Development of a Buck-Boost Convertor for Photovoltaic Systems using GaN Power Devices

A high-efficiency buck-boost converter is developed using a GaN semiconductor field-effect transistor (FET).Conventional boost-type distributed MPPT converters perform only the boost operation, requiring the load-side voltage to be higher than the photovoltaic (PV) voltage. Thus, when the load-side voltage is low, MPPT control cannot be performed, yielding a sub-optimal output. A buck-boost converter was therefore fabricated, with the efficiency reduction arising from the added circuit complexity remedied using a GaN FET. MPPT control could therefore be performed even in the step-down regime, in contrast with a conventional step-up-only converter. The use of a GaN FET to improve efficiency demonstrably therefore addresses the shortcomings of buck-boost converters.