Radiator control method of fuel cell

Abstract

The invention relates to the technical field of fuel cells, in particular to a radiator control method of a fuel cell. The method comprises the following steps: collecting the real-time temperature of a fuel cell waterway stack, calculating the control quantity through a PID closed-loop control algorithm, dividing fans of a radiator into three groups, and controlling the start, stop and rotating speed of the fans in stages. And adjusting the rotating speed duty ratio of each group of radiators according to the value of the control quantity, so that the water path stack-out temperature of the fuel cell quickly reaches and is stabilized at the expected temperature. The invention further relates to calculation of PID control parameters, grouping of the radiators, a rotating speed adjusting strategy and a method for controlling a cooling water circulation path through the thermostat before the radiators are started. The method has the advantages of quick response, accurate control, low energy consumption and the like, and is suitable for temperature control of various fuel cell systems.

Description

Technical Field

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

[0002] As a highly efficient and clean energy conversion device, the proton exchange membrane fuel cell (PEMFC) offers broad application prospects in electric vehicles, stationary power stations, and portable power sources due to its low operating temperature, high current density, fast startup, and zero emissions. The PEMFC operates by generating electricity through an electrochemical reaction between hydrogen and oxygen in the presence of a catalyst. The only product is water, significantly reducing environmental pollution. However, during operation, PEMFCs generate not only electricity but also a significant amount of heat. Since the optimal operating temperature range for PEMFCs is limited to 60 to 80°C, effectively managing this heat to ensure the cells operate within this optimal temperature range has become a key issue that needs to be addressed in the development of PEMFC technology.

[0003] Thermal management of PEMFCs is crucial because temperature has a crucial impact on their performance and lifespan. When the PEMFC's operating temperature exceeds its upper limit, the proton exchange membrane and catalyst degrade due to heat, significantly reducing cell performance and potentially even causing serious failure. Conversely, when the temperature is too low, the electrochemical reaction kinetics are negatively impacted, and cell performance also degrades. In severe cases, flooding may occur, further impairing cell performance. Therefore, the core task of the PEMFC thermal management system is to maintain the cell stack within an appropriate temperature range to maximize system life and overall efficiency.

[0004] To achieve this goal, researchers have developed a variety of PEMFC cooling technologies, mainly including heat sink cooling, air cooling, liquid cooling and phase change cooling. Heat sink cooling technology relies on the thermal conductivity of the cooling plate in the plane, and transfers the heat generated by the PEMFC from the central area of the stack to the peripheral area through the cooling plate to achieve edge cooling. However, the challenge of this technology is to ensure that the cooling plate has an extremely high in-plane thermal conductivity to ensure efficient control of the temperature changes in the active area of the stack. High thermal conductivity materials such as graphite-based materials and heat pipes are used to solve this problem, but they still face challenges such as cost, manufacturing difficulty and integration in practical applications.

[0005] Although air cooling technology is simple, its cooling efficiency is relatively low due to the low heat transfer coefficient of air, making it difficult to meet the heat dissipation requirements of high-power PEMFC stacks. In contrast, liquid cooling technology has been widely used because of its high heat transfer coefficient. Liquid cooling usually uses deionized water or a mixture of ethylene glycol and water as the cooling medium, and improves the cooling performance of PEMFC stacks by optimizing the coolant flow field, cooling channels, and alternative cooling media. However, there are also some problems with liquid cooling systems. For example, the conductivity of the cooling medium may cause current leakage, reducing battery efficiency and even leading to bipolar plate degradation. Therefore, developing low-conductivity cooling media or adding antioxidants to the cooling medium to maintain its low conductivity has become an important research direction for liquid cooling technology.

[0006] Phase change cooling technology makes full use of the latent heat of evaporation of the cooling mechanism and realizes the circulation of the cooling medium through hydrophilic wicking, pressure difference, or density difference. It has the advantages of a low cooling medium flow rate, a simplified system layout, and no need for an external cooling circulation pump. Evaporative cooling and boiling cooling are two main forms of phase change cooling, which show good application prospects in PEMFC thermal management, but still need further research and optimization.

[0007] In summary, the thermal management technology of PEMFCs is of great significance for improving battery performance, extending service life, and promoting its commercial application. With the in-depth research and continuous progress of technology, it is believed that more efficient and reliable PEMFC thermal management solutions will emerge in the future, laying a solid foundation for the wide application of PEMFCs. Summary of the Invention

[0008] The purpose of the present invention is to provide a radiator control method for a fuel cell with fast response to overcome the defects of the above-mentioned existing technologies.

[0009] To achieve the purpose of the present invention, the present application provides the following technical solutions.

[0010] The present application provides a temperature control method for a fuel cell. A fan, a temperature sensor, and a controller are provided inside the fuel cell. The controller can adjust the PWM (Pulse Width Modulation, an analog control method) control amount of the radiator in real time. The control method includes the following steps:

[0011] (1) Collect the real-time temperature of the fuel cell water outlet from the stack.

