Hydrogen circulation amount control system and method in fuel cell system

Abstract

The application discloses a hydrogen circulation amount control system and method in a fuel cell system, wherein the hydrogen circulation amount control system in the fuel cell system comprises a fuel cell stack, a hydrogen jet ejector, a water distributor and a hydrogen circulation pump. The outlet of the hydrogen jet ejector is connected with the outlet of a cooling liquid cavity of the fuel cell stack through a first pipeline. The outlet of the water distributor is connected with the backflow port of the hydrogen jet ejector through a second pipeline, and the inlet of the water distributor is connected with the outlet of an anode cavity of the fuel cell stack through a third pipeline. The outlet of the hydrogen circulation pump is connected with the inlet of the anode cavity of the fuel cell stack through a fourth pipeline, and the inlet of the hydrogen circulation pump is connected with the outlet of the water distributor through a fifth pipeline. Therefore, the hydrogen circulation amount control system in the fuel cell system of the application increases the internal water management stability of the fuel cell stack, improves the service life and reliability of the fuel cell system, and reduces the overall cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermal management of fuel cell systems for vehicles, and in particular to a hydrogen circulation amount control system and method in a fuel cell system. BACKGROUND

[0002] A fuel cell system is a power system for a new energy vehicle, which uses hydrogen as fuel and air as oxidant to generate electric power. The fuel cell system includes core components (fuel cell stack), electrical auxiliary components (air compressor, humidifier, sensor, valve components, DCDC, etc.), thermal management system components (anode heat exchanger, intercooler, thermostat, radiator, etc.), connecting pipe joints, mechanical structures, etc.

[0003] The fuel cell stack, the most core component in the fuel cell system, is an electrochemical device that generates electric power through electrochemical reactions of hydrogen and air. Unlike traditional internal combustion engines, the fuel cell stack generates electric power through electrochemical reactions and only emits water. The fuel cell stack is composed of a plurality of fuel cell monomers stacked together, each of which is composed of a membrane electrode, a bipolar plate, and a sealing material. The membrane electrode is the site of electrochemical reactions, which includes a proton exchange membrane, a catalyst (cathode and anode), and a gas diffusion layer. The anode of the membrane electrode undergoes hydrogen oxidation, and the cathode undergoes air reduction. To ensure the normal progress of the electrochemical reactions in the fuel cell stack, the water-heat balance inside the membrane electrode needs to be maintained. In particular, water balance is particularly important for the discharge performance of the fuel cell stack. Fuel cell water balance refers to maintaining the water content of the proton exchange membrane, catalyst layer, and gas diffusion layer in the membrane electrode at an appropriate level. The proton exchange membrane needs to have a certain water content to ensure the conductivity of protons in the proton exchange membrane; otherwise, the proton exchange membrane will shrink and crack due to dehydration, causing damage to the fuel cell stack. At the same time, the water content cannot be too high, as excessive water content in the membrane electrode can cause waterlogging of the catalyst layer. Water blocks the gas passage in the gas diffusion layer, preventing the reaction gas oxygen or hydrogen from reaching the catalyst layer, which prevents the electrochemical reaction from proceeding normally and greatly reduces the performance of the fuel cell.

[0004] To maintain the water balance of the membrane electrode in the fuel cell stack, the hydrogen subsystem of the fuel cell system usually introduces a hydrogen circulation system to circulate the gas and water after the reaction in the fuel cell stack back to the inlet of the fuel cell stack to maintain the anode water balance in the membrane electrode of the fuel cell. When the fuel cell system is at low current, less water is generated, so a higher circulation rate is needed; when the fuel cell system is at high current, more water is generated, so a lower circulation rate is needed or the water in the circulating gas is separated and removed by a water separator to prevent waterlogging.

