Integrated reversible fuel cell mode switching control system and method

Abstract

The application relates to a one-piece reversible fuel cell mode switching control system and method for controlling the conversion of a one-piece reversible fuel cell from an electrolysis mode to a power generation mode, including an electrolysis stopping stage, a purging stage and a power generation starting stage, wherein: in the electrolysis stopping stage, the water passage of the fuel cell is closed, the air compressor or other oxygen source and the air inlet are opened, and the air outlet water flow is less than a threshold value; in the purging stage, the oxygen side of the fuel cell is purged, the water content of the membrane is monitored in real time during the purging process, and the purging gas flow is adjusted to the optimal flow under the water content in real time when the water content reaches different stages; and in the power generation starting stage, the air compressor or other oxygen source is adjusted to the power generation mode, the hydrogen inlet is opened, and power generation is performed. Compared with the prior art, the application simplifies the pipeline design and control process and improves the mode switching efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fuel cells, in particular to a unitized regenerative fuel cell mode switching control system and method. BACKGROUND

[0002] Hydrogen energy, a clean energy with no pollution and high energy storage density, is a hot topic to solve the problem of rapid reduction of fossil fuel reserves and energy depletion. Unitized regenerative fuel cell (URFC) has both power generation and electrolysis functions, which can generate electricity using hydrogen energy and produce hydrogen using primary energy. The specific energy is up to 1000 Wh / kg, and it has the advantages of no self-discharge and no battery capacity limit, etc. It is a high-efficiency and environmentally friendly energy storage system.

[0003] The unitized regenerative fuel cell has the functions of fuel cell (FC) and electrolysis cell (WE). In power generation mode, the hydrogen and oxygen gas inputted are subjected to electrochemical reaction, the oxygen electrode is O2+4H + +4e→2H2O, the hydrogen electrode is H2-2e→2H + , and the output is electric energy; in electrolysis mode, the stored water is electrolyzed into hydrogen and oxygen by external electric energy, the oxygen electrode is 2H2O-4e→O2+4H + , and the hydrogen electrode is 2H + +2e→H2. When the unitized regenerative fuel cell is switched from electrolysis mode to power generation mode, the oxygen side of the cell is full of electrolytic water, which cannot directly generate electricity. Therefore, it is necessary to blow out a large amount of water in the cell, while not making the membrane electrode too dry, and a certain amount of water needs to be reserved to smoothly complete the mode switching. However, the existing mode switching blowing method is mostly fixed flow blowing, which is time-consuming and low in efficiency, resulting in a long idle time during the operation of the unitized regenerative fuel cell, which is not conducive to the efficient operation of the system.

[0004] Through literature retrieval of the prior art, it is found that the regeneration fuel cell starting method disclosed in Chinese invention patent CN 108390083 A only monitors voltage and current, the evaluation conditions are not comprehensive enough, and the safety is low. The fuel cell purging method disclosed in Chinese invention patent CN114865014 A is only applicable to fuel cell shutdown, the method mentioned in the patent is not applicable to the state of the battery oxygen side filled with water after electrolysis is completed, nor is it applicable to the power generation starting state of retaining a certain amount of water after purging is completed, and the segmented strategy cannot maximize the efficiency. The purging strategy disclosed in Chinese invention patent CN111029623A has a large gas flow and takes a long time, and the purging efficiency is low, which is not suitable for short-time requirements of mode switching. Chinese invention patent CN113839068A discloses an intermittent multiple purging strategy, and the purging time of the constant current and constant voltage strategy is long, which is not suitable for short-time requirements of mode switching, and the system is too complex and has poor economy. SUMMARY

[0005] The purpose of the present application is to overcome the defects of the prior art and provide an integrated reversible fuel cell mode switching control system and method, which shortens the mode switching time, reduces the gas consumption, ensures the safety of mode switching, simplifies the pipeline arrangement and control process of the system, and improves the mode switching efficiency.

