Method for testing service life of fixed power generation fuel cell stack

Abstract

The invention relates to the technical field of fuel cells, in particular to a method for testing the service life of a fixed power generation fuel cell stack. The method comprises the following steps: S1, determining a reference current, a low-load current and a rated current of the fuel cell stack through a current-voltage test; s2, determining the initial voltage V0 of the fuel cell stack through a working condition test; and S3, determining the voltage change rate V low under the low-load working condition through low-load working condition test circulation. And S4, determining the voltage change rate V under the rated working condition through rated working condition test circulation. And S5, determining the voltage change rate V change under the variable load working condition through variable load working condition test circulation. And S6, determining the voltage change rate V1 of the fuel cell caused by the variable load working condition. And S7, determining the performance degradation rate A of the fuel cell. And S8, determining the service life range tLF of the fuel cell stack. Compared with the prior art, the method has the advantages that the attenuation rate of each working condition is calculated and finally integrated, so that the prediction error caused by the fuel cell is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of fuel cells, in particular to a life test method for a fixed power generation fuel cell stack. Background Art

[0002] Proton exchange membrane fuel cells have the advantages of high conversion efficiency, clean and pollution-free, and can be started quickly at room temperature. They have become an ideal power source today. As proton exchange membrane fuel cells gradually move towards commercialization, the optimization of fuel cell life has gradually been put on the agenda and has become a focus of increasing attention. Under this condition, life prediction technology has developed rapidly. It can quickly evaluate the service life of fuel cells. Compared with large-scale actual measurements of fuel cells, it can save a lot of manpower, material resources, and financial resources, and can accelerate the product development cycle and provide decision support for system control. Therefore, fuel cell life prediction technology has become a current research hotspot.

[0003] At present, the mainstream fuel cell life prediction methods are divided into two categories. One is the fuel cell stack life prediction method driven by the fuel cell electrochemical mechanism model. The fuel cell stack performance prediction method driven by the electrochemical mechanism model mostly combines the material properties of the stack itself, the stack failure mechanism and the electrochemical mechanism to construct a semi-empirical formula to predict the performance degradation of the fuel cell stack. The disadvantage of this method is that if the fuel cell operation state needs to be accurately predicted, a complex mathematical model needs to be established to describe the internal electrochemical and thermal phenomena, and its formula lacks versatility. The other is a data-driven fuel cell performance prediction method based on big data. This method uses big data and machine learning technology to improve the prediction accuracy of the fuel cell life prediction model. Its disadvantage is that the current research data are mainly current density, voltage, etc., and it mainly focuses on predicting the voltage of the stack at future times through the current density of the stack. Considering that the stack voltage values ​​are relatively small, this method has a high demand for prediction accuracy. Slight fluctuations in the predicted value will have a greater impact on the error, and the longer the prediction time, the greater the prediction error of the model.

[0004] At present, the national standard GB / T 38914-2020 discloses a method to predict the life of fuel cells by decomposing working conditions, but this method cannot be applied to the life prediction of stationary fuel cells. There are also a large number of fuel cells used in stationary applications. After the fixed power generation fuel cell stack is started, it basically runs for a long time without stopping, and the start-stop attenuation rate cannot be taken into account. Moreover, the judgment standard for the end of fuel cell life, in accordance with the current national regulations on the performance degradation of new energy vehicle batteries, the performance reduction of the battery during the warranty period should not exceed the limit of 10%, but there is no national standard for stationary fuel cells yet, and the limit requirements of automotive fuel cells for the judgment of the life requirements of stationary fuel cells still cannot solve the problem. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a life test method for a fixed power generation fuel cell stack, comprising the following steps: S1: determining the reference current, low load current and rated current of the fuel cell stack through a current-voltage test. S2: determining the initial voltage V of the fuel cell stack through a working condition test. 0 S3: Determine the voltage change rate V under low-load conditions through low-load condition test cycles 低 S4: Determine the voltage change rate V under rated operating conditions through the rated operating condition test cycle 额 S5: Determine the voltage change rate V under variable load conditions through variable load condition test cycles 变 S6: Determine the voltage change rate V of the fuel cell caused by the variable load condition 1 S7: Determine the fuel cell performance attenuation rate A. S8: Determine the fuel cell stack service life range t LF .

[0006] The specific method for determining the reference current, low-load current and rated current of the fuel cell stack described in step S1 includes measuring 10 operating points between open circuit and an average voltage of 0.60V per fuel cell, and recording the output current and voltage when each operating condition is stable; recording the open circuit voltage; and performing a series of loading on the fuel cell to measure the output current and voltage when each operating condition is stable, and selecting the reference current, low-load current and rated current of the fuel cell stack.

