Control method for stable operation of fuel cell system

Abstract

The invention discloses a control method for stable operation of a fuel cell system. The control method comprises the following steps: controlling the fuel cell system to complete a cold start preheating process; controlling the fuel cell system to adjust the output power; controlling the fuel cell system to carry out output power adjustment, namely controlling a first fuel supplier to input fuel to an evaporator, and controlling a liquid water supplier to input water to the evaporator, so that the fuel and the water output by the evaporator sequentially enter a first-stage electric pile and a second-stage electric pile; and controlling the output power of the first-stage electric pile to be gradually increased to first rated output power, and controlling the output power of the second-stage electric pile to be gradually reduced to a set value. In the initial stage of combustion power generation of the fuel cell, fuel which is not fully combusted due to relatively low output power of the first-stage electric pile can enter the second-stage electric pile to be fully combusted, so that the utilization rate of the fuel in the fuel cell is improved, meanwhile, stable adjustment of the power of the first-stage electric pile and the second-stage electric pile is ensured, and the stability of the system is improved.

Description

Technical Field

[0001] The present invention relates to the field of fuel cell technology, and in particular to a control method for stable operation of a fuel cell system. Background Technology

[0002] Fuel cells have the advantages of high power generation efficiency, high comprehensive thermal efficiency, combined heat and power, and are environmentally friendly. They are an important component of future distributed power stations and have broad application prospects.

[0003] Most fuel cells work in a single stack or multiple stacks in parallel. For systems with multiple stacks working in series, there is no clear control scheme for different levels of stacks, which can easily lead to instability in the operation of the fuel cell system. SUMMARY OF THE INVENTION

[0004] The present invention provides a control method for the stable operation of a fuel cell system to ensure the smooth regulation of the power of the first-stage fuel cell stack and the second-stage fuel cell stack and improve the stability of the system.

[0005] According to one aspect of the present invention, a control method for stable operation of a fuel cell system is provided, which is used to control the fuel cell system, wherein the fuel cell system comprises a fuel cell, a first fuel supplier, an evaporator and a liquid water supplier, wherein the fuel cell comprises a first-stage stack and a second-stage stack, wherein the output end of the first fuel supplier is connected to the first input end of the evaporator, the output end of the liquid water supplier is connected to the second input end of the evaporator, the output end of the evaporator is connected to the input end of the first-stage stack, and the output end of the first-stage stack is connected to the input end of the second-stage stack;

[0006] The control method for stable operation of the fuel cell system includes:

[0007] Control the fuel cell system to complete the cold start preheating process;

[0008] Control the fuel cell system to adjust output power;

[0009] The controlling the fuel cell system to adjust the output power includes:

[0010] Control the first fuel supplier to input fuel to the evaporator, and control the liquid water supplier to input water to the evaporator, so that the fuel and water output by the evaporator enter the first-stage battery stack and the second-stage battery stack in sequence, and the output power of the first-stage battery stack and the second-stage battery stack is zero;;

[0011] Control the output power of the first-stage stack to gradually increase to the first rated output power, and control the output power of the second-stage stack to gradually decrease from the second rated output power to the set value.

[0012] Optionally, the fuel cell system further includes a flame burner, a catalytic burner, an air preheater, a first-stage reformer, and a second fuel supply. A first input end of the flame burner is connected to an output end of the second-stage fuel cell stack. An output end of the flame burner is connected to an input end of the catalytic burner. An output end of the catalytic burner is connected to a first input end of the air preheater. A first output end of the air preheater is connected to a first input end of the first-stage reformer. A second input end of the air preheater is used for inputting air. A second output end of the air preheater is connected to a third input end of the evaporator. An output end of the evaporator is connected to a second input end of the first-stage reformer. An output end of the first-stage reformer is connected to an input end of the first-stage fuel cell stack. An output end of the second fuel supply is connected to a second input end of the flame burner;

[0013] Controlling the fuel cell system to complete the cold start preheating process includes:

[0014] Controlling the second fuel supply to supply fuel to the flame burner;

[0015] Controlling the flame burner to start, so that the fuel burns in the flame burner;

[0016] Controlling the gas output after the flame burner burns to be input into the air preheater through the catalytic burner until the gas in the air preheater heats the temperature of the first-stage reformer to a first set temperature, wherein the temperature of the gas output after the flame burner burns is less than the ignition temperature of the catalytic burner.

[0017] Optionally, when controlling the fuel cell system to adjust the output power, after determining that the flame burner is extinguished, at different moments within a preset time, obtain the temperature at the output end of the catalytic burner;

[0018] According to the temperature at the output end of the catalytic burner obtained at different moments, determine whether the catalytic burner starts successfully;

[0019] If it is determined that the catalytic burner starts successfully, then control the output power of the second-stage fuel cell stack to gradually increase until both the first-stage fuel cell stack and the second-stage fuel cell stack are operating at full load.

