CN114784320A - An air-cooled fuel cell cathode control method against environmental disturbance - Google Patents

Abstract

The invention provides an air-cooled fuel cell cathode control method against environmental disturbance, belonging to the technical field of new energy power generation. Specifically, the load current is obtained according to the reference temperature-current curve and the protection activation resistance-current curve of the air-cooled fuel cell stack, respectively. The reference temperature and protection activation resistance value corresponding to the value, adjust the stack temperature to the reference temperature, and measure the activation resistance value of the stack in real time; trend, then lower the corresponding reference temperature and repeat until the activation resistance value tends to be stable, so as to realize the cathode control of the air-cooled fuel cell. Based on the reference temperature control, the present invention obtains an anti-environmental disturbance control method by introducing the protection activation resistance value related to the environmental conditions, which can effectively avoid the voltage decay of the stack and prolong the service life of the stack, which is beneficial to the specific combined with engineering applications.

Description

An air-cooled fuel cell cathode control method against environmental disturbance

technical field

The invention belongs to the technical field of new energy power generation, and in particular relates to an air-cooled fuel cell cathode control method resistant to environmental disturbance.

Background technique

As a kind of clean energy, proton exchange membrane fuel cell has the characteristics of high efficiency, zero pollutant emission, long battery life, and low working temperature. It is one of the research hotspots in the field of new energy. Air-cooled proton exchange membrane fuel cells eliminate the need for auxiliary equipment for realizing functions such as cooling liquid circulation and reaction gas humidification. Compared with traditional fuel cells, they have the advantages of light weight, high efficiency, and compact structure. The ideal power source for the future of electrical systems.

The output performance of the proton exchange membrane fuel cell has a great relationship with its operating temperature and the water content of the proton exchange membrane. The fuel cell stack needs to maintain a suitable temperature and water content during operation, and the temperature and water content are too high or too low. The content will cause the output performance of the stack to decrease. Since the air-cooled fuel cell has no auxiliary humidification equipment, the water content of the stack membrane is mainly regulated by the cooling fan of the cathode. temperature. The water content inside the stack is indirectly affected by the temperature, and the temperature will affect the evaporation rate of the water inside the stack, so the temperature and the water content show a coupled relationship. On the whole, the cooling fan of the stack cathode plays three roles, one is to transport the air required for the electrochemical reaction to the cathode; the other is to control the temperature of the stack by agitating the air flow; the third is to indirectly control the temperature of the stack. Control the water content inside the stack. Many literatures show that the supply of cathode reactant gas for air-cooled fuel cells is far from sufficient, so the main factor that determines the performance of the stack is to control the stack temperature at an appropriate level by controlling the cooling fan of the cathode.

No matter what specific control method is used to control the cooling fan of the cathode, the controller needs to input a reference temperature so that the temperature can be quickly controlled near the reference temperature value by the cooling fan. The so-called reference temperature refers to the maximum output voltage of the stack at this temperature. The stack has different reference temperatures under different load currents, and the reference temperatures of the stack under different currents can be obtained through experiments. However, this relationship curve is only measured under a specific environmental condition. If the environmental conditions change, the reference temperature-current relationship curve may deviate from the actual one. Once the deviation is too large, it will cause the controller to control the temperature too high, so that the water content of the stack decreases sharply, resulting in an irreversible and rapid decay of the voltage. This is also a common problem that the academic community believes that air-cooled fuel cells exist, that is, it is difficult to make the stack adaptable to environmental changes simply from the perspective of temperature control. In order to prevent the large deviation of the simple reference temperature control due to environmental influences and the irreversible rapid decay of the stack voltage, it is necessary to invent an air-cooled fuel cathode control that is resistant to environmental disturbances from other perspectives on the basis of temperature control. method.

SUMMARY OF THE INVENTION

In view of the above problems in the prior art, the present invention proposes an air-cooled fuel cell cathode control method that is resistant to environmental disturbances. Heap stable high performance output.

