A transformerless step-up resonant converter for grid-connected renewable energy sources

Resonant converters can achieve soft-switching for switching devices and they are very suitable for high-power applications. This paper presents a resonant converter which is suitable for grid-connected renewable energy sources. The converter can achieve high voltage-gain using LC parallel resonant tank. It is characterized by zero-voltage-switching (ZVS) turn-on and nearly ZVS turn-off as well as zero-current-switching (ZCS) turn-off of rectifier diode. In addition, compared to conventional resonant converter, the variation of switching frequency of the proposed resonant converter is smaller over the entire load range. The operation principle of the converter and its resonant parameter selection is presented in the paper. A 1kW prototype is built in the lab to verify the effectiveness of the converter.