Fuel cell system and humidification control method thereof

Abstract

The invention provides a fuel cell system and a humidification control method thereof. The fuel cell system comprises an electric pile, a humidifier and an air pipeline, wherein the air pipeline comprises a dry air inlet header pipe, an air pile inlet pipeline, a dry air bypass, an air return pipeline, a backpressure pipeline and a bypass pipeline; one end of the air return pipeline is connected with an air outlet of the galvanic pile, and the other end is connected with a return air inlet of the humidifier; one end of the backpressure pipeline is connected with a backflow air outlet of the humidifier, and the other end is communicated with external atmosphere; two ends of the bypass pipeline are connected with an air return pipeline and a backpressure pipeline; a first throttle valve is arranged in the dry air inlet main pipe; a second throttle valve is arranged in the dry air bypass; a third throttle valve is arranged in the air return pipeline; and a fourth throttle valve is arranged in the bypass pipeline. In this way, when humidification is needed, the opening degree of the first throttle valve and the third throttle valve can be increased, the opening degree of the second throttle valve and the fourth throttle valve can be reduced, the water supplementing requirement of the humidifier is lowered, and the problems in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and more specifically to a fuel cell system and its humidification control method. Background Technology

[0002] In fuel cell systems, the humidification control of the air circuit can directly affect the working performance of the stack. As the core component of humidification control, the humidifier's role is to provide suitable humidity for the air entering the stack, ensuring the stack's reaction efficiency and stability.

[0003] like Figure 1 The diagram shows the connection structure of the fuel cell stack 10 and the humidifier 20 in a current fuel cell system. In this system, the humidifier 20 is equipped with a humidification throttle valve 21 and a drying throttle valve 22. Humidity control can be achieved by opening and closing these throttle valves. Specifically, when humidification is needed, the opening of the humidification throttle valve 21 is increased and the opening of the drying throttle valve 22 is decreased. This allows more air to flow through the humidifier 20 and be humidified before flowing into the fuel cell stack 10. When humidity needs to be reduced, the opening of the humidification throttle valve 21 is decreased and the opening of the drying throttle valve 22 is increased. This allows more air to flow directly into the fuel cell stack 10 through the drying throttle valve 22. Thus, the humidity of the air flowing into the fuel cell stack 10 is adjusted by regulating the opening of the humidification throttle valve 21 and the drying throttle valve 22.

[0004] However, in current fuel cell systems, when humidification is required, the opening of the humidification throttle valve 21 is increased, allowing more air to flow through the humidifier 20 for humidification. As a result, water in the humidifier 20 is constantly lost, requiring frequent water replenishment, which is inconvenient to operate. Summary of the Invention

[0005] In view of the deficiencies in the existing technology, the purpose of this invention is to provide a fuel cell system and its humidification control method, which aims to solve the problems in the related technology to a certain extent.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This application provides a fuel cell system including a stack, a humidifier, and an air pipeline, wherein the air pipeline includes a dry air intake main pipe, an air inlet pipe, a dry air bypass, an air return pipe, a back pressure pipe, and a bypass pipe.

[0008] One end of the dry air intake manifold is connected to an air source, and the other end is connected to the dry air inlet of the humidifier;

[0009] One end of the air inlet pipe is connected to the humidified air outlet of the humidifier, and the other end is connected to the air inlet of the fuel cell stack.

[0010] One end of the dry air bypass is connected to the dry air inlet manifold, and the other end is connected to the air inlet stack pipeline;

[0011] One end of the air return pipeline is connected to the air outlet of the stack, and the other end is connected to the return air inlet of the humidifier;

[0012] One end of the back pressure pipeline is connected to the return air outlet of the humidifier, and the other end is connected to the external atmosphere;

[0013] Both ends of the bypass pipeline are connected to the air return pipeline and the back pressure pipeline, respectively;

[0014] The first throttle valve is arranged in the dry air inlet manifold;

[0015] The second throttle valve is arranged in the dry air bypass;

[0016] The third throttle valve is arranged in the air return pipeline;

[0017] The fourth throttle valve is arranged in the bypass pipeline;

[0018] The fifth throttle valve is arranged in the back pressure pipeline.

[0019] Preferably, the first one-way valve is arranged in the air inlet stack pipeline.

[0020] Preferably, the connection point of the dry air bypass and the air inlet stack pipeline is arranged between the first one-way valve and the air inlet of the stack.

