A method for diagnosing a fault of voltage uniformity of a fuel cell system

Abstract

The application discloses a kind of fuel cell system voltage consistency fault diagnosis method, when average single voltage and the difference of minimum single voltage is greater than voltage difference threshold value, and the minimum single voltage variation rate is greater than voltage variation rate threshold value, determine whether there is single battery has been marked as there is voltage patrol module measurement fault: if there is, end diagnosis, if there is no, continue diagnosis;Increase air flow and hydrogen recirculation flow, if the difference is less than or equal to voltage difference threshold value, then diagnose stack flooding, end diagnosis;If the difference is greater than voltage difference threshold value, continue diagnosis;Restore air flow and hydrogen recirculation flow, when the difference is less than or equal to voltage difference threshold value, then judge whether the minimum single voltage variation rate is greater than voltage variation rate threshold value: if yes, then diagnose voltage patrol module measurement fault;If no, then diagnose as non-voltage patrol module measurement fault.The application can make accurate judgment to the measurement fault of voltage patrol module.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cell, in particular to a fault diagnosis method for voltage consistency of fuel cell system. BACKGROUND

[0002] Fuel cell stack is stacked by multiple single cells. When the fuel cell system generates electricity, the voltage of single cell is measured by voltage inspection module (CVM) to detect the consistency of single voltage in real time. When the single voltage is low due to common conditions such as water flooding of single cell, corresponding measures need to be taken to prevent the performance of single cell from further deteriorating, otherwise the normal power generation of the whole stack will be affected, and even irreversible damage to single cell will be caused.

[0003] However, when the voltage inspection module has a measurement fault, such as inaccurate single voltage measurement caused by problems such as poor contact of wire welding point, virtual connection of connector, signal interference, etc., it will also cause the single voltage to be low, which will lead to incorrect and effective actions of the fuel cell system, causing misdiagnosis and preventing the system from continuing normal power generation.

[0004] Therefore, it is necessary to correctly identify and diagnose the voltage consistency problem caused by the measurement fault of the voltage inspection module, so as to take correct and effective measures in time and ensure the normal operation of the fuel cell system.

[0005] Currently, there is a lack of diagnosis means for the measurement fault of the voltage inspection module, and the complex working conditions of the vehicle-mounted fuel cell system also increase the possibility of measurement fault of the voltage inspection module. SUMMARY

[0006] To solve one of the above technical problems, the present application provides a fault diagnosis method for voltage consistency of fuel cell system, which can accurately judge the measurement fault of the voltage inspection module, effectively avoid misdiagnosis, and improve the operation stability of the fuel cell system.

[0007] To solve the above technical problems, the present application provides the following technical scheme: a fault diagnosis method for voltage consistency of fuel cell system, comprising the following steps:

[0008] When the fuel cell system is normally operated, the difference ΔU between the average single voltage and the minimum single voltage and the minimum single voltage change rate dU min / dt are calculated in real time, U min is the minimum single voltage, and t is time;

[0009] When the difference ΔU is greater than the voltage difference threshold, and the minimum single voltage change rate dU minIf the voltage change rate dU / dt is greater than the voltage change rate threshold value, the number of single cells with the minimum single voltage is determined, and it is further determined whether any single cell in all single cells with the minimum single voltage has been marked as having a voltage inspection module measurement fault: if yes, the present diagnosis is ended; if no, the next diagnosis process is entered;

[0010] The air flow rate and the hydrogen recirculation flow rate entering the stack are increased, and within the ΔT time, if the difference ΔU decreases and is less than or equal to the preset voltage difference threshold value, the stack is diagnosed as flooded, and the present diagnosis is ended; if the difference ΔU is greater than the voltage difference threshold value, the next diagnosis process is entered;

[0011] The air flow rate and the hydrogen recirculation flow rate are restored, and the difference ΔU is continuously monitored; when the difference ΔU decreases and is less than or equal to the preset voltage difference threshold value, it is determined whether the minimum single voltage change rate dU / dt is greater than the preset voltage change rate threshold value: if yes, a voltage inspection module measurement fault is diagnosed, and the present diagnosis is ended; if no, a non-voltage inspection module measurement fault is diagnosed, and the present diagnosis is ended. min

[0012] Further, the voltage difference threshold value is 0.05V-0.1V, the voltage change rate threshold value is 0.1V / s-0.2V / s, and the ΔT time is 1s-5s.

[0013] The air flow rate and the hydrogen recirculation flow rate entering the stack are increased, and the air flow rate increase ratio and the hydrogen recirculation flow rate increase ratio are both 5%-15%.

[0014] Further, the fuel cell system voltage consistency fault diagnosis method further comprises: during the fault diagnosis method, if the minimum single voltage is less than a voltage threshold value, the fuel cell system is directly terminated to protect the stack; and the voltage threshold value is 0.1V-0.3V.