The specific technical scheme of the present invention is as follows:

A method for controlling the cathode of an air-cooled fuel cell against environmental disturbance, characterized in that it comprises the following steps:

Step 1: Open the anode hydrogen inlet valve and the cathode fan, set the load current to a fixed value I, and the air-cooled fuel cell stack starts to work;

Step 2: According to the reference temperature-current curve and the protection activation resistance-current curve of the air-cooled fuel cell stack, respectively obtain the reference temperature and protection activation resistance value corresponding to the load current value of 1;

Step 3: The temperature of the air-cooled fuel cell stack is adjusted to be near the reference temperature through a control algorithm, and the activation resistance value of the air-cooled fuel cell stack is measured in real time while the temperature is being adjusted;

Step 4: If the activation resistance value is rapidly approaching the corresponding protection activation resistance value, and there is a tendency to exceed the protection activation resistance value, lower the corresponding reference temperature to avoid the activation resistance being too high due to excessive temperature, which will lead to irreversible and rapid voltage decay ; Then go back to step 3 until the activation resistance value becomes stable, realizing the cathode control of the air-cooled fuel cell.

Further, the control algorithm is a proportional-integral-derivative (PID) control algorithm, a predictive control algorithm, an active disturbance rejection control algorithm, and the like.

Further, in step 3, when the activation resistance value of the air-cooled fuel cell stack is measured in real time, the load current value is monitored in real time. If the load current value changes to I', I' is the load current according to the method in steps 2 to 4. value for cathode control.

Further, the steps of obtaining the reference temperature-current curve are as follows:

Step A1: Open the anode hydrogen inlet valve, and adjust the hydrogen inlet pressure to a fixed value that makes the output performance of the stack good, the specific value depends on the fuel cell system used;

Step A2: Turn on the cathode fan to provide oxygen for the air-cooled fuel cell stack;

Step A3: set the load current to a fixed value I, and the air-cooled fuel cell stack starts to work;

Step A4: The speed of the cathode fan is controlled by the duty cycle of the pulse width modulation (PWM) signal. By adjusting the duty cycle of the PWM signal of the cathode fan to P _A , the temperature of the air-cooled fuel cell stack is stably maintained at a low 30°C. ℃ level;

Step A5: Take P _A as the initial value, ΔP as the fixed step size, wait for the temperature of the air-cooled fuel cell stack to remain stable as the criterion for the next decrease, and stepwise decrease the PWM signal of the cathode fan, so that the air-cooled fuel cell stack is The temperature step increases, observe the change curve of the stack output voltage during the period, until the stack output voltage begins to decay rapidly, stop the stepwise decreasing cathode fan PWM signal, the temperature corresponding to the maximum value of the stack output voltage during the period is the load current value I reference temperature at ;

Step A6: Set the load current to different fixed values, and repeat steps A4 to A5 respectively to obtain the reference temperature under different load current values, and draw the reference temperature-current curve.

Further, ΔP is 1% to 10%, which is selected based on the actual situation of the air-cooled fuel cell stack used. The smaller the ΔP, the higher the measurement accuracy of the experiment, but the time cost of the experiment will also be corresponding. Increase.

Further, the steps of obtaining the protection activation resistance-current curve are as follows:

Step B1: Open the anode hydrogen inlet valve, and adjust the hydrogen inlet pressure to a fixed value that makes the output performance of the stack good, and the specific value depends on the fuel cell system used;

Step B2: turn on the cathode fan to provide oxygen for the air-cooled fuel cell stack;

Step B3: set the load current to a fixed value I, and the air-cooled fuel cell stack starts to work;

Step B4: The speed of the cathode fan is controlled by the duty cycle of the PWM signal, and the temperature of the air-cooled fuel cell stack is stably maintained at a low level of about 30°C by adjusting the duty cycle of the cathode fan PWM signal to P _A ;

Step B5: applying an AC disturbance current whose amplitude is X percent of the load current to the air-cooled fuel cell stack, and measuring and calculating the activation resistance of the current air-cooled fuel cell stack;

Step B6: Take P _A as the initial value, ΔP as the fixed step size, wait for the temperature of the air-cooled fuel cell stack to remain stable as the criterion for the next decrease, and stepwise decrease the PWM signal of the cathode fan, so that the air-cooled fuel cell stack is The temperature step increases; test the activation resistance of each step process until the output voltage of the stack starts to decay rapidly, stop the stepwise decrease of the cathode fan PWM signal, and the activation resistance measured last before the output voltage of the stack starts to decay rapidly is the load current value. is the protection activation resistance when I;

Step B7: Set the load current to different fixed values, and repeat steps B4 to B6 respectively to obtain the protection activation resistance under different load current values, and draw the protection activation resistance-current curve.