[0005] As the power of fuel cell system increases, the hydrogen circulation system becomes more complex. In small power fuel cell systems, the hydrogen circulation system is usually composed of a hydrogen circulation pump or a hydrogen ejector, because the circulation flow requirement is low, and one of the two technical routes can be taken. When the power of the fuel cell system increases, the hydrogen circulation pump is not enough to support the large flow circulation, and a hydrogen ejector needs to be introduced. By connecting the hydrogen ejector and the hydrogen circulation pump in parallel or series, the circulation rate of the hydrogen circulation system can be controlled, and the water balance in the fuel cell stack can be maintained. Among them, the hydrogen circulation pump usually rotates the rotor in the Roots pump to push the gas to move to achieve circulation. The hydrogen ejector sucks the induced gas (circulating gas) through the local vacuum generated by the jet of the convergent nozzle, thereby forming the effect of circulation. The hydrogen ejector can adjust the flow of the jet by adjusting the opening of the electromagnetic valve of the ejector, thereby controlling the flow of the induced gas. Compared with the hydrogen circulation pump, the energy consumption of the hydrogen ejector is smaller.

[0006] Currently, the existing deionizer scheme in the fuel cell system thermal management subsystem is mainly as follows:

[0007] 1. The patent document with publication number CN110676484A proposes a vehicle, a hydrogen circulation system of a fuel cell, and a hydrogen circulation control method. The hydrogen circulation system includes a hydrogen cylinder, a hydrogen ejector, a gas-liquid separator provided with a first outlet and a second outlet, a hydrogen circulation pump, an electromagnetic valve, etc. According to the current change of the fuel cell, the inlet pressure of the hydrogen ejector, the rotation speed of the hydrogen circulation pump, the opening frequency of the drain electromagnetic valve, and the opening time of each time are adjusted in real time. The control basis of the hydrogen circulation system of this scheme is the current of the fuel cell. This scheme does not use a feedback control strategy, and the control is relatively simple, with poor adaptability. In addition, the fuel cell stack is a strong time-varying controlled object, and this scheme cannot accurately control the hydrogen circulation amount of the fuel cell system in the whole life cycle.

[0008] 2. The patent document with publication number CN114665129A proposes a hydrogen ejector control method and device for low-temperature cold start of a fuel cell. The scheme is to arrange a hydrogen pressure sensor on the inner wall of the output pipe of the hydrogen ejector. By acquiring the pressure data collected by the hydrogen pressure sensor, it is determined whether the hydrogen pressure sensor is normal, and whether the ice removal repair operation of the hydrogen pressure sensor is performed. This scheme solves the influence of water icing in the hydrogen circulation of the fuel cell system on the water balance, but does not clearly control the hydrogen circulation amount in the hydrogen subsystem.

[0009] 3、Patent literature with publication number CN112803045A proposes a hydrogen system control method, device and equipment for a fuel cell, the specific control method is to obtain the difference value of the target stack flow and the current stack flow according to the output power, control the duty cycle of the hydrogen ejector and the decoupling speed of the hydrogen circulation pump; through the difference value of the target stack pressure and the current stack pressure, control the speed of the hydrogen circulation pump, the duty cycle of the hydrogen ejector. This scheme optimizes the static response and dynamic response effect of the hydrogen control system, but introduces a complex algorithm, which reduces the robustness of the control and the difficulty of calibration.

[0010] 4、Patent literature with publication number CN109830709A proposes a fuel cell hydrogen supply control method, which controls the opening time of the hydrogen injection device by combining the feedforward value of compensating the pressure influence of the circulation pump, the feedforward value of compensating the pressure influence of the electrochemical reaction of the stack, the feedforward value of compensating the pressure influence of the tail exhaust valve, and the feedback value of the duty cycle, to optimize the anode pressure of the fuel cell stack. This scheme emphasizes the control of the anode pressure of the fuel cell stack, but the control of the circulation flow is not optimized.

[0011] 5、Patent literature with publication number CN113540506A proposes a water management control method, the main control method is to calculate the net water content and water content change value of the fuel cell stack by using the current of the fuel cell system and the temperature, pressure and humidity data of the inlet and outlet of the fuel cell system, compare the calculation result with the target water content of the fuel cell stack under the current, and adjust the hydrogen circulation system according to the difference. This scheme uses the method of calculating the water content, and controls by comparing the difference between the water content and the target value, but this scheme needs to install temperature and humidity sensors, which increases the cost of fuel cell system design. In addition, the water content is calculated by using the apparent temperature, pressure and humidity data of the inlet and outlet of the fuel cell system, which has the risk of inaccuracy, reducing the robustness of the control system.