[0006] The purpose of the present application can be achieved by the following technical solutions: an integrated reversible fuel cell mode switching control method for controlling an integrated reversible fuel cell to switch from an electrolysis mode to a power generation mode, including an electrolysis stopping phase, a purging phase and a power generation starting phase, wherein:

[0007] In the electrolysis stopping phase, the water passage of the fuel cell is closed, the air compressor or other oxygen source and the air inlet are opened, and when the water flow of the air outlet is less than a threshold value, the air outlet communication passage is switched;

[0008] In the purging phase, the oxygen side of the fuel cell is purged, and the water content of the membrane is monitored in real time during the purging process. When the water content reaches different stages, the purging gas flow is adjusted to the optimal flow at the water content in real time;

[0009] In the power generation starting phase, the air compressor or other oxygen source is adjusted to the power generation mode, and the hydrogen inlet is opened for power generation.

[0010] Preferably, the threshold value of the water flow of the air outlet in the electrolysis stopping phase is 1 ml / s.

[0011] Preferably, in the purging phase, the control basis for controlling the purging flow is obtained through two pre-experiments, and the purging gas flow is changed in real time according to the water content in the fuel cell:

[0012] Pre-experiment 1: Obtain the corresponding relationship between the high frequency impedance value of the fuel cell and the water content in the fuel cell, take the water content at the start of the fuel cell mode as the minimum value, take the water content at the end of the electrolysis mode as the maximum value, and the mode switching is completed after the water content changes from the maximum value to the minimum value, and the purging is stopped;

[0013] Pre-experiment 2: Measure the water content change curve in the fuel cell under different purging gas flow rates in the way of constant flow and constant pressure purging;

[0014] During the purging process, the water content in the membrane is monitored by monitoring the high frequency impedance of the fuel cell. In different stages of water content, the best gas flow rate is calculated according to the data of pre-experiment 2, so as to change the purging gas flow rate in real time, and the best flow control strategy of the purging process is obtained.

[0015] Preferably, pre-experiment 1 is purging at 0.1A / cm 2 The weight change curve of the battery during mode switching purging is measured by a precision mass meter, the water content change curve in the fuel cell is obtained by reflecting the water content change through the weight change, and the high frequency impedance value corresponding to the water content is recorded, and the water content in the fuel cell is monitored by the high frequency impedance value of the battery.

[0016] The gas flow rate of pre-experiment 2 is taken as the air flow rate on the oxygen side under different current densities with back pressure 0kPa, and the current density is taken in the range of 0.2A / cm 2 ~3A / cm 2 , every 0.1A / cm 2 .

[0017] Preferably, the purging speed represents the speed of the water content from the starting value to the final value, which is the slope of the water content-time curve;

[0018] Preferably, the purging safety standard is that the purging flow rate does not exceed the safety value, and the safety value a safe The calculation method is:

[0019] a safe =a 0.5 *k*p

[0020] Wherein, a 0.5 is the air inlet flow rate on the oxygen side at 0.5A / cm 2 current density;

[0021] k is a proportional coefficient, which is different for different stacks, and the value is 2.5-4;

[0022] p is the water content percentage, which is 0-1, 1 when the stack is full of water, and 0 when it is completely dry;

[0023] Under the condition that the purge flow does not exceed the safety value, the membrane electrode is not damaged after the purge is completed, and the battery performance is not reduced after switching to the power generation mode.

[0024] The specific evaluation method of the comprehensive standard is:

[0025] For different water contents, the actual purge flow does not exceed the safety value under the water content, and the purge speed and gas consumption are evaluated with different proportions. The evaluation proportion of the purge speed is much higher than that of the gas consumption. The comprehensive score Score formula is as follows:

[0026] Score=m*P speed +n*P consumption

[0027] Wherein, P speed is the purge speed score, and the purge flow corresponding to the fastest purge speed in the safety value range is 100 points;

[0028] P consumption is the gas consumption score, and the purge flow corresponding to the minimum gas consumption in the safety value range is 100 points;

[0029] m is the evaluation proportion of the purge speed;

[0030] n is the evaluation proportion of the gas consumption, and m+n=1;

[0031] This strategy pays more attention to switching speed, and the evaluation proportion m of the purge speed should be not less than 0.8. The comprehensive evaluation score of different purge gas flows under the water content is obtained, and the purge gas flow value with the highest score is selected as the best purge flow under the water content. Thus, the purge flow curve varying with the water content is fitted. In the actual purge process, the water content is monitored in real time by the high-frequency impedance of the battery, and the flow is adjusted to the best purge flow under the water content by the control program in real time.

