Rapid cold start method and system for fuel cell

Abstract

The invention discloses a rapid cold start method and system for a fuel cell. The method comprises the following steps: S1, acquiring a cold start boundary temperature, a normal working temperature and a temperature rise stopping temperature; s2, acquiring the temperature of the electric pile; s3, judging whether the pile temperature is greater than the cold start boundary temperature or not; s4, increasing the temperature of the galvanic pile through an autonomous thermal management mode until the temperature of the galvanic pile is higher than the temperature rise stopping temperature; s5, increasing the temperature of the electric pile in an external auxiliary heating mode until the temperature of the electric pile is higher than the temperature rise stopping temperature; and S6, starting a double-circulation cooling loop when the temperature of the electric pile reaches the normal working temperature. By adopting a hybrid control strategy combining autonomous thermal management and external auxiliary heating, high-energy-efficiency cold start of the fuel cell can be realized, and an accident that the performance of the fuel cell is damaged due to internal freezing of the fuel cell is prevented; by intelligently controlling the heater, the heating efficiency and the flow speed of the cooling circulation loop and integrating a temperature equalizing plate, a fuel cell starting scheme which is short in starting time and reliable is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and in particular relates to a method and system for rapid cold start of a fuel cell. Background Art

[0002] In ultra-low temperature environments, the water inside the fuel cell will freeze, resulting in fuel gas diffusion blockage, reducing the electrochemical active surface area, causing battery performance degradation and extending the start-up time. Therefore, in order to ensure an effective and fast cold start, the fuel cell must be raised above the freezing point before all the pores in the fuel cell cathode catalyst layer are blocked by ice.

[0003] Traditional methods of rapid cold start include setting up an external heater to assist in cold start, using the heater to preheat the fuel cell stack, melt the ice inside the battery, and continue to heat the heater to the normal operating temperature of the fuel cell. However, under extremely cold conditions, the temperature from freezing temperature to normal operating temperature spans about 100 degrees. Using a heater will consume a lot of electricity, increasing energy consumption. At the same time, ice can cause irreversible damage to multiple components of the fuel cell, such as membrane rupture, membrane stratification, gas diffusion loss and layer hydrophobicity. In addition, melted ice water will corrode battery components, including catalysts.

[0004] Another method is to use a fuel cell system without auxiliary heat. The fuel cell system without auxiliary heat mainly relies on the hydrogen pump effect to heat the fuel cell stack. However, the heating efficiency of the hydrogen pump effect is low. Under extreme low temperature conditions, the reaction speed is slow and the startup efficiency is relatively low, which will extend the startup time and cause a certain amount of energy waste. Monitoring the temperature of the coolant to judge the stack temperature cannot monitor the uneven temperature of the stack and the large local temperature difference. It cannot ensure the temperature consistency of the entire stack and cannot avoid the problem of local icing.

[0005] For example, a Chinese patent with publication number CN118039956A discloses a cold start control method and device for a fuel cell system, which belongs to the field of fuel cell technology and is applied to a fuel cell system. The fuel cell system includes a fuel cell controller and a heater. The cold start control method for the fuel cell system includes: when the shutdown time of the fuel cell system reaches a first preset time, starting the fuel cell controller, obtaining the average water temperature of the cooling water at the stack inlet and the stack outlet through the fuel cell controller, and when the average water temperature is less than a first temperature threshold, controlling the heater to heat the cooling water through the fuel cell controller; however, the patent only uses the heater for cold start, which will consume a lot of electricity and increase energy consumption. At the same time, during the rapid heating process, the cold start of the fuel cell is not precisely controlled, such as adjusting the cooling water flow rate and the heater power, etc., which may cause uneven stack temperature and excessive heating speed, resulting in damage to the fuel cell components.

[0006] For example, the Chinese patent with publication number CN103825037A discloses a fuel cell cold start rapid heating system, including a hydrogen delivery pipeline and a fuel cell stack, the hydrogen delivery pipeline delivers hydrogen to the flow channel on the anode side of the fuel cell stack, characterized in that: it also includes a heater, a thermometer and a battery control system; the heater is arranged on the hydrogen delivery pipeline to heat the hydrogen; the thermometer is arranged inside the fuel cell stack to measure the temperature of the stack; the data acquisition end of the battery control system is connected to the thermometer, and the output end is connected to the heater, and the heater is turned on and off according to the temperature inside the stack measured by the thermometer. However, this patent also only uses a heater for cold start, which consumes a lot of electricity and increases energy consumption. At the same time, in the process of extremely fast heating, there is no precise control of the cold start of the fuel cell, such as adjusting the cooling water flow rate and the heater power, etc., which may cause uneven temperature of the stack and too fast heating speed, resulting in damage to the fuel cell components. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a method and system for rapid cold start of a fuel cell.

[0008] The present invention is achieved through the following technical solutions.

