Voltage source (VS) control based on inertia synchronization is a novel phase lock loop (PLL)-less autonomous grid-synchronization control strategy suitable for the permanent magnet synchronous generator (PMSG)-based wind turbine. It can autonomously sense grid frequency fluctuations by adopting the dynamics of DC-link capacitor, and it has the advantage of stable operation in an extremely weak grid. This paper further studies the low-voltage ride-through (LVRT) of the PMSG-based wind turbine under the VS control, and presents a wind turbine structure with the additional energy storage battery on the DC side, which not only improves its LVRT capability but also enables the wind turbine to participate in the grid primary frequency regulation. The transient characteristics of VS-controlled wind turbines after the occurrence of the short-circuit fault are analyzed, and a current suppression strategy via switching the virtual resistor in the control loop of the grid-side converter (GCS) is presented. Through coordination with the energy storage battery, the LVRT of the PMSG-based wind turbine is realized, which has the advantage of withstanding a long-time short-circuit fault. Finally, based on the PSCAD/EMTDC simulation platform, the feasibility of the control strategy and the correctness of the theoretical analysis are verified.

A fault current limiter (FCL) may be applied to assist the low-voltage ride-through (LVRT) of a doubly fed induction generator (DFIG). FCLs with fixed impedance, lack the flexibility to adjust their impedance to adapt to different LVRT scenarios. The direct switch-in and -out of the fixed-impedance FCL yields transient electromagnetic oscillations in the DFIG, which need to be addressed. In this paper, a variable-impedance FCL is implemented at the stator side of the DFIG to assist its LVRT, and a novel methodology is proposed to control the impedance of the FCL, with which the stator current oscillation is effectively constrained and the smooth switch-out of the FCL is realized to avoid continued active power consumption of the FCL and to restore the DFIG to its pre-fault working condition. Analysis of the LVRT transient is carried out, which lays the foundation for the control methodology to determine the impedance of the FCL based on calculation of the optimization goal. The feasibility and effectiveness of the control to the variable-impedance FCL are verified by the numerical analysis results, which compare the LVRT simulation results with the application of the fixed-impedance and the variable-impedance FCLs.