Temperature control method and system for fuel cell stack

Abstract

The invention relates to a temperature control method and system for a fuel cell stack, and the method comprises the steps: determining corresponding stack target temperatures under different current values according to a volt-ampere characteristic curve of a controlled stack, and taking the stack target temperatures as corresponding starting temperatures Tref; after the controlled galvanic pile is started, heating and circulating equipment is controlled to enable the pile outlet temperature Tout to rise to the galvanic pile starting temperature Tref according to the size relation between the cooling liquid pile outlet temperature Tout and the starting temperature Tref under the corresponding current; if the current pile outlet temperature Tout is between the starting temperature Tref and the pile inlet temperature Tin, continuing to judge whether the pile inlet and outlet temperature difference is within a set range; otherwise, controlling the working states of heat dissipation equipment and circulation equipment in the cooling liquid circulation loop, and carrying out heat dissipation on the controlled galvanic pile at the maximum power; if the in-pile and out-pile temperature difference is within a set range, maintaining the current state of the electric pile; and if not, controlling the working states of a heat dissipation device and a circulation device in the cooling liquid circulation loop through feedforward control and PID control, so that the temperature difference in and out of the reactor is recovered to a set range.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cells, and in particular to a temperature control method and system for a fuel cell stack. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Proton exchange membrane fuel cells (PEMFCs) can convert chemical energy in hydrogen fuel into electrical energy to supply external loads. During PEMFC operation, its output power not only depends on external reactants, but is also sensitive to temperature changes. If the temperature is too high, membrane dehydration will occur, reducing battery performance and even causing the membrane to dry out; if the temperature is too low, battery polarization will increase, which will also reduce battery performance. However, due to the nonlinear and delayed characteristics of the fuel cell thermal management system, the existing temperature control process is difficult to balance between control accuracy and system response, and there is often a large contradiction. Summary of the invention

[0004] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a temperature control method and system for a fuel cell stack. PID fuzzy control performs small-range adjustment on the basis of feedforward control, avoiding large temperature fluctuations, and can also perform adaptive adjustment according to different ambient temperatures. By combining feedforward control with PID fuzzy control, the response time of the system is effectively shortened and the control error is reduced. By reasonably configuring and using air-cooled radiators of different powers, the heat dissipation effect can be dynamically adjusted according to the current heat dissipation requirements of the stack, improving the system flexibility, energy saving, and enhancing adaptability and reliability.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A first aspect of the present invention provides a method for controlling the temperature of a fuel cell stack, comprising the following steps:

[0007] According to the volt-ampere characteristic curve of the controlled battery stack, the corresponding target temperature of the battery stack under different current values ​​is determined and used as the corresponding starting temperature T ref ;

[0008] Obtain the current density i and voltage V of the controlled battery stack, as well as the outlet temperature T of the battery stack coolant out and the temperature of the pile T in ;

[0009] After the controlled stack is started, the temperature T of the coolant out of the stack is determined according to the current density i and the voltage V. out The starting temperature T under the corresponding current refThe relationship between the size of the cooling liquid and the cooling liquid circulation loop controls the working state of the heating equipment and the circulation equipment in the cooling liquid circulation loop, so that the stack temperature T out Raise to the stack starting temperature T ref ;

[0010] If the current stack outlet temperature T out At the starting temperature T ref and the loading temperature T in If the temperature difference between the inlet and outlet of the stack is within the set range, it continues to determine whether it is within the set range; if not, the working state of the heat dissipation equipment and the circulation equipment in the coolant circulation loop is controlled to dissipate heat to the controlled stack at the maximum power;

[0011] If the temperature difference between the inlet and outlet of the stack is within the set range, the current state of the stack is maintained; if not, the working state of the heat dissipation equipment and circulation equipment in the coolant circulation loop is controlled through feedforward control and PID control to restore the temperature difference between the inlet and outlet of the stack to within the set range.

[0012] Furthermore, the volt-ampere characteristic curve is specifically: through test experiments or simulation models, the target temperature T of the controlled battery stack under different current values ​​is obtained. ref As the starting temperature, we can get the current i and the corresponding temperature T ref The calibration data table is used to form the volt-ampere characteristic curve.

