Short-circuit analysis of a doubly fed induction generator wind turbine with direct current chopper?protection

Modern doubly fed induction generator (DFIG) wind turbines can ride through a symmetrical fault in the network by using a chopper protection on the direct current (DC) link without triggering a crowbar protection. A novel method to model the DC link system of such wind turbines as an equivalent resistance during symmetrical faults is presented in this paper. The method allows looking at the DFIG with chopper protection as to one with an equivalent crowbar protection and, hence, to apply to the former type of DFIG short-circuit calculation methods developed for a DFIG with crowbar protection. This may be a valid help in short-circuit calculations, for example, for protection settings. It also allows simulating for short-circuit studies a DFIG with chopper protection, often not available in a standard power system simulation software, by using an equivalent DFIG with crowbar protection, which is a standard model in power system simulation software. The results for the short-circuit current obtained through the proposed method are compared with simulations of a detailed model of a DFIG with chopper protection under different conditions, which showed good agreement. It is also shown that the DFIG with chopper protection delivers lower short-circuit current than a DFIG with standard crowbar protection, especially for low initial loading. Copyright (C) 2011 John Wiley & Sons, Ltd.