Further, X is from 1 to 10, and the value range is a common industry standard.

Further, the frequency range of the AC disturbance current is 0.2-500 Hz.

The beneficial effects of the present invention are:

The invention proposes an air-cooled fuel cell cathode control method that is resistant to environmental disturbance, analyzes the cause of stack voltage decay from a deeper perspective, and introduces a protective activation resistance value related to environmental conditions on the basis of reference temperature control. , to obtain an anti-environmental disturbance control method, which can effectively avoid the voltage attenuation of the stack and prolong the service life of the stack; this method can realize automatic control through programming, the implementation process is simple and efficient, and is conducive to combining with specific engineering applications, It is convenient to practically solve the problems of air-cooled fuel cells in engineering applications.

Description of drawings

Fig. 1 is the temperature change curve of the air-cooled fuel cell stack corresponding to the step-decreasing cathode fan PWM signal when the load current value is 10A in Example 1 of the present invention;

Fig. 2 is the stack output voltage variation curve corresponding to the PWM signal of the step-decreasing cathode fan when the load current value is 10A in Embodiment 1 of the present invention;

3 is a flowchart of obtaining a reference temperature when the load current value is 10A in Embodiment 1 of the present invention;

4 is an illustration diagram of the application of electrochemical impedance spectroscopy in an air-cooled fuel cell system in Example 1 of the present invention;

Fig. 5 is the activation resistance change curve corresponding to the PWM signal of the step-decreasing cathode fan when the load current value is 15A in Embodiment 1 of the present invention;

6 is a flow chart of obtaining the protection activation resistor when the load current value is 15A in Embodiment 1 of the present invention;

7 is a control block diagram of the method for controlling the cathode of an air-cooled fuel cell with anti-environmental disturbance proposed in Embodiment 1 of the present invention;

FIG. 8 is a control flow chart of the method for controlling the cathode of an air-cooled fuel cell with anti-environmental disturbance proposed in Embodiment 1 of the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described with reference to the following specific embodiments and the accompanying drawings.

The following non-limiting examples may enable those of ordinary skill in the art to more fully understand the present invention, but do not limit the present invention in any way.

Example 1

This embodiment proposes an air-cooled fuel cell cathode control method that is resistant to environmental disturbances, which is implemented based on the control block diagram shown in FIG. 7 , and the flowchart is shown in FIG. 8 , including the following steps:

Step 1: Open the anode hydrogen inlet valve and the cathode fan, set the load current to a fixed value I, and the air-cooled fuel cell stack starts to work.

Step 2: According to the reference temperature-current curve and the protection activation resistance-current curve of the air-cooled fuel cell stack, the controller obtains the corresponding reference temperature T ₁ and protection activation resistance value R ₁ when the load current value is I, respectively.

Step 3: The temperature sensor measures the temperature of the air-cooled fuel cell stack in real time, and the controller controls the cathode fan through the PID control algorithm to adjust the temperature of the air-cooled fuel cell stack to the vicinity of the reference temperature T1 _; while the temperature is adjusted, the electrochemical impedance is The spectrum measuring instrument measures the activation resistance value of the air-cooled fuel cell stack in real time, and monitors the load current value in real time.

Step 4: If the activation resistance value is rapidly approaching the corresponding protection activation resistance value R ₁ and tends to exceed the protection activation resistance value R ₁ , the controller reduces the corresponding reference temperature to T ₁ -ΔT to avoid activation due to excessive temperature The resistance is too high, resulting in irreversible and rapid voltage decay; then go back to step 3, if at the reference temperature of T ₁ -ΔT, the activation resistance value is still rapidly approaching the corresponding protection activation resistance value R ₁ , and there is more than the protection activation resistance The trend of the value R ₁ , the controller continues to reduce the corresponding reference temperature to T ₁ -2ΔT until the activation resistance value becomes stable.

