Electricity-hydrogen-electricity coupled energy conversion system and application method thereof

Abstract

The invention belongs to the technical field of power system dispatching automation, and provides an electricity-hydrogen-electricity coupled energy conversion system and an application method thereof. According to the'electricity-hydrogen-electricity 'coupled energy conversion system disclosed by the invention, the pressure of oxygen is used as the air inlet pressure of the cathode of the fuel cell stack, so that the air inlet pressure of the cathode of the fuel cell stack does not need to be provided by an air compressor through compressed air; and air intake can be replaced by a common blower device, so that the energy consumption of an auxiliary system is greatly reduced. Therefore, oxygen-enriched air is obtained by mixing air and oxygen, the electric efficiency of the hydrogen fuel cell stack is improved, more importantly, the use of an air compressor is abandoned, the energy consumption of an auxiliary system is reduced, and finally the overall efficiency of an electricity-hydrogen-electricity coupled energy conversion system is improved. Compared with a traditional'electricity-hydrogen-electricity 'coupled energy conversion system, the'electricity-hydrogen-electricity' coupled energy conversion system has the advantage that the overall efficiency is improved by 11.36%.

Description

Technical Field

[0001] The present invention relates to the technical field of power system dispatching automation, and in particular to an "electricity-hydrogen-electricity" coupled energy conversion system and an application method thereof. Background Art

[0002] Renewable energy sources such as wind power and photovoltaic power are highly volatile and intermittent, and their power generation is difficult to match with electricity demand in real time, and it is often the case that power generation is greater than or less than electricity consumption. When the power generation of renewable energy exceeds the electricity demand, hydrogen energy storage technology can produce hydrogen through water electrolysis, converting excess electricity into hydrogen and storing it. When the power generation of renewable energy is not enough to meet the electricity demand, fuel cell power generation technology can convert the stored hydrogen into electricity, supply power to the power grid, and make up for the energy gap. However, the overall efficiency of the current "electricity-hydrogen-electricity" coupled energy conversion system is relatively low. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide an "electricity-hydrogen-electricity" coupled energy conversion system and its application method. The "electricity-hydrogen-electricity" coupled energy conversion system provided by the present invention has low energy consumption, improves the "hydrogen-electricity" energy conversion efficiency of the hydrogen fuel cell stack, and ultimately improves the overall efficiency of the "electricity-hydrogen-electricity" coupled energy conversion system.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides an "electricity-hydrogen-electricity" coupled energy conversion system, including an electrolyzer and a fuel cell stack; The direct current outputted by renewable energy is connected to the electrolyzer; the electrolyzer is a high-pressure electrolyzer, and the high-pressure electrolyzer uses electrolysis technology to generate high-pressure hydrogen and high-pressure oxygen; The oxygen generated by the electrolyzer is transported to the cathode of the fuel cell stack through an oxygen gas path; the pressure of the oxygen generated by the electrolyzer is used to provide an intake pressure for the cathode of the fuel cell stack; The hydrogen generated by the electrolyzer is transported to the anode of the fuel cell stack through a hydrogen gas path; Along the oxygen delivery direction, an oxygen constant pressure buffer tank, a pressure control component and a gas mixing device are sequentially arranged on the oxygen gas path; The oxygen constant pressure buffer tank comprises an intelligent pressure relief valve, which receives the anode outlet pressure signal feedback of the electrolyzer, and when the pressure of the oxygen constant pressure buffer tank is higher than the anode outlet pressure of the electrolyzer, the pressure is relieved, and when it is lower than the anode outlet pressure of the electrolyzer, the pressure is closed; The gas mixing device comprises two gas inlets and one gas outlet, one gas inlet of the gas mixing device is communicated with the gas outlet of the pressure control component, and the other gas inlet of the gas mixing device is communicated with the blowing device.

[0005] Preferably, the oxygen constant-pressure buffer cell comprises a gas inlet and a gas outlet; the gas inlet of the oxygen constant-pressure buffer cell is connected to the anode outlet of the electrolyzer, and the gas outlet of the oxygen constant-pressure buffer cell is connected to the gas inlet of the pressure control assembly.

