Method for controlling loading and unloading of fuel cell system

Abstract

The invention discloses a loading and unloading control method for a fuel cell system, which comprises the following steps of: firstly, establishing a parameter calibration table of an auxiliary component BOP to obtain a one-to-one correspondence relationship between a loading current value of a fuel cell stack and parameters of the auxiliary component BOP; in the stable operation process of the fuel cell system, if a system controller FCU receives a target loading current issued by an upper computer, after the current operation state is judged, loading or unloading variable working conditions are carried out in a loading and unloading mode controlled by two lines of the loading current and a BOP parameter respectively. According to the invention, the response speed of the system can be improved, stepless power regulation of the fuel cell system is realized, and the problems that a conventional system only loads specific current density and power output is discontinuous are avoided.

Description

TECHNICAL FIELD

[0001] The application relates to a fuel cell system loading and unloading control method, and belongs to the technical field of hydrogen energy and fuel cells. BACKGROUND

[0002] Hydrogen energy has become an important development direction of future energy due to its zero-carbon advantage. A fuel cell system is a device for converting hydrogen energy into electric energy and mainly comprises an upper computer, a fuel cell system controller FCU, a fuel cell stack, auxiliary components BOP and a power conversion device.

[0003] The auxiliary components BOP provide the fuel cell stack with hydrogen, air and cooling liquid with suitable temperature, pressure, flow rate and humidity, and comprise an air compressor, a hydrogen circulating pump, a water pump, a pressure control valve and a sensor. The power conversion device boosts the direct current of the fuel cell stack to a required voltage and supplies external power demand. The current of the fuel cell stack, i.e. the input current of the power conversion device, is realized by the power conversion device, and the voltage of the fuel cell stack is determined by the electrochemical reaction inside the stack and is automatically followed. The increase of the current drawn by the power conversion device also means that the consumption of hydrogen and oxygen increases and the heat generation increases, so the speed of the air compressor, the hydrogen circulating pump and the water pump needs to be increased and the opening degree of the pressure control valve needs to be adjusted.

[0004] A conventional fuel cell system generally sets multiple platform currents, and the parameters of the auxiliary components BOP are adjusted to the parameters of the next platform before the current drawn by the power conversion device is switched among the platforms. This method causes slow response of the output power of the fuel cell system and discontinuous output power. SUMMARY

[0005] The technical problem solved by the application is to overcome the shortcomings of the prior art and provide a fuel cell system loading and unloading control method, which optimizes the loading and unloading control process of the fuel cell system by adjusting the current drawn by the power conversion device and the parameters of the auxiliary components BOP.

[0006] The technical solution of the application is as follows:

[0007] A fuel cell system loading and unloading control method comprises the following steps:

[0008] S1: According to the demand of the fuel cell stack, a parameter calibration table of the auxiliary components BOP is established to obtain a one-to-one correspondence between the current drawn by the fuel cell stack and the parameters of the auxiliary components BOP.

[0009] S2: During the stable operation of the fuel cell system, if the system controller FCU receives a target current drawn from the upper computer, the current operating state is judged, and the working condition is changed: if loading is required, S3 is executed; if unloading is required, S4 is executed.

[0010] S3: The power conversion device increases the pull current with a set current loading slope N; at the same time, according to the target pull current and the current pull current, the following is performed:

[0011] When the pull current increase value is less than or equal to the set mutation value, the auxiliary component BOP parameter is directly assigned according to the auxiliary component BOP parameter value corresponding to the target pull current in the parameter calibration table;

[0012] When the pull current increase value is greater than the set mutation value, the mutation value is added to the current pull current, and the auxiliary component BOP parameter is first assigned according to the auxiliary component BOP parameter value corresponding to the added pull current in the parameter calibration table, and then increased in a manner greater than the current loading slope N;

[0013] When it is monitored that the current pull current and the target pull current are consistent, the variable condition ends;

[0014] S4: The power conversion device reduces the pull current and the auxiliary component BOP parameter value in a manner greater than the current loading slope N;

[0015] When it is monitored that the auxiliary component BOP parameter is consistent with the parameter corresponding to the target pull current in the parameter calibration table, the variable condition ends.