Step 5: If in the control process of step 4, the load current value changes to I', obtain the reference temperature T ₂ and the protection activation resistance value R ₂ corresponding to the load current value of I' according to the method of step 2, refer to the step The methods 3 to 4 are used to control the cathode, and finally realize the cathode control of the air-cooled fuel cell.

Wherein, the acquisition process of the reference temperature-current curve specifically includes the following steps:

Step A1: Open the anode hydrogen inlet valve and adjust the hydrogen inlet pressure to 20KPa;

Step A2: Turn on the cathode fan, set the PWM to 10%, and provide oxygen for the air-cooled fuel cell stack;

Step A3: Set the load current to a fixed value of 10A, the air-cooled fuel cell stack starts to work, and outputs a constant current of 10A;

Step A4: Adjust the PWM signal of the cathode fan to 50%, so that the temperature of the air-cooled fuel cell stack is kept stable at 30°C;

Step A5: Take 50% as the initial value, 5% as the fixed step size, and wait for the temperature of the air-cooled fuel cell stack to remain stable as the criterion for the next decrease, stepwise decrease the cathode fan PWM signal, and the number of stepwise decrease is K , so that the temperature of the air-cooled fuel cell stack increases in steps, the temperature change curve is shown in Figure 1, and the change curve of the stack output voltage during the observation period is shown in Figure 2, until the stack output voltage begins to decay rapidly, that is, Figure 2 The temperature corresponding to the maximum output voltage of the stack during the period, that is, the temperature corresponding to point A in Figure 2 (point A in Figure 1), is used as a reference when the load current value is 10A. temperature, the flow chart is shown in Figure 3;

Step A6: Set the load current to different fixed values (15A, 20A, 25A, 30A, and 35A), repeat steps A4 to A5 respectively, obtain the reference temperature under different load current values, and draw the reference temperature-current curve.

The acquisition process of the protection activation resistance-current curve specifically includes the following steps:

Step B1: Open the anode hydrogen inlet valve, and adjust the hydrogen inlet pressure to 20KPa;

Step B2: Turn on the cathode fan, set the PWM to 10%, and provide oxygen for the air-cooled fuel cell stack;

Step B3: set the load current to a fixed value of 15A, the air-cooled fuel cell stack starts to work, and outputs a constant current of 15A;

Step B4: adjust the PWM signal of the cathode fan to 50%, so that the temperature of the air-cooled fuel cell stack is kept stable at 30°C;

Step B5: Based on the system shown in Figure 4, an electrochemical impedance spectroscopy measuring instrument is used to apply an AC disturbance current with an amplitude of 5% of the load current to the air-cooled fuel cell stack, that is, 0.05*15A, the frequency of the AC disturbance current The range is 0.2~500Hz, and the activation resistance of the current air-cooled fuel cell stack is obtained by measurement and calculation;

Step B6: take 50% as the initial value, 5% as the fixed step size, and wait until the temperature of the air-cooled fuel cell stack is stable as the criterion for the next decrease, step down the cathode fan PWM signal, so that the air-cooled fuel cell power The temperature of the stack increases step by step; test the activation resistance of each step process, the change curve is shown in Figure 5, until the output voltage of the stack begins to decay rapidly, corresponding to point B in Figure 5, stop the step decreasing the cathode fan PWM signal, and the output voltage of the stack The activation resistance measured for the last time before the rapid decay starts, corresponding to point A in Figure 5, as the protection activation resistance when the load current value is 15A, the flow chart is shown in Figure 6;

Step B7: Set the load current to different fixed values (10A, 20A, 25A, 30A, and 35A), repeat steps B4 to B6 respectively, obtain the protection activation resistance under different load current values, and draw the protection activation resistance-current curve.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or Equivalent replacement, without departing from the spirit and scope of the technical solution, should be included in the scope of the claims of the present invention.

