Compartmentalization Strategy for the Optimal Economic Operation of a Hybrid AC/DC Microgrid

Abstract

In this paper, a compartmentalization strategy is proposed for the economic operation of a hybrid AC/DC microgrid. The hybrid AC/DC microgrid will be compartmentalized into several independently controlled and coordinated AC and DC nanogrids. Accordingly, the optimal economic operation of the microgrid consists of two segments, including the optimal power sharing among local DERs in individual nanogrids and the optimal power sharing among interconnected nanogrids. For each AC/DC nanogrid, the optimal power sharing and frequency/voltage restoration are realized simultaneously without the need for any real-time communication. In the compartmentalized microgrid, each nanogrid will communicate with neighboring nanogrids through a sparse communication network to regulate power exchanges among nanogrids. In islanded mode, incremental costs of nanogrids are unified for realizing the optimal economic operation of the microgrid. In grid-connected mode, the external electricity price (i.e., purchase/sale electricity price set by the utility grid) is the desired incremental cost, which would be imposed on some pinned nanogrids and propagated among the remaining nanogrids. Then, the optimal power sharing of nanogrids within the grid-connected microgrid would be modeled as a pinning synchronization problem. The proposed compartmentalization strategy ensures that the optimal economic operation of the hybrid AC/DC microgrid is achieved under both island and grid-connected modes while the utilized communication structure is simplified and the dependency on communication networks is reduced. The performance of the proposed compartmentalization strategy is tested and verified through time-domain simulations in PSCAD/EMTDC for a hybrid AC/DC microgrid located at Illinois Institute of Technology (IIT).