Fuel cell hydrogen circulation system and control method thereof

Abstract

The invention discloses a fuel cell hydrogen circulation system and a control method thereof. The fuel cell hydrogen circulation system comprises a fuel cell stack FCS, a high-pressure hydrogen tank T, an FCU module, a first switch valve V1, a pressure reducing valve PRV, a proportional valve PCV, a three-way valve DV1, a three-way valve DV2, a circulation loop HRC, a water segregator GLS, a pressure sensor P1 and a pressure sensor P2. The circulation loop HRC comprises an ejector EJ, a hydrogen circulation pump CP, a second switch valve V2, a one-way valve CV1, a third switch valve V3 and a one-way valve CV2; the circulation loop comprises a first circulation loop, a second circulation loop, a third circulation loop and / or a fourth circulation loop. According to the invention, four hydrogen circulation modes can be switched, the optimal circulation mode is selected under different power conditions, and the on-off of a switch valve is controlled through a hierarchical control strategy to reconstruct a topological structure, so that the optimal hydrogen utilization efficiency is achieved, the full-working-condition operation requirement of the fuel cell is effectively covered, the severe fluctuation of circulation flow and anode pressure is avoided, and the service life of the fuel cell is prolonged. Therefore, stability is improved and overall efficiency of the system is improved.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and in particular relates to a fuel cell hydrogen circulation system and its control method. Background Technology

[0002] Fuel cell systems are widely used in vehicles, power plants, and distributed energy fields. Their core component, the fuel cell stack (FCS), generates electricity through an electrochemical reaction of hydrogen and air.

[0003] In existing technologies, fuel cell systems mostly employ a topology with a single hydrogen circulation mode or two hydrogen circulation modes, using a single- or dual-range power determination method. This method determines the current load state based on a fixed threshold and switches the hydrogen circulation mode accordingly. However, the dynamic response characteristics of fuel cell stacks (FCS) are complex, with a wide range of power variations. A single threshold determination method is insufficient to meet the control requirements under multiple operating conditions. Due to the lack of more refined power range division, existing topologies and control strategies have room for optimization in terms of hydrogen circulation efficiency, energy consumption, and stack response speed under partial load conditions.

[0004] If a topology with a single hydrogen circulation mode is adopted, the ejector's ejection capacity is insufficient under low power conditions, and the hydrogen circulation pump consumes more power under high power conditions. When external conditions change, the single circulation mode cannot adjust the circulation flow in time, which can easily lead to excessive hydrogen emission or local hydrogen shortage. If a topology with two hydrogen circulation modes is adopted, the operating conditions are quite different when switching between the two circulation modes, which can easily cause fluctuations and present certain optimization bottlenecks. Furthermore, it is difficult to cover the optimal circulation mode for each power range.

[0005] Furthermore, during dynamic power increases and decreases, the power output of a fuel cell stack (FCS) experiences frequent small fluctuations. Directly employing a single threshold switching control mode can easily lead to frequent changes in air compressor speed, circulating pump status, or ejector opening, resulting in system oscillations, decreased control stability, and shortened component lifespan. Therefore, how to achieve more refined interval division based on the stack's power characteristics and incorporate hysteresis mechanisms to avoid frequent switching remains a key technical challenge in fuel cell system control. Summary of the Invention

[0006] To address the aforementioned issues, this invention proposes a fuel cell hydrogen circulation system and its control method. By altering the topology of the fuel cell hydrogen circulation system under different power conditions, four hydrogen circulation modes can be switched: single hydrogen circulation pump mode, hydrogen circulation pump and ejector series mode, single ejector mode, and hydrogen circulation pump and ejector parallel mode. This optimizes the hydrogen circulation mode across the entire operating range and effectively improves the hydrogen utilization rate of the fuel cell.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a fuel cell hydrogen circulation system, comprising: a fuel cell stack FCS, a high-pressure hydrogen tank T, an FCU module, a first switching valve V1, a pressure reducing valve PRV, a proportional valve PCV, a three-way valve DV1, a three-way valve DV2, a circulation loop HRC, a water distributor GLS, a pressure sensor P1, and a pressure sensor P2. The circulation loop HRC includes an ejector EJ, a hydrogen circulation pump CP, a second switching valve V2, a one-way valve CV1, a third switching valve V3, and a one-way valve CV2. The water distributor GLS is integrated with a drain valve LD and an air vent valve PV. One end of the first switching valve V1 is connected to the high-pressure hydrogen tank T, and the other end is connected to the inlet of the pressure reducing valve PRV. The outlet of the pressure reducing valve PRV is connected to the inlet of the proportional valve PCV. The inlet of the three-way valve DV1 is connected to the outlet of the proportional valve PCV, and the outlet is connected via pipelines to the anode inlet of the fuel cell stack FCS and the inlet of the ejector EJ, respectively. The circulation loop HRC is in closed-loop fluid communication with the anode of the fuel cell stack FCS. The inlet of the water distributor GLS is connected to the anode outlet of the fuel cell stack. The outlet of the water distributor GLS is connected to the drain valve LD, the vent valve PV, and the three-way valve DV2, respectively; the inlet of the three-way valve DV2 is connected to the outlet of the water distributor GLS, and the outlet of the three-way valve DV2 is connected to the one-way valve CV2 and the one-way valve CV1, respectively; the other end of the one-way valve CV1 is connected to the hydrogen circulation pump CP; the other end of the one-way valve CV2 is connected to the ejector port of the ejector EJ; the pressure sensor P1 and the pressure sensor P2 are respectively installed at the inlet and outlet of the fuel cell stack FCS to detect the pressure value in real time. The circulation loop forms different states of circulation loops based on the adjustment of three-way valve DV1, three-way valve DV2, second switching valve V2 and / or third switching valve V3, including a first circulation loop, a second circulation loop, a third circulation loop and / or a fourth circulation loop.