[0032] After the purge stage is completed, the power generation start stage is entered, the hydrogen source and the hydrogen inlet and outlet switch are opened, the air compressor or other oxygen source is adjusted to the power generation mode, and ventilation is performed at a standard gas inlet amount of 0.5A / cm 2 The battery voltage is monitored, and if the voltage of any battery within 20s is not lower than the warning value 0.4V, it is considered that the battery can normally perform the power generation mode. If the voltage of the battery is lower than the warning value, the hydrogen source and the hydrogen inlet and outlet are closed, and the constant pressure and constant flow purge is continued. The purge flow is the safety value under the water content, and then the safety detection is performed again until it is passed.

[0033] The application also provides an integrated reversible fuel cell mode switching control system for implementing the above method, comprising a stack, a hydrogen source, an air source, a hydrogen storage device, a high-frequency impedance measuring instrument, a cooling water tank and an electrolytic water tank.

[0034] wherein,

[0035] The electrolytic water tank is connected with the stack through an electrolytic water inlet and outlet pipeline, and an electrolytic water inlet switch valve and an electrolytic water outlet switch valve are respectively arranged on the electrolytic water inlet and outlet pipeline.

[0036] The cooling water tank is connected with the stack through a cooling water inlet and outlet pipeline, and a cooling water inlet switch and a cooling water outlet switch are respectively arranged on the cooling water inlet and outlet pipeline.

[0037] A hydrogen inlet switch is arranged on the connecting pipeline between the hydrogen source and the stack, and an air inlet switch is arranged on the connecting pipeline between the air source and the stack; the high-frequency impedance measuring instrument is connected with the stack.

[0038] The air outlet of the stack has two passages, passage one is connected to the electrolytic water tank, and an air outlet first switch is arranged on the passage one, and passage two is connected to the atmospheric environment, and an air outlet second switch is arranged on the passage two.

[0039] During electrolysis, the electrolytic water inlet switch valve and the electrolytic water outlet switch valve are both opened, the hydrogen outlet switch is opened, the hydrogen inlet switch is closed, and the air inlet and outlet switches are both closed, the electrolytic water pump pumps water from the electrolytic water tank to the stack, and the remaining electrolytic water after the reaction flows into the electrolytic water tank through the outlet for circulation.

[0040] When the mode switching instruction is issued, the system enters the electrolysis stopping stage, the electrolytic water pump is closed, the electrolytic water inlet and outlet switches are closed after 1s, the air inlet switch and the air outlet first switch are opened, the air compressor or other oxygen source is opened, the constant pressure and constant flow purging is performed, the air outlet water flow is less than the threshold 1ml / s, the air outlet second switch is opened, the air outlet first switch is closed, and the purging stage is entered.

[0041] The stack is provided with end plates adapted to the mode switching strategy, and the end plates have a total of 8 inlets and outlets, the inlets and outlets on the end plates and the stack core jointly constitute a flow circulation loop, including a cooling water path, a hydrogen path, an air path and an electrolytic water path, and the electrolytic water path and the air path are connected through the polar plate in the stack, and the cooling water path and the hydrogen path are completely independent passages.

[0042] Compared with the prior art, the application has the following advantages:

[0043] 1. The application divides different stages of mode switching, controls according to the characteristics of each stage, and the switching process is more concise and efficient.

[0044] 2. The present application can calibrate different models of integrated reversible fuel cells through pre-experiment, develop optimal mode switching purge strategy, and has wide applicability.

[0045] 3. The present application realizes real-time regulation through feedback variable flow purge, which can effectively improve the purge efficiency of mode switching, and the evaluation standard considers both purge speed and purge safety, greatly improves the purge speed under the premise of ensuring the safe operation of power generation mode, reduces the mode switching time, effectively reduces the stagnation time of mode switching, reduces the gas consumption, reduces the energy consumption of the purge process, and effectively improves the comprehensive performance of the integrated reversible fuel cell system.

[0046] 4. The end plate configuration of the present application realizes that the electrolysis mode uses the electrolysis water inlet and outlet alone, and the power generation mode uses the air inlet and outlet alone, which simplifies the pipeline design and control process, and improves the mode switching efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 It is a basic flowchart of the mode switching strategy of the integrated reversible fuel cell.

[0048] Figure 2 It is a basic flowchart of the optimal control strategy of the oxygen side purge stage of the mode switching of the integrated reversible fuel cell.

