A Single-Stage AC/DC Bridge-Less Converter with an Adaptive Control Scheme and Reduced DC-Link and Output Capacitances for High Voltage EV Systems

This paper presents a new AC/DC step-up CLLC resonant converter with reduced dc-link and output capacitance and an adaptive control scheme for fully soft-switching operation for high-voltage EV systems. In the proposed converter, a closed-loop controller guarantees soft-switching operation and high-quality sinusoidal input current without a need for any auxiliary circuits. Moreover, the designed adaptive control system allows for replacing bulky dc-link and output filter capacitors with small capacitors that result in a high-power density, higher reliability, and reduced size converter system. Moreover, the proposed adaptive control scheme allows the converter to further narrow its switching frequency spectrum for output voltage regulation, resulting in an extended high-efficiency range while maintaining soft-switching operation. Furthermore, a variable frequency control algorithm is designed to regulate the converter's output voltage during its modes of operation. The performance of the proposed converter system is verified through a 2kW, 120Vac/800Vdc design.