Research On High-Gain Three-Port Converter And Energy Management Strategy Of PEMFC Hybrid Power Supply System

Proton Exchange Membrane Fuel Cell(PEMFC)is a new type of power generation device that directly converts hydrogen energy into electrical energy.Aiming at the problems of PEMFC with low voltage and high current,slow dynamic response,and difficulty in self-starting,this paper proposes a high-gain three-port DC-DC converter for PEMFC hybrid power supply system based on the switched capacitor unit;And according to the working characteristics of the three-port,a forget-state machine energy management strategy is proposed,which solves the system instability caused by the excessive change of the duty cycle during mode switching.The main research contents of this paper are:(1)Based on the working characteristics of PEMFC,a PEMFC hybrid power supply system is designed,and a simplified model of PEMFC is established.First,the design scheme of the PEMFC hybrid power supply system is described in detail from the four aspects of the hybrid power supply system topology,auxiliary power supply selection,three-port DC-DC converter design,and energy management strategy design;Then,a PEMFC output voltage model was built,and the correctness of the model was verified by comparing the simulation data with the measured data,which provided an accurate model for system simulation and PEMFC simulator.(2)Aiming at the characteristics of low voltage and high current of PEMFC and the problem of low voltage gain of non-isolated three-port,a high-gain three-port DC-DC converter for PEMFC hybrid power supply system is proposed.This converter is based on Boost nonisolated three-port converter and switched capacitor unit.There are three working modes,each of which has a higher voltage gain.Because the converter adopts the combination method of adding the power flow path,the battery charging and discharging control is simpler.(3)Aiming at the problem that the three-port converter shares the switching tube,a forgetstate machine energy management strategy is proposed.When the mode is switched,the output value of the original PI controller is multiplied by the forgetting factor and then assigned to the PI controller in the new mode,which effectively solves the system instability caused by the excessive change of the duty cycle when the mode is switched.In addition,the particle swarm optimization algorithm is used to tune the PI parameters,which improves the tuning efficiency and accuracy;the fractional-order PI is used to control the current loop to improve the dynamic performance of the system;the system simulation model is built,and the effectiveness of the energy management strategy proposed in this paper is verified through simulation.(4)In order to verify the rapidity and stability of the PEMFC hybrid power supply system,an experimental platform for the PEMFC hybrid power supply system was built on the basis of software and hardware design.The experimental results show that the PEMFC hybrid power supply system designed in this paper can switch between modes according to the change of load demand power,has good dynamic performance,realizes the smooth cut-in and cut-out of the battery,and completes the power distribution of PEMFC and battery.