A method for detecting insulation of a hybrid fuel cell vehicle

Abstract

This invention discloses an insulation detection method for hybrid fuel cell vehicles, comprising: after the VCU is powered on, detecting the closed state of the high-voltage circuit relay; the BMS performs insulation detection on the high-voltage circuit of the power battery, obtaining a first insulation detection value and feeding it back to the VCU; then, based on any one of the current vehicle power demand, the maximum output power of the power battery, and the power battery voltage, switching between pure electric and hybrid modes, and selecting only one of the BMS or the FCU to perform insulation detection; the VCU compares the received insulation detection value with a preset insulation alarm threshold; when the insulation detection value is lower than the alarm threshold, it issues an insulation fault alarm signal and executes forced pure electric mode or power-limited operation according to the current operating mode. This invention solves the problem of false power-off of the vehicle caused by inaccurate detection of the high voltage section of the power battery, while improving the life of the fuel cell and the high-voltage safety of the vehicle.

Description

Technical Field

[0001] This invention relates to the technical field of vehicle insulation testing methods, and particularly to an insulation testing method for hybrid fuel cell vehicles. Background Technology

[0002] New energy vehicle power systems generally have high voltage and high current characteristics, with operating voltages far exceeding those safe for the human body. Therefore, vehicles must monitor the insulation resistance of high-voltage circuits in real time. When the insulation resistance falls below the alarm threshold, a warning should be immediately issued to the driver, and a high-voltage reduction procedure should be performed to prevent the risk of electric shock.

[0003] During the actual vehicle development process, it was discovered that when the power battery voltage exceeds 528V, the battery's built-in insulation detection module is prone to detection drift, leading to inaccurate insulation resistance measurements. This can falsely trigger insulation faults, forcing the entire vehicle to shut down and preventing it from operating normally. Furthermore, prematurely activating the fuel cell when the power battery's state of charge (SOC) is high may cause overcharging of the power battery.

[0004] On the other hand, frequent start-ups and shutdowns of fuel cell systems due to inadequate insulation detection strategies will significantly shorten their lifespan. Therefore, ensuring the reliability of insulation detection under high-voltage conditions while avoiding frequent start-ups and shutdowns of fuel cells has become an urgent problem to be solved. Summary of the Invention

[0005] To address the above problems, this invention provides an insulation testing method for hybrid fuel cell vehicles, the specific technical solution of which is as follows:

[0006] S1: After power-on, the vehicle controller detects the closed state of the high-voltage circuit relay and waits for a first set time before sending a first insulation detection invitation signal to the power battery controller. The power battery controller then controls the power battery insulation detection module to perform insulation detection on the high-voltage circuit of the power battery, obtains the first insulation detection value, and feeds it back to the vehicle controller.

[0007] S2: The vehicle controller switches between pure electric mode and hybrid mode based on any one of the current vehicle power demand, the maximum output power of the power battery, and the power battery voltage, and controls the power battery insulation detection module or the fuel cell insulation detection module to perform insulation detection.

[0008] S3: The vehicle controller compares the received insulation detection value with the preset insulation alarm threshold. When the insulation detection value is lower than the alarm threshold, it issues an insulation fault alarm signal and executes forced pure electric mode or power-limited operation according to the current operating mode.

[0009] Furthermore, in step S2, the mode switching is as follows:

[0010] When the vehicle is in pure electric mode, the BMS continues to control the insulation detection module to detect the insulation status of the high-voltage circuit of the vehicle. When the insulation signal value of the BMS is lower than the set threshold, the VCU controls the vehicle to enter hybrid mode.

[0011] In hybrid mode, the VCU wakes up the FCU, the FCU starts the fuel cell battery system, and after the VCU receives the fuel cell start-up completion signal from the FCU, the VCU invites the FCU to perform insulation detection. The FCU controls the fuel cell system to perform insulation detection, the VCU receives the insulation detection value from the FCU, and if the insulation signal value from the FCU is determined to be lower than the set threshold, the VCU forces the vehicle to enter forced pure electric mode.

