Harmonics due to resonance in a wind power plant

Conventional PF correction equipment used in wind power plants, based on asynchronous generators, causes serious problems of resonance which affect the speed regulation stability, mainly at instants when the generated power is low. A practical case where a high level of harmonics was detected has been analyzed and a prediction model has been developed. The analysis was carried out by using a very simple simulation model where transformers were substituted by its short circuit reactance and the generator and the rest of loads by an R-L circuit according to active and reactive power. The resonance frequency obtained from this simple model was very close to the measured values in the practical case. A combination of a fast thyristor switched capacitor bank (TSC) and a detuned passive filter has been successfully used to avoid the resonance and solve the instability problem in the practical case presented here