Fuel cell system and control method and control device thereof

Abstract

The invention relates to a fuel cell system and a control method and device thereof.The fuel cell system comprises a fuel cell, a first cooling loop and a second cooling loop, and the first cooling loop and the second cooling loop are used for conducting temperature adjustment on the fuel cell. When the voltage of the fuel cell is smaller than or equal to a first preset value, a fuel cell direct-current converter in the first cooling loop is controlled to enter an active discharging mode; on the basis that the voltage of the fuel cell is larger than a second preset value, the fuel cell is controlled to conduct active discharging through a fuel cell direct-current converter, and the second preset value is smaller than the first preset value; based on the fact that the voltage of the fuel cell is smaller than or equal to the second preset value, the fuel cell is controlled to discharge through a heat preservation device in the second cooling loop, and the heat preservation device is controlled to store heat generated by discharging of the heat preservation device. The fuel cell system can be quickly started at low temperature, and residual hydrogen can be thoroughly discharged.

Description

Technical Field

[0001] The present application relates to the field of fuel cell technology, and in particular to a fuel cell system and a control method and a control device thereof. Background Art

[0002] When the fuel cell is shut down, it is necessary to purge the inside of the fuel cell to control the water content of the fuel cell and prevent the water from freezing and blocking the fuel cell reaction channel, thereby improving the success rate of the next low-temperature cold start of the fuel cell. By shutting down and purging and coordinating low-temperature start control strategies (such as active heating), the fuel cell system can achieve a higher success rate of startup, but there is a disadvantage of long low-temperature startup time.

[0003] In the related art, the waste heat of the fuel cell stack can be recovered through the cooling system and stored in the heat preservation device, so that the heat preservation device can be used to keep the stack warm for the next low-temperature cold start. This solution can solve the disadvantage of long low-temperature start time, but it lacks a solution to solve the problem of residual hydrogen discharge in the stack. Even if it is combined with relevant residual hydrogen discharge strategies, such as load discharge through the fuel cell DC converter, there are still disadvantages such as incomplete discharge and high cost, which is not conducive to extending the battery life. Summary of the invention

[0004] In view of the above, it is necessary to provide a fuel cell system and its control method and control device, which can use the electrical energy discharged from the residual hydrogen to heat and keep the coolant in the cooling system when the fuel cell system is shut down, so as to achieve rapid low-temperature start-up of the fuel cell system and completely discharge the residual hydrogen.

[0005] The first aspect of the present application provides a control method for a fuel cell system, the fuel cell system comprising a fuel cell, a first cooling circuit and a second cooling circuit for regulating the temperature of the fuel cell, the method comprising: when the fuel cell system is in an initial shutdown stage and the voltage of the fuel cell is less than or equal to a first preset value, controlling the fuel cell DC converter in the second cooling circuit to enter an active discharge mode; based on the voltage of the fuel cell being greater than a second preset value, controlling the fuel cell to actively discharge through the fuel cell DC converter, wherein the second preset value is less than the first preset value; based on the voltage of the fuel cell being less than or equal to the second preset value, controlling the fuel cell to discharge through a heat preservation device in the first cooling circuit, and controlling the heat preservation device to store heat generated by the discharge of the heat preservation device.

[0006] In the present application, when the fuel cell system enters shutdown, there will be some residual hydrogen in the anode area of ​​the stack, and the residual hydrogen needs to be removed. When the voltage of the fuel cell decays to the first preset value, the fuel cell DC converter is set to an active discharge mode. When the voltage of the fuel cell is between the first preset value and the second preset value, the fuel cell DC converter is actively discharged, thereby reducing the problem of insufficient discharge through general load pulling. When the voltage of the fuel cell is less than the second preset value, the insulation device in the second cooling circuit is discharged, which can reduce the problem of insufficient discharge through the fuel cell DC converter. At the same time, the heat generated by the insulation device during discharge is stored, so that the fuel cell system can be started next time. The heat in the insulation device can be used to achieve rapid low-temperature startup and reduce the startup time of the fuel cell system. The present application uses the electric energy of residual hydrogen discharge to consume and discharge through the insulation device, and heats and insulates the coolant stored in the insulation device in the cooling system through the insulation device during the discharge process, which can not only achieve rapid low-temperature startup of the fuel cell system, but also completely discharge the residual hydrogen.

[0007] In some embodiments, the control method of the fuel cell system further includes: controlling the heat preservation device to stop discharging based on the voltage of the fuel cell being less than or equal to a third preset value; wherein the third preset value is less than the second preset value.

[0008] In some embodiments, the control method of the fuel cell system further includes: based on the coolant temperature of the fuel cell being greater than the target temperature, controlling the fuel cell system to enter a shutdown completion stage; wherein the coolant temperature is related to the heat generated by the discharge of the insulation device.

[0009] In some embodiments, based on the fuel cell system being in the initial stage of shutdown, the control method further includes: controlling the purge device to purge the fuel cell; based on the current of the fuel cell being greater than the first load current of the fuel cell DC converter, controlling the fuel cell DC converter to perform load discharge.

[0010] In some embodiments, based on the fuel cell system being in the initial stage of shutdown, the control method also includes: controlling a purge device to purge the fuel cell; based on the time for the purge device to purge the fuel cell reaching a predetermined time, controlling the air supply subsystem to stop providing air to the cathode of the fuel cell, and controlling the hydrogen supply subsystem to adjust the anode hydrogen supply flow rate of the fuel cell to a preset flow rate value; based on the current of the fuel cell being less than the first load current of the fuel cell DC converter and greater than the second load current of the fuel cell DC converter, controlling the fuel cell to load discharge through the fuel cell DC converter.