[0009] The present invention provides a method for rapid cold start of a fuel cell, comprising the following steps:

[0010] S1, start the fuel cell, obtain the cold start boundary temperature, normal operating temperature and stop heating temperature;

[0011] S2, obtaining the temperature of the battery stack through multi-point temperature sensors;

[0012] S3, judging whether the stack temperature is greater than the cold start boundary temperature, if yes, proceeding to step S4, otherwise proceeding to step S5;

[0013] S4, raising the temperature of the battery stack through the autonomous thermal management mode until the temperature of the battery stack is higher than the temperature at which heating stops, and then proceeding to step S6;

[0014] S5, raising the temperature of the battery stack through the external auxiliary heating mode until the temperature of the battery stack is higher than the temperature at which heating stops;

[0015] S6. Wait for the temperature of the battery stack to reach the normal operating temperature and start the dual-circulation cooling circuit.

[0016] Preferably, obtaining the temperature of the battery stack by using a multi-point temperature sensor comprises the following steps:

[0017] S21, obtaining temperature data from multiple temperature sensors;

[0018] S22, filtering the temperature data to obtain background noise temperature data;

[0019] S23. Perform weighted average calculation on the background noise temperature data to obtain the stack temperature.

[0020] Preferably, the expression for weighted average calculation of the background noise temperature data is as follows:

[0021]

[0022] Among them, T 电堆 is the stack temperature, w i is the weight of the i-th sensor, T i is the background noise temperature data of the i-th sensor, and n is the total number of sensors.

[0023] Preferably, the step of increasing the temperature of the stack by the autonomous thermal management mode until the temperature of the stack is higher than the temperature at which heating stops includes the following steps:

[0024] S41, judging the status of the fuel cell, if it is load reduction, proceeding to step S42, if it is load increase, proceeding to step S43;

[0025] S42, adjusting the variable load of the fuel cell until the temperature of the fuel cell stack is higher than the temperature at which heating stops, and then ending;

[0026] S43. Adjust the current density of the fuel cell until the stack temperature is higher than the temperature at which heating stops.

[0027] Preferably, adjusting the variable load of the fuel cell comprises the following steps:

[0028] S421, reducing the variable load of the fuel cell so that the battery output voltage reaches a preset value;

[0029] S422, obtaining the temperature of the battery stack, and generating a temperature change curve according to the temperature of the battery stack;

[0030] S423, adjusting the battery variable load according to the temperature change curve;

[0031] The step of adjusting the current density of the fuel cell comprises the following steps:

[0032] S431, increasing the current density of the fuel cell to a preset value;

[0033] S432, obtaining the temperature of the battery stack, and generating a temperature change curve according to the temperature of the battery stack;

[0034] S433. Adjust the current density of the fuel cell according to the temperature variation curve.

[0035] Preferably, the step of increasing the temperature of the stack by using the external auxiliary heating mode until the temperature of the stack is higher than the temperature at which heating stops is comprised of the following steps:

[0036] S51, start the heater and the small circulation cooling circuit;

[0037] S52, obtaining the temperature of the battery stack, calculating the difference between the temperature of the battery stack and the temperature at which heating stops, and obtaining the temperature error;

[0038] S53, inputting the temperature error into the PID controller, adjusting the parameters of the PID controller, and obtaining a first PID output;

[0039] S54, adjusting the heating power of the heater according to the first PID output;

[0040] S55, obtaining the temperature of the battery stack, and generating a temperature change curve according to the temperature of the battery stack;

[0041] S56, obtaining a temperature change rate according to a temperature change curve;

[0042] S57, inputting the temperature change rate into the PID controller, adjusting the parameters of the PID controller, and obtaining a second PID output;

[0043] S58. Adjust the flow rate of the small circulation cooling loop according to the second PID output.

[0044] Preferably, adjusting the heating power of the heater according to the first PID output comprises the following steps:

[0045] S541, setting a first threshold;

[0046] S542, determining whether the first PID output is greater than a first threshold, if so, increasing the power of the heater, otherwise reducing the power of the heater;

[0047] The method of adjusting the flow rate of the small circulation cooling loop according to the second PID output comprises the following steps:

[0048] S581, setting a second threshold;

[0049] S582: Determine whether the second PID output is greater than a second threshold value; if so, speed up the flow rate of the small circulation cooling loop; otherwise, slow down the flow rate of the small circulation cooling loop.

[0050] Preferably, the output calculation formula of the PID controller is as follows:

[0051]

[0052] Among them, Output is the PID output, e(t) is the temperature error or temperature change rate between the stack temperature and the set temperature, K p is the proportionality coefficient, K i is the integration coefficient, K d is the differential coefficient.

[0053] A fuel cell rapid cold start system, which implements the above rapid cold start method, comprises: a fuel cell stack, a bipolar plate, a heater, a multi-point temperature sensor, a dual-circulation cooling loop, a water manager and a controller;

[0054] The controller is respectively connected to the heater, the multi-point temperature sensor, the dual-circulation cooling loop and the water manager;

[0055] The bipolar plate is arranged in the fuel cell stack, the water manager is arranged beside the bipolar plate, the dual-circulation cooling circuit is connected to the fuel cell stack, and the multi-point temperature sensor is arranged on the fuel cell stack;

[0056] The dual-circulation cooling circuit includes: a large-circulation cooling circuit and a small-circulation cooling circuit;

[0057] The heater is arranged in the small circulation cooling loop, and the large circulation cooling loop and the small circulation cooling loop are respectively connected to the fuel cell stack.

