Application of Cycle Skipping Modulation in Buck-Boost Photovoltaic Microconverters

Cycle skipping modulation (CSM) was previously demonstrated for efficiency improvement in different converters intended for photovoltaic module-level applications. Currently, galvanically isolated buck-boost converters (IBBCs) have attracted increased attention in these applications due to the uptake of dc microgrids. This article revisits the topic of CSM and applies it to a quasi-Z-source-based IBBC. Two new CSM schemes are proposed for the given converter. Power losses in components are estimated for different CSM schemes to predict efficiency improvement that could be attained. A 300-W prototype was built to verify the efficiency estimation results. The efficiency trends are the same between the theoretical estimations and experimental measurements. Converter operation was studied for two bell-shaped solar irradiance daily profiles using a solar array simulator. The converter demonstrates efficiency improvement during morning and evening hours for a sunny day and during the whole day for overcast sky conditions.