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This study presents the qualitative and quantitative analyses, design procedure and experimental results on a soft switching cell applied to a high-voltage gain interleaved boost converter. An active snubber cell is proposed as a possible solution for the increase of efficiency in a hard switching topology, where switching losses are drastically minimised. The main advantages of the introduced circuit are the common source terminal to all switches; zero-voltage switching of the main switches; zero current switching of the auxiliary switches; low-voltage stress across the switches; balanced voltage across the output capacitors; the presence of a magnetic coupling cell, which allows the gain to be significantly increased; and the magnetic components that are designed for twice the switching frequency. A prototype rated at 500 W is implemented and evaluated, where relevant issues are discussed to validate the theoretical assumptions.

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The concept is presented of converters integrated in such a way as to obtain, in a single conversion stage, the maximum energy extraction from photovoltaic panels, battery charging and discharging dynamic control, and high voltage step-up to the inverter DC bus, also operating with soft-switching capability. Although this idea can be applied to most of the high voltage gain topologies, this presented report is based on structures derived from the half-bridge boost converter. Thus, a 500 W prototype, with input voltage of 24 V and output voltage of 200 V, has been developed with the purpose of obtaining experimental results and validating the proposed concept. High efficiency is achieved, above 92.5%, confirming the expected operation and functionalities necessary for the proposed application.Introduction: The growing use of alternative energy sources, such as photovoltaic panels, wind energy conversion systems and fuel cells, brings new challenges for the power electronic society and industry. In particular, small and distributed generation systems, isolated or grid-connected types, are the future trends for this technology. It is predictable that in the future most small consumers could act as an energy seller to the utility. Then the optimisation of the efficiency, volume, weight, and cost of power converters will be key features regarding the viability of these technologies.In the last few years, photovoltaic panels have been used only in isolated systems, in order to charge battery banks or in pumping systems, and the traditional power converters have been able to achieve maximum power point operation and battery charge control. Nowadays, many systems use an AC power supply and a low voltage inverter associated with a low frequency transformer to provide a sinusoidal voltage waveform with the appropriated voltage level. However, this solution presents high weight and appreciable losses owing to the high currents processed by the inverter and owing to the low frequency transformer. Thus, an additional stage is necessary to step the low level voltage up from the battery bank (12, 24, or 48 V) to the higher voltage level of the inverter DC link (200 or 400 V). As traditional step-up converters are not feasible for providing such high voltage gain, typical solutions use one high frequency isolated stage to achieve the high step-up voltage gain. Recently, non-isolated DC-DC converters with high voltage gain capability were successfully introduced [1, 2]. However, in systems where photovoltaic panels and battery banks are required, two DC-DC stages are still necessary, as shown in Fig. 1a.