[0058] Preferably, a temperature balancing plate is provided on the bipolar plate;

[0059] The controller comprises a PID controller, and the PID controller is respectively connected to the heater and the small circulation cooling loop;

[0060] Phase change material is arranged on the double circulation cooling loop.

[0061] The beneficial effects of the present invention are:

[0062] A hybrid control strategy that combines autonomous thermal management and external auxiliary heating can achieve efficient cold start of the fuel cell and prevent accidents that damage the fuel cell performance due to internal icing of the fuel cell. By intelligently controlling the heater and heating efficiency, the flow rate of the cooling cycle, and integrating a temperature equalizer, a fuel cell startup solution with short startup time can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is a flow chart of a method for rapid cold start of a fuel cell provided by an embodiment of the present invention;

[0064] Figure 2 is a schematic diagram of a fuel cell rapid cold start system provided by an embodiment of the present invention;

[0065] Figure 3 This is a flow chart of a method for increasing the temperature of a fuel cell stack through an autonomous thermal management mode provided in an embodiment of the present invention;

[0066] Figure 4 It is a flow chart of a method for increasing the temperature of a fuel cell stack through an external auxiliary heating mode provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0067] The technical solution of the present invention is further described below, but the scope of protection claimed is not limited to the description.

[0068] like Figure 1 As shown, a method for rapid cold start of a fuel cell comprises the following steps:

[0069] S1, start the fuel cell, obtain the cold start boundary temperature, normal operating temperature and stop heating temperature;

[0070] The cold start boundary temperature is used to determine whether to start the autonomous thermal management mode or the external auxiliary heating mode. It needs to be set according to the parameters of the fuel cell. When the heat generated inside the stack in a temperature range is not enough for the stack to overcome the freezing state, this critical point temperature value is the cold start boundary temperature.

[0071] In this embodiment, the cold start boundary temperature is -15°C. When the temperature of the battery stack is higher than -15°C, the heat generated inside the battery stack can be used to heat the battery stack to achieve significant results. This is the battery's autonomous thermal management mode. When the temperature is lower than -15°C, the heat generated inside the battery stack is not enough to enable the battery stack to overcome the freezing state. Therefore, a heater is introduced to assist in heating, which is an external auxiliary heating mode. The cold start boundary temperature is used as the critical point of the cold start control measure, i.e., the guiding condition of the decision-making mechanism, to determine the control strategy mechanism orientation.

[0072] The ideal operating temperature of a fuel cell is usually between 60°C and 80°C. In this embodiment, the normal operating temperature is set to 80°C;

[0073] The temperature for stopping heating can be set according to the optimal operating temperature or the minimum operating temperature of the fuel cell. In this embodiment, the minimum operating temperature for overcoming the freezing state is taken as an example, that is, the temperature for stopping heating is 0°C.

[0074] S2, obtaining the temperature of the battery stack through multi-point temperature sensors;

[0075] The method of obtaining the temperature of the battery stack by using a multi-point temperature sensor comprises the following steps:

[0076] S21, obtaining temperature data from multiple temperature sensors;

[0077] By distributing multiple temperature sensors in different areas of the battery stack, more accurate temperature information can be obtained to avoid the influence of local hot spots on judgment.

[0078] S22, filtering the temperature data to obtain background noise temperature data;

[0079] In this embodiment, since the sensor may be affected by electromagnetic interference or short-term temperature fluctuations, the data is firstly low-pass filtered to remove high-frequency noise, retain the actual temperature change trend, and obtain the noise-free temperature data.

[0080] S23. Perform weighted average calculation on the background noise temperature data to obtain the stack temperature.

[0081] Since each temperature sensor is located at a different position, the measured temperature is also different, and a weighted average calculation is required on the data to obtain an accurate value representing the overall stack temperature.

[0082] The expression for weighted average calculation of the background noise temperature data is as follows:

[0083]

[0084] Among them, T 电堆 is the stack temperature, w i is the weight of the i-th sensor, T i is the background noise temperature data of the i-th sensor, and n is the total number of sensors.

[0085] Sensors at different locations may have different thermal response speeds and measurement accuracies. Different weights can be assigned to the measured values ​​according to factors such as the location of the sensor and the thermal importance of the area in which it is located, and finally the weighted average temperature is calculated.

[0086] In this embodiment, according to the temperature unevenness inside the stack, the stack is divided into different regional models, namely, a reaction zone, a cooling zone, and a bipolar plate. The stack temperature is the temperature inside the fuel cell stack, especially the temperature of the reaction zone. Therefore, the temperature around the membrane electrode assembly, that is, the temperature of the reaction zone, is more important than the temperature of other areas, and the weight of its temperature measurement value is set to the highest.

[0087] By accurately collecting multi-point temperature data, we can ensure accurate control of the temperature of the fuel cell stack, prevent local overheating or overcooling, improve temperature control accuracy, and ensure the reliability and responsiveness of the system in different temperature environments.

