Fault processing strategy for extended-range electric vehicle

Abstract

The invention discloses a fault processing strategy for an extended-range electric vehicle, which is characterized in that for a whole vehicle control unit (hereinafter referred to as' VCU '), if an electric drive system or a range extender system or other systems have a high-grade fault, how to ensure driving safety and protect parts needs to be considered from the whole vehicle perspective, and when a serious fault occurs, high voltage needs to be delayed. Functional safety is integrated into a whole vehicle fault processing strategy of the extended-range electric vehicle, and a safety target of not generating unexpected accelerating force or decelerating force and a safety state of not generating direct current higher than 60V are set; high-grade faults of high voltage needing to be delayed and serious faults of an electric drive system and a power generation system are subjected to targeted analysis, decision making and execution according to actual scenes when the faults occur, driving safety is guaranteed to the maximum extent, meanwhile, protection of components of the electric drive system and components of the power generation system is also taken into consideration, overall consideration of people and vehicles is achieved, and the safety is improved. And the user can use the bicycle more securely.

Description

Technical Field

[0001] The present invention relates to the field of vehicle control technology, and in particular to a fault handling strategy for an extended-range electric vehicle. Background Art

[0002] For new energy vehicles, besides battery life and vehicle economy, safety is a common concern. In addition to the problem of battery thermal runaway, the electric drive system, as one of the core components for the whole vehicle to achieve drive and electric braking, also has many safety issues that require extra attention. It plays an important role in the driving safety of the whole vehicle, especially when the motor and electronic control fail. If the control strategy is not considered comprehensively, it will affect driving safety, and in serious cases even endanger the lives of the driver and passengers.

[0003] In addition to the electric drive system, the range extender system of extended-range electric vehicles also includes a generator and a generator controller (hereinafter referred to as "GCU"), so high-voltage safety needs to be considered more comprehensively. For new energy commercial vehicles, the products are aimed at ordinary commercial vehicle users, and the electric drive system fault handling ideas are generally simpler. The safety goals and safety states in the functional safety requirements are not fully considered. The impact brought about by this is that when the vehicle's electric drive system fails, the post-fault handling strategy adopted by the motor controller (hereinafter referred to as "MCU") may protect the electric drive components, but it fails to take into account driving safety, or it considers driving safety but fails to fully protect the components. These have buried safety hazards for both people and vehicles. Summary of the invention

[0004] The present invention provides a fault handling strategy for an extended-range electric vehicle, which maximizes driving safety while also taking into account the protection of electric drive system components and power generation system components, thereby achieving a comprehensive consideration of both people and vehicles and allowing users to use the vehicle with greater peace of mind.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a fault handling strategy for extended-range electric vehicles. For the vehicle control unit (hereinafter referred to as "VCU"), if a high-level fault occurs in the electric drive system, the range extender system or other systems, it is necessary to consider how to ensure driving safety and protect components from the perspective of the entire vehicle. When a serious fault occurs and it is necessary to delay the reduction of high voltage, the VCU will judge the speed of the electric drive system and the power generation power of the range extender system. The high voltage operation will be lowered only when the speed of the electric drive system is lower than the threshold and if the range extender is generating electricity, the power generation power of the range extender is also lower than the threshold. Otherwise, the high voltage will be directly reduced when the time exceeds the threshold.

[0006] Preferably, the lower high pressure control strategy is specifically: Step S10, power-on initialization, power-on high voltage ready operation; Step S20, real-time monitoring of the vehicle fault handling system; Step S30, determining whether a serious fault alarm requires a delay in lowering the high voltage, if yes, proceed to step S40, if no, repeat this step; Step S40, the VCU sends a zero torque command to the MCU; Step S50, whether the APU is in power generation state, if yes, proceed to step S60, if no, proceed to step S80; Step S60, the VCU sends a zero power generation instruction to the GCU; Step S70, determine whether the power generation is less than 2kw, if yes, proceed to step S80, if no, repeat the current step; Step S80, determining whether the speed of the driving motor is lower than 200 rpm, if yes, proceed to step S90, if no, repeat this step; Step S90, VCU controls the lower voltage.

