Optimal reactive power allocation in a wind powered doubly-fed induction generator

The doubly-fed induction machine has been shown to be a popular choice for wind power generators, due to the desirable features of variable speed operation, reduced converter size and the ability to control the real and reactive output power. Typically the reactive power compensation is performed only from the rotor side converter while the supply side converter maintained at unity power factor. This work explains the concept of reactive power compensation in this generator and shows that it can be performed using both converters. In addition, it is shown that through proper choice of the distribution of reactive compensation between the two converters, an overall reduction in the total KVA rating of the converters can be achieved. A methodology for the design of the components and the control is presented. The theoretical predictions are supported by simulations using EMTP-RV.