Research On Energy Management Of Solid Oxide Fuel Cell Hybrid Power System

As a kind of green energy, Solid Oxide Fuel Cell(SOFC) has becoming more and more attractive. However, fuel cell can't follow the load change instantaneously because of its inherent output features. Therefore, auxiliary power(storage battery) must be introduced to SOFC system to realize fast load following. During the load following transient, the thermal and electrical characteristics of SOFC have to be considered together. Since the SOFC system experiments are time consuming and cost, semi-physical simulation platform was adopted to assist the research in this thesis.Firstly, a model was built for SOFC system on MATLAB platform. In the modeling process, every SOFC components was divided into certain nodes by finite volume method. Physical laws, such as energy conservation, mass conservation and mole fraction conservation, were followed in the models of every nodes. A model for the whole SOFC system was achieved by combining the models of every components together. Then, Kalman filter was used to estimate and control the State Of Charge(SOC) of the storage battery. Since the state space equations of storage battery was needed in the Kalman filtering method, a second order Resistance and Capacitance(RC) model was built and the model parameters was identified by the data from charge-discharge experiments of storage battery. A complete SOFC hybrid energy system was built by combining the SOFC model, storage battery model, DC/DC and DC power supply together on dSPACE platform. Finally, according to the controlling variables and control target of the SOFC hybrid energy system, a control strategy was designed. Feed forward control, PID control, state machine and hysteresis control were used in this control strategy. Simulation results proved that all the relevant issues of the four temperature constraints, fast load following, fuel starvation and storage battery SOC could be solved very well at the same time. Therefore, the models and control strategy proposed in this thesis were effective and the research achievement could provide a solid foundation of method and theory for physical design.