Online identification method and system for optimal efficiency of multi-stack hydrogen fuel cell system

Abstract

The invention belongs to the technical field of control, and particularly relates to an online identification method and system for the optimal efficiency of a multi-stack hydrogen fuel cell system, and the method comprises the steps: firstly obtaining the output current and output voltage of each hydrogen fuel cell during operation, and the real-time data of the real-time power demand of a power grid; calculating the real-time output power and efficiency of each hydrogen fuel cell according to the obtained real-time data; identifying the relationship between the efficiency of each hydrogen fuel cell and the output power based on a forgetting factor recursive least square method; and finally, solving the output power of each hydrogen fuel cell with the highest system efficiency by taking the system efficiency as an optimization target and combining a KKT condition, thereby improving the energy utilization efficiency of the whole system when the multi-stack hydrogen fuel cell system is in centralized operation for power generation, reducing the hydrogen consumption of the system, enabling the system to operate in a high-efficiency working area for most of the time, and reducing the energy consumption of the system. The system service life is prolonged and the system maintenance cost is saved.

Description

Technical Field

[0001] The present invention belongs to the field of energy management of a multi-stack hydrogen fuel cell system, and in particular relates to an online identification method and system for optimal efficiency of a multi-stack hydrogen fuel cell system. Background Art

[0002] In the context of traditional fossil energy facing many practical problems such as depletion and serious pollution, hydrogen fuel cell stacks are energy conversion devices that use hydrogen and oxygen electrochemical reactions to generate electricity. The final product is water, and it has the characteristics of negative emissions, no pollution, and high energy utilization. It is the direction of future new energy development. When facing high-power load scenarios, a single fuel cell has low output power, poor durability, and low reliability, so it is necessary to build a multi-stack fuel cell system to solve the above problems.

[0003] At present, the power of hydrogen fuel cells is basically below 100kW, and the power of high-power fuel cells on the market is 150-225kW. Due to technical limitations: excessive stacking of single-chip cells can easily lead to uneven chemical reactions inside the hydrogen fuel cell, resulting in a decrease in life; if a single chip fails, it will affect the output performance of the entire stack and cause damage to the entire hydrogen fuel cell stack. It is difficult to break through the output power of a single-stack fuel cell by an order of magnitude. For high-power application scenarios such as energy storage and power generation, a single-stack hydrogen fuel cell is obviously unable to meet actual needs, so multiple hydrogen fuel cells are required to operate in series to meet the power required by the power grid during energy storage and power generation. If the power distribution is reasonable, the multi-stack hydrogen fuel cell system can achieve better performance than the single-stack hydrogen fuel cell system in terms of power output, efficiency, hydrogen consumption and reliability, but it also increases the complexity of control.

[0004] Therefore, we need a real-time online power allocation method for multi-stack hydrogen fuel cell systems to improve system efficiency, reduce system hydrogen consumption, and thereby extend system operating life and reduce system operating and maintenance costs. Summary of the invention

[0005] The purpose of the present invention is to provide an online identification method for the optimal efficiency of a multi-stack hydrogen fuel cell system, to improve the system efficiency of the multi-stack hydrogen fuel cell system when generating electricity to the power grid, to reduce the system hydrogen consumption, to extend the system operating life, and to improve the system reliability.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] An online identification method for the optimal efficiency of a multi-stack hydrogen fuel cell system, wherein the multi-stack hydrogen fuel cell system and a power battery cooperate to supply power to a power grid; the multi-stack hydrogen fuel cell system includes a plurality of hydrogen fuel cells, and the power battery is used to maintain bus voltage stability. The online identification method for the optimal efficiency of the multi-stack hydrogen fuel cell system includes the following:

[0008] Calculate the real-time output power and real-time efficiency of each hydrogen fuel cell according to the real-time data of each hydrogen fuel cell during operation;

[0009] The real-time efficiency of each hydrogen fuel cell is used as output, and the real-time output power corresponding to each hydrogen fuel cell is used as input. The numerical parameters in the relationship between the efficiency and output power of each hydrogen fuel cell are identified based on the forgetting factor recursive least square method.

[0010] Taking system efficiency as the optimization goal, combined with the KKT condition, the output power of each hydrogen fuel cell that makes the system most efficient under the current real-time power demand of the power grid is solved.