[0088] S3, judging whether the stack temperature is greater than the cold start boundary temperature, if yes, proceeding to step S4, otherwise proceeding to step S5;

[0089] S4, raising the temperature of the battery stack through the autonomous thermal management mode until the temperature of the battery stack is higher than the temperature at which heating stops, and then proceeding to step S6;

[0090] Autonomous thermal management mode can reduce reliance on external heating, improving system efficiency while reducing energy consumption.

[0091] In this embodiment, the temperature at which the temperature rise stops is 0°C. When the temperature of the stack reaches 0°C, the autonomous thermal management mode stops raising the temperature of the stack.

[0092] However, it should be noted that the autonomous thermal management mode can set a different stop heating temperature, which does not have to be the same as the external auxiliary heating mode, to extend the use time of the autonomous thermal management mode; for example: set the stop heating temperature of the autonomous thermal management mode to 20°C, and stop the autonomous management mode after the battery stack is heated to 20°C, so as to better support the electrochemical reaction.

[0093] like Figure 3 As shown, the method of increasing the temperature of the stack by the autonomous thermal management mode until the temperature of the stack is higher than the temperature at which the temperature rise is stopped includes the following steps:

[0094] S41, judging the status of the fuel cell, if it is load reduction, proceeding to step S42, if it is load increase, proceeding to step S43;

[0095] S42, adjusting the variable load of the fuel cell until the temperature of the fuel cell stack is higher than the temperature at which heating stops, and then ending;

[0096] When a fuel cell is working, hydrogen decomposes into protons and electrons at the anode, and oxygen undergoes a reduction reaction at the cathode to produce water. This process not only generates electricity but also releases waste heat. By controlling the reaction conditions, the heat in the reaction can be appropriately increased.

[0097] The step of adjusting the variable load of the fuel cell comprises the following steps:

[0098] S421, reducing the variable load of the fuel cell so that the battery output voltage reaches a preset value;

[0099] By reducing the battery variable load, the battery output voltage is reduced to 0.3V-0.5V, so that more chemical energy is converted into heat rather than electrical energy, maximizing heat output and helping the battery stack to heat up quickly. In this embodiment, the voltage output is reduced to 0.4V, which can ensure heat generation and avoid excessive loss of performance.

[0100] S422, obtaining the temperature of the battery stack, and generating a temperature change curve according to the temperature of the battery stack;

[0101] Obtain the temperature of the battery stack, generate a temperature change curve of the battery stack based on the temperature data of the battery stack, and monitor whether the real-time temperature of the battery stack has reached the target temperature.

[0102] S423, adjusting the battery variable load according to the temperature change curve;

[0103] The voltage is adjusted according to the change of the battery stack temperature to ensure the optimal heat output under different temperature conditions, that is, after the temperature reaches the stop heating temperature, the battery variable load is adjusted to the default value.

[0104] When the stop heating temperature of the autonomous management mode is set separately, such as setting the stop heating temperature of the autonomous management mode to the normal operating temperature, the specific adjustment value is: when the temperature of the battery stack reaches between 0℃ and 60℃, the fuel cell is already in a relatively stable reaction area, and it is necessary to balance the heat output and battery performance to avoid excessive heat generation. Therefore, the battery variable load is increased to maintain the battery output voltage at 0.6V-0.7V. When the temperature of the battery stack exceeds 80℃, the battery stack will be at risk of overheating, and it is necessary to reduce the reaction rate and reduce heat generation, so the battery variable load is further raised to above 0.8V.

[0105] S43. Adjust the current density of the fuel cell until the stack temperature is higher than the temperature at which heating stops.

[0106] The step of adjusting the current density of the fuel cell comprises the following steps:

[0107] S431, increasing the current density of the fuel cell to a preset value;

[0108] The heat output is increased by adjusting the operating parameters of the battery and increasing the current density. In this embodiment, the current density is increased to 1.0-1.5A / cm2 to avoid local overheating while outputting heat.

[0109] S432, obtaining the temperature of the battery stack, and generating a temperature change curve according to the temperature of the battery stack;

[0110] Obtain the temperature of the battery stack, generate a temperature change curve of the battery stack based on the temperature data of the battery stack, and monitor whether the real-time temperature of the battery stack has reached the target temperature.

[0111] S433. Adjust the current density of the fuel cell according to the temperature variation curve.

[0112] Automatically adjust the current density according to temperature changes to avoid membrane aging or damage caused by rapid temperature rise; optimize the heat output during the reaction process and improve the startup efficiency of the fuel cell by adjusting the load voltage or current density.

[0113] S5, raising the temperature of the battery stack through the external auxiliary heating mode until the temperature of the battery stack is higher than the temperature at which heating stops;

[0114] like Figure 4 As shown, the method of increasing the temperature of the battery stack by the external auxiliary heating mode until the temperature of the battery stack is higher than the temperature at which the temperature rise is stopped includes the following steps:

[0115] S51, start the heater and the small circulation cooling circuit;

[0116] S52, obtaining the temperature of the battery stack, calculating the difference between the temperature of the battery stack and the temperature at which heating stops, and obtaining the temperature error;

[0117] The temperature of the battery stack is monitored in real time, the current temperature value is obtained through a multi-point temperature sensor, and the difference between the battery stack temperature and the set temperature is calculated; in this embodiment, the difference between the current battery stack temperature and 0° is calculated to obtain the temperature difference.