[0012] (2) According to the desired temperature of the water outlet from the stack, use the PID closed-loop control algorithm to calculate the corresponding control amount u(t).

[0013] (3) Divide the fans of the radiator into three groups, with each group containing at least one fan.

[0014] (4) Control the start / stop and rotation speed of three groups of radiators in stages according to the value of the control quantity u(t), specifically including:

[0015] When 0 ≤ u(t) < 30, start the first group of radiators and adjust the rotation speed, and turn off the second and third groups;

[0016] When 30 ≤ u(t) < 60, start the first and second groups of radiators and adjust the rotation speed, and turn off the third group;

[0017] When 60 ≤ u(t) ≤ 90, start all three groups of radiators and adjust the rotation speed;

[0018] The rotation speed of each radiator is adjusted by the sum of the control quantity and the initial control quantity for starting the radiator.

[0019] (5) By adjusting the rotation speed of each group of radiators, make the temperature of the fuel cell water outlet reach and stabilize at the desired temperature quickly.

[0020] Further, in the step (2), the PID closed-loop control algorithm calculates the control quantity u(t) through the following formula:

[0021] u(t) = Kp × e(t) + Ki × ∫e(t)dt + Kd × de(t) / dt;

[0022] Among them, u(t) is the output signal of the PID controller, that is, the duty cycle, %, e(t) is the difference between the desired temperature and the real-time temperature, the unit is °C, and Kp, Ki, and Kd are the proportional coefficient, integral time constant, and differential time constant respectively.

[0023] This formula describes the basic principle of PID control, that is, by performing proportional, integral, and differential operations on the error signal e(t), generating the control signal u(t) to achieve the control of the system. The proportional link adjusts according to the current value of the error, the integral link considers the accumulated value of the error to eliminate the static error, and the differential link performs lead adjustment according to the change rate of the error to increase the predictability of the system.

[0024] The parameter adjustment of the PID controller is the core content of the control system design, including the determination of the proportional coefficient Kp, the integral time constant Ki, and the differential time constant Kd. The adjustment of these parameters is usually based on the characteristics of the controlled process and is determined through theoretical calculation or engineering experience to achieve the best control effect.

[0025] Further, in the step (4):

[0026] When 0 ≤ u(t) < 30, the duty cycle U1 of the rotation speed of the first group of radiators is calculated through the formula U1 = 2.5 × u(t) + U Ini Calculate;

[0027] When 30 ≤ u(t) < 60, the duty cycle of the first group of radiators is fixed at the maximum value, and the duty cycle U2 of the rotational speed of the second group of radiators is calculated through the formula U2 = 2.5×(u(t) - 30) + U Ini Calculation;

[0028] When 60 ≤ u(t) ≤ 90, the duty cycles of both the first group and the second group of radiators are fixed at the maximum value, and the duty cycle U3 of the rotational speed of the third group of radiators is calculated through the formula U3 = 2.5×(u(t) - 60) + U Ini Calculation;

[0029] Among them, U Ini is the initial control quantity of the fuel cell radiator.

[0030] Furthermore, the maximum duty cycle of the first group of radiators and the maximum duty cycle of the second group of radiators are both 90;

[0031] Among them, 15 ≤ U1 ≤ 90, 15 ≤ U2 ≤ 90, 15 ≤ U3 ≤ 90;

[0032] The default value of the initial control quantity U Ini is 15.

[0033] Furthermore, in the step (3), the grouping method of the three groups of radiators is as follows: the first group, the second group, and the third group each include at least one fan, and the total number of fans is at least three. According to the number of cooling fans, the cooling fans are divided into three groups, namely U1, U2, and U3. For example, if there are 6 fans, they can be divided into three groups of 1, 2, and 3.

[0034] Furthermore, the value range of the control quantity u(t) is from 0 to 100. When the actual control quantity u(t) is greater than 90, it meets the maximum workload.

[0035] Furthermore, when u(t) ≥ 90, the duty cycles of the three groups of radiators are all set to the maximum value, that is, the maximum value 90 is set to operate at full power.

[0036] The method of the present invention further includes controlling the cooling water circulation path through a thermostat before the radiator starts: closing the radiator path when the temperature is lower than the threshold, and opening the radiator path when the temperature is higher than the threshold.

[0037] The input of the PID closed-loop control is the real-time temperature error value of the fuel cell stack, the output is the control quantity u(t), and the coordinated control of the three groups of radiators is realized through piecewise linear mapping.

