Evaluation of DC-to-DC converters topologies with quadratic conversion ratios for photovoltaic power systems

This paper presents a new class of pulsewidth modulation (PWM) DC-to-DC converters with quadratic conversion ratios for photovoltaic applications without a transformer. The aim of these structures is to obtain at the same time high conversion ratio and excellent efficiency for a wide source voltage range. The DC voltage conversion ratios of these converters have a quadratic dependence on duty cycle providing thus a large step-up and offering the possibility of higher switching frequency. This research focuses on the development of these new structures with only one single active switch and their theoretical analysis with relevant equations and operating principle. Moreover, a complete simulation and experimental results are presented to confirm their interest in photovoltaic applications. These results are used to compare on the one hand the conversion ratios versus duty cycle and on the other hand the efficiency versus the conversion ratios of each topology.