[0020] Optionally, after determining whether the catalytic burner starts successfully according to the temperature at the output end of the catalytic burner obtained at different moments, it further includes:

[0021] If it is determined that the catalytic burner starts unsuccessfully, then control the fuel cell system to shut down and input air into the second-stage fuel cell stack.

[0022] Optionally, determining that the flame burner is extinguished includes:

[0023] Obtaining the temperature at the output end of the flame burner in real time;

[0024] Calculating the temperature change rate of the output end of the flame burner according to the temperatures at the output end of the flame burner obtained at different times;

[0025] If the temperature change rate of the output end of the flame burner is less than or equal to the absolute value of the set decay rate, it is determined that the flame burner is extinguished, where the set decay rate is less than zero.

[0026] Optionally, determining whether the catalytic burner starts successfully according to the temperatures at the output end of the catalytic burner obtained at different times includes:

[0027] Obtaining the temperature at the output end of the catalytic burner in real time;

[0028] Calculating the temperature change rate of the output end of the catalytic burner according to the temperatures at the output end of the catalytic burner obtained at different times;

[0029] If the temperature change rate of the output end of the catalytic burner is greater than the set temperature rise rate, it is determined that the catalytic burner starts successfully; if the temperature change rate of the output end of the catalytic burner is less than or equal to the set temperature rise rate, it is determined that the catalytic burner starts unsuccessfully, where the set temperature rise rate is greater than zero.

[0030] Optionally, the fuel cell system includes a third fuel supplier, and the third fuel supplier is connected to the second-stage fuel cell stack;

[0031] After controlling the output power of the second-stage fuel cell stack to gradually increase, it includes:

[0032] Controlling the third fuel supplier to output fuel to the second-stage fuel cell stack, and controlling the flow rate of the fuel output by the third fuel supplier to gradually increase.

[0033] Optionally, after both the first-stage fuel cell stack and the second-stage fuel cell stack are operating at full load, the control method for the stable operation of the fuel cell system further includes:

[0034] After receiving an instruction to reduce the output power of the fuel cell, controlling the flow rates of the fuels output by the first fuel supplier and the third fuel supplier to both decrease;

[0035] Controlling the output power of the first-stage fuel cell stack to decrease, and controlling the output power of the second-stage fuel cell stack to decrease.

[0036] Optionally, the fuel cell system further includes a cathode exhaust gas mixer. A first input end of the cathode exhaust gas mixer is connected to an output end of the first-stage fuel cell stack. An output end of the cathode exhaust gas mixer is connected to an input end of the second-stage fuel cell stack. A second input end of the cathode exhaust gas mixer is configured to input air.

[0037] The cold start preheating process further includes:

[0038] Controlling the flow rate of the air input into the cathode exhaust gas mixer so that the temperature of the gas output by the catalytic combustor is equal to a set outlet temperature.

[0039] The fuel cell system further includes a cooler and a gas-water separator. An input end of the cooler is connected to an output end of the first-stage fuel cell stack. An output end of the cooler is connected to an input end of the gas-water separator. An output end of the gas-water separator is connected to an input end of the second-stage fuel cell stack.

[0040] After both the first-stage fuel cell stack and the second-stage fuel cell stack operate at full load, the control method for the stable operation of the fuel cell system further includes:

[0041] Increasing the power of the cooler to reduce the water content of the anode exhaust gas of the second-stage fuel cell stack.

[0042] In the technical solution of the embodiment of the present invention, after controlling the fuel cell system to complete the cold start preheating process, the output power of the fuel cell system is controlled to be adjusted. When adjusting the output power, the output power of the first-stage fuel cell stack is controlled to gradually increase to a first rated output power, and the output power of the second-stage fuel cell stack is controlled to gradually decrease, so that in the initial stage of fuel cell combustion power generation, since the output power of the first-stage fuel cell stack is small, the unburned fuel can enter the second-stage fuel cell stack for full combustion, improving the utilization rate of the fuel in the fuel cell, and at the same time ensuring the smooth adjustment of the power of the first-stage fuel cell stack and the second-stage fuel cell stack, and improving the stability of the system.

