Renewable Energy Systems
Technical Lecture Session
Photovoltaic (PV) Inverters and Micro Inverters
Single stage inverters
This paper presents a single-stage series-resonant dual active half bridge (SR-DAHB) inverter suitable for high power applications. The topology is an isolated dual half-bridge circuit with an unfolding bridge. A combined phase-shift and frequency modulation technique is presented to generate AC power. In high-power applications where the switching devices operate at relatively high current and voltage, the switching loss becomes the major portion of the converter's total loss as the devices are turned off under hard switching. The primary merit of the proposed single-stage SR-DAHB inverter with the combined phase-shift and frequency modulation control is to significantly reduce the switching loss so that it is not a function of load current. A precise and comprehensive power loss model is developed to optimize the operation of the SR-DAHB inverter. The objective of the optimization is to minimize the inverter total loss while calculating the optimum combination of frequency and phase shift. A 1 kV, 50 kW prototype was built to demonstrate the performance of the SR-DAHB inverter with the combined phase-shift and frequency modulation control, and validate the theoretical analysis.