[0008] Furthermore, the first circulation loop is sequentially equipped with a one-way valve CV1, a hydrogen circulation pump CP, and a second switching valve V2 along the hydrogen flow direction to realize a single hydrogen circulation pump mode.

[0009] Furthermore, the second circulation loop is sequentially equipped with a one-way valve CV1, a hydrogen circulation pump CP, a third switching valve V3, and an ejector EJ along the hydrogen flow direction, realizing a series connection mode between the hydrogen circulation pump and the ejector.

[0010] Furthermore, the third circulation loop is equipped with a one-way valve CV2 and an ejector EJ in sequence along the hydrogen flow direction to achieve a single ejector mode.

[0011] Furthermore, the fourth circulation loop includes a first circulation loop and a third circulation loop connected in parallel. The two loops form independent hydrogen channels and together constitute a composite circulation path for supplying hydrogen to the fuel cell stack (FCS) in a parallel structure. The fourth circulation loop is provided with the first circulation loop including a one-way valve CV1, a hydrogen circulation pump CP, and a second switching valve V2, and the third circulation loop including a one-way valve CV2 and an ejector EJ, in sequence along the hydrogen flow direction, realizing the parallel connection mode of the hydrogen circulation pump and the ejector.

[0012] Furthermore, the FCU module is used to control the on / off state of the switching valve and the opening frequency and duration of the drain valve LD and the exhaust valve PV based on the output power of the fuel cell.

[0013] On the other hand, the present invention also provides a control method for a fuel cell hydrogen circulation system, applied to the aforementioned fuel cell hydrogen circulation system, comprising the following steps: (1) Obtain the operating status of the fuel cell stack FCS; (2) Based on the output power of the fuel cell stack FCS, the circulation mode is automatically switched, that is, when the power reaches a certain range, the on / off state of each switch valve of the fuel cell hydrogen circulation system is controlled to switch to the corresponding circulation mode. (3) A hierarchical structure is adopted, and the system is efficiently and stably controlled through the upper-level decision-making and lower-level execution architecture. The upper-level decision-making module constructs a fuzzy rule base based on the real-time monitored key parameters of fuel cell stack FCS output power, anode inlet and outlet pressure, hydrogen flow rate and parasitic power consumption to realize the identification of operating conditions and adaptive selection of cycle schemes. The lower-level execution module designs controllers for different cycle schemes.

[0014] Furthermore, when the fuel cell stack FCS is operating at low power, the hydrogen circulation pump CP supplies hydrogen to the fuel cell stack FCS through the first circulation loop; the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell stack FCS. When the fuel cell stack FCS is operating at low power, the hydrogen circulation pump CP and the ejector EJ work in series. The hydrogen circulation pump CP delivers circulating hydrogen to the fuel cell stack FCS via the second circulation loop. The ejector EJ uses high-pressure hydrogen supply to form a negative pressure suction effect, introducing the circulating hydrogen and the fresh hydrogen provided by the high-pressure hydrogen tank T into the anode side of the fuel cell stack FCS. When the fuel cell stack FCS is operating at high power, the ejector EJ supplies hydrogen to the fuel cell stack FCS through the third circulation loop; the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell stack FCS through the ejector EJ. When the fuel cell stack FCS is operating at high power, the ejector EJ and the hydrogen circulation pump CP operate in parallel. The hydrogen circulation pump CP supplies hydrogen to the fuel cell stack FCS through a first circulation loop, and the ejector EJ supplies hydrogen to the fuel cell stack FCS through a third circulation loop. The high-pressure hydrogen tank T simultaneously supplies high-pressure hydrogen to the ejector EJ, so that fresh hydrogen and circulating hydrogen enter the anode side of the fuel cell stack FCS through parallel channels.

[0015] Furthermore, when the output power of the fuel cell stack FCS is less than the first power threshold W1, the fuel cell hydrogen circulation system is determined to be in the low-power operating range; when the output power of the fuel cell stack FCS is between the first power threshold W1 and the second power threshold W2, the fuel cell hydrogen circulation system is determined to be in the medium-low power operating range; when the output power of the fuel cell stack FCS is between the second power threshold W2 and the third power threshold W3, the fuel cell hydrogen circulation system is determined to be in the medium-high power operating range; when the output power of the fuel cell stack FCS is greater than the third power threshold W3, the fuel cell hydrogen circulation system is determined to be in the high-power operating range; the first power threshold is less than the second power threshold and the third power threshold.

[0016] Furthermore, the first power threshold W1, the second power threshold W2, and the third power threshold W3 are all provided with hysteresis intervals to avoid the fuel cell frequently switching between adjacent intervals when the power fluctuates; each power threshold includes an upper switching threshold for load determination and a lower switching threshold for load reduction determination, and the upper switching threshold is greater than the corresponding lower switching threshold.