[0007] Preferably, the electric drive system fault handling strategy comprises the following specific steps: Step S100, high voltage operation on the whole vehicle; Step S200, determining whether a serious fault occurs in the electric drive system, if so, proceeding to step S300, if not, repeating this step; Step S300, determine whether the high and low voltage connections are normal, if yes, proceed to step S400, if not, proceed to step S500; Step S400, MCU performs zero torque control; Step S500, determining whether the motor speed is lower than a threshold value, if yes, proceed to step S600, if no, proceed to step S700; Step S600, MCU performs shutdown control; Step S700: MCU executes stator three-phase short-circuit control.

[0008] Preferably, the range extender power generation system fault handling strategy specifically includes the following steps: Step S1000, high voltage operation on the whole vehicle; Step S2000, determining whether the APU is in power generation operation state, if so, proceed to step S3000, if not, repeat this step; Step S3000, determine whether a serious fault occurs in the GCU or the engine, if so, proceed to step S4000, if not, repeat this step; Step S4000, determine whether the high and low voltage connections are normal, if yes, proceed to step S5000, if not, proceed to step S6000; Step S5000, the GCU performs zero torque control; Step S6000: GCU performs shutdown control.

[0009] The beneficial effects of adopting the above technical solution are: 1. The present invention integrates functional safety into the whole vehicle fault handling strategy of the extended-range electric vehicle. By setting the safety goal of not generating unexpected acceleration force or deceleration force and the safety state of not generating direct current higher than 60V, targeted analysis, decision-making and execution are carried out according to the actual scenario when high-level faults that require delayed high voltage and serious faults of the electric drive system and the power generation system occur, so as to maximize driving safety. At the same time, it also takes into account the protection of the electric drive system components and the power generation system components, realizes the overall consideration of people and vehicles, and makes users feel more at ease when using the car.

[0010] 2. In the present invention, when a serious fault occurs and the high voltage needs to be delayed, the VCU will judge the rotation speed of the electric drive system and the power generation power of the range extender system. The high voltage operation will be performed only when the rotation speed of the electric drive system is lower than the threshold and if the range extender is generating electricity, the power generation power of the range extender is also lower than the threshold. Otherwise, the high voltage will be directly lowered when the time exceeds the threshold to prevent the direct disconnection of the DC high voltage connection from causing high back electromotive force to cause impact damage to the power devices of the drive system and the power generation system, and also to avoid the main positive relay in the battery pack being disconnected under load, causing arcing and ignition to damage the main positive relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a diagram of the fault handling architecture for an extended-range electric vehicle; Figure 2 This is the overall control flow chart of the high-pressure control strategy of the present invention; Figure 3 This is a flow chart of the electric drive system fault handling strategy of the present invention; Figure 4 This is a flow chart of the fault handling strategy of the range extender power generation system of the present invention. DETAILED DESCRIPTION

[0012] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0013] like Figures 1 to 4 As shown, the present invention is a fault handling strategy for extended-range electric vehicles that maximizes driving safety, while also taking into account the protection of electric drive system components and power generation system components, achieving a comprehensive consideration of both people and vehicles, and allowing users to use the vehicle with greater peace of mind. Example 1

[0014] Specifically, Figures 1 to 4As shown, for the vehicle control unit (hereinafter referred to as "VCU"), if a high-level fault occurs in the electric drive system, the range extender system or other systems, it is necessary to consider how to ensure driving safety and protect components from the perspective of the entire vehicle. When a serious fault occurs and it is necessary to delay the release of high voltage, the VCU will judge the speed of the electric drive system and the power generation power of the range extender system. The high voltage operation will be performed only when the speed of the electric drive system is lower than the threshold and if the range extender is generating electricity, the power generation power of the range extender is also lower than the threshold. Otherwise, the high voltage will be directly released when the time exceeds the threshold.

