Effects of digital differentiation on flicker measurements in wind turbines

Quantification of the flicker generated by wind turbines is a rather complex process requiring high-precision measurements. Based on the measurements of voltage and current time-series, the procedure uses an inductive circuit model to make the final measurements site-independent. This paper presents a study on the inaccuracy introduced by the numerical algorithms in calculating the derivative of the sampled signal when evaluating the flicker emission of wind turbines. It describes the alternatives found in the digital signal processing literature, and presents a comparative study of the results using analytically generated signals. The application of differentiation methods to the actual signal data of a wind turbine showed that depending on the implemented method, the differences in flicker emission quantification could be significant.