[0012] Furthermore, in step S2, in pure electric mode, the following is also included:

[0013] When the vehicle controller determines that the power battery voltage has risen and reached the first voltage threshold, it switches from pure electric mode to hybrid mode. The vehicle controller wakes up the fuel cell controller and waits for the fuel cell system to start up before sending a second insulation detection invitation signal to the fuel cell controller. The fuel cell controller then controls the fuel cell insulation detection module to perform insulation detection on the fuel cell high-voltage circuit and feeds back the second insulation detection value to the vehicle controller.

[0014] When the vehicle controller determines that the power battery voltage has dropped below the second voltage threshold, it switches from hybrid mode to pure electric mode. The vehicle controller then sends a first insulation detection invitation signal to the power battery controller (BMS) and stops the insulation detection of the fuel cell controller. The second voltage threshold is lower than the first voltage threshold.

[0015] Furthermore, the first voltage threshold is dynamically adjusted by the vehicle controller based on the rate of increase of the power battery voltage, and is calculated as follows:

[0016] V1 = 528.5V–dv×4–α

[0017] Where dv is the voltage rise rate and α is the actual vehicle calibration correction.

[0018] Furthermore, when the vehicle controller detects that the power battery voltage exceeds the first voltage threshold and the power battery SOC exceeds the first SOC threshold, the vehicle controller increases the power consumption of the vehicle accessories and issues a request to increase the power usage of the accessories.

[0019] Furthermore, when the SOC of the power battery continues to rise to the second SOC threshold, the vehicle controller controls the vehicle to operate with reduced power and issues a parking warning, wherein the second SOC threshold is higher than the first SOC threshold.

[0020] Furthermore, when the vehicle controller detects a fault or abnormal detection value in the system currently performing insulation testing, it immediately switches to another insulation testing system to perform insulation testing.

[0021] Furthermore, when switching to hybrid mode, and during the insulation detection module's insulation detection, the vehicle controller sends a fuel cell power demand request to the fuel cell controller based on the difference between the vehicle's required power and the battery's maximum output power, thus:

[0022] When the power demand of the vehicle exceeds the maximum output power of the power battery, the vehicle controller controls the fuel cell to output power of no less than 25kW.

[0023] When the vehicle's required power is less than or equal to the maximum output power of the power battery, the vehicle controller controls the fuel cell to operate at minimum power, and after operating at minimum power for a second set time, switches to high power operation for a third set time.

[0024] Furthermore, the minimum power is 1-2kW, and the high power is 25kW.

[0025] Furthermore, the second set time is 10 minutes, and the third set time is 1 minute.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. This invention uses VCU to coordinate the BMS and FCU to perform insulation detection, and switches to fuel cell side detection when the voltage is higher than the first threshold and switches back to power battery side detection when the voltage is lower than the second threshold, forming hysteresis control. This solves the problem of false power-off caused by inaccurate detection of the power battery in the high voltage range, and avoids frequent start-stop of the fuel cell, which significantly improves the high voltage safety of the whole vehicle and the life of the fuel cell.

[0028] 2. This invention corrects the switching point in real time according to the voltage rise rate, realizes dynamic adjustment of the first voltage threshold, and prevents the fuel cell from starting too early or too late; at the same time, it sets a hysteresis dual threshold mechanism with the second voltage threshold lower than the first threshold to eliminate the jitter in the switching critical zone and reduce the number of fuel cell start-stop cycles.

