Method and system for detecting failure of power module

Abstract

The invention relates to a method for detecting failure of a power module. The method comprises the following steps: monitoring voltage data of bus voltage in a pre-charging stage of a high-voltage system; when the voltage data exceeds a preset safe voltage threshold value, the driving circuit is controlled to alternately output PWM driving signals with set frequency and set duty ratio to a lower bridge arm and an upper bridge arm of the power module, so that the upper bridge arm and the lower bridge arm are alternately conducted; in the alternating conduction process of the upper bridge arm and the lower bridge arm, monitoring whether a preset fault signal is detected within a set time; and judging whether the power module fails based on the detection result. The power module failure detection method can effectively identify whether the power module has the fault condition of short circuit of the upper bridge arm chip or the lower bridge arm chip CE, thereby preventing serious safety accidents such as bridge arm direct connection and secondary overcurrent caused by driving the failed power module from the source, ensuring the safe operation of a high-voltage system, and improving the reliability of the power module. And the starting safety and the operation reliability of the electric drive system are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric drive systems of new energy vehicles, and particularly relates to a detection method and system for failure of a power module. BACKGROUND

[0002] A power module, such as an IGBT module, is a core execution device of a motor controller of an electric vehicle, and its reliability is directly related to the power performance and high-voltage system safety of the vehicle. Due to factors such as manufacturing process defects, long-term harsh working conditions, and material aging, the power module has a risk of failure. At present, the industry generally designs drive circuit desaturation protection, under-voltage / over-voltage protection and other functions in the motor controller for monitoring and preventing serious faults of the power module during operation, but such protection mechanisms are difficult to determine whether a specific type of hidden fault exists at the beginning of system power-on and before the power module is working, especially a very dangerous and difficult-to-detect fault: only a single IGBT chip in the upper bridge arm or lower bridge arm of the power module has a collector-emitter short circuit, and the controller does not know the existence of such a fault, which easily leads to bridge arm short circuit when the drive signal is turned on blindly, causing secondary overcurrent and even burning the module, thereby seriously threatening the safety of the high-voltage system. Therefore, failure determination of the power module before the electric vehicle starts is of great significance to the safety of the electric drive system and the high-voltage system.

[0003] At present, detection of such faults relies on after-sales maintenance means, that is, using a multimeter or other tools to measure the resistance or diode voltage drop between the pins of the module offline. This method requires the motor controller to be removed from the vehicle, and is only suitable for fault analysis of the motor controller. Therefore, there is an urgent need for a detection method that can automatically detect whether the power module has a CE short circuit of the upper bridge arm or lower bridge arm chip during the high-voltage power-on stage of the electric vehicle without disassembly, so as to eliminate the risk of secondary failure from the source and ensure the safety of the electric drive system. SUMMARY

[0004] The present application provides a detection method and system for failure of a power module, which can automatically detect during the high-voltage power-on stage of the electric vehicle, and effectively determine whether the power module has a CE short circuit fault of the upper bridge arm or lower bridge arm chip without disassembly of the controller, so as to eliminate the risk of secondary failure from the source and ensure the safety of the electric drive system.

[0005] In a first aspect, the present application provides a detection method for failure of a power module, comprising the following steps: monitoring voltage data of a bus voltage during a pre-charging stage of a high-voltage system; when the voltage data exceeds a preset safety voltage threshold, controlling a drive circuit to alternately output a PWM drive signal with a set frequency and a set duty cycle to a lower bridge arm and an upper bridge arm of the power module, so as to alternately turn on the upper bridge arm and the lower bridge arm; In the process of alternating conduction of the upper bridge arm and the lower bridge arm, whether a preset fault signal is detected within a set time is monitored; Based on the detection result, whether the power module is failed is determined.

[0006] In combination with the first aspect, in an implementation manner, the preset safety voltage threshold is lower than a rated working voltage of the high-voltage system.

[0007] In combination with the first aspect, in an implementation manner, the preset safety voltage threshold is 100 V.

[0008] In combination with the first aspect, in an implementation manner, the control driving circuit alternately outputs a PWM driving signal with a set frequency and a set duty cycle to the lower bridge arm and the upper bridge arm of the power module to make the upper bridge arm and the lower bridge arm alternately conduct, and specifically includes: The control driving circuit outputs the PWM driving signal with the set frequency and the set duty cycle to all the switching tubes of the lower bridge arm of the power module, and keeps all the switching tubes of the upper bridge arm off; The control driving circuit outputs the PWM driving signal with the set frequency and the set duty cycle to all the switching tubes of the upper bridge arm of the power module, and keeps all the switching tubes of the lower bridge arm off.