[0013] Furthermore, if the stack temperature T out Greater than the stack starting temperature T at the corresponding current ref , the stack starts normally; if not, the heating and circulation equipment in the coolant circulation loop is turned on to heat the stack so that the stack outlet temperature T out Raise to the stack starting temperature T ref .

[0014] Furthermore, if the starting temperature T ref <Out-of-pile temperature T out <Pile entry temperature T in , then further determine whether the temperature difference between the inlet and outlet piles is within the set range; where the temperature difference between the inlet and outlet piles is |T out -T in |;

[0015] If not satisfied, the start temperature T ref <Out-of-pile temperature T out <Pile entry temperature T in , then the working status of the heat dissipation equipment and circulation equipment in the coolant circulation loop is controlled to dissipate heat to the controlled battery stack at maximum power.

[0016] Furthermore, the circulation device is a water pump, the heat dissipation device is a fan and a thermostat, and the heating device is a PTC heater.

[0017] Furthermore, the working states of the heat dissipation equipment and the circulation equipment in the coolant circulation loop are controlled to dissipate heat to the controlled battery stack at maximum power, specifically: the thermostat opening is 100%, and the water pump speed is maximum, and the fan speed is controlled according to the output power of the battery stack.

[0018] Furthermore, the feedforward control is calibrated according to the fuel cell stack under different load conditions, and the current heat generation of the fuel cell stack is determined according to the obtained battery current, voltage, stack outlet temperature and stack inlet temperature, and the feedforward control duty cycle is obtained by combining the temperature difference between the stack inlet and outlet and the current opening value of the radiator.

[0019] Furthermore, the feedforward duty cycle is specifically: the feedforward control duty cycle of the radiator in the heat dissipation device is obtained by pre-calibrating the radiator under different load conditions according to the battery stack, as shown in the following formula:

[0020]

[0021] P heap =I*V*η;

[0022] D1=K et ×P heap / P rated ;

[0023] Wherein, η is the heating efficiency of the fuel cell stack, I is the current of the fuel cell stack, V is the average cell voltage of the fuel cell stack, t is the time, K et is the feedforward coefficient, P heap P is the real-time heating power of the battery stack; rated is the rated heat dissipation power of the radiator.

[0024] Furthermore, on the basis of feedforward control, the addition and subtraction amount D2 of the fan duty cycle is obtained by looking up the fuzzy control table through the temperature difference between the target temperature entering the stack and the actual temperature entering the stack.

[0025] Furthermore, the feedforward control of the water pump is a duty cycle D3 at a fixed flow rate, and the follow duty cycle of the feedforward control is obtained through bench calibration, that is, a follow duty cycle of the feedforward control is calibrated at each current density.

[0026] Furthermore, the actual temperature difference T r and target temperature difference T f The temperature difference t , the fan PID control operation is as follows:

[0027]

[0028] Where, D4 ​​= u(t)*T, T is the period of the PWM signal. p is the proportionality coefficient; K iis the integration constant; K d is the differential constant, which is calibrated through the proportional, integral and differential parameters in the PID control module according to experience and test process.

[0029] A second aspect of the present invention provides a temperature control system for a fuel cell stack, comprising:

[0030] The coolant outlet of the fuel cell stack is connected to the water pump inlet through a pipeline, and the water pump outlet is connected to the radiator inlet and the PTC heater inlet through pipelines respectively; the outlets of the PTC heater and the radiator are connected to the first and second inlets of the thermostat through pipelines respectively, and the outlet of the thermostat is connected to the coolant inlet of the fuel cell stack through a pipeline; a solenoid valve for bypass is provided on the pipeline where the PTC heater is located.

[0031] Furthermore, the pipeline is also provided with:

[0032] The stack outlet temperature sensor is used to collect the coolant temperature at the outlet of the fuel cell stack;

[0033] Stack temperature sensor. Used to collect the coolant temperature at the inlet of the fuel cell stack;

[0034] Current density detector. Used to detect the current density flowing through the fuel cell stack;

[0035] The voltage detector is used to detect the voltage value at both ends of the fuel cell stack.

