A fuel cell multi-stack system with a gas-balanced backpressure structure and a control method thereof

Abstract

The present invention belongs to the field of fuel cell technology, and discloses a fuel cell multi-stack system with a gas-equalizing back pressure structure and a control method thereof, wherein a hydrogen gas source is used to input hydrogen into the multi-stack system and the gas-equalizing back pressure tank respectively; the outlet end of the multi-stack system is provided with a normally closed pulse exhaust valve, which can perform pulse exhaust, so that the impurity gas collected inside the multi-stack system enters the gas-liquid separator for gas-liquid separation; the gas-liquid separator is provided with a first outlet, and a second normally closed solenoid valve is provided at the first outlet, which is used to discharge the impurity gas and liquid water after gas-liquid separation to the outside world; when the load current changes, and the hydrogen flow rate in the hydrogen gas source lags behind and has not yet reached the end of the multi-stack system, the hydrogen in the gas-equalizing back pressure tank enters the multi-stack system under the action of the pressure difference, providing the multi-stack system with a reaction gas. The present invention can effectively increase the output back pressure without increasing the parasitic power, thereby improving the consistency between the multi-stack systems and the dynamic response capability of the system.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and more specifically, relates to a fuel cell multi-stack system with a gas-balanced back pressure structure and a control method thereof. Background Art

[0002] Fuel cell multi-stack systems are suitable for high-power output scenarios. The system is large in size, the flow of reactant gas and cooling medium is large, and the distribution unevenness is exacerbated. The demand-side load change signal flow and the supply-side energy flow are complex and coordinated, exacerbating the uneven distribution of gas. Existing fuel cell multi-stack systems are directly connected to multiple stack inlets through parallel pipes. The gases at the outlets of multiple stacks are collected and discharged from the system, which can easily lead to gas shortages and flooding in the terminal stacks. Therefore, the uniform gas drainage design of the fuel cell multi-stack system helps to improve the system life and output stability. Fuel cell systems generally improve output characteristics by adding a back-pressure valve at the stack outlet to ensure operating pressure.

[0003] CN202210992389.7 discloses a uniform gas supply system for multiple fuel cell stacks. This system uses an air diverter to ensure uniform intake air. The cathode outlets of multiple fuel cell stacks are connected to the inlet of a water-gas separation tank, whose gas outlet is connected to an exhaust pipe. However, the system does not describe the diverter's structural design or how it ensures consistent intake air pressure across all fuel cell stacks. Furthermore, the system exhibits a slow response to dynamic load changes, making transient fuel starvation a frequent occurrence. CN201810874914.9 discloses a fuel cell backpressure regulator with gas-liquid separation capabilities. This device is used to regulate backpressure during performance testing of hydrogen-oxygen or hydrogen-air fuel cells. The device includes a one-way valve, a pressure gauge, a backpressure valve, a water collection tank, a water level display tube, a drain valve, and piping. This device separates and discharges unreacted gas and liquid water droplets from the fuel cell. However, the system suffers from complex structure and wasteful unreacted gas discharge. Summary of the Invention

[0004] In view of the defects of the prior art, the purpose of the present invention is to provide a fuel cell multi-stack system with a uniform gas back pressure structure and a control method thereof, so as to solve the problems of low back pressure, low output voltage and weak dynamic response capability under variable load in the existing fuel cell multi-stack system.

[0005] To achieve the above objectives, the present invention provides a fuel cell multi-stack system with a gas-balanced backpressure structure, comprising a hydrogen gas source, a fuel cell stack system, a gas-balanced backpressure tank, and a gas-liquid separator, wherein:

[0006] The hydrogen source is used to input hydrogen into the multi-stack system and the equalizing gas back pressure tank respectively; the outlet end of the multi-stack system is provided with a normally closed pulse exhaust valve, and the normally closed pulse exhaust valve can perform pulse exhaust, so that the impurity gas collected inside the multi-stack system enters the gas-liquid separator for gas-liquid separation; the gas-liquid separator is provided with a first outlet, and a second normally closed solenoid valve is provided at the first outlet, which is used to discharge the impurity gas and liquid water after gas-liquid separation to the outside; it is used to discharge the impurity gas and liquid water after gas-liquid separation to the outside; when the load current changes and the hydrogen flow in the hydrogen source lags and has not reached the end of the multi-stack system, the hydrogen in the equalizing gas back pressure tank can enter the multi-stack system under the action of the pressure difference, providing reaction gas for the multi-stack system.