[0015] After the above technical solution is adopted, the present application has at least the following beneficial effects: the present application can accurately judge the measurement fault of the voltage inspection module, effectively avoid misdiagnosis, and improve the fuel cell system operation stability; the diagnosis method of the present application, without adding additional detection equipment on the basis of the original fuel cell system equipment, can accurately diagnose the stack fault and greatly save the cost. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 FIG. 1 is a structural schematic diagram of a fuel cell system of the present application.

[0017] Figure 2 FIG. 4 is a voltage trend graph of the fuel cell system of the present application when the stack is flooded.

[0018] Figure 3 ​The voltage trend chart for the fuel cell system patrol module in case of failure.

[0019] Figure 4 The step block diagram of the fault diagnosis method. DETAILED DESCRIPTION

[0020] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict, and the present application will be further described in detail below in combination with the drawings and specific embodiments.

[0021] The embodiment discloses a fuel cell system, which comprises a stack 1, a voltage patrol module 11, an air subsystem 2 and a hydrogen subsystem 3. Figure 1 As shown in the figure, the stack 1 comprises a hydrogen inlet, a hydrogen outlet, an air inlet and an air outlet, the air subsystem 2 comprises an air compressor 21, an intercooler 22 and a back pressure valve 23, and the hydrogen subsystem 3 comprises a hydrogen supply unit 31, a proportional valve 32, a gas-water separator 33, a water and exhaust valve 34 and a hydrogen circulating pump 35.

[0022] The air compressor 21, the intercooler 22 and the air inlet are sequentially connected, and the air outlet is connected to the back pressure valve 23; the hydrogen supply unit 31, the proportional valve 32 and the hydrogen inlet are sequentially connected, the hydrogen outlet, the gas-water separator 33 and the water and exhaust valve 34 are sequentially connected, and one end of the hydrogen circulating pump 35 is connected to the gas-water separator 33 and the other end is connected to the hydrogen inlet. The voltage patrol module 11 is connected to the stack 1 and is used for monitoring the single voltage of the single cell of the stack 1 in real time.

[0023] When the fuel cell system is running, on the air subsystem 2 side, air is driven by the air compressor 21 and enters the cathode of the stack 1 after being cooled by the intercooler 22, and is distributed to each single cell of the stack 1 (the stack 1 is stacked by a plurality of single cells), and the exhaust air after reaction is discharged through the back pressure valve 23; on the hydrogen subsystem 3 side, high-pressure hydrogen provided by the hydrogen supply unit 31 enters the anode of the stack 1 after being decompressed by the proportional valve 32, and is distributed to each single cell of the stack 1, hydrogen and water vapor are generated after electrochemical reaction of hydrogen in the anode of the stack 1, the hydrogen and water vapor are separated by the gas-water separator 33, the separated liquid water is regularly discharged to the outside through the water and exhaust valve 34, and the anode tail gas is driven to circulate into the anode of the stack 1 by the hydrogen circulating pump 35. The voltage patrol module 11 monitors the single voltage of the single cell of the stack 1 in real time. The air flow through the cathode of the stack 1 and the hydrogen flow through the anode of the stack 1 can be controlled by changing the rotating speed of the air compressor 21 and the hydrogen circulating pump 35 respectively.

[0024] When the fuel cell system is running, the average single voltage and the minimum single voltage of the single cell of the stack are monitored and calculated in real time by the voltage patrol module 11. As shown in the figure, Figure 2The figure shows a typical phenomenon of voltage consistency deterioration due to flooding during actual operation of the fuel cell system, the minimum single voltage slowly decreases, deviates from the average single voltage, and gradually recovers by strengthening the purging of the cathode or anode of the stack 1; as shown in the figure Figure 3 The figure shows a typical phenomenon of voltage consistency deterioration due to measurement failure of the voltage inspection module 11 during actual operation of the fuel cell system, the minimum single voltage rapidly decreases, deviates from the average single voltage, and then unpredictably rapidly recovers.

[0025] The embodiment discloses a fault diagnosis method for voltage consistency of a fuel cell system, as shown in the figure, comprising the following steps: Figure 4 The figure shows a typical phenomenon of voltage consistency deterioration due to flooding during actual operation of the fuel cell system, the minimum single voltage slowly decreases, deviates from the average single voltage, and gradually recovers by strengthening the purging of the cathode or anode of the stack 1; as shown in the figure

[0026] When the fuel cell system is normally operated, each operating parameter of the stack 1 is within a normal range, the operating parameters include temperature, gas flow, pressure, etc., the difference ΔU between the average single voltage and the minimum single voltage and the minimum single voltage change rate dU min / dt are detected and calculated in real time by the voltage inspection module 11, U min is the minimum single voltage, t is time, and the number of single cells reaching the minimum single voltage in the stack 1 is recorded at the same time.