[0011] In some embodiments, the control method of the fuel cell system also includes: shutting down the hydrogen circulation device in the hydrogen supply subsystem based on the voltage of the fuel cell being greater than a fourth preset value; wherein the fourth preset value is less than the second preset value and greater than the third preset value.

[0012] In some embodiments, controlling a fuel cell to actively discharge through a fuel cell DC converter includes: obtaining a calibrated value and a minimum value of a discharge current of the fuel cell; controlling the fuel cell to actively discharge with a final discharge current through a fuel cell DC converter; wherein the final discharge current is a larger value between the calibrated value and the minimum value, and the calibrated value is positively correlated with the real-time voltage of the fuel cell.

[0013] In some embodiments, controlling the fuel cell to enter the shutdown completion stage includes: controlling the fuel cell DC converter to stop outputting electrical energy; controlling the low-temperature circuit water pump in the second cooling circuit to stop running; and controlling the power supply of the fuel cell system to stop supplying power.

[0014] In some embodiments, the heat preservation device is controlled to store the heat generated by the discharge of the heat preservation device, including: setting the heating power of the heat preservation device to a preset power value, the preset power value is related to the target temperature of the coolant of the fuel cell; stopping the water inlet and outlet control of the heat preservation device.

[0015] The second aspect of the present application provides a fuel cell system, including: a control device, a fuel cell, a first cooling circuit and a second cooling circuit, the control device is used for shutdown control of the fuel cell system, the fuel cell is used to convert chemical energy into electrical energy, and the first cooling circuit and the second cooling circuit are used to regulate the temperature of the fuel cell; the first cooling circuit includes a thermal insulation device, and the second cooling circuit includes a fuel cell DC converter; when the fuel cell system is in the initial shutdown stage and the voltage of the fuel cell is less than or equal to a first preset value, the control device controls the fuel cell DC converter to enter an active discharge mode; based on the voltage of the fuel cell being greater than a second preset value, the control device controls the fuel cell to actively discharge through the fuel cell DC converter, wherein the second preset value is less than the first preset value; based on the voltage of the fuel cell being less than or equal to the second preset value, the control device controls the fuel cell to discharge through the thermal insulation device, and controls the thermal insulation device to store the heat generated by the discharge of the thermal insulation device.

[0016] In some embodiments, the control device controls the insulation device to stop discharging based on the voltage of the fuel cell being less than or equal to a third preset value, wherein the third preset value is less than the second preset value; the control device controls the fuel cell system to enter a shutdown completion stage based on the coolant temperature of the fuel cell being greater than a target temperature, wherein the coolant temperature is related to the heat generated by the discharge of the insulation device.

[0017] In some embodiments, the heat preservation device includes a semiconductor heater, which is disposed inside the heat preservation device and is used to release heat by utilizing the electrical energy discharged from the residual hydrogen of the fuel cell.

[0018] In some embodiments, the first cooling circuit also includes a water pump, a first radiator, a deionization device, a thermostat, an air cooler, a filter and an overflow device, wherein the insulation device and the air cooler are connected at both ends of the fuel cell, the water pump, the deionization device and the thermostat are connected at both ends of the fuel cell, and the water pump is connected to the insulation device, the thermostat is connected to the air cooler, the first radiator is connected to both ends of the fuel cell and is connected to the water pump, the deionization device and the thermostat, the overflow device is connected to the insulation device, the water pump, the first radiator and the thermostat, and the filter is arranged at the water inlet of the fuel cell stack.

[0019] In some embodiments, the second cooling circuit includes a second radiator, a first fuel cell DC converter, a low-temperature circuit water pump, a second fuel cell DC converter and an air compressor. The hydrogen circulation device of the fuel cell system is connected to the second radiator, the first fuel cell DC converter, the low-temperature circuit water pump, the second fuel cell DC converter and the air compressor in sequence. The second cooling circuit is used to regulate the temperature of the hydrogen circulation device.

[0020] A third aspect of the present application provides a control device for a fuel cell system, which is applied to the fuel cell system. The control device is used to execute any one of the control methods in the present application to achieve shutdown control of the fuel cell system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural block diagram of an embodiment of a fuel cell system of an embodiment of the present application.

[0022] Figure 2 It is a schematic diagram of the connection between various devices in the first cooling circuit and the fuel cell in an embodiment of the present application.

[0023] Figure 3 It is a connection diagram of various devices in the second cooling circuit of an embodiment of the present application.

[0024] Figure 4 It is a structural block diagram of another embodiment of the fuel cell system of the embodiment of the present application.

[0025] Figure 5 It is a flow chart of an embodiment of the control method of the embodiment of the present application.

[0026] Figure 6 It is a flow chart of the initial shutdown stage in the control method of an embodiment of the present application.

[0027] Figure 7It is a sub-flow chart of step S200 in the control method of an embodiment of the present application.

[0028] Figure 8 It is a sub-flow chart of step S300 in the control method of an embodiment of the present application.

[0029] Fig. 9 It is a flow chart of another embodiment of the control method of the embodiment of the present application.

[0030] Fig.10 It is a flow chart of another embodiment of the control method of the embodiment of the present application.

[0031] Fig.11 It is a sub-flow chart of step S500 in the control method of an embodiment of the present application.

[0032] Main component symbols 1. Fuel cell system; 10. Control device; 11. First cooling circuit; 12. Second cooling circuit; 13. Fuel cell; 14. Air supply subsystem; 15. Hydrogen supply subsystem; 111. Insulation device; 1111. Semiconductor heater; 1112. Water inlet control valve; 1113. Water outlet control valve; 112. Water pump; 113. First radiator; 114. Deionization device; 115. Thermostat; 116. Air cooler; 117. Filter; 118. Overflow device; 121. Second radiator; 122. First fuel cell DC converter; 123. Low temperature circuit water pump; 124. Second fuel cell DC converter; 125. Air compressor; 126. Hydrogen circulation device.

