Design of LCC resonant converter for renewable energy systems with wide-range input voltage

This paper deals with the design of a 21 kW series-parallel resonant converter, that is, LCC resonant converter that can be effectively used for intermediate power conversion from renewable energy sources to a battery energy storage system. The developed LCC resonant converter was made of a high-frequency transformer and a relatively high parallel capacitance for voltage boosting in order to cover a wide range of input voltage (200 - 400 V) with high-efficiency. Furthermore, the optimized design of resonant tank parameters described in this paper helped reduce or make negligible the turn-off loss of insulated gate bipolar transistors by increasing the lossless snubber capacitance. In this paper, the detailed design of the proposed converter, including the selection of the snubber capacitor and the determination of transformer turns ratio on the basis of the converter specifications, is described along with operational mode analysis and PSpice simulation. In addition, a simple structure of a controller for a battery charging application that requires both constant current and constant voltage control is described. A gate driving method for zero voltage switching was introduced to compensate the difference of snubber capacitor discharging time. Finally, the developed LCC resonant converter was tested with a resistive load, and the results showed a maximum efficiency higher than 90% in the input voltage range of 200-400 V. A long duration operation test was conducted to verify the reliability and robustness of the designed converter.