 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 harm caused by systematic failures and random hardware failures in the electric drive inverter on the other hand, thereby achieving high circuit safety at low cost.

[0043] Figure 2 An exemplary embodiment of the present application is shown for use with Figure 1 The diagram shows the structural principle of the discharge control device for the vehicle's high-voltage system. This discharge control device can be integrated into the vehicle's electric drive inverter. The following section discusses... Figure 2 This section will describe in detail the composition and control principle of the discharge control device.

[0044] Unlike conventional discharge strategies, the discharge control device in this embodiment is equipped with a voltage acquisition unit, which is used to acquire the voltage value across the bus capacitor Cs in real time. This 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, which can execute different active discharge control strategies based on the sampling signal provided by the bus voltage acquisition unit and the indication signals 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 vehicle's airbag module, a second communication port connected to the vehicle controller, a first control port connected to the drive chip, and a second control port connected to the electronic switch C1. The control unit is configured to determine whether it is necessary to discharge the vehicle's high-voltage system 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. When it is determined that the vehicle's high-voltage system needs to be discharged, the control unit selectively controls the operation of the drive chip and / or the electronic switch C1 to cause the vehicle's high-voltage system to enter a corresponding discharge mode.

[0046] Figure 3 It shows the result of Figure 2The flowchart shown illustrates the discharge control strategy executed by the discharge control device. Specifically, the discharge strategy executed by this discharge control device, particularly its control unit, mainly includes the following three cases:

[0047] 1) When the voltage across the bus capacitor Cs exceeds a preset voltage threshold, the control unit outputs a first control signal to the drive 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 could be, for example, the ASC (Active Short Circuit) state. Figure 1 In the example of the electric drive inverter, the power module is configured as a bridge inverter consisting of six IGBTs. Upon receiving the first control signal, the drive chip can turn on all the lower arms T4, T5, and T6 of the bridge inverter and disconnect all the upper arms T1, T2, and T3 (or turn on all the upper arms T1, T2, and T3 of the bridge inverter and disconnect all the lower arms T4, T5, and T6) to put the motor into ASC state. This is because IGBTs themselves have limited overvoltage tolerance. If a voltage spike is generated during the turn-off process due to stray inductance in the inverter circuit, it can easily cause breakdown damage. Therefore, this discharge strategy can effectively protect the inverter power module under abnormal high-voltage power supply conditions or load shedding conditions.

[0049] 2) When a collision signal is detected from the airbag module (ABM), the control unit can output a first control signal to the drive chip via the first control port to put the power module into a safety protection state (e.g., ASC). Simultaneously, the control unit can also output a second control signal to the electronic switch C1 via the second control port to activate the discharge circuit, allowing active discharge using a discharge resistor until the discharge is complete. For example, when the voltage 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 at high speed, because the vehicle is still running, the impact can lead to electrical leakage or even sparks due to damage to high-voltage circuits, causing the vehicle body to become electrified. This poses a significant danger to the safety of passengers. In particular, when an electric vehicle collides while in motion, the motor continues to operate at high speed, generating a back electromotive force (EMF). Excessive back EMF can cause overvoltage in the electric drive system, damaging various electrical components, especially the power devices in the inverter. This discharge control strategy is a safety protection device that can quickly identify collision signals from the airbag and react accordingly, particularly ensuring the safety of the vehicle's motor during a collision to reduce the impact of the accident.

[0051] 3) When a discharge request signal is detected from the vehicle control unit (VCU), the control unit can output a third control signal to the drive chip via the first control port to discharge the vehicle's high-voltage system through the motor windings. Upon 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 windings of the motor and its Q-axis current is zero.

[0052] In this article, "D-axis current" refers to the current component along the rotational axis of the motor (usually the rotor shaft), also known as direct-axis current. Changes in the D-axis current cause the motor windings to heat up. "Q-axis current" refers to the current component along the quadrature axis perpendicular to the D-axis. It is typically used to adjust the position of the motor's magnetic field. Changes in the Q-axis current cause changes in the position of the motor's magnetic field, thus affecting the motor's output torque and speed.

[0053] In this discharge strategy, upon detecting a discharge request from the vehicle controller, the VCU can send a PWM signal via software to apply D-axis current, causing the motor to discharge through the stator windings. Within a certain time (e.g., 500ms), 90-95% of the electrical energy is converted into heat energy and released through the motor windings. During the motor winding discharge process, the bus voltage acquisition module monitors the discharge (e.g., monitoring changes in the slope of the voltage curve). If an abnormality is detected, the discharge resistor is triggered to actively discharge. For example, the control unit can acquire and determine whether the voltage across the bus capacitor Cs has dropped below a predetermined value after a predetermined time since the motor windings began discharging. If it has not dropped below the predetermined value, the electronic switch C1 is controlled to connect the discharge circuit, switching to the discharge resistor for discharge.

