Low voltage ride-through requirements at the PCC versus wind generator terminals

Low voltage ride-through (LVRT) requirements, listed in modern grid codes, have proven to be a significant technical issue for many wind turbine manufacturers. The LVRT requirements are usually defined by the transmission system operators at the point of common coupling (PCC) of wind farm to the power network. However, depending on the transformers configuration, the voltage sag conditions experienced at the wind generator terminals can be substantially different from the conditions at the PCC. This paper compares the LVRT requirements at the PCC versus wind generator terminals for offshore DFIG-based wind farms subjected to various (a)symmetrical faults. Moreover, for wind farms located offshore or connected to the distribution systems, short circuit fault in the grid causes not only substantial drops in the voltage magnitudes but sudden changes in the voltage phase-angles. The effect of the latter phenomenon, referred to as phase-angle jump, on the transient response of DFIG-based wind turbine has been also investigated in this paper.