Fuel cell system cold-heat coolant mixed temperature control method

Abstract

The application discloses a fuel cell system cold-heat coolant mixed temperature control method and relates to the technical field of fuel cell system temperature control. The fuel cell system cold-heat coolant mixed temperature control method provided by the application linearizes a control system by using a feedback linearization method, solves the nonlinear characteristics of the system, then further theoretically feeds forward the fuel cell system operating conditions, improves the response speed of the system in response to the change of the fuel cell operating conditions, and finally performs closed-loop feedback control based on temperature control errors. Thanks to the feedback linearization that solves the nonlinear characteristics of the control system at this stage, compared with the case without feedback linearization, the control method can use stronger closed-loop feedback correction coefficients and obtain stronger closed-loop correction capabilities under the premise of ensuring the stability of system control, thereby solving the problem of weak system anti-interference capability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fuel cell system temperature control, and particularly relates to a fuel cell system cold-hot coolant mixing temperature control method. BACKGROUND

[0002] At present, most fuel cells have a suitable working temperature range that is obviously higher than the ambient temperature. In order to improve the power generation response speed of the fuel cell system, the fuel cell needs to be quickly operated in its suitable temperature range. In addition, under specific power generation and operating conditions, the fuel cell has an optimal temperature operating point. Controlling the fuel cell temperature as close as possible to the optimal temperature operating point is beneficial to improving the power generation efficiency and service life of the fuel cell.

[0003] Based on the above requirements, most fuel cell systems currently adopt a large-small circulation design scheme to improve the temperature rising rate of the fuel cell while ensuring the temperature control effect. When the large-small circulation design scheme is adopted, there is a temperature control stage of cold-hot coolant mixing. At the beginning of the cold-hot coolant mixing stage, the temperature of the coolant in the total circulation loop approaches or reaches the optimal operating temperature of the fuel cell, and the temperature of the large circulation coolant is equal to the ambient temperature. Then, by controlling the angle of the electronic thermostat, the cold-hot coolant is gradually mixed to achieve the goal of controlling the temperature of the fuel cell coolant. At this time, the radiator is not working and the temperature of the coolant in the total circulation loop is always higher than the temperature of the large circulation coolant. When the temperature of the large circulation coolant approaches or reaches the operating temperature of the fuel cell, the fuel cell temperature control cannot be achieved by only controlling the angle of the thermostat. At this time, the stage ends.

[0004] The temperature control system of the cold-hot coolant mixing stage is a nonlinear control system. If the commonly used linear system closed-loop control method, such as PID control, is directly used, the temperature stable and accurate control in this stage cannot be achieved, and problems such as large temperature fluctuation or slow response speed will occur. If open-loop control is used, the control accuracy and anti-interference ability cannot be guaranteed. In addition, due to the weak closed-loop regulation ability (under the condition that the nonlinear characteristics of the system are not solved, enhancing the closed-loop regulation ability of the system will lead to an increase in temperature control fluctuation or even instability), the anti-interference ability is relatively weak. When the control scheme is implemented, if the output power of the fuel cell system changes, there is still a possibility of large temperature fluctuation, and it needs a certain time to adjust and stabilize again. The effect of temperature control in this stage not only affects the performance of the fuel cell in this stage, but also may affect the temperature control effect during the switching process from cold-hot coolant mixing to the next stage (such as radiator cooling fan control). SUMMARY

[0005] The present application aims at the above-mentioned problems, and provides a fuel cell system cold-hot coolant mixed temperature control method, which solves the non-linear characteristics of the fuel cell system temperature control system in the cold-hot coolant mixing stage, improves the system response speed, ensures the stability and precision of the control, and has strong system robustness.

[0006] The technical solutions adopted by the present application are as follows.

[0007] A fuel cell system cold-hot coolant mixed temperature control method is applied to a fuel cell system, wherein the fuel cell system comprises a stack, a water pump, a heat dissipation device and a thermostat, the water outlet of the stack is connected with the water inlet of the water pump, the water outlet of the water pump is connected with the water inlet of the stack through the thermostat to form a small circulation loop, and the water outlet of the water pump is connected with the water inlet of the stack through the heat dissipation device and the thermostat to form a large circulation loop, and the temperature control method comprises the following steps.

