Analysis of wind driven grid connected induction generators under unbalanced grid conditions

A wind driven induction generator feeding power to the grid has been analyzed under the abnormal condition of unbalanced grid voltages. Using the symmetrical component and double revolving field theory, appropriate equivalent circuits and model equations have been derived for the generating mode with suitable realistic modifications. It is emphasized that the active and reactive power components and their directions for both positive and negative sequence systems need to be properly identified in order to obtain the cumulative response of the generator under different wind power conditions. In view of the fact that the reactive power is drawn from the grid while the active power is fed into the grid, the extent of variations in power fed to the grid and the reactive VAr due to unbalanced grid voltages for different wind power conditions need to be estimated to provide guidelines in the design and operation of the wind energy conversion system. Both experimental and theoretical results for a 3.7 kW laboratory model have also been presented, to validate the theoretical formulations, extendable to large units. Extensive data have been presented and discussed for a 55 kW unit installed in site