Abstract：Transient characteristics analysis is the foundation and the key for low voltage ride through (LVRT) of doubly fed induction generator (DFIG). Conventional studies usually focus on the transient processes during gird faults and ignore the transient process of fault clearing. Thus, the transient process analyses are incomplete. It will result in the inaccurate calculation of the maximum rotor short-circuit current, further leading to Crowbar resistance selection unreasonable. In this paper, the expressions of the stator flux during the grid fault and fault clearing were proposed based on the mathematical model of DFIG. Then the expression of the rotor current was derived from the view point of the rotor equivalent circuit. Accordingly, the Crowbar resistance was amended. The results of simulations on a 1.5MW DFIG in PSCAD/EMTDC verify the correctness of the derivation. What’s more, different fault durations will lead to the different transient processes during fault clearing, where ignoring the process of fault clearing will lead to the excessive crowbar resistance. The resistance optimization of Crowbar needs to consider the processes of grid fault and fault clearing.
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2017, Vol. 32 