[0008] A judgment step: setting a control target temperature Ts, collecting the total loop coolant temperature T1(t) and the large circulation loop coolant temperature T2(t) in real time, and issuing a temperature adjustment instruction by the control system when the total loop coolant temperature T1(t) is within the deviation range of the control target temperature Ts and the large circulation loop coolant temperature T2(t) is outside the deviation range of the control target temperature Ts.

[0009] Feedback control intermediate quantity calculation: after confirming the temperature adjustment instruction,

[0010] Calculate the temperature control error eT(t), and the calculation process of the temperature control error eT(t) is shown in the following formula (1):

[0011] eT(t)=Ts-T1(t) (1)

[0012] In formula 1, Ts is the set control target temperature, and T1(t) is the total loop coolant temperature;

[0013] Based on the temperature control error eT(t), the closed-loop control intermediate quantity u(t) is calculated by using a linear system control method. fb

[0014] Feedback control intermediate quantity linearization processing: calculate the temperature difference δT(t) between the total loop coolant and the large circulation loop coolant, and the calculation process of the temperature difference δT(t) is shown in the following formula (2):

[0015] δT(t)=T1(t)-T2(t) (2)

[0016] ​In formula 2, "T1(t)" is the total loop coolant temperature, and "T2(t)" is the large circulation loop coolant temperature;

[0017] Based on the closed-loop control intermediate variable u fb (t), the temperature difference δT(t) is calculated to achieve the large circulation flow percentage α(t) required for the mixed temperature of the cold and hot coolant to reach the target temperature Ts, and the calculation process of α(t) is shown in the following formula (3):

[0018] α(t) = u fb (t) / δT(t) (3)

[0019] In formula 3, "u fb (t)" is the closed-loop control intermediate variable, and "δT(t)" is the temperature difference between the coolant in the total loop and the coolant in the large circulation loop;

[0020] Thermostat opening degree adjustment: according to the large circulation flow percentage α(t) and the thermostat opening degree percentage relationship obtained by calibration, the opening degree percentage u(t x ) of the thermostat is calculated in real time, and the control system sends adjustment instructions to the thermostat to adjust the opening degree of the thermostat in real time.

[0021] Further, it further comprises

[0022] Feedforward control intermediate variable calculation: according to the operation of the fuel cell system, the total heat generation power Pst(t) in the fuel cell system is obtained, and the feedforward control intermediate variable u ff (t) is calculated based on the total heat generation power Pst(t), and the calculation process of the feedforward control intermediate variable u ff (t) is shown in the following formula (4):

[0023] u ff (t) = K ff ·Pst(t) (4)

[0024] In formula 4, "K ff " is the feedforward control system coefficient, and "Pst(t)" is the total heat generation power in the fuel cell system;

[0025] In the feedback control intermediate variable linearization process, the calculation process of α(t) is shown in the following formula (5):

[0026] α(t) = u fb (t) / δT(t) + u ff (t) / δT(t) (5)

[0027] In formula 5, "u fb (t)" is the closed-loop control intermediate variable, "δT(t)" is the temperature difference between the coolant in the total loop and the coolant in the large circulation loop, and "uff (t) is an intermediate quantity of feedforward control.

[0028] Further, in the calculation of the intermediate quantity of feedback control, the intermediate quantity of closed-loop control u fb (t) before linearization is calculated by PID control. fb (t) is calculated as shown in the following formula (6):

[0029]

[0030] In formula 6, "K p " is the proportional coefficient of PID control, "T i " is the integral time constant of PID control, "τ" is the differential time constant of PID control, and "eT(t)" is the temperature control error.

[0031] Further, in the calculation of the intermediate quantity of feedforward control, the feedforward control coefficient K ff is calculated by calculation. ff The calculation process of the feedforward control coefficient K ff is shown in the following formula (7):

[0032] K ff = 1 / (Wc·Ccool) (7)

[0033] In formula 7, "Wc" is the mass flow of the cooling liquid in the total circuit, and "Ccool" is the specific heat capacity of the cooling liquid.

[0034] Further, in the judgment step, the deviation range of the control target temperature Ts is ±2℃.