[0049] Figure 3 It is a curve of the water content represented by the high-frequency impedance value in the cell changing with time under different flow rates when the integrated reversible fuel cell is purged during mode switching in Example 1.

[0050] Figure 4 It is a curve of the water content represented by the high-frequency impedance value in the cell changing with time when the optimal purge strategy is used when the integrated reversible fuel cell is purged during mode switching in Example 1.

[0051] Figure 5 It is a schematic diagram of the integrated reversible fuel cell system.

[0052] In the figure, 1 is an electrolysis water inlet switch, 2 is an electrolysis water outlet switch, 3 is a cooling water inlet switch, 4 is a cooling water outlet switch, 5 is a high-frequency impedance measuring instrument, 6 is a stack, 7 is an air inlet switch, 8 is an air outlet first switch, 9 is an air outlet second switch, 10 is a hydrogen inlet switch, 11 is a hydrogen outlet switch, 12 is an air compressor, 13 is a cooling water tank, 14 is an electrolysis water tank, 15 is a hydrogen tank, and 16 is a hydrogen storage device.

[0053] Figure 6 It is a schematic diagram of the end plate of the integrated reversible fuel cell.

[0054] In the diagram, 301 is the inlet for electrolyzed water, 302 is the outlet for electrolyzed water, 303 is the inlet for cooling water, 304 is the outlet for cooling water, 305 is the inlet for air, 306 is the outlet for air, 307 is the inlet for hydrogen, and 308 is the outlet for hydrogen. Detailed Implementation

[0055] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0056] The purpose of this invention is to provide an integrated reversible fuel cell mode switching oxygen side purging strategy and a suitable endplate structure, which shortens the mode switching time, reduces gas consumption, ensures the safety of mode switching, simplifies the system's piping layout and control process, and improves mode switching efficiency.

[0057] The integrated reversible fuel cell mode switching control system that specifically implements the above control method is, for example... Figures 5-6 As shown: Includes fuel cell stack 6 (i.e., integrated reversible fuel cell stack), hydrogen source (preferred). Figure 5 Hydrogen tank 15), air source (preferred) Figure 5 The system includes an air compressor 12, a hydrogen storage device 16, a high-frequency impedance meter 5, a cooling water tank 13, and an electrolysis water tank 14; among which,

[0058] The electrolytic water tank 14 is connected to the fuel cell stack 6 through an electrolytic water inlet and outlet pipeline, and an electrolytic water inlet switch valve 1 and an electrolytic water outlet switch valve 2 are respectively provided on the electrolytic water inlet and outlet pipeline;

[0059] The cooling water tank 13 is connected to the fuel cell stack 6 via cooling water inlet and outlet pipes, and a cooling water inlet switch 3 and a cooling water outlet switch 4 are respectively provided on the cooling water inlet and outlet pipes;

[0060] A hydrogen inlet switch 10 is provided on the connecting pipe between the hydrogen tank 15 and the fuel cell stack 6, and an air inlet switch 7 is provided on the connecting pipe between the air compressor 12 and the fuel cell stack 6; a high-frequency impedance meter 5 is connected to the fuel cell stack 6.

[0061] The fuel cell stack 6 has two air outlets. One outlet is connected to the electrolysis tank 14 and is equipped with a first air outlet switch 8. The other outlet is connected to the atmospheric environment and is equipped with a second air outlet switch 9.

[0062] The electric pile 6 is provided with end plates at both ends, which are adapted to the mode switching strategy. The end plates have a total of 8 inlets and outlets. The inlets and outlets on the end plates and the battery core jointly form a flow circulation loop, which includes a cooling water circuit, a hydrogen circuit, an air circuit and an electrolytic water circuit. The electrolytic water circuit and the air circuit are connected through the polar plate inside the electric pile. The cooling water circuit and the hydrogen circuit are completely independent circuits. Figure 6 As shown in the figure, the lowermost part is the electrolytic water inlet 301 and the cooling water inlet 303, respectively. The upper part is the cooling water outlet 304 and the electrolytic water outlet 302. The air inlet 305 is located on the upper side and adjacent to the electrolytic water outlet 302. The air outlet 306 is located on the lower side and adjacent to the electrolytic water inlet 301. The hydrogen inlet 307 is located on the upper side and adjacent to the cooling water outlet 304. The hydrogen outlet 308 is located on the lower side and adjacent to the cooling water inlet 303. The hydrogen and air inlets and outlets are staggered. The inlets and outlets on the end plates and the battery core jointly form a flow circulation loop, which includes a cooling water circuit, a hydrogen circuit, an air circuit and an electrolytic water circuit. The electrolytic water circuit and the air circuit are connected through the polar plate inside the electric pile. The cooling water circuit and the hydrogen circuit are completely independent circuits.