[0009] In combination with the first aspect, in an implementation manner, the set frequency of the PWM driving signal is 10 kHz, and the set duty cycle is 50%.

[0010] In combination with the first aspect, in an implementation manner, the preset fault signal includes a bus under-voltage fault signal or a driving desaturation protection fault signal.

[0011] In combination with the first aspect, in an implementation manner, after determining whether the power module is failed based on the detection result, the method further includes: If it is determined that the power module is failed, a fault handling measure is taken.

[0012] In combination with the first aspect, in an implementation manner, the fault handling measure includes sending a fault signal to a vehicle control unit, and after receiving the fault signal, the vehicle control unit controls a battery management system to cut off power supply to an electric drive system.

[0013] Secondly, the application embodiment provides a detection system based on the detection method of the power module failure, which includes: A monitoring module is configured to monitor voltage data of a bus voltage in a pre-charging stage of a high-voltage system, and determine whether the voltage data exceeds a preset safety voltage threshold; A driving module is configured to control a driving circuit to alternately output a PWM driving signal with a set frequency and a set duty cycle to a lower bridge arm and an upper bridge arm of a power module to make the upper bridge arm and the lower bridge arm alternately conduct; a detection module configured to monitor whether a preset fault signal is detected within a set time during alternating conduction of the upper bridge arm and the lower bridge arm; a determination module configured to determine whether the power module is failed based on a detection result of the detection module.

[0014] In combination with the second aspect, in an implementation, the driving module comprises: an output unit configured to output the PWM driving signal; a control unit configured to control a frequency and a duty cycle of the PWM driving signal output by the output unit, and control the output unit to alternately output the PWM driving signal to the lower bridge arm and the upper bridge arm of the power module.

[0015] The technical scheme provided by the embodiments of the present application has the following beneficial effects: 1. The power module failure detection method and system, by controlling the driving current to output the PWM driving signal with a specific frequency and duty cycle, the upper bridge arm and the lower bridge arm are alternately conducted, so that whether the power module has the fault condition of the upper bridge arm or the lower bridge arm chip CE short circuit can be effectively identified, from the source, the serious safety accidents such as bridge arm through and secondary overcurrent caused by driving the failed power module are prevented, the safe operation of the high-voltage system is ensured, and the starting safety and operation reliability of the electric drive system are greatly improved.

[0016] 2. The power module failure detection method and system, the detection program can be automatically started at each vehicle pre-charging stage, compared with the traditional testing method using a multimeter and other tools, the power module can be quickly detected online without disassembling the motor controller, the detection efficiency is greatly improved, the detection time is shortened, and the operation safety of the vehicle is ensured.

[0017] 3. The power module failure detection method and system, only when the bus voltage rises to the preset safety voltage threshold during the pre-charging process, the detection is triggered, and the threshold is much lower than the rated working voltage of the high-voltage system, the design enables the entire detection process to be carried out at a lower bus voltage, reducing the voltage risk in the detection process and reducing the safety hazards that may be caused by high-voltage detection. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0019] Figure 1 The main steps of the present application are shown in the schematic diagram. Figure 2 Flow chart for detecting the present application; Figure 3 Power circuit diagram of high-voltage pre-charging circuit and motor controller in the embodiment of the present application; Figure 4 Principle diagram of power module failure detection circuit in the embodiment of the present application. DETAILED DESCRIPTION

[0020] In order to make the personnel in the technical field better understand the scheme of the present application, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor fall within the scope of protection of the present application.

[0021] Please refer to Figure 1 and Figure 2 The embodiment of the present application provides a detection method for power module failure, comprising the following steps: S1, monitoring the voltage data of the bus voltage in the pre-charging stage of the high-voltage system; In the embodiment, the voltage data of the bus voltage in the pre-charging stage of the high-voltage system is monitored by the motor controller. A safety voltage threshold is set in the control program of the motor controller to start the detection program. Specifically, as shown in Figure 3 , Fig. 1 is a motor. When the high voltage is powered on, the negative contactor (K-) and the pre-charging contactor (KP) are closed first. The high voltage VB output by the power battery pack charges the bus capacitor (C) through the pre-charging resistor (R). The voltage data of the bus voltage rises with time according to an exponential function. Based on the set safety voltage threshold, when the motor controller detects that the voltage data exceeds the set safety voltage threshold during the rising process of the voltage data of the bus voltage, the detection program is triggered. The pre-set safety voltage threshold is lower than the rated working voltage of the high-voltage system, so that the entire detection process can be carried out at a lower bus voltage, reducing the voltage risk in the detection process. At the same time, the pre-charging resistor (R) and the pre-charging contactor (KP) can protect the high-voltage loop and components, reducing the safety hidden danger that may be caused by high-voltage detection.

