Hybrid DCM/CCM Modulation Strategy for Dual-Active-Bridge Microinverter

In response to the increasing demands for high efficiency, convenience, and low cost in micro-photovoltaic grid-connected inverters, this paper investigates a dual active bridge (DAB) microinverter. This microinverter is designed to achieve high power density in the conversion of electrical energy while facilitating soft switching across a wide range of grid voltages. The operation of the inverter can be categorized into discontinuous conduction mode (DCM) and continuous conduction mode (CCM), depending on the characteristics of the transformer leakage current. This paper introduces a hybrid modulation strategy that alternates between DCM and CCM by designing the trajectory of the primary-side switch drive duty cycle throughout the operating frequency cycle. This modulation strategy ensures that all switches operate with zero-voltage switching (ZVS) or zero-current switching (ZCS) under both heavy and light load conditions. Simulation results are provided to validate the proposed model and control strategy.