[0011] As a more optimal technical solution of the present invention: the real-time data of the hydrogen fuel cell during operation includes output current, output voltage and real-time power of the power grid.

[0012] As a more optimal technical solution of the present invention: the real-time output power of the hydrogen fuel cell is obtained by multiplying the corresponding measured output voltage and output current, and the real-time efficiency of the hydrogen fuel cell is obtained by formula (1):

[0013]

[0014] Where: η FC is the efficiency of a single hydrogen fuel cell, P SFC is the power of a single hydrogen fuel cell, is the energy released by the consumed hydrogen, V SFC is the single-chip voltage of a single hydrogen fuel cell, F is the Faraday constant, and ΔH is the enthalpy change of hydrogen.

[0015] As a better technical solution of the present invention: the output power P of each hydrogen fuel cell that makes the system most efficient in step 4 SFC1 …P SFCn , based on the MATLAB nonlinear programming solver, combined with the KKT condition; the system efficiency is defined as the ratio of the sum of the output power of each battery stack P1 to the power P2 consumed by the system to generate P1, calculated by formula (2);

[0016]

[0017] Where P d is the power demand of the power grid, η MFCS Efficiency of multi-stack hydrogen fuel cell system.

[0018] Another object of the present invention is to provide an online identification system for the optimal efficiency of a multi-stack hydrogen fuel cell system, comprising:

[0019] A data acquisition module, the data acquisition module is used to obtain real-time data of the output current and output voltage of each hydrogen fuel cell during operation and the real-time power demand of the power grid;

[0020] An offline calculation module, the calculation module is used to calculate the real-time output power and real-time efficiency of each hydrogen fuel cell according to the acquired real-time data; and then use the real-time efficiency of each hydrogen fuel cell as output and the real-time output power corresponding to each hydrogen fuel cell as input, and identify the numerical parameters in the relationship between the efficiency and output power of each hydrogen fuel cell based on the forgetting factor recursive least squares method;

[0021] The online optimization module takes system efficiency as the optimization target and combines the KKT condition to solve the output power of each hydrogen fuel cell that makes the system most efficient under the current real-time power demand of the power grid.

[0022] Another object of the present invention is to provide a computer-readable storage medium having a program stored thereon, characterized in that when the program is executed by a processor, the steps in the online identification method of the optimal efficiency of a multi-stack hydrogen fuel cell system are implemented.

[0023] Another object of the present invention is to provide an electronic device, comprising a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor implements the steps in the method for online identification of the optimal efficiency of a multi-stack hydrogen fuel cell system when executing the program.

[0024] The beneficial effects are as follows:

[0025] The online identification method of the present invention can realize the online power allocation of a multi-stack hydrogen fuel cell system, and realizes the online identification of the relationship between the output power and efficiency of each hydrogen fuel cell through the forgetting factor recursive least squares method, so that the system power allocation can be performed online. Based on the MATLAB nonlinear programming solver, combined with the KKT condition solution, the online allocation of the output power of each hydrogen fuel cell is performed, so that the efficiency of the system is maximized.

[0026] The present invention can improve the efficiency and reliability of the system, reduce the hydrogen consumption of the system, and extend the operating life of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A method flow chart of a specific embodiment of the present invention.

[0028] Figure 2This is a structural schematic diagram of a system of a specific embodiment of the present invention applied to power grid power supply, wherein 1 is an air supply system, 2 is a hydrogen supply system, 3 is a hydrogen fuel cell, 4 is a DC / DC, 5 is a DC / AC inverter 5, 6 is a power battery, 7 is a power grid, and 8 is a multi-stack hydrogen fuel cell subsystem.

[0029] Figure 3 This is a diagram showing the output power and efficiency identification results of a hydrogen fuel cell according to a specific embodiment of the present invention.

[0030] Figure 4 This is a diagram showing the verification results of the power allocation strategy of two hydrogen fuel cells according to a specific embodiment of the present invention.

[0031] Figure 5 The figure is a comparison of system efficiency results under different power allocation strategies of a specific embodiment of the present invention.

[0032] Figure 6 This is a comparison chart of system hydrogen consumption results under different power allocation strategies of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with specific embodiments and drawings.