[0029] 3. This invention sets a SOC threshold judgment. During the minimum power operation of the fuel cell, if the SOC exceeds the set threshold, the VCU will actively increase the power consumption of the accessories and prompt the driver. If necessary, it will reduce the power and prompt the driver to pull over to prevent the power battery from being overcharged and extend the battery life. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention are clearly and completely described in the following description. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] In the description of the embodiments of the present invention, it should be noted that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is conventionally placed during use, or the orientation or positional relationship in which those skilled in the art conventionally understand it during use. This is only for the convenience of describing the present invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. Furthermore, the terms "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0034] Example 1

[0035] Embodiment 1 of this invention discloses an insulation detection method for a hybrid fuel cell vehicle, applied to a new energy vehicle power system. The system includes a power battery system, a power battery controller (BMS), a power battery insulation detection module, a fuel cell system, a fuel cell controller (FCU), a fuel cell boost system (FDC), a multi-function controller, a power motor, and a motor controller. The power motor, motor controller, multi-function controller, fuel cell boost system, fuel cell system, and power battery system are connected via high-voltage lines. The power battery insulation detection module can detect the insulation resistance value of the high-voltage circuit forming a closed loop with the power battery. The fuel cell system insulation detection module can detect the insulation resistance value of the high-voltage circuit forming a closed loop with the fuel cell system. The FCU controls the fuel cell insulation detection module to perform insulation detection and receives information, and the BMS controls the battery to perform insulation detection and receives its information. The multi-function controller powers on the high-voltage relay and controls the drive motor to operate. The BMS, FCU, and multi-function controller communicate with the VCU via a CAN bus and hardwired connection to achieve real-time interaction of insulation detection invitation signals, insulation detection values, and fault status information.

[0036] like Figure 1 As shown, the specific method is as follows:

[0037] S1: After power-on, the vehicle controller (VCU) checks the closed state of the high-voltage circuit relay and waits for 40 seconds before sending the first insulation test invitation signal to the BMS. The BMS then controls the power battery insulation test module to perform insulation test on the high-voltage circuit of the power battery, obtains the first insulation test value, and feeds it back to the VCU. The VCU determines whether the vehicle is fault-free based on the vehicle status information and the insulation test value. If not, it determines that the high voltage connection is complete and the vehicle is in a ready state.

[0038] Specifically, the first set time is calibrated based on the power-on completion time of the vehicle system, and is not specifically limited here. In this embodiment, the first set time is set to 40 seconds for a delay to ensure that the high-voltage system completes pre-charging and self-test.

[0039] S2: The VCU switches between pure electric mode and hybrid mode based on any one of the current vehicle power demand, the maximum output power of the power battery, and the power battery voltage, and controls the power battery insulation detection module or fuel cell insulation detection module to perform insulation detection.

[0040] Specifically, if the power battery and fuel cell are tested for insulation at the same time, the results will be inaccurate. Therefore, in this embodiment, the VCU only invites one of the two system components to perform insulation testing.

[0041] In pure electric mode, the BMS continues to control the insulation detection module to detect the insulation status of the vehicle's high-voltage circuit. When the insulation signal value of the BMS is lower than the set threshold, the VCU controls the vehicle to enter hybrid mode.

[0042] In hybrid mode, the VCU wakes up the FCU, the FCU starts the fuel cell battery system, and after receiving the fuel cell start-up completion signal from the FCU (during the fuel cell start-up process, the insulation detection module is controlled by the BMS to perform insulation detection), the VCU invites the FCU to perform insulation detection. The FCU controls the fuel cell system to perform insulation detection, and the VCU receives the insulation detection value from the FCU. If the insulation signal value from the FCU is determined to be lower than the set threshold, the VCU forces the vehicle to enter forced pure electric mode: that is, the VCU sends an insulation detection invitation signal to the BMS, sends a fuel cell system shutdown or idle stop signal to the FCU, and the vehicle instrument panel displays insulation detection warning information and alarm signals.

[0043] In this embodiment, in pure electric mode, when the VCU determines that the power battery voltage has risen and reached the first voltage threshold, the VCU switches from pure electric mode to hybrid mode. The VCU wakes up the FCU and waits for the fuel cell system to start up before sending a second insulation detection invitation signal to the FCU. The FCU controls the fuel cell insulation detection module to perform insulation detection on the high-voltage circuit of the fuel cell and feeds back the second insulation detection value to the VCU.