[0043] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0045] Figure 1It is a schematic structural diagram of a fuel cell system provided by an embodiment of the present invention;

[0046] Figure 2 It is a flowchart of a control method for stable operation of a fuel cell system provided by an embodiment of the present invention;

[0047] Figure 3 It is a flowchart of another control method for stable operation of a fuel cell system provided by an embodiment of the present invention;

[0048] Figure 4 It is a flowchart of another control method for stable operation of a fuel cell system provided by an embodiment of the present invention. Detailed implementation manners

[0049] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0050] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0051] Figure 1 It is a schematic structural diagram of a fuel cell system provided by an embodiment of the present invention, Figure 2 It is a flowchart of a control method for stable operation of a fuel cell system provided by an embodiment of the present invention. This embodiment is applicable to the situation of controlling the combustion and power generation of a fuel cell system. The control method for stable operation of a fuel cell system is used to control the fuel cell system. Refer to Figure 1 and Figure 2, a fuel cell system includes a fuel cell, a first fuel supplier 10, an evaporator 11, and a liquid water supplier 12. The fuel cell includes a first-stage stack 13 and a second-stage stack 14. The output end of the first fuel supplier 10 is connected to the first input end of the evaporator 11. The output end of the liquid water supplier 12 is connected to the second input end of the evaporator 11. The output end of the evaporator 11 is connected to the input end of the first-stage stack 13. The output end of the first-stage stack 13 is connected to the input end of the second-stage stack 14. As Figure 2 shown, the method includes:

[0052] S110: Control the fuel cell system to complete the cold start preheating process.

[0053] When the fuel cell generates electricity by combustion, in addition to supplying reaction raw materials such as methane and water to the fuel cell, it is also necessary to make the reaction raw materials input to the fuel cell have a certain temperature. The cold start preheating process is a process of heating the reaction raw materials, that is, fuel and water. Optionally, the fuel cell system further includes a first-stage reformer 15, and the first-stage reformer 15 is connected between the output end of the evaporator 11 and the input end of the first-stage stack 13. Exemplarily, the first-stage reformer 15 may include a heating device. Before the first fuel supplier 10 outputs fuel and the liquid water supplier 12 outputs water, the heating device in the first-stage reformer 15 can be turned on to heat the first-stage reformer 15, so that after the subsequent fuel and water are heated in the first-stage reformer 15, they are input into the first-stage stack 13.

[0054] Control the fuel cell system to perform output power regulation. Controlling the fuel cell system to perform output power regulation includes:

[0055] S120: Control the first fuel supplier to input fuel into the evaporator, and control the liquid water supplier to input water into the evaporator, so that the fuel and water output by the evaporator sequentially enter the first-stage stack and the second-stage stack, and the output powers of both the first-stage stack and the second-stage stack are zero.

[0056] After the temperature in the first - stage reformer 15 reaches the set reforming temperature, the fuel cell system completes the cold - start preheating process. Control the first fuel supplier 10 to input fuel such as methane into the evaporator, and control the liquid - water supplier 12 to input water into the evaporator 11. The evaporator 11 is used to convert liquid water into gas and then transport it to the first - stage reformer 15 together with the fuel. After water and methane are heated in the first - stage reformer 15, they are input into the first - stage fuel cell stack 13 and the second - stage fuel cell stack 14 to carry out electrochemical reactions to generate electric energy. Among them, a first valve F1 is connected between the output end of the first fuel supplier 10 and the first input end of the evaporator 11 to control whether the first fuel supplier 10 outputs fuel. A second valve F2 is connected between the output end of the liquid - water supplier 12 and the second input end of the evaporator 11 to control whether the liquid - water supplier 12 outputs water. In the initial stage of the system power generation, after fuel and water are introduced into the first - stage fuel cell stack 13 and the second - stage fuel cell stack 14, set the output power of the first - stage fuel cell stack and the second - stage fuel cell stack to zero, and the fuel cell stacks do not output electric energy externally to adapt to the initial power - generation stage of the system.

[0057] S130: Control the output power of the first - stage fuel cell stack to gradually increase to the first rated output power, and control the output power of the second - stage fuel cell stack to gradually decrease from the second rated output power to the set value.

[0058] In the initial stage of controlling the output - power regulation of the fuel cell system, the supply of fuel and water is unstable. And to ensure the stability of the system output power, set the first - stage fuel cell stack 13 to output a load at a low power, and maintain the first - stage fuel cell stack 13 in a low - load operation state. Because the output power of the first - stage fuel cell stack 13 is small, a large amount of the fuel entering the first - stage fuel cell stack 13 has not undergone a combustion reaction. Therefore, the output power of the second - stage fuel cell stack 14 can be set to be larger to burn the unburned fuel in the first - stage fuel cell stack 13 again, improving the fuel utilization rate of the system. As the fuel - cell combustion - power - generation process progresses, gradually increase the output power of the first - stage fuel cell stack 13 until the first - stage fuel cell stack 13 tends to operate at full load, and the output power of the second - stage fuel cell stack 14 decreases accordingly.

