Fast Reactive Power Support Strategy for Grid-connected Converters under Asymmetric Faults Based on Time-scale Partitioning

In asymmetric fault conditions, grid-connected converters typically employ double second-order generalized integrators (DSOGI) to decompose grid voltage, extracting positive and negative sequence voltages for reactive current control, thus supporting grid voltage. However, the inherent dynamics of DSOGI introduce a 10-20 ms delay in voltage decomposition post-fault, hindering rapid and accurate grid voltage sensing and delaying reactive support. To mitigate this, a rapid reactive support strategy based on time-scale partitioning is proposed for asymmetric faults. Full-voltage information is utilized to create a composite voltage for immediate positive sequence reactive current control before sequence decomposition is complete, ensuring timely reactive support. This approach maintains grid stability by providing rapid response in the short term without sacrificing long-term control accuracy. DIgSILENT PowerFactory simulations confirm the strategy’s effectiveness in maintaining rapid support post-fault and long-term accuracy.