[0044] During actual vehicle operation, when the BMS voltage exceeds 528.5V, the insulation resistance detection becomes inaccurate, and the resistance value is prone to drift. In severe cases, this can lead to insulation failure, causing the entire vehicle to lose power and become inoperable. If the fuel cell is started prematurely when the BMS's SOC is too high, it may cause overcharge to the power battery. Before reaching the inaccurate voltage value, insulation detection needs to be switched to FCU detection. The fuel cell's power-on completion time is approximately 4 seconds, and the switch from insulation detection to FCU detection can be performed within 4 seconds. By calibrating different thresholds based on the voltage rise rate, that is, when the voltage is below 528.5V, different thresholds are selected according to different voltage rise rates, achieving dynamic selection of the first voltage threshold.

[0045] In a preferred embodiment, the first voltage threshold is calculated as follows:

[0046] V1 = 528.5V–dv×4–α

[0047] Where dv is the voltage rise rate and α is the actual vehicle calibration correction to prevent the fuel cell from starting too early or too late.

[0048] In this embodiment, when the VCU detects that the power battery voltage exceeds the first voltage threshold and the power battery SOC exceeds the first SOC threshold, the VCU increases the power consumption of the vehicle accessories and sends a request to the driver to increase the use of accessory power in order to reduce the SOC rise rate.

[0049] When the SOC of the power battery continues to rise to the second SOC threshold, the VCU controls the vehicle to operate with reduced power and sends a parking reminder to the instrument panel. The second SOC threshold is higher than the first SOC threshold.

[0050] When the VCU determines that the power battery voltage has dropped below the second voltage threshold, the VCU returns from hybrid mode to pure electric mode, sends the first insulation detection invitation signal to the BMS again, and stops the insulation detection of the FCU. The second voltage threshold is lower than the first voltage threshold to form hysteresis control and prevent the fuel cell system from starting and stopping frequently.

[0051] In a preferred embodiment, when switching to hybrid mode and the FCU performs insulation detection, the VCU sends a fuel cell power demand request to the FCU based on the difference between the vehicle's required power and the maximum output power of the power battery, such that:

[0052] When the power demand of the vehicle exceeds the maximum output power of the power battery, the VCU controls the fuel cell to output power of no less than 25kW.

[0053] When the power demand of the vehicle is less than or equal to the maximum output power of the power battery, the VCU controls the fuel cell to operate at the minimum power (1-2kW), and after operating at the minimum power for a second set time (10min), it switches to high power (25kW) for a third set time (1min), and repeats this cycle to prevent the power battery SOC from continuously increasing.

[0054] S3: The VCU compares the received insulation detection value with the preset insulation alarm threshold. When the insulation detection value is lower than the alarm threshold, it issues an insulation fault alarm signal and executes forced pure electric mode or power-limited operation according to the current operating mode to ensure the high-voltage safety of the whole vehicle.

[0055] As a preferred embodiment, when the VCU detects a fault or abnormal detection value in the system currently performing insulation testing, it immediately switches to another insulation testing system to perform insulation testing, so as to ensure the continuous insulation monitoring capability of the vehicle's high-voltage circuit.