[0059] The technical solution of the embodiment of the present invention controls the output - power regulation of the fuel cell system after the cold - start preheating process of the fuel cell system is completed. When performing output - power regulation, control the output power of the first - stage fuel cell stack to gradually increase to the first rated output power, and control the output power of the second - stage fuel cell stack to gradually decrease to the set value, so that in the initial stage of the fuel - cell combustion - power - generation, due to the small output power of the first - stage fuel cell stack, the unburned fuel can enter the second - stage fuel cell stack for full combustion, improving the fuel utilization rate in the fuel cell, and at the same time ensuring the smooth regulation of the power of the first - stage fuel cell stack and the second - stage fuel cell stack, improving the stability of the system.

[0060] Figure 3The flowchart of another control method for the stable operation of the fuel cell system provided by the embodiment of the present invention is referred to Figure 1 and Figure 3 , optionally, the fuel cell system further includes a flame burner 16, a catalytic burner 17, an air preheater 18, a first-stage reformer 15 and a second fuel supplier 19. The first input end of the flame burner 16 is connected to the output end of the second-stage fuel cell stack 14, the output end of the flame burner 16 is connected to the input end of the catalytic burner 17, the output end of the catalytic burner 17 is connected to the first input end of the air preheater 18, the second input end of the air preheater 18 is used to input air, the first output end of the air preheater 18 is connected to the first input end of the first-stage reformer 15, the second output end of the air preheater 18 is connected to the third input end of the evaporator 11, the output end of the evaporator 11 is connected to the second input end of the first-stage reformer 15, the output end of the first-stage reformer 15 is connected to the input end of the first-stage fuel cell stack 13, and the output end of the second fuel supplier 19 is connected to the second input end of the flame burner 16. Both the first fuel cell stack 13 and the second fuel cell stack 14 include an anode, an electrolyte and a cathode. The output end of the first-stage reformer 15 includes a first output end and a second output end. When the output end of the first-stage reformer 15 is connected to the input end of the first-stage fuel cell stack 13, the first output end of the first-stage reformer 15 is connected to the cathode of the first-stage fuel cell stack 13, and the second output end of the first-stage reformer 15 is connected to the cathode of the first-stage fuel cell stack 13. The anode of the first-stage fuel cell stack 13 is directly or indirectly connected to the anode of the second-stage fuel cell stack 14, the cathode of the first-stage fuel cell stack 13 is directly or indirectly connected to the cathode of the second-stage fuel cell stack 14, and both the anode and the cathode of the second-stage fuel cell stack 14 are connected to the first input end of the flame burner 16. Wherein, the first input end and the first output end of the first-stage reformer 15 are communicated to transport the air conveyed by the air preheater 18, and the second input end and the second output end of the first-stage reformer 15 are communicated to transport the fuel and water output by the evaporator 11.

[0061] The control method for the stable operation of the fuel cell system includes:

[0062] S111: Control the second fuel supplier to supply fuel to the flame burner.

[0063] The second fuel supplier 19 is used to supply the fuel required for combustion to the flame burner 16. Optionally, a third valve F3 is connected between the output end of the second fuel supplier 19 and the second input end of the flame burner 16, and the third valve F3 is used to control whether the second fuel supplier 19 outputs fuel. By controlling the opening of the third valve F3, the second fuel supplier 19 is controlled to supply fuel to the flame burner 16.

[0064] S121: Control the start of the flame burner to cause the fuel to burn in the flame burner.

[0065] The fuel cell system further includes a pulse igniter, which is connected to the flame burner 16 and is used to release a pulse voltage to complete ignition at the flame burner 16 to start the flame burner 16.

[0066] S131: Control the gas output after the flame burner burns and input it into the air preheater through the catalytic burner until the gas in the air preheater heats the temperature of the first-stage reformer to a first set temperature, where the temperature of the gas output after the flame burner burns is less than the ignition temperature of the catalytic burner.

[0067] The temperature of the gas output after the flame burner burns is less than the ignition temperature of the catalytic burner, which can prevent the flame burner 17 from starting and only start the flame burner 16. After the exhaust gas output after the flame burner 16 burns passes through the catalytic burner 17 to the air preheater 18, it heats the external air input into the air preheater 18, so that the hot air enters the first-stage reformer 15 to increase the temperature in the first-stage reformer 15. Until the temperature in the first-stage reformer 15 reaches the first set temperature, enter S141, control the first fuel supply device 10 and the liquid water supply device 12 to open, and input fuel and water into the first-stage reformer 15, so that the hot air input into the first-stage reformer 15 exchanges heat with methane and water in the first-stage reformer 15. At the same time, control the heated gas in the air preheater 18 to enter the evaporator 11 to heat the evaporator 11 to complete the conversion of liquid water to gaseous water. The air after heat exchange enters the cathode of the first-stage fuel cell stack 13, and the fuel and water after heat exchange enter the anode of the first-stage fuel cell stack 13.

