IEC 61400-21:2008 covers the definition and specification of the quantities to be determined for characterizing the power quality of a grid connected wind turbine; measurement procedures for quantifying the characteristics; and procedures for assessing compliance with power quality requirements, including estimation of the power quality expected from the wind turbine type. The main changes with respect to the previous edition deal with interharmonics and current distortions (<9 kHz); response to voltage dips; active power ramp rate limitation and set-point control; reactive power capabilities and set-point control; grid protection and reconnection time after grid faults.
This publication is of high relevance for Smart Grid.