[0017] The beneficial effects of adopting this technical solution are: This invention can switch between four hydrogen circulation modes, select the optimal circulation mode under different power conditions, and reconstruct the topology by controlling the on / off state of the switching valve through a hierarchical control strategy to achieve optimal hydrogen utilization efficiency. It effectively covers the full operating conditions of the fuel cell, avoids drastic fluctuations in circulation flow and anode pressure, thereby improving stability and overall system efficiency.

[0018] This invention proposes a fuel cell topology reconfiguration system that can simultaneously support multiple circulation modes, such as hydrogen circulation pump CP, ejector EJ, and series / parallel hybrid mode. It effectively solves problems such as insufficient driving force of ejector EJ and poor ejection capability in different power ranges, and high energy consumption of hydrogen circulation pump CP. It also optimizes the system oscillation and instability caused by single threshold switching mode, and significantly improves the overall energy efficiency across the entire power range.

[0019] This invention enhances the dynamic adaptability of the hydrogen circulation system of a fuel cell. By dynamically selecting the optimal mode, it achieves efficient and stable control of the system through an architecture of "upper-level decision-making + lower-level execution". The control method ensures the stable operation of the system under scheme switching and complex operating conditions, and effectively alleviates the problems of anode "flooding" and nitrogen accumulation.

[0020] This invention improves the system's robustness and disturbance resistance. By adaptively switching operating conditions, it avoids the long-term high-speed operation of the circulating pump CP, allowing the ejector EJ to undertake the main hydrogen return task within a suitable range. This reduces parasitic power, decreases pump mechanical wear, and helps extend the overall lifespan of the fuel cell stack (FCS), thereby improving the system's reliability and safety. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a fuel cell hydrogen circulation system according to the present invention; Figure 2 This is a schematic diagram of the first circulation loop of the fuel cell hydrogen circulation system in an embodiment of the present invention; Figure 3 This is a schematic diagram of the second circulation loop of the fuel cell hydrogen circulation system in an embodiment of the present invention; Figure 4 This is a schematic diagram of the third circulation loop of the fuel cell hydrogen circulation system in an embodiment of the present invention; Figure 5 This is a schematic diagram of the fourth circulation loop of the fuel cell hydrogen circulation system in an embodiment of the present invention; Figure 6 This is a schematic flowchart of a control method for a fuel cell hydrogen circulation system according to an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings.

[0023] As an embodiment of the present invention, see Figure 1As shown, a fuel cell hydrogen circulation system includes a fuel cell stack (FCS), a high-pressure hydrogen tank (T), an FCU module, a first switching valve (V1), a pressure reducing valve (PRV), a proportional valve (PCV), a three-way valve (DV1), a three-way valve (DV2), a circulation loop (HRC), a water distributor (GLS), and pressure sensors (P1 / P2). The circulation loop (HRC) includes an ejector (EJ), a hydrogen circulation pump (CP), a second switching valve (V2), a check valve (CV1), a third switching valve (V3), and a check valve (CV2). The water distributor integrates a drain valve (LD) and an exhaust valve (PV). One end of the first switching valve (V1) is connected to the high-pressure hydrogen tank (T), and the other end is connected to the inlet of the pressure reducing valve (PRV). The outlet of the pressure reducing valve (PRV) is connected to the inlet of the proportional valve. The inlet of the three-way valve (DV1) is connected to the outlet of the proportional valve (PCV), and the outlet is connected to... The pipelines are connected to the anode inlet of the fuel cell stack (FCS) and the inlet of the ejector (EJ); the circulation loops are all in closed-loop fluid communication with the anode of the fuel cell stack (FCS); the inlet of the water distributor (GLS) is connected to the anode outlet of the fuel cell stack, and the outlet of the water distributor (GLS) is connected to the drain valve (LD), the vent valve (PV), and the three-way valve (DV2); the inlet of the three-way valve (DV2) is connected to the outlet of the water distributor (GLS), and the outlet is connected to the one-way valve (CV2) and the one-way valve (CV1); the other end of the one-way valve (CV1) is connected to the hydrogen circulation pump (CP); the other end of the one-way valve (CV2) is connected to the ejector port of the ejector (EJ); the pressure sensors (P1 / P2) are respectively installed at the inlet and outlet of the fuel cell stack (FCS) to detect the pressure value in real time.

[0024] As a specific embodiment of the present invention, see Figure 2 As shown, in the first circulation loop, the first switching valve V1 is open, and the two ports of the three-way valve DV1 are open and the three ports are closed. The hydrogen in the high-pressure hydrogen tank T can flow through the pressure reducing valve PRV and the proportional valve PCV in sequence. At the same time, the two ports of the three-way valve DV2 are closed and the three ports are open, the second switching valve V2 is closed, and the third switching valve V3 is closed. The return hydrogen after separation by the gas-water separation unit flows through the hydrogen circulation pump CP and merges with the new hydrogen before entering the fuel cell stack FCS.