[0021] Preferably, the connection point of the dry air bypass and the dry air inlet manifold is arranged upstream of the first throttle valve.

[0022] Preferably, the second one-way valve is arranged in the back pressure pipeline; and,

[0023] The connection point of the bypass pipeline and the back pressure pipeline is arranged between the second one-way valve and the fifth throttle valve.

[0024] Preferably, the connection point of the bypass pipeline and the air return pipeline is arranged between the third throttle valve and the air outlet of the stack.

[0025] Preferably, the air source comprises an air compressor and an intercooler.

[0026] The application also provides a humidification control method based on the fuel cell system provided by the application, which comprises:

[0027] In the case that the fifth throttle is kept open, it is judged whether the air entering the stack needs to be humidified;

[0028] If the air entering the stack does not need to be humidified, the first and third throttles are closed and the second and fourth throttles are opened; or,

[0029] If the air entering the stack needs to be humidified, the opening degrees of the first and third throttles are increased and the opening degrees of the second and fourth throttles are simultaneously decreased by using a PID control algorithm.

[0030] Preferably, the judgment of whether the air entering the stack needs to be humidified specifically comprises:

[0031] The actual humidity of the air entering the stack at the air inlet of the stack is obtained;

[0032] The target humidity of the air entering the stack is determined according to the current actual working condition of the stack;

[0033] The actual humidity of the air entering the stack is compared with the target humidity to judge whether the air entering the stack needs to be humidified, wherein, if the actual humidity of the air entering the stack is less than the target humidity, it is judged that the air entering the stack needs to be humidified, or if the actual humidity of the air entering the stack is greater than or equal to the target humidity, it is judged that the air entering the stack does not need to be humidified.

[0034] Preferably, the judgment of whether the air entering the stack needs to be humidified specifically comprises:

[0035] The actual humidity of the air entering the stack at the air inlet of the stack is obtained;

[0036] The target humidity of the air entering the stack is determined according to the current actual working condition of the stack;

[0037] The humidity hysteresis interval is determined according to the target humidity, wherein the upper limit value and the lower limit value of the humidity hysteresis interval are determined according to the target humidity;

[0038] The actual humidity of the air entering the stack is compared with the upper limit value and the lower limit value of the humidity hysteresis interval to judge whether the air entering the stack needs to be humidified, wherein, if the actual humidity of the air entering the stack is less than the lower limit value, it is judged that the air entering the stack needs to be humidified, or if the actual humidity of the air entering the stack is greater than the upper limit value, it is judged that the air entering the stack does not need to be humidified.

[0039] On the basis of the above technical solutions, compared with the prior art, the application has the following advantages:

[0040] The fuel cell system provided by the embodiment of the application comprises a stack, a humidifier and an air pipeline, the air pipeline comprises a dry air inlet manifold, an air inlet stack pipeline, a dry air bypass, an air backflow pipeline, a back pressure pipeline and a bypass pipeline; one end of the dry air inlet manifold is connected with an air source, and the other end is connected with a dry air inlet of the humidifier; one end of the air inlet stack pipeline is connected with a wet air outlet of the humidifier, and the other end is connected with an air inlet of the stack; one end of the dry air bypass is connected with the dry air inlet manifold, and the other end is connected with the air inlet stack pipeline; one end of the air backflow pipeline is connected with an air outlet of the stack, and the other end is connected with a backflow air inlet of the humidifier; one end of the back pressure pipeline is connected with a backflow air outlet of the humidifier, and the other end is communicated with an external atmosphere; two ends of the bypass pipeline are respectively connected with the air backflow pipeline and the back pressure pipeline; a first throttle valve is arranged in the dry air inlet manifold; a second throttle valve is arranged in the dry air bypass; a third throttle valve is arranged in the air backflow pipeline; a fourth throttle valve is arranged in the bypass pipeline; and a fifth throttle valve is arranged in the back pressure pipeline. In this way, when humidification is needed, the opening degrees of the first throttle valve and the third throttle valve can be increased, and the opening degrees of the second throttle valve and the fourth throttle valve can be reduced, so that the backflow air carrying the reaction generated water can be backflowed to the humidifier through the air backflow pipeline, thereby humidifying the dry air flowing into the humidifier, and further reducing the water supplement demand of the humidifier itself, and solving the problems in the prior art. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 A specific structure schematic diagram of the fuel cell system in the prior art;

[0042] Figure 2 A structure schematic diagram of the fuel cell system provided by the application;

[0043] Figure 3 A flow schematic diagram of the humidification control method of the fuel cell system provided by the application. DETAILED DESCRIPTION

[0044] The embodiments of the application will be further described below in conjunction with the accompanying drawings.