[0015] The specific control strategy for lower high pressure is as follows: Step S10, power-on initialization, power-on high voltage ready operation; Step S20, real-time monitoring of the vehicle fault handling system; Step S30, determining whether a serious fault alarm requires a delay in lowering the high voltage, if yes, proceed to step S40, if no, repeat this step; Step S40, the VCU sends a zero torque command to the MCU; Step S50, whether the APU is in power generation state, if yes, proceed to step S60, if no, proceed to step S80; Step S60, the VCU sends a zero power generation instruction to the GCU; Step S70, determine whether the power generation is less than 2kw, if yes, proceed to step S80, if no, repeat the current step; Step S80, determining whether the speed of the driving motor is lower than 200 rpm, if yes, proceed to step S90, if no, repeat this step; Step S90, VCU controls the lower voltage.

[0016] The specific steps of the electric drive system fault handling strategy are as follows: Step S100, high voltage operation on the whole vehicle; Step S200, determining whether a serious fault occurs in the electric drive system, if so, proceeding to step S300, if not, repeating this step; Step S300, determine whether the high and low voltage connections are normal, if yes, proceed to step S400, if not, proceed to step S500; Step S400, MCU performs zero torque control; Step S500, determining whether the motor speed is lower than a threshold value, if yes, proceed to step S600, if no, proceed to step S700; Step S600, MCU performs shutdown control; Step S700: MCU executes stator three-phase short-circuit control.

[0017] The fault handling strategy of the range extender power generation system includes the following steps: Step S1000, high voltage operation on the whole vehicle; Step S2000, determining whether the APU is in power generation operation state, if so, proceed to step S3000, if not, repeat this step; Step S3000, determine whether a serious fault occurs in the GCU or the engine, if so, proceed to step S4000, if not, repeat this step; Step S4000, determine whether the high and low voltage connections are normal, if yes, proceed to step S5000, if not, proceed to step S6000; Step S5000, the GCU performs zero torque control; Step S6000: GCU performs shutdown control. Example 2

[0018] If the MCU has a three-phase zero drift fault, or a short power or short ground fault in the two-resistance current sampling sensor, or a resolver fault, these faults are mainly hardware faults that affect the control implementation of FOC. At this time, normal torque control is no longer possible. Therefore, the MCU needs to cancel the power output in time to ensure driving safety.

[0019] The above fault and other faults of the same type should be analyzed based on the vehicle speed status (single gear box) or the motor speed before the fault occurs (multi-gear box has neutral gear configuration). If the vehicle speed is available, then when the vehicle is in high-speed operation, such as high-speed cruising, and the above fault occurs, the motor should be controlled to enter the upper three bridge arms open state or the lower three bridge arms open state. When the upper three bridge arms are open, the lower three bridge arms are closed, and when the lower three bridge arms are open, the upper three bridge arms are closed.

[0020] In order to protect the safety of the driver and the components of the electric drive system, the power switch of the upper three-bridge arm or the lower three-bridge arm of the MCU is opened at this time to short-circuit the three-phase winding of the motor stator. When the three-phase winding of the stator is short-circuited, the back electromotive force of the motor will be forced to zero. Therefore, the back electromotive force of the electric drive system will not be higher than the safety voltage of 60V specified in the national standard, thus achieving functional safety status.

[0021] After short-circuiting the three-phase winding, the back electromotive force of the motor will be dissipated in the form of heat. Since the vehicle has no driving force, the speed will drop quickly. When the speed decreases, the motor and the wheel are rigidly connected, and the motor speed also decreases synchronously. The back electromotive force of the motor is strongly positively correlated with the motor speed. Therefore, after the motor speed drops rapidly, the heat generated also gradually decreases, which has little or no effect on the stator winding life, insulation thermal aging, etc.

[0022] The active safety strategy of stator three-phase winding short circuit will have a large braking torque when the motor speed is low. This braking torque will cause unexpected deceleration of the vehicle, so there is a certain threat to the functional safety goal. Therefore, after the motor speed is lower than the threshold (such as the inflection point), the active safety control strategy of stator three-phase winding short circuit is no longer applicable.

