Modeling Analysis And Control Strategy Research Of Hydrogen Fuel Cell Engine Cooling System

Proton exchange membrane fuel cell(PEMFC),as a kind of clean power source,can convert hydrogen energy into electric energy.Due to its high power conversion rate,low operating temperature and high energy density,more and more people pay attention to it.Operating temperature affects the moisture,catalyst activity,chemical reaction rate and the life of fuel cell.Temperature control level on the dynamic performance and service life of PEMFC have a significant impact,equipped with efficient cooling system,formulating appropriate control strategies,it is very important to maintain the battery to work properly,improving the performance of the fuel cell,improve the reliability of the fuel cell and extend the service life of the battery,the study of PEMFC is an important part.Therefore,in order to give full play to the power generation performance of PEMFC,it is necessary to master the influence law of temperature on the battery output characteristics,and carry out the research on the cooling system model and its control strategy.In this paper,the influence of temperature on the performance and parameters of fuel cell is analyzed firstly,and then the requirements of coolant temperature control are proposed.In order to stabilize the temperature of PEMFC inlet coolant within the ideal temperature range,the structure of the cooling system and the overall scheme were designed.The deionized water was selected as the coolant in the system.Based on the principle of energy conservation,and based on the mathematical model and experimental data,a semi-empirical and semi-mechanism model of the PEMFC cooling system was established.Secondly,for the cooling system of PEMFC,the maximum overshoot of the coolant inlet temperature,the response time,the control precision and the temperature difference between the coolant inlet and outlet are taken as the control indexes.The control strategy was developed to realize the cooling requirements,the pump speed was controlled by feedforward and feedback,and the feedback PID control was added on flow following function control control.The radiator opening is controlled by feedback,and the traditional PID control,fuzzy PID control and variable domain fuzzy PID control are applied to the radiator.By adjusting the speed of the circulating water pump to change the coolant flow in the system,by adjusting the opening of the radiator to change the amount of air into the radiator.Finally,the result of flow following function to control the pump speed and PID control to adjust the radiator opening is taken as the benchmark.According to the test by emulator,the control results were compared in different control strategies.By comparison,it can be seen that the control of the pump speed affects the temperature difference between the inlet and outlet of the coolant.The greater the speed,the greater the coolant flow in the system and the smaller the temperature difference.The temperature difference of the coolant at 2500g/s is 2.57℃ less than that at 1500g/s.The greater the radiator opening is,the greater the air flow into the radiator is,the lower the inlet coolant temperature is.When the radiator opening is increased from 30% to 90%,the inlet temperature can drop by 10℃.The maximum overshoot of inlet coolant can be reduced by 5.42℃ after adding feedback control to the control of water pump.The feedback control of the radiator can control the temperature difference between the inlet and outlet coolant of PEMFC within 4℃,and the temperature fluctuation of the inlet coolant is stable within ±1℃.However,with different control methods,the maximum overshoot,response time and control precision obtained after simulation are different.Under the premise of feedforward and feedback combined control,the variable domain fuzzy PID control method has the best control effect on inlet temperature.The maximum overshoot of inlet coolant temperature is reduced by 8.89℃,and the adjustment time is advanced by 3.64 s.The control precision of fuzzy PID control is the highest,which can reach below 0.01℃,but the maximum overshoot is only reduced by 8℃,and the result is a little worse.The result of traditional PID control is the worst,the maximum overshoot is only reduced by 5.4℃,and the adjustment time is not advanced.