Measurement of the flicker characteristics of grid connected wind turbines: Instantaneous frequency versus instantaneous phase estimation methods

Power injection of grid-connected wind turbines can produce voltage fluctuations and hence affect power quality. The assessment of the injected flicker is computed through the calculation of a fictitious voltage in a simple grid-model. For that purpose, the instantaneous angle of the fundamental component of the measured voltage has to be estimated. This paper presents the analysis of two different approaches for the estimation of the instantaneous frequency and phase of the fundamental frequency of a voltage signal. Based on those two approaches, four estimation methods are assessed. The accuracy of each method is evaluated using analytically generated signal. Then, the methods are compared when applied to registered voltage signals, collected in a Spanish wind farm.