[0033] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0034] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a concrete manner.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field in this application. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. It should be understood that, unless otherwise specified in this application, " / " means or. For example, A / B can represent A or B. "And / or" in this application is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. "At least one" means one or more. "Multiple" means two or more than two. For example, at least one of a, b or c can represent: a, b, c, a and b, a and c, b and c, a, b and c seven situations.

[0036] It should also be noted that the terms "first" and "second" in the specification, claims and drawings of this application are used to distinguish similar objects, rather than to describe a specific order or sequence. The method disclosed in the embodiments of this application or the method shown in the flowchart includes one or more steps for implementing the method. Without departing from the scope of the claims, the execution order of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0037] A fuel cell is a chemical device that converts the chemical energy of a fuel directly into electrical energy, also known as an electrochemical generator. Fuel cells mainly include: Proton Exchange Membrane Fuel Cell (PEMFC), Alkaline Fuel Cell (AFC), Phosphoric Acid Fuel Cell (PAFC), Solid Oxide Fuel Cell (SOFC) and Molten Carbonate Fuel Cell (MCFC). Fuel cell shutdown purge is an important method to ensure safe storage and normal startup of the battery in a low temperature environment. When the fuel cell is shut down, it is necessary to purge the inside of the fuel cell to control the water content of the fuel cell to prevent the water from freezing and causing the fuel cell reaction channel to be blocked, thereby improving the success rate of the next low-temperature cold start of the fuel cell. By shutting down and purging and cooperating with low-temperature startup control strategies (such as active heating), the fuel cell system can achieve a higher success rate of startup, but there is a disadvantage of a long low-temperature startup time.

[0038] In the related art, the waste heat of the fuel cell stack can be recovered through the cooling system and stored in the insulation device, so that the insulation device is used to keep the stack warm for the next low-temperature cold start. This solution can solve the disadvantage of long low-temperature start-up time, but it lacks a solution to solve the problem of residual hydrogen discharge in the stack. Residual hydrogen discharge in the fuel cell stack refers to when the fuel cell system is shut down, there is still unreacted hydrogen in the fuel cell stack. In order to ensure electrical safety and the service life of the stack, a load, such as a fuel cell DC converter (FDC), is required to release the residual hydrogen energy in the stack in time. In the related art, the residual hydrogen discharge in the stack is mostly a single discharge method, such as load discharge through a fuel cell DC converter, but this method is not thorough, and voltage rebound is likely to occur after the discharge is completed, or discharge is carried out through the discharge resistor inside the fuel cell DC converter, but due to the limitation of the discharge resistor power, the discharge time may be very long. If the discharge resistor power needs to be increased, a higher cost and larger volume discharge resistor is required for discharge, which does not meet the development needs and direction of compact integration and low cost of fuel cell systems.

[0039] Therefore, even if the battery stack waste heat recovery method of the related technology is combined with the relevant residual hydrogen discharge strategy, it still has the disadvantages of incomplete discharge and high cost, which is not conducive to extending the battery life.

[0040] To this end, the embodiments of the present application provide a control method and a control device thereof, which can use the electrical energy of the residual hydrogen discharge to heat and keep the coolant in the cooling system when the fuel cell system is shut down, so as to achieve rapid low-temperature startup of the fuel cell system and completely discharge the residual hydrogen. Some embodiments will be described below in conjunction with the accompanying drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0041] Figure 1 It is a structural block diagram of an embodiment of the fuel cell system 1 of the embodiment of the present application.

[0042] The embodiment of the present application first provides a control device 10 of a fuel cell system, which is applied to the fuel cell system 1. The control device 10 is used to execute any control method in the present application to achieve shutdown control of the fuel cell system 1.

[0043] See also Figure 1As shown, the fuel cell system 1 may include the control device 10 of the embodiment of the present application. In addition, the fuel cell system 1 may also include a fuel cell 13, a first cooling circuit 11 and a second cooling circuit 12. The fuel cell 13 may directly convert the chemical energy of the fuel (such as hydrogen) into electrical energy, and the conversion method may be a redox reaction, and the reaction site may be called a fuel cell stack (or "stack"). The first cooling circuit 11 and the second cooling circuit 12 may be used to adjust the temperature of the fuel cell 13.

[0044] In some embodiments, the control device 10 may include a fuel cell controller (Fuel-Cell Control Unit, FCU / FCCU), which can be used for overall control of the entire fuel cell system 1. The control content may include monitoring hydrogen and oxygen content, hydrogen and oxygen supply control, thermal management, water circulation management, energy conversion management, fault analysis, and safety monitoring.

[0045] In some embodiments, the fuel cell controller may also be replaced by one or more controllers or controller combinations having the same or similar functions, such as a microcontroller unit (MCU) or a central processing unit (CPU).

[0046] Figure 2 Schematic diagram of the connection between the various devices in the first cooling circuit 11 and the fuel cell 13 in the embodiment of the present application.

[0047] In the embodiments of the present application, Figure 2 As shown, the first cooling circuit 11 may include a heat preservation device 111, a water pump 112, a first radiator 113, a deionization device 114, a thermostat 115, an air cooler 116, a filter 117 and an overflow device 118. Each structure or device is connected by a pipeline, and the pipeline is filled with coolant.