[0035] Further, the small circulation circuit comprises a branch section, a heat generation section, and a merging section, the heat generation section is arranged between the branch section and the merging section; the large circulation circuit comprises a branch section, a heat dissipation section, and a merging section, the heat dissipation section is arranged between the branch section and the merging section, and the heat dissipation device is arranged in the heat dissipation section; the water inlet of the stack is connected with the merging section, and the water outlet is connected with the branch section, the heat generation section in the small circulation circuit and the heat dissipation section in the large circulation circuit are connected in parallel, and the heat generation section, the heat dissipation section, and the merging section are connected with the thermostat.

[0036] Further, the heat generation device is arranged on the heat generation section.

[0037] Further, the heat generation device is arranged on the heat generation section.

[0038] Further, the fuel cell system is provided with a first temperature sensor, which collects the temperature T1 of the cooling liquid in the total circuit in real time, and the first temperature sensor is arranged on the branch section and / or the heat generation section.

[0039] Further, the fuel cell system is provided with a second temperature sensor, which collects the temperature T2 of the cooling liquid in the large circulation loop in real time, and the second temperature sensor is arranged in the heat dissipation section.

[0040] In summary, due to the adoption of the above technical solutions, the present application has the following advantages:

[0041] The present application firstly performs mathematical modeling on the control system, linearizes the control system by using the feedback linearization method, solves the nonlinear characteristics of the system, then further performs theoretical feedforward according to the operating conditions of the fuel cell system, improves the response speed of the system to the changes of the operating conditions of the fuel cell system, and finally performs closed-loop feedback control based on the temperature control error. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a schematic diagram of the circulation process of the fuel cell system of the present application;

[0043] Figure 2 is a control flow chart of the temperature control method of the hot and cold cooling liquids of the fuel cell system of the present application without feedforward control;

[0044] Figure 3 is a control flow chart of the temperature control method of the hot and cold cooling liquids of the fuel cell system of the present application with feedforward control;

[0045] Figure 4 is a comparison chart of the temperature control effects under different power generations of the present application;

[0046] Figure 5 is an influence chart of the change of the ambient temperature of the present application;

[0047] Figure 6 is an influence chart of the change of the control target temperature of the present application;

[0048] Figure 7 is an actual control effect chart of the present application applied to a certain type of fuel cell system test bench.

[0049] Marked in the figure: 1 - stack, 2 - water pump, 3 - heat dissipation device, 4 - thermostat, 5 - heat generating device, 6 - heat generating device, 7 - shunt section, 8 - combined section, 9 - heat generating section, 10 - heat dissipation section, 11 - first temperature sensor, 12 - second temperature sensor. DETAILED DESCRIPTION

[0050] The application will be described in further detail below with reference to the drawings.

[0051] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0052] Example 1

[0053] A fuel cell system cold-heat coolant mixed temperature control method, as shown in Figures 1-2 , applied to a fuel cell system, the fuel cell system comprising a stack 1, a water pump 2, a heat dissipation device 3 and a thermostat 4, the water outlet of the stack 1 is connected to the water inlet of the water pump 2, the water outlet of the water pump 2 is connected through the thermostat 4 and returns to the water inlet of the stack 1 to form a small circulation loop, the water outlet of the water pump 2 is connected through the heat dissipation device 3 and the thermostat 4 and returns to the water inlet of the stack 1 to form a large circulation loop, the temperature control method comprising:

[0054] Judgment step: set the control target temperature Ts, real-time acquisition of the total loop coolant temperature T1(t) and the large circulation loop coolant temperature T2(t), when the total loop coolant temperature T1(t) is within the deviation range of the control target temperature Ts and the large circulation loop coolant temperature T2(t) is outside the deviation range of the control target temperature Ts, the control system issues a temperature adjustment instruction.

[0055] Feedback control intermediate quantity calculation: after confirming the temperature adjustment instruction,

[0056] Calculate the temperature control error eT(t), the calculation process of the temperature control error eT(t) is shown in the following formula (1):

[0057] eT(t) = Ts - T1(t) (1)

[0058] In formula 1, "Ts" is the set control target temperature, "T1(t)" is the total loop coolant temperature;

[0059] Based on the temperature control error eT(t), the linear system control method is used to calculate the closed-loop control intermediate quantity u fb (t);

[0060] Feedback control intermediate variable linearization process: calculate the temperature difference δT(t) between the coolant in the total circuit and the coolant in the large cycle, the calculation process of the temperature difference δT(t) is shown in the following formula (2):