[0063] During electrolysis, the electrolytic water inlet and outlet switch valves 1 and 2 are opened, the hydrogen outlet switch 11 is opened, the hydrogen inlet switch 10 is closed, and the air inlet and outlet switches are closed. The electrolytic water pump pumps water from the electrolytic water tank 14 to the electric pile 6. The remaining electrolytic water after the reaction flows into the electrolytic water tank 14 for circulation;

[0064] When the mode switching instruction is issued, the system enters the electrolysis stop stage. The electrolytic water pump is closed. After 1s, the electrolytic water inlet and outlet switches are closed, the air inlet switch 7 and the air outlet first switch 8 are opened, the air compressor or other oxygen source is opened, the constant pressure and constant flow purging is performed, the air outlet water flow is less than the threshold value 1ml / s, the air outlet second switch 9 is opened, and the air outlet first switch 8 is closed. Enter the purging stage;

[0065] The above system is controlled to realize the control process of converting the integrated reversible fuel cell from the electrolysis mode to the power generation mode, which is divided into three stages: the electrolysis stop stage, the purging stage and the power generation start stage, as shown in the figure: Figure 1 Mode switching starts, and enters the electrolysis end stage

[0066] S01, close the electrolytic water path of the battery, open the air inlet and outlet, and open the air compressor or other oxygen source for constant pressure and constant flow purging;

[0067] S02, judge whether the air outlet water flow reaches the threshold value, if not, enter S03, if yes, enter S04;

[0068] S03, continue constant flow purging, and return to S02;

[0069] S04, monitoring the high-frequency impedance value in real time, monitoring the water content of the battery, implementing optimal purge flow control, and implementing adjustment of the purge gas flow;

[0070] S05, determining whether the high-frequency impedance value reaches the threshold value, if not, entering S06, if yes, entering S07;

[0071] S06, continue variable flow purging, and return to S05;

[0072] S07, hydrogen inlet and outlet and hydrogen source are opened, air compressor or other oxygen source is adjusted to power generation mode, both sides are ventilated with standard gas amount;

[0073] S08, determining whether the voltage of each battery is higher than the dangerous value, if not, entering S09, if yes, entering S010;

[0074] S09, continue constant flow purging, and return to S08;

[0075] S10, mode switching is completed.

[0076] The purging stage purges the oxygen side of the battery. First, through two pre-experiments, the best purge gas flow corresponding to different water contents is obtained as the control basis for purging flow, so as to obtain the best flow control strategy for the purging process, taking the purging speed, gas consumption, and purging safety as the comprehensive standards. Then, the water content is monitored in real time by the high-frequency impedance value of the battery, and the purge gas flow is changed according to the water content, and the best flow control strategy is implemented. The basic process is as shown in Figure 2

[0077] Pre-experiment one (S21) is to perform a small flow constant speed purging on the oxygen side with purging gas when mode switching is performed after electrolysis. The change curve of the battery weight with time during the purging process is measured by a precision mass meter, so as to obtain the change curve of the water content in the battery with time, and the change curve of the high-frequency impedance value of the battery with time is recorded, so as to obtain the corresponding relationship between the high-frequency impedance value of the battery and the water content of the battery (S22).

[0078] Pre-experiment two (S23) is to select different purging gas flows to perform multiple independent mode switching purging, and record the change curve of the water content in the battery with time in each experiment, so as to obtain the water content-time change curve under different flows (S24).

[0079] The purging speed, gas consumption, and purging safety are evaluated (S25): the actual purging flow does not exceed the safety value under this water content, the purging speed and gas consumption are evaluated according to different proportions, in particular, the purging speed evaluation proportion should be much larger than the gas consumption, and this strategy pays more attention to switching speed, and the evaluation proportion of the purging speed should be not less than 0.8. ​

[0080] After obtaining the comprehensive evaluation score of different flow rates at the water content, the flow rate with the highest score is selected as the optimal purging flow rate at the water content, so as to fit the purging flow rate curve varying with the water content (obtain the optimal purging gas amount S26 at different water contents). In the actual purging process, the water content is monitored in real time by the high-frequency impedance of the battery, and the flow rate is adjusted to the optimal purging flow rate at the water content in real time by the control program.

