Unidirectional isolated high‐frequency link DC/AC converter for grid integration of DC sources

Abstract

Most of the converters used for the grid integration of DC resources are multi-stage DC/AC converters with a huge intermediate DC-link capacitor. This bulky DC-link capacitor increases the converter volume and cost, reduces its lifetime and reliability and, causes converters fault ride-through problems. For this purpose, DC/AC converters without any intermediate energy storage components are proposed in the literature named high-frequency AC (HFAC) link converters. However, due to a large number of active switches, modulation and commutation methods of these converters are overly complex compared with their conventional multi-stage versions. In this study, a new isolated unidirectional converter without any intermediate energy storage components, and with a reduced number of active switches are proposed for the grid integration of DC sources. The proposed HFAC converter structure is simple but more efficient and reliable than its conventional isolated multi-stage and HFAC versions. The converter modulation and commutation methods which are more simple than those of its conventional HFAC version, and its voltage and current gains are also presented. The performance of the proposed converter is verified through simulation in the islanded and grid-connected modes of operation. A simple experimental setup is also provided to validate the simulated converter.