Control strategy of clustered micro-grids for grid voltage unbalance compensation without communications

• Published in: IET generation, transmission & distribution Vol. 14; no. 20; pp. 4410 - 4415
• Main Authors: Liu, Baoquan, Zhao, Xuguang, Liu, Yan, Zhu, Yixin, Chen, Jingwen
• Format: Journal Article
• Language: English
• Published: The Institution of Engineering and Technology 16.10.2020
• Subjects: clustered microgrids; control strategy; distributed power generation; grid synchronisation; grid voltage; grid‐connected converters; grid‐connecting; invertors; microgrid cluster model; microgrid inverter; mode switching; NS control loops; power distribution control; power generation control; power grid; power grids; Research Article; voltage control; power distribution control; control strategy; microgrid inverter; grid voltage; grid-connected converters; power generation control; distributed power generation; power grid; mode switching; invertors; microgrid cluster model; clustered microgrids; grid-connecting; NS control loops; power grids; grid synchronisation; voltage control
• ISSN: 1751-8687; 1751-8695
• DOI: 10.1049/iet-gtd.2020.0421

Grid-connected converters are expected to provide ancillary service utilising their spare capacities during operation. This study proposes a novel control strategy for clustered micro-grids to compensate voltage-unbalance of the power grid at the point of common coupling. Every micro-grid are interfaced to the power grid through a micro-grid inverter (MGI). All MGIs are designed independently with positive-sequence (PS) and negative-sequence (NS) control loops. Every micro-grid autonomously performs grid synchronisation and mode switching. After grid-connecting, a dynamic capacity allocation method is proposed for the MGIs to optimise its PS and NS capacity according to the grid voltage unbalance factor. Furthermore, a V–I droop control of the NS control loops is developed, with which each MGI can regulate its NS current according to the NS voltage in a droop manner. With the proposed method, all micro-grids participate in grid voltage unbalance compensation according to their own potential capacities without communications. Finally, a micro-grid cluster model with three micro-grids is built on Matlab/Simulink to validate the proposed control strategy.