Research On Power Optimal Management And Control Of Solid Oxide Fuel Cell/Lithium Battery Hybrid System

Solid Oxide Fuel Cell(SOFC)as a green energy industry has great scientific research significance and market space.SOFC power system has characteristics of slow dynamic responses of output power.When the power demand of load suddenly rises or drops in a short time,fast power tracking cannot be achieved if power system relies solely on SOFC.In this thesis,lithium battery was used as auxiliary power source cooperating with SOFC to generate electricity.At present,most researches on the hybrid energy management only considered State of Charge(SOC)of lithium battery,and didn't consider the influence of State of Health(SOH).In this thesis,filter algorithm was designed to achieve combined estimate of the two state values,and fuzzy control algorithm was designed to ensure the hybrid energy system to perform power tracking safely and efficiently.Firstly,this thesis made use of MATLAB/Simulink to build model of the research object——500W pure hydrogen solid oxide fuel cell system.The model of stack and auxiliary unit were established based on the characteristics of electrochemical reaction and thermal dynamic of the system,and complete the integration of system model.Then,a physical system was built to study the parasitic power and system efficiency under different power generation;Secondly,to test whether the model is consistent with the performance of actual stack,this thesis built stack testing system.Through the experiment of temperature rising with stack,this thesis tested U-I-P characteristics of fuel cell under different temperatures and fuel utilization rates as well as the power tracking characteristics of stack.The effectiveness of the stack model was also verified in this thesis;Then,the state-space model of lithium battery was built.This thesis chose the most commonly used second-order RC equivalent circuit model to build SOC and SOH estimation model respectively.The model parameters were identified by designing charging and discharging experiments.Based on the model,the estimation of SOC and SOH of lithium battery were carried out by Particle Filter(PF)algorithm;Finally,a T-S fuzzy controller was designed to control the output current of lithium battery to ensure that its SOC was within a reasonable range during the process of co-generation.In order to facilitate the simulation of hybrid energy system and test the control algorithm,this thesis built a hardware-in-the-loop simulation platform using dSPACE.The control algorithm was downloaded to the control board and combined it with the system model and electrical equipment for on-line simulation.Then the algorithm was tested with irregular load power changes to verify its effectiveness.The result showed that the algorithm could effectively solve the technical problem of slow dynamic response of SOFC power tracking,and realized the protection of SOC for lithium battery.