Energy Management And Maintenance Of Multi-Stack Solid Oxide Fuel Cell System

Solid oxide fuel cell（SOFC）,as one of the extremely popular new energy sources in the 21st century,can directly convert the chemical energy in the fuel into electric energy through electrochemical reaction.It has the remarkable advantages of high efficiency and less pollution and so on.Due to the limited power of a single SOFC stack,there are limitations in the application of high-power load demand scenarios,such as rail trains and data centers.Therefore,multi stack SOFC system based on a certain topology is often used to supply energy.Considering that there are multiple energy sources in the system,it is necessary to formulate an appropriate energy management strategy to allocate the load demand.At the same time,aiming at the failure of the stack due to degradation,the stack maintenance strategy is formulated to supply the load demand successfully.The main research of this thesis includes:Firstly,based on the theories of electrochemistry and thermodynamics,a multi stack SOFC power generation system model is built,including subsystems such as SOFC stacks with degradation,SOFC peripheral,battery and DC\DC converters.Combined with the experimental data,the polarization curve and degradation trajectory of the voltage are analyzed.The maximum error is 4.7%,which verifies the reliability of the model.Then,aiming at the degradation and performance differences of the stack in the system,an adaptive energy management strategy to minimize the fuel consumption of the system is designed.The fuel consumption model of the system is established based on the principle of equivalent fuel consumption,and identify model parameters based on the recursive least squares algorithm,which can compensate the performance change caused by stack degradation.The distributed consensus optimization algorithm is used to solve the optimization model to obtain the expected power of each energy component.Based on the PID controller,the output current control plans of the stacks are designed to make each stack quickly track its expected power,so the energy management of the multi stack system has finished.The equal allocation and chain allocation strategies are compared with the proposed strategy,and the results show that the proposed strategy can effectively reduce the fuel consumption of the system and give play to the performance advantages of the system.Finally,aiming to decrease the maintenance cost of the system,a multi stack group maintenance strategy is designed based on preventive maintenance,which solves the problem of affecting system energy management due to stack failure.Based on the adaptive Wiener process,the degradation trend of the stack is analyzed,and the failure rate function of the stack is obtained,and then the model of the system maintenance cost is established.Analyzing the "set partition problem" to solve the optimization model,the grouping and cycle of group maintenance are obtained,and the group maintenance of multi stack system is realized.Compared with other maintenance strategies,the results show that if the failed stack is not treated,the system cannot afford the load.At the same time,compared with the independent maintenance strategy of the stacks,the proposed strategy can reduce the operating cost of the system.