[0081] The purging gas amount S27 is adjusted according to the real-time water content of the battery, and the purging stage ends S28.

[0082] The application will be described in detail below through specific embodiments:

[0083] Example 1

[0084] For a certain type of integrated reversible fuel cell stack, the mode switching purging stage strategy is formulated and tested. In this embodiment, the purging gas is air. The cell number is 2, the reaction area is 160 cm 2 .

[0085] First, the battery is in the state after the electrolysis stops, and is purged at a small flow rate. The weight change curve of the battery during the mode switching purging process is measured by a precision mass measuring instrument with an accuracy of 0.01 g, and the water content change curve of the battery with time is obtained. The water content at the start of the fuel cell mode is the minimum value, the water content at the end of the electrolysis mode is the maximum value, and the water content changes from the maximum value to the minimum value after the mode switching is completed. At the same time, the high-frequency impedance value of the battery is recorded by a high-frequency impedance instrument, and the corresponding relationship between the high-frequency impedance value of the battery and the water content of the battery is obtained.

[0086] The value of the gas flow rate is the air intake amount on the oxygen side of the battery at different current densities under a back pressure of 0 kPa, and the gas flow rate is selected as shown in the following table:

[0087]

[0088]

[0089] Repeat the process of placing the battery in the electrolysis end state, selecting different flow rates for mode switching purging, and recording the water content change curve of the battery represented by the high-frequency impedance with time as shown in Figure 3The slope of each point on the water content change curve over time is calculated to obtain the purge rate, thereby characterizing the speed of water content change. The gas consumption under a certain small water content change is calculated by the product of gas flow and time. The purge safety standard is made according to different water content segments. The actual purge flow under each water content segment does not exceed the maximum purge flow of the segment, which is recorded as the safety value. When the purge flow is switched to the end of the mode, the membrane electrode is not damaged, and the battery performance is not reduced after switching to the power generation mode. In particular, the safety value of the purge flow is different when the water content in the stack is different. When the water content is higher than 80%, the safety value is 7L / min, and when the water content is less than 20%, the safety value is 1.35L / min.

[0090] The actual purge flow does not exceed the safety value under the water content, and when the optimal purge gas amount is evaluated, the proportion of the purge rate is 0.9, and the proportion of the gas consumption is 0.1. Thus, the comprehensive evaluation score of different purge flows under each water content segment is obtained, and the highest score is selected as the optimal purge flow under the water content, thereby fitting the purge flow curve changing with the water content. Through Figure 5 The actual test is carried out on the device, the water content of the battery is monitored in real time by the high-frequency impedance instrument 5, the air compressor 12 is adjusted in real time by the control program, the flow is adjusted to the optimal flow under the water content, and thus the water content change curve over time characterized by the high-frequency impedance is obtained as shown in Figure 4 The actual test is carried out on the device, the water content of the battery is monitored in real time by the high-frequency impedance instrument 5, the air compressor 12 is adjusted in real time by the control program, the flow is adjusted to the optimal flow under the water content, and thus the water content change curve over time characterized by the high-frequency impedance is obtained as shown in

[0091] The common flow is 0.5A / cm 2 Compared with the normal pressure constant flow mode switching purge strategy corresponding to the oxygen side gas inlet flow, the normal pressure variable flow strategy in Example 1 reduces the purge time by 60% and reduces the gas consumption by 40%.

[0092] Example 2

[0093] The mode switching strategy test is carried out on a certain type of integrated reversible fuel cell stack

[0094] Specifically, the purge gas in this embodiment is air. The battery node is 2 nodes, the reaction area is 160cm 2 .

[0095] First, the battery is in an electrolysis state. During electrolysis, the electrolysis water inlet switch 1 and the electrolysis water outlet switch 2 are both opened, the hydrogen gas outlet switch 11 is opened, the hydrogen gas inlet switch 10 is closed, the air inlet switch 7, the air outlet first switch 8 and the air outlet second switch 9 are all closed, the electrolysis water pump pumps water from the electrolysis water tank 14 to the integrated reversible fuel cell stack 6, and the reacted electrolysis water flows into the electrolysis water tank 14 for circulation.

