Decentralised non-linear I-V droop control to improve current sharing and voltage restoration in DCNG clusters

Abstract

This study proposes a new decentralised non-linear I-V droop control to achieve current sharing and voltage restoration for paralleled DC nanogrids (DCNGs) in a cluster. The performance of the conventional droop methods in current sharing among parallel converters degrades due to line impedances. The proposed method improves current sharing among the DCNGs with parallel-connected converters by considering the effect of line impedance, which is an important issue in practical applications. By the proposed method, desired current sharing from the light-load to heavy-load condition is achieved. Since only local information (the output voltage and output current of the DCNGs) is used, the proposed method is fully decentralised, and no communication infrastructure is required, which improves the reliability and stability of the overall system. Furthermore, Lyapunov stability theory is applied to investigate the stability of the proposed method. Additionally, the plug-andplay feature is achieved as an important desired functionality in the DCNGs as well as the proposed method provides scalability and modularity for the DCNGs in a cluster. In the end, theoretical analysis and experimental results validate the effectiveness of the proposed control framework for different scenarios.