[0012] The information disclosed in this BACKGROUND section is only intended to increase an understanding of the general context in which the present application can be practiced. It is not admitted that any of the information provided in this BACKGROUND section constitutes prior art. SUMMARY

[0013] The purpose of the present application is to provide a hydrogen circulation amount control system and method in a fuel cell system, which increases the stability of water management in the fuel cell stack, improves the service life and reliability of the fuel cell system, and reduces the overall cost.

[0014] To achieve the above object, in a first aspect, the present application provides a hydrogen circulation amount control system in a fuel cell system, comprising: a fuel cell stack, a hydrogen ejector, a water distributor, and a hydrogen circulation pump. An outlet of the hydrogen ejector is connected to an outlet of a cooling liquid chamber of the fuel cell stack through a first pipeline. An outlet of the water distributor is connected to a backflow port of the hydrogen ejector through a second pipeline, and an inlet of the water distributor is connected to an outlet of an anode chamber of the fuel cell stack through a third pipeline. An outlet of the hydrogen circulation pump is connected to an inlet of the anode chamber of the fuel cell stack through a fourth pipeline, and an inlet of the hydrogen circulation pump is connected to the outlet of the water distributor through a fifth pipeline.

[0015] In an embodiment of the present application, the hydrogen circulation amount control system in the fuel cell system further comprises a temperature sensor connected to the inlet of the anode chamber of the fuel cell stack.

[0016] In an embodiment of the present application, the hydrogen circulation amount control system in the fuel cell system further comprises a first hydrogen pressure sensor arranged on the first pipeline.

[0017] In an embodiment of the present application, the hydrogen circulation amount control system in the fuel cell system further comprises a second hydrogen pressure sensor arranged on the second pipeline.

[0018] In an embodiment of the present application, the first hydrogen pressure sensor and the second hydrogen pressure sensor are used to monitor the pressures at the outlet and the backflow port of the hydrogen ejector, respectively.

[0019] In an embodiment of the present application, the hydrogen circulation pump is used to push the inlet gas to the outlet by rotating the rotor.

[0020] In a second aspect, the present application provides a hydrogen circulation amount control method in a fuel cell system, comprising: when the fuel cell system starts to operate, reading the pressure of a first hydrogen pressure sensor, the pressure of a second hydrogen pressure sensor, the current value of the fuel cell stack, and the opening degree of the hydrogen ejector. The target pressure value of the inlet of the fuel cell stack is obtained by looking up a first preset table according to the current value. The opening degree of the hydrogen ejector is controlled by PID feedback according to the difference between the target pressure value of the inlet of the fuel cell stack and the reading of the second hydrogen pressure sensor. A control command is issued to update the opening degree instruction of the hydrogen ejector. The hydrogen circulation flow under the opening degree instruction is obtained by looking up a second preset table according to the opening degree instruction. The required hydrogen circulation flow is obtained by looking up a third preset table according to the current of the fuel cell system. The target rotating speed of the hydrogen circulation pump is obtained by looking up a fourth preset table according to the required flow of the hydrogen circulation, the pressure difference between the inlet and the outlet of the hydrogen circulation, and the target rotating speed of the hydrogen circulation pump.

[0021] Compared with the prior art, the hydrogen circulation amount control system and method in the fuel cell system according to the present application has the following beneficial effects:

[0022] 1. The hydrogen gas subsystem pressure of the fuel cell system is controlled by the hydrogen gas jet ejector opening, and the rotating speed of the hydrogen circulation pump is controlled by the pressure difference between the hydrogen gas jet ejector outlet and the backflow port, so that the circulation flow and pressure of the hydrogen gas subsystem are controlled.

[0023] 2. Compared with the prior art, the number of humidity sensors is reduced, and the system cost is reduced.

[0024] 3. The coupling control of the pressure and the flow is added, and the adaptability of the control is improved.

[0025] 4. The control strategy does not include complex calculation, and the robustness is high.

[0026] 5. The stability of the water management in the fuel cell stack is improved, and the service life and reliability of the fuel cell system are improved. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of the architecture of the hydrogen circulation amount control system in the fuel cell system according to an embodiment of the present application.

