Transient Characteristics Analysis of DFIG during Power Grid Fault and Crowbar Resistance Adaptive Tuning

The purpose of this paper is to improve low voltage ride through (LVRT) capability of doubly fed induction generator (DFIG).First, this paper gives expressions of the stator flux and rotor current during the grid fault occurrence and clearing by solving the mathematical model of DFIG. The results of simulation conducted on a 1.5MW DFIG in the PSCAD/EMTDC verified the correctness of the derivation. Through qualitative analysis of stator flux expression, different fault durations will lead to the difference of transient during fault clearing and ignoring the process of fault clearing will lead to excessive crowbar resistance. Therefore, this paper optimizes the Crowbar resistance by considering both the process of grid fault and fault clearing, and then presents a Crowbar resistance adaptive setting principle based on Crowbar structure with parallel resistor. Simulation confirms this method can improve LVRT of wind farms. Keywords-doubly fed induction generator (DFIG); transient characteristics; low voltage ride through (LVRT); Crowbar circuit; adaptive tuning