[0007] Furthermore, the multi-stack system includes at least two parallel fuel cell stacks, and a normally open solenoid valve is provided between each fuel cell stack and the hydrogen gas source, and the normally open solenoid valve is used to control the on and off of hydrogen; the normally closed pulse exhaust valve is provided at the outlet of each fuel cell stack, which is used to pulse exhaust the multi-stack system.

[0008] Furthermore, the multi-stack system also includes an external controller, and a first pressure sensor is provided on the gas-liquid separator for recording and transmitting the internal pressure signal thereof to the external controller; a second pressure sensor is provided on the gas equalizing back pressure tank for recording and transmitting the internal pressure signal thereof to the external controller; when the pressure in the gas-liquid separator is greater than a preset multiple of the pressure in the gas equalizing back pressure tank, the external controller is used to control the opening of the second normally closed solenoid valve to discharge the impurity gas and liquid water of the multi-stack system to the outside.

[0009] Furthermore, a liquid level sensor is provided on the gas-liquid separator for recording and transmitting the liquid level height inside it to an external controller. When the liquid level height inside the gas-liquid separator is greater than the preset maximum liquid level height, the external controller can control the second normally closed solenoid valve to open to discharge the separated impurity gas and liquid water to the outside.

[0010] Furthermore, a voltage patrol meter is provided on the multi-stack system for reading and outputting the voltage signal of each stack in the multi-stack system to the external controller. The external controller determines and controls the opening and closing of the normally closed pulse exhaust valve based on the voltage signal.

[0011] Furthermore, the gas-liquid separator is provided with a second outlet, which is connected to the gas equalization back pressure tank via a first normally closed solenoid valve. When the multi-stack system is started or stopped, the first normally closed solenoid valve is opened to purge the multi-stack system.

[0012] According to another aspect of the present invention, a control method for a fuel cell multi-stack system having a gas back pressure equalization structure as described above is also disclosed, the control method comprising the following steps:

[0013] S1 acquires in real time the liquid level of the gas-liquid separator, the operation time of the fuel cell system, the pressure of the gas-liquid separator, the pressure of the gas equalization back pressure tank, the exhaust time of the second normally closed solenoid valve, and the voltage signal of each fuel cell in the fuel cell system when the multi-stack system is running;

[0014] S2 determines whether any of the voltage signals is less than the preset minimum single-chip voltage: if so, proceed to the next step; if not, repeat the determination of step S2;

[0015] S3 opens the pulse exhaust valve corresponding to the stack whose voltage signal is less than the minimum single-chip voltage, continues exhausting for a first preset time, and then closes;

[0016] S4 determines whether the liquid level is greater than or equal to a preset maximum liquid level: if so, proceed to the next step; if not, repeat the determination of step S4;

[0017] Alternatively, determine whether the pressure of the gas-liquid separator is greater than or equal to a preset multiple of the pressure of the gas equalization back pressure tank: if so, proceed to the next step; if not, repeat the determination of step S4;

[0018] S5: Open the second normally closed solenoid valve to exhaust gas and record the exhaust time. When the exhaust time is greater than or equal to the preset exhaust time, close the second normally closed solenoid valve.

[0019] S6 determines whether the running time is greater than or equal to the preset running time: if so, the multi-stack system is controlled to stop running; if not, steps S1-S6 are repeated until the multi-stack system stops running.

[0020] Furthermore, in step S5, the preset multiple is 0.5 times to 0.8 times.

[0021] Furthermore, the minimum single-chip voltage is 0.3V; the maximum liquid level is preferably within the gas-liquid separator. At height.

[0022] Furthermore, the first preset time is preferably 1 second, and the exhaust time of the exhaust gas is preferably 2 seconds to 4 seconds.

[0023] The above technical solution conceived by the present invention has the following advantages compared with the prior art:

[0024] 1. The improvement of the gas equalization back pressure structure of the fuel cell multi-stack system of the present invention compared with the existing fuel cell multi-stack system is: by adding a gas equalization back pressure tank at the air intake end, the gas pressure of the terminal stack of the multi-stack system is guaranteed without increasing the air intake source. When the load current changes, the gas output by the hydrogen gas source cannot be delivered to the terminal stack in a short time, but the reaction in the stack is still consuming gas. At this time, the hydrogen gas stored in the gas equalization back pressure tank enters the terminal stack under the action of the pressure difference, providing additional reaction gas for the terminal stack, thereby improving the dynamic response capability of the fuel cell multi-stack system when the load current changes; therefore, the present invention can effectively increase the output back pressure without increasing the parasitic power, thereby improving the consistency between the stack and the multi-stack system and the dynamic response capability of the system.