[0061] δT(t) = T1(t) - T2(t) (2)

[0062] In formula 2, “T1(t)” is the total circuit coolant temperature, and “T2(t)” is the large cycle circuit coolant temperature;

[0063] Based on the closed-loop control intermediate variable u fb (t), the temperature difference δT(t), calculate the large cycle flow percentage α(t) required to achieve the target temperature Ts of the mixed temperature of the cold and hot coolant, the calculation process of α(t) is shown in the following formula (3):

[0064] α(t) = u fb (t) / δT(t) (3)

[0065] In formula 3, “u fb (t)” is the closed-loop control intermediate variable, and “δT(t)” is the temperature difference between the coolant in the total circuit and the coolant in the large cycle;

[0066] Thermostat opening degree adjustment: according to the large cycle flow percentage α(t) and the thermostat 4 opening degree percentage relationship obtained by calibration, the opening degree percentage u(t x ) of the thermostat 4 is calculated in real time, and the control system sends adjustment instructions to the thermostat 4 to adjust the opening degree of the thermostat 4 in real time.

[0067] In the feedback control intermediate variable calculation, the closed-loop control intermediate variable u fb (t) before linearization includes but is not limited to being calculated by PID control, when PID control is used, the calculation process of the closed-loop control intermediate variable u fb (t) is shown in the following formula (6):

[0068]

[0069] In formula 6, “K p ” is the proportional coefficient of PID control, “T i ” is the integral time constant of PID control, “τ” is the differential time constant of PID control, and “eT(t)” is the temperature control error. In the judgment step, the deviation range of the control target temperature Ts is ±2℃.

[0070] The small circulation loop includes a branch section 7, a heat generation section 9, and a confluence section 8, with the heat generation section 9 located between the branch section 7 and the confluence section 8. The large circulation loop includes a branch section 7, a heat dissipation section 10, and a confluence section 8, with the heat dissipation section 10 located between the branch section 7 and the confluence section 8. The heat dissipation device 3 is located in the heat dissipation section 10. The inlet of the fuel cell stack 1 is connected to the confluence section 8, and the outlet is connected to the branch section 7. The heat generation section 9 in the small circulation loop and the heat dissipation section 10 in the large circulation loop are connected in parallel. The heat generation section 9, the heat dissipation section 10, and the confluence section 8 are connected to the thermostat 4.

[0071] The heat-generating section 9 is equipped with heat-generating equipment 6. The heat-generating equipment 6 includes, but is not limited to, a PTC heater.

[0072] The confluence section 8 is equipped with a heating device 5. The heating device 5 includes, but is not limited to, a DC-DC converter, an intercooler, etc.

[0073] The heat dissipation device 3 can be a radiator or a plate heat exchanger, etc.

[0074] The fuel cell system is equipped with a first temperature sensor 11, which collects the temperature T1 of the coolant in the main circuit in real time. The first temperature sensor 11 is located in the flow branch section 7.

[0075] The fuel cell system is equipped with a second temperature sensor 12, which collects the temperature T2 of the coolant in the large circulation loop in real time. The second temperature sensor 12 is located in the heat dissipation section 10.

[0076] Example 2

[0077] A method for controlling the mixing temperature of hot and cold coolants in a fuel cell system, such as Figure 1 , Figures 3-7 As shown, this is applied to a fuel cell system, which includes a fuel cell stack 1, a water pump 2, a heat dissipation device 3, and a thermostat 4. The outlet of the fuel cell stack 1 is connected to the inlet of the water pump 2. The outlet of the water pump 2 is connected to and returns to the inlet of the fuel cell stack 1 through the thermostat 4, forming a small loop. The outlet of the water pump 2 is connected to and returns to the inlet of the fuel cell stack 1 through the heat dissipation device 3 and the thermostat 4, forming a large loop. The temperature control method includes:

[0078] Judgment steps: Set the target temperature Ts, and collect the total loop coolant temperature T1(t) and the large loop coolant temperature T2(t) in real time. When the total loop coolant temperature T1(t) is within the deviation range of the target temperature Ts and the large loop coolant temperature T2(t) is outside the deviation range of the target temperature Ts, the control system issues a temperature adjustment command.