[0048] Among them, the heat preservation device 111 and the air cooler 116 are "connected in parallel" at both ends (water inlet and water outlet) of the fuel cell stack, that is, the heat preservation device 111 and the air cooler 116 are connected at both ends of the fuel cell stack. The water pump 112, the deionization device 114 and the thermostat 115 are "connected in parallel" at both ends of the fuel cell stack and are connected to the heat preservation device 111 and the air cooler 116, that is, the water pump 112, the deionization device 114 and the thermostat 115 are connected at both ends of the fuel cell stack, and the water pump 112 is connected to the heat preservation device 111, and the thermostat 115 is connected to the air cooler 116. The first radiator 113 is "connected in parallel" at both ends of the fuel cell stack and is connected to the water pump 112, the deionization device 114 and the thermostat 115, that is, the first radiator 113 is connected to both ends of the fuel cell stack and is connected to the water pump 112, the deionization device 114 and the thermostat 115. The overflow device 118 is connected to the heat preservation device 111, the water pump 112, the first radiator 113 and the thermostat 115. Specifically, the overflow device 118 is connected to the connecting pipeline between the heat preservation device 111 and the water outlet of the battery stack, the connecting pipeline between the water pump 112 and the heat preservation device 111, and the connecting pipeline between the first radiator 113 and the thermostat 115. The filter 117 is arranged at the water inlet of the battery stack.

[0049] The first cooling circuit 11 of the embodiment of the present application is used to adjust the temperature or control the heat of the fuel cell stack, so the first cooling circuit 11 can also be called a stack cooling circuit.

[0050] The heat preservation device 111, also known as a heat insulation pot, can be used to recover the heat of the coolant in the pipeline. When the coolant retains a certain amount of heat, the heater heating start can be reduced when the fuel cell system 1 is started next time, thereby achieving a fast low-temperature cold start.

[0051] In some embodiments, the heat preservation device 111 may include a semiconductor heater 1111. The semiconductor heater 1111, also known as a thermistor heater (Positive Temperature Coefficient, PTC), may be disposed inside the heat preservation device 111 to heat the coolant in the heat preservation device 111. Specifically, the semiconductor heater 1111 may utilize the electrical energy discharged by the residual hydrogen when the fuel cell system 1 is shut down to release heat to heat the coolant in the heat preservation device 111.

[0052] In some embodiments, the heat preservation device 111 may include a water inlet control valve 1112 and a water outlet control valve 1113. The water inlet control valve 1112 is provided in the connection pipeline between the heat preservation device 111 and the air cooler 116, and is used to control the coolant to enter the heat preservation device 111. The water outlet control valve 1113 is provided in the connection pipeline where the heat preservation device 111 and the connection pipeline between the water pump 112 and the fuel cell stack intersect, and is used to control the coolant to be discharged from the heat preservation device 111.

[0053] The water pump 112 can be used to provide power for the coolant to flow, so that the coolant can circulate in various connecting pipes or devices.

[0054] The first radiator 113 can be used to dissipate heat from the coolant or transfer the heat absorbed from the coolant to heat-using equipment, such as heating equipment and the heat preservation device 111.

[0055] The deionization device 114 , also known as a deionization tank, can be used to deionize (also known as “desalting”) the coolant discharged from the fuel cell stack.

[0056] The thermostat 115 , also known as a three-way electronic temperature control valve or an automatic temperature control device, can be used to adjust the flow path size of the coolant by means of expansion or contraction to achieve heat control of the first cooling circuit 11 .

[0057] The air cooler 116 can be used to further cool the coolant entering the heat preservation device 111 .

[0058] The filter 117 can be used to filter dust and particulates from the coolant entering the fuel cell stack, and is therefore also called a particulate filter 117 .

[0059] Figure 3 Schematic diagram of the connection of the devices in the second cooling circuit 12 of the embodiment of the present application.

[0060] In the embodiments of the present application, Figure 3 As shown, the second cooling circuit 12 may include a second radiator 121, a first fuel cell DC converter 122, a low temperature circuit water pump 123, a second fuel cell DC converter 124 and an air compressor 125. The second cooling circuit 12 is used to perform temperature regulation or heat management on the hydrogen circulation device 126 of the fuel cell system 1, thereby regulating the temperature of the hydrogen entering the fuel cell stack 13. The second cooling circuit 12 requires less heat to be managed than the first cooling circuit 11, so it is also called a low temperature cooling circuit.

[0061] The hydrogen circulation device 126 is connected to the second radiator 121, the first fuel cell DC converter 122, the low-temperature circuit water pump 123, the second fuel cell DC converter 124 and the air compressor 125 in sequence, and each structure or device is connected through a pipeline filled with coolant.

[0062] The hydrogen circulation device 126 can be used for hydrogen supply and recovery circulation of the fuel cell system 1 .

[0063] The second radiator 121 may be used to dissipate heat and cool the coolant discharged from the hydrogen circulation device 126 .

[0064] The first fuel cell DC converter 122 and the second fuel cell DC converter 124 can be used to convert the unadjustable DC power output by the fuel cell 13 into adjustable DC power, and output it to a battery (such as a car's power battery) for storage or to an auxiliary system for use.

[0065] The low-temperature circuit water pump 123 can be used to provide flow power for the coolant in the second cooling circuit 12 so that the coolant can circulate in various connecting pipelines or devices.

[0066] The air compressor 125 can be used to dissipate heat and cool the coolant in the second cooling loop 12 by means of air cooling, and can be used to provide air with a certain temperature or heat to the cathode of the fuel cell stack.

[0067] Figure 4 It is a structural block diagram of another embodiment of the fuel cell system 1 of the embodiment of the present application.

