Research On Fuel Cell/Battery Combined Power Supply System Based On Partial Power Conversion

The reduction of fossil energy reserves promotes the development and application of renewable energy such as solar energy,wind energy and hydrogen energy,and promotes the research of microgrid system containing renewable energy.Hydrogen fuel cell is popular in microgrid system due to its advantages of cleanliness,high efficiency and transportability,but its response is slow and it also be affected by the transmission efficiency of the converter in the microgrid system.In order to solve the problem of fuel cell characteristics in microgrid system,a fuel cell(FC)/battery(BAT)combined power supply system based on partial power conversion(PPC)is established and studied in this paper.Firstly,this paper analyzes the structure of FC/BAT combined power supply system.The principle of PPC technology is analyzed and applied to the fuel cell subsystem.The basic structure and characteristics of solid oxide fuel cell(SOFC)are described.Combined with PPC technology,the isolated full bridge(IFB)converter is determined as FC converter.The working principle and mode of IFB converter are described and analyzed and modeled.The basic characteristics and control methods of the battery in the energy storage subsystem are described,and the structure and control methods of the three-phase converter subsystem are analyzed.Secondly,the single SOFC lumped parameter model was established and its steady state and dynamic characteristics were analyzed by simulation.The output power characteristics of FC in the economic operation mode and the maximum power operation mode,as well as the response time scale characteristics of FC,and the compensation of response speed between FC and the battery are analyzed.After linearizing the FC model,a small signal model is established by combining the FC converter with the FC model.The control model of FC and FC converter is constructed and the regulator is designed.Then,the power routing control scheme of FC/BAT combined power supply system in grid connected and island mode is designed.In the grid connected mode,the three-phase converter controls the DC bus voltage,the FC converter controls the output power of the fuel cell,and the battery regulates the charging and discharging state according to the instructions.At the same time,the pulsation of FC in the system is suppressed under the coordinated control strategy.In island mode,FC converter controls the output power of fuel cell,three-phase converter controls AC load,battery converter controls DC bus voltage and battery current to regulate system energy.Finally,the FC converter parameters were designed,the simulation circuit of the1 KW FC/BAT combined power supply system was built by MATLAB /Simuink software,and the system experimental platform prototype was built to verify the effectiveness of the proposed system control scheme.