[0079] Feedforward control intermediate quantity calculation: according to the operation of the fuel cell system, the total heat generation power Pst(t) in the fuel cell system is obtained, and the feedforward control intermediate quantity u ff (t) is calculated based on the total heat generation power Pst(t) ff The calculation process of the feedforward control intermediate quantity u

[0080] u ff (t) = K ff ·Pst(t) (4)

[0081] In formula 4, “K ff ” is the coefficient of the feedforward control system, and “Pst(t)” is the total heat generation power in the fuel cell system;

[0082] Feedback control intermediate quantity calculation: after confirming the temperature adjustment instruction,

[0083] The temperature control error eT(t) is calculated, and the calculation process of the temperature control error eT(t) is shown in the following formula (1):

[0084] eT(t) = Ts-T1(t) (1)

[0085] In formula 1, “Ts” is the set control target temperature, and “T1(t)” is the total circuit coolant temperature;

[0086] Based on the temperature control error eT(t), the closed-loop control intermediate quantity u fb (t) is calculated by using a linear system control method;

[0087] Feedback control intermediate quantity linearization processing: the temperature difference δT(t) between the coolant in the total circuit and the coolant in the large circulation is calculated, and the calculation process of the temperature difference δT(t) is shown in the following formula (2):

[0088] δT(t) = T1(t)-T2(t) (2)

[0089] In formula 2, “T1(t)” is the total circuit coolant temperature, and “T2(t)” is the large circulation circuit coolant temperature;

[0090] Based on the closed-loop control intermediate quantity u fb (t) and the temperature difference δT(t), the large circulation flow percentage α(t) required to achieve the target temperature of the hot and cold coolant mixture temperature is calculated, and the calculation process of α(t) is shown in the following formula (5):

[0091] α(t) = u fb (t) / δT(t) + u ff (t) / δT(t) (5)

[0092] In formula 5, "u fb (t)" is a closed-loop control intermediate variable, "δT(t)" is a temperature difference between the coolant in the total circuit and the coolant in the large circulation, "u ff (t)" is a feedforward control intermediate variable.

[0093] Thermostat opening degree adjustment: according to the large circulation flow percentage α(t) and the thermostat 4 opening degree percentage relationship obtained through calibration, the thermostat 4 opening degree percentage u(t x ) is calculated in real time, and the control system sends an adjustment instruction to the thermostat 4 to adjust the opening degree of the thermostat 4 in real time.

[0094] In the calculation of the feedback control intermediate variable, the closed-loop control intermediate variable u fb (t) before linearization includes but is not limited to being calculated through PID control. When PID control is used, the calculation process of the closed-loop control intermediate variable u fb (t) is shown in the following formula (6):

[0095]

[0096] In formula 6, "K p " is the proportional coefficient of PID control, "T i " is the integral time constant of PID control, "τ" is the differential time constant of PID control, and "eT(t)" is the temperature control error. In the judgment step, the deviation range of the control target temperature Ts is ±2℃.

[0097] In the calculation of the feedforward control intermediate variable, the total heat generation power Pst(t) in the fuel cell system is first calculated, estimated or calibrated in real time according to the operating conditions of the fuel cell system. For example, the heat generation power of the stack and the DCDC can be calculated or estimated according to the polarization curve of the fuel cell and the efficiency of the DCDC, respectively.

[0098] The feedforward control coefficient K ff is calculated, and the calculation process of the feedforward control coefficient K ff is shown in the following formula (7):

[0099] K ff = 1 / (Wc·Ccool) (7)

[0100] In formula 7, "Wc" is the mass flow rate of the coolant in the total circuit, and "Ccool" is the specific heat capacity of the coolant. K ff It is not necessary to use a theoretical value, and it can also be obtained through debugging.

[0101] In thermostat opening adjustment, this embodiment obtains the functional relationship between the percentage of flow in the large circulation loop and the percentage of thermostat opening based on calibration data: f(x) = 0.0027 + 0.2468x + 0.3327x 2 +0.3783x 3 This functional relationship is not unique and varies depending on the thermostat used or the pressure drop between the large and small circulation loops in the design.