[0068] In some embodiments, Figure 4 As shown, the fuel cell system 1 also includes an air supply subsystem 14 and a hydrogen supply subsystem 15. The air supply subsystem 14 can be used to provide air to the cathode of the fuel cell stack or to purge the cathode of the fuel cell stack, and the air supply subsystem 14 can include the air compressor 125 of the above embodiment, that is, the air compressor 125 in the second cooling loop 12. The hydrogen supply subsystem 15 can be used to provide hydrogen to the anode of the fuel cell stack, and the hydrogen supply subsystem 15 can include the hydrogen circulation device 126 of the above embodiment.

[0069] In some embodiments, the hydrogen supply subsystem 15 may include a hydrogen injection valve, which can be used to adjust the hydrogen pressure of the anode of the fuel cell 13 so that the pressure difference between the cathode and anode gases of the fuel cell 13 is within a preset value, thereby facilitating the fuel cell stack reaction and ensuring the reaction safety.

[0070] In some embodiments, the insulation device 111, water pump 112, air cooler 116, low-temperature circuit water pump 123, and air compressor 125 of the above-mentioned embodiments can be collectively referred to as auxiliary devices of the fuel cell system 1, and the first cooling circuit 11, the second cooling circuit 12, the air supply subsystem 14 and the hydrogen supply subsystem 15 can be collectively referred to as the auxiliary system (Balance of Plant, BOP) of the fuel cell system 1.

[0071] In some embodiments, the fuel cell system 1 may further include a purge device, which may be used to purge the interior of the fuel cell 13 when the fuel cell 13 is shut down, so as to control the water content of the fuel cell 13 and prevent the water from freezing and causing the reaction channel of the fuel cell 13 to be blocked.

[0072] In some embodiments, the purging device may be at least one of air blast purging, medium purging, and pressure loss purging. In the embodiment of the present application, the purging device may also be the air compressor 125 in the air supply subsystem 14 .

[0073] Figure 5 It is a flow chart of an embodiment of the control method of the embodiment of the present application.

[0074] The present application also provides a control method for a fuel cell system, hereinafter referred to as the control method. Figure 5 , the control methods may include: Step S100: when the fuel cell system is in the initial shutdown stage and the voltage of the fuel cell is less than or equal to a first preset value, the fuel cell DC converter in the second cooling loop is controlled to enter an active discharge mode.

[0075] It is understandable that when the fuel cell system is in the initial stage of shutdown, there is still residual hydrogen in the fuel cell stack. In order to improve the safety and life of the fuel cell, it is necessary to discharge the residual hydrogen, and load-pulling discharge can usually be used. Load-pulling discharge usually requires setting a load current. When the current of the fuel cell exceeds the load current, the electric energy generated by the residual hydrogen discharge is connected to various energy-consuming loads, and discharged and consumed through various energy-consuming loads. In step S100 of an embodiment of the present application, when the voltage of the fuel cell is less than or equal to the first preset value, the fuel cell DC converter in the second cooling circuit can be controlled to enter an active discharge mode, wherein active discharge means that the electric energy generated by the residual hydrogen discharge is directly connected to the load for discharge consumption without considering the current of the fuel cell.

[0076] The voltage of the fuel cell will usually continue to decay along with the residual hydrogen content when the fuel cell is shut down, so the voltage of the fuel cell involved in the embodiments of the present application refers to the real-time voltage (or "actual voltage") of the fuel cell.

[0077] The fuel cell DC converter in the second cooling circuit of the embodiment of the present application may include the first fuel cell DC converter and the second fuel cell DC converter described above. The first fuel cell DC converter and the second fuel cell DC converter may be connected to the auxiliary machine or the power battery circuit of the vehicle.

[0078] Figure 6 It is a flow chart of the initial shutdown stage in the control method of an embodiment of the present application.

[0079] In some embodiments, see Figure 6 When the fuel cell system is in the initial shutdown stage, the control method further includes: Step S001: controlling the purge device to purge the fuel cell.

[0080] It can be understood that step S001 can control the water content of the fuel cell to prevent water from freezing and causing the fuel cell reaction channel to be blocked. Specifically, the embodiment of the present application can purge the cathode of the fuel cell by an air compressor.

[0081] Step S002: When the current of the fuel cell is greater than a first current value, the fuel cell DC converter is controlled to perform load discharge, wherein the first current value can be set according to the actual current of the fuel cell.

[0082] It can be understood that when the current of the fuel cell exceeds the first current value, the electric energy discharged by the residual hydrogen in the fuel cell will be consumed by the fuel cell DC converter, thereby reducing the problem of fuel cell over-current through steps S002 and S003. At this time, the electric energy discharged by the residual hydrogen in the fuel cell can be used for storage in the power battery of the vehicle after passing through the fuel cell DC converter.

[0083] In some embodiments, based on the fuel cell system being in the initial shutdown stage, the control method further includes: Step S003: When the time for the purge device to purge the fuel cell reaches a predetermined time, the air supply subsystem is controlled to stop supplying air to the cathode of the fuel cell, and the hydrogen supply subsystem is controlled to adjust the hydrogen supply flow rate of the anode of the fuel cell to a preset flow rate value.

[0084] Among them, the predetermined time can be set according to the water content requirement of the fuel cell. The preset flow value can be set according to the residual hydrogen content of the fuel cell. Controlling the air supply subsystem to stop supplying air to the cathode of the fuel cell can be to control the air compressor in the air supply subsystem to stop supplying air to the cathode of the fuel cell. Controlling the hydrogen supply subsystem to adjust the anode hydrogen supply flow rate of the fuel cell to a preset flow value can be to control the hydrogen injection valve in the hydrogen supply subsystem to adjust the anode hydrogen supply flow rate of the fuel cell to a preset flow value, so that the pressure difference between the anode and cathode gases of the fuel cell is at a preset value, thereby facilitating the fuel cell stack reaction and ensuring the safety of the reaction.

