CN116111145A - Fuel cell stack model online analysis method - Google Patents
Fuel cell stack model online analysis method Download PDFInfo
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- CN116111145A CN116111145A CN202211730227.2A CN202211730227A CN116111145A CN 116111145 A CN116111145 A CN 116111145A CN 202211730227 A CN202211730227 A CN 202211730227A CN 116111145 A CN116111145 A CN 116111145A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04992—Processes for controlling fuel cells or fuel cell systems characterised by the implementation of mathematical or computational algorithms, e.g. feedback control loops, fuzzy logic, neural networks or artificial intelligence
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04298—Processes for controlling fuel cells or fuel cell systems
- H01M8/04305—Modeling, demonstration models of fuel cells, e.g. for training purposes
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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Abstract
An online analysis method for fuel cell pile model belongs to the technical field of fuel cell pile model. It comprises the following steps: selecting a frequency f0 as a short circuit frequency of a transmission part of a fuel cell stack model, selecting two frequencies f2 and f3 between the high frequencies f1 and f0, obtaining real imaginary impedance values of the stack under the four disturbance currents, obtaining element values of the model which do not contain a substance transmission part by using the impedance values, selecting a frequency f4 smaller than f0, obtaining the real imaginary impedance values of the stack under the frequency, and obtaining element values of the transmission part in the complete model by combining the obtained element values; and respectively bringing the frequency f0 into a complete model and a transmission part lack model, comparing whether the difference of the resistance values of the two models is in an error range, and adjusting the frequency f0 to obtain an accurate resistance value of the circuit element. The method for obtaining the resistance value of the fuel cell model element avoids testing complete impedance spectrum and shortens the solving time for determining the model resistance value.
Description
Technical Field
The invention belongs to the technical field of fuel cell stack models, and particularly relates to an online analysis method of a fuel cell stack model.
Background
The fuel cell has high energy conversion efficiency, low operating temperature and environmental friendliness, and is a favored new energy development direction. However, due to the complicated structure, severe working environment, frequent change of running conditions and the like, various faults are unavoidable in practical application, and the durability and the reliability are affected if the faults are not handled in time. The method for judging the fault type of the fuel cell by using the model is a more effective method, but whether the circuit element value is accurate or not can generate larger error on the fault judgment, so that it is important to obtain accurate model element value to obtain accurate fault type and fault degree.
The existing method for obtaining the model element uses an electrochemical impedance spectrum mode, and obtains the resistance value of the circuit element through the electrochemical impedance spectrum by utilizing a nonlinear least square method to fit and solve, but the obtaining of the electrochemical impedance spectrum of the fuel cell needs to take a long time, and the obtained resistance value cannot reflect the actual condition of the electric pile when the electric pile is in dynamic change. Or the PSO and differential evolution algorithm mode is used, the value of the continuously changing element is judged and fitted once and once, and the obtained precision is good, but larger calculation amount is needed.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide an online analysis method for a fuel cell stack model, which can realize the online rapid obtaining of the accurate resistance value of a fuel cell model element in a medium-high frequency range.
The invention provides the following technical scheme: an online analysis method for fuel cell stack model comprises the following specific steps:
s1, selecting a frequency f0 in a frequency range where a turning frequency causing a short circuit of a fuel cell model transmission part and a constant phase element do not occur;
s2, selecting a high-frequency f1 in a frequency range higher than the frequency f0 and lower than the short circuit of the constant-phase element, selecting two frequency points f2 and f3 at equal frequency intervals between the f0 and f1, and applying alternating current of the frequency points to the galvanic pile to obtain a galvanic pile alternating current impedance value under each frequency;
s3, calculating an element value which does not contain the transmission part fuel cell model by using the obtained impedance value;
s4, selecting a frequency f4 in a frequency range in which short circuit does not occur in a transmission part lower than the frequency f0, obtaining a pile resistance value under the frequency f4, and obtaining an element value of a substance transmission part of the complete model by using the obtained model element value and the impedance value of the frequency f 4;
s5, the frequency f0 is brought into the complete model to obtain a real-imaginary part resistance value;
s6, judging whether the resistance result in S5 and the real-imaginary part resistance of the transmission part model are within a set error range, and adjusting the frequency f0 to finally obtain the accurate element resistance.
Further, the upper limit value of the frequency f0 is determined by a frequency minimum value in a determination range for causing a short circuit of the constant phase element of the fuel cell equivalent circuit, and the lower limit value is determined by a maximum frequency at which a short circuit occurs in the transmission portion.