[0045] The exemplary embodiments will be described in detail hereinbelow with reference to the drawings. In the following description, the same numbers in different drawings represent the same or similar elements unless otherwise represented. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present disclosure. Instead, they only represent examples of devices and methods consistent with some aspects of the present disclosure, as detailed in the appended claims.

[0046] In the description of the present application, it is also necessary to explain that, unless otherwise explicitly specified and limited, the terms "set", "install", "connect", "connect" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or equipment. Without more limitation, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0047] As described previously, Figure 1 In the fuel cell system shown, when humidification is needed, the opening of the humidification throttle valve 21 is increased, so that more air flows through the humidifier 20 for humidification through the humidification throttle valve 21, so that the water in the humidifier 20 will be continuously lost, and frequent water replenishment is needed, which is relatively inconvenient to operate.

[0048] Based on this, the embodiments of the present application provide a fuel cell system and a humidification control method thereof, which can be used to solve the problems in the prior art. In order to facilitate understanding, the structure of the fuel cell system provided by the embodiments of the present application can be described first.

[0049] As Figure 2 The structure of the fuel cell system provided by the embodiments of the present application is shown in the schematic diagram, which includes a stack 40, a humidifier 50 and an air pipeline. Among them, the stack 40 is used as the core power generation unit of the fuel cell, which is used to convert the chemical energy of hydrogen and oxygen in air into electrical energy, and its normal operation depends on stable reaction gas supply and appropriate membrane wetting state. In actual application, the stack 40 can usually be stacked by a plurality of fuel cell monomers in series or parallel, which includes membrane electrode, bipolar plate, end plate, sealing ring and other components.

[0050] The humidifier 50 is a gas-gas type humidification device, which includes a wet transmission channel array composed of hydrophilic membrane material, which can extract water vapor from the backflow air and transfer it to the stack dry air, so as to realize the humidification function. The air pipeline is a gas transmission network, which integrates a variety of functional branches to support different working modes.

[0051] The air pipeline structure can be described as follows. The air pipeline includes a dry air inlet main pipe 31, an air inlet stack pipeline 32, a dry air bypass 33, an air return pipeline 34, a back pressure pipeline 35, and a bypass pipeline 36. The pipelines of the air pipeline can be made of corrosion-resistant engineering plastics, and the inner diameter thereof can be 8-50 mm. The specific size can be determined according to the rated power of the fuel cell system.

[0052] One end of the dry air inlet main pipe 31 is connected to an air source, and the other end is connected to a dry air inlet of the humidifier 50. Therefore, the dry air in the air source can be guided to the humidifier 20 through the dry air inlet main pipe 31.

[0053] One end of the air inlet stack pipeline 32 is connected to a wet air outlet of the humidifier 50, and the other end is connected to an air inlet of the stack 40. Therefore, the air humidified or mixed by the humidifier 50 can be delivered to the air inlet of the stack 40 through the air inlet stack pipeline 32.

[0054] The dry air bypass 33 is an auxiliary path that can bypass the humidifier 50. One end of the dry air bypass 33 is connected to the dry air inlet main pipe 31, and the other end is connected to the air inlet stack pipeline 32. Therefore, part or all of the dry air can be directly introduced into the air inlet stack pipeline 32 without passing through the humidifier 50 through the dry air bypass 33.

[0055] One end of the air return pipeline 34 is connected to an air outlet of the stack 40, and the other end is connected to a return air inlet of the humidifier 50. Therefore, the air after the redox reaction in the stack 40 (referred to as return air) can be introduced into the return air inlet of the humidifier 50 through the air return pipeline 34. Since the product of the redox reaction of hydrogen and oxygen in the stack 40 is water, the return air carries a certain amount of water (in the form of water vapor or small water droplets). After the return air is introduced into the return air inlet of the humidifier 50, the water carried by the return air can be absorbed by the humidifying channel array of the humidifier 50 and used for humidifying the dry air. Therefore, the humidifier 50 can be watered through the air return pipeline 34, and the dry air can be self-humidified.