[0102] The percentage of the large circulation flow calculated at a certain time tx is α(t x If ), then at time t x Thermostat opening percentage at a certain moment t x The calculated percentage of the large circulation flow is α(t) x If ), then at time t x Thermostat opening percentage u(t) x As shown in equation (8):

[0103] u(t x )=0.0027+0.2468α(t x )+0.3327α 2 (t x )+0.3783α 3 (t x (8)

[0104] In Equation 8, “α(t x At a certain moment t x The calculated percentage of the large circulation flow.

[0105] The thermostat adjustment angle obtained by the above control method allows the hot and cold coolants in the large and small circulation loops to gradually mix. As the coolant in the large circulation loop gradually rises, it carries away the heat generated by the heat-generating equipment in the small circulation loop, ultimately achieving rapid, stable, and precise control of the coolant temperature in the total loop, i.e., rapid, stable, and precise control of the fuel cell stack temperature.

[0106] The small circulation loop includes a branch section 7, a heat generation section 9, and a confluence section 8, with the heat generation section 9 located between the branch section 7 and the confluence section 8. The large circulation loop includes a branch section 7, a heat dissipation section 10, and a confluence section 8, with the heat dissipation section 10 located between the branch section 7 and the confluence section 8. The heat dissipation device 3 is located in the heat dissipation section 10. The inlet of the fuel cell stack 1 is connected to the confluence section 8, and the outlet is connected to the branch section 7. The heat generation section 9 in the small circulation loop and the heat dissipation section 10 in the large circulation loop are connected in parallel. The heat generation section 9, the heat dissipation section 10, and the confluence section 8 are connected to the thermostat 4.

[0107] The heat production section 9 is provided with a heat production device 6. The heat production device 6 includes but is not limited to a PTC heater.

[0108] The confluence section 8 is provided with a heat production device 5. The heat production device 5 includes but is not limited to a DCDC, an intercooler, etc.

[0109] The heat dissipation device 3 can be a radiator or a plate heat exchanger, etc.

[0110] The fuel cell system is provided with a first temperature sensor 11, which collects the temperature T1 of the cooling liquid in the total circuit in real time. The first temperature sensor 11 is arranged in the shunt section 7.

[0111] The fuel cell system is provided with a second temperature sensor 12, which collects the temperature T2 of the cooling liquid in the large circulation circuit in real time. The second temperature sensor 12 is arranged in the heat dissipation section 10.

[0112] The principles and implementation manners of the present application are described by using specific embodiments in the present application. The above description of the embodiments is only used to help understand the method of the present application and its core idea. It should be noted that, for those skilled in the art, without departing from the principles of the present application, some improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

[0113] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present application is usually placed, and are only used to facilitate the description of the present application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0114] In the description of the present application, it should be noted that, unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