[0025] As a specific embodiment of the present invention, see Figure 3 As shown, in the second circulation loop, the first switching valve V1 is open, and the two ports of the three-way valve DV1 are closed and the three ports are open. The hydrogen in the high-pressure hydrogen tank T can flow sequentially through the hydrogen supply pressure reducing valve PRV, the proportional valve PCV, and the ejector EJ. At the same time, the two ports of the three-way valve DV2 are closed and the three ports are open, the second switching valve V2 is closed, and the third switching valve V3 is open. The return hydrogen after separation by the gas-water separation unit flows through the hydrogen circulation pump CP and is then ejected by the ejector EJ and merged with the new hydrogen before entering the fuel cell stack FCS.

[0026] As a specific embodiment of the present invention, seeFigure 4 As shown, in the third circulation loop, the first switching valve V1 is open, and the two ports of the three-way valve DV1 are closed and the three ports are open. The hydrogen in the high-pressure hydrogen tank T can flow sequentially through the hydrogen supply pressure reducing valve PRV, the proportional valve PCV, and the ejector EJ. At the same time, the two ports of the three-way valve DV2 are open and the three ports are closed, the second switching valve V2 is closed, and the third switching valve V3 is closed. The return hydrogen after separation by the gas-water separation unit is ejected by the ejector EJ and merges with the new hydrogen into the fuel cell stack FCS.

[0027] As a specific embodiment of the present invention, see Figure 5 As shown, in the fourth circulation loop, the first switching valve V1 is open, and port 2 of the three-way valve DV1 is closed and port 3 is open. The hydrogen in the high-pressure hydrogen tank T can flow sequentially through the hydrogen supply pressure reducing valve PRV, the proportional valve PCV, and the ejector EJ. At the same time, ports 2 and 3 of the three-way valve DV2 are both open, the second switching valve V2 is open, and the third switching valve V3 is closed. The return hydrogen after separation by the gas-water separation unit is ejected by the ejector EJ and merges with the return hydrogen flowing through the hydrogen circulation pump CP into the fuel cell stack FCS.

[0028] As an embodiment of the present invention, see Figure 6 As shown, when the fuel cell stack FCS operates at low power, the hydrogen recirculation pump CP supplies hydrogen to the fuel cell stack FCS through the first recirculation loop; when the fuel cell stack FCS operates at medium to low power, the hydrogen recirculation pump CP and the ejector EJ operate in series, and the hydrogen recirculation pump CP supplies recirculated hydrogen to the fuel cell stack FCS through the second recirculation loop; when the fuel cell stack FCS operates at medium to high power, the ejector EJ supplies hydrogen to the fuel cell stack FCS through the third recirculation loop; when the fuel cell stack FCS operates at high power, the ejector EJ and the hydrogen recirculation pump CP operate in parallel, the hydrogen recirculation pump CP supplies hydrogen to the fuel cell stack FCS through the first recirculation loop, and the ejector EJ supplies hydrogen to the fuel cell stack FCS through the third recirculation loop.

[0029] Specifically, unreacted hydrogen in the fuel cell hydrogen circulation system can be returned to the fuel cell stack (FCS) through the first, second, third, or fourth circulation loops for full reaction. Different operating conditions are assessed, and different circulation modes are selected to control the unreacted hydrogen to return to the stack inlet through different circulation loops. Based on the collected pressure data, the opening of the tail valves (nitrogen venting valve PV and water draining valve LD) is controlled to remove nitrogen and water, preventing nitrogen accumulation and flooding.

[0030] Furthermore, one-way valves are installed on the second, third, and fourth circulation loops of the ejector EJ. The one-way valves are installed to prevent hydrogen in the loop from flowing back from the ejector port, ensuring that the hydrogen always flows unidirectionally along the set main circulation path.

[0031] Furthermore, the fuel cell hydrogen circulation system of the present invention also includes a gas-liquid separator (GLS); the gas after the fuel cell stack FCS reaction is separated into gas and water in the gas-liquid separator (GLS), and the unreacted hydrogen gas used for circulation backflow is discharged through the outlet of the gas-liquid separator (GLS) and enters the circulation loop again to enter the stack for chemical reaction. The separated water and nitrogen gas are discharged through the drain valve (LD) and the exhaust valve; the opening and closing of the drain valve (LD) and the exhaust valve are controlled by the output power status.

[0032] Furthermore, pressure sensors are installed at the inlet and outlet of the fuel cell stack FCS to detect the inlet and outlet pressure values ​​of the fuel cell stack FCS; the proportional valve PCV is used to regulate the hydrogen inlet pressure of the main hydrogen supply pipeline to ensure that the stack can work stably and enhance the dynamic response capability of the system.

[0033] When the first switching valve V1 is open, port 2 of the three-way valve DV1 is open and port 3 is closed, and port 2 of the three-way valve DV2 is closed and port 3 is open, the hydrogen in the high-pressure hydrogen tank T flows through the pressure reducing valve PRV and the proportional valve PCV and then enters the fuel cell stack FCS for reaction; when the second switching valve V2 is open, the reflux hydrogen after chemical reaction flows out from the outlet of the fuel cell stack FCS, is separated by the gas-liquid separator GLS and flows into the first circulation loop into the hydrogen circulation pump CP, and then merges with the new hydrogen from the high-pressure hydrogen tank T and enters the fuel cell stack FCS.