[0025] 2. The present invention controls the on / off of the gas equalizing back pressure tank and the gas-liquid separator by setting a normally closed solenoid valve, so as to achieve complete purge of the gas equalizing back pressure tank and the entire fuel cell multi-stack system when the fuel cell multi-stack system is started and stopped, thereby ensuring the safety of the fuel cell multi-stack system. The present invention has a simple structure, a simple control method and a high degree of automation.

[0026] 3. The present invention controls the normally closed solenoid valve at the outlet of the gas-liquid separator to exhaust and remove water to the outside by setting the maximum drainage pressure and comparing the pressure difference between the gas-equalizing back pressure tank and the gas-liquid separator. Sufficient pressure difference can provide sufficient pulse exhaust power, thereby ensuring the pulse exhaust and water removal effect and improving the fuel utilization rate of the system.

[0027] 4. In the control method of the gas-balanced back pressure structure of the fuel cell multi-stack system of the present invention: by setting the minimum single-chip voltage, the stack is guaranteed to intermittently discharge impurity water vapor, thereby ensuring the output performance of the fuel cell multi-stack system and improving the battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of a fuel cell multi-stack system with a gas back pressure equalization structure provided by an embodiment of the present invention;

[0029] Figure 2 This is a flow chart of a control method for a fuel cell multi-stack system with a gas back pressure equalization structure provided by an embodiment of the present invention.

[0030] In the figure: 1-hydrogen gas source, 2-first solenoid valve, 3-first fuel cell voltage sensor, 4-second solenoid valve, 5-second fuel cell voltage sensor, 6-gas equalization back pressure tank, 7-first pressure sensor, 8-first normally closed solenoid valve, 9-first fuel cell, 10-second fuel cell, 11-fourth solenoid valve, 12-fifth solenoid valve, 13-second pressure sensor, 14-liquid level sensor, 15-gas-liquid separator, 16-second normally closed solenoid valve. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0033] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0034] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0035] To achieve the above objectives, the present invention provides a fuel cell multi-stack system with a uniform gas back pressure structure, combined with Figure 1 As shown, the structure includes a hydrogen gas source 1, a fuel cell system, a gas equalization back pressure tank 6 and a gas-liquid separator 15 connected by pipelines, wherein:

[0036] The outlet of the hydrogen source 1 is connected to the inlet of the fuel cell system and an inlet of the equalizing gas back-pressure tank 6 respectively, and the output hydrogen enters the fuel cell system and the equalizing gas back-pressure tank 6 respectively; a normally closed pulse exhaust valve for pulse exhaust of the fuel cell system is provided at the outlet of the fuel cell system, and the normally closed pulse exhaust valve is used to pulse exhaust the multi-stack system, so that the impurity gas collected inside the multi-stack system enters the gas-liquid separator for gas-liquid separation; the gas-liquid separator 15 has at least one outlet (i.e., the first outlet), and a second normally closed solenoid valve 16 is provided at the outlet, and when the second normally closed solenoid valve 16 is opened, the impurity gas and liquid water after gas-liquid separation can be discharged to the outside; when the load current changes, and the hydrogen in the hydrogen source 1 has not yet reached the fuel cell in the multi-stack system (especially has not yet entered the end fuel cell) due to flow lag, the hydrogen in the equalizing gas back-pressure tank can enter the multi-stack system under the action of pressure difference, and provide reaction gas for the multi-stack system to increase the corresponding speed;

[0037] In a preferred embodiment, the fuel cell system includes at least two fuel cells connected in parallel, and a normally open solenoid valve is provided between each fuel cell and the hydrogen gas source 1, and the normally open solenoid valve is used to control the on and off of hydrogen; specifically, the hydrogen in the hydrogen gas source 1 enters the fuel cell through the normally open solenoid valve to react and generate electrical energy, and when hydrogen is not needed, the normally open solenoid valve is closed.

[0038] In a preferred embodiment, a normally closed pulse exhaust valve is provided at the outlet of each fuel cell stack, and each normally closed pulse exhaust valve is used to individually realize pulse exhaust of each fuel cell stack; specifically, when hydrogen reacts in the fuel cell stack system, impurity gas with a certain humidity will be generated. During the reaction, the normally closed pulse exhaust valve is closed. When exhaust is required, the normally closed pulse exhaust valve is opened to discharge the impurity gas from the fuel cell stack.