Claims (8)

1. An environmental disturbance resistant air-cooled fuel cell cathode control method is characterized by comprising the following steps:

step 1: opening an anode hydrogen inlet valve and a cathode fan, setting the load current to be a fixed value I, and starting the air-cooled fuel cell stack to work;

step 2: respectively obtaining a reference temperature and a protection activation resistance value corresponding to a load current value I according to a reference temperature-current curve and a protection activation resistance-current curve of the air-cooled fuel cell stack;

and step 3: adjusting the temperature of the air-cooled fuel cell stack to a reference temperature through a control algorithm, and simultaneously measuring the activation resistance value of the air-cooled fuel cell stack in real time;

and 4, step 4: if the activation resistance value approaches to the corresponding protection activation resistance value quickly and the trend of exceeding the protection activation resistance value exists, the corresponding reference temperature is reduced; and then, returning to the step 3 until the activation resistance value tends to be stable, thereby realizing the cathode control of the air-cooled fuel cell.

2. The method for controlling the cathode of the air-cooled fuel cell resistant to environmental disturbance according to claim 1, wherein the load current value is monitored in real time in step 3, and if the load current value changes to I ', cathode control is performed according to the method of steps 2 to 4 by using I' as the load current value.

3. The environmentally disturbance resistant air-cooled fuel cell cathode control method according to claim 1, wherein the control algorithm is a PID control algorithm, a predictive control algorithm, or an active disturbance rejection control algorithm.

4. The environmental disturbance resistant air-cooled fuel cell cathode control method according to claim 1, wherein the reference temperature-current curve is obtained by:

step A1: opening an anode hydrogen inlet valve, and adjusting the hydrogen inlet pressure;

step A2: starting a cathode fan to provide oxygen for the air-cooled fuel cell stack;

step A3: setting the load current as a fixed value I, and starting the air-cooled fuel cell stack to work;

step A4: by adjusting the duty cycle of the cathode fan PWM signal to P_AKeeping the temperature of the air-cooled fuel cell stack at 30 ℃;

step A5: with P_AWhen the temperature of the air-cooled fuel cell stack is kept stable, the cathode fan PWM signal is stepped down to enable the temperature of the air-cooled fuel cell stack to be stepped up until the output voltage of the stack begins to attenuate rapidly, the stepped down reduction of the cathode fan PWM signal is stopped, and the temperature corresponding to the maximum value of the output voltage of the stack in the period is the reference temperature when the load current value is I;

step A6: setting the load current as different fixed values, respectively repeating the steps A4-A5 to obtain reference temperatures under different load current values, and drawing to obtain a reference temperature-current curve.

5. The environmental disturbance resistant air-cooled fuel cell cathode control method according to claim 4, wherein Δ P is 1% to 10%.

6. The environmental disturbance resistant air-cooled fuel cell cathode control method according to claim 1, wherein the protective activation resistance-current curve is obtained by:

step B1: opening an anode hydrogen inlet valve and adjusting the hydrogen inlet pressure;

step B2: starting a cathode fan to provide oxygen for the air-cooled fuel cell stack;

step B3: setting the load current as a fixed value I, and starting the air-cooled fuel cell stack to work;

step B4: by adjusting the duty cycle of the cathode fan PWM signal to P_AKeeping the temperature of the air-cooled fuel cell stack at 30 ℃;

step B5: applying alternating current disturbance current with the amplitude being X percent of the load current to the air-cooled fuel cell stack, and measuring and calculating to obtain the activation resistance of the current air-cooled fuel cell stack;

step B6: with P_AWhen the delta P is a fixed step length as an initial value, and the temperature of the air-cooled fuel cell stack is kept stable as a judgment standard for carrying out next descending, the PWM signal of the cathode fan is gradually reduced in a stepped manner, so that the temperature of the air-cooled fuel cell stack is gradually increased in a stepped manner; testing the activation resistance of each step process until the output voltage of the electric pile begins to decay rapidly, stopping the step-down reduction of the PWM signal of the cathode fan, and obtaining the last measured activation resistance before the output voltage of the electric pile begins to decay rapidly, namely the protection activation resistance when the load current value is I;

step B7: setting the load current as different fixed values, respectively repeating the steps B4-B6 to obtain the protection activation resistance under different load current values, and drawing to obtain a protection activation resistance-current curve.

7. The method for controlling a cathode of an air-cooled fuel cell according to claim 6, wherein X is 1 to 10.

8. The method for controlling the cathode of the air-cooled fuel cell resistant to environmental disturbance according to claim 6, wherein the frequency range of the AC disturbance current is 0.2-500 Hz.

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