[0006] Preferably, the intelligent pressure relief valve is used to maintain the pressure of the oxygen constant pressure buffer tank consistent with the anode outlet pressure of the electrolyzer.

[0007] Preferably, the pressure control component receives the inlet pressure signal feedback of the fuel cell stack, reduces the outlet pressure of the oxygen constant pressure buffer tank, and controls the inlet pressure of the fuel cell stack to be a set value.

[0008] Preferably, the blowing device is an air blower.

[0009] Preferably, a first humidifier is provided between the gas mixing device and the fuel cell stack.

[0010] Preferably, a hydrogen storage tank is provided on the hydrogen gas path.

[0011] Preferably, a second humidifier is provided between the hydrogen storage tank and the fuel cell stack.

[0012] Preferably, the fuel cell stack is also connected to a power consumption terminal.

[0013] The present invention also provides an application method of the "electricity-hydrogen-electricity" coupled energy conversion system described in the above technical solution, comprising the following steps: The electrolyzer is started, and when the oxygen produced by the electrolyzer makes the pressure of the oxygen constant pressure buffer tank consistent with the pressure of the anode outlet of the electrolyzer and remains stable, the pressure control component, the gas mixing device, the air blowing device and the fuel cell stack are turned on.

[0014] The present invention provides an "electricity-hydrogen-electricity" coupled energy conversion system.

[0015] The inventors found that in the traditional "electricity-hydrogen-electricity" coupled energy conversion system, the "electricity-hydrogen" energy conversion efficiency of water electrolysis is 60%~80%; while the "hydrogen-electricity" energy conversion efficiency of the hydrogen fuel cell stack is only 30%~45%. The hydrogen fuel cell stack is the main factor limiting the overall efficiency of the "electricity-hydrogen-electricity" coupled energy conversion system. At the same time, the inventors also found that the auxiliary system of the hydrogen fuel cell stack must have an air compressor, which maintains the fuel cell stack reaction and generates electricity by compressing the air and then passing it into the cathode of the fuel cell stack. The energy consumption of the air compressor is very large (accounting for most of the energy consumption of the auxiliary system), which makes the energy conversion efficiency of the hydrogen fuel cell stack low. Therefore, if the overall efficiency of the "electricity-hydrogen-electricity" coupled energy conversion system is to be improved, the energy consumption of the auxiliary system must be reduced on the basis of improving the electrical efficiency of the stack, and reducing the energy consumption of the auxiliary system and reducing the energy consumption of the air compressor are the key. The "electricity-hydrogen-electricity" coupled energy conversion system provided by the present invention utilizes the pressure of the oxygen generated by the electrolyzer as the intake pressure of the cathode of the fuel cell stack, so that there is no need for an air compressor to provide the intake pressure of the cathode of the fuel cell stack through compressed air; and then the air intake can be replaced by an ordinary blower, and the blower only needs to provide the flow rate of air, thereby greatly reducing the energy consumption of the auxiliary system. The design of the oxygen constant pressure buffer tank ensures the constant flow rate of oxygen while ensuring that no external energy consumption is introduced, so that sufficient oxygen and air are mixed to obtain oxygen-rich air and improve the electrical efficiency of the hydrogen fuel cell stack. More importantly, the present invention abandons the use of an air compressor, reduces the energy consumption of the auxiliary system, and finally improves the overall efficiency of the "electricity-hydrogen-electricity" coupled energy conversion system. The data of the embodiment show that the "electricity-hydrogen-electricity" coupled energy conversion system provided by the present invention has an overall efficiency improvement of up to 11.36% compared with the traditional "electricity-hydrogen-electricity" coupled energy conversion system.