[0039] In a preferred embodiment, the multi-stack system with an equalizing gas back pressure structure further includes an external controller (not shown in the figure), and the multi-stack system further includes an external controller, a first pressure sensor 7 is provided on the gas-liquid separator 15, for recording and transmitting the internal pressure signal thereof to the external controller; a second pressure sensor 13 is provided on the equalizing gas back pressure tank 6, for recording and transmitting the internal pressure signal thereof to the external controller; when the pressure in the gas-liquid separator 15 is greater than the preset multiple pressure in the equalizing gas back pressure tank 6, the external controller is used to control the second normally closed solenoid valve 16 to open, so as to discharge the impurity gas and liquid water of the multi-stack system to the outside; in this embodiment, the opening and closing of each solenoid valve are controlled by the aforementioned external controller ( Figure 1 (not shown) for centralized control.

[0040] In a more preferred embodiment, a liquid level sensor 14 is provided on the gas-liquid separator 15 for recording and transmitting the liquid level height inside it to an external controller. When the liquid level height inside the gas-liquid separator 15 is greater than the preset maximum liquid level height, the external controller can control the second normally closed solenoid valve 16 to open to discharge the separated impurity gas and liquid water to the outside.

[0041] In a more preferred embodiment, a voltage patrol meter is provided on the aforementioned fuel cell system for reading and outputting the voltage signal of each fuel cell in the fuel cell system to an external controller, and the external controller determines and controls the opening and closing of the normally closed pulse exhaust valve based on the voltage signal.

[0042] In a preferred embodiment, the gas-liquid separator 15 also includes another outlet (i.e., the second outlet), which is connected to another inlet of the gas equalization back pressure tank 6 via the first normally closed solenoid valve 8. When the multi-stack system is started and stopped, the first normally closed solenoid valve 8 is opened to achieve a thorough purge of the multi-stack system; specifically, when the multi-stack system is turned on or off, inert gas is introduced for purge, and the first normally closed solenoid valve 8 is opened so that the inert gas can be completely purged into each pipeline in the multi-stack system to purge the multi-stack system cleanly.

[0043] The aforementioned external controller is also connected to other actuators (such as normally closed pulse exhaust valves, etc.) in the fuel cell multi-stack system to issue control instructions to control the actuators to perform corresponding actions.

[0044] In another embodiment, Figure 2 As shown, a control method for any of the above-mentioned gas equalization back pressure structures is also provided, and the control method includes the following steps:

[0045] S1 records in real time the liquid level of the gas-liquid separator, the operation time of the fuel cell system, the pressure of the gas-liquid separator, the pressure of the gas equalization back pressure tank, the exhaust time of the second normally closed solenoid valve, and the voltage signal of each fuel cell in the fuel cell system when the multi-stack system is running;

[0046] S2 determines whether the voltage signal of any stack is less than the preset minimum single-chip voltage: if so, proceed to the next step; if not, repeat the judgment of step S2; that is, the number of voltage signals recorded is equal to the number of stacks in the stack system. When judging, the condition for proceeding to the next step can only be determined to be met when any voltage signal is less than the preset minimum single-chip voltage;

[0047] S3 opens the normally closed pulse exhaust valve corresponding to the battery stack whose voltage signal is less than the preset minimum single-chip voltage, keeps it open for a first preset time, and then closes it. Specifically, the outlet of each battery stack is provided with a corresponding normally closed pulse exhaust valve. When it is determined in step S2 that the voltage signal of a battery stack is less than the preset minimum single-chip voltage, the corresponding normally closed pulse exhaust valve is opened to enable the battery stack to start discharging impurity gases and water into the gas-liquid separator 15 to increase its output voltage. The opening degree and opening time of each pulse exhaust valve are the same.

[0048] S4 determines whether the liquid level of the gas-liquid separator 15 is greater than or equal to the preset maximum liquid level. If so, the next step is executed. This is because when the liquid level is greater than or equal to the preset maximum liquid level, it proves that the gas-liquid separator 15 is full of reaction water and needs to be discharged outside the system. Otherwise, the excess liquid water will reduce the storage space of the impurity gas and reduce the pressure difference between the fuel cell stack and the gas-liquid separator, affecting the pulse drainage voltage recovery effect. If not, the judgment of step S4 is repeated until the liquid level is greater than or equal to the preset maximum liquid level.