[0016] Further, the BOP parameters include but are not limited to air compressor speed, back pressure valve opening degree, hydrogen pressure target, hydrogen pump speed, hydrogen exhaust valve opening frequency, hydrogen exhaust valve opening time, water pump speed, and target temperature.

[0017] Further, if the target pull current value issued by the upper computer does not exist in the BOP parameter calibration table, the auxiliary component BOP parameter value corresponding to the target pull current value is obtained through the difference method.

[0018] Further, the BOP parameter calibration table is set with 0.1 current density as a step.

[0019] Further, in step S3, if the system controller FCU receives a new target pull current issued by the upper computer during the variable condition process, the new target pull current and the current target pull current are compared to determine whether to load or unload;

[0020] If it is loaded, the current variable load process is continued; after it is monitored that the pull current and the current target pull current are consistent, S3 is executed again according to the new target current; if it is unloaded, the new target pull current is used to replace the current target pull current, and S3 is executed again.

[0021] Further, in step S4, if the system controller FCU receives a new target pull load current from the upper computer during the variable working condition process, the new target pull load current is compared with the current target pull load current to determine whether to load or unload;

[0022] If it is loading, the current variable load process is continued; after the pull load current and the current target pull load current are consistent, the new target current is executed again in step S4; if it is unloading, the new target pull load current replaces the current target pull load current, and step S4 is executed again.

[0023] Further, in step S3 or S4, if the system controller FCU receives a “normal shutdown” or “emergency shutdown” instruction from the upper computer during the variable working condition process, the variable working condition is stopped, and the instruction is directly executed.

[0024] Further, in step S4, the power conversion device reduces the pull load current in a slope of 4N, and reduces the auxiliary component BOP parameter value in a slope of 3N.

[0025] Further, in step S4, the power conversion device reduces the pull load current for 1s, and then reduces the auxiliary component BOP parameter value.

[0026] Further, in step S3, when the pull load current increase value is greater than the set mutation value, the mutation value is added to the current pull load current, the auxiliary component BOP parameter is first assigned to the auxiliary component BOP parameter value corresponding to the added pull load current in the parameter calibration table, and then increased in a manner of 1.5N.

[0027] The advantages of the present application compared with the prior art are:

[0028] (1) The present application improves the system response speed by the load and unload mode controlled by the pull load current and the BOP parameter, realizes the stepless regulation of the fuel cell system power, and avoids the problem of discontinuous power output caused by the conventional system only pulling a specific current density.

[0029] (2) The present application realizes the avoidance of local starvation of the fuel cell stack (i.e., the supply of hydrogen and air is slightly higher than the demand of the fuel cell stack) during the load and unload process through reasonable load and unload design. BRIEF DESCRIPTION OF DRAWINGS

[0030] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a better understanding of the preferred embodiments, and are not to be considered as limitations on the present application. Moreover, in the entire drawings, the same reference numerals represent the same components. In the drawings:

[0031] Figure 1 It is a flow chart of the load and unload control method of the fuel cell system embodiment of the present application. Detailed Implementation

[0032] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0033] This invention proposes a method for load on / off control of a fuel cell system, such as... Figure 1 As shown:

[0034] S1: Establish BOP parameter calibration table

[0035] Based on the requirements of the fuel cell stack, a BOP parameter calibration table is set with a current density of 0.1 as the step, so as to obtain a one-to-one correspondence between the current value and the BOP parameter. The part between the two current steps is calculated by the difference to obtain the corresponding BOP parameter, thereby realizing the ability to respond to any target current within the allowable load range of the fuel cell stack.