[0034] Example 1

[0035] The online identification method of the optimal efficiency of a multi-stack hydrogen fuel cell system provided in this embodiment is applied to a multi-stack hydrogen fuel cell system supplying power to a power grid. Figure 2 As shown, the online identification method is implemented by a multi-stack hydrogen fuel cell system and a power battery, which cooperate to supply power to the grid. The multi-stack fuel cell system is composed of multiple fuel cell stacks connected in series; the power battery can be a lithium phosphate battery, which is used to stabilize the bus voltage; Figure 4 As shown, in the multi-stack hydrogen fuel cell system of the present invention, n hydrogen fuel cells (hydrogen fuel cell 3, hydrogen fuel cell 2, ... hydrogen fuel cell n in the figure) are connected to form a multi-stack hydrogen fuel cell subsystem 8, whose output voltage is regulated by DC / DC 4, connected in parallel with the power battery 6 and then in series with the DC / AC inverter 5, and then the voltage is transmitted to the power grid 7. Each fuel cell is connected to the hydrogen supply module 2 and the air supply module 3 to form a hydrogen fuel cell. The process of the online identification method of the optimal efficiency of the multi-stack hydrogen fuel cell system is referred to as follows Figure 1 , as follows:

[0036] In the first step, a voltage sensor and a current sensor are used to obtain the real-time output voltage and current of each hydrogen fuel cell.

[0037] In the second step, the output power and efficiency of each hydrogen fuel cell are calculated based on the real-time output voltage and current of each hydrogen fuel cell obtained in the first step. The output power of the hydrogen fuel cell is obtained by multiplying the corresponding measured output voltage and output current, and the real-time efficiency of the hydrogen fuel cell is obtained by formula (1):

[0038]

[0039] Where η FC is the efficiency of a single hydrogen fuel cell, P SFC is the power of a single hydrogen fuel cell, is the energy released by the consumed hydrogen, V SFC is the single-chip voltage of a single hydrogen fuel cell, F is the Faraday constant, and ΔH is the enthalpy change of hydrogen.

[0040] In the third step, the output power and efficiency of each hydrogen fuel cell are calculated according to the second step, and the parameters of the relationship between the output power and efficiency of each hydrogen fuel cell are identified based on the forgetting factor recursive least squares method.

[0041] The formula of recursive least squares method with forgetting factor is as follows:

[0042]

[0043] The real-time efficiency of each hydrogen fuel is used as the output y(k), and the real-time output power corresponding to each hydrogen fuel is used as the input φ(k). The numerical parameters in the relationship between the efficiency and output power of each hydrogen fuel cell are identified based on the forgetting factor recursive least squares method. The efficiency value calculated based on the identified parameters Compared with the actual efficiency value y(k) of the hydrogen fuel cell, the identification result of Example 1 is as follows: Figure 3 As shown, from Figure 3 It can be seen that the forgetting factor recursive least squares method can accurately identify the parameters of the relationship between the output power and efficiency of each hydrogen fuel cell with basically no error.

[0044] The fourth step is to use the MATLAB nonlinear programming solver and the KKT condition to solve the power that should be allocated to each hydrogen fuel cell when the system efficiency is maximized, based on the relationship between the output power and efficiency of each hydrogen fuel cell calculated in the third step. SFC1 ...P SFCn , based on MATLAB nonlinear programming solver, combined with KKT conditions. When there are two hydrogen fuel cells in the system, the power allocation strategy results of the online identification method of the present invention are as follows Figure 4 The power distribution strategy is compared with the daisy chain power distribution and average power distribution system efficiency results. Figure 5 The power allocation strategy is compared with the hydrogen consumption results of the daisy chain power allocation and average power allocation system. Figure 6 As shown, it can be seen that the online power distribution method for the multi-stack hydrogen fuel cell system provided in this embodiment improves the efficiency of the system, reduces the hydrogen consumption of the system, thereby extending the operating life of the system and reducing the operating cost and maintenance cost of the system.

[0045] The present invention also provides a computer-readable storage medium in another embodiment, on which a program is stored, and when the program is executed by a processor, the steps in the online identification method of the optimal efficiency of a multi-stack hydrogen fuel cell system as described in Example 1 of the present invention are implemented.

[0046] The present invention also provides an electronic device in another embodiment, comprising a memory, a processor, and a program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps in the online identification method for the optimal efficiency of a multi-stack hydrogen fuel cell system as described in Example 1 of the present invention are implemented.