[0118] S53, inputting the temperature error into the PID controller, adjusting the parameters of the PID controller, and obtaining a first PID output;

[0119] In step S53, among the parameters of the PID controller, the proportional control K p Used to quickly increase temperature, response error, K p When the value is large, the control response is fast, but overshoot is prone to occur; integral control K i Used to eliminate steady-state errors and ensure that the temperature is within the set value, K i A moderate value can prevent the temperature from deviating from the set value for a long time; differential control K d Used to predict error changes and prevent temperature overshoot, suitable for slowing down the heating speed when approaching the set value. The first PID output is obtained by parameter adjustment.

[0120] The PID control algorithm is used to automatically adjust the flow rate of the coolant in the small circulation cooling loop and the power of the heater in real time according to the temperature of the fuel cell stack, ensuring maximum heating efficiency and precise control of the heating rate of the fuel cell stack, so as to avoid overshoot or undershoot during the heating process of the fuel cell stack, improve the safety and stability of the system, and effectively extend the service life of the fuel cell.

[0121] S54, adjusting the heating power of the heater according to the first PID output;

[0122] According to the output of the PID controller, the output power added thereto is adjusted. When the temperature error is large, the first PID output of the PID controller is higher and the heating power of the heater increases. When the temperature difference is small, the first PID output is lower and the output power of the heater decreases.

[0123] The step of adjusting the heating power of the heater according to the first PID output comprises the following steps:

[0124] S541, setting a first threshold;

[0125] S542, determining whether the first PID output is greater than a first threshold, if so, increasing the power of the heater, otherwise reducing the power of the heater;

[0126] In this embodiment, the heating power range of the heater is 0% to 100%, the PID output range is 0 to 1, and the first threshold is set to 0.5 for a heater power of 50%. That is, when the first PID output is greater than 0.5, it means that the temperature error is large and the system needs to speed up the heating, so the heating power of the heater is increased. Conversely, when the first PID output is less than 0.5, it means that the temperature error is small and close to the set target temperature. At this time, the heating power is reduced to prevent overshoot.

[0127] In this embodiment, the heating power is increased or decreased by 10% of the current power each time until the maximum or minimum power is reached.

[0128] S55, obtaining the temperature of the battery stack, and generating a temperature change curve according to the temperature of the battery stack;

[0129] According to the temperature sensor, the change trend of the temperature of the fuel cell stack is monitored in real time to obtain the temperature change curve of the fuel cell stack.

[0130] S56, obtaining a temperature change rate according to a temperature change curve;

[0131] According to the temperature change curve, the rising speed of the battery stack temperature is calculated, and the temperature change rate is obtained as the input of the PID controller.

[0132] S57, inputting the temperature change rate into the PID controller, adjusting the parameters of the PID controller, and obtaining a second PID output;

[0133] In step S57, among the parameters of the PID controller, the proportional control K p Used to quickly respond to temperature changes. When the temperature rises too quickly, proportional control will quickly increase the flow rate of the coolant; integral control K i It is used to eliminate long-term steady-state errors and keep the stack temperature within the set range. Integral control can slowly adjust the flow rate to ensure that the temperature change deviates from the target for a long time; differential control K d Used to predict temperature change trends, reduce flow rate fluctuations and over-adjustment, and prevent coolant from being overcooled or overheated. The second PID output is obtained through parameter adjustment.

[0134] S58. Adjust the flow rate of the small circulation cooling loop according to the second PID output.

[0135] The coolant flow rate is adjusted according to the temperature change rate of the fuel cell stack. When the temperature of the fuel cell stack rises too quickly, the second PID output of the PID controller is higher, and the coolant flow rate of the small circulation cooling loop is increased. When the temperature of the fuel cell stack rises slowly or tends to stabilize, the coolant flow rate of the small circulation cooling loop is reduced.

[0136] The method of adjusting the flow rate of the small circulation cooling loop according to the second PID output comprises the following steps:

[0137] S581, setting a second threshold;

[0138] S582: Determine whether the second PID output is greater than a second threshold value; if so, speed up the flow rate of the small circulation cooling loop; otherwise, slow down the flow rate of the small circulation cooling loop.

[0139] In this embodiment, the flow rate of the small circulation cooling loop can be set to 0% to 100%, the PID output range is 0 to 1, and the second threshold is set to 0.6. That is, when the second PID output is greater than 0.6, it indicates that the temperature change rate is too fast, which may cause overheating in a short time. Therefore, it is necessary to increase the coolant flow rate and reduce the heat transfer time. Conversely, when the second PID output is less than 0.6, it indicates that the temperature change rate is slow, and the flow rate is appropriately slowed down to maintain the heating effect.

[0140] Optionally, the flow rate is increased or decreased by 10% of the current flow rate each time until the maximum or minimum flow rate is reached.