[0016] The present invention also provides an application method of the "electricity-hydrogen-electricity" coupled energy conversion system described in the above technical solution. In principle, the anode outlet pressure of the electrolyzer and the gas pressure of the oxygen constant pressure buffer tank are higher than the inlet pressure of the fuel cell stack; therefore, when the system described in the above technical solution is started, the electrolyzer should be started first, and when the pressure in the oxygen constant pressure buffer tank is stable, the subsequent accessories should be started. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of an "electricity-hydrogen-electricity" coupled energy conversion system in a specific embodiment of the present invention; Figure 2 It is the performance curve of a single fuel cell under different oxygen concentrations; Figure 3 Schematic diagram of the traditional "electricity-hydrogen-electricity" coupled energy conversion system. DETAILED DESCRIPTION

[0018] The present invention provides an "electricity-hydrogen-electricity" coupled energy conversion system, including an electrolyzer and a fuel cell stack; The direct current outputted by renewable energy is connected to the electrolyzer; the electrolyzer is a high-pressure electrolyzer, and the high-pressure electrolyzer uses electrolysis technology to generate high-pressure hydrogen and high-pressure oxygen; The oxygen generated by the electrolyzer is transported to the cathode of the fuel cell stack through an oxygen gas path; the pressure of the oxygen generated by the electrolyzer is used to provide an intake pressure for the cathode of the fuel cell stack; The hydrogen generated by the electrolyzer is transported to the anode of the fuel cell stack through a hydrogen gas path; Along the oxygen delivery direction, an oxygen constant pressure buffer tank, a pressure control component and a gas mixing device are sequentially arranged on the oxygen gas path; The oxygen constant pressure buffer tank comprises an intelligent pressure relief valve, which receives the anode outlet pressure signal feedback of the electrolyzer, and when the pressure of the oxygen constant pressure buffer tank is higher than the anode outlet pressure of the electrolyzer, the pressure is relieved, and when it is lower than the anode outlet pressure of the electrolyzer, the pressure is closed; The gas mixing device comprises two gas inlets and one gas outlet, one gas inlet of the gas mixing device is communicated with the gas outlet of the pressure control component, and the other gas inlet of the gas mixing device is communicated with the blowing device.

[0019] The "electricity-hydrogen-electricity" coupled energy conversion system provided by the present invention includes an electrolyzer, and the direct current output of renewable energy is connected to the electrolyzer; the electrolyzer is a high-pressure electrolyzer, and the high-pressure electrolyzer uses electrolysis technology to produce high-pressure hydrogen and high-pressure oxygen. In the present invention, the anode of the electrolyzer preferably produces high-pressure oxygen, and the oxygen produced by the electrolyzer has its own pressure; the cathode of the electrolyzer preferably produces high-pressure hydrogen, and the hydrogen produced by the electrolyzer has its own pressure.

[0020] In the present invention, the oxygen generated by the electrolyzer is transported to the cathode of the fuel cell stack through the oxygen gas path. In the present invention, along the oxygen transport direction, the oxygen constant pressure buffer tank, the pressure control component and the gas mixing device are sequentially arranged on the oxygen gas path.

[0021] In the present invention, the oxygen constant-pressure buffer cell includes an intelligent pressure relief valve, which receives the anode outlet pressure signal feedback of the electrolyzer. When the pressure of the oxygen constant-pressure buffer cell is higher than the anode outlet pressure of the electrolyzer, the pressure is overflowed, and when it is lower, the pressure is closed. In the present invention, the intelligent pressure relief valve is used to maintain the pressure of the oxygen constant-pressure buffer cell consistent with the anode outlet pressure of the electrolyzer. In the present invention, the oxygen constant-pressure buffer cell preferably includes a gas inlet and a gas outlet; the gas inlet of the oxygen constant-pressure buffer cell is connected to the anode outlet of the electrolyzer, and the gas outlet of the oxygen constant-pressure buffer cell is connected to the gas inlet of the pressure control component. In the present invention, the oxygen constant-pressure buffer cell can form an oxygen buffer zone on the oxygen pipeline, play a role in stabilizing pressure and flow, and avoid the gas pressure at the front end of the pressure control component suddenly dropping to below the required pressure of the fuel cell inlet when the oxygen flow demand at the rear end increases.