[0068] The hot gas after the flame burner 14 burns is transmitted to the air preheater 18 and the evaporator 11 for heating the corresponding devices, improving the utilization rate of the gas after burning in the flame burner 14 and the fuel utilization rate of the entire system.

[0069] S141: Control the first fuel supply device to input fuel into the evaporator, and control the liquid water supply device to input water into the evaporator, so that the fuel and water output by the evaporator enter the first-stage fuel cell stack and the second-stage fuel cell stack in sequence, and the output powers of the first-stage fuel cell stack and the second-stage fuel cell stack are both zero.

[0070] S151: Control the output power of the first-stage fuel cell stack to gradually increase to the first rated output power, and control the output power of the second-stage fuel cell stack to gradually decrease from the second rated output power to a set value.

[0071] Reference Figure 2, Optionally, the fuel cell system further includes a cooler 24 and a gas-water separator 25. The input end of the cooler 24 is connected to the output end of the first-stage fuel cell stack 15, the output end of the cooler 24 is connected to the input end of the gas-water separator 25, and the output end of the gas-water separator 25 is connected to the input end of the second-stage fuel cell stack 16. The fuel cell system further includes a second-stage reformer 20, a mixer 21, a check valve 24, and a power device 25. The first input end of the second-stage reformer 20 is connected to the anode of the first-stage fuel cell stack 13, the first output end of the second-stage reformer 20 is connected to the input end of the cooler 22, the output end of the cooler 22 is connected to the input end of the gas-water separator 23, the first output end of the gas-water separator 23 is connected to the second input end of the evaporator 11 through the power device, and the first output end of the gas-water separator 23 is also connected to the drain valve F0. The second output end of the gas-water separator 23 is connected to the first input end of the mixer 21 through the check valve 24. The output end of the mixer 21 is connected to the second input end of the second-stage reformer 20, and the second output end of the second-stage reformer 20 is connected to the anode of the second fuel cell stack 14.

[0072] The content of combustible components in the anode exhaust gas of the first-stage fuel cell stack 13 is relatively high. After controlling the anode exhaust gas to be dehydrated by the second-stage reformer 20, the cooler 22, and the gas-water separator 23, it enters the second-stage reformer 20 through the check valve 24 and the mixer 21 to complete the consumption conversion at the second-stage fuel cell stack 14. The anode exhaust gas can heat the second-stage reformer 20 to adjust the temperature of the gas in the second-stage reformer. Since the water output by the gas-water separator 23 can be input into the evaporator 11, the supply of liquid water from the liquid water supplier 12 to the evaporator 11 can be controlled to stop by controlling the second valve F2 to close, improving the utilization rate of the anode exhaust gas and saving energy. If there is too much water in the gas-water separator 23, it can be discharged from the fuel cell system through the drain valve F0.

[0073] Figure 4 It is a flowchart of another control method for the stable operation of the fuel cell system provided by the embodiment of the present invention. Refer to Figure 1 and Figure 4 , On the basis of the above embodiments, optionally, the fuel cell system further includes a cathode exhaust gas mixer 26 and a third fuel supplier 27. The first input end of the cathode exhaust gas mixer 26 is connected to the cathode of the first-stage fuel cell stack 13, the output end of the cathode exhaust gas mixer 26 is connected to the cathode of the second-stage fuel cell stack 14, and the second input end of the cathode exhaust gas mixer 26 is used to input external air. The third fuel supplier 27 is connected to the second-stage fuel cell stack 14. Specifically, the output end of the third fuel supplier 27 is connected to the second input end of the mixer 21, and the third fuel supplier 27 is connected to the input end of the second-stage fuel cell stack 14 through the mixer 21 and the second-stage reformer 20. The control method includes:

[0074] S112: Control the second fuel supplier to supply fuel to the flame burner.

[0075] S122: Control the flame burner to start, so that the fuel burns in the flame burner.

[0076] S132: Control the gas output after the flame burner burns to be input into the air preheater through the catalytic burner until the gas in the air preheater heats the temperature of the first-stage reformer to the first set temperature.

[0077] Optionally, the cold start preheating process further includes:

[0078] Control the flow rate of the air input into the cathode exhaust gas mixer 26 so that the temperature of the gas output by the catalytic burner 17 is equal to the set outlet temperature. The temperature at the output end of the catalytic burner 17 is maintained at the set outlet temperature, and the temperature at the output end of the catalytic burner 17 is adjusted by adjusting the flow rate of the air input into the cathode exhaust gas mixer 26. Exemplarily, when the temperature at the output end of the catalytic burner 17 is greater than the set outlet temperature, control the flow rate of the air input into the cathode exhaust gas mixer 26 to increase to reduce the temperature at the output end of the catalytic burner 17.

