Coordinating voltage controllers within a wind park being connected to a utility grid

It is described a method for coordinating voltage controllers within a wind park (100) being connected to a utility grid (190) and comprising (i) a plurality of wind turbines (180) and (ii) different types of controllers (110, 120, 130, 140) which are assigned to different voltage levels within the wind park