[0096] When the mode switching instruction is sent, the system enters the electrolysis stopping stage, the electrolysis water pump is closed, the electrolysis water inlet switch 1 and the electrolysis water outlet switch 2 are closed after 1s, the air inlet switch 7 and the air outlet first switch 8 are opened, the air compressor 12 is opened, the air outlet second switch 9 is opened after the air outlet water flow is less than the threshold value, the air outlet first switch 8 is closed, and the system enters the purging stage.

[0097] The purging stage uses air to purge the oxygen side of the battery, the air compressor 12 is in the purging mode, the flow rate can be controlled, the real-time high-frequency impedance is obtained through the high-frequency impedance meter 5 during the purging process, so as to monitor the water content of the battery, and when the water content reaches different values, the purging gas flow is changed in real time according to the corresponding relationship between the optimal purging flow and the water content obtained in embodiment 1;

[0098] In the power generation starting stage, the hydrogen inlet switch 10 and the hydrogen outlet switch 11 are opened, the air compressor 12 is adjusted to the power generation mode, air is passed at a standard air intake amount of 0.5A / cm 2 2 of 1.69L / min, the voltages of each battery are monitored, and if the voltage of any battery is lower than the warning value of 0.4V within 20s, the mode switching is completed.

[0099] The above description of the embodiments is for the convenience of the ordinary skilled in the art to understand and use the application. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without creative labor. Therefore, the present application is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art according to the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. An integrated reversible fuel cell mode switching control method for controlling an integrated reversible fuel cell to switch from an electrolysis mode to a power generation mode, characterized by, The method comprises an electrolysis stopping stage, a purging stage and a power generation starting stage, wherein: The electrolysis stopping stage: closing the water electrolysis passage of the fuel cell, opening the air compressor or other oxygen source and the air inlet, and switching the air outlet connection passage when the water flow of the air outlet is less than a threshold value; The purging stage: purging the oxygen side of the fuel cell, and monitoring the water content of the membrane in real time during the purging process; when the water content reaches different stages, the purging gas flow is adjusted to the optimal flow under the water content in real time; The power generation starting stage: adjusting the air compressor or other oxygen source to the power generation mode, and opening the hydrogen inlet to generate power; The purging stage first obtains the control basis for controlling the purging flow through two pre-experiments, and then changes the purging gas flow in real time according to the water content in the fuel cell: Pre-experiment one: obtaining the corresponding relationship between the high-frequency impedance value of the fuel cell and the water content in the fuel cell, taking the water content at the start of the fuel cell mode as the minimum value, the water content at the end of the electrolysis mode as the maximum value, and the mode switching being completed when the water content changes from the maximum value to the minimum value, and stopping purging; Pre-experiment two: measuring the change curve of the water content in the fuel cell under different purging gas flows in the form of purging with a constant flow and pressure; During the purging process, the water content of the membrane is monitored by monitoring the high-frequency impedance of the fuel cell; when the water content reaches different stages, the optimal gas flow is calculated according to the data of pre-experiment two, taking the purging speed, gas consumption and purging safety as the comprehensive standard, so as to change the purging gas flow in real time, and obtain the optimal flow control strategy of the purging process; The purging speed represents the speed of the water content decreasing from the initial value to the final value, which is the slope of the water content-time curve; The purge safety criterion is that the purge flow does not exceed a safety value, a safe The calculation method is: a safe = a 0.5 *k*p wherein a 0.5 is 0.5 A / cm 2 air flow rate on the oxygen side at a current density of k is a proportional coefficient, which is different for different stacks and is valued at 2.5-4; p is the water content percentage, valued at 0-1, 1 for the stack full of water and 0 for the completely dry stack; Under the condition that the purging flow does not exceed the safety value, the membrane electrode is not damaged after purging is completed, and the battery performance is not reduced after being converted to the power generation mode; The specific evaluation method of the comprehensive standard is as follows: For different water contents, the actual purging flow does not exceed the safety value under the water content, and the purging speed and gas consumption are evaluated with different proportions, the purging speed evaluation proportion is much higher than the gas consumption proportion, and the comprehensive score Score formula is as follows: Score = m*P speed + n*P consumption wherein P speed is the purge speed score, with the fastest purge speed within the safety value range corresponding to 100 points; P consumption For gas consumption score, the minimum gas consumption in the safe value range corresponds to 100 points of purge flow. m is the evaluation proportion of the purging speed; n is the evaluation proportion of the gas consumption, and m+n=1; The purging speed evaluation proportion is much higher than the gas consumption proportion, the comprehensive evaluation score of different purging gas flows under the water content is obtained, and the purging gas flow value with the highest score is selected as the optimal purging flow under the water content.

