A Comparison of Isolated DC-DC Converters for Microinverter Applications

Developing a cost-effective and high-efficiency microinverter to interface a single photovoltaic (PV) module with residential ac voltages is not an easy task taking into account the cost target set by the Department of Energy (DOE) of 18 cents per Watt and the requirements imposed by the National Electric Code (NEC) which lead to galvanic isolation. This paper presents a detailed analysis of three isolated topologies which are the top candidates for the dc-dc stage of a two-stage microinverter. The considered topologies are the flyback, interleaved flyback and push-pull converters. A complete set of design equations for each topology is presented and used for designing the dc-dc stage of a microinverter system with the goal of comparing the ratings of the active and passive components since these affect system cost. Validation of the design equations are done through PSpice simulations.