[0034] When the first switching valve V1 is open, port 2 of the three-way valve DV1 is closed and port 3 is open, and port 2 of the three-way valve DV2 is closed and port 3 is open, the hydrogen gas in the high-pressure hydrogen tank T flows through the pressure reducing valve PRV and the proportional valve PCV, and then enters the fuel cell stack FCS through the ejector EJ inlet to react. When the third switching valve V3 is open, the reflux hydrogen after the chemical reaction flows out from the outlet of the fuel cell stack FCS, is separated by the gas-liquid separator GLS, flows into the second circulation loop, and flows into the ejector port of the ejector EJ through the hydrogen circulation pump CP. In the ejector EJ, it merges with the new hydrogen from the high-pressure hydrogen tank T and then flows out of the ejector EJ outlet into the fuel cell stack FCS.

[0035] When the first switching valve V1 is open, port 2 of the three-way valve DV1 is closed and port 3 is open, and port 2 of the three-way valve DV2 is open and port 3 is closed, the hydrogen gas in the high-pressure hydrogen tank T flows through the pressure reducing valve PRV and the proportional valve PCV, and then enters the fuel cell stack FCS through the ejector EJ inlet to react. When open, the reflux hydrogen after chemical reaction flows out from the outlet of the fuel cell stack FCS, is separated by the gas-liquid separator GLS, flows into the third circulation loop and enters the ejector port of the ejector EJ. In the ejector EJ, it merges with the new hydrogen from the high-pressure hydrogen tank T and then flows out of the ejector EJ outlet into the fuel cell stack FCS.

[0036] When the first switching valve V1 is open, port 2 of the three-way valve DV1 is closed and port 3 is open, and ports 2 and 3 of the three-way valve DV2 are both open, the hydrogen gas in the high-pressure hydrogen tank T flows through the pressure reducing valve PRV and the proportional valve PCV, and then enters the fuel cell stack FCS through the ejector EJ inlet for reaction; when the second switching valve V2 is open, the reflux hydrogen gas after chemical reaction flows out from the outlet of the fuel cell stack FCS, is separated by the gas-liquid separator GLS, flows into the fourth circulation loop, is ejected to the ejector EJ inlet, and then merges with the new hydrogen from the high-pressure hydrogen tank T in the ejector EJ before flowing out of the ejector EJ outlet, and then merges with the hydrogen gas refluxed by the hydrogen circulation pump CP before entering the fuel cell stack FCS.

[0037] Furthermore, it can be seen that by controlling the on / off state of the switching valve and the three-way valve, the switching and adjustment of different circulation loops can be realized, thereby improving the hydrogen utilization rate and enabling the system to maintain the best operating state under all working conditions.

[0038] This invention also provides a control method for a fuel cell hydrogen recirculation system, applied to the fuel cell hydrogen recirculation system described above. The control method for the fuel cell hydrogen recirculation system includes: (1) Obtain the operating status of the fuel cell stack FCS; (2) Based on the output power of the fuel cell stack FCS, the circulation mode is automatically switched, that is, when the power reaches a certain range, the on / off state of each switch valve of the fuel cell hydrogen circulation system is controlled to switch to the corresponding circulation mode. (3) A hierarchical structure is adopted, and the system is efficiently and stably controlled through an architecture of "upper-level decision-making + lower-level execution". The upper-level decision-making module constructs a fuzzy rule base based on key parameters such as the fuel cell stack FCS output power, anode inlet and outlet pressure, hydrogen flow rate and parasitic power consumption monitored in real time to realize the identification of operating conditions and adaptive selection of cycle schemes. The lower-level execution module designs controllers for different cycle schemes.

[0039] When the fuel cell stack FCS is operating at low power, the hydrogen circulation pump CP supplies hydrogen to the fuel cell stack FCS through the first circulation loop; the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell stack FCS. When the fuel cell stack FCS is operating at low power, the hydrogen circulation pump CP and the ejector EJ operate in series. The hydrogen circulation pump CP supplies circulating hydrogen to the fuel cell stack FCS via a second circulation loop. The ejector EJ uses high-pressure hydrogen supply to create a negative pressure suction effect, introducing the circulating hydrogen and the fresh hydrogen provided by the high-pressure hydrogen tank T together into the anode side of the fuel cell stack FCS.

[0040] When the fuel cell stack FCS is operating at high power, the ejector EJ supplies hydrogen to the fuel cell stack FCS through the third circulation loop; the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell stack FCS through the ejector EJ.

[0041] When the fuel cell stack FCS is operating at high power, the ejector EJ and the hydrogen circulation pump CP operate in parallel. The hydrogen circulation pump CP supplies hydrogen to the fuel cell stack FCS through a first circulation loop, and the ejector EJ supplies hydrogen to the fuel cell stack FCS through a third circulation loop. The high-pressure hydrogen tank T simultaneously supplies high-pressure hydrogen to the ejector EJ, so that fresh hydrogen and circulating hydrogen enter the anode side of the fuel cell stack FCS through parallel channels.

[0042] This invention, focusing on the core requirement of adapting to different hydrogen circulation schemes, adopts a hierarchical control architecture of "upper-level decision-making + lower-level execution" to achieve efficient, stable, and adaptive control of the fuel cell system. The upper-level decision-making module, based on real-time acquisition and monitoring of key operating parameters such as stack output power, anode inlet and outlet pressures, hydrogen flow rate, and parasitic power consumption, constructs a condition recognition model based on a fuzzy rule base to determine the current operating condition and automatically selects and switches the corresponding hydrogen circulation scheme based on the determination result. The lower-level execution module configures matching controllers for different hydrogen circulation schemes, achieving precise adjustment of anode pressure, circulation flow rate, and related auxiliary components through closed-loop control of relevant actuators.