[0023] It should be noted that when the three-phase stator winding is short-circuited, the short-circuit current is large. At this time, the software overcurrent fault should be shielded to prevent the three-phase short-circuit current from exceeding the overcurrent fault threshold and causing a false fault alarm.

[0024] When the motor speed is lower than the inflection point speed, active safety control can be performed by turning off all six power switches (such as IGBTs) of the three-phase full bridge. At this time, the back electromotive force generated by the motor will be rectified by the anti-parallel diode of the IGBT.

[0025] In the off state, the PWM duty cycle is not actively controlled to achieve control of the stator winding current. Therefore, it is an uncontrollable rectification state. The motor speed is below the inflection point, and the motor's back electromotive force will not be higher than the bus voltage. Therefore, the DC side voltage after rectification is still lower than the bus voltage.

[0026] The rectified voltage is lower than the bus voltage because the rectified voltage cannot flow to the DC bus. The voltage of the DC bus cannot flow to the AC side because of the reverse parallel diode. Therefore, the AC and DC sides are actually in an open-circuit and no-load state. Therefore, the back electromotive force will not be rectified and charged into the battery. At this time, the back electromotive force will directly act on the motor's voltage-stabilizing capacitor and IGBT. Since the back electromotive force is lower than the bus voltage, it is within the normal working voltage range and will not cause impact or damage to the voltage-stabilizing capacitor and IGBT.

[0027] Shut-off control is suitable for scenarios where the motor speed is not high, because it will not generate charging current to cause the kinetic energy of the vehicle to decrease, resulting in unexpected deceleration of the vehicle. If the motor speed is higher than the inflection point, the back electromotive force generated by the motor is higher than the bus voltage when the speed is high. If the DC side of the inverter is not disconnected from the DC bus end, shutting off the control will cause the motor back electromotive force to be higher than the bus voltage after rectification, and the rectified DC voltage will be pressed into the battery. According to the law of conservation of energy, the kinetic energy of the vehicle will decrease, causing unexpected deceleration of the vehicle, affecting the driving safety of the vehicle, and causing driving hazards in severe cases.

[0028] If the inverter is disconnected from the DC bus, the voltage drop after rectification will directly act on the voltage stabilizing capacitor and power devices. After the capacitor is charged to saturation, it will have a risk of breakdown if it acts for a long time, and in serious cases, it will also damage the power devices. Therefore, when the motor speed is higher than the inflection point, the shutdown control cannot be used for active safety control, otherwise there will be certain risks to the driving safety of the whole vehicle and its components.

[0029] If the high and low voltage connections of the vehicle are normal, then when the motor fails and cannot be driven normally, such as motor overspeed, overheating, disconnection and other faults, zero torque control can be adopted to cancel the torque output to prevent acceleration or deceleration output that is contrary to the driver's intention.

[0030] Zero torque control is based on the vector control framework, which requests the quadrature-axis current to be zero, that is, the reference current of the quadrature-axis current is zero. The coordinate transformation is performed on the current sampled by the ADC current to obtain the measured equivalent quadrature-axis current, and then the closed-loop control of the rotor torque is performed.

[0031] If the low-voltage power supply is disconnected, signal acquisition for low-voltage control, such as current ADC sampling, will not be possible. If the DC high-voltage side is disconnected, SVPWM wave control will not be able to be effectively performed.

[0032] Zero torque control is more friendly to electric drive and the whole vehicle than stator three-phase short circuit and shut-off. Therefore, when conditions permit, zero torque control should be preferred. Since stator three-phase short circuit will have a larger braking torque at low speed, it is suitable for use in scenarios where a fault occurs and the motor speed is high. When the motor speed is high, if the DC side is not disconnected, that is, the whole vehicle is not in a high-voltage state, then an energy recovery effect will occur, resulting in unexpected deceleration of the whole vehicle. The higher the motor speed, the greater the deceleration.