[0049] Or, determine whether the pressure of the gas-liquid separator 15 is greater than or equal to a preset multiple of the pressure of the equalizing gas back pressure tank 6: if so, execute the next step; if not, re-perform the judgment of step S5; the reason for performing this judgment is that if the pressure of the gas-liquid separator 15 reaches a preset multiple of the equalizing gas back pressure tank pressure, when the fuel cell stack is pulse-exhausted, the pressure difference between the fuel cell stack inlet and the gas-liquid separator 15 is too small, and the liquid water in the fuel cell stack cannot be discharged in time, affecting the pulse exhaust water removal and voltage recovery effect.

[0050] S5 opens the second normally closed solenoid valve 16 to exhaust and records the exhaust time. When the exhaust time is greater than or equal to the preset exhaust time, closes the second normally closed solenoid valve 16 to stop exhausting.

[0051] S6 determines whether the actual operating time of the fuel cell multi-stack system is greater than or equal to the preset operating time: if so, the fuel cell multi-stack system is controlled to stop running; if not, steps S1-S6 are repeated until the operating time of the fuel cell multi-stack system reaches the preset operating time and stops running.

[0052] In a preferred embodiment, the preset time for opening the normally closed pulse exhaust valve is 0.5s-1.5s, such as 0.5s, 0.6s, 0.8s, 0.9s, 1.1s, 1.3s, 1.5s, etc. The most preferred time is 1s, which can ensure that the reaction gas or liquid water in the fuel cell stack can be fully discharged.

[0053] In a preferred embodiment, in step S5, the preset multiple is 0.5 times to 0.8 times, which can ensure that there is a sufficient pressure difference between the gas-liquid separator 15 and the gas equalization back pressure tank 6 to provide power for pulse exhaust and ensure smooth drainage.

[0054] In a preferred embodiment, the aforementioned preset minimum single-chip voltage is at least 0.3V, which can ensure that the fuel cell stack intermittently discharges impurities, water vapor, etc. at a certain frequency, thereby ensuring the output performance of the fuel cell system and further improving the service life of the battery.

[0055] In a preferred embodiment, the maximum liquid level is The height can ensure that enough reaction water is collected in the gas-liquid separator while retaining enough storage space for impurity gas. Otherwise, excessive liquid water will reduce the storage space for impurity gas and reduce the pressure difference between the fuel cell stack and the gas-liquid separator, affecting the pulse drainage voltage recovery effect.

[0056] In a preferred embodiment, the preset exhaust time of the exhaust gas is 2s-4s, such as 2s, 3s, 3.5s, etc., which can ensure sufficient exhaust.

[0057] In order to better illustrate the implementation details of the present invention, the following examples are provided to further illustrate the present invention. It should be understood that the following examples are only intended as optimal implementation methods and are not intended to limit the scope of protection of the present invention.

[0058] Example 1

[0059] like Figure 1 As shown, the gas equalization back pressure structure of the fuel cell multi-stack system provided in this embodiment includes a hydrogen gas source 1, a first fuel cell stack 9, a second fuel cell stack 10, a gas equalization back pressure tank 6, a gas-liquid separator 15 and an external controller; wherein, the outlet gas path of the hydrogen gas source 1 is divided into three paths, the first path is connected to the inlet of the first fuel cell stack 9, the second path is connected to the inlet of the second fuel cell stack 10, and the third path is connected to the first inlet of the gas equalization back pressure tank 6. A normally open first solenoid valve 2 is provided at the inlet of the first fuel cell stack 9, and a normally open second solenoid valve 4 is provided at the inlet of the second fuel cell stack 10. The two solenoid valves respectively control whether the fuel cell stack enters hydrogen.

[0060] The outlet end of the first fuel cell stack 9 is connected to the gas-liquid separator 15. The outlet end of the first fuel cell stack 9 is also provided with a normally closed fourth solenoid valve 11 (i.e., a normally closed pulse solenoid valve). The solenoid valve is used to open and close the outlet of the first fuel cell stack 9 so that the impurity gas with humidity inside the first fuel cell stack 9 can accumulate and be discharged; the first fuel cell stack 9 is also provided with a first fuel cell stack voltage sensor 3 (i.e., a voltage patrol meter) for collecting the voltage signal of the first fuel cell stack 9.