[0022] In the present invention, the oxygen constant pressure buffer tank is used to collect oxygen to ensure the constant oxygen flow rate at the rear end.

[0023] In the present invention, the pressure control component receives the inlet pressure signal feedback of the fuel cell stack, reduces the outlet pressure of the oxygen constant pressure buffer tank, and controls the inlet pressure of the fuel cell stack to a set value. In the present invention, the pressure control component can control the delivery pressure of oxygen to stabilize the inlet pressure of the fuel cell stack. In the present invention, the pressure control component can realize the pressure-controlled delivery of oxygen.

[0024] In the present invention, the gas mixing device includes two gas inlets and one gas outlet, one gas inlet of the gas mixing device is connected to the gas outlet of the pressure control assembly, and the other gas inlet of the gas mixing device is connected to the air blowing device, and the air blowing device is preferably an air blower. In the present invention, the gas mixing device can mix the oxygen and air entering from the two gas inlets to form oxygen-enriched air; the formed oxygen-enriched air is transported to the cathode of the fuel reactor through the gas outlet of the gas mixing device.

[0025] The present invention utilizes the pressure of the oxygen generated by the electrolyzer to supply the required pressure of the cathode inlet of the fuel cell stack, thus abandoning the design of using an air compressor to provide pressure by compressed air in the traditional system; and then the air intake can be replaced by an ordinary blower, and the blower only provides the flow of air, thereby greatly reducing the energy consumption of the auxiliary system. In this way, it not only achieves the mixing of air and oxygen to obtain oxygen-enriched air, but more importantly, it abandons the use of air compressors, reduces the energy consumption of auxiliary systems, improves the energy conversion efficiency of hydrogen fuel cell stacks, and ultimately improves the overall efficiency of the "electricity-hydrogen-electricity" coupled energy conversion system. In the present invention, a first humidifier is preferably arranged between the gas mixing device and the fuel reactor, and the first humidifier is used to increase the temperature and humidity of the oxygen-enriched air in the oxygen gas path.

[0026] In the present invention, the hydrogen generated by the electrolyzer is transported to the anode of the fuel cell stack through the hydrogen gas path. In the present invention, a hydrogen storage tank is preferably provided on the hydrogen gas path, and the hydrogen storage tank can store the hydrogen generated by the electrolyzer for this system or other uses. In the present invention, a second humidifier is preferably provided between the hydrogen storage tank and the fuel cell stack, and the second humidifier is used to increase the temperature and humidity of the hydrogen in the hydrogen gas path.

[0027] The "electricity-hydrogen-electricity" coupled energy conversion system provided by the present invention comprises a fuel cell stack, which generates electrical energy by using transported oxygen, air (oxygen and air form oxygen-enriched air) and hydrogen.

[0028] In the present invention, the fuel cell stack is preferably also connected to a power consumption end, and the power consumption end is preferably a power grid or an electrical appliance.