[0079] S142: Control the first fuel supplier to supply fuel to the evaporator, and control the liquid water supplier to supply water to the evaporator, so that the fuel and water output by the evaporator enter the first-stage fuel cell stack and the second-stage fuel cell stack in sequence, and the output power of both the first-stage fuel cell stack and the second-stage fuel cell stack is zero.

[0080] S152: Control the output power of the first-stage fuel cell stack to gradually increase to the first rated output power, and control the output power of the second-stage fuel cell stack to gradually decrease from the second rated output power to the set value.

[0081] When the fuel cell system adjusts its output power, the output power of the first-stage fuel cell stack 13 is increased to make the first-stage fuel cell stack 13 tend to operate at full load, and the output power of the second-stage fuel cell stack 14 is decreased. Since the fuel utilization rates of the first-stage fuel cell stack 13 and the second-stage fuel cell stack 14 are too high, the calorific value of the fuel entering the flame burner 16 decreases, and the phenomenon of sudden flame extinction of the flame burner is likely to occur. Therefore, it is necessary to determine whether the flame burner extinguishes when the fuel cell system adjusts its output power. Optionally, determining that the flame burner extinguishes includes: obtaining the temperature at the output end of the flame burner in real time; calculating the temperature change rate at the output end of the flame burner according to the temperatures at the output end of the flame burner obtained at different times; if the temperature change rate at the output end of the flame burner is less than or equal to the set decay rate, it is determined that the flame burner extinguishes, where the set decay rate is less than zero. A temperature sensor can be set at the output end of the flame burner 16 to obtain the temperature at the output end of the flame burner 16 in real time. If the temperature change rate at the output end of the flame burner 16 is less than or equal to the set decay rate, it indicates that the temperature at the output end of the flame burner 16 is rapidly decreasing, further indicating that the flame burner 16 extinguishes and cannot generate a large amount of heat through combustion.

[0082] S162: When controlling the fuel cell system to adjust its output power, after determining that the flame burner extinguishes, obtain the temperature at the output end of the catalytic burner at different times within a preset time.

[0083] Within the set time after the flame burner extinguishes, obtain the temperature at the output end of the catalytic burner 17 every set number of seconds.

[0084] S172: Determine whether the catalytic burner starts successfully according to the temperatures at the output end of the catalytic burner obtained at different times.

[0085] After the flame burner 16 is extinguished, when the temperature of the gas entering the catalytic burner 17 reaches a certain temperature, the catalytic burner 17 can be triggered to start, and the combustible components in the tail gas of the fuel cell are burned. Optionally, determining whether the catalytic burner 17 starts successfully according to the temperature at the output end of the catalytic burner 17 obtained at different times includes: obtaining the temperature at the output end of the catalytic burner 17 in real time; calculating the temperature change rate at the output end of the catalytic burner 17 according to the temperature at the output end of the catalytic burner 17 obtained at different times; if the temperature change rate at the output end of the catalytic burner 17 is greater than the set temperature rise rate, it is determined that the catalytic burner 17 starts successfully, and if the temperature change rate at the output end of the catalytic burner 17 is less than or equal to the set temperature rise rate, it is determined that the catalytic burner 17 starts unsuccessfully, where the set temperature rise rate is greater than zero. A temperature sensor is provided at the output end of the catalytic burner 17, and the temperature at the output end of the catalytic burner 17 is obtained through the temperature sensor. When the temperature change rate at the output end of the catalytic burner 17 is greater than the set temperature rise rate, it indicates that the temperature at the output end of the catalytic burner 17 rises sharply, further indicating that the catalytic burner 17 starts successfully, and the combustible components burn in the catalytic burner 17, causing the temperature at the output end of the catalytic burner 17 to rise.

[0086] S182: If it is determined that the catalytic burner starts successfully, then control the output power of the second-stage stack to gradually increase until both the first-stage stack and the second-stage stack are operating at full load.

[0087] If the catalytic burner 17 starts successfully, the combustible components in the tail gas generated by the fuel cell combustion can still be burned and reused through the catalytic burner 17. Therefore, the output power of the second-stage stack 14 can be increased, so that even if the fuel input to the second-stage stack 14 increases, the unburned fuel can still be burned and reused through the catalytic burner 17, ensuring that the second-stage stack 14 can have a large output power, and at the same time, the fuel utilization rate of the entire system is also high.

[0088] S192: Control the third fuel supply device to output fuel to the second-stage stack, and control the flow rate of the fuel output by the third fuel supply device to gradually increase.

