Current stress and switching loss evaluation of a unified expandable power converter used for grid-integration of renewable energy sources

Abstract

Due to the intermittent nature of the renewable energy systems (RESs), more specifically, solar panels and wind turbines, their sole use does not lead to a smooth and reliable power. To overcome this issue, the concurrent grid-integration of RESs to form a microgrid is reported. In the DC-bus microgrid, the produced power by RES is initially given to the shared DC-bus through an individual source-side converter and then transmitted to the utility via a common grid-side converter. By increasing the number of RESs, the number of required power converters, and therefore, the investment cost also increase. Using the cost-effective multi-input low-switch converters is a promising alternative to alleviate this significant need for individual converters. Recently, a nine-switch-based unified expandable power converter (UEPC) has been presented for concurrent integration of AC and DC sources with a tangible fewer switch count. This unified structure has been utilized in two configurations named AC-AC-AC and AC-AC-DC. In this paper, both configurations are evaluated and compared in terms of current stress and switching loss. Considering the current stress analysis, the best port for interfacing with the grid to lower the total current rating of power switching devices is also determined. The high-performance capability of both configurations is finally verified using MATLAB/Simulink.