[0036] Compared with the prior art, one or more of the above technical solutions have the following beneficial effects:

[0037] 1. Use the volt-ampere characteristic curve to calibrate the ideal operating temperature of the fuel cell stack under different currents. Using this temperature as a reference, the fuel cell stack is raised to the required temperature range within a period of time after startup. During the operation of the fuel cell stack, the inlet and outlet temperature difference of the fuel cell stack coolant is used as the control input. By controlling the heat dissipation device or heating device, the inlet and outlet temperature difference of the fuel cell stack coolant is maintained within the set range.

[0038] 2. Combining feedforward control with PID fuzzy control can effectively shorten the response time of the system and reduce the control error. PID fuzzy control makes small-scale adjustments based on feedforward control, avoiding large temperature fluctuations, and can also make adaptive adjustments according to different ambient temperatures.

[0039] 3. By rationally configuring and using air-cooled radiators of different powers, the heat dissipation effect can be dynamically adjusted according to the current heat dissipation requirements of the fuel cell stack, thereby improving system flexibility, energy saving, and enhancing adaptability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0041] Figure 1 is a flow chart of a fuel cell temperature control method provided by one or more embodiments of the present invention;

[0042] Figure 2 is a schematic diagram of the architecture of a fuel cell temperature control program provided by one or more embodiments of the present invention;

[0043] Figure 3 It is a schematic diagram of a fuel cell stack temperature control system provided by one or more embodiments of the present invention.

[0044] In the figure: 101 stack outlet temperature sensor, 102 stack inlet temperature sensor, 103 current density detector, 104 voltage detector, 201 high power air cooling radiator, 202 low power air cooling radiator, 203 thermostat, 204 water pump, 205 expansion water tank, 206 ion filter, 301 PTC heater, 302 solenoid valve. DETAILED DESCRIPTION

[0045] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0046] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0047] As introduced in the background art, the proton exchange membrane fuel cell (PEMFC) is sensitive to temperature changes during operation. The existing temperature control process is difficult to strike a balance between control accuracy and system response, and there is often a large contradiction.

[0048] Therefore, the following embodiments provide a temperature control method and system for a fuel cell stack. PID fuzzy control performs small-range adjustment based on feedforward control, avoiding large temperature fluctuations, and can also perform adaptive adjustment according to different ambient temperatures. By combining feedforward control with PID fuzzy control, the response time of the system can be effectively shortened and the control error can be reduced. By reasonably configuring and using air-cooled radiators of different powers, the heat dissipation effect can be dynamically adjusted according to the current heat dissipation requirements of the stack, improving system flexibility, energy saving, and enhancing adaptability and reliability.

[0049] Embodiment 1:

[0050] A method for controlling the temperature of a fuel cell stack comprises the following steps:

[0051] According to the volt-ampere characteristic curve of the controlled battery stack, the corresponding target temperature of the battery stack under different current values ​​is determined and used as the corresponding starting temperature T ref ;

[0052] Obtain the current density i and voltage V of the controlled battery stack, as well as the outlet temperature T of the battery stack coolant out and the temperature of the pile T in ;

[0053] After the controlled stack is started, the temperature T of the coolant out of the stack is determined according to the current density i and the voltage V. out The starting temperature T under the corresponding current ref The relationship between the size of the heating circuit and the speed of the water pump is controlled to make the outlet temperature T out Raise to the stack starting temperature T ref ;

[0054] If the current stack outlet temperature T out At the starting temperature T ref and the loading temperature T in If the temperature difference between the inlet and outlet of the stack is within the set range, the working state of the thermostat, water pump and fan is controlled to dissipate heat to the controlled stack at the maximum power.

[0055] If the temperature difference between the inlet and outlet of the stack is within the set range, the current state of the stack is maintained; if not, the opening of the thermostat and the speed of the water pump and fan are adjusted through feedforward control and PID control to restore the temperature difference between the inlet and outlet of the stack to the set range.

[0056] The temperature control process provided in this embodiment is as follows Figure 1 As shown in the figure, the volt-ampere characteristic curve of the battery stack model is obtained, and the target temperature T of the battery stack under different current values ​​is ref As the starting temperature, the current i and temperature T ref Get the target temperature T at different current values ref The actual battery stack equipment can be used for testing or the mathematical model of the battery stack can be used for simulation.

