Soft-switched Boost-cuk-type High Step-up Converter for Grid-tied with Half-bridge Inverter

In this study, a novel two-stage grid-tied high step-up inverter is proposed. The first stage (DC-DC) is a combination of boost and cuk converters as well as a simple DC-link voltage balancing circuit. The balancing circuit is connected in series with the output of the cuk converter to compensate for the output voltage difference between boost and cuk converters. The second stage (DC-AC) comprises a conventional half-bridge inverter. The ground leakage current is eliminated in the proposed topology by the simultaneous grounding of the PV module and the grid. A lossless passive snubber with the minimum elements is also proposed and analyzed to provide the soft-switching conditions. In this snubber circuit, the snubber capacitance discharges to the output DC-link to decrease the converter circulation losses. The main attributes of the proposed DC-DC converter with lossless passive snubber are the simple structure of the DC-DC converter and snubber circuit, simple control scheme, and high efficiency. Various operation modes of the proposed topology are theoretically analyzed and investigated. The experimental results substantiate the effectiveness and performance of the proposed boost-cuk-based high step-up inverter with the lossless snubber.