Power Conversion And Control System Design For A7KW PEM Fuel Cell

Energy crisis and environment pollution, the two major issues of currentworld, make people to have a clear understanding of the importance ofdevelopment of new energy. Proton exchange membrane fuel cell (PEMFC)is widely concerned by the world because of its clean and high-efficiency,and many other advantages. However, since the PEMFC is a nonlinear,multi-input, and strong coupling complex system, the output voltage has thecharacteristics of instability and variability. That means the output power ofthe PEMFC should be controlled in real application. In order to match thedifferent loads, designing a power conversion and control system is necessaryfor the PEMFC power generation system.The objective of this paper is to design a power conversion and controlsystem for a7KW PEMFC, including the DC-DC converter main circuitdesign and control circuit design. The work mainly focuses on the followingaspects:(1)Based on the electrochemical model of the PEMFC, a simulationmodel of the7KW PEMFC was constructed in Matlab/Simulink. Theeffectiveness and operability of the simulation model were validated bycomparing the simulation curves with experimental data. The influences oftemperature and pressure on the output electrical characteristics of PEMFCwere analyzed based on the PEMFC model. That can be a reference for the corresponding power conversion system design.(2) The commonly used DC-DC converters were introduced. And basedon the output electrical characteristics of the PEMFC and correspondingdesign requirements, the synchronous buck converter was selected as themain circuit topology. The working principle of the synchronous buckconverter was analyzed, and the parameters of the components werecalculated. To verify the rationality of the design, an open-loop synchronousbuck converter simulation model was constructed in SimPowersystems.(3)Closed-loop control system was designed for the synchronous buckconverter, and the voltage and current double closed-loop average currentmode with incremental PI controller was used. And the PI control parameterswere designed in Simulink based on the small signal model of thesynchronous buck converter. And the effectiveness of the average currentmode control was verified by constructing integral simulation modelconsisting of PEMFC and synchronous buck converter which was controlledby the double closed-loop.(4)The hardware and control program design of the converter werecompleted based on the TMS320LF2407DSP. The hardware design mainlyincludes sampling circuit, driver circuit, and communication circuit etc. Thecontrol program monitors the system in real-time based on DSP，and it wasfor converter voltage regulation and circuit protection. Finally a prototype ofthe synchronous buck converter was made. The validity of the design wasverified through the test.