[0057] Get the system stack outlet temperature T out , Pile entry temperature T in , Stack start-up temperature T ref , current density i and voltage V.

[0058] After the fuel cell stack is initially started, the stack temperature T out (e.g. 45°C) is greater than the stack start-up temperature T refIf the condition is met, the stack starts normally. Otherwise, the heating circuit is turned on, the coolant heats the stack, the stack temperature rises, and the stack outlet temperature gradually rises to the stack start-up temperature T ref .

[0059] Detect the current stack temperature T out Whether the starting temperature T ref and the loading temperature T in If the temperature difference between the inlet and outlet temperature is within the range of 5 to 10 K, the temperature difference between the inlet and outlet temperature is between 5 and 10 K. Otherwise, the thermostat opening is 100%, the coolant dissipates heat to the stack at the maximum power, and the fan dissipates heat to the stack at the maximum power according to the power of the stack.

[0060] Finally, determine whether the temperature difference between the inlet and outlet of the stack is within the range of 5 to 10K. If it is, there is no need to change the existing control strategy and parameters, and continue to monitor the inlet and outlet temperatures to ensure that the temperature difference remains within the target range. Otherwise, use feedforward control and PID control to adjust the water pump speed and fan speed to keep the inlet and outlet temperature difference within a stable range.

[0061] The temperature control process of the fuel cell stack can be implemented in the form of a program, such as Figure 2 As shown, it includes: a state acquisition module #100, a judgment module #200, a control algorithm module #200 and an execution module #400; the control algorithm module #200 includes a feedforward control module #301 and a PID control module #302; the execution module #400 includes a radiator control module #401 and a water pump control module #402.

[0062] The state acquisition module #100 obtains the real-time fuel cell stack inlet temperature T through the temperature sensors at the inlet and outlet ends of the fuel cell stack, the current density detector and the voltage detector. r,in , stack temperature T out , current density i and stack starting temperature T ref .

[0063] The judgment module #200 is used to receive the stack status information sent by the status acquisition module #100. This module pre-stores the startup temperature T of the fuel cell stack. ref The starting temperature is based on the volt-ampere characteristic curve of the battery stack model, and the target temperature of the battery stack under different current values ​​is used as the initial temperature value to form a calibration data table of current and temperature.

[0064] The control algorithm module #300 includes a feedforward value algorithm #301 and a PID control #302.

[0065] The feedforward value algorithm module is calibrated according to the stack under different load conditions. The current heat generation of the fuel cell stack is calculated based on the state parameters obtained by the state acquisition module. Based on the preset feedforward value algorithm, the current heat generation of the stack, the stack inlet temperature difference and the current opening value of the radiator are input into the calculation formula of the feedforward value algorithm.

[0066] The PID control algorithm module is based on the feedforward value algorithm, and performs fuzzification, fuzzy reasoning and defuzzification processing through the fuzzy rule control library to output the proportional coefficient k, integral coefficient and differential coefficient.

[0067] The fuel cell stack inlet temperature is controlled by the radiator, and the actual fuel cell stack inlet temperature T r,in and the target temperature T i,in The difference is controlled within the allowable error range.

[0068] In this embodiment, the current heat generation of the fuel cell stack is as shown in the following formula:

[0069] Q = I*V*t;

[0070] Wherein, Q is the current heat generation of the fuel cell stack, I is the current of the fuel cell stack, V is the average cell voltage of the fuel cell stack, and t is time (s).

[0071] The feedforward duty cycle is calibrated according to the fuel cell system under different load conditions. The feedforward control duty cycle of the radiator is shown in the following formula:

[0072]

[0073] E input =I*V*t;

[0074] Among them, η is the heating efficiency of the battery stack, E input The electrical energy input to the fuel cell stack.

[0075] Ideally, the input electrical energy is equal to the heat generated by the battery stack, so the known data can be used directly for calculation. In practical applications, the heating efficiency of the battery stack is usually affected by many factors, such as internal resistance, material properties, etc. Therefore, the actual efficiency can be obtained by the ratio of the measured heat and the input electrical energy, as shown in the following formula:

[0076]

[0077] P heap =I*V*η;

[0078] D1=K et ×P heap / P rated ;

[0079] Where V is the power supply voltage; K et is the feedforward coefficient, take 1.2; P heap P is the real-time heating power of the battery stack; rated is the rated heat dissipation power of the radiator. For the embodiment of the present invention, the rated heat dissipation power of the radiator is the sum of the rated powers of the high-power air-cooled radiator and the low-power air-cooled radiator.