[0033] In addition, when the three-phase stator is short-circuited, considering that this working state is likely to cause overheating of the motor or MCU, a method of alternating stator three-phase short-circuit and zero torque control can be designed in the high-speed area to achieve safety goals and prevent overheating from causing damage to power devices such as IGBTs.

[0034] For the generator and GCU in the range extender, when their own software and hardware failures occur, active safety control, such as zero torque and shut-off, must also be considered for the protection of their own components. The range extender system of an extended-range electric vehicle is only responsible for power generation, and there is no mechanical connection between the generator and the drive end. Therefore, there is no need to consider the active safety control of the generator and GCU to produce unexpected acceleration or deceleration that affects driving safety.

[0035] Therefore, for the generator and GCU in the range extender of the extended-range electric vehicle, when related faults occur, it is only necessary to select zero torque or shutdown control according to the specific fault, without entering the stator three-phase short-circuit control state, which can prevent the stator three-phase short-circuit heat from affecting the life of the power device.

[0036] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above-mentioned concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A fault handling strategy for an extended-range electric vehicle, characterized in that: For the vehicle control unit (hereinafter referred to as "VCU"), if a high-level fault occurs in the electric drive system, the range extender system or other systems, it is necessary to consider how to ensure driving safety and protect components from the perspective of the entire vehicle. When a serious fault occurs and it is necessary to delay the reduction of high voltage, the VCU will judge the speed of the electric drive system and the power generation power of the range extender system. The high voltage operation will be performed only when the speed of the electric drive system is lower than the threshold and if the range extender is generating electricity, the power generation power of the range extender is also lower than the threshold. Otherwise, the high voltage will be directly reduced when the time exceeds the threshold.

2. A fault handling strategy for an extended-range electric vehicle according to claim 1, characterized in that: The lower high pressure control strategy is specifically as follows: Step S10, power-on initialization, power-on high voltage ready operation; Step S20, real-time monitoring of the vehicle fault handling system; Step S30, determining whether a serious fault alarm requires a delay in lowering the high voltage, if yes, proceed to step S40, if no, repeat this step; Step S40, the VCU sends a zero torque command to the MCU; Step S50, whether the APU is in power generation state, if yes, proceed to step S60, if no, proceed to step S80; Step S60, the VCU sends a zero power generation instruction to the GCU; Step S70, determine whether the power generation is less than 2kw, if yes, proceed to step S80, if no, repeat the current step; Step S80, determining whether the speed of the driving motor is lower than 200 rpm, if yes, proceed to step S90, if no, repeat this step; Step S90, VCU controls the lower voltage.

3. A fault handling strategy for an extended-range electric vehicle according to claim 1, characterized in that: The specific steps of the electric drive system fault handling strategy are as follows: Step S100, high voltage operation on the whole vehicle; Step S200, determining whether a serious fault occurs in the electric drive system, if so, proceeding to step S300, if not, repeating this step; Step S300, determining whether the high and low voltage connections are normal, if yes, proceed to step S400, if no, proceed to step S500; Step S400, MCU performs zero torque control; Step S500, determining whether the motor speed is lower than a threshold value, if yes, proceed to step S600, if no, proceed to step S700; Step S600, MCU performs shutdown control; Step S700: MCU executes stator three-phase short-circuit control.

4. The extended-range electric vehicle fault handling strategy according to claim 1, characterized in that: The range extender power generation system fault handling strategy specifically includes the following steps: Step S1000, high voltage operation on the whole vehicle; Step S2000, determining whether the APU is in power generation operation state, if yes, proceed to step S3000, if no, repeat this step; Step S3000, determine whether a serious fault occurs in the GCU or the engine, if so, proceed to step S4000, if not, repeat this step; Step S4000, determine whether the high and low voltage connections are normal, if yes, proceed to step S5000, if not, proceed to step S6000; Step S5000, the GCU performs zero torque control; Step S6000: GCU performs shutdown control.

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