Analysis and Implementation of Phase Synchronization Control Strategies for BCM Interleaved Flyback Microinverters

A flyback converter that operates in the boundary conduction mode or discontinuous conduction mode has been widely used in microinverters. Placing two flyback converters in parallel and utilizing interleaving can extend the power range of microinverters. Interleaving phases between the two converters should be carefully regulated in order to reduce the switching current ripple. In this paper, two open-loop phase synchronization methods are put forward and compared for the interleaved flyback microinverters utilizing the master-slave control principle. The comparison result shows that stable phase regulation can be achieved if synchronization is triggered at the instant when the master converter's primary switch is turned OFF. However, the switching loss will be increased with the transformers' magnetizing inductances mismatch between the two interleaved converters. To solve this problem, a novel closed-loop interleaving phase synchronization control method is proposed in this paper to guarantee high efficiency and stable operation at the same time. Simulation platform together with a 200-W prototype have been built to verify the proposed control methods. These results demonstrate that the proposed closed-loop interleaving phase synchronization control method can achieve high efficiency while maintaining stable phase synchronization for the interleaved flyback microinverter.