[0080] The fuzzy control of the fan is based on the feedforward control and the target temperature T i,in and the actual temperature T r,in The calculated temperature difference e and the rate of change of the temperature difference △e are used to obtain the fan duty cycle addition and subtraction amount D2 by looking up the fuzzy control table shown in Table 1.

[0081] Table 1 Fuzzy control table

[0082]

[0083] The outlet / inlet temperature difference of the fuel cell stack needs to be controlled by a water pump to keep the outlet / inlet temperature difference of the fuel cell stack within the error range allowed by the target temperature difference.

[0084] The feedforward control of the water pump must maintain the same target temperature difference at each current density point of the battery stack. The flow rate of the cooling water pump will fluctuate around a fixed value. The feedforward control is the duty cycle D3 at a fixed flow rate of the cooling water pump. The follow-up duty cycle of the feedforward control can be obtained through bench calibration, that is, a follow-up duty cycle of the feedforward control is calibrated at each current density.

[0085] The PID fuzzy control of the water pump plays a role of precise regulation based on the feedforward control. r and target temperature difference T f The temperature difference between t , the duty cycle D4 of the water pump is obtained as follows:

[0086]

[0087] Where, D4 ​​= u(t)*T, T is the period of the PWM signal. p is the proportionality coefficient; K i is the integration constant; K d is the differential constant, which is calibrated through the proportional, integral and differential parameters in the PID control module according to experience and test process.

[0088] Execution module #400, namely, radiator control module #401 and water pump control module #402.

[0089] The radiator control module #401 is used to determine whether to configure a high-power air-cooled radiator or a low-power air-cooled radiator based on the output radiator duty cycle and the fan speed table after the PID control module #302 works. For example, when the duty cycle is 80%, the fan speed is 6000r / min, and the high-power air-cooled radiator is running.

[0090] The water pump control module #402 obtains the water pump speed at the corresponding current density from a preset water pump speed table based on the current density of the fuel cell stack and configures the water pump speed to the water pump.

[0091] The above process combines feedforward control with PID fuzzy control, which can effectively shorten the response time of the system and reduce the control error.

[0092] In this case, for the control of the water pump and fan, the feedforward control duty cycle (D1 and D3) is calculated based on the pre-estimation of the system operating status (such as heat load changes, coolant flow demand changes, etc.). The feedforward control will quickly adjust the duty cycle (D1 and D3) of the water pump and fan based on this estimate. This pre-adjustment mechanism does not need to wait for the temperature deviation to occur before making adjustments. Instead, it uses the feedforward control duty cycle to adjust the operating status of the water pump and fan at the same time as the interference occurs, greatly shortening the system response time.

[0093] Although feedforward control can respond quickly to foreseeable disturbances, there are still some factors in the actual system that are difficult to fully predict or errors in the feedforward control itself, which can cause certain temperature deviations. When temperature deviations occur, the PID control duty cycle (D2 and D4) can quickly fine-tune the duty cycle (D2 and D4) of the pump and fan according to the size and trend of the deviation. This dynamic fine-tuning mechanism can accelerate the process of the system reaching a stable state. Compared with using only feedforward control, the addition of PID control duty cycle can more finely adjust the working state of the pump and fan, and correct the remaining temperature deviation after feedforward control more quickly.

[0094] PID fuzzy control makes small-scale adjustments based on feedforward control, avoiding large temperature fluctuations, and can also make adaptive adjustments according to different ambient temperatures. By properly configuring and using air-cooled radiators of different powers, the cooling effect can be dynamically adjusted according to the current cooling requirements of the battery stack, improving system flexibility, energy saving, and enhancing adaptability and reliability.

[0095] Embodiment 2:

[0096] like Figure 3 As shown, a temperature control system of a fuel cell stack includes a fuel cell stack and pipelines.