[0007] The initial working condition cycle process of the fuel cell stack described in step S2 includes S21: one working condition test cycle is performed every hour. S22: when S21 reaches the end of the last cycle, S1 is repeated to obtain the power generation performance of the fuel cell stack and generate a power generation performance curve, and the average single fuel cell voltage V under the reference current working condition is determined according to the power generation performance curve. 0 , that is, the initial voltage of the fuel cell stack V 0 .

[0008] The fuel cell stack low-load operating condition test cycle described in step S3 includes S31: completing one operating condition test cycle every hour, and completing at least 60 cycles for each operating condition. S32: generating a low-load operating condition spectrum according to the corresponding voltage value of the reference current operating condition obtained in step S1, and performing a linear fit between the reference current operating condition and the corresponding voltage value measured at the end of the last cycle of each low-load operating condition cycle, so as to obtain the voltage change rate V under the low-load operating condition. 低 .

[0009] The fuel cell stack rated operating condition test cycle described in step S4 includes S41: completing one operating condition test cycle every hour, and completing at least 60 cycles for each operating condition. S42: generating a rated operating condition spectrum according to the corresponding voltage value of the reference current operating condition obtained in step S1, and performing a linear fit between the reference current operating condition and the corresponding voltage value measured at the end of the last cycle of each rated operating condition cycle, so as to obtain the voltage change rate V under the rated operating condition. 额 .

[0010] The fuel cell stack variable load condition test cycle S51 described in step S5: complete one test cycle every 4 hours, and complete at least 15 cycles. S52: generate a variable load condition spectrum based on the corresponding voltage value of the reference current condition obtained in step S1, and perform linear fitting on the reference current condition and the corresponding voltage value measured at the end of the last cycle of each variable load condition cycle to obtain the voltage change rate V under the variable load condition. 变。

[0011] Fuel cell voltage change rate V caused by variable load conditions 1 for: Where n is the number of loads; t 1 is the dwell time of the initial working condition; t 3 is the dwell time at the rated current point under rated operating conditions; t 5 is the dwell time at the low current point under rated conditions; t 9 It is the dwell time at the low current point under low current working condition.

[0012] The fuel cell performance attenuation rate A is: Where n is the number of loading times; t1 is the operating time under low-load conditions; t2 is the operating time under rated conditions, as well as the frequency or time occupied by other conditions; the total time occupied by all condition spectra should be 3600s±360s.

[0013] The judgment standard of the service life of the stationary power generation fuel cell stack described in S8 is: under the reference current, the average voltage decay rate A of each fuel cell is ≤20%, otherwise it is judged that the service life has ended.

[0014] The service life of the fuel cell stack described in S8 is t LF The range is: Where A is the fuel cell performance attenuation rate; V O is the initial voltage of the fuel cell stack.

[0015] Compared with the prior art, the present invention can start from the baseline current, low-load current and rated current of the fuel cell stack, and experimentally determine the voltage change rate of the three working conditions respectively, and considering that the fixed power generation fuel cell stack basically runs for a long time without stopping after startup, the attenuation rate caused by the start and stop of the stack is basically not considered. By calculating the attenuation rate of each working condition and then integrating them at the end, the error caused by the fuel cell itself to the prediction is reduced, and the accuracy of the prediction is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the power generation performance curve of the fuel cell stack.

[0017] Figure 2 It is the fuel cell average single cell voltage-low load operating time spectrum.

[0018] Figure 3 It is the fuel cell average single cell voltage-rated operating time spectrum.

[0019] Figure 4 It is the average single-cell voltage-load variation frequency spectrum of the fuel cell.

[0020] Figure 5 It is the low load condition spectrum.

[0021] Figure 6 It is the rated operating spectrum.

[0022] Figure 7 It is the spectrum of variable load conditions.

[0023] Figure 8 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0025] S1: Set up 10 operating points between the open circuit and 0.6V voltage, record the output current and voltage when each operating condition is stable; record the open circuit voltage; through a series of loading on the fuel cell, measure the output current and voltage when each operating condition is stable, and select the reference current, low load current and rated current of the fuel cell stack. Now take the reference current as 60A, then the corresponding average voltage per fuel cell is 0.74V; the low load current is 40A, corresponding to the average voltage per fuel cell is 0.78V, the rated current is 80A, corresponding to the average voltage per fuel cell is 0.70V.

