A proposal for verification tests for the flicker measurement procedure of grid-connected wind turbines

This paper presents a set of verification tests to assist the accurate implementation of flicker measurement in wind turbines. The flicker measurement procedure is defined in the IEC 61400-21 standard, which includes the estimation of a fictitious grid in order to measure voltage fluctuations generated exclusively by the wind turbine. The large margin in the digital implementation of the fictitious grid can result in large deviations in flicker measurements between different instrument manufacturers. This work shows the need of a verification test protocol to minimize the potential divergences. Furthermore, it suggests a set of five tests aimed at guaranteeing the accurate implementation of two specific components of the fictitious grid, namely the estimation of the electrical angle of the mains frequency and the derivative of the line current measured at the wind turbine terminals. The work has been proposed to the IEC Maintenance Team TC88/MT21 for it to be included in the third edition of the standard.