Design On Front-End DC/DC Converter For Fuel Cell Power System

Fuel Cell (FC) has various advantages such as the high efficiency of power generation and density, the feature of environment friendly, stability and so on, which makes it become one of the most foreground energy technologies in the distributed power system. Because of its elec-chemical characteristics, its output voltage varies largely as the load changes. Hence the power converter unit (PCU) is needed to adjust, control and manage the output of the power supply to produce the desired DC or AC power.In middle and small scale Fuel cell generation power system, the output voltage of the FC is always not very high and varies largely as the load changes. It is essential that a high-efficiency DC/DC converter connect the output of the FC and the grid for boosting the voltage of the FC and stabilizing the voltage of the output of the DC/DC converter for the inverter. The front-ended DC/DC converter in the Grid-connected fuel cell gerneration power system is studied in the paper.Firstly, the fundamental theory of the PEMFC used in our research is discussed and the output characteristic line is deduced. Based on the output voltage line, we choose the two-level structure of the Fuel cell generation system, and propose the fuctions the front-ended DC/DC converter of the FC generation power system should process. Secondly, making comparison of some normal DC/DC converters, we selects PS-FB-ZVS-PWM DC/DC converter as the front-ended DC/DC converter of a 5kW grid-connected FC generation power system. Thirdly, the detailed design of DC/DC converter's hardware and control software is presented in the paper. And our experiments prove that the DC/DC converter realizes the function outputting±380VDC for the half-bridge inverter in the case of inputting 85～120VDC in full range of output power, as well as the function of soft-start and various protection. Fourthly, the paper analyzes the loss distributing, and puts forward some methods to improve efficiency. Finally, the experiment results of DC/DC converter in single working state and in the online state is presented to prove the feasibility and the rationality of the design.