An Improved Adaptive Sinusoidal Single Phase Shift Modulation for Bidirectional Single-Stage Onboard EV Chargers

Single-stage onboard chargers (SSOBCs) integrate traditional two-stage structures of front-end power factor correction (PFC) AC/DC converter and back-end DC/DC converter, which increases compactness and reliability. However, PFC function and DC voltage regulation need to be achieved simultaneously within only a single converter. Hence, it is challenging for SSOBCs to obtain high efficiency with a unity power factor (PF) under a wide operating range. To address the above issue, this paper presents an adaptive sinusoidal single phase shift (ASSPS) modulation strategy that introduces a sinusoidal single phase shift for maintaining a high PF. Firstly, the proposed adaptive technique solves the high current issue at the zero-crossing point of grid voltage based on different operating modes, significantly decreasing conduction loss and increasing efficiency. Moreover, the full-range zero-voltage switching (ZVS) technique on the secondary bridge can be achieved under universal specification from 300 V to 800 V battery voltage, which reduces the switching loss. The proposed ASSPS modulation has only one variable, which is easy to implement for hardware design. Finally, a generalized design guideline of the 6 kW SiC-based bidirectional SSOBC is proposed, and the prototype is built. The experimental results validate the operating principle and ZVS achievement of the proposed ASSPS modulation. Compared with the traditional modulation methods, the proposed ASSPS modulation increases the peak efficiency by 1.1%.