Circulating Currents in Coupled Multi-Terminal Hybrid AC-DC Grids

Abstract:
Coupling multi-terminal low voltage direct current (LVDC) and low voltage alternating current (LVAC) grids without isolation transformers is of high interest to reduce costs, material and losses. However, this introduces circulating currents between the LVAC grids. In this paper, the circulating currents are analyzed and reduction techniques are proposed. First, a simplified single phase system model is presented. Thereafter, the implementation of reduction methods derived from the model are introduced. Lastly, measurements from a test bench are presented where a significant reduction of circulating currents is achieved using the proposed methods.