[0097] Among them, the stack outlet temperature sensor 101 is used to collect the coolant temperature at the outlet of the fuel cell stack; the stack inlet temperature sensor 102 is used to collect the coolant temperature at the inlet of the fuel cell stack; the current density detector 103 is used to detect the current density flowing through the fuel cell stack; the voltage detector 104 is used to detect the voltage value at both ends of the fuel cell stack; the water pump 204 inlet is connected to the stack coolant outlet through a pipeline, and the water pump outlet is connected to the radiator 201 (202) inlet and the PTC heater 301 inlet through pipelines respectively; the first and second inlets and outlets of the thermostat 203 are respectively connected to the PTC heater 301 and the radiator 201 (202) and the stack inlet through pipelines; the solenoid valve 302 is connected to both sides of the PTC heater 301. Since the PTC heater heats the coolant in a low temperature environment, the fuel cell stack operates at the target temperature T ref , does not work at room temperature, so this embodiment does not involve the control of the PTC heater 301.

[0098] The target temperature T of the stack at different current values ref Set as the starting temperature, set the low temperature starting temperature T l Set the high temperature start temperature T to 40℃ h is 100°C.

[0099] Since it is difficult to monitor the actual temperature of the fuel cell, and considering that the coolant temperature at the outlet of the fuel cell stack is close to the actual temperature of the fuel cell and can be monitored, this embodiment selects the outlet temperature of the fuel cell stack as the actual temperature of the fuel cell. ref , T l , T h There is no limitation on the specific value of , which can be selected based on specific calculations in actual applications.

[0100] When the stack outlet temperature is judged to be greater than T l and less than T ref When the stack is heated, the stack needs to reach the set start-up temperature as soon as possible. The coolant starts to flow through the heating circuit, and the coolant flows through the stack outlet, water pump 204, filter 206, expansion tank 205, PTC heater 301, thermostat 203 and stack inlet in sequence. At this time, the first inlet of the thermostat 203 is open, and the second inlet is closed, with an opening of 0%. At this stage, at T l and T ref N temperature intervals are set, and the corresponding water pump speed is set to the first speed and gradually increases to the Nth speed. When the stack outlet temperature is in the i-th interval, the water pump is controlled to run at the i-th speed. By adjusting the water pump speed, the circulation rate of the coolant can be adjusted, and the heating process of the fuel cell stack can be dynamically adjusted to avoid the water pump running at full speed and reduce the energy consumption of the water pump.

[0101] When the fuel cell stack temperature is greater than the stack setting T ref When the battery stack enters the normal working stage, the temperature rises rapidly, the thermostat opens gradually, and the coolant begins to flow through the coolant circuit. The coolant flows through the battery stack outlet, water pump 204, filter 206, expansion water tank 205, radiator 201 (202), thermostat 203 and battery stack inlet in sequence.

[0102] When the stack temperature is kept below T h Within this temperature range, the water pump speed and fan speed are controlled by feedforward control and PID to ensure that the temperature difference deviation of the stack is minimal and the temperature error of the stack is within 5-10K, ensuring that the temperature fluctuates within an acceptable range. h When the water pump is controlled to run at full speed, the thermostat opening is 100%, and the fan dissipates heat to the battery stack at the maximum power possible according to the battery stack power, so that the temperature of the battery stack is maintained within the optimal temperature range for normal operation.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A temperature control method for a fuel cell stack, characterized in that: The following steps are involved: According to the volt-ampere characteristic curve of the controlled battery stack, the corresponding target temperature of the battery stack under different current values ​​is determined and used as the corresponding starting temperature T ref ; Obtain the current density i and voltage V of the controlled battery stack, as well as the outlet temperature T of the battery stack coolant out and the temperature of the pile T in ; After the controlled stack is started, the temperature T of the coolant out of the stack is determined according to the current density i and the voltage V. out The starting temperature T under the corresponding current ref The relationship between the size of the cooling liquid and the cooling liquid circulation loop controls the working state of the heating equipment and the circulation equipment in the cooling liquid circulation loop, so that the stack temperature T out Raise to the stack starting temperature T ref ; If the current stack outlet temperature T out At the starting temperature T ref and the loading temperature T in If the temperature difference between the inlet and outlet of the stack is within the set range, it continues to determine whether it is within the set range; if not, the working state of the heat dissipation equipment and the circulation equipment in the coolant circulation loop is controlled to dissipate heat to the controlled stack at the maximum power; If the temperature difference between the inlet and outlet of the stack is within the set range, the current state of the stack is maintained; if not, the working state of the heat dissipation equipment and circulation equipment in the coolant circulation loop is controlled through feedforward control and PID control to restore the temperature difference between the inlet and outlet of the stack to within the set range.

