High efficiency DC/AC power converter for photovoltaic applications

Abstract

This thesis presents the development of a microinverter for single-phase photovoltaic applications that is suitable for conversion from low-voltage (25-40V) DC to high voltage AC (e.g. 240VAC,RMS). The circuit topology is based on a full-bridge series resonant inverter, a high-frequency transformer, and a novel half-wave cyclo-converter. The operational characteristics are analyzed, and a multidimensional control technique is utilized to achieve high efficiency, encompassing frequency control and inverter and cyclo-converter phase shift control. An experimental prototype is demonstrated in DC/DC conversion mode for a wide range of output voltages. The proposed control strategy is shown to allow for accurate power delivery with minimal steps taken towards correction. The prototype achieves a CEC averaged efficiency of approximately 95.1%. Guidelines for optimization are presented along with experimental results which validate the method.