[0089] Based on the above embodiments, the third fuel supply device 27 is connected to the second-stage stack 14 through the mixer 21 and the second-stage reformer 20. A fourth valve F4 is also connected between the output end of the third fuel supply device 27 and the second input end of the mixer 21, and the fourth valve F4 is used to control whether the third fuel supply device 27 outputs fuel. When the output power of the second-stage stack 14 gradually increases, the flow rate of the fuel input to the second-stage stack 14 should be gradually increased through the third fuel supply device 27 to ensure that the flame burner 16 will not suddenly ignite due to excessive fuel replenishment, and the system always operates with the catalytic burner 17 in the startup state.

[0090] S202: If it is determined that the catalytic combustor fails to start, control the fuel cell system to shut down and input air into the second stack.

[0091] When the catalytic combustor 17 also fails to start after the flame burner 16 goes out, control the entire system to shut down, such as controlling the first fuel supplier 10, the second fuel supplier 19, and the third fuel supplier 27 to stop outputting fuel, and controlling the cathode exhaust gas mixer 26 to input external air into the second stack 14 for purging.

[0092] Continue to refer to Figure 2 and Figure 4 Optionally, after both the first stack 13 and the second stack 14 are operating at full load, the control method for the stable operation of the fuel cell system further includes:

[0093] After receiving an instruction to reduce the output power of the fuel cell, control the flow rates of the fuel output by the first fuel supplier 10 and the third fuel supplier 27 to decrease; control the output power of the first stack 13 to decrease, and control the output power of the second stack 14 to decrease.

[0094] After the first stack 13 and the second stack 14 have been operating at full load for a set time, the power required to be output by the fuel cell changes. Exemplarily, the power required to be output by the fuel cell decreases. After receiving an instruction to reduce the output power of the fuel cell, the flow rates of the fuel output by the first fuel supplier 10 and the third fuel supplier 27 should be reduced first, and then the output powers of the first stack 13 and the second stack 14 should be reduced to avoid sudden ignition of the flame burner 16 caused by the lag in the control of the flow rate of the output fuel, avoid fluctuations in the exhaust gas flow rate, and improve system stability.

[0095] After both the first stack 13 and the second stack 14 are operating at full load, the control method for the stable operation of the fuel cell system further includes:

[0096] Increase the power of the cooler 24 to enhance the cooling effect of the cooler, so as to reduce the water content of the anode exhaust gas of the second stack 16. At the same time, increase the opening degree of the drain valve F0 to reduce the water content of the anode exhaust gas of the first stack 13 entering the mixer 21, and further reduce the water content of the anode exhaust gas of the second stack 14, so as to avoid excessive water content in the fluid entering the flame burner 16 and the catalytic combustor 17 from the anode exhaust gas of the second stack 14, resulting in a relatively high chromium emission in the flame burner 16 and the catalytic combustor 17.

[0097] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is made herein.

[0098] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A control method for stable operation of a fuel cell system, characterized in that: Used to control a fuel cell system, the fuel cell system comprising a fuel cell, a first fuel supplier, an evaporator and a liquid water supplier, the fuel cell comprising a first-stage stack and a second-stage stack, the output end of the first fuel supplier being connected to the first input end of the evaporator, the output end of the liquid water supplier being connected to the second input end of the evaporator, the output end of the evaporator being connected to the input end of the first-stage stack, and the output end of the first-stage stack being connected to the input end of the second-stage stack; The control method for stable operation of the fuel cell system comprises: Controlling the fuel cell system to complete a cold start preheating process; Controlling the fuel cell system to adjust output power; The controlling the fuel cell system to adjust the output power includes: Controlling the first fuel supplier to input fuel to the evaporator, and controlling the liquid water supplier to input water to the evaporator, so that the fuel and water output by the evaporator enter the first-stage battery stack and the second-stage battery stack in sequence, and the output power of the first-stage battery stack and the second-stage battery stack are both zero; The output power of the first-stage fuel cell stack is controlled to gradually increase to a first rated output power, and the output power of the second-stage fuel cell stack is controlled to gradually decrease from a second rated output power to a set value.