2. The integrated reversible fuel cell mode switching control method according to claim 1, characterized by, The threshold value of the water flow of the air outlet in the electrolysis stopping stage is 1 ml / s.

3. The integrated reversible fuel cell mode switching control method according to claim 1, characterized by, Pre-experiment 1: at the end of electrolysis, the air flow rate on the oxygen side was purged at 0.1 A / cm 2 Pre-experiment 1: at the end of electrolysis, the air flow rate on the oxygen side was purged at 0.1 A / cm 2 Pre-experiment 1: at the end of electrolysis, the air flow rate on the oxygen side was purged at 0.1 A / cm 2 Pre-experiment 1: at the end of electrolysis, the air flow rate on the oxygen side was purged at 0.1 A / cm 2 Pre-experiment 1: at the end of electrolysis, the air flow rate on the oxygen side was purged at 0.1 A / cm 2 Pre-experiment 1: at the end of electrolysis, the air flow rate on the oxygen side was purged at 0.1 A / cm 2 Pre-experiment 1: at the end of electrolysis, the air flow rate on the oxygen side was purged at 4. The integrated reversible fuel cell mode switching control method according to claim 1, characterized by, The gas flow value of the pre-experiment two is the air flow of the oxygen side under different current densities with a back pressure of 0 kPa, and the current density value range is 0.2 A / cm 2 3 A / cm 2 , every 0.1 A / cm 2 Take a value.

5. The integrated reversible fuel cell mode switching control method according to claim 1, characterized by, After the purging stage, the power generation stage begins. The hydrogen source and the hydrogen inlet and outlet switches are opened, the air compressor or other oxygen source is adjusted to the power generation mode, and the standard air intake of 0.5 A / cm 2 is ventilated. The voltage of each battery is monitored, and if the voltage of any battery is not lower than the warning value of 0.4 V within 20 s, it is considered that the battery can normally perform the power generation mode. If the voltage of a battery is lower than the warning value, the hydrogen source and the hydrogen inlet and outlet are closed, and the constant-pressure and constant-flow purging is continued. The purging flow is the safety value under the water content.

6. An integrated reversible fuel cell mode switching control system implementing the method of claim 1, characterized by The method comprises a stack (6), a hydrogen source, an air source, a hydrogen storage device, a high-frequency impedance measuring instrument (5), a cooling water tank (13) and an electrolysis water tank (14); Among them, The electrolysis water tank (14) is connected with the stack (6) through an electrolysis water inlet and outlet pipeline, and electrolysis water inlet and outlet switch valves (1) and (2) are respectively arranged on the electrolysis water inlet and outlet pipeline. The cooling water tank (13) is connected with the electric pile (6) through a cooling water inlet and outlet pipeline, and a cooling water inlet switch (3) and a cooling water outlet switch (4) are respectively arranged on the cooling water inlet and outlet pipeline; A hydrogen inlet switch (10) is arranged on the connecting pipeline between the hydrogen source and the electric pile (6), and an air inlet switch (7) is arranged on the connecting pipeline between the air source and the electric pile (6); and the high-frequency impedance measuring instrument (5) is connected with the electric pile (6); The air outlet of the electric pile (6) has two passages, passage one is connected to the electrolytic water tank (14), and an air outlet first switch (8) is arranged on the passage one; and passage two is connected to the atmospheric environment, and an air outlet second switch (9) is arranged on the passage two.

7. The integrated reversible fuel cell mode switching control system of claim 6, wherein, The electric pile (6) is provided with end plates adapted to the mode switching strategy at two ends, and there are a total of 8 inlets and outlets on the surface of the end plates; the inlets and outlets on the end plates and the battery pile core jointly constitute a flow circulation loop, including a cooling water circuit, a hydrogen circuit, an air circuit and an electrolytic water circuit, and the electrolytic water circuit and the air circuit are connected through the polar plate in the electric pile; and the cooling water circuit and the hydrogen circuit are completely independent passages.

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