[0061] The outlet end of the second fuel cell stack 10 is also connected to the gas-liquid separator 15, so that the first fuel cell stack 9 and the second fuel cell stack 10 are in parallel, and the gas paths of the two are merged into one path at the inlet of the gas-liquid separator 15. A normally closed fifth solenoid valve 12 (i.e., a normally closed pulse solenoid valve) is also provided at the outlet of the second fuel cell stack 10, which is used to independently control the accumulation and discharge of impurity water vapor generated by the reaction in the second fuel cell stack 10; a second fuel cell stack voltage sensor 5 (i.e., a voltage patrol meter) is provided on the second fuel cell stack 10, which is used to collect the voltage signal of the second fuel cell stack 10.

[0062] The gas-liquid separator 15 is used to separate the impurity gas discharged from the gas-liquid separation stack. It has two outlets. The first outlet is connected to the second inlet of the gas equalization back pressure tank 6, and a first normally closed solenoid valve 8 is provided on this passage; the second outlet of the gas-liquid separator 15 is connected to the outside world, and a second normally closed solenoid valve 16 is also provided at the second outlet. The solenoid valve is used to connect or disconnect the gas-liquid separator 15 with the external environment to discharge a preset amount of liquid water and impurity gas after gas-liquid separation into the external environment.

[0063] In this embodiment, a first pressure sensor 7 is also provided in the gas equalizing back pressure tank 6 for collecting the pressure in the gas equalizing back pressure tank 16; the gas-liquid separator 15 is a tank body, and a second pressure sensor 13 and a liquid level sensor 14 are also provided inside it, which are used to collect the internal pressure P and liquid height H in the gas-liquid separator 15 respectively; the first fuel cell stack 9 and the second fuel cell stack 10 are respectively provided with voltage patrol meters for reading the voltage signals of the corresponding fuel cell stacks and outputting them to the external controller.

[0064] When the load current changes, the gas output by the hydrogen source 1 cannot be delivered to the second fuel cell stack 10 at the end in a short time, but the reaction in the fuel cell stack is still consuming gas. At this time, the hydrogen gas stored in the equalizing back pressure tank 6 enters the end fuel cell stack under the action of the pressure difference, providing additional reaction gas for the end fuel cell stack, thereby improving the dynamic response capability of the fuel cell multi-stack system when the load current changes.

[0065] Example 2

[0066] The flow chart of the gas back pressure control method of the gas back pressure structure of the fuel cell multi-stack system in Example 1 is as follows: Figure 2 As shown, the following steps are included:

[0067] S1 Before starting the fuel cell multi-stack system, set the operating time T of the fuel cell multi-stack system d For 15s, set the minimum single-chip voltage of the stack V limit is 0.3V, set the maximum liquid level H max The exhaust time T is 1 / 2 of the internal height of the gas-liquid separator 15. P Set to 3s;

[0068] S2 then starts the fuel cell multi-stack system. During the operation of the fuel cell multi-stack system, the operating time t is recorded, and the voltage signal of each stack is recorded in real time. When the voltage signal of any stack is less than or equal to the lowest single-chip voltage V limit When , the fourth solenoid valve 11 and the fifth solenoid valve 12 are opened for 1 second and then closed;

[0069] S3 determines whether the liquid level h of the gas-liquid separator 15 currently collected in real time is greater than or equal to the maximum liquid level H max If yes, proceed to the next step; if not, repeat step S3 until the collected liquid level height h of the gas-liquid separator 15 is greater than or equal to the maximum liquid level height H max ;

[0070] Alternatively, it is determined whether the pressure P currently collected in real time inside the gas-liquid separator 15 is greater than or equal to 0.8 times the pressure P currently collected in real time by the equalizing back pressure tank 6. d if not, repeat step S3 until the pressure P inside the gas-liquid separator 15 is greater than or equal to 0.8 times the pressure P of the current real-time acquisition of the gas back pressure tank 6 d ;

[0071] S4 opens the second normally closed solenoid valve 16 to exhaust and records the exhaust time. When the exhaust time is greater than or equal to the exhaust time T of the second normally closed solenoid valve 16, P When , the second normally closed solenoid valve 16 is closed;

[0072] S5 determines whether the current fuel cell multi-stack system operation duration t is greater than or equal to the preset operation time 15s: if so, shut down the fuel cell multi-stack system; if not, repeat steps S2-S5 until the operation duration t reaches the preset fuel cell multi-stack system operation time T d , thereby achieving uniform gas back pressure regulation; in this embodiment, the operating time of the fuel cell multi-stack system can be set according to demand.

