Output Optimization Control Of PEMFC Based On Sliding Mode Control

With the development of the global economy,the development and utilization of high-efficiency and clean new energy has become the focus of attention in the world today.In order to realize the commercialization of the proton exchange membrane fuel cell(PEMFC),it is necessary to comprehensively consider the output performance optimization of the PEMFC system.As the two types of PEMFC,air-cooled and water-cooled fuel cells are suitable for different application scenarios due to their different characteristics and structural design.Aiming at the impact of the coupling interaction between the PEMFC gas supply and heat dissipation subsystems on the output performance of the PEMFC system,Air-cooled and water-cooled PEMFC system experimental platform(including the hardware design of the control board and the Lab VIEW host computer software)was built.The output characteristics of air-cooled and water-cooled PEMFC systems under different operating conditions such as temperature,load,and air supply changes are studied,which lays an experimental foundation for optimal control of system output performance.Aiming at the net power optimization problem of the air-cooled PEMFC system,according to the net power characteristics obtained based on the experimental platform,the influence of the stack temperature and load changes of the air-cooled PEMFC system on the net power of the system is analyzed.A control method of maximum net power strategy based on sliding mode variable structure control(SMVSC)is proposed.This method obtains the operating temperature of the stack at the maximum net power point of the system by designing the maximum net power regulator of the system.At the same time,Lyapunov function is used to prove the stability of the closed-loop system under sliding mode control,and reasonable control parameters are selected to realize the stable control of the system.Through the air-cooled PEMFC system experimental platform,comparing traditional PID control and the difference in response characteristics of SMVSC when load changes,it is verified that SMVSC is better than traditional PID control in steady-state characteristics,dynamic characteristics and PEMFC net power output.Aiming at the "oxygen starvation" and "oxygen saturation" problems of the water-cooled PEMFC system,according to the net power characteristics obtained on the experimental platform,the influence of the operating area of the water-cooled PEMFC system on the output performance of the system is analyzed.A control method of net power hierarchical control is proposed.The upper control was based on the offline+online net power optimization algorithm.Feedback control based on super-twisting algorithm was used as the lower control.The super-twisting algorithm was used to replace the traditional PID feedback control.In the hardware-in-the-loop mode,the system steady-state and dynamic output characteristics of the net power hierarchical control,P&O algorithm and traditional PID control are compared.It is verified that the net power hierarchical control can stabilize the PEMFC system at the best advantage of the oxygen excess ratio.