GaN based transformer-less microinverter with extended-duty-ratio boost and doubly grounded voltage swing inverter

Microinverters are capturing the roof-top-PV market due to their plug and play feature, easy installation, and higher power yield under partial shading condition. This paper explores a converter for the transformer-less microinverter with extended-duty-ratio (EDR) boost as the DC-DC stage and doubly grounded inverter as the DC-AC stage. EDR boost is a hybrid of the interleaved boost and switched capacitor concept which has the advantage of providing high gain while simultaneously maintaining reduced voltage and current stress on most of the switches. The inductor currents are interleaved, reducing the equivalent ripple on the converter input current and the inductor power loss. The doubly grounded voltage swing inverter has the advantages of reduced capacitor requirement for 120 Hz power decoupling and zero capacitive-coupled common-mode ground currents, critical for transformer-less PV inverters. Also through dynamically variable DC-link with large voltage swing approach the decoupling capacitor is reduced allowing an all film capacitor implementation. A 300 W GaN based inverter prototype with 20 V-40 V DC input and 120 V, 60 Hz AC output and operating at switching frequency of 100 kHz has been developed to validate the converter's operation in hardware.