[0085] Step S004: When the current of the fuel cell is greater than the second current value and less than the first current value, the fuel cell is controlled to be loaded and discharged through the fuel cell DC converter. The second current value is less than the first current value. The second current value can be set according to the single-chip voltage of the fuel cell.

[0086] It can be understood that when the current of the fuel cell exceeds the second current value, the electric energy discharged by the residual hydrogen in the fuel cell will be consumed by the fuel cell DC converter, thereby reducing the problem of over-current in the single-chip fuel cell through step S004. At this time, the electric energy discharged by the residual hydrogen in the fuel cell can be used for auxiliary machine consumption and storage in the power battery of the vehicle after passing through the fuel cell DC converter.

[0087] When the fuel cell system is in the initial stage of shutdown, the control method also includes steps S001 to S004, that is, before step S100, steps S001 to S004 may be included. Therefore, steps S001 to S004 may also be referred to as the "initial stage of shutdown". In the initial stage of shutdown, except for the fuel cell stack of the fuel cell system, other devices or subsystems, such as the fuel cell DC converter, hydrogen circulation device, air supply subsystem or hydrogen supply subsystem, have not stopped running or have not completely stopped running. The control method of the embodiment of the present application aims to use the combined discharge to consume the residual hydrogen of the fuel cell stack when the fuel cell system enters the shutdown completion stage, and at the same time use the electric energy of the residual hydrogen discharge to heat the coolant so that the fuel cell system can be quickly cold-started at low temperature next time.

[0088] like Figure 5 As shown, the control method of the embodiment of the present application may also include: Step S200: Based on the voltage of the fuel cell being greater than a second preset value, the fuel cell is controlled to perform active discharge through the fuel cell DC converter.

[0089] Among them, the second preset value is less than the first preset value. The second preset value can be set according to the actual voltage of the fuel cell. It can be understood that when the voltage of the fuel cell decays to less than the first preset value and greater than the second preset value as the residual hydrogen content decreases after the fuel cell is purged for a preset time, the current of the fuel cell does not meet the load discharge current (i.e., the first current value and the second current value), and at this time, the fuel cell can be controlled to actively discharge through the fuel cell DC converter to reduce the voltage of the fuel cell to a safe voltage value.

[0090] Figure 7 It is a sub-flow chart of step S200 in the control method of an embodiment of the present application.

[0091] In some embodiments, Figure 7 As shown, step S200 may include: Sub-step S201: Obtain the calibrated value and minimum value of the discharge current of the fuel cell.

[0092] Sub-step S202: Control the fuel cell to actively discharge with a final discharge current through the fuel cell DC converter.

[0093] Among them, the final discharge current is the larger value between the calibration value and the minimum value, and the calibration value is positively correlated with the real-time voltage of the fuel cell. The calibration value of the discharge current can be obtained by the formula: I_dic=a*V_in+b, V_in is the real-time voltage of the fuel cell stack during discharge, a and b are calibrable constants, and the corresponding discharge current curve is set by modifying a and b. The minimum value of the discharge current is also set according to the real-time voltage of the fuel cell stack during discharge.

[0094] It can be understood that the fuel cell is controlled to perform active discharge with a final discharge current through the fuel cell DC converter, and the final discharge current of the fuel cell is the larger value between the calibrated value and the minimum value, so the efficiency of active discharge of the fuel cell DC converter can be improved.

[0095] like Figure 5 As shown, the control method of the embodiment of the present application may also include: Step S300: Based on the voltage of the fuel cell being less than or equal to a second preset value, the fuel cell is controlled to discharge through the heat preservation device in the first cooling circuit, and the heat preservation device is controlled to store heat generated by the discharge of the heat preservation device.

[0096] The electric energy discharged by the residual hydrogen can be discharged and consumed by the semiconductor heater in the heat preservation device.

[0097] The control method of the fuel cell of the embodiment of the present application utilizes a combined discharge mode, that is, when the voltage of the fuel cell is high, such as greater than the second preset value, the fuel cell DC converter is used to perform small load discharge and active discharge, that is, step S200. When the voltage is about to reach a specific limit, that is, less than or equal to the second preset value, the heat preservation device is used for discharge, that is, step S300. In this way, the voltage of the fuel cell can be quickly reduced to a safe voltage value, and the discharge resistor in the fuel cell DC converter can be saved, the space volume of the fuel cell DC converter can be reduced, and the cost can be reduced.

[0098] In addition, the heat preservation device can store the heat generated by the discharge, that is, the heat generated by the semiconductor heater in the heat preservation device using the electric energy of the residual hydrogen discharge for heating can be stored by the heat preservation device. The heated medium can be a coolant. In this case, when the fuel cell system is cold-started at low temperature next time, the coolant with residual heat can quickly heat up the inside of the fuel cell, shorten the low-temperature cold-start time of the fuel cell, and improve the success rate of the start-up.

[0099] In addition, when the control device executes step S300, the fuel cell DC converter can be controlled to be in a standby state. If the voltage of the fuel cell rebounds, that is, it is greater than the second preset value, the fuel cell DC converter continues to be used for small load discharge and active discharge, that is, step S200 is continued.

[0100] Figure 8 It is a sub-flow chart of step S300 in the control method of an embodiment of the present application.

[0101] In some embodiments, Figure 3 As shown, step S300 may include: Sub-step S301: setting the heating power of the heat preservation device to a preset power value.