[0056] One end of the back pressure pipeline 35 is connected to a return air outlet of the humidifier 50, and the other end is connected to the external atmosphere. Therefore, the return air outlet of the humidifier 20 can be connected to the external atmosphere to discharge the excess gas that cannot be recycled to the external atmosphere and maintain the internal pressure of the fuel cell system stable. The end of the back pressure pipeline 35 (i.e., the end close to the external atmosphere) can be configured with a soundproof structure or a waterproof and breathable membrane to prevent external pollutants from entering.

[0057] The bypass pipe 36 is connected with the air return pipe 34 and the back pressure pipe 35 at two ends, and thus serves as a bypass channel for the air return pipe 34 and the back pressure pipe 35. In this way, part of the return air can be led out of the system in advance under certain conditions, so as to avoid overloading of the humidifier 20 at the front end and ensure the humidification efficiency.

[0058] In addition, each throttle valve is arranged at a key node of the pipeline as a key control element. For example, the first throttle valve 311 is arranged in the dry air inlet pipe 31 to adjust the size of the main air flow entering the humidifier 20; the second throttle valve 331 is arranged in the dry air bypass pipe 33 to control the proportion of the bypass air; the third throttle valve 341 is arranged in the air return pipe 34 to adjust the flow of the return air; the fourth throttle valve 361 is arranged in the bypass pipe 36 to control the branch of the return path; and the fifth throttle valve 351 is arranged in the back pressure pipe 35 to actively adjust the exhaust back pressure and thus affect the pressure gradient distribution of the entire air system.

[0059] It should be further explained that another important function of the bypass pipe 36 is to protect the humidifier 50. Specifically, if the bypass pipe 36 is not arranged, the air discharged from the stack 40 will continue to flow back into the humidifier 50 through the air return pipe 34 regardless of whether the air entering the stack needs to be humidified, which will cause the humidifier 20 to be in a high-temperature, high-pressure, and high-humidity environment for a long time. The continuous effect of such an environment will directly affect the service life of the hydrophilic membrane material in the humidifier 50. In the present application, when the air does not need to be humidified, the third throttle valve 341 is closed to cut off the air return pipe 34, and the fourth throttle valve 361 is opened to make the bypass pipe 36 conductive, so that the return air can be directly introduced into the back pressure pipe 35 and discharged into the atmosphere. In this way, the return air can be prevented from flowing into the humidifier 50 without humidification, so as to avoid the humidifier 50 being in a high-temperature, high-pressure, and high-humidity environment for a long time, and the service life of the humidifier 50 can be improved.

[0060] Therefore, the connection relationship between the above-mentioned components constitutes a closed-loop air management architecture with multiple regulation capabilities. For example, when the fuel cell system detects that the air entering the stack does not need to be humidified, the first throttle valve 311 and the third throttle valve 341 are closed, and the second throttle valve 331 and the fourth throttle valve 361 are opened, so that the dry air is directly supplied to the stack 40 through the bypass, and the return air is directly discharged through the bypass pipe 36, thereby avoiding ineffective humidification and protecting the humidifier 50; conversely, when humidification is needed, the opening degrees of the first throttle valve 311 and the third throttle valve 341 are increased, and the opening degrees of the second throttle valve 331 and the fourth throttle valve 361 are decreased, so that more air passes through the humidifier 50 to complete humidification.

[0061] The fuel cell system provided by the embodiment of the present application comprises a stack 40, a humidifier 50, and an air pipeline, which comprises a dry air inlet main pipe 31, an air inlet stack pipeline 32, a dry air bypass 33, an air backflow pipeline 34, a back pressure pipeline 35, and a bypass pipeline 36; one end of the dry air inlet main pipe 31 is connected to an air source, and the other end is connected to a dry air inlet of the humidifier 50; one end of the air inlet stack pipeline 32 is connected to a wet air outlet of the humidifier 50, and the other end is connected to an air inlet of the stack 40; one end of the dry air bypass 33 is connected to the dry air inlet main pipe 31, and the other end is connected to the air inlet stack pipeline 32; one end of the air backflow pipeline 34 is connected to an air outlet of the stack 40, and the other end is connected to a backflow air inlet of the humidifier 50; one end of the back pressure pipeline 35 is connected to a backflow air outlet of the humidifier 50, and the other end is connected to an external atmosphere; two ends of the bypass pipeline 36 are respectively connected to the air backflow pipeline 34 and the back pressure pipeline 35; the dry air inlet main pipe 31 is provided with a first throttle valve 311; the dry air bypass 33 is provided with a second throttle valve 331; the air backflow pipeline 34 is provided with a third throttle valve 341; the bypass pipeline 36 is provided with a fourth throttle valve 361; and the back pressure pipeline 35 is provided with a fifth throttle valve 351. In this way, when humidification is needed, the opening degrees of the first throttle valve 311 and the third throttle valve 341 can be increased, and the opening degrees of the second throttle valve 331 and the fourth throttle valve 361 can be reduced. In this way, the backflow air carrying the reaction-generated water can flow back to the humidifier 50 through the air backflow pipeline 34, so as to humidify the dry air flowing into the humidifier 50, and thus the water supplement demand of the humidifier 50 itself is reduced, and the problem of the prior art is solved.