[0043] Specifically, the FCU module determines the inlet pressure value based on the fuel cell's power output. The FCU module can acquire the voltage signal across the pressure sensor and convert it into a pressure signal. By comparing the fuel cell's inlet pressure value with the target inlet pressure value, the FCU module outputs a PWM power signal to the pressure reducing valve (PRV) and the proportional valve (PCV), and adjusts the opening of the PRV and PCV using an algorithm. During the actual operation of the fuel cell hydrogen recirculation system, the adjustment of the PRV and PCV can be performed in real time, or the adjustment frequency can be set according to the fuel cell's operating conditions.

[0044] When the system stops running, the first switching valve V1 is closed, and the high-pressure hydrogen tank T cannot supply hydrogen to the fuel cell hydrogen circulation system. At this time, the pressure reducing valve PRV and the proportional valve PCV are both closed, all circulation loops are closed, and the hydrogen circulation pump CP and the ejector EJ do not participate in the hydrogen flow.

[0045] Specifically, in this invention, when the output power of the fuel cell stack FCS is less than the first power threshold W1, the fuel cell hydrogen circulation system is determined to be in the low-power operating range; when the output power of the fuel cell stack FCS is between the first power threshold W1 and the second power threshold W2, the fuel cell hydrogen circulation system is determined to be in the medium-low power operating range; when the output power of the fuel cell stack FCS is between the second power threshold W2 and the third power threshold W3, the fuel cell hydrogen circulation system is determined to be in the medium-high power operating range; and when the output power of the fuel cell stack FCS is greater than the third power threshold W3, the fuel cell hydrogen circulation system is determined to be in the high-power operating range.

[0046] The first power threshold, second power threshold, and third power threshold can be specifically designed according to the specific conditions of the fuel cell stack (FCS) and the actual requirements of its operating conditions. The first power threshold, second power threshold, and third power threshold can be equal. In this invention, the first power threshold is less than the second power threshold, which is less than the third power threshold. This effectively avoids frequent state switching in the fuel cell hydrogen circulation system near the threshold points, thus improving system stability.

[0047] When the fuel cell is operating at low power, the hydrogen circulation pump CP supplies hydrogen to the fuel cell stack FCS through the first circulation loop, and the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell. The speed of the hydrogen circulation pump CP is controlled and adjusted.

[0048] At this time, the first switching valve V1 opens, port 2 of the three-way valve DV1 opens and port 3 closes, port 2 of the three-way valve DV2 closes and port 3 opens, the second switching valve V2 opens, the first circulation loop is activated, and the unreacted hydrogen in the fuel cell flows back to the fuel cell for reaction through the first circulation loop. The returned hydrogen flows out from the outlet of the fuel cell stack FCS, enters the gas-liquid separator GLS for gas-liquid separation, flows into the first circulation loop, passes through the hydrogen circulation pump CP and the second switching valve V2, and flows into the fuel cell stack FCS. Fresh hydrogen from the high-pressure hydrogen tank T merges with the returned hydrogen and enters the fuel cell stack FCS.

[0049] When the fuel cell switches from low-power operation to medium-low power operation, the first circulation loop closes and the second circulation loop opens. Specifically, the FCU module controls the first switching valve V1 to open, the two ports of the three-way valve DV1 to close and the three port to open, the two ports of the three-way valve DV2 to close and the three port to open, the second switching valve V2 to close, and the third switching valve V3 to open.

[0050] By connecting the outlet of the hydrogen circulation pump CP to the ejector port of the ejector EJ, the hydrogen flowing out of the hydrogen circulation pump CP can be ejected by the ejector EJ to achieve backflow, thus making better use of the circulation capacity of the hydrogen circulation pump CP and the ejector EJ.

[0051] When the fuel cell is operating at low power, the hydrogen circulation pump CP and ejector EJ supply hydrogen to the fuel cell stack FCS through the second circulation loop, while the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell stack FCS through ejector EJ.

[0052] At this time, the first switching valve V1 opens, port 2 of the three-way valve DV1 is closed and port 3 is open, port 2 of the three-way valve DV2 is closed and port 3 is open, the third switching valve V3 opens, and the second circulation loop is activated. Unreacted hydrogen in the fuel cell stack FCS can flow back into the fuel cell stack FCS through the second circulation loop for complete reaction. The returned hydrogen flows out from the fuel cell outlet, enters the gas-liquid separator GLS for gas-liquid separation, flows into the second circulation loop, and then passes through the check valve, hydrogen circulation pump CP, and ejector EJ before re-entering the fuel cell stack FCS. Fresh hydrogen from the high-pressure hydrogen tank T merges with the returned hydrogen before entering the fuel cell stack FCS.

[0053] When the fuel cell switches from low-to-medium power operation to medium-to-high power operation, the second circulation loop closes and the third circulation loop opens. Specifically, when the FCU module controls the first switching valve V1 to open, and the two ports of the three-way valve DV1 to close and the three port to open, and the two ports of the three-way valve DV2 to open and the three port to close, the third switching valve V3 closes and opens, and the hydrogen circulation pump CP closes.