[0029] Figure 1 is a schematic diagram of an "electricity-hydrogen-electricity" coupled energy conversion system in a specific embodiment of the present invention, Figure 1 In the embodiment, the "electricity-hydrogen-electricity" coupled energy conversion system includes an electrolyzer and a fuel cell stack, and the direct current outputted by renewable energy is connected to the electrolyzer; the electrolyzer is a high-pressure electrolyzer, and the high-pressure electrolyzer uses electrolysis technology to produce high-pressure hydrogen and high-pressure oxygen; the oxygen produced by the electrolyzer is transported to the cathode of the fuel cell stack through an oxygen gas path; along the oxygen transport direction, an oxygen constant-pressure buffer tank, a pressure control component, a gas mixing device and a first humidifier are sequentially arranged on the oxygen gas path, and the gas mixing device includes two gas inlets and one gas outlet, one gas inlet of the gas mixing device is connected to the gas outlet of the pressure control component, and the other gas inlet of the gas mixing device is connected to a blower, and the gas outlet of the gas mixing device is connected to the first humidifier; the hydrogen produced by the electrolyzer is transported to the anode of the fuel cell stack through a hydrogen gas path; a hydrogen storage tank and a second humidifier are sequentially arranged on the hydrogen gas path. The following is combined with Figure 1The schematic diagram of the "electricity-hydrogen-electricity" coupled energy conversion system shown in the figure briefly describes its working principle: the direct current output by the renewable energy provides electric energy for the high-pressure electrolyzer, and the water in the high-pressure electrolyzer is electrolyzed into high-pressure oxygen and high-pressure hydrogen. The high-pressure oxygen generated at the anode of the electrolyzer is buffered by the oxygen constant-pressure buffer tank, and the oxygen in the oxygen constant-pressure buffer tank is pressure-controlled and transported through the pressure control component, and mixed with the air introduced by the blower fan in the mixing device to form oxygen-enriched air, which is output through the gas outlet of the mixing device, and is transported to the cathode of the fuel cell stack after being heated and humidified by the first humidifier; the high-pressure hydrogen generated at the cathode of the high-pressure electrolyzer enters the hydrogen storage tank, and the hydrogen in the hydrogen storage tank is heated and humidified by the second humidifier and transported to the anode of the fuel cell stack; the fuel cell stack generates electricity using the hydrogen at the anode and the oxygen-enriched air at the cathode, and the resulting direct current can be directly connected to electrical appliances, or it can be connected to the grid for power generation through a DC / AC system.

[0030] The present invention also provides an application method of the "electricity-hydrogen-electricity" coupled energy conversion system described in the above technical solution, comprising the following steps: The electrolyzer is started, and when the oxygen produced by the electrolyzer makes the pressure of the oxygen constant pressure buffer tank consistent with the pressure of the anode outlet of the electrolyzer and remains stable, the pressure control component, the gas mixing device, the air blowing device and the fuel cell stack are turned on.

[0031] Figure 2 The performance curve of a single fuel cell under different oxygen concentrations is shown in Figure 2. Figure 2 It can be seen that the voltage and power density change with the current density under different oxygen concentrations. The higher the oxygen concentration, the greater the voltage and power density at the same current density, which means that the battery has a higher output performance under this condition.

[0032] Based on the experimental results under different oxygen concentrations, the performance of the same membrane electrode under different oxygen concentration conditions was obtained. The voltage corresponding to the current density of 1A / cm² was selected to characterize the performance of the membrane electrode. The results showed that the higher the oxygen concentration, the better the performance of the membrane electrode.

[0033] In addition, according to the fuel cell stack efficiency calculation formula provided in the national standard GB / T 24554-2022 "Fuel Cell Engine Performance Test Method", the fuel cell stack efficiency in the "electricity-hydrogen-electricity" coupled energy conversion system provided by the present invention is calculated at different oxygen enrichment concentrations, and the results are shown in Table 1. The fuel cell stack efficiency calculation formula is as follows: Traditional "electricity-hydrogen-electricity" coupled energy conversion system ( Figure 3 The overall efficiency difference between the energy conversion system of the "electricity-hydrogen-electricity" coupling provided by the present invention and the energy conversion system of the "electricity-hydrogen-electricity" coupling provided by the present invention is calculated as follows: According to the calculation formula of the air compressor provided in the article (https: / / doi.org / 10.1016 / j.fuel.2024.133495), it is as follows: in, P CP is the power consumption of the air compressor, W; τ cp is the compressor load torque; ω cp is the compressor rotation angular frequency, rad / s; V cp is the rotation speed, rpm; C p is the specific heat capacity of air (J / (kg·K)); γ is the specific heat ratio of air, unitless; p sm and p atm are the supply manifold and atmospheric pressure (Pa), respectively; T atm is the atmospheric temperature (K); W cp is the mass flow rate, kg / s.