2. The method for controlling stable operation of a fuel cell system according to claim 1, characterized in that: The fuel cell system further comprises a flame burner, a catalytic burner, an air preheater, a first-stage reformer and a second fuel supplier, wherein the first input end of the flame burner is connected to the output end of the second-stage stack, the output end of the flame burner is connected to the input end of the catalytic burner, the output end of the catalytic burner is connected to the first input end of the air preheater, the first output end of the air preheater is connected to the first input end of the first-stage reformer, the second input end of the air preheater is used to input air, the second output end of the air preheater is connected to the third input end of the evaporator, the output end of the evaporator is connected to the second input end of the first-stage reformer, the output end of the first-stage reformer is connected to the input end of the first-stage stack, and the output end of the second fuel supplier is connected to the second input end of the flame burner; The controlling the fuel cell system to complete the cold start preheating process comprises: controlling the second fuel supplier to supply fuel to the flame burner; Controlling the flame burner to start, so that the fuel burns in the flame burner; The gas output from the flame burner after combustion is controlled to be input into the air preheater through the catalytic burner until the gas in the air preheater heats the temperature of the first-stage reformer to a first set temperature, wherein the temperature of the gas output from the flame burner after combustion is lower than the ignition temperature of the catalytic burner.

3. The method for controlling stable operation of a fuel cell system according to claim 2, characterized in that: When controlling the fuel cell system to adjust the output power, after determining that the flame burner is extinguished, obtaining the temperature of the output end of the catalytic burner at different times within a preset time; Judging whether the catalytic burner is started successfully according to the temperature of the output end of the catalytic burner obtained at different times; If it is determined that the catalytic burner is successfully started, the output power of the second-stage fuel cell stack is controlled to gradually increase until both the first-stage fuel cell stack and the second-stage fuel cell stack are running at full load.

4. The method for controlling stable operation of a fuel cell system according to claim 3, characterized in that: After judging whether the catalytic burner is successfully started according to the temperature of the output end of the catalytic burner obtained at different times, the method further includes: If it is determined that the catalytic burner fails to start, the fuel cell system is controlled to shut down and air is input into the second-stage fuel cell stack.

5. The method for controlling stable operation of a fuel cell system according to claim 3, characterized in that: The step of determining that the flame burner is extinguished comprises: Acquire the temperature of the output end of the flame burner in real time; Calculating the temperature change rate of the output end of the flame burner according to the temperature of the output end of the flame burner obtained at different times; If the temperature change rate of the output end of the flame burner is less than or equal to a set decay rate, it is determined that the flame burner is extinguished, wherein the set decay rate is less than zero.

6. The method for controlling stable operation of a fuel cell system according to claim 3, characterized in that: The step of judging whether the catalytic burner is successfully started according to the temperature of the output end of the catalytic burner obtained at different times includes: Acquiring the temperature of the output end of the catalytic burner in real time; Calculating the temperature change rate of the output end of the catalytic burner according to the temperature of the output end of the catalytic burner obtained at different times; If the temperature change rate of the output end of the catalytic burner is greater than the set temperature rise rate, it is determined that the catalytic burner is started successfully; if the temperature change rate of the output end of the catalytic burner is less than or equal to the set temperature rise rate, it is determined that the catalytic burner fails to start, wherein the set temperature rise rate is greater than zero.

7. The method for controlling stable operation of a fuel cell system according to claim 3, characterized in that: The fuel cell system includes a third fuel supplier, and the third fuel supplier is connected to the second-stage fuel cell stack; After controlling the output power of the second-stage stack to gradually increase, the method further comprises: The third fuel supplier is controlled to output fuel to the second-stage fuel cell stack, and the flow rate of the fuel output by the third fuel supplier is controlled to gradually increase.

8. The method for controlling stable operation of a fuel cell system according to claim 7, characterized in that: After the first-stage fuel cell stack and the second-stage fuel cell stack are both running at full load, the control method for stable operation of the fuel cell system further includes: After receiving an instruction to reduce the output power of the fuel cell, controlling the flow rates of the fuel outputted by the first fuel supplier and the third fuel supplier to decrease; The output power of the first-stage fuel cell stack is controlled to decrease, and the output power of the second-stage fuel cell stack is controlled to decrease.

9. The method for controlling stable operation of a fuel cell system according to claim 2, characterized in that: It also includes a cathode tail gas mixer, wherein a first input end of the cathode tail gas mixer is connected to an output end of the first-stage stack, an output end of the cathode tail gas mixer is connected to an input end of the second-stage stack, and a second input end of the cathode tail gas mixer is used to input air; The cold start preheating process further includes: The flow rate of the air input into the cathode tail gas mixer is controlled so that the temperature of the gas output by the catalytic burner is equal to the set outlet temperature.

10. The method for controlling stable operation of a fuel cell system according to claim 3, characterized in that: The fuel cell system further includes a cooler and a gas-water separator, wherein the input end of the cooler is connected to the output end of the first-stage stack, the output end of the cooler is connected to the input end of the gas-water separator, and the output end of the gas-water separator is connected to the input end of the second-stage stack; After the first-stage fuel cell stack and the second-stage fuel cell stack are both running at full load, the control method for stable operation of the fuel cell system further includes: The power of the cooler is increased to reduce the water content of the anode tail gas of the second-stage fuel cell stack.

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