[0141] The output calculation formula of the PID controller is as follows:

[0142]

[0143] Among them, Output is the PID output, e(t) is the temperature error or temperature change rate between the stack temperature and the set temperature, K p is the proportionality coefficient, K i is the integration coefficient, K d is the differential coefficient.

[0144] PID control parameters are continuously adjusted to achieve more precise temperature control and flow rate control.

[0145] The PID control algorithm is used to automatically adjust the flow rate of the coolant in the small circulation cooling loop and the power of the heater in real time according to the temperature of the fuel cell stack, ensuring maximum heating efficiency and precise control of the heating rate of the fuel cell stack, so as to avoid overshoot or undershoot during the heating process of the fuel cell stack, improve the safety and stability of the system, and effectively extend the service life of the fuel cell.

[0146] S6. Wait for the temperature of the battery stack to reach the normal operating temperature and start the dual-circulation cooling circuit.

[0147] The ideal operating temperature of a fuel cell is between 60° and 80°, at which point the reaction efficiency and performance of the fuel cell can reach optimal levels. If the temperature exceeds 80°, the cell stack will overheat. Therefore, when the stack reaches normal operating temperature, the dual-circulation cooling circuit can begin to dissipate heat to prevent the membrane electrode assembly from overheating, damaging the catalyst layer and gas diffusion layer, or reducing the performance of the electrolyte. Maintaining the ideal operating temperature range is critical to the long-term operation and performance of the fuel cell.

[0148] In this embodiment, the threshold of the normal operating temperature is set to 80°, and logic control is adopted. When the temperature of the battery stack approaches this value, the dual-circulation cooling loop is started in advance to prevent temperature overshoot.

[0149] The dual-circulation cooling loop achieves a balance between rapid heating and efficient heat dissipation through a reasonable switching mechanism, ensuring that the fuel cell system maintains good temperature management during low-temperature startup and normal operating stages, thereby improving the reliability and durability of the system.

[0150] like Figure 2 As shown, a fuel cell rapid cold start system realizes the above rapid cold start method, comprising: a fuel cell stack 11, a bipolar plate 12, a heater 13, a multi-point temperature sensor 14, a dual-circulation cooling loop 15, a water manager 16 and a controller;

[0151] The controller is respectively connected to the heater 13, the multi-point temperature sensor 14, the dual-circulation cooling loop 15 and the water manager 16;

[0152] The bipolar plate 12 is disposed in the battery stack 11, the water manager 16 is disposed beside the bipolar plate 12, the dual-circulation cooling loop 15 is connected to the battery stack 11, and the multi-point temperature sensor 14 is disposed on the battery stack 11;

[0153] The dual-circulation cooling circuit 15 includes: a large-circulation cooling circuit 151 and a small-circulation cooling circuit 152;

[0154] The heater 152 is disposed in the small circulation cooling loop 151 , and the large circulation cooling loop 151 and the small circulation cooling loop 152 are respectively connected to the fuel cell stack 11 .

[0155] The fuel cell stack 11 is the core part of the fuel cell system and is used for energy conversion, converting chemical energy into electrical energy;

[0156] The bipolar plate 12 is used to isolate the fuel and the oxidant, provide an air flow channel, and evenly distribute the gas to the reaction layer of the motor for electrode reaction; the bipolar plate 12 is as thin as possible while maintaining a certain mechanical strength and good gas barrier effect to reduce the conduction obstruction of current and heat;

[0157] The heater 13 is used to provide a heat source for the external auxiliary heating mode of the fuel cell, and heat the coolant in the small circulation cooling loop 152;

[0158] Specifically, the multi-point temperature sensors 14 are distributed in different areas of the battery stack to monitor the temperature of the battery stack in real time, and are used to obtain the temperature of the battery stack and transmit the temperature data to the controller;

[0159] The large circulation cooling loop 151 is used to dissipate heat during normal operation of the fuel cell;

[0160] The small circulation cooling loop 152 is used to transfer the temperature of the heater 13 to the fuel cell stack 11;

[0161] When the heated coolant reaches the bipolar plate 12 through the small circulation cooling loop 152, the heat is transferred from the coolant to the bipolar plate 12 by conduction, and then the heat is further evenly distributed through the temperature equalizing plate integrated in the bipolar plate 12 to avoid local hot spots, and the heat is evenly dispersed to various areas of the fuel cell stack 11, helping to increase the internal temperature of the fuel cell stack 11.

[0162] The temperature of the coolant in the small circulation cooling loop 152 decreases after passing through the battery stack 11. At this time, the coolant continues to return to the heater 13 for heating and circulates again to form a closed-loop heat exchange process until the battery stack 11 reaches the desired temperature. The small circulation cooling loop 152 has a short path and a fast circulation speed, and can effectively transfer heat.

[0163] The controller is connected to a multi-point sensor 14 to obtain the temperature of the battery stack 11, and adjusts the working status of the heater 13 and the dual-circulation cooling loop 15 according to the temperature of the battery stack 11. The controller is also responsible for controlling the working time of the water manager 16, playing the role of an overall coordination control component.

