Power Management for a Hybrid AC/DC Microgrid with Multiple Subgrids

Abstract

This paper proposes a new topology of a hybrid ac/dc microgrid, where there are multiple subgrids connected to the common bus by bidirectional ac/dc converters (BADCs) and bidirectional dc/dc converters (BDDCs) in the system. The rated ac frequencies in different ac subgrids and the rated dc voltages in different dc subgrids can be different for different applications. All the storages in the system are concentrated to form a storage subgrid for convenient management and high efficiency, which maintains the common bus voltage. To ensure the hybrid microgrid operate well, a proper power management method is necessary to control the power flow among multiple subgrids. This paper proposes a decentralized power management method for the hybrid microgrid to make the interacted subgrids operate in coordination and support each other. First, taking the characteristics of the common bus configuration into consideration, a Pdc – V2dc droop control strategy is proposed to maintain the common bus voltage and to realize power sharing among storages in the storage subgrid. Second, as the interaction among multiple subgrids is more complicated compared to the conventional hybrid, a coordinated power control strategy based on the common bus voltage, ac subgrid frequency and dc subgrid voltage is designed for the BADCs and BDDCs to realize the power interaction among different subgrids. Furthermore, the proposed strategy takes the capacities and load types of each subgrid into consideration, hence, it is still suitable when the capacities of subgrids are mismatched and it can ensure the power quality of the subgrids with high proportion of critical loads.

Existing System

Maximum Power Point Tracking Control.

Proposed System

A new topology of a hybrid ac/dc microgrid with multiple subgrids is proposed and a decentralized power management method is designed for this kind of hybrid microgrid in this paper. The proposed decentralized power management method can make the interacted subgrids operate in coordination and support each other. The proposed control strategy is simple in form, yet it can realize proper power management for multiple subgrids although the interaction among subgrids is very complicated. Through the coordinated control strategy, the subgrids can support each other and share the power fluctuation of the system in coordination. Furthermore, the proposed coordinated power control strategy considers the capacities and load types of subgrids, it is still suitable when the capacities of subgrids are mismatched and it can ensure the power quality of the subgrids with high proportion of critical loads.

Architecture

Topology of Hybrid AC-DC Converter