[0062] It needs to be further explained that the air inlet stack pipeline 32 is provided with a first one-way valve 321, so that the gas flow direction in the air inlet stack pipeline 32 can be controlled through the first one-way valve 321, and it is ensured that the humidified wet air after the humidifier 50 can only flow to the stack 40 in one direction, so as to prevent the air in the stack 40 from flowing into the humidifier from the side of the stack 40, so as to ensure the stability and reliability of the system operation. The one-way valve (including the first one-way valve 321 and other one-way valves) is a valve device that only allows the medium to flow in a single direction, and its structure can adopt common forms such as spring type, gravity type, or diaphragm type.

[0063] Of course, considering that the dry air bypass 33 is also connected to the air inlet pipe 32, in order to avoid the dry air in the dry air bypass 33 from flowing into the humidifier 50 in reverse, the connection point of the dry air bypass 33 and the air inlet pipe 32 can be arranged between the first one-way valve 321 and the air inlet of the stack 40, which limits the dry air flowing out of the dry air bypass 33, and generally only flows to the air inlet of the stack 40, preventing it from flowing into the humidifier 50 in reverse, affecting the pressure balance in the humidifier 50.

[0064] In addition, the connection point of the dry air bypass 33 and the dry air inlet manifold 31 can be arranged upstream of the first throttle valve 311, so that the dry air bypass 33 and the wet path provided with the humidifier 50 form a parallel relationship, facilitating independent control of the flow of the two.

[0065] The back pressure pipe 35 is provided with a second one-way valve 352, and the connection point of the bypass pipe 36 and the back pressure pipe 35 is arranged between the second one-way valve 352 and the fifth throttle valve 351. In this way, on the one hand, the second one-way valve 352 can prevent external air from flowing into the fuel cell system due to pressure difference during shutdown or low load of the fuel cell system; on the other hand, due to the arrangement position of the connection point of the bypass pipe 36 and the back pressure pipe 35, that is, between the second one-way valve 352 and the fifth throttle valve 351, the second one-way valve 352 can also prevent the backflow air in the bypass pipe 36 from flowing into the humidifier 50 in reverse through the back pressure pipe 35.

[0066] The connection point of the bypass pipe 36 and the air backflow pipe 34 is arranged between the third throttle valve 341 and the air outlet of the stack 40, so that the backflow air is branched upstream of the third throttle valve 341, and the bypass pipe 36 is used to guide part of the backflow air that does not pass through the third throttle valve 341 to the back pressure pipe 35, thereby forming a pressure regulation branch independent of the main backflow path, avoiding the accumulation of backflow air near the third throttle valve 341.

[0067] The air source includes an air compressor and an intercooler. During normal operation of the fuel cell system, the air compressor pressurizes the air and blows it to the intercooler for cooling. The cooled air flows into the dry air inlet manifold 31.

[0068] As described above, based on the fuel cell system provided by the embodiment of the present application, the present application can further provide a humidification control method thereof, as shown in the following. Figure 3 The specific flowchart of the method is shown in the figure, and the method comprises the following steps:

[0069] S61: In the case that the fifth throttle is kept open, it is judged whether the air entering the stack needs to be humidified. If the air does not need to be humidified, step S62 is executed, and if the air needs to be humidified, step S63 is executed.

[0070] S62: The first and third throttles are closed, and the second and fourth throttles are opened.

[0071] S63: The opening degrees of the first and third throttles are increased by a PID control algorithm, and the opening degrees of the second and fourth throttles are simultaneously decreased.

