Online Backflow Power Minimization Modulation Technique for Single-Stage High-Frequency Link Rectifier

This article proposes an online backflow power minimization (OBPM) modulation for single-stage single-phase high-frequency link rectifier (HFLR). The HFLR topology consists of a cycloconverter and a full bridge (FB) rectifier, interconnected via a high- frequency (HF) transformer to form a single-stage power conversion structure. The proposed hybrid control strategy combines frequency modulation and extended phase shift (EPS) method to enable linear power control, which significantly simplifies the complexity of the controller design. Besides, the high- and low- frequency interleaved control is employed in the cycloconverter to reduce the HF conduction loss. Moreover, the optimal phase-shift ratios were derived to minimize the backflow power. Through the proposed OBPM strategy in this article, the peak current can be reduced. Furthermore, the rectifier implements soft switching operation of all switching devices without adding additional components or modifications to the baseline topology. Thus, the switching losses can be reduced and the system efficiency is increased. Finally, a 500 W prototype was built to experimentally confirm the validity and feasibility of the proposed control strategy.