[0034] Under oxygen-rich conditions, when the cathode flow is fixed at 3SLPM, if an air compressor is used, while maintaining a constant pressure ratio between the air compressor outlet and inlet, as the oxygen concentration in the oxygen-rich air increases, the flow rate of the air output by the air compressor will continue to decrease. According to the calculation formula of the above air compressor, the air compressor is proportional to the air flow rate, and the air compressor loss and the overall efficiency of the system can be calculated. When pure oxygen is input to the cathode, the air compressor non-operating loss is 0.

[0035] In addition, if the pressure at the outlet of the air compressor is close to the atmospheric pressure at the inlet, that is, it does not compress but only provides gas flow, then the power loss of the air compressor can be ignored. Therefore, an ordinary blower can be used to replace the air compressor, so that it only provides air flow, freeing up the energy consumption caused by the air compressor, greatly reducing the loss of the auxiliary system, and thus improving the overall efficiency of the "electricity-hydrogen-electricity" coupled energy conversion system.

[0036] According to the literature (Wang Feijie. Research on efficiency matching design of fuel cell power station [J]. Electrical Application, 2024, 43(05): 65-73.), the loss of the auxiliary system is assumed to be 10%, and the air compressor is considered to account for the main loss of the auxiliary system, assuming that it accounts for 8%. The efficiency calculation formula of the system in the national standard GB / T 24554-2022 "Fuel Cell Engine Performance Test Method" is used to calculate the efficiency of the traditional and the present application system. The efficiency calculation formula of the system is as follows: Among them, P F is the fuel cell engine power, kW; P Sis the fuel cell stack power, kW; P A is the auxiliary system power, kW; η F is the fuel cell engine efficiency; m H2 is the hydrogen flow rate, in grams per second, g / s; LHV H2 , low calorific value of hydrogen, 1.2×10 5 kJ / kg.

[0037] Will be at 1A / cm 2 The system efficiencies of the conventional and the present invention-provided "electricity-hydrogen-electricity" coupled energy conversion systems during operation are summarized in Table 1.

[0038] Table 1 System efficiency at different oxygen enrichment concentrations

[0039] It can be seen from Table 1 that according to the data in the literature (Wang Feijie. Research on efficiency matching design of fuel cell power station [J]. Electrical Application, 2024, 43(05): 65-73.), assuming that the hydrogen utilization rate is 98%, a conclusion can be drawn: when the oxygen concentration increases from 21% to 100%, the maximum efficiency of the fuel cell stack is increased by 3.36%. Compared with the "electric-hydrogen-electric" coupled energy conversion system with an air compressor, the efficiency of the "electric-hydrogen-electric" coupled energy conversion system without an air compressor of the present invention is higher at different oxygen concentrations (the consistency at 100% oxygen concentration is because the air compressor is not working at this time). In addition, compared with the traditional "electric-hydrogen-electric" coupled energy conversion system (with an air compressor, the cathode input is air), the overall efficiency of the "electric-hydrogen-electric" coupled energy conversion system without an air compressor of the present invention is increased by up to 11.36%.

[0040] Comparative Example 1 The difference from Example 1 is that the air blower is replaced by an air compressor, and the pressure control component and the oxygen constant pressure buffer tank are removed.

[0041] Compared with comparative example 1, the present invention mainly utilizes the pressure of the oxygen generated in the electrolyzer to meet the pressure required by the cathode air inlet of the fuel cell stack, and uses an ordinary air blower to replace the air compressor, which is only used as a unit to provide air flow, and no longer uses the air compressor to meet the pressure required by the cathode air inlet of the fuel cell stack, thereby greatly reducing the auxiliary system (BOP) loss and improving the overall efficiency. In addition, in order to ensure the normal operation of the above design, an oxygen constant pressure buffer tank is also added to ensure sufficient oxygen flow supply. The high-pressure oxygen generated by the anode of the high-pressure electrolyzer naturally flows into the oxygen constant pressure buffer tank without being compressed by the compressor, so the system does not introduce additional energy consumption. The pressure of the oxygen constant pressure buffer tank is equal to the anode outlet pressure of the high-pressure electrolyzer, and the oxygen overflows through the pressure relief valve to maintain the constant pressure of the oxygen constant pressure buffer tank, avoiding the operation of the high-pressure electrolyzer due to excessive pressure. In principle, the gas pressure of the anode of the electrolyzer and the oxygen constant pressure buffer tank is higher than the inlet pressure of the fuel cell stack; when the system is started, the electrolyzer should be started first, and when the pressure in the oxygen constant pressure buffer tank is stable, the other accessories behind should be started.

