Study On Interval Lqg Control Strategy For Solid Oxide Fuel Cell-gas Turbine Hybrid System

Solid oxide fuel cell(SOFC)has the advantages of high operating temperature,multi-fuel sources compatible,long life cycle,which makes it possible to be widely used in distributed power generation systems.However,its energy efficiency is relatively low when SOFC works alone,which severely limits its promotion and application.Combining SOFC and gas turbine(GT)for power generation cannot only significantly improve the overall efficiency of the system,but also reduce environment pollution,which attracts attentions from distributed power plants.Solid oxide fuel cell-gas turbine(SOFC-GT)hybrid system is a complex system with large-scale,various control parameters,and mutual coupling of components.Therefore,it is necessary to establish its dynamic model and design a suitable control strategy to accurately describe the system performance and to ensure the stable operation of the system.For a SOFC-GT hybrid system,considering the interval uncertainty of each parameter and the disturbance of ambient temperature and fuel concentration,this thesis constructs its dynamic model and proposes a LQG control strategy based on interval analysis.First of all,the interval analysis theory and the Chebyshev method which can effectively reduce the high valuation of interval results are studied,which provide a theoretical foundation for solving the system model of interval uncertainty.Secondly,the underlying circulating structure of the SOFC-GT hybrid system is improved and the working principle of each component of the SOFC-GT hybrid system and the transfer relationship of energy flow are analyzed.Based on the mass conservation equation,energy conservation equation,thermodynamic formula and electric power conversion formula,the SOFC-GT hybrid system dynamic model is established.After linearizing the dynamic model of the nonlinear system,the Hankel matrix singular value method is used to reduce the dimensionality of the system to obtain a simplified model of the system.Thirdly,the interval LQG controller is designed based on the interval analysis theory and the linear LQR controller,and is applied in centralized optimal closed-loop control on the uncertain system.Furthermore,a local proportional feedback loop is added to stabilize GT shaft speed,and an interval extended Kalman filter is used to improve the robustness of the results and a power integrator is used to track the power of the system.Finally,a long-term simulation of the SOFC-GT hybrid system is carried out in MATLAB-SIMULINK.The control results of SOFC temperature,SOFC current,SOFC voltage,combustor temperature,combustor fuel and GT shaft speed based on the interval LQG control strategy,the ordinary LQR control strategy,and the decentralized control strategy are compared.The simulation results verify the effectiveness and superiority of the interval LQG control strategy in the robustness and lifetime of the SOFC-GT hybrid system.The main novelty of this thesis can be summerized as follows:(1)Based on the improved underlying circulating structure of the SOFC-GT hybrid system,the dynamic model of the SOFC-GT hybrid system is established.The model is simple to integrate,easy to control,suitable for simulation and can accurately describe the system performance.(2)Based on the uncertainty of each parameter and disturbance,an interval LQG control strategy is proposed,and the system robust interval that can ensure stable operation of the system is obtained.This robust interval can be used as a verification standard for the correctness of other control strategies.