[0073] Example 3

[0074] The method for controlling the gas back pressure of the gas back pressure structure of the fuel cell multi-stack system provided in this embodiment includes the following steps:

[0075] S1 Before starting the fuel cell multi-stack system, set the operating time T of the fuel cell multi-stack system d For 10s, set the minimum single-chip voltage of the stack V limit is 0.3V, set the maximum liquid level H max The exhaust time T is 1 / 3 of the internal height of the gas-liquid separator 15. P Set to 2s;

[0076] S2 then starts the fuel cell multi-stack system. During the operation of the fuel cell multi-stack system, the operating time t is recorded, and the voltage signal of each stack is recorded in real time. When the voltage signal of any stack is less than or equal to the lowest single-chip voltage V limit When the voltage is 0, the corresponding electromagnetic valves at the outlet of the stack are opened for exhaust, such as the fourth electromagnetic valve 11 and the fifth electromagnetic valve 12, and the two valves are closed after 1 second to increase the output voltage;

[0077] S3 determines whether the liquid level h of the gas-liquid separator 15 currently collected in real time is greater than or equal to the maximum liquid level H max If yes, proceed to the next step; if not, repeat step S3 until the collected liquid level height h of the gas-liquid separator 15 is greater than or equal to the maximum liquid level height H max ;

[0078] Alternatively, it is determined whether the pressure P currently collected in real time inside the gas-liquid separator 15 is greater than or equal to 0.6 times the pressure P currently collected in real time by the equalizing back pressure tank 6. d if not, repeat step S3 until the pressure P inside the gas-liquid separator 15 is greater than or equal to 0.8 times the pressure P of the current real-time acquisition of the gas back pressure tank 6 d ;

[0079] S4 opens the second normally closed solenoid valve 16 to exhaust and records the exhaust time. When the exhaust time is greater than or equal to 2s, closes the second normally closed solenoid valve 16;

[0080] S5 determines whether the operating duration t of the current fuel cell multi-stack system is greater than or equal to 10s: if so, shut down the fuel cell multi-stack system; if not, repeat steps S2-S5 until the operating duration t reaches 10s, thereby completing the gas back pressure adjustment.

[0081] In other embodiments, the parallel-connected fuel cell stacks in the fuel cell stack system in the gas back pressure equalization structure of the fuel cell multi-stack system may include 3, 4 or more, and a corresponding solenoid valve for turning hydrogen on and off is provided at the inlet of each fuel cell stack, and a corresponding solenoid valve for exhaust and drainage is provided at the outlet of each fuel cell stack. Apart from this, the other structures are roughly the same as those in the aforementioned embodiment 1, and the gas back pressure equalization method of the gas back pressure equalization structure of the fuel cell multi-stack system is also roughly the same.

[0082] In other preferred embodiments, it is also possible to determine in step S5 whether the real-time pressure of the gas-liquid separator 15 is less than or equal to the preset minimum exhaust pressure. If so, the next step is executed, i.e., closing the second normally closed solenoid valve 16, stopping the exhaust gas discharge, and determining whether the operating time of the fuel cell multi-stack system meets the preset time; if not, the determination of step S5 is repeated until the real-time pressure of the gas-liquid separator 15 is less than or equal to the preset minimum exhaust pressure, which must be greater than atmospheric pressure.

[0083] In summary, the present invention controls the gas equalization back pressure of the fuel cell multi-stack system by connecting the gas equalization buffer tank 6 at the end of the fuel cell system and proposing a corresponding control strategy, thereby increasing the system back pressure during the operation of the fuel cell multi-stack system, thereby increasing the system output voltage and further improving the dynamic response capability of the system under variable load.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fuel cell multi-stack system with a gas back pressure equalization structure, characterized in that: It includes a hydrogen gas source (1), a fuel cell system, a gas back pressure tank (6) and a gas-liquid separator (15), wherein: The hydrogen source (1) is used to input hydrogen into the multi-stack system and the equalizing gas back pressure tank (6) respectively; the outlet end of the multi-stack system is provided with a normally closed pulse exhaust valve, and the normally closed pulse exhaust valve can perform pulse exhaust, so that the impurity gas collected inside the multi-stack system enters the gas-liquid separator (15) for gas-liquid separation; the gas-liquid separator (15) is provided with a first outlet, and a second normally closed solenoid valve (16) is provided at the first outlet, which is used to discharge the impurity gas and liquid water after gas-liquid separation to the outside; when the load current changes and the hydrogen flow in the hydrogen source (1) lags and has not yet reached the end of the multi-stack system, the hydrogen in the equalizing gas back pressure tank (6) can enter the multi-stack system under the action of the pressure difference, providing reaction gas for the multi-stack system.

