Research On Air Supply Control And Energy Management Of Marine PEMFC System

Polymer Electrolyte Membrane Fuel Cell(PEMFC)has the advantages of high energy utilization,zero pollution,low operating temperature,etc.It is one of the most promising clean energy sources.In order to ensure the stability and efficiency of PEMFC operation,the air supply system needs to be controlled in real time to maintain the stability of the excess oxygen ratio.However,the ship’s load fluctuates drastically under variable load conditions,and the PEMFC alone will bear the power output,which will cause a large overshoot of the over-oxygen ratio,and the rapid control of the over-oxygen ratio will easily cause the air compressor to deviate from the stable working area.In this regard,the introduction of battery and supercapacitor to form a ship hybrid power system and the design of energy management strategy according to the characteristics of ship operating conditions can improve the control performance of the air supply system,while improving the stability and economy of the whole energy supply system.This paper focuses on the PEMFC air supply control and energy management strategy as follows:(1)Based on the working principle of PEMFC,the PEMFC electro-gas model is established,which covers the PEMFC stack and a number of auxiliary equipment.The influence of peroxide ratio on PEMFC output net power under different current,temperature and membrane water content was analyzed,and the reference value of peroxide ratio control was determined.(2)Linearize the established PEMFC electro-gas model,construct a feedforward controller to analyze the stability,and introduce PID feedback control to form feedforward feedback control.For the problem of system linearization difficulties,the fuzzy controller is established and the fuzzy controller is optimized with genetic algorithm.The simulation results show that the genetic fuzzy controller has superiority in both response speed and steady-state error.(3)The energy management strategy of PEMFC hybrid system is proposed: aiming at the problem of slow load response of PEMFC,the output power of fuel cell is smoothed by frequency decoupling;aiming at the extreme differentiation problem of SOC of energy storage unit,the power balance of energy storage unit is corrected by fuzzy logic judgment method according to the SOC and primary power allocation state of the energy storage unit.In order to improve system safety and prevent damage caused by excessive charge and discharge,the charge and discharge threshold is set to establish an overcharge and overdischarge protection module.Considering the hydrogen consumption and system equipment loss,a hybrid power system value loss model is established to provide a basis for evaluating the economy of the system.The system functionality and superiority are verified from multiple perspectives,including frequency decoupling,SOC equalization control,overcharge and overdischarge protection,the influence of control strategy on PEMFC air supply control,and the influence of system value loss.