[0164] The water manager 16 is used to dry the moisture of the fuel cell stack 11;

[0165] After the battery is shut down, the residual water in the battery stack 11 is removed by releasing the compressed air in the water manager 16 to prevent ice formation at low temperatures.

[0166] In this embodiment, the water manager 16 cooperates with the heater 13 to work together. During the temperature rise phase of the fuel cell stack at cold start, the water manager 16 can assist in draining the water generated by the fuel cell when the heater 13 is heating.

[0167] It effectively solves the problem of moisture accumulation and icing inside the fuel cell stack, extends the life of the system, and ensures the normal startup and operation of the fuel cell in a low temperature environment.

[0168] The bipolar plate 12 is provided with a temperature balancing plate;

[0169] The controller includes a PID controller, and the PID controller is connected to the heater 13 and the small circulation cooling loop 152 respectively;

[0170] The power of the heater 13 and the flow rate of the small circulation cooling loop 152 are adjusted by the PID controller.

[0171] Phase change material is arranged on the dual circulation cooling circuit 15 .

[0172] Specifically, the phase change material wraps the dual-circulation cooling loop 15;

[0173] Phase change materials are used to store excess heat generated when the battery is working, and release this heat when the battery is cold started, helping to quickly heat the battery stack. The heat stored in the phase change material can be used to quickly heat key areas in the fuel cell stack, such as the gas diffusion layer and membrane electrode assembly, thereby accelerating the startup process.

[0174] In this embodiment, a phase change material is wrapped on the dual-circulation cooling loop 15 . When the temperature of the fuel cell stack 11 exceeds a set value, the phase change material absorbs excess heat to further reduce the temperature of the fuel cell stack 11 .

[0175] The manager is used to receive the stack temperature transmitted by the multi-point temperature sensor 14, and control the working states of the heater 13, the dual-circulation cooling loop 15 and the water manager 16 according to the stack temperature.

[0176] The present invention adopts a hybrid control strategy that combines autonomous thermal management and external auxiliary heating to achieve high energy efficiency and prevent accidents that damage the performance of the fuel cell due to ice formation inside the fuel cell. By integrating a temperature equalizing plate, a heater and intelligently controlling the heating efficiency and the flow rate of the cooling circulation loop, a fuel cell startup solution with short startup time and reliability is achieved.

[0177] The application environment of the present invention is mainly concentrated on the start-up of fuel cells in low temperature environments and requiring rapid response.

[0178] This embodiment can be applied in the following scenarios:

[0179] In cold regions, such as the northern regions with low temperatures in winter, fuel cell vehicles need to start quickly at low temperatures. The present invention uses the autonomous thermal management mode and the external auxiliary heating mode to ensure that the vehicle can start quickly and enter the working state at -15°C or even lower, meeting the technical goal of starting the fuel cell to 50% of the rated power within 30 seconds at -20°C. The design of the dual-circulation cooling circuit and water manager can ensure that the fuel cell does not freeze in extremely cold conditions and ensure the normal operation of the system.

[0180] Used for emergency equipment or backup power supplies that need to be started quickly, such as communication base stations, power emergency systems, etc. These devices may need to standby for a long time at low temperatures, but need to be put into operation immediately when started. The present invention can respond quickly to ensure that the equipment can still provide temperature power output in a low temperature environment, especially when the temperature of the battery stack is lower than the set cold start boundary temperature, it can be quickly heated through the external auxiliary heating mode.

[0181] In extreme outdoor environments, such as Arctic expeditions, mountain climbing and camping, and rescue scenarios, portable fuel cells need to start quickly under low temperature conditions. The phase change material and small circulation cooling circuit in the present invention can provide stable startup support in low temperature environments, while accurately adjusting stability and coolant flow rate through the controller to avoid standby energy loss.

[0182] For driverless cars, drones or other automated equipment, when these devices are performing tasks in a low-temperature environment, the fuel cell needs to start quickly and run stably for a long time. The autonomous thermal management mode of the present invention can quickly improve efficiency.

[0183] The present invention adopts a hybrid control strategy that combines autonomous thermal management and external auxiliary heating to achieve high-efficiency fuel cell cold start and prevent accidents that damage the fuel cell performance caused by internal icing of the fuel cell; by intelligently controlling the heater and heating efficiency and the flow rate of the cooling circulation loop and integrating the temperature equalizing plate, a fuel cell start-up solution with short start-up time and reliability is achieved.

Claims

1. A method for rapid cold start of a fuel cell, characterized in that: The following steps are involved: S1, start the fuel cell, obtain the cold start boundary temperature, normal operating temperature and stop heating temperature; S2, obtaining the temperature of the battery stack through multi-point temperature sensors; S3, judging whether the stack temperature is greater than the cold start boundary temperature, if yes, proceeding to step S4, otherwise proceeding to step S5; S4, raising the temperature of the battery stack through the autonomous thermal management mode until the temperature of the battery stack is higher than the temperature at which heating stops, and then proceeding to step S6; S5, raising the temperature of the battery stack through the external auxiliary heating mode until the temperature of the battery stack is higher than the temperature at which heating stops; S6. Wait for the temperature of the battery stack to reach the normal operating temperature and start the dual-circulation cooling circuit.