[0028] Figure 2 is a flowchart of the hydrogen circulation amount control method in the fuel cell system according to an embodiment of the present application.

[0029] MAIN REFERENCE NUMERALS EXPLANATION:

[0030] 1 - fuel cell stack, 2 - water separator, 3 - hydrogen circulation pump, 4 - hydrogen gas jet ejector, 5 - first hydrogen pressure sensor, 6 - second hydrogen pressure sensor. DETAILED DESCRIPTION

[0031] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present application is not limited by the specific embodiments.

[0032] Unless otherwise clearly indicated, in the entire specification and claims, the term "comprise" or its variants such as "contain" or "include" and the like will be understood to include the stated element or component, but not to exclude the presence of other elements or components.

[0033] Figure 1 is a schematic diagram of the architecture of the hydrogen circulation amount control system in the fuel cell system according to an embodiment of the present application. As Figure 1As shown, a hydrogen circulation amount control system in a fuel cell system according to a preferred embodiment of the present application comprises a fuel cell stack 1, a hydrogen ejector 4, a water separator 2 and a hydrogen circulation pump 3. The outlet of the hydrogen ejector 4 is connected to the outlet of the coolant cavity of the fuel cell stack 1 through a first pipe. The outlet of the water separator 2 is connected to the backflow port of the hydrogen ejector 4 through a second pipe, and the inlet of the water separator 2 is connected to the outlet of the anode cavity of the fuel cell stack 1 through a third pipe. The outlet of the hydrogen circulation pump 3 is connected to the inlet of the anode cavity of the fuel cell stack 1 through a fourth pipe, and the inlet of the hydrogen circulation pump 3 is connected to the outlet of the water separator 2 through a fifth pipe.

[0034] In an embodiment of the present application, the hydrogen circulation amount control system in a fuel cell system further comprises a temperature sensor connected to the inlet of the anode cavity of the fuel cell stack 1.

[0035] In an embodiment of the present application, the hydrogen circulation amount control system in a fuel cell system further comprises a first hydrogen pressure sensor 5 disposed on the first pipe.

[0036] In an embodiment of the present application, the hydrogen circulation amount control system in a fuel cell system further comprises a second hydrogen pressure sensor 6 disposed on the second pipe.

[0037] In an embodiment of the present application, the first hydrogen pressure sensor 5 and the second hydrogen pressure sensor 6 are used to monitor the pressure of the outlet and the backflow port of the hydrogen ejector 4 respectively.

[0038] In an embodiment of the present application, the hydrogen circulation pump 3 is used to push the inlet gas to the outlet by the rotation of the rotor.

[0039] Figure 2 is a flowchart of a hydrogen circulation amount control method in a fuel cell system according to an embodiment of the present application. As shown, Figure 2As shown, according to the hydrogen circulation amount control method of the fuel cell system according to another preferred embodiment of the present application, when the fuel cell system starts to operate, the pressure of the first hydrogen pressure sensor 5, the pressure of the second hydrogen pressure sensor 6, the current value of the fuel cell stack 1 and the opening of the hydrogen ejector 4 are read. The target pressure value of the fuel cell stack 1 inlet is obtained by looking up the first preset table through the current value. The opening of the hydrogen ejector 4 is controlled by PID feedback according to the difference between the target pressure value of the fuel cell stack 1 inlet and the reading of the second hydrogen pressure sensor 6. The control command is issued to update the opening instruction of the hydrogen ejector 4. The hydrogen circulation flow under the opening instruction is obtained by looking up the second preset table according to the opening instruction. The required hydrogen circulation flow is obtained by looking up the third preset table according to the current of the fuel cell system. The target rotating speed of the hydrogen circulation pump 3 is obtained by looking up the fourth preset table according to the required flow of the hydrogen circulation, the pressure difference between the inlet and outlet of the hydrogen circulation. The control command is issued to update the rotating speed of the hydrogen circulation pump 3.