[0072] Here, the steps S61-S63 can be uniformly described.

[0073] The fifth throttle kept open means that the fifth throttle 351 is in a fixed opening degree or a fully open state, does not participate in dynamic adjustment, and is only used to guarantee the flow capacity of the back pressure pipeline 35 to prevent the abnormal increase of the pressure in the fuel cell system due to the blockage of the back pressure pipeline 35.

[0074] The judgment of whether the air entering the stack needs to be humidified is the prerequisite for the decision of the whole control strategy. The implementation manner can be that the actual humidity of the air entering the stack at the air inlet of the stack 40 is obtained, for example, a humidity sensor can be arranged at the air inlet of the stack 40, so that the actual humidity of the air entering the stack at the air inlet of the stack 40 is obtained through the humidity sensor. Then, the target humidity of the air entering the stack is determined according to the current actual working condition of the stack 40. In actual application, the size of the target humidity is associated with the current actual working condition of the stack 40. Generally, the greater the power of the stack 40, the greater the humidity (that is, the target humidity) required, so the target humidity can be calculated according to the current actual working condition of the stack 40. For example, the relationship curve between the target humidity and the stack power can be obtained through experimental test in advance, and then the target humidity is calculated through the relationship curve. After obtaining the target humidity, whether the air entering the stack needs to be humidified can be judged by comparing the size of the actual humidity of the air entering the stack with the target humidity. If the actual humidity of the air entering the stack is less than the target humidity, it is judged that the air needs to be humidified, or if the actual humidity of the air entering the stack is greater than or equal to the target humidity, it is judged that the air does not need to be humidified.

[0075] In view of directly comparing the actual humidity of the air entering the stack with the target humidity to determine whether humidification is needed, frequent switching is prone to occur, for example, if the actual humidity of the air entering the stack is slightly less than the target humidity and slightly less than the target humidity, it is determined that humidification is needed, but after a short period of humidification, the actual humidity of the air entering the stack can be slightly greater than the target humidity, at which time it is necessary to switch to not needing humidification, and after a short period of time, it can be necessary to switch to needing humidification, thereby causing frequent switching. To solve this problem, the method provided in the embodiments of the present application can further determine a humidity hysteresis interval according to the target humidity after obtaining the actual humidity of the air entering the stack and the target humidity, the upper limit value and the lower limit value of the humidity hysteresis interval being determined according to the target humidity, for example, the upper limit value can be the target humidity multiplied by an amplification factor (which can be 1.01-1.1), and the lower limit value can be the target humidity multiplied by a discount factor (which can be 0.9-0.99), thereby calculating the upper limit value and the lower limit value of the humidity hysteresis interval from the target humidity,

[0076] The actual humidity of the air entering the stack can then be compared with the upper limit value and the lower limit value of the humidity hysteresis interval to determine whether the air entering the stack needs to be humidified, wherein if the actual humidity of the air entering the stack is less than the lower limit value, it is determined that humidification is needed, or if the actual humidity of the air entering the stack is greater than the upper limit value, it is determined that humidification is not needed. This method replaces the target humidity in the previous method with the upper limit value and the lower limit value of the humidity hysteresis interval, which can effectively avoid frequent switching and improve the stability of the fuel cell system.

[0077] If it is determined that humidification is not needed through step S61, the first and third throttle valves can be closed and the second and fourth throttle valves can be opened, so that on the one hand, dry air flows directly into the stack through the dry air bypass, and on the other hand, the backflow air flowing out of the stack does not flow into the humidifier but flows directly into the back pressure pipeline through the bypass pipeline and then into the external atmosphere, thereby avoiding the backflow air flowing into the humidifier when humidification is not needed, which affects the service life of the humidifier.

[0078] Of course, if step S61 determines that humidification is needed, the opening degree of the first and third throttle valves can be increased and the opening degree of the second and fourth throttle valves can be simultaneously decreased through a PID control algorithm, so that the air flow into the humidifier and the backflow air flow into the humidifier are gradually increased, and the air flow through the dry air bypass and the flow directly into the back pressure pipeline through the bypass pipeline are simultaneously decreased, so as to gradually increase the humidity. In the control mode of the PID control algorithm, a plurality of control cycles can be included, and in each control cycle, the actual opening degree is compared with the target opening degree, and then the adjustment direction of the valve opening degree is controlled.

