Applying a novel PMU to replace the large DC bus electrolytic capacitors in Fuel Cell power generation system

Fuel cell (FC) is considered as an attractive power source for the application of the distributed power generation system. A three-level power conversion system (PCS) for fuel cell is investigated. To suppress variation of the neutral point voltage of three-level inverter and prevent fuel cell from the low frequency current ripple under unbalanced load, a novel power management unit (PMU) and its control are proposed. It can complement the function of FC. In addition, PMU acts as DC bus capacitors, therefore the large DC bus electrolytic capacitors can be eliminated. Through analysis of low frequency current ripple flow path, the control strategy of PMU is derived. Finally, the proposed PMU with its control is verified by simulation and experiments.