[0038] Advantages of the present invention:

[0039] The present invention can effectively control the temperature of the fuel cell stack leaving the stack, ensuring that the temperature leaving the stack can quickly reach the desired temperature. The present invention provides a fuel cell temperature control method with fast response. By adopting a PID closed-loop control algorithm combined with a segmented control strategy of the radiator, for example, when the system power is loaded and the fuel cell stack is heating up, multiple groups of radiators can be quickly turned off to allow the fuel cell stack to heat up rapidly. Then, according to the monitored temperature rise rate, the rotation speed of each group of radiators is quickly adjusted to make the single-group radiator quickly reach the maximum rotation speed, preventing overshoot of the steady-state temperature, and achieving precise and rapid adjustment of the temperature of the fuel cell stack leaving the stack. This method not only improves the accuracy of temperature control but also ensures that the fuel cell can operate stably and efficiently under various working conditions. By reasonably grouping and controlling the start-stop and rotation speed of the radiator in stages, the present invention effectively utilizes the heat dissipation resources, avoids unnecessary energy consumption, and improves the overall performance and reliability of the system. Brief Description of the Drawings

[0040] Figure 1 It is a schematic diagram of the PID control strategy of the present invention.

[0041] Figure 2 It is a flowchart of the radiator control strategy of the present invention.

[0042] Figure 3 It is the durability working condition of the fuel cell in the embodiment of the present invention.

[0043] Figure 4 It is a real-time temperature change curve of the fuel cell waterway leaving the stack in the embodiment. Detailed Embodiments

[0044] The following will describe the detailed embodiments of the present invention. It should be noted that in the specific description process of these embodiments, for the sake of concise description, this specification cannot describe all the features of the actual embodiments in detail. Without departing from the spirit and scope of the present invention, those skilled in the art can modify and replace the embodiments of the present invention, and the obtained embodiments are also within the protection scope of the present invention.

[0045] The radiator control method of the proton exchange membrane fuel cell provided by the present invention includes:

[0046] Step 1: According to the working principle and stack characteristics in the proton exchange membrane fuel cell, establish a temperature model, that is, the stack temperature in different states;

[0047] Step 2: Establish a PID controller according to the established temperature model and temperature difference value;

[0048] Step 3: Group the radiators according to the working principle, stack characteristics and radiator characteristics in the proton exchange membrane fuel cell;

[0049] Step 4: Through closed-loop control of the PID controller, Figure 1 This is a schematic diagram of the PID control strategy of the present invention, which controls different groups of radiators respectively and controls the cooling fans in real time to maintain the temperature balance of the stack outlet of the proton exchange membrane fuel cell.

[0050] Before performing Step 1, it is necessary to conduct long-term and effective operation tests on the proton exchange membrane fuel cell to determine the optimal temperature for the proton exchange membrane fuel cell to operate at different powers.

[0051] The proton exchange membrane fuel cell cooling system includes: a proton exchange membrane fuel cell stack, a cooling water tank, a water pump, a thermostat, and a radiator; when the outlet cooling water of the proton exchange membrane fuel cell stack is too low, the thermostat closes, and the cooling water does not pass through the radiator to ensure rapid heating of the stack; when the temperature is too high, the thermostat opens, and after the cooling water is dissipated by the radiator, it flows into the inlet of the proton exchange membrane fuel cell stack.

[0052] The closed-loop control algorithm is: PID control.

[0053] The control strategy is: the radiator is divided into three groups and controlled separately. The flow chart of the radiator control strategy of the present invention is as Figure 2 shown.

[0054] The input quantity of the closed-loop control algorithm is the temperature error value of the proton exchange membrane fuel cell stack.

[0055] Detailed introduction to the control model of the radiator:

[0056] T is the currently required temperature of the fuel cell;

[0057] T t is the currently actual temperature of the fuel cell;

[0058] e(t) is the current temperature error of the fuel cell (i.e., the difference between the required temperature and the actual temperature);

[0059] u(t) is the control quantity of the fuel cell radiator control system;

[0060] U Ini is the initial control quantity of the fuel cell temperature control system (when the temperature is greater than a certain threshold, the temperature control system starts, and the control quantity is given a minimum control quantity, that is, the initial control quantity);

[0061] U is the control quantity of the fuel cell temperature control system, and the three groups of radiators are U1, U2, and U3 respectively.

[0062] The embodiments of the present invention will be described in detail below. These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0063] Example 1

[0064] In this example, the fuel cell used is a water-cooled stack fuel cell with a rated power of 130 kW, a rated current of 480 A, and the number of single cells in the stack is 478.