[0022] In addition, the pre-set safety voltage threshold of the embodiment is 100V, which can be adjusted according to the vehicle situation and actual demand.

[0023] S2, when the voltage data exceeds the preset safe voltage threshold, the motor controller controls the drive circuit to alternately output the PWM drive signal of the set frequency and set duty ratio to the lower bridge arm and the upper bridge arm of the power module, so that the upper bridge arm and the lower bridge arm are alternately turned on; Specifically, when the voltage data of the bus voltage exceeds the preset 100V: ①The motor controller will control the drive circuit to output the PWM drive signal of the set frequency and set duty ratio to all the switch tubes of the lower bridge arm of the power module, and keep all the switch tubes of the upper bridge arm turned off; ②The motor controller will control the drive circuit to output the PWM drive signal of the set frequency and set duty ratio to all the switch tubes of the upper bridge arm of the power module, and keep all the switch tubes of the lower bridge arm turned off; In this embodiment, the set frequency of the PWM drive signal is 10kHz, and the set duty ratio is 50%.

[0024] S3, in the process of alternately turning on the upper bridge arm and the lower bridge arm, whether the preset fault signal is detected within the set time is monitored; In this embodiment, the set time is preferably 50ms, which is counted by the timer in the motor controller. The set time can be adjusted according to the vehicle condition and actual demand.

[0025] The preset fault signal includes a bus under-voltage fault signal or a drive desaturation protection fault signal.

[0026] Please refer to Figure 4 The detection principle of the application is described in detail taking the CE short circuit failure of T1 device in IGBT module as an example: Case one: based on bus under-voltage fault for judgment: When the drive waveform controls the lower bridge arm switch tubes (T2, T4, T6) to be turned on at the same time, because the upper bridge arm (T1) is in the CE short circuit state, a low impedance path through the short-circuited (T1) and the turned-on (T2) is formed, which causes the bus capacitor (C) to be short-circuited and discharged. At this time, the bus voltage is rapidly pulled down to 0V, and the bus voltage monitoring unit of the motor controller detects that the voltage is lower than the under-voltage protection threshold, and immediately generates a bus under-voltage fault signal and reports to the main control chip of the motor controller, and accordingly the power module failure can be judged; Case two: based on drive desaturation protection fault for judgment: If the drive circuit of the motor controller has a desaturation protection function, when the gate drive voltage of the lower bridge arm (T2) under the drive waveform control is high, a through circuit is formed due to the short circuit of the upper bridge arm (T1), at this time, the current flowing through the lower bridge arm (T2) increases sharply, causing the collector-emitter voltage to rise rapidly and exit the saturation region, and the desaturation protection circuit of the drive chip detects that the voltage exceeds the internal set threshold, and immediately triggers the protection action, so that the drive circuit outputs a low level to turn off the lower bridge arm (T2), and reports a desaturation protection fault signal to the main control chip of the motor controller through the fault pin, and the power module failure can be judged accordingly.

[0027] S4, judging whether the power module is failed based on the detection result; Specifically, if any of the signals as mentioned in step S3 is captured within 50 ms, it is determined that the power module is failed; if not, it represents that the detection result is normal.

[0028] In addition, the steps of the detection method of the embodiment further include: S5, if it is judged that the power module is failed, taking a fault handling measure.

[0029] The fault handling measure includes sending a fault signal to the vehicle control unit, and the vehicle control unit receives the fault signal and controls the battery management system to cut off the power supply to the electric drive system; Specifically, when the motor controller receives the bus under-voltage fault signal or the drive desaturation protection fault signal, it will immediately send a fault information to the vehicle control unit, at this time, the vehicle central control screen will light up the fault indicator light or pop up a warning prompt to remind the driver to pay attention, at the same time, the vehicle control unit will control the battery management system to quickly disconnect the pre-charging contactor and the negative contactor, thereby cutting off the power supply of the power battery to the electric drive system, effectively preventing the fault from expanding, and ensuring the safety of the vehicle and personnel.