[0040] In practical application, the hydrogen circulation amount control system of the fuel cell system according to the present application is composed of the fuel cell stack 1, the water distributor 2, the hydrogen circulation pump 3, the hydrogen ejector 4, the first hydrogen pressure sensor 5 and the second hydrogen pressure sensor 6. The main loop of the hydrogen subsystem of the fuel cell system is composed of the fuel cell stack 1, the water distributor 2, the hydrogen ejector 4, the first hydrogen pressure sensor 5 and the second hydrogen pressure sensor 6. The inlet of the anode cavity (hydrogen) of the fuel cell stack 1 is connected with the outlet of the hydrogen circulation pump 3 through the pipeline and the joint. The outlet of the cooling liquid cavity of the fuel cell stack 1 is connected with the outlet of the hydrogen ejector 4 through the pipeline and the joint. The first hydrogen pressure sensor 5 is arranged on the pipeline and the joint between the fuel cell stack 1 and the hydrogen ejector 4. The backflow port of the hydrogen ejector 4 is connected with the outlet of the water distributor 2 through the pipeline and the joint. The second hydrogen pressure sensor 6 is arranged on the pipeline and the joint between the outlet of the water distributor 2 and the backflow port of the hydrogen ejector 4. The outlet of the anode cavity of the fuel cell stack 1 is connected with the inlet of the water distributor 2 through the pipeline and the joint. The branch of the hydrogen subsystem of the fuel cell system is composed of the fuel cell stack 1, the water distributor 2 and the hydrogen circulation pump 3. The inlet of the anode cavity (hydrogen) of the fuel cell stack 1 is connected with the outlet of the hydrogen circulation pump 3 through the pipeline and the joint. The inlet of the hydrogen circulation pump 3 is connected with the outlet of the water distributor 2 through the pipeline and the joint. The inlet of the water distributor 2 is connected with the outlet of the fuel cell stack 1 through the pipeline and the joint.

[0041] In the main circuit of the hydrogen subsystem of the fuel cell system, the anode cavity of the fuel cell stack 1 is the reaction site of hydrogen, and hydrogen is consumed to generate electricity through electrochemical reaction; the water separator 2 separates liquid water in the gas from the gas through centrifugal force or blocking, etc. The hydrogen circulating pump 3 pushes the inlet gas to the outlet through the rotation of the rotor. The hydrogen injection ejector 4 has a convergent nozzle inside, and the gas injection or closing of the convergent nozzle is controlled by the opening or closing of the injection electromagnetic valve. The first hydrogen pressure sensor 5 and the second hydrogen pressure sensor 6 monitor the pressures at the outlet and the backflow port of the hydrogen injection ejector 4, respectively.

[0042] The hydrogen circulation amount control method under the double circulation of the hydrogen injection ejector 4 and the circulating pump in the fuel cell system provided by the present application starts the hydrogen circulation amount control method under the double circulation of the hydrogen injection ejector 4 and the circulating pump when the fuel cell system is in the running state. The hydrogen pressures at the outlet and the backflow port of the hydrogen injection ejector 4 are monitored by the first hydrogen pressure sensor 5 and the second hydrogen pressure sensor 6, the working current of the fuel cell stack 1 is monitored by the current sensor, and the opening signal of the ejector of the hydrogen injection ejector 4 itself is monitored. The hydrogen inlet target pressure of the fuel cell stack 1 under the current is obtained by looking up the first preset table according to the current value of the fuel cell stack 1. The difference between the hydrogen inlet target pressure and the reading of the first hydrogen sensor (i.e. the actual pressure of the hydrogen inlet) is calculated, the opening of the hydrogen injection ejector 4 is adjusted by the PID feedback control according to the difference, and the opening instruction is issued to the hydrogen injection ejector 4. The outlet flow and the injection flow of the hydrogen injection ejector 4 under the working state are obtained by looking up the second preset table according to the opening instruction of the hydrogen injection ejector 4, the flow is determined by the flow channel design of the ejector, and the second preset table is obtained by the test of the ejector in advance. The total hydrogen flow required by the fuel cell stack 1 under the current is obtained by looking up the third preset table according to the current of the fuel cell stack 1, and the difference between the total hydrogen flow and the outlet flow of the hydrogen injection ejector 4 obtained in the last link is the additional circulating flow required by the hydrogen circulating pump 3. The target rotating speed of the hydrogen circulating pump 3 is obtained by looking up the fourth preset table according to the additional circulating flow and the pressure difference between the outlet and the backflow port of the hydrogen injection ejector 4. Finally, the target rotating speed of the hydrogen circulating pump 3 is issued, and the hydrogen circulation amount control strategy under the double circulation of the hydrogen injection ejector 4 and the circulating pump is completed. Then, it returns to the starting step to start the next round of control.