2. The rapid cold start method according to claim 1, characterized in that: The method of obtaining the temperature of the battery stack by using a multi-point temperature sensor comprises the following steps: S21, obtaining temperature data from multiple temperature sensors; S22, filtering the temperature data to obtain background noise temperature data; S23. Perform weighted average calculation on the background noise temperature data to obtain the stack temperature.

3. The rapid cold start method according to claim 2, characterized in that: The expression for weighted average calculation of the background noise temperature data is as follows: Among them, T 电堆 is the stack temperature, w i is the weight of the i-th sensor, T i is the background noise temperature data of the i-th sensor, and n is the total number of sensors.

4. The rapid cold start method according to claim 1, characterized in that: The method of increasing the temperature of the stack by the autonomous thermal management mode until the temperature of the stack is higher than the temperature at which the temperature rise is stopped includes the following steps: S41, judging the status of the fuel cell, if it is load reduction, proceeding to step S42, if it is load increase, proceeding to step S43; S42, adjusting the variable load of the fuel cell until the temperature of the fuel cell stack is higher than the temperature at which heating stops, and then ending; S43. Adjust the current density of the fuel cell until the stack temperature is higher than the temperature at which heating stops.

5. The rapid cold start method according to claim 4, characterized in that: The step of adjusting the variable load of the fuel cell comprises the following steps: S421, reducing the variable load of the fuel cell so that the battery output voltage reaches a preset value; S422, obtaining the temperature of the battery stack, and generating a temperature change curve according to the temperature of the battery stack; S423, adjusting the battery variable load according to the temperature change curve; The step of adjusting the current density of the fuel cell comprises the following steps: S431, increasing the current density of the fuel cell to a preset value; S432, obtaining the temperature of the battery stack, and generating a temperature change curve according to the temperature of the battery stack; S433. Adjust the current density of the fuel cell according to the temperature variation curve.

6. The rapid cold start method according to claim 1, characterized in that: The external auxiliary heating mode is used to increase the temperature of the battery stack until the temperature of the battery stack is higher than the stop heating temperature. The following steps are involved: S51, start the heater and the small circulation cooling circuit; S52, obtaining the temperature of the battery stack, calculating the difference between the temperature of the battery stack and the temperature at which heating stops, and obtaining the temperature error; S53, inputting the temperature error into the PID controller, adjusting the parameters of the PID controller, and obtaining a first PID output; S54, adjusting the heating power of the heater according to the first PID output; S55, obtaining the temperature of the battery stack, and generating a temperature change curve according to the temperature of the battery stack; S56, obtaining a temperature change rate according to a temperature change curve; S57, inputting the temperature change rate into the PID controller, adjusting the parameters of the PID controller, and obtaining a second PID output; S58. Adjust the flow rate of the small circulation cooling loop according to the second PID output.

7. The rapid cold start method according to claim 6, characterized in that: The heating power of the heater is adjusted according to the first PID output The following steps are involved: S541, setting a first threshold; S542, determining whether the first PID output is greater than a first threshold, if so, increasing the power of the heater, otherwise reducing the power of the heater; The method of adjusting the flow rate of the small circulation cooling loop according to the second PID output comprises the following steps: S581, setting a second threshold; S582: Determine whether the second PID output is greater than a second threshold value; if so, speed up the flow rate of the small circulation cooling loop; otherwise, slow down the flow rate of the small circulation cooling loop.

8. The rapid cold start method according to claim 6, characterized in that: The output calculation formula of the PID controller is as follows: Among them, Output is the PID output, e(t) is the temperature error or temperature change rate between the stack temperature and the set temperature, K p is the proportionality coefficient, K i is the integration coefficient, K d is the differential coefficient.

9. A fuel cell rapid cold start system, characterized in that: A rapid cold start method according to any one of claims 1 to 8, comprising: a battery stack (11), a bipolar plate (12), a heater (13), a multi-point temperature sensor (14), a dual-circulation cooling loop (15), a water manager (16) and a controller; The controller is respectively connected to the heater (13), the multi-point temperature sensor (14), the dual-circulation cooling circuit (15) and the water manager (16); The bipolar plate (12) is arranged in the battery stack (11), the water manager (16) is arranged beside the bipolar plate (12), the dual-circulation cooling circuit (15) is connected to the battery stack (11), and the multi-point temperature sensor (14) is arranged on the battery stack (11); The dual-circulation cooling circuit (15) comprises: a large-circulation cooling circuit (151) and a small-circulation cooling circuit (152); The heater (152) is arranged in the small circulation cooling loop (151), and the large circulation cooling loop (151) and the small circulation cooling loop (152) are respectively connected to the fuel cell stack (11).

10. The fuel cell rapid cold start system according to claim 9, characterized in that: A temperature balancing plate is provided on the bipolar plate (12); The controller comprises a PID controller, and the PID controller is respectively connected to the heater and the small circulation cooling loop (152); Phase change material is arranged on the double circulation cooling circuit (15).

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