2. A fuel cell stack temperature control method according to claim 1, characterized in that: The volt-ampere characteristic curve is as follows: Through test experiments or simulation models, the target temperature T of the controlled stack under different current values ​​is obtained. ref As the starting temperature, we can get the current i and the corresponding temperature T ref The calibration data table is used to form the volt-ampere characteristic curve.

3. A fuel cell stack temperature control method according to claim 1, characterized in that: If the out-of-pile temperature T out Greater than the stack starting temperature T at the corresponding current ref , the stack starts normally; if not, the heating and circulation equipment in the coolant circulation loop is turned on to heat the stack so that the stack outlet temperature T out Raise to the stack starting temperature T ref .

4. A fuel cell stack temperature control method according to claim 1, characterized in that: If satisfied, the starting temperature T ref <Out-of-pile temperature T out <Pile entry temperature T in , then further determine whether the temperature difference between the inlet and outlet piles is within the set range; where the temperature difference between the inlet and outlet piles is |T out -T in |; If not satisfied, the start temperature T ref <Out-of-pile temperature T out <Pile entry temperature T in , then the working status of the heat dissipation equipment and circulation equipment in the coolant circulation loop is controlled to dissipate heat to the controlled battery stack at maximum power.

5. A fuel cell stack temperature control method according to claim 1, characterized in that: Control the working status of the heat dissipation equipment and circulation equipment in the coolant circulation loop to dissipate heat to the controlled battery stack at maximum power, specifically: the thermostat opening is 100%, and the water pump speed is maximum, and the fan speed is controlled according to the output power of the battery stack.

6. A fuel cell stack temperature control method according to claim 1, characterized in that: In the feedforward control, the feedforward control duty ratio D1 of the radiator is obtained by calibration under different load conditions of the battery stack, as shown in the following formula: P heap =I*V*η; D1=K et ×P heap / P rated ; Wherein, η is the heating efficiency of the fuel cell stack, I is the current of the fuel cell stack, V is the average cell voltage of the fuel cell stack, t is the time, K et is the feedforward coefficient, P heap P is the real-time heating power of the battery stack; rated is the rated heat dissipation power of the radiator.

7. A fuel cell stack temperature control method according to claim 1, characterized in that: On the basis of feedforward control, the temperature difference and the rate of change of the temperature difference are calculated through the target temperature entering the stack and the actual temperature entering the stack. By looking up the fuzzy control table, the addition and subtraction amount D2 of the fan duty cycle is obtained.

8. A fuel cell stack temperature control method according to claim 1, characterized in that: The feedforward control of the water pump is a duty cycle D3 at a fixed flow rate, and the follow duty cycle of the feedforward control is obtained through bench calibration, that is, a follow duty cycle of the feedforward control is calibrated at each current density.

9. A fuel cell stack temperature control method according to claim 1, characterized in that: In PID control, the actual temperature difference T r and target temperature difference T f The temperature difference between t The fan PID control operation is as follows: Where, D4 ​​= u(t)*T, T is the period of the PWM signal. p is the proportionality coefficient; K i is the integration constant; K d is the differential constant, which is calibrated through the proportional, integral and differential parameters in the PID control module according to experience and test process.

10. A temperature control system for a fuel cell stack implementing the method according to any one of claims 1 to 9, comprising: The coolant outlet of the fuel cell stack is connected to the water pump inlet through a pipeline, and the water pump outlet is connected to the radiator inlet and the PTC heater inlet through pipelines respectively; The outlets of the PTC heater and the radiator are connected to the first and second inlets of the thermostat through pipelines respectively, and the outlet of the thermostat is connected to the coolant inlet of the fuel cell stack through a pipeline; a solenoid valve for bypass is provided on the pipeline where the PTC heater is located.

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