A new approach for the prediction and identification of generated harmonics by induction generators in transient state

For the planning of future connection of wind generators to the public power system there is a need to specify the conditions when they can become sources of harmonic distortion. Induction generators have applications in wind power systems. Generators connected to the infinite bus are not sources for voltage harmonics. Autonomous generators are variable frequency variable voltage systems and their steady state voltage is distorted. In transient state the transient frequencies are superposed on the steady state waveform increasing the harmonic distortion. In this paper the transient model of the induction generator is extended and adapted for the prediction of the higher order transient harmonics in the generated voltage. Then, using experimental equipment a new numerical technique for their identification is implemented. A data acquisition system records the generated stator voltage during transients from various types of disturbances and the spectral analysis identifies the transient frequencies produced by the steady state fundamental and by its fractional and subfractional order harmonics. The identification of harmonics validates the predicted values by the analytical method