Claims

1. A method for controlling the mixing temperature of hot and cold coolants in a fuel cell system, applied to a fuel cell system comprising a fuel cell stack, a water pump, a heat dissipation device, and a thermostat, wherein the outlet of the fuel cell stack is connected to the inlet of the water pump, the outlet of the water pump is connected to and returns to the inlet of the fuel cell stack via the thermostat to form a small circulation loop, and the outlet of the water pump is connected to and returns to the inlet of the fuel cell stack via the heat dissipation device and the thermostat to form a large circulation loop, characterized in that, The temperature control method includes: Judgment steps: Set the target temperature Ts, collect the total loop coolant temperature T1(t) and the large loop coolant temperature T2(t) in real time. When the total loop coolant temperature T1(t) is within the deviation range of the target temperature Ts and the large loop coolant temperature T2(t) is outside the deviation range of the target temperature Ts, the control system issues a temperature adjustment command. Calculation of intermediate quantities for feedforward control: Based on the operating conditions of the fuel cell system, obtain the total heat production power Pst(t) within the fuel cell system, and then calculate the intermediate quantities based on the total heat production power Pst(t) and the feedforward control coefficient K. ff The intermediate quantity u of the feedforward control is calculated. ff (t), feedforward control intermediate quantity u ff The calculation process of (t) is shown in the following formula (4): u ff (t)=K ff ·Pst(t)(4) In Equation 4, "K ff “ is the feedforward control system coefficient, and “Pst(t)” is the total heat power generated in the fuel cell system; The feedforward control coefficient K is obtained through calculation. ff Feedforward control coefficient K ff The calculation process is shown in the following formula (7): K ff =1 / (Wc·Ccool)(7) In Equation 7, "Wc" is the mass flow rate of the coolant in the total circuit, and "Ccool" is the specific heat capacity of the coolant. Feedback control intermediate quantity calculation: After confirming the temperature adjustment command... The temperature control error eT(t) is calculated as shown in equation (1) below: eT(t)=Ts-T1(t)(1) In Equation 1, "Ts" is the set control target temperature, and "T1(t)" is the total loop coolant temperature; Based on the temperature control error eT(t), the intermediate quantity u of the closed-loop control is calculated using a linear system control method. fb (t); Linearization of intermediate quantities in feedforward control and feedback control: Calculate the temperature difference δT(t) between the coolant in the total loop and the coolant in the large loop. The calculation process of the temperature difference δT(t) is shown in the following formula (2): δT(t)=T1(t)-T2(t)(2) In Equation 2, "T1(t)" represents the total coolant temperature and "T2(t)" represents the coolant temperature of the large circulation loop. Based on feedforward control intermediate quantity u ff (t), Closed-loop control intermediate quantity u fb (t), temperature difference δT(t), calculate the percentage of large circulation flow rate α(t) required to achieve the target temperature Ts for the mixing temperature of the hot and cold coolant. The calculation process of α(t) is shown in the following formula (5): α(t)=u fb (t) / δT(t)+u ff (t) / δT(t)(5) In Equation 5, "u fb "(t)" represents the intermediate quantity of the closed-loop control, "δT(t)" represents the temperature difference between the coolant in the total loop and the coolant in the main circulation loop, and "u" represents the temperature difference between the coolant in the total loop and the coolant in the main circulation loop. ff (t)” represents the intermediate quantity of feedforward control; Thermostat opening adjustment: Based on the relationship between the calibrated large circulation flow rate percentage α(t) and the thermostat opening percentage, the thermostat opening percentage u(t) is calculated in real time. x The control system sends adjustment commands to the thermostat to adjust the opening degree of the thermostat in real time.

2. The method for controlling the mixing temperature of hot and cold coolants in a fuel cell system as described in claim 1, characterized in that, In the calculation of intermediate quantities in feedback control, the intermediate quantity u of the closed-loop control is... fb The calculation process of (t) is shown in the following equation (6): In Equation 6, " "This refers to the proportional coefficient of the PID control." "This refers to the integral time constant of the PID control." " is the derivative time constant of PID control, and "eT(t)" is the temperature control error.

3. The method for controlling the mixing temperature of hot and cold coolants in a fuel cell system as described in claim 1, characterized in that, In the judgment step, the deviation range of the control target temperature Ts is ±2℃.

4. The method for controlling the mixing temperature of hot and cold coolants in a fuel cell system as described in any one of claims 1-3, characterized in that, The small circulation loop includes a branching section, a heat-generating section, and a confluence section, with the heat-generating section located between the branching section and the confluence section. The large circulation loop includes a branching section, a heat-dissipating section, and a confluence section, with the heat-dissipating section located between the branching section and the confluence section. The heat dissipation device is located in the heat dissipation section. The inlet of the fuel cell stack is connected to the confluence section, and the outlet is connected to the branching section. The heat-generating section in the small circulation loop and the heat-dissipating section in the large circulation loop are connected in parallel. The heat-generating section, the heat-dissipating section, and the confluence section are connected to a thermostat.

5. The method for controlling the mixing temperature of hot and cold coolants in a fuel cell system as described in claim 4, characterized in that, The heat-generating section is equipped with heat-generating equipment.

6. The method for controlling the mixing temperature of hot and cold coolants in a fuel cell system as described in claim 4, characterized in that, Heating devices are installed on the merging section.

7. The method for controlling the mixing temperature of hot and cold coolants in a fuel cell system as described in claim 4, characterized in that, The fuel cell system is equipped with a first temperature sensor, which collects the temperature T1 of the coolant in the main circuit in real time. The first temperature sensor is located in the flow branch section and / or the heat generation section.

8. The method for controlling the mixing temperature of hot and cold coolants in a fuel cell system as described in claim 1, characterized in that, The fuel cell system is equipped with a second temperature sensor, which collects the temperature T2 of the coolant in the large circulation loop in real time. The second temperature sensor is located in the heat dissipation section.

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