Equivalent voltage and current models for PEM fuel cell generation system in grid-connected systems

Fuel cell is an important distributed generation in micro-grid and the modeling and control for fuel cell power generation systems have attracted the attention of many researchers. Proton exchange membrane fuel cell (PEMFC) modeling for grid-connected is studied in this paper. The simulation model of fuel cell stacks with DC/DC and DC/AC converters is built in Matlab/Simulink. The P/Q Control strategy is adopted in the PEMFC generation system in grid-connected system. A equivalent voltage source circuit with a resistance and an inductance is built for the PEMFC generation system in grid-connected mode. This equivalent circuit is used to analyze the dynamic behaviors of the distribution system or the micro-grid with PEMFC power systems. In addition, an equivalent current source circuit with a resistance, a capacitance, and an inductance is built for the PEMFC generation system. The transfer function of power model can be gotten by the equivalent circuit. It can be used in the analysis and design of power follow-up control system for a distribution or micro-grid. Data fitting method is employed to identify the parameters of the equivalent circuit, and the parameters are tested by the simulation model in various disturbances. When the grid is stability, the output power is positive correlation to the output current. So the output power transfer function of the PEMFC in the P/Q model can be deduced according to the current source model. This transfer function can be used in the power flow control in microgrids.