| This paper aims at a hybrid AC/DC power supply system with fuel cell and battery mixed energy supply.According to the characteristics of wide voltage range and slow response speed of fuel cell,the bus voltage control of the system is studied.Furthermore,the energy management scheme for maximizing the utilization of fuel cells is further studied.First,the paper determines the structure of power supply system.Both the solid oxide fuel cell and the lithium battery are connected to the DC bus through the Buck/Boost circuit,and the AC load is powered by the DC/AC inverter,forming an AC-DC hybrid power supply system.The average model of the cascade system composed of lithium battery energy storage unit and inverter is established,and the nonlinear control scheme based on Lyapunov control theory is studied.DC bus voltage is controlled by lithium battery and AC side voltage is controlled by inverter.Four simulations are used to verify that the controller can guarantee the stability of cascade system under large disturbance.Secondly,the economical operation characteristics of fuel cell are analyzed.The mathematical model of the fuel cell was established to analyze its performance,and the power output characteristics of the system were studied by observing the V-I and P-I characteristic curves.Combined with the loss of fuel cell itself and the loss of auxiliary system,the economic operating zone of fuel cell is analyzed to provide the basis for further system energy management.The average model of fuel cell converter is established,and the fuel cell is incorporated into the DC bus in current control mode by using Lyapunov control.Then,the energy management scheme of the system is designed.Analyze the equivalent circuit of lithium battery,evaluate the energy loss during charge and discharge.Based on the economic operation zone of fuel cell,the energy regulation scheme is proposed to ensure that the fuel cell operates in the economic operation zone,reduce energy consumption and increase energy supply capacity.The simulation platform of MATLAB/Simulink hybrid power supply system is built,and the feasibility of the proposed energy regulation scheme is verified by analyzing the operation regulation of five operating modes.Finally,the experimental platform of the hybrid power supply system is built,and the superior performance of the proposed Lyapunov controller and the effectiveness of the proposed energy management scheme are verified through three groups of experimental conditions. |
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