Penetration of wind power into power grids have had an accelerated growth in the number of wind farms and the installed capacity. However, the connection of wind power generation with high voltage systems lead to power quality problems due to the stochastic behavior of wind speed. Power quality problems are associated with the power fluctuations, voltage stability, frequency regulation and harmonic voltage and current distortion. Energy storage systems have been studied as an alternative to solve power quality problems. Related to harmonic distortion, the limits of individual and total voltage and current distortion for wind farms are defined in IEC Std. 61400-21: Measurement and assessment of power quality characteristics of grid connected wind turbines. To evaluated the effectiveness of energy storage systems, a power quality study of a large-scale wind farm with and without storage is presented. The study is focused on voltage drops and harmonic voltage and current distortion at the wind farm output. The study shows that the storage system could be implemented as a harmonic current distortion mitigation technique and improve the voltage level at the wind farm output when a short circuit occurs in the connection with the power grid.