[0054] When the fuel cell is operating at high power, the ejector EJ supplies hydrogen to the fuel cell stack FCS through the third circulation loop, and the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell stack FCS through the ejector EJ.

[0055] At this time, when the first switching valve V1 opens, and the two ports of the three-way valve DV1 are closed and the three port is open, and the two ports of the three-way valve DV2 are open and the three port is closed, the third switching valve V3 is closed and then opened, thus opening the third circulation loop. Unreacted hydrogen in the fuel cell stack FCS can then flow back into the fuel cell stack FCS for complete reaction. The returned hydrogen flows out from the fuel cell outlet, enters the gas-liquid separator GLS for gas-liquid separation, flows into the third circulation loop, and then passes through the check valve and ejector EJ before re-entering the fuel cell stack FCS. Fresh hydrogen from the high-pressure hydrogen tank T merges with the returned hydrogen before entering the fuel cell stack FCS.

[0056] When the fuel cell switches from medium-high power operation to high power operation, the third circulation loop closes and the fourth circulation loop opens. Specifically, the FCU module controls the first switching valve V1 to open, the second port of the three-way valve DV1 to close and the third port to open, the second and third ports of the three-way valve DV2 to open, the second switching valve V2 to open, the third switching valve V3 to close and open, and the hydrogen circulation pump CP to start.

[0057] When the fuel cell is operating at high power, the hydrogen circulation pump CP and ejector EJ supply hydrogen to the fuel cell stack FCS through the fourth circulation loop, while the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell stack FCS through ejector EJ.

[0058] At this time, the first switching valve V1 opens, port 2 of the three-way valve DV1 closes and port 3 opens, ports 2 and 3 of the three-way valve DV2 both open, the second switching valve V2 opens, and the third switching valve V3 closes and opens, thus activating the fourth circulation loop. Unreacted hydrogen in the fuel cell stack FCS can flow back to the fuel cell stack FCS through the fourth circulation loop for complete reaction. The returned hydrogen flows out from the fuel cell outlet, enters the gas-liquid separator GLS for gas-liquid separation, flows into the fourth circulation loop, and sequentially passes through the check valve, ejector EJ, and hydrogen circulation pump CP before re-entering the fuel cell stack FCS. Fresh hydrogen from the high-pressure hydrogen tank T merges with the returned hydrogen before entering the fuel cell stack FCS.

[0059] Furthermore, in this invention, when gas enters the ejector EJ, it can be considered that the ejector EJ is activated, and when no gas flows through the ejector EJ, it can be considered that the ejector EJ is deactivated.

[0060] The fuel cell hydrogen circulation system and its control method of the present invention analyze the operating power of the fuel cell at the upper level and select the most suitable hydrogen circulation mode. At the lower level, a controller is used to achieve closed-loop control of the hydrogen circulation pump CP, ejector EJ, etc., to precisely adjust the pump speed and the working state of the ejector EJ. This enables the fuel cell hydrogen circulation system and its control method to simultaneously meet the optimal circulation requirements at low power, medium-low power, medium-high power, and high power, effectively improving the efficiency and energy saving of the fuel cell hydrogen circulation system.

[0061] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. The present invention is not limited to the above embodiments; the embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The appended claims and their equivalents define the scope of protection of this invention.

[0062] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A fuel cell hydrogen recirculation system, characterized in that, include: Fuel cell stack FCS, high-pressure hydrogen tank T, FCU module, first switching valve V1, pressure reducing valve PRV, proportional valve PCV, three-way valve DV1, three-way valve DV2, circulation loop HRC, water distributor GLS, pressure sensor P1 and pressure sensor P2. The circulation loop HRC includes an ejector EJ, a hydrogen circulation pump CP, a second switching valve V2, a one-way valve CV1, a third switching valve V3, and a one-way valve CV2. The water distributor GLS is integrated with a drain valve LD and an air vent valve PV. One end of the first switching valve V1 is connected to the high-pressure hydrogen tank T, and the other end is connected to the inlet of the pressure reducing valve PRV. The outlet of the pressure reducing valve PRV is connected to the inlet of the proportional valve PCV. The inlet of the three-way valve DV1 is connected to the outlet of the proportional valve PCV, and the outlet is connected via pipelines to the anode inlet of the fuel cell stack FCS and the inlet of the ejector EJ, respectively. The circulation loop HRC is in closed-loop fluid communication with the anode of the fuel cell stack FCS. The inlet of the water distributor GLS is connected to the anode outlet of the fuel cell stack. The outlet of the water distributor GLS is connected to the drain valve LD, the vent valve PV, and the three-way valve DV2, respectively; the inlet of the three-way valve DV2 is connected to the outlet of the water distributor GLS, and the outlet of the three-way valve DV2 is connected to the one-way valve CV2 and the one-way valve CV1, respectively; the other end of the one-way valve CV1 is connected to the hydrogen circulation pump CP; the other end of the one-way valve CV2 is connected to the ejector port of the ejector EJ; the pressure sensor P1 and the pressure sensor P2 are respectively installed at the inlet and outlet of the fuel cell stack FCS to detect the pressure value in real time. The circulation loop forms different states of circulation loops based on the adjustment of three-way valve DV1, three-way valve DV2, second switching valve V2 and / or third switching valve V3, including a first circulation loop, a second circulation loop, a third circulation loop and / or a fourth circulation loop.

