Analytical characterization of DFIG response to asymmetrical voltage dips for efficient design

Abstract

The fault current characteristics of Doubly Fed Induction Generator (DFIG) based wind turbine generator (WTGs) differ from those of traditional generators. Although asymmetrical faults are far more frequent, the studies on transient current characteristics of DFIG-based WTGs are mainly focused on symmetrical faults and consider the variations in voltage magnitude only. This paper presents highly accurate and concise analytical expressions for the stator and rotor currents of DFIG-based WTGs under crowbar protection considering the variations in magnitude and phase angle of both the positive- and negative-sequence voltages during asymmetrical faults. The proposed expressions are validated using a detailed simulation model of a 1.5 MW DFIG-based WTG. The expressions can be directly integrated into protection tools for the evaluation of dynamic performance of relays and design of fault ride through (FRT) solutions.