[0036] The fuel cell stack is where the electrochemical reaction between hydrogen and oxygen in the air takes place. Because the effective area of ​​the membrane electrode assembly (MEA) varies in the stack, the rated load current differs. To evaluate the output characteristics of cells with different areas, the single-cell voltage characteristics under the same current density (load current / effective area) are generally used for evaluation, facilitating conversion between different fuel cells.

[0037] Under different current densities, the BOP auxiliary components need to supply hydrogen, air, and coolant to the fuel cell stack at different pressures, flow rates, and temperatures. In this embodiment, the BOP parameter calibration is shown in Table 1. The parameters include load current (current density), air compressor speed, back pressure valve opening, target hydrogen pressure (air pressure plus a specific value), hydrogen pump speed, hydrogen exhaust valve opening frequency, hydrogen drain valve opening duration, water pump speed, and target temperature.

[0038] Table 1. Meaning of BOP parameter calibration

[0039]

[0040]

[0041] S2: During stable system operation, the system controller FCU receives the target current from the host computer, determines the current operating status, and then performs a change of operating condition: if loading is required, execute S3; if unloading is required, execute S4.

[0042] S3: the power conversion device increases the pull current at a set slope N, different fuel cell stacks allow different pull current change rates, for example, a certain type of fuel cell stack allows a pull rate of 10 A / s.

[0043] At the same time, according to the target current and the current, the following is performed:

[0044] When the pull current increase value is less than or equal to 0.06 C, the BOP state is directly assigned according to the working condition parameters corresponding to the target current in the BOP parameter calibration table;

[0045] When the pull current increase value is greater than 0.06 C, first, the mutation value of 0.06 C is assigned, and then the working condition is changed in a manner greater than the current loading slope, as shown in Table 2:

[0046] Table 2 BOP state change table

[0047] Auxiliary component BOP BOP loading BOP mutation Parameters corresponding to 0.06 electric density BOP working parameter change slope (A / s) 1.5N

[0048] For example, the current pull current increases from 280 A to 560 A (1.6 C), and the air compressor speed is taken as an example. According to the BOP parameter calibration table, 280 A (0.8 C) corresponds to 7.1 w, first, the mutation of 0.06 C is performed, that is, the air compressor speed corresponding to 0.86 C is changed, that is, the difference is calculated to obtain the speed of 7.4 w, and then the speed is increased according to the BOP parameters corresponding to the pull current change rate of 1.5 N, until the speed of 9.7 w corresponding to 560 A is loaded.

[0049] When the loading current and the target current are consistent, the working condition is changed; if the system controller FCU receives a new instruction from the upper computer during the working condition change process, S5 is performed.

[0050] S4: the power conversion device reduces the pull current at a slope of 4N; in addition, after a delay of 1s, the BOP parameter value is reduced at a slope of 3N.

[0051] When the BOP parameter is consistent with the working condition parameter corresponding to the target current in the BOP parameter calibration table, the working condition is changed; if the system controller FCU receives a new instruction from the upper computer during the working condition change process, S5 is performed.

[0052] S5: according to the new instruction content, the following is performed:

[0053] If the new instruction is a "normal shutdown" or "emergency shutdown" instruction, the new instruction is directly executed, and the process ends.

[0054] If the new instruction is a new target current: compare the new target current with the current target current to determine whether to load or unload;

[0055] If the load is increased, the original step is returned to be executed, and after the original load change process is executed, S3 is executed again according to the new target current; if the load is decreased, the new target current is directly used to replace the current target current, and the original step is returned to be executed.

[0056] The above-described embodiments are only the preferred specific embodiments of the present application, and the common changes and replacements made by the skilled in the art within the technical scheme of the present application should be included in the protection scope of the present application.