[0027] When the difference ΔU is greater than a pre-set voltage difference threshold value, and the minimum single voltage change rate dU min / dt is greater than a pre-set voltage change rate threshold value, it indicates that a single voltage low fault occurs, the number of single cells of the minimum single voltage is determined, and it is further confirmed whether any single cell has been marked as having a voltage inspection module measurement fault among all single cells of the minimum single voltage, the voltage difference threshold value can be selected from 0.05V to 0.1V, and the voltage change rate threshold value can be selected from 0.1V / s to 0.2V / s; if any single cell has been marked as having a voltage inspection module measurement fault, the alarm of the single voltage low fault of the single cell is shielded (generally, since the single cell has been marked as having a voltage inspection module measurement fault, the alarm is shielded to avoid repeated triggering of the alarm due to the single voltage low of the single cell), the current diagnosis is ended, and the fuel cell system continues to operate; if no single cell has been marked as having a voltage inspection module measurement fault, the next diagnosis process is entered.

[0028] By increasing the rotation speed of the air compressor 21 and the rotation speed of the hydrogen circulation pump 35, the air flow and the hydrogen recirculation flow into the stack 1 are increased (the increase ratio of the air flow and the hydrogen recirculation flow can be selected as 5% to 15%), within the time ΔT (1s to 5s), if the difference ΔU is reduced and is less than or equal to the preset voltage difference threshold value, it is indicated that the single voltage is not caused by the measurement failure of the voltage inspection module, but is caused by the lack of air due to water flooding or other reasons, the air flow and the hydrogen recirculation flow are restored, and the present diagnosis is ended; if the difference ΔU is still greater than the preset voltage difference threshold value, the next diagnosis process is entered.

[0029] The air flow and the hydrogen recirculation flow are restored, and the difference ΔU is continuously monitored; when the difference ΔU is reduced and is less than or equal to the preset voltage difference threshold value, it is determined whether the minimum single voltage change rate dU / dt is greater than the preset voltage change rate threshold value: if yes, it is diagnosed as the measurement failure of the voltage inspection module, the number of single cells of the minimum single voltage is marked and stored, the present diagnosis is ended, and the fuel cell system continues to operate; if no, it is diagnosed as the measurement failure of the non-voltage inspection module, the present diagnosis is ended, and the fuel cell system continues to operate. min

[0030] In the above fault diagnosis process, if the minimum single voltage U min is less than the preset voltage threshold value (which can be selected as 0.1V to 0.3V), the operation of the fuel cell system is directly terminated to protect the stack.

[0031] The embodiment can accurately judge the measurement failure of the voltage inspection module, effectively avoid misdiagnosis, and improve the operation stability of the fuel cell system; the diagnosis method of the embodiment can accurately diagnose the stack failure without increasing additional detection equipment on the basis of the original fuel cell system equipment, and greatly saves the cost.

[0032] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various equivalent changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, the scope of the present application is defined by the appended claims and their equivalent ranges.​

Claims

1. A method of diagnosing a failure of voltage uniformity of a fuel cell system, characterized by, The method comprises the following steps: In normal operation of the fuel cell system, the difference ΔU between the average single voltage and the minimum single voltage and the minimum single voltage change rate dU / dt, U min are detected and calculated in real time min is the minimum single voltage, and t is time; When the difference ΔU is greater than the voltage difference threshold, and the minimum single voltage change rate dU min If the absolute value of / dt is greater than the voltage change rate threshold, determine the number of individual cells with the minimum single voltage. Then, confirm whether any individual cells with the minimum single voltage have been marked as having a voltage inspection module measurement fault. If so, end the current diagnosis; otherwise, proceed to the next diagnostic step. The voltage change rate threshold is 0.1V / s to 0.2V / s. If the difference ΔU is reduced and is less than or equal to a voltage difference threshold value, the fuel cell stack is diagnosed as flooded, and the diagnosis is ended; if the difference ΔU is greater than the voltage difference threshold value, the next diagnosis process is entered; The air flow and hydrogen recirculation flow are restored, and the difference ΔU is continuously monitored; when the difference ΔU is reduced and less than or equal to the voltage difference threshold, it is judged that the minimum single voltage change rate dU min whether the absolute value of dU / dt is greater than the voltage change rate threshold: if yes, it is diagnosed as a voltage inspection module measurement fault, and the minimum single cell number is marked and stored, and the current diagnosis is ended; if no, it is diagnosed as a non-voltage inspection module measurement fault, and the current diagnosis is ended.

2. The method of claim 1, wherein The voltage difference threshold value is 0.05V-0.1V, and the ΔT time is 1s-5s; the air flow rate and the hydrogen recirculation flow rate into the fuel cell stack are increased by 5%-15%.

3. The method of claim 1, wherein The method further comprises the following steps: During the fault diagnosis method, if the minimum single voltage is less than a voltage threshold value, the operation of the fuel cell system is directly terminated to protect the fuel cell stack.

4. The method of claim 3, wherein The voltage threshold value is 0.1V-0.3V.

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