Impacts of DFIG-based wind farm integration on its tie line distance protection and countermeasures

Modern power grids, especially high-voltage grids, are increasingly integrated with wind farms. The correct action of distance protection for the wind farm tie line plays an important role in the safe and stable operation of the power system. However, based on the fault characteristics of wind farms based on the doubly fed induction generator, considering crowbar action and weak infeed properties, this paper reveals some serious defects of conventional distance protection. The result shows that, due to the influences of mixed data window and damped current component with near-rotor-speed frequency, the fault distance calculation result obtained by the fundamental-component-based distance protection is inaccurate. To tackle this problem, a transient-based distance protection countermeasure along with a faulted phase selection technique is proposed. Specifically, the transient phase voltage characteristic for different fault types is analyzed to select the faulted phase. Considering the effect of high-frequency components, pre-fault voltage compensation, and transducer characteristics, a distance calculation procedure including a low-pass filter, the reconstruction of voltage at the fault point, and an iterative fault distance calculation is proposed. The comprehensive performance of the proposed method is validated by the simulation case studies using the PSCAD/EMTDC software. (c) 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.