Post-Fault Active Power Control of DFIGs for Improving Multi-Swing Transient Stability-Part I: Theoretical Foundation

As the first part of this two-part paper, this paper proposes the theoretical foundation of DFIG's post-fault active power control for improving multi-swing transient stability (MSTS). Based on the static extended equal area criterion, the impact of DFIG's post-fault active power on the MSTS is analyzed, which indicates that the second-swing instability and the odd multi-swing instability should be focused on in the recovery process of DFIGs' post-fault active power. The slow and constant recovery speed has negative effects on the second-swing transient stability, while the fast and constant recovery speed rapidly decreases the odd MSTS. The simulations carried on the New England 10-machine 39-bus system with a DFIG based wind farm show that the revealed mechanism is correct. Keywords-Active power control, doubly-fed induction generator, extended equal area criterion, multi-swing