[0026] S2: Figure 1As shown, S21: one hour is one working condition test cycle. S22: when S21 reaches the end of the last cycle, S1 is repeated to obtain the power generation performance of the fuel cell stack and generate a power generation performance curve, and the average single fuel cell voltage V under the reference current working condition is determined according to the power generation performance curve. 0 , that is, the initial voltage of the fuel cell stack V 0 .

[0027]

[0028] Table 1 shows the operating procedures of step S2. From S1, we can see that the average single-cell fuel cell voltage under the reference current condition is V 0 =0.74V.

[0029] S3: Figure 2 As shown, S31: complete one working condition test cycle every hour, and complete at least 60 cycles for each working condition. S32: generate a low-load working condition spectrum according to the corresponding voltage value of the reference current working condition obtained in step S1, and perform linear fitting on the reference current working condition and the corresponding voltage value measured at the end of each low-load working condition cycle to obtain the voltage change rate V under the low-load working condition. 低 .

[0030]

[0031] Table 2 is the operating procedure of step S3. Linear fitting is performed based on the corresponding voltage values ​​of the experimentally recorded reference current conditions. Figure 5 As shown in the figure, the vertical axis is the average single-cell voltage of the fuel cell (V), and the horizontal axis is the fitting diagram of the low-load working time (h). Finally, V 低 =5×10 -6 V / h.

[0032] S4: Figure 3 As shown, the fuel cell stack rated operating condition test cycle includes S41: completing one operating condition test cycle every hour, and completing at least 60 cycles for each operating condition, S42: generating a rated operating condition spectrum according to the corresponding voltage value of the reference current operating condition obtained in step S1, and performing a linear fit on the corresponding voltage value of the reference current operating condition measured at the end of each rated operating condition cycle, so as to obtain the voltage change rate V under the rated operating condition. 额 .

[0033]

[0034] Table 3 is the operating procedure of step S4. Linear fitting is performed based on the corresponding voltage values ​​of the experimentally recorded reference current conditions. Figure 6 As shown in the figure, the vertical axis is the average single-cell voltage (V), and the horizontal axis is the rated operating time (h) of the fitting diagram, and finally Vrated = 7×10 -6 .

[0035] S5: Figure 4 As shown, the fuel cell stack variable load condition test cycle S51: complete one test cycle every 4 hours, and complete at least 15 cycles. S52: generate a variable load condition spectrum based on the corresponding voltage value of the reference current condition obtained in step S1, and perform linear fitting on the corresponding voltage value of the reference current condition measured at the end of each cycle to obtain the voltage change rate V under the variable load condition. 变 .

[0036]

[0037] Table 4 is the operating procedure of step S5. Linear fitting is performed based on the corresponding voltage values ​​of the experimentally recorded reference current conditions. Figure 7 As shown in the figure, the vertical axis is the average single-cell voltage (V), and the horizontal axis is the fitting diagram of the number of load changes (n). Finally, V 变 =9×10 -6 V / times.

[0038] S6: Determine the fuel cell voltage change rate V caused by the variable load condition 1 :

[0039] n, t3, t5, and t9 can be obtained by recording the steps in Table 4. In this embodiment, a total of n=216 loading times are measured, and the residence time t under different working conditions is recorded. 1 =90s, t3=3s, t5=15s, t9=200s, finally calculate V 1 =8.971×10 -6 V / times.

[0040] S7: Determine the fuel cell performance attenuation rate A:

[0041] The total time occupied by all working conditions should be 3600s±360s. The total number of loading times n 1 =1 time, low load condition running time t 1 =36min, rated operating time t 2 =21min, A=0.144×10 -4 V / h.

[0042] S8: Determine the service life range of the fuel cell stack t LF。

[0043] Fuel cell stack service life LfThe range is determined by the national standard for automobiles, which takes the average voltage decay rate of each fuel cell cell under the reference current. The service life standard of the fixed power generation fuel cell stack is the average voltage decay rate of each fuel cell cell under the reference current as 20%. If A>20%, it is determined that the life is over.

[0044] Service life range LF The formula is

[0045] The V obtained by S2 above 0 , the fuel cell performance attenuation rate A obtained in S7 is substituted into the formula to obtain the service life range t LF ∈[7808, 10378)h.

[0046] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be within the protection scope of the present invention.