[0065] The specific steps are as follows:

[0066] (1) According to Figure 3 the durability condition, the current is loaded in stages, and the corresponding target temperature at the outlet of the fuel cell water circuit is set as shown in Table 1; collect the real-time temperature at the outlet of the fuel cell water circuit, as Figure 4 shown, calculate the difference between the target temperature and the real-time temperature to obtain the error value e(t);

[0067] (2) According to the PID calculation formula u(t) = Kp×e(t) + Ki×∫e(t)dt + Kd×de(t) / dt, where Kp is 6, Ki is 0.1, and Kd is 0.1, calculate the current control quantity u(t);

[0068] (3) Divide the fans of the radiator of the fuel cell in this example into three groups. The first group has 2 fans, the second group has 4 fans, and the third group has 4 fans;

[0069] (4) When 0 ≤ u(t) < 30, start the first group of radiators and turn off the second and third groups of radiators; when 30 ≤ u(t) < 60, start the first and second groups of radiators and turn off the third group of radiators; when 60 ≤ u(t) ≤ 90, start all three groups of radiators;

[0070] (5) The duty cycle of the rotation speed of the first group of radiators is U1 = 2.5×u(t) + U Ini , the duty cycle of the rotation speed of the second group of radiators is U2 = 2.5×(u(t) - 30) + U Ini , and the duty cycle of the rotation speed of the third group of radiators is U2 = 2.5×(u(t) - 60) + U Ini .

[0071] Table 1

[0072]

[0073]

[0074] The results show that through the above control method, the temperature of the fuel cell can quickly reach and maintain at the desired temperature, and the temperature fluctuation is within ±0.5°C.

Claims

1. A radiator control method for a fuel cell, wherein a radiator, a temperature sensor and a controller are provided in the fuel cell, and the controller can adjust the pulse width modulation control amount of the radiator in real time, characterized in that, It includes the following steps: (1) Collect the real-time temperature of the fuel cell water path out of the stack; (2) According to the desired temperature of the water path out of the stack, use the PID closed-loop control algorithm to calculate the corresponding control quantity u(t); (3) Divide the fans of the radiator into three groups, and each group contains at least one fan; (4) Control the start, stop and speed of the three groups of radiators in stages according to the value of the control quantity u(t), specifically including: When 0 ≤ u(t) < 30, start the first group of radiators and adjust the speed, and turn off the second and third groups; When 30 ≤ u(t) < 60, start the first and second groups of radiators and adjust the speed, and turn off the third group; When 60 ≤ u(t) ≤ 90, start all three groups of radiators and adjust the speed; The speed of each radiator is adjusted by the sum of the control quantity and the initial control quantity for starting the radiator; (5) By adjusting the speed of each group of radiators, make the temperature of the fuel cell water path out of the stack quickly reach and stabilize at the desired temperature.

2. The radiator control method of the fuel cell according to claim 1, wherein, In the step (2), the PID closed-loop control algorithm calculates the control quantity u(t) through the following formula: u(t) = Kp × e(t) + Ki × ∫e(t)dt + Kd × de(t) / dt; Wherein, u(t) is the duty cycle, e(t) is the difference between the desired temperature and the real-time temperature, the unit is °C, and Kp, Ki, and Kd are the proportional coefficient, integral time constant, and differential time constant respectively.

3. The radiator control method of the fuel cell according to claim 1, wherein, In the step (4): When \(0\leq u(t)\lt30\), the duty ratio \(U1\) of the rotation speed of the first group of radiators is calculated by the formula \(U1 = 2.5\times u(t)+U\). Ini Calculated When 30 ≤ u(t) < 60, the duty cycle of the first group of radiators is fixed at the maximum value, and the rotational speed duty cycle U2 of the second group of radiators is calculated through the formula U2 = 2.5×(u(t) - 30) + U Ini Calculation; When 60 ≤ u(t) ≤ 90, the duty cycles of the first and second groups of radiators are both fixed at the maximum value, and the rotational speed duty cycle U3 of the third group of radiators is calculated through the formula U3 = 2.5×(u(t) - 60) + U Ini Calculate; Among them, U Ini is the initial control quantity of the fuel cell radiator.

4. The radiator control method of the fuel cell according to claim 3, characterized in that, The maximum duty cycle of the first group of radiators and the maximum duty cycle of the second group of radiators are both 90; Wherein, 15 ≤ U1 ≤ 90, 15 ≤ U2 ≤ 90, 15 ≤ U3 ≤ 90; The initial control quantity U Ini has a default value of 15.

5. The radiator control method for a fuel cell according to claim 1, wherein In the step (3), the grouping method of the three groups of radiators is: the first group, the second group, and the third group each contain at least one fan, and the total number of fans is at least three.

6. The radiator control method of the fuel cell according to claim 1, characterized in that The value range of the control quantity u(t) is 0 to 100.

7. The radiator control method of the fuel cell according to claim 6, characterized in that, When u(t) ≥ 90, the duty cycles of the three groups of radiators are all set to the maximum value to operate at full power.

8. The radiator control method of the fuel cell according to claim 1, wherein The method further includes controlling the cooling water circulation path by a thermostat before the radiator starts: closing the radiator path when the temperature is lower than the threshold, and opening the radiator path when the temperature is higher than the threshold.

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