A General Current Limiting Strategy of Grid-Forming Converters Based on Adaptive Virtual Impedance Regulated by Fuzzy PI Control

Grid-forming (GFM) converters are considered as a key solution for new power system with high penetration of renewable energy resources, owing to its voltage and frequency support ability. However, most of existing current limiting strategies of GFM converters are effective only in several predefined scenarios. Therefore, a general current limiting strategy that functions in both islanded and grid-connected modes for various fault conditions is highly expected. In this paper, a current limiting strategy based on adaptive virtual impedance regulated by fuzzy PI control is proposed. It shows excellent current limiting ability for various fault conditions in different operation modes with the same predesigned parameters. Moreover, unlike previous virtual-impedance-based current limiting methods that cannot precisely limit the current at a predefined value, the proposed method accurately restrains the output current at the desired limit via fuzzy PI control. The effectiveness of the proposed current limiting strategy in various fault scenarios is verified by simulation in MATLAB/Simulink.