A Zeta-Based Multiport Converter with Soft-Switching and Hard-Switching Approaches for Microgrid Applications

This paper proposes a new Zeta-based multiport AC-link converter that serves as an interface for the interconnection of different sources and loads in multi-input/multi-output systems. The proposed converter offers improved reliability by replacing electrolytic capacitors with small film capacitors. Additionally, this converter achieves a high power density by utilizing compact high-frequency transformers instead of low-frequency transformers when isolation is needed. With only one small inductor and one small capacitor for power transfer between different sources and loads, the converter is capable of voltage step up and down over a wide range. An additional small capacitor in parallel with the inductor helps realize soft-switching in this converter. Moreover, the converter performs power conversion in a single stage, increasing the efficiency compared to multi-stage power converters. In comparison to the Ćuk-based AC-link converters, this topology uses a capacitor with a lower voltage rating. A small microgrid including a three-phase AC source, one photovoltaic source, and a three-phase AC load are considered in this paper to study and evaluate different power flow scenarios of the proposed multiport systems. The principles of the operation of the proposed topology are presented in this paper, and its performance is verified through simulations.