Claims

1. A method for load on / off control of a fuel cell system, characterized in that, include: S1: Based on the requirements of the fuel cell stack, establish a parameter calibration table for the auxiliary component BOP to obtain a one-to-one correspondence between the load current value of the fuel cell stack and the parameters of the auxiliary component BOP. S2: During the stable operation of the fuel cell system, if the system controller FCU receives the target load current from the host computer, it will determine the current operating status and then perform a change of operating condition: if loading is required, execute S3; if unloading is required, execute S4. S3: The power conversion equipment increases the load current at a set current loading slope N; simultaneously, based on the target load current and the current load current, it executes: When the increase in load current is less than or equal to the set sudden change, the auxiliary component BOP parameter is directly assigned the value according to the auxiliary component BOP parameter value corresponding to the target load current in the parameter calibration table. When the increase in load current exceeds the set mutation amount, the mutation amount is added to the current load current. The auxiliary component BOP parameter is first assigned according to the auxiliary component BOP parameter value corresponding to the superimposed load current in the parameter calibration table, and then increased in a way that is greater than the current loading slope N. The variable operating condition ends when the current load current and the target load current are detected to be consistent. S4: Power conversion equipment reduces load current and lowers the BOP parameter value of auxiliary components by using a current loading slope N greater than the current loading slope N. The variable operating condition ends when the BOP parameter of the auxiliary component is found to be consistent with the parameter corresponding to the target load current in the parameter calibration table.

2. The method for load on / off control of a fuel cell system according to claim 1, characterized in that, BOP parameters are calibrated based on the load current and the corresponding current density, including but not limited to air compressor speed, back pressure valve opening, hydrogen pressure target, hydrogen pump speed, hydrogen exhaust valve opening frequency, hydrogen drain valve opening duration, water pump speed, and target temperature.

3. A method for load control of a fuel cell system according to claim 1 or 2, characterized in that, If the target load current value issued by the host computer is not found in the BOP parameter calibration table, the auxiliary component BOP parameter value corresponding to the target load current value can be obtained by the difference method.

4. The method for load control of a fuel cell system according to claim 2, characterized in that, Set up the BOP parameter calibration table with a current density step of 0.

1.

5. The method for load control of a fuel cell system according to claim 1, characterized in that, In step S3, if the system controller FCU receives a new target load current from the host computer during the changing operating condition process, the new target load current is compared with the current target load current to determine whether to increase or decrease the load. If it is a loading process, continue executing the current loading process; After detecting that the load current is consistent with the current target load current, execute S3 again according to the new target current; If the load is reduced, replace the current target load current with the new target load current and execute S3 again.

6. The method for load on / off control of a fuel cell system according to claim 1, characterized in that, In step S4, if the system controller FCU receives a new target load current from the host computer during the changing operating condition process, the new target load current is compared with the current target load current to determine whether to increase or decrease the load. If it is a loading process, continue executing the current loading process; After detecting that the load current is consistent with the current target load current, execute S4 again according to the new target current; If the load is reduced, replace the current target load current with the new target load current and execute S4 again.

7. The method for load on / off control of a fuel cell system according to claim 1, characterized in that, In step S3 or S4, if the system controller FCU receives a "normal shutdown" or "emergency shutdown" command from the host computer during the change of operating conditions, the change of operating conditions is stopped and the command is executed directly.

8. The method for load control of a fuel cell system according to claim 1, characterized in that, In step S4, the power conversion equipment reduces the load current with a slope of 4N and reduces the BOP parameter value of the auxiliary components with a slope of 3N.

9. The method for load control of a fuel cell system according to claim 1, characterized in that, In step S4, after the power conversion equipment reduces the load current by 1 second, it reduces the BOP parameter value of the auxiliary components.

10. The method for load control of a fuel cell system according to claim 1, characterized in that, In step S3, when the increase in load current is greater than the set mutation amount, the mutation amount is added to the current load current. The auxiliary component BOP parameter is first assigned according to the auxiliary component BOP parameter value corresponding to the superimposed load current in the parameter calibration table, and then increased by 1.5N.

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