High-efficiency power conversion for low power fuel cell generation system

This study presents a newly designed topology for a fuel cell energy source conversion in order to supply a highly reliable utility power. Because the fuel cell has the power quality of low voltage as well as high current due to the electrochemical reaction; a high step-up dc-dc converter is utilized for boosting the fuel cell voltage up to a constant dc-bus voltage for the utilization of later inverter. Moreover, a current-source sine-wave voltage inverter is designed in the sense of voltage-clamping and soft-switching techniques to enable the use of a smaller inductor in the current source circuit and the compression of the voltage stress across switches about two times of the dc-bus voltage. In this power conversion scheme, the output voltage has the salient features of lower distortion, fast dynamic regulating speed and insensitivity to load variation, even under nonlinear loads. In addition, experimental results via an example of a proton exchange membrane fuel cell generation system with 250-W nominal power rating are given to demonstrate the effectiveness of the proposed power conversion strategy. According to the experimental measure, the maximum power inverter efficiency is over 95 % and the total harmonic distortions for various load conditions are all within 1.1%.