[0056] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. An insulation testing method for a hybrid fuel cell vehicle, characterized in that, include: S1: After power-on, the vehicle controller detects the closed state of the high-voltage circuit relay and waits for a first set time before sending a first insulation detection invitation signal to the power battery controller. The power battery controller then controls the power battery insulation detection module to perform insulation detection on the high-voltage circuit of the power battery, obtains the first insulation detection value, and feeds it back to the vehicle controller. S2: The vehicle controller switches between pure electric mode and hybrid mode based on any one of the current vehicle power demand, the maximum output power of the power battery, and the power battery voltage, and controls the power battery insulation detection module or the fuel cell insulation detection module to perform insulation detection. In pure electric mode, it also includes: When the vehicle controller determines that the power battery voltage has risen and reached the first voltage threshold, it switches from pure electric mode to hybrid mode. The vehicle controller wakes up the fuel cell controller and waits for the fuel cell system to start up before sending a second insulation detection invitation signal to the fuel cell controller. The fuel cell controller then controls the fuel cell insulation detection module to perform insulation detection on the fuel cell high-voltage circuit and feeds back the second insulation detection value to the vehicle controller. When the vehicle controller determines that the battery voltage has dropped below the second voltage threshold, it switches from hybrid mode to pure electric mode. The vehicle controller then sends a first insulation detection invitation signal to the battery management system (BMS) and stops the insulation detection of the fuel cell controller. The second voltage threshold is lower than the first voltage threshold. S3: The vehicle controller compares the received insulation detection value with the preset insulation alarm threshold. When the insulation detection value is lower than the alarm threshold, it issues an insulation fault alarm signal and executes forced pure electric mode or power-limited operation according to the current operating mode.

2. The insulation testing method for hybrid fuel cell vehicles according to claim 1, characterized in that, In step S2, the mode switching is as follows: When the vehicle is in pure electric mode, the BMS continues to control the insulation detection module to detect the insulation status of the high-voltage circuit of the vehicle. When the insulation signal value of the BMS is lower than the set threshold, the VCU controls the vehicle to enter hybrid mode. In hybrid mode, the VCU wakes up the FCU, the FCU starts the fuel cell battery system, and after the VCU receives the fuel cell start-up completion signal from the FCU, the VCU invites the FCU to perform insulation detection. The FCU controls the fuel cell system to perform insulation detection, the VCU receives the insulation detection value from the FCU, and if the insulation signal value from the FCU is determined to be lower than the set threshold, the VCU forces the vehicle to enter forced pure electric mode.

3. The insulation testing method for hybrid fuel cell vehicles according to claim 1, characterized in that, The first voltage threshold is dynamically adjusted by the vehicle controller based on the rate of rise of the power battery voltage, and is calculated as follows: V1 = 528.5V–dv×4–α Where dv is the voltage rise rate and α is the actual vehicle calibration correction.

4. The insulation testing method for a hybrid fuel cell vehicle according to claim 1, characterized in that, When the vehicle controller detects that the power battery voltage exceeds the first voltage threshold and the power battery SOC exceeds the first SOC threshold, the vehicle controller increases the power consumption of the vehicle accessories and issues a request to increase the power usage of the accessories.

5. The insulation testing method for a hybrid fuel cell vehicle according to claim 4, characterized in that, When the SOC of the power battery continues to rise to the second SOC threshold, the vehicle controller controls the vehicle to operate with reduced power and issues a parking warning. The second SOC threshold is higher than the first SOC threshold.

6. The insulation testing method for a hybrid fuel cell vehicle according to claim 1, characterized in that, When the vehicle controller detects a fault or abnormal detection value in the system currently performing insulation testing, it immediately switches to another insulation testing system to perform insulation testing.

7. The insulation testing method for a hybrid fuel cell vehicle according to any one of claims 1-6, characterized in that, When switching to hybrid mode, and the fuel cell insulation detection module performs insulation detection, the vehicle controller sends a fuel cell power demand request to the fuel cell controller based on the difference between the vehicle's required power and the maximum output power of the power battery, such that: When the power demand of the vehicle exceeds the maximum output power of the power battery, the vehicle controller controls the fuel cell to output power of no less than 25kW. When the vehicle's required power is less than or equal to the maximum output power of the power battery, the vehicle controller controls the fuel cell to operate at minimum power, and after operating at minimum power for a second set time, switches to high power operation for a third set time.

8. The insulation testing method for a hybrid fuel cell vehicle according to claim 7, characterized in that, The minimum power is 1-2kW, and the high power is 25kW.

9. The insulation testing method for a hybrid fuel cell vehicle according to claim 7, characterized in that, The second set time is 10 minutes, and the third set time is 1 minute.

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