[0079] The present application is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the principles of the present application, and such improvements and modifications are deemed to be within the scope of the present application. The contents not described in detail in the specification are the prior art known to those skilled in the art.

Claims

1. A fuel cell system, characterized in that, It includes a fuel cell stack (40), a humidifier (50), and air piping, wherein the air piping includes a dry air intake manifold (31), an air inlet pipe (32), a dry air bypass (33), an air return pipe (34), a back pressure pipe (35), and a bypass pipe (36). One end of the dry air intake manifold (31) is connected to an air source, and the other end is connected to the dry air inlet of the humidifier (50); One end of the air inlet pipe (32) is connected to the humid air outlet of the humidifier (50), and the other end is connected to the air inlet of the fuel cell stack (40); One end of the dry air bypass (33) is connected to the dry air intake manifold (31), and the other end is connected to the air inlet pipe (32). One end of the air return pipe (34) is connected to the air outlet of the fuel cell stack (40), and the other end is connected to the return air inlet of the humidifier (50); One end of the back pressure pipeline (35) is connected to the return air outlet of the humidifier (50), and the other end is connected to the outside atmosphere; The two ends of the bypass pipe (36) are respectively connected to the air return pipe (34) and the back pressure pipe (35). The dry air intake manifold (31) is provided with a first throttle valve (311); The dry air bypass (33) is provided with a second throttle valve (331); The air return pipe (34) is provided with a third throttle valve (341); The bypass pipe (36) is provided with a fourth throttle valve (361); The back pressure line (35) is equipped with a fifth throttle valve (351).

2. The fuel cell system according to claim 1, characterized in that, The air inlet pipe (32) is equipped with a first check valve (321).

3. The fuel cell system according to claim 2, characterized in that, The connection point between the dry air bypass (33) and the air inlet pipe (32) is located between the first one-way valve (321) and the air inlet of the fuel cell stack (40).

4. The fuel cell system according to claim 1, characterized in that, The connection point between the dry air bypass (33) and the dry air intake manifold (31) is located upstream of the first throttle valve (311).

5. The fuel cell system according to claim 1, characterized in that, The back pressure line (35) is equipped with a second check valve (352); and, The connection point between the bypass pipe (36) and the back pressure pipe (35) is located between the second one-way valve (352) and the fifth throttle valve (351).

6. The fuel cell system according to claim 5, characterized in that, The connection point between the bypass pipe (36) and the air return pipe (34) is located between the third throttle valve (341) and the air outlet of the fuel cell stack (40).

7. The fuel cell system according to claim 1, characterized in that, The air source includes an air compressor and an intercooler.

8. A humidification control method for a fuel cell system according to any one of claims 1 to 7, characterized in that, include: With the fifth throttle valve open, determine whether it is necessary to humidify the incoming air; If humidification is not required, close the first and third throttle valves and open the second and fourth throttle valves; or, If humidification is required, the opening of the first and third throttle valves is increased through a PID control algorithm, while the opening of the second and fourth throttle valves is decreased simultaneously.

9. The fuel cell system according to claim 8, characterized in that, Determining whether humidification of the incoming air is necessary includes: Obtain the actual humidity of the incoming air at the air inlet of the fuel cell stack (40); The target humidity of the incoming air is determined based on the current actual operating conditions of the fuel cell stack (40); By comparing the actual humidity of the incoming air with the target humidity, it is determined whether the incoming air needs to be humidified. If the actual humidity of the incoming air is less than the target humidity, it is determined that humidification is needed; if the actual humidity of the incoming air is greater than or equal to the target humidity, it is determined that humidification is not needed.

10. The fuel cell system according to claim 8, characterized in that, Determining whether humidification of the incoming air is necessary includes: Obtain the actual humidity of the incoming air at the air inlet of the fuel cell stack (40); The target humidity of the incoming air is determined based on the current actual operating conditions of the fuel cell stack (40); A humidity hysteresis interval is determined based on the target humidity, wherein the upper and lower limits of the humidity hysteresis interval are determined based on the target humidity; The actual humidity of the incoming air is compared with the upper and lower limits of the humidity hysteresis range to determine whether humidification of the incoming air is required. If the actual humidity of the incoming air is less than the lower limit, humidification is required; if the actual humidity of the incoming air is greater than the upper limit, humidification is not required.

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