Claims

1. A life test method for a stationary power generation fuel cell stack, The following steps are involved: S1: Determine the base current, low-load current and rated current of the fuel cell stack through current-voltage test. S2: Determine the initial voltage V0 of the fuel cell stack through operating condition test. S3: Determine the voltage change rate V under low-load condition through low-load operating condition test cycle. 低 S4: Determine the voltage change rate V under rated operating conditions through the rated operating condition test cycle 额 S5: Determine the voltage change rate V under variable load conditions through variable load condition test cycles 变 S6: Determine the fuel cell voltage change rate V1 caused by the variable load condition. S7: Determine the fuel cell performance attenuation rate A. S8: Determine the fuel cell stack service life range t LF .

2. The life test method of a stationary power generation fuel cell stack according to claim 1, characterized in that: The specific method for determining the reference current, low-load current and rated current of the fuel cell stack described in step S1 includes measuring 10 operating points between open circuit and an average voltage of 0.60V per fuel cell, and recording the output current and voltage when each operating condition is stable; recording the open circuit voltage; and selecting the reference current, low-load current and rated current of the fuel cell stack by performing a series of loading on the fuel cell and measuring the output current and voltage values ​​when each operating condition is stable.

3. The life test method of a stationary power generation fuel cell stack according to claim 1, characterized in that: The initial working condition cycle process of the fuel cell stack described in step S2 includes S21: one working condition test cycle is performed every hour. S22: when S21 reaches the end of the last cycle, S1 is repeated to obtain the power generation performance of the fuel cell stack and generate a power generation performance curve, and the average single fuel cell voltage V0 under the reference current working condition is determined according to the power generation performance curve, that is, the initial voltage V0 of the fuel cell stack.

4. The method for testing the life of a stationary fuel cell stack according to claim 1, characterized in that: The fuel cell stack low-load operating condition test cycle described in step S3 includes S31: completing one operating condition test cycle every hour, and completing at least 60 cycles for each operating condition. S32: generating a low-load operating condition spectrum according to the corresponding voltage value of the reference current operating condition obtained in step S1, and performing a linear fit between the reference current operating condition and the corresponding voltage value measured at the end of the last cycle of each low-load operating condition cycle, so as to obtain the voltage change rate V under the low-load operating condition. 低 .

5. The life test method of a stationary power generation fuel cell stack according to claim 1, characterized in that: The fuel cell stack rated operating condition test cycle described in step S4 includes S41: completing one operating condition test cycle every hour, and completing at least 60 cycles for each operating condition. S42: generating a rated operating condition spectrum according to the corresponding voltage value of the reference current operating condition obtained in step S1, and performing a linear fit between the reference current operating condition and the corresponding voltage value measured at the end of the last cycle of each rated operating condition cycle, so as to obtain the voltage change rate V under the rated operating condition. 额 .

6. The life test method of a stationary power generation fuel cell stack according to claim 1, characterized in that: The fuel cell stack variable load condition test cycle S51 described in step S5: complete one test cycle every 4 hours, and complete at least 15 cycles. S52: generate a variable load condition spectrum based on the corresponding voltage value of the reference current condition obtained in step S1, and perform linear fitting on the reference current condition and the corresponding voltage value measured at the end of the last cycle of each variable load condition cycle to obtain the voltage change rate V under the variable load condition. 变。 7. The life test method of a stationary power generation fuel cell stack according to claim 1, characterized in that: The fuel cell voltage change rate V1 caused by the variable load condition is: Where n is the number of loading times; t1 is the dwell time at the initial operating condition; t3 is the dwell time at the rated current point at the rated operating condition; t5 is the dwell time at the low current load point under rated conditions; t9 is the dwell time at the low load current point under the low load current condition.

8. The life test method of a stationary power generation fuel cell stack according to claim 1, characterized in that: The fuel cell performance attenuation rate A is: Where n1 is the number of loading times; t1 is the low-load operating time; t2 is the rated operating time; And the frequency or time occupied by other operating conditions; the total time occupied by all operating condition spectra should be 3600s±360s.

9. The life test method of a stationary power generation fuel cell stack according to claim 1, characterized in that: The judgment standard of the service life of the stationary power generation fuel cell stack described in S8 is: under the reference current, the average voltage decay rate A of each fuel cell is ≤20%, otherwise it is judged that the service life has ended.

10. The life test method of a stationary power generation fuel cell stack according to claim 1, characterized in that: The service life of the fuel cell stack described in S8 is t LF The range is: Where A is the fuel cell performance attenuation rate; V0 is the initial voltage of the fuel cell stack.

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