[0047] In another embodiment, the present invention provides an online identification system for optimal efficiency of a multi-stack hydrogen fuel cell system, comprising:

[0048] A data acquisition module, the data acquisition module is used to obtain real-time data of the output current and output voltage of each hydrogen fuel cell during operation and the real-time power demand of the power grid;

[0049] An offline calculation module, the calculation module is used to calculate the real-time output power and real-time efficiency of each hydrogen fuel cell according to the acquired real-time data; and then use the real-time efficiency of each hydrogen fuel cell as output and the real-time output power corresponding to each hydrogen fuel cell as input, and identify the numerical parameters in the relationship between the efficiency and output power of each hydrogen fuel cell based on the forgetting factor recursive least squares method;

[0050] The online optimization module takes system efficiency as the optimization target and combines the KKT condition to solve the output power of each hydrogen fuel cell that makes the system most efficient under the current real-time power demand of the power grid.

[0051] In the description of this specification, the reference term "another embodiment" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0052] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. An online identification method for the optimal efficiency of a multi-stack hydrogen fuel cell system, characterized in that: Includes the following: Calculate the real-time output power and real-time efficiency of each hydrogen fuel cell according to the real-time data of each hydrogen fuel cell during operation; The real-time efficiency of each hydrogen fuel cell is used as output, and the real-time output power corresponding to each hydrogen fuel cell is used as input. The numerical parameters in the relationship between the efficiency and output power of each hydrogen fuel cell are identified based on the forgetting factor recursive least square method. Taking system efficiency as the optimization goal, combined with the KKT condition, the output power of each hydrogen fuel cell that makes the system most efficient under the current real-time power demand of the power grid is solved.

2. The online identification method for the optimal efficiency of a multi-stack hydrogen fuel cell system as claimed in claim 1, characterized in that: The real-time data of the hydrogen fuel cell during operation includes output current, output voltage and real-time power of the power grid.

3. The online identification method for optimal efficiency of a multi-stack hydrogen fuel cell system as claimed in claim 1, characterized in that: The real-time output power of the hydrogen fuel cell is obtained by multiplying the corresponding measured output voltage and output current, and the real-time efficiency of the hydrogen fuel cell is obtained by formula (1): Where: η FC is the efficiency of a single hydrogen fuel cell, P SFC is the power of a single hydrogen fuel cell, is the energy released by the consumed hydrogen, V SFC is the single-chip voltage of a single hydrogen fuel cell, F is the Faraday constant, and ΔH is the enthalpy change of hydrogen.

4. The online identification method for optimal efficiency of a multi-stack hydrogen fuel cell system as claimed in claim 1, characterized in that: The output power P of each hydrogen fuel cell that makes the system most efficient SFC1 …P SFCn , based on the MATLAB nonlinear programming solver, combined with the KKT condition; the system efficiency is defined as the ratio of the sum of the output power of each battery stack P1 to the power P2 consumed by the system to generate P1, calculated by formula (2); Where P d is the power demand of the power grid, η MFCS Efficiency of multi-stack hydrogen fuel cell system.

5. An online identification system for the optimal efficiency of a multi-stack hydrogen fuel cell system, comprising: A data acquisition module, the data acquisition module is used to obtain real-time data of the output current and output voltage of each hydrogen fuel cell during operation and the real-time power demand of the power grid; An offline calculation module, the calculation module is used to calculate the real-time output power and real-time efficiency of each hydrogen fuel cell according to the acquired real-time data; and then use the real-time efficiency of each hydrogen fuel cell as output and the real-time output power corresponding to each hydrogen fuel cell as input, and identify the numerical parameters in the relationship between the efficiency and output power of each hydrogen fuel cell based on the forgetting factor recursive least squares method; The online optimization module takes system efficiency as the optimization target and combines the KKT condition to solve the output power of each hydrogen fuel cell that makes the system most efficient under the current real-time power demand of the power grid.

6. A computer-readable storage medium having a program stored thereon, characterized in that: When the program is executed by a processor, the steps in the online identification method of the optimal efficiency of a multi-stack hydrogen fuel cell system are implemented.

7. An electronic device comprising a memory, a processor, and a program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the steps in the online identification method of the optimal efficiency of a multi-stack hydrogen fuel cell system are implemented.

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