Analysis, simulation and testing of the ZVRT capability of a wind turbine with a doubly fed induction generator

Zero-voltage ride through (ZVRT) is the extreme case of a low-voltage ride through (LVRT), which represents the optimal grid-connection capability of a wind turbine (WT). Enforcing ZVRT will improve the dynamic performance of a WT under the extreme conditions, and therefore significantly enhance the resiliency of a renewable-rich power grid. Compared with LVRT, there are few research on ZVRT with no field validation been conducted. The feasibility of the ZVRT requirement, especially the 400-ms-level fault-time condition, is not clear yet. The first system-level study including the control strategy, transient analysis, hardware enhancement strategy, WT modelling and field test on the ZVRT capability of a Type-3 WT is presented in this study. Particularly, to meet the challenging technical requirements, the authors proposed a hardware enhancement strategy, which accommodates with the widely-used LVRT control approach. The holistic strategy is tested under the extreme grid-connection condition by both simulation and a costly field test. The field test in the 400-ms-level fault-time condition based on an operating WT in a weak power system directly verifies the feasibility and effectiveness of ZVRT for a Type-3 WT. Furthermore, the critical time window and the key parameter ranges during ZVRT, which significantly affect ZVRT performance, are obtained.