[0043] Compared with the existing scheme 5, the present application does not need to integrate the high-cost humidity sensor, thereby reducing the overall cost of the fuel cell system. Compared with the existing scheme 3, the control algorithm of the present application is relatively simple, does not need to introduce complex calculation, and has strong robustness. Compared with the existing scheme 1, the rotating speed of the hydrogen circulating pump 3 and the control of the hydrogen injection ejector 4 are associated in the present application, thereby increasing the adaptability of the control.

[0044] In summary, the hydrogen circulation amount control system and method in the fuel cell system of the present application has the following advantages:

[0045] 1. The hydrogen gas subsystem pressure of the fuel cell system is controlled by the hydrogen gas injection ejector opening, and the rotating speed of the hydrogen circulation pump is controlled by the pressure difference between the hydrogen gas injection ejector outlet and the backflow port, thereby realizing the control of the circulation flow and pressure of the hydrogen gas subsystem.

[0046] 2. Compared with the prior art, the number of humidity sensors is reduced, and the system cost is lowered.

[0047] 3. The coupling control of the pressure and flow is added, and the adaptability of the control is improved.

[0048] 4. The control strategy does not include complex calculation, and the robustness is relatively high.

[0049] 5. The stability of the water management inside the fuel cell stack 1 is improved, and the service life and reliability of the fuel cell system are improved.

[0050] The foregoing description of specific exemplary embodiments of the application is intended to be illustrative only and is not intended to limit the application to the precise forms described. Many modifications and variations are possible in light of the above teachings without departing from the spirit or essential characteristics of the application. The exemplary embodiments are chosen and described in order to explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the application be defined by the claims and their equivalents.

Claims

1. A hydrogen circulation control system for a fuel cell system, characterized in that, include: Fuel cell stack; A hydrogen injection ejector, the outlet of which is connected to the inlet of the anode cavity of the fuel cell stack via a first pipeline; The water distributor has its outlet connected to the return port of the hydrogen injection ejector via a second pipeline, and its inlet connected to the anode cavity outlet of the fuel cell stack via a third pipeline. A hydrogen circulation pump, the outlet of which is connected to the inlet of the anode chamber of the fuel cell stack via a fourth pipeline, and the inlet of which is connected to the outlet of the water distributor via a fifth pipeline; A first hydrogen pressure sensor is installed on the first pipeline; A second hydrogen pressure sensor is installed on the second pipeline; The first hydrogen pressure sensor and the second hydrogen pressure sensor are used to monitor the pressure at the outlet and return port of the hydrogen jet ejector, respectively. When the fuel cell system starts running, the pressure of the first hydrogen pressure sensor, the pressure of the second hydrogen pressure sensor, the current value of the fuel cell stack, and the opening degree of the hydrogen injection ejector are read. The target pressure value at the inlet of the fuel cell stack is obtained by looking up the current value in the first preset table. The opening of the hydrogen injection ejector is controlled by PID feedback based on the difference between the target pressure value at the fuel cell stack inlet and the reading of the first hydrogen pressure sensor. Issue control commands to update the opening instructions for the hydrogen ejector; The hydrogen circulation flow rate under the opening command is obtained by looking up the second preset table according to the opening command. Based on the current of the fuel cell system, the required hydrogen circulation flow rate is obtained by referring to the third preset table. Based on the required flow rate of hydrogen circulation and the pressure difference between the inlet and outlet of hydrogen circulation, the target speed of the hydrogen circulation pump is obtained by referring to the fourth preset table. Issue a control command to update the hydrogen circulation pump speed.

2. The hydrogen circulation control system in the fuel cell system as described in claim 1, characterized in that, It also includes a temperature sensor connected to the inlet of the anode cavity of the fuel cell stack.

3. The hydrogen circulation control system in the fuel cell system as described in claim 1, characterized in that, The hydrogen circulation pump is used to push the inlet gas to the outlet by rotating the rotor.

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