[0102] Among them, the preset power value is related to the target temperature. The heating power of the insulation device may refer to the heating power of the semiconductor heater in the insulation device. The semiconductor heater is turned on after receiving the control instruction of the control device to consume the electric energy discharged by the residual hydrogen of the fuel cell and heat the coolant in the insulation device. Optionally, the heating method of the semiconductor heater may be a pulse width modulation (PWM) method. It can be understood that the "storage" in step S300 in the embodiment of the present application may refer to insulating and sealing the coolant in the insulation device and heating the coolant.

[0103] Sub-step S302: Stop the water inlet and outlet control of the heat preservation device.

[0104] Specifically, stopping the water inlet and outlet control of the heat preservation device can be to control the water inlet control valve of the heat preservation device to stop delivering the coolant to the heat preservation device and to control the water outlet control valve to stop discharging the coolant from the heat preservation device. In this way, the coolant can be heated and kept warm, so that when the fuel cell system is cold-started at low temperature next time, the coolant with residual heat can quickly heat up the inside of the fuel cell, thereby achieving a rapid cold start.

[0105] In the embodiment of the present application, step S100 to step S300 may also be referred to as an “active discharge phase”.

[0106] Fig. 9 It is a flow chart of another embodiment of the control method of the embodiment of the present application.

[0107] In some embodiments, see Fig. 9 , the control method may further include: Step S400: Based on the voltage of the fuel cell being less than or equal to a third preset value, controlling the heat preservation device to stop discharging.

[0108] The third preset value is less than the second preset value. The third preset value can be set according to the actual voltage of the fuel cell. Controlling the heat preservation device to stop discharging can be controlling the semiconductor heater in the heat preservation device to stop heating.

[0109] Fig.10 It is a flow chart of another embodiment of the control method of the embodiment of the present application.

[0110] In some embodiments, see Fig.10 Optionally, the control method further includes: Step S304: when the voltage of the fuel cell is greater than a fourth preset value, shutting down the hydrogen circulation device in the hydrogen supply subsystem.

[0111] The fourth preset value is less than the second preset value and greater than the third preset value. Step S304 may be between step S300 and step S400. Thus, the problem of adding new hydrogen to the fuel cell stack to form residual hydrogen in step S400 can be reduced.

[0112] like Fig. 9 As shown, the control method also includes: Step S500: Based on the coolant temperature of the fuel cell being greater than the target temperature, the fuel cell system is controlled to enter a shutdown completion phase.

[0113] Among them, the coolant temperature is related to the heat generated by the discharge of the insulation device.

[0114] Fig.11 It is a sub-flow chart of step S500 in the control method of an embodiment of the present application.

[0115] In some embodiments, step S500 may include: Sub-step S501: Control the fuel cell DC converter to stop outputting electrical energy.

[0116] Specifically, controlling the fuel cell DC converter to stop outputting electric energy may be controlling the fuel cell DC converter to enter a standby state or cutting off the electrical connection with the auxiliary machine and the power battery.

[0117] Sub-step S502: Control the low-temperature circuit water pump in the second cooling circuit to stop running.

[0118] Sub-step S503: Control the power supply of the fuel cell system to stop supplying power.

[0119] Thus, the fuel cell system enters the shutdown completion stage. In the embodiment of the present application, steps S400 to S500 may also be referred to as the "shutdown completion stage".

[0120] In summary, in the present application, when the fuel cell system enters shutdown, some residual hydrogen will exist in the anode area of ​​the stack, and the residual hydrogen needs to be removed. When the voltage of the fuel cell decays to the first preset value, the fuel cell DC converter is set to the active discharge mode. When the voltage of the fuel cell is between the first preset value and the second preset value, the fuel cell DC converter is actively discharged, thereby reducing the problem of incomplete discharge through general load pulling. When the voltage of the fuel cell is less than the second preset value, the heat preservation device in the second cooling circuit is used for discharge, which can reduce the problem of incomplete discharge through the fuel cell DC converter. At the same time, the heat generated by the heat preservation device during discharge is stored, so that the next time the fuel cell system is started, the heat energy in the heat preservation device can be used to achieve rapid low-temperature startup, thereby reducing the startup time of the fuel cell system.

[0121] The present application utilizes the electrical energy discharged from the residual hydrogen to be consumed and discharged through a heat preservation device, and during the discharge process, the heat preservation device is used to heat and preserve the coolant stored in the heat preservation device in the cooling system, which can not only achieve rapid low-temperature start-up of the fuel cell system, but also completely discharge the residual hydrogen.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application has been described in detail with reference to the preferred embodiments, a person of ordinary skill in the art should understand that the technical solution of the present application may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present application.

Claims

1. A fuel cell system, characterized in that: The system comprises: a control device, a fuel cell, a first cooling circuit and a second cooling circuit, wherein the control device is used for shutdown control of the fuel cell system, the fuel cell is used for converting chemical energy into electrical energy, and the first cooling circuit and the second cooling circuit are used for regulating the temperature of the fuel cell; The first cooling circuit includes a heat preservation device, and the second cooling circuit includes a fuel cell DC converter; When the fuel cell system is in the initial shutdown stage and the voltage of the fuel cell is less than or equal to a first preset value, the control device controls the fuel cell DC converter to enter an active discharge mode; The control device controls the fuel cell to actively discharge through the fuel cell DC converter based on the voltage of the fuel cell being greater than a second preset value, wherein the second preset value is less than the first preset value; The control device controls the fuel cell to discharge through the heat preservation device based on the voltage of the fuel cell being less than or equal to the second preset value, and controls the heat preservation device to store heat generated by the discharge of the heat preservation device.

