The electrical utilities have specified in their recent requirements that wind turbines have to be capable to ride through severe symmetrical and unsymmetrical voltage dips without disconnection. Moreover, the generators are required to produce active and reactive power in order to improve the stability of the grid. For symmetric three-phase dips, the measurement of reactive and active power, and current is quite straightforward, and several methods can be used. On the contrary, with unsymmetrical dips, very different results are obtained using alternative methods. A recommendation to use active and reactive power calculation method based on the positive sequence of the fundamental component is given. Copyright © 2007 John Wiley & Sons, Ltd.