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Abstract. This paper proposes a decentralized stand-alone photovoltaic (PV) system, which presents a set of advantages when compared to conventional stand-alone PV system. In the proposed system, the generated energy by the PV arrays is processed by multi-string MPPT step-up converters, which assure a maximum utilization of this energy. The storage system is designed in a decentralized configuration, enabling to achieve a reduction of maintenance cost of back-up system. Moreover, the output stage is composed by a multilevel dc-ac inverter, which enables higher efficiency, low distortion ac waveforms, low leakage currents and the use of low voltage rating semiconductor devices.

Abstract. This paper exploits the advantages of using a cascaded connection of dc-dc step-up stages for a series string of photovoltaic (PV) panels in a single-phase residential/commercial grid connected installation. It is demonstrated that when multistring PV systems are adopted in order to minimize shadowing problems, it is required to employ some approach to reduce the switching losses (turn-on losses of MOSFETs and mainly diode reverse-recovery losses) of the dc-dc step-up stages. As a multistring PV system is normally comprised by several dc-dc stepup stages, integrated soft-switching topologies are attractive due to their compactness, reliability and low cost. Thus, this work proposes to use an integrated zero-voltage transition (ZVT) cell, which assists all dc-dc step-up stages and employs a very compact circuit, enabling to minimize the switching losses, improving the system efficiency. The proposed cell makes use of a magnetically-coupled auxiliary voltage source implemented by adding a secondary winding on the input inductors. In order to validate the proposed topology, experimental results are presented.