Loss of Synchronism of Wind Turbine Converters during Low Voltage Grid Faults

In the recent grid codes, wind power plants are required to stay connected and inject reactive and active currents during grid short-circuit faults, even when the grid voltage drops down to zero. However, the physical fact, Loss of Synchronism (LOS) of wind turbines during these very low voltage faults has been underestimated in the grid codes; and the LOS has recently been explored only in few studies.

In this paper the LOS phenomenon is studied, especially focusing on the case of a string of wind turbines, rather than an aggregated one. It is shown that the LOS affects the wind power plant as whole. Additionally, existing methods to solve the LOS problem are briefly reviewed, and a closed loop frequency based solution is implemented within PowerFactory simulations of a detailed generic wind power plant model.