Operation and coordination control scheme of an enhanced AC–DC hybrid microgrid under abnormal distribution network

Abstract

Considering that the AC–DC hybrid microgrid (HMG) is connected to the low‐voltage distribution network (DN) where voltage faults occur most commonly, the fault ride‐through (FRT) capability and power quality performance of the HMG under abnormal DN conditions have become a critical issue. In this paper, a decentralized coordination control scheme based on an improved topology is proposed for the grid‐interactive HMG to guarantee uninterrupted and high power‐quality operation during grid faults. The method of it includes: (1) a new HMG topology is presented by adding a series transformer (ST), which is inserted between the DN and HMG; (2) an improved coordination control strategy that considers the interaction between converters of the enhanced HMG. Based on the proposed method, the operation modes of the system are introduced, and the specific design process and small‐signal model analysis of the proposed control scheme are presented. Finally, the simulated and experimental results show that the proposed method can keep both AC and DC bus voltage stable and improve the fault ride‐through capability and power quality of the HMG under abnormal DN conditions.