Zero-Power Transmission Control for DFIG-Based WT to Improve Synchronization Stability During Severe Grid Faults

Wind turbines (WTs) depend on the phase-locked loop (PLL) to maintain synchronization with power grid when integrated in weak grid. However, PLL may loss equilibrium point resulting in synchronous instability with improper active current reference, since voltage dips during severe grid faults diminish transfer capacity between WT and power grid. To cope with this issue, the zero-power transmission control for DFIG-based WT is proposed to improve synchronous stability. In this strategy, controlled rotor active current is injected to ensure that the DFIG- based WT operates at the stable equilibrium point during grid faults from the perspective of transmitted active power balance. This strategy is independent on the grid parameters and no addition controller parameter need to be designed, making the proposed method easy to use in practice. In the end, the experiments are performed to validate the theoretical analysis and proposed strategy.