The invention relates to a method for controlling a wind turbine system, more particular for a method for determining shadow flicker at a location and identifying a wind turbine in a wind park with a plurality of wind turbines causing the shadow flicker. A remote detector located at or near the location is determining the presence of shadow flicker and generating flicker data representative of the shadow flicker. A target wind turbine potentially causing a shadow at the location is identified based on the turbine position and the position of the sun. Operational data from the target wind turbine is obtained and it is verified whether the target wind turbine generates the shadow flicker by comparing the flicker data and the operational data.