[0042] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An "electricity-hydrogen-electricity" coupled energy conversion system, characterized in that: including electrolyzers and fuel cell stacks; The direct current outputted by renewable energy is connected to the electrolyzer; the electrolyzer is a high-pressure electrolyzer, and the high-pressure electrolyzer uses electrolysis technology to generate high-pressure hydrogen and high-pressure oxygen; The oxygen generated by the electrolyzer is transported to the cathode of the fuel cell stack through an oxygen gas path; the pressure of the oxygen generated by the electrolyzer is used to provide an intake pressure for the cathode of the fuel cell stack; The hydrogen generated by the electrolyzer is transported to the anode of the fuel cell stack through a hydrogen gas path; Along the oxygen delivery direction, an oxygen constant pressure buffer tank, a pressure control component and a gas mixing device are sequentially arranged on the oxygen gas path; The oxygen constant pressure buffer tank comprises an intelligent pressure relief valve, which receives the anode outlet pressure signal feedback of the electrolyzer, and when the pressure of the oxygen constant pressure buffer tank is higher than the anode outlet pressure of the electrolyzer, the pressure is relieved, and when it is lower than the anode outlet pressure of the electrolyzer, the pressure is closed; The gas mixing device comprises two gas inlets and one gas outlet, one gas inlet of the gas mixing device is communicated with the gas outlet of the pressure control component, and the other gas inlet of the gas mixing device is communicated with the blowing device.

2. The "electricity-hydrogen-electricity" coupled energy conversion system according to claim 1 is characterized in that: The oxygen constant pressure buffer cell comprises a gas inlet and a gas outlet; the gas inlet of the oxygen constant pressure buffer cell is connected to the anode outlet of the electrolyzer, and the gas outlet of the oxygen constant pressure buffer cell is connected to the gas inlet of the pressure control component.

3. The "electricity-hydrogen-electricity" coupled energy conversion system according to claim 1 is characterized in that: The intelligent pressure relief valve is used to maintain the pressure of the oxygen constant pressure buffer tank consistent with the anode outlet pressure of the electrolyzer.

4. The "electricity-hydrogen-electricity" coupled energy conversion system according to claim 1 is characterized in that: The pressure control component receives the inlet pressure signal feedback of the fuel cell stack, reduces the outlet pressure of the oxygen constant pressure buffer tank, and controls the inlet pressure of the fuel cell stack to be a set value.

5. The "electricity-hydrogen-electricity" coupled energy conversion system according to claim 1 is characterized in that: The blowing device is an air blower.

6. The "electricity-hydrogen-electricity" coupled energy conversion system according to claim 1 is characterized in that: A first humidifier is arranged between the gas mixing device and the fuel cell stack.

7. The "electricity-hydrogen-electricity" coupled energy conversion system according to claim 1 is characterized in that: A hydrogen storage tank is arranged on the hydrogen gas path.

8. The "electricity-hydrogen-electricity" coupled energy conversion system according to claim 7 is characterized in that: A second humidifier is arranged between the hydrogen storage tank and the fuel cell stack.

9. The "electricity-hydrogen-electricity" coupled energy conversion system according to claim 1 is characterized in that: The fuel cell stack is also connected to a power consumption terminal.

10. The application method of the "electricity-hydrogen-electricity" coupled energy conversion system according to any one of claims 1 to 9, characterized in that: The following steps are involved: The electrolyzer is started, and when the oxygen produced by the electrolyzer makes the pressure of the oxygen constant pressure buffer tank consistent with the pressure of the anode outlet of the electrolyzer and remains stable, the pressure control component, the gas mixing device, the air blowing device and the fuel cell stack are turned on.

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