Further, the frequency range of the short circuit of the constant phase element is determined by the maximum value obtained by the resistance values R1 and R2 and the variation range of the CPE element, and the formula is as follows:
f=1/2ΠCPE*[R1*R2/(R1+R2)]
wherein R1 is ohm resistance, R2 is activation resistance, CPE is constant phase element.
Further, the frequency range of the transmission part short circuit is determined by the maximum value obtained by the variation ranges of the resistance R3 and the C1 element, and the formula is as follows: f=1/2 pi R3C1, where R3 is the transmission resistance and C1 is the capacitance at the transmission.
Further, in the step S2, the frequency f0 is determined to be the frequency interval which is required to be the distance from the frequency f1 to meet two thirds of the working condition when the impedance spectrum activation semicircle is minimum, so that the influence of the concentration of impedance values on the accuracy of the model element is avoided.
Further, in the step S2, the frequencies f2 and f3 are equal frequency interval frequencies between f0 and f1, which are multiples of 10.
Further, in the step S4, the frequency f4 is less than the frequency around f0min, which is a multiple of 10.
Further, the step S6 is repeated, and when the resistance result in the step S5 and the real-imaginary part resistance of the model without the transmission part do not meet the set error range, f0 is adjusted by increasing (f 0max-f0 min)/10 each time.
By adopting the technology, compared with the prior art, the invention has the following beneficial effects:
the method can realize the on-line rapid obtaining of the accurate resistance value of the fuel cell model element in the medium-high frequency range, and the method does not need higher excitation frequency to generate the problem of expensive impedance equipment; the method has the advantages of avoiding testing complete impedance spectrum, shortening the solving time for determining the model resistance value and having great significance for carrying out fault type diagnosis on the follow-up dependent model parameters.
Drawings
FIG. 1 is a schematic diagram of a flow chart of determining a frequency of a partial short circuit of a model transmission according to the present invention;
FIG. 2 is a schematic diagram of a complete fuel cell model of the present invention;
FIG. 3 is an equivalent circuit diagram of the present invention without transmission circuit;
FIG. 4 is a graph of impedance versus frequency for an RC parallel circuit of the present invention;
FIG. 5 is a graph of the impedance versus frequency of the parallel circuit of R and RC of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail below with reference to the accompanying drawings and examples of the present invention. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
On the contrary, the invention is intended to cover any alternatives, modifications, equivalents, and variations as may be included within the spirit and scope of the invention as defined by the appended claims. Further, in the following detailed description of the present invention, certain specific details are set forth in order to provide a better understanding of the present invention. The present invention will be fully understood by those skilled in the art without the details described herein.
Referring to fig. 1-5, as shown in fig. 1, the present example provides an online analysis method for a fuel cell stack model. By selecting a suitable frequency f0 in the frequency range where the frequency of the transmission partial short circuit in the fuel cell model as shown in fig. 2 and the frequency of the short circuit of the constant phase element in the model, the upper limit of the range f0 for f0 is the frequency at which the short circuit of the constant phase element in the model will occur, which is referred to as f0max.
By frequency of short circuit of FIG. 3
f=f1=1/2 pi CPE [ r1×r2/(r1+r2) ], where R1, R2, CPE elements are also range values that vary with operating conditions, and the frequency range of f1 is solved by historical values. The lower limit value of the range is selected as the maximum value f0max of f 0.
For the lower limit value of f0, solving the formula of f=1/2 pi R3C1, R3 and C1 as the material transmission resistance and the material transmission capacitance which change along with the working condition of the electric pile by using the short circuit formula of the RC circuit, obtaining the range of f by using the recorded range, and taking the obtained maximum value as the lower limit value f0min of f 0.
The selected f0 is used as a boundary line to select a high-frequency f1 in a frequency range higher than the frequency and lower than the short circuit of the constant-phase element, so that the difference value of the two frequencies is ensured to be in a certain range, more impedance information of the electric pile is ensured to be obtained, and the impedance value of the electric pile is not greatly different due to the fact that the frequency interval is relatively close, and the resistance value precision of the circuit element is affected. And selecting two frequencies f2 and f3 with equal frequency intervals between the two frequencies, enabling excitation current with four frequencies to flow into the fuel cell stack to obtain the response voltage of the cell stack, and obtaining real part and imaginary part values of the impedance of the cell stack in a frequency domain by using a fast Fourier method.
The obtained values are brought into a model not including a transmission portion, as shown in fig. 3, the ohmic resistance value, the activation resistance value and the resistance value of the constant phase element in the model are obtained by a nonlinear least square method, and a frequency f4 of a multiple of 10 is found on the side of the frequency smaller than the frequency f 0.