2. A fuel cell multi-stack system with a gas back pressure equalization structure according to claim 1, characterized in that: The multi-stack system comprises at least two parallel-connected stacks, and a normally open solenoid valve is provided between each stack and the hydrogen gas source (1), and the normally open solenoid valve is used to control the on-off of hydrogen.

3. A fuel cell multi-stack system with a gas back pressure equalization structure according to claim 2, characterized in that: The normally closed pulse exhaust valve is provided at the outlet of each fuel cell stack to control the pulse exhaust of each fuel cell stack respectively.

4. The fuel cell multi-stack system with a gas back pressure equalization structure according to claim 1, characterized in that: The multi-stack system also includes an external controller, and a first pressure sensor (7) is provided on the gas-liquid separator (15) for recording and transmitting the internal pressure signal thereof to the external controller; a second pressure sensor (13) is provided on the gas-equalizing back-pressure tank (6) for recording and transmitting the internal pressure signal thereof to the external controller; when the pressure in the gas-liquid separator (15) is greater than a preset multiple of the pressure in the gas-equalizing back-pressure tank (6), the external controller is used to control the second normally closed solenoid valve (16) to open, so as to discharge the impurity gas and liquid water of the multi-stack system to the outside.

5. The fuel cell multi-stack system with a gas back pressure equalization structure according to claim 4, characterized in that: The gas-liquid separator (15) is provided with a liquid level sensor (14) for recording and transmitting the liquid level inside the gas-liquid separator to an external controller. When the liquid level inside the gas-liquid separator (15) is greater than a preset maximum liquid level, the external controller can control the second normally closed solenoid valve (16) to open, so as to discharge the separated impurity gas and liquid water to the outside.

6. The fuel cell multi-stack system with a gas back pressure equalization structure according to claim 4, characterized in that: The multi-stack system is provided with a voltage patrol meter for reading and outputting the voltage signal of each stack in the multi-stack system to the external controller. The external controller determines and controls the opening and closing of the normally closed pulse exhaust valve based on the voltage signal.

7. The fuel cell multi-stack system with a gas back pressure equalization structure according to claim 1, characterized in that: The gas-liquid separator (15) is also provided with a second outlet, which is connected to the gas equalization back pressure tank (6) via a first normally closed solenoid valve (8). When the multi-stack system is started or stopped, the first normally closed solenoid valve (8) is opened to purge the multi-stack system.

8. A control method for a fuel cell multi-stack system with a gas back pressure equalization structure according to any one of claims 1 to 7, characterized in that: The control method comprises the following steps: S1 acquires in real time the liquid level of the gas-liquid separator (15), the operation time of the fuel cell system, the pressure of the gas-liquid separator (15), the pressure of the gas equalization back pressure tank (6), the exhaust time of the second normally closed solenoid valve (16), and the voltage signal of each fuel cell in the fuel cell system when the multi-fuel cell system is running; S2 determines whether any of the voltage signals is less than the preset minimum single-chip voltage: if so, proceed to the next step; if not, repeat the determination of step S2; S3 opens the pulse exhaust valve corresponding to the stack whose voltage signal is less than the minimum single-chip voltage, continues exhausting for a first preset time, and then closes; S4 determines whether the liquid level is greater than or equal to a preset maximum liquid level: if so, proceed to the next step; if not, repeat the determination of step S4; Or, determine whether the pressure of the gas-liquid separator (15) is greater than or equal to a preset multiple of the pressure of the gas equalizing back pressure tank (6): if so, proceed to the next step; if not, repeat the determination of step S4; S5 opens the second normally closed solenoid valve (16) to exhaust, and records the exhaust time, and when the exhaust time is greater than or equal to the preset exhaust time, closes the second normally closed solenoid valve (16); S6 determines whether the operating time is greater than or equal to the preset operating time: if so, the fuel cell multi-stack system is controlled to stop operating; if not, steps S1-S6 are repeated until the multi-stack system stops operating.

9. The control method of a fuel cell multi-stack system with a gas back pressure equalization structure according to claim 8, characterized in that: In step S5, the preset multiple is 0.5 times to 0.8 times.

10. The control method of a fuel cell multi-stack system with a gas back pressure equalization structure according to claim 8, characterized in that: The minimum single-chip voltage is 0.3V; the maximum liquid level is At height.

11. The control method of a fuel cell multi-stack system with a gas back pressure equalization structure according to claim 8, characterized in that: The first preset time is 1s, and the exhaust time of the exhaust gas is 2s-4s.

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