Modeling And Control Of Solid Oxide Fuel Cell/Micro Gas Turbine Hybrid Power Generation System

The solid oxide fuel cell/micro gas turbine(SOFC/MGT) hybrid power generation systemis an advanced efficiency and environmentally-friendly novel power generation technology,which has a wide application prospect in the field of future distributed generation. However,at present the demonstration hybrid power plant has been developed abroad. In China thehybrid system is still in the early research stage, and the practical equipment for the systemhas not been built.Therefore, according to some experience on the hybrid power generation system in theworld, a dynamic model is established firstly, and then the performance simulation analysisand dynamic optimization are carried on, lastly the integral control strategy for theSOFC/MGT hybrid power generation system is researched in the dissertation. By simulationanalysis, the SOFC/MGT hybrid power generation system can operate steadily and meet theload power requirements with high efficiency. The dissertation can provide valuable theoryinstructions for developments and applications of real hybrid power generation system. Themain contributions and achievements of this dissertation are given below:1. Establish the dynamic model of a SOFC/MGT hybrid power generation system. Firstly,according to the demonstration device built by the Siemens Westinghouse Power, thepertinent literatures and practical operating experience, the topping cycle topologicalstructure is designed for an anode recirculation SOFC/MGT hybrid power generationsystem. And then, for the heavy structure, many performance parameters and complexcharacteristics, the dynamic model is established by modularization modelling method.According to the ideal gas equation, mass conservation law, energy conservation law,thermodynamics formula and electric power conversion, the components models of ananode recirculation SOFC, micro gas turbine and a power conditioning system are builtrespectively in MATLAB/SIMULINK environment. Lastly, according to the designedtopological structure, each submodular is connected to make up of the integrateddynamic model for the whole hybrid power generation system. The simulation results show that the model is able to reflect the steady and dynamic characteristics of the hybridsystem correctly, so it can be used in the performance analysis, dynamic optimizationand control design of the hybrid system. Moreover, owing to the part structures andparameters easily modified, the dynamic model of the hybrid system possesses thegeneral applicability. It can be used not only for the designed topological structure in thesimulation research, but also for the other researches of similar hybrid power generationsystems by simply changing.2. The dynamic optimization problem of operating parameters for the SOFC/MGT hybridpower is introduced in detail. At present, the researches mainly focus on the processdesign optimization. The optimal hybrid structure and circulation mode are determinedby special optimization method. However, research about the optimal operatingparameter is very little. For the dynamic optimization of the hybrid system, firstly, anovel iteration partial swarm optimization (PSO) algorithm is proposed, which is madeup of iteration dynamic programming and adaptive immune particle swarm optimization.For the algorithm, firstly the control variables are discretized and the improved particleswarm optimization is used to search for the best solution of the discretized controlvariables. And then the benchmark is moved to the acquired optimal values in thesubsequent iterations and the searching space contracts at the same time, hence theoptimization performance index and control profile could achieve the best valvegradually through iterations. The optimization algorithm is proved to be effective by alarge number of examples. According to the designed dynamic optimization model of thehybrid power generation system, the novel iteration PSO algorithm can calculate theoptimal operating parameters. Tracking the demanded load and obtaining the highestgenerating efficiency are the goal function, and the dynamic model and safe operationrequest are the constraints of the dynamic optimization model for the hybrid system.Lastly, substituting the optimal parameters into the established dynamic model of thehybrid system, the optimal SOFC output power trajectory can be obtained, which acts asthe SOFC output power setpoints in order to closed loop optimized control.3. The integral control design is proposed and tested for the SOFC/MGT hybrid powergeneration system. At present, documents focus on controlling the specific performancesof hybrid system, and the integrated control research is lack. But for the close nonlineardynamic characteristics and some parameters couplings of the system, it is significant forreal applications that the system is controlled to operate steadily with all idealperformances.Therefore, according to the performance analysis and dynamicoptimization results, the integrated control design is proposed and tested for the hybridsystem based on the dynamic model.In this dissertation, for the complex characteristics of the hybrid system, the system control is separated to some processes. An improvedneural network predictive controller is designed for tracking the system output power. APID decoupling controller based on a dynamic RBF neural network is put forward forsystem temperature decoupling control. An improved single-neural unit adaptive PIDcontroller is utilized for steady fuel utilization.The SOFC output voltage is transformed toan ideal amplitude alternate current voltage by sliding mode variable structure controlmethod. During the power control, the optimal operation trajectory results obtained fromthe improved iteration PSO algorithm are successfully modeled and predicted by meansof the least squares support vector machine. This facilitates the optimal SOFC outputpower setpoints under various loads. And then, these above controlled processes areintegrated to realize the integral control research of the SOFC/MGT hybrid powergeneration system. Under the step power loads, the simulation results show that the mainoperation parameters are kept in the ideal steady state, and the hybrid system can track thedesired power with high system efficiency.