The impedance value under the frequency is obtained by adopting the mode of obtaining the real and imaginary impedance in the same mode, and the resistance and capacitance value of the transmission part in the complete equivalent circuit model are obtained by combining the obtained circuit element values and fitting. And carrying the frequency f0 into a complete model to solve and judge whether the phase difference between the resistance value and the model which does not contain the transmission part is within a certain range, so as to determine whether the frequency f0 is the frequency capable of ensuring the failure of the transmission part under the working condition. If not, the frequency of f0 is increased, and the gain of f0 is (f 0max-f0 min)/10, and then the judgment is continued.
For the fuel cell model selected as in fig. 1, as shown in fig. 5, the impedance of the stack is the sum of the ohmic resistance activation resistance and the mass transfer tissue when the frequency is 0. When the frequency is greater than f0 and less than f1, the transmission part in the model disappears, the impedance at the moment is only the resistance of the circuit shown in fig. 3, and when the frequency is greater than f2, the resistance of the electric pile is only the ohmic resistance.
Therefore, the transmission circuit is partially short-circuited by selecting proper frequency, the solution of the resistance value of the pile model element is simplified, and the frequency is selected to be in a middle-high frequency accessory, so that the time for obtaining response voltage by applying exciting current to the pile is shorter.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (8)
1. An on-line analysis method for fuel cell pile model is characterized in that: the method comprises the following specific steps:
s1, selecting a frequency f0 in a frequency range where a turning frequency causing a short circuit of a fuel cell model transmission part and a constant phase element do not occur;
s2, selecting a high-frequency f1 in a frequency range higher than the frequency f0 and lower than the short circuit of the constant-phase element, selecting two frequency points f2 and f3 at equal frequency intervals between the f0 and f1, and applying alternating current of the frequency points to the galvanic pile to obtain a galvanic pile alternating current impedance value under each frequency;
s3, calculating an element value which does not contain the transmission part fuel cell model by using the obtained impedance value;
s4, selecting a frequency f4 in a frequency range in which short circuit does not occur in a transmission part lower than the frequency f0, obtaining a pile resistance value under the frequency f4, and obtaining an element value of a substance transmission part of the complete model by using the obtained model element value and the impedance value of the frequency f 4;
s5, the frequency f0 is brought into the complete model to obtain a real-imaginary part resistance value;
s6, judging whether the resistance result in S5 and the real-imaginary part resistance of the transmission part model are within a set error range, and adjusting the frequency f0 to finally obtain the accurate element resistance.
2. The method for on-line analysis of a fuel cell stack model according to claim 1, wherein the upper limit value of the frequency f0 is determined by a frequency minimum value in a determination range for causing a short circuit of a constant phase element of the equivalent circuit of the fuel cell, and the lower limit value is determined by a maximum frequency for causing a short circuit of a transmission portion.
3. The method for on-line analysis of fuel cell stack model according to claim 2, wherein the frequency range of the short circuit of the constant phase element is determined by the maximum value obtained by the variation ranges of the resistance values R1, R2 and CPE elements, and the formula is as follows:
f=1/2ΠCPE*[R1*R2/(R1+R2)]
wherein R1 is ohm resistance, R2 is activation resistance, CPE is constant phase element.
4. The method for on-line analysis of fuel cell stack model according to claim 2, wherein the frequency range of the transmission part short circuit is determined by the maximum value obtained from the variation ranges of the resistance R3 and C1 elements, and the formula is as follows: f=1/2 pi R3C1, where R3 is the transmission resistance and C1 is the capacitance at the transmission.
5. The method for on-line analysis of fuel cell stack model according to claim 1, wherein the frequency f0 in the step S2 is determined to be a frequency interval which is about to satisfy two thirds of the working conditions when the impedance spectrum activation semicircle is minimum from the frequency f1, so as to avoid the influence of the relatively concentrated impedance value on the accuracy of the model element.
6. The method for online analysis of fuel cell stack model according to claim 5, wherein in the step S2, the frequencies f2 and f3 are equal frequency interval frequencies between f0 and f1, which are multiples of 10.
7. The method for online analysis of fuel cell stack model according to claim 6, wherein the frequency f4 in step S4 is less than f0min, which is a multiple of 10.
8. The method for online analysis of fuel cell stack model according to claim 7, wherein the step S6 is repeated, and when the resistance result in the step S5 and the real-imaginary part resistance of the model without the transmission part do not satisfy the set error range, the step f0 is adjusted by increasing (f 0max-f0 min)/10 each time.
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| CN202211730227.2A CN116111145A (en) | 2022-12-30 | 2022-12-30 | Fuel cell stack model online analysis method |
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