[0030] The embodiment also provides a detection system based on the detection method of the power module failure, which comprises: A monitoring module is configured to monitor the voltage data of the bus voltage in the pre-charging stage of the high-voltage system, and judge whether the voltage data exceeds 100 V; A drive module is configured to control the drive circuit of the motor controller to alternately output PWM drive signals with a set frequency and a set duty cycle to the lower bridge arm and the upper bridge arm of the power module so as to alternately turn on the lower bridge arm and the upper bridge arm; The drive module comprises an output unit configured to output the PWM drive signals; A control unit is configured to control the frequency and the duty cycle of the PWM drive signals output by the output unit, and control the output unit to alternately output the PWM drive signals to the lower bridge arm and the upper bridge arm of the power module; a detection module configured to monitor whether a bus under-voltage fault signal or a drive back-to-back protection fault signal is detected within 50 ms during the process of alternating on the upper bridge arm and the lower bridge arm; a determination module configured to determine whether the power module is failed based on the detection result of the detection module; if the bus under-voltage fault signal or the drive back-to-back protection fault signal is detected, it indicates that the power module has a fault, and if not, it represents that the detection result is normal; In addition, a processing module is further included, which is configured to perform fault processing based on the determination result of the determination module; if the power module has a fault, the processing module sends a fault signal to the vehicle control unit, and the vehicle control unit controls the battery management system to cut off the power supply to the electric drive system after receiving the fault signal.

[0031] Through the cooperation of the above modules, the faults such as the CE short circuit of the single bridge arm IGBT chip, which cannot be detected by the traditional operation protection mechanism, can be effectively identified, and the serious safety accidents such as the bridge arm short circuit and the secondary overcurrent caused by the drive of the failed power module are prevented from the source, the safe operation of the high-voltage system is ensured, and the starting safety and the operation reliability of the electric drive system are greatly improved.

[0032] In the description of the present application, it should be noted that the positions or position relationships indicated by the terms "upper", "lower" and the like are based on the positions or position relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] It should be noted that, in the present application, the relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0034] The foregoing is merely illustrative of the principles of the application and various modifications can be made by those skilled in the art without departing from the spirit and scope of the application. The above embodiments are illustrative, and not restrictive, of the scope of the application.

Claims

1. A method for detecting power module failure, characterized in that, Includes the following steps: Monitor the voltage data of the bus voltage during the pre-charge phase of the high-voltage system; When the voltage data exceeds the preset safe voltage threshold, the control drive circuit alternately outputs PWM drive signals with a set frequency and a set duty cycle to the lower and upper bridge arms of the power module, so that the upper and lower bridge arms are turned on alternately. During the alternating conduction of the upper and lower bridge arms, monitor whether a preset fault signal is detected within a set time period; Determine whether the power module has failed based on the test results.

2. The method for detecting power module failure according to claim 1, characterized in that, The preset safety voltage threshold is lower than the rated operating voltage of the high-voltage system.

3. The method for detecting power module failure according to claim 1, characterized in that, The preset safe voltage threshold is 100V.

4. The method for detecting power module failure according to claim 1, characterized in that, The control drive circuit alternately outputs PWM drive signals with a set frequency and a set duty cycle to the lower and upper bridge arms of the power module, so that the upper and lower bridge arms are alternately turned on, specifically including: The control drive circuit outputs a PWM drive signal with a set frequency and a set duty cycle to all the switches in the lower bridge arm of the power module, while keeping all the switches in the upper bridge arm off. The control drive circuit outputs a PWM drive signal with a set frequency and a set duty cycle to all the switches in the upper bridge arm of the power module, while keeping all the switches in the lower bridge arm off.

5. The method for detecting power module failure according to claim 1, characterized in that, The PWM drive signal is set to a frequency of 10kHz and a duty cycle of 50%.

6. The method for detecting power module failure according to claim 1, characterized in that, The preset fault signals include bus undervoltage fault signals or drive desaturation protection fault signals.

7. The method for detecting power module failure according to claim 1, characterized in that, After determining whether the power module has failed based on the detection results, the process also includes: If the power module is determined to be faulty, troubleshooting measures should be taken.

8. The method for detecting power module failure according to claim 7, characterized in that, The fault handling measures include sending a fault signal to the vehicle control unit, and after receiving the fault signal, the vehicle control unit controls the battery management system to cut off the power supply to the electric drive system.

9. A detection system based on the power module failure detection method of claim 1, characterized in that, include: The monitoring module is used to monitor the voltage data of the bus voltage during the pre-charging stage of the high-voltage system and determine whether it exceeds the preset safe voltage threshold. The drive module is used to control the drive circuit to alternately output PWM drive signals with a set frequency and a set duty cycle to the lower and upper bridge arms of the power module so that the upper and lower bridge arms are alternately turned on. The detection module is used to monitor whether a preset fault signal is detected within a set time during the alternating conduction of the upper and lower bridge arms. The determination module is used to determine whether the power module has failed based on the detection results of the detection module.

10. The detection system of the power module failure detection method according to claim 9, characterized in that, The driving module includes: The output unit is used to output PWM drive signals; The control unit is used to control the frequency and duty cycle of the PWM drive signal output by the output unit, and to control the output unit to alternately output PWM drive signals to the lower and upper bridge arms of the power module.

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