2. The fuel cell system according to claim 1, characterized in that: The control device controls the heat preservation device to stop discharging based on the voltage of the fuel cell being less than or equal to a third preset value, wherein the third preset value is less than the second preset value; The control device controls the fuel cell system to enter a shutdown completion stage based on the coolant temperature of the fuel cell being greater than a target temperature, wherein the coolant temperature is related to the heat generated by the discharge of the heat preservation device.

3. The fuel cell system according to claim 1, characterized in that: The heat preservation device comprises a semiconductor heater, which is arranged inside the heat preservation device and is used for releasing heat by utilizing the electrical energy discharged by the residual hydrogen of the fuel cell.

4. The fuel cell system according to claim 1, characterized in that: The first cooling circuit also includes a water pump, a first radiator, a deionization device, a thermostat, an air cooler, a filter and an overflow device, wherein the insulation device and the air cooler are connected to both ends of the fuel cell, the water pump, the deionization device and the thermostat are connected to both ends of the fuel cell, and the water pump is connected to the insulation device, the thermostat is connected to the air cooler, the first radiator is connected to both ends of the fuel cell and to the water pump, the deionization device and the thermostat, the overflow device is connected to the insulation device, the water pump, the first radiator and the thermostat, and the filter is arranged at the water inlet of the fuel cell stack.

5. The fuel cell system according to claim 1, characterized in that: The second cooling circuit includes a second radiator, a first fuel cell DC converter, a low-temperature circuit water pump, a second fuel cell DC converter and an air compressor. The hydrogen circulation device of the fuel cell system is connected to the second radiator, the first fuel cell DC converter, the low-temperature circuit water pump, the second fuel cell DC converter and the air compressor in sequence. The second cooling circuit is used to regulate the temperature of the hydrogen circulation device.

6. A control method for a fuel cell system, the fuel cell system comprising a fuel cell, a first cooling circuit and a second cooling circuit for regulating the temperature of the fuel cell, characterized in that: The method comprises: When the fuel cell system is in an initial shutdown stage and the voltage of the fuel cell is less than or equal to a first preset value, controlling the fuel cell DC converter in the second cooling circuit to enter an active discharge mode; Based on the voltage of the fuel cell being greater than a second preset value, controlling the fuel cell to actively discharge through the fuel cell DC converter, wherein the second preset value is less than the first preset value; Based on the voltage of the fuel cell being less than or equal to the second preset value, the fuel cell is controlled to discharge through the heat preservation device in the first cooling circuit, and the heat preservation device is controlled to store heat generated by the discharge of the heat preservation device.

7. The control method of the fuel cell system according to claim 6, characterized in that: The control method further comprises: Based on the voltage of the fuel cell being less than or equal to a third preset value, controlling the heat preservation device to stop discharging; Wherein, the third preset value is smaller than the second preset value.

8. The control method of the fuel cell system according to claim 7, characterized in that: The control method further comprises: Based on the coolant temperature of the fuel cell being greater than the target temperature, controlling the fuel cell system to enter a shutdown completion phase; The temperature of the coolant is related to the heat generated by the discharge of the heat preservation device.

9. The control method of the fuel cell system according to claim 8, characterized in that: Based on the fuel cell system being in the initial shutdown stage, the control method further includes: Controlling a purge device to purge the fuel cell; Based on the fact that the current of the fuel cell is greater than the first load current of the fuel cell DC converter, the fuel cell DC converter is controlled to perform load discharge.

10. The control method of the fuel cell system according to claim 8, characterized in that: Based on the fuel cell system being in the initial shutdown stage, the control method further includes: Controlling a purge device to purge the fuel cell; Based on the time for the purge device to purge the fuel cell reaching a predetermined time, controlling the air supply subsystem to stop supplying air to the cathode of the fuel cell, and controlling the hydrogen supply subsystem to adjust the hydrogen supply flow rate of the anode of the fuel cell to a preset flow rate value; Based on the current of the fuel cell being less than the first load current of the fuel cell DC converter and greater than the second load current of the fuel cell DC converter, the fuel cell is controlled to perform load discharge through the fuel cell DC converter.

11. The control method of the fuel cell system according to claim 7, characterized in that: The control method further comprises: Based on the voltage of the fuel cell being greater than a fourth preset value, shutting down a hydrogen circulation device in the hydrogen supply subsystem; The fourth preset value is smaller than the second preset value and larger than the third preset value.

12. The control method of the fuel cell system according to claim 6, characterized in that: The step of controlling the fuel cell to actively discharge through the fuel cell DC converter comprises: Obtaining a calibrated value and a minimum value of a discharge current of the fuel cell; Controlling the fuel cell to actively discharge with a final discharge current through the fuel cell DC converter; The final discharge current is a larger value between the calibration value and the minimum value, and the calibration value is positively correlated with the real-time voltage of the fuel cell.

13. The control method of the fuel cell system according to claim 8, characterized in that: The step of controlling the fuel cell to enter a shutdown completion phase includes: Controlling the fuel cell DC converter to stop outputting electrical energy; Controlling the low-temperature circuit water pump in the second cooling circuit to stop running; and The power supply of the fuel cell system is controlled to stop supplying power.

14. The control method of the fuel cell system according to claim 6, characterized in that: The controlling the heat preservation device to store the heat generated by the heat preservation device during discharge comprises: Setting the heating power of the heat preservation device to a preset power value, wherein the preset power value is related to the target temperature of the coolant of the fuel cell; Stop the water inlet and outlet control of the heat preservation device.

15. A control device for a fuel cell system, characterized in that: The control device is used to execute the control method as described in any one of claims 6 to 14 to achieve shutdown control of the fuel cell system.

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