Transient Stability Assessment for DFIG-MWPS Within the DC Voltage Control Timescale During Asymmetrical Grid Faults

During asymmetric grid faults, significant transient interactions occur between the grid and wind turbines (WTs) based on doubly fed induction generators (DFIGs), as well as among different DFIG-based WTs, increasing the risk of transient instability in DFIG-based multi-WT parallel systems (DFIG-MWPS). To quantitatively assess the transient stability (TS) of DFIG-MWPS during asymmetric grid faults, this letter proposes an assessment algorithm operating on the DC-link voltage (DCV) control timescale. The proposed method defines the TS boundary from the perspective of energy conversion. Compared to qualitative approaches, it quantitatively evaluates system stability based on the positive and negative sequence (PNS) active and reactive currents from each WT during grid faults, and determines the TS level of the DCV. Finally, hardware-in-the-loop experimental results validate the accuracy of the proposed assessment algorithm.