Power electronics interfaces for hybrid DC and AC-linked microgrids

This paper discusses the power electronics interfaces and controls for a microgrid paradigm with both DC and AC links. The microgrid is an integrated energy delivery system that consists of interconnected distributed energy resources and controllable loads and can operate in parallel with or isolated from the main power grid. The proposed approach provides a general framework to aggregate a wide range of distributed energy resources at several levels with DC, AC and synchronous links. The collection of the aggregated units at each level represents those distributed units themselves to the upper level as a single self-controlled entity (DC or AC, generator or load). As an integrated energy system, the microgrid appears to the utility grid as indistinguishable from other currently legitimate customers. Advanced power electronics interfaces and their controls make it possible to achieve a desirable coordination among distributed resources, DC links, AC links, and the surrounding power system. In the paper, the variety of power electronics interfaces and control schemes are discussed and their performances are evaluated in a typical DC-linked microgrid and a representative AC-linked microgrid respectively.