2. The fuel cell hydrogen recirculation system according to claim 1, characterized in that, The first circulation loop is equipped with a one-way valve CV1, a hydrogen circulation pump CP, and a second switching valve V2 in sequence along the hydrogen flow direction to realize a single hydrogen circulation pump mode.

3. The fuel cell hydrogen recirculation system according to claim 1, characterized in that, The second circulation loop is sequentially equipped with a one-way valve CV1, a hydrogen circulation pump CP, a third switching valve V3, and an ejector EJ along the hydrogen flow direction, realizing the series connection mode of the hydrogen circulation pump and the ejector.

4. A fuel cell hydrogen recirculation system according to claim 1, characterized in that, The third circulation loop is equipped with a one-way valve CV2 and an ejector EJ in sequence along the hydrogen flow direction to realize the single ejector mode.

5. A fuel cell hydrogen recirculation system according to claim 1, characterized in that, The fourth circulation loop includes a first circulation loop and a third circulation loop connected in parallel. The two loops form independent hydrogen channels and together constitute a composite circulation path for supplying hydrogen to the fuel cell stack (FCS) in a parallel structure. The fourth circulation loop is provided with the first circulation loop including a one-way valve CV1, a hydrogen circulation pump CP, and a second switching valve V2, and the third circulation loop including a one-way valve CV2 and an ejector EJ, in sequence along the hydrogen flow direction, realizing the parallel connection mode of the hydrogen circulation pump and the ejector.

6. A fuel cell hydrogen recirculation system according to claim 1, characterized in that, The FCU module is used to control the on / off state of the switching valve and the opening frequency and duration of the drain valve LD and the exhaust valve PV based on the output power of the fuel cell.

7. A control method for a fuel cell hydrogen circulation system, characterized in that, The method applied to the hydrogen recirculation system of the fuel cell according to any one of claims 1-6 includes the following steps: (1) Obtain the operating status of the fuel cell stack FCS; (2) Based on the output power of the fuel cell stack FCS, the circulation mode is automatically switched, that is, when the power reaches a certain range, the on / off state of each switch valve of the fuel cell hydrogen circulation system is controlled to switch to the corresponding circulation mode. (3) A hierarchical structure is adopted, and the system is efficiently and stably controlled through an architecture of upper-level decision-making and lower-level execution; The upper-level decision-making module constructs a fuzzy rule base based on real-time monitoring of key parameters such as fuel cell stack FCS output power, anode inlet and outlet pressure, hydrogen flow rate, and parasitic power consumption to achieve operating condition identification and adaptive selection of cycle schemes; the lower-level execution module designs controllers for different cycle schemes.

8. The control method for a fuel cell hydrogen circulation system according to claim 7, characterized in that, When the fuel cell stack FCS is operating at low power, the hydrogen circulation pump CP supplies hydrogen to the fuel cell stack FCS through the first circulation loop; the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell stack FCS. When the fuel cell stack FCS is operating at low power, the hydrogen circulation pump CP and the ejector EJ work in series. The hydrogen circulation pump CP delivers circulating hydrogen to the fuel cell stack FCS via the second circulation loop. The ejector EJ uses high-pressure hydrogen supply to form a negative pressure suction effect, introducing the circulating hydrogen and the fresh hydrogen provided by the high-pressure hydrogen tank T into the anode side of the fuel cell stack FCS. When the fuel cell stack FCS is operating at high power, the ejector EJ supplies hydrogen to the fuel cell stack FCS through the third circulation loop; the high-pressure hydrogen tank T simultaneously supplies hydrogen to the fuel cell stack FCS through the ejector EJ. When the fuel cell stack FCS is operating at high power, the ejector EJ and the hydrogen circulation pump CP operate in parallel. The hydrogen circulation pump CP supplies hydrogen to the fuel cell stack FCS through a first circulation loop, and the ejector EJ supplies hydrogen to the fuel cell stack FCS through a third circulation loop. The high-pressure hydrogen tank T simultaneously supplies high-pressure hydrogen to the ejector EJ, so that fresh hydrogen and circulating hydrogen enter the anode side of the fuel cell stack FCS through parallel channels.

9. A control method for a fuel cell hydrogen circulation system according to claim 7 or 8, characterized in that, When the output power of the fuel cell stack FCS is less than the first power threshold W1, the fuel cell hydrogen circulation system is determined to be in the low-power operating range; when the output power of the fuel cell stack FCS is between the first power threshold W1 and the second power threshold W2, the fuel cell hydrogen circulation system is determined to be in the medium-low power operating range; when the output power of the fuel cell stack FCS is between the second power threshold W2 and the third power threshold W3, the fuel cell hydrogen circulation system is determined to be in the medium-high power operating range; when the output power of the fuel cell stack FCS is greater than the third power threshold W3, the fuel cell hydrogen circulation system is determined to be in the high-power operating range; the first power threshold is less than the second power threshold and the third power threshold.

10. The control method for a fuel cell hydrogen circulation system according to claim 9, characterized in that, The first power threshold W1, the second power threshold W2, and the third power threshold W3 are all provided with hysteresis intervals to avoid the fuel cell frequently switching between adjacent intervals when the power fluctuates; each power threshold includes an upper switching threshold for load determination and a lower switching threshold for load reduction determination, and the upper switching threshold is greater than the corresponding lower switching threshold.

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