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Isolated multiport converters for renewable energy conversion and microgrids
In recent years, there has been a growing interest in generating electricity from distributed renewable energy sources (RESs). In many applications, connecting multiple RESs of different types (e.g., wind and solar), voltages, and capacities to a power grid or load is required. An isolated multiport converter is preferable to perform efficient power management and grid integration for the multiple sources due to its advantages, which include fewer components, lower cost, higher power density, and higher efficiency. In this work, different isolated multiport converters were developed for integrating multiple RESs with the load or power grid. For a renewable energy generation system consisting of multiple sources, two new unidirectional isolated multiport DC-DC converters were proposed for simultaneous maximum power point tracking (MPPT) control of each source. For those renewable energy generation systems with energy storage devices, e.g., batteries, two bidirectional isolated three-port converters were designed for controlling the power flow among the three ports. However, the output of these converters is DC and cannot be directly connected to the AC utility grid. This dissertation introduces a new isolated, single-stage, three-port inverter for integrating RESs to the AC utility grid. The proposed converters have the advantages of low cost, a compact structure, high efficiency, and using the least number of switches, i.e., one switch for each port. Besides, the proposed converters not only are capable of MPPT for the RESs but also can control the charge/discharge of the battery to maintain the voltage of the DC-link/load at a constant value. Furthermore, the proposed converters achieve high efficiency owing to the merit of the soft-switching, e.g., zero-current switching (ZCS) and zero-voltage switching (ZVS).
Zeng, Jianwu, "Isolated multiport converters for renewable energy conversion and microgrids" (2015). ETD collection for University of Nebraska - Lincoln. AAI3718114.