[0054] Since motor winding discharge requires a power transistor, and the power transistor drive circuit is typically powered by a high-voltage switching power supply or a linear power supply, the discharge from the motor windings alone may not be sufficient to completely release the high-voltage energy below a safe voltage due to the limitations of the drive power supply's operating voltage range. Therefore, as an alternative extension of this discharge control strategy, if no abnormal changes in the bus capacitor voltage are detected during the entire discharge process of the motor windings, the discharge resistor can be automatically switched after a certain time (e.g., 500ms) to continue discharging below 60V. Thus, this control scheme is compatible with various hardware circuit designs and effectively ensures high-voltage safety when the vehicle is powered off.

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

[0056] The discharge control device for vehicle high-voltage systems according to this application can effectively cope with operating conditions such as normal vehicle power-off, collision, high-voltage power supply failure, or load shedding. By combining motor winding discharge and resistor discharge, it can effectively avoid the harm caused by random hardware failure and system failure, and extend the reliability and service life of the resistor. Without increasing costs, it ensures the availability and safety of active discharge function throughout the vehicle's life cycle.

[0057] An optional embodiment of this application also relates to an electric drive inverter, comprising: a power module including a DC terminal connected to a DC power supply and an AC terminal connected to a motor; a drive chip for controlling the operating state of various power devices in the power module to regulate the three-phase current output to the motor; and referenced above. 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 understood by those skilled in the art that the steps of the method according to this application are not limited to being performed in the order listed above. Although this application has been disclosed above with reference to preferred embodiments, it is not limited thereto. Any modifications and alterations made by those skilled in the art without departing from the spirit and scope of this application should be included within the protection scope of this application; therefore, the protection scope of this application should be determined by the scope defined in the claims.

Claims

1. A discharge control device for a vehicle high-voltage system, the vehicle high-voltage system comprising a motor, a direct-current power supply, a bus capacitor (Cs) connected across positive and negative terminals of the direct-current power supply, and an electric drive inverter connected between the direct-current 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 configured to control an operating state of the plurality of power devices, characterized in that, The discharge control device comprises: a discharge circuit composed of a discharge resistor (R1) and an electronic switch (S1) in series, the discharge circuit being connected in parallel across the bus capacitor (Cs); a voltage acquisition unit for acquiring the voltage value across the bus capacitor (Cs) in real time; and a control unit comprising a sampling port connected to the voltage acquisition unit, a first communication port connected to a safety airbag module of the vehicle, a second communication port connected to a vehicle control unit, a first control port connected to the drive chip, and a second control port connected to the electronic switch (S1), wherein 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 safety airbag module, and the second communication signal received from the vehicle control unit, and selectively control the operation of the drive chip and / or the electronic switch (S1) to make the vehicle high-voltage system enter different discharge modes when it is determined that the vehicle high-voltage system needs to be discharged, wherein the control unit is further configured to output a third control signal to the drive chip via the first control port to discharge the vehicle high-voltage system by means of motor windings when a discharge request signal from the vehicle control unit is detected, determine whether the voltage value across the bus capacitor (Cs) drops below a predetermined value after a predetermined time period since the vehicle high-voltage system is discharged by means of motor windings; and control the electronic switch (S1) to turn on the discharge circuit when the voltage value across the bus capacitor (Cs) does not drop below the predetermined value.

2. The discharge control device according to claim 1, characterized by The control unit is further configured to, when it is detected that the voltage value across the bus capacitor (Cs) exceeds a pre-set voltage threshold, output a first control signal to the drive chip via the first control port to make the power module enter a safety protection state; and output a second control signal to the electronic switch (S1) via the second control port to make the electronic switch (S1) turn on the discharge circuit.

3. The discharge control device according to claim 1, characterized by The control unit is further configured to, when a collision signal from the safety airbag module is detected, output a first control signal to the drive chip via the first control port to make the power module enter a safety protection state; and output a second control signal to the electronic switch (S1) via the second control port to make the electronic switch (S1) turn on the discharge circuit.

4. The discharge control device according to claim 1, characterized by The drive chip is configured to, when the third control signal is received, adjust the three-phase current output from the power module so that only D-axis current is applied on the motor windings and its Q-axis current is zero.

5. The discharge control device according to claim 2 or 3, characterized by The power module is formed as a bridge inverter, and the drive chip is configured to, when the first control signal is received, turn on all lower bridge arms and turn off all upper bridge arms in the bridge inverter, or turn on all upper bridge arms and turn off all lower bridge arms in the bridge inverter.

6. The discharge control device according to claim 2 or 3, characterized by The control unit is further configured to: when the voltage value across the bus capacitor (Cs) falls below a safety value, turn off the electronic switch (S1) to end the discharge process of the vehicle high-voltage system.

7. The discharge control device according to any one of claims 1 to 4, characterized by The discharge control device is formed as part of the electric drive inverter.

8. An electric drive inverter, characterized by The electric drive inverter comprises: a power module comprising a direct current end connected to a direct current power supply and an alternating current end connected to the motor; a drive chip for controlling the working state of each power device in the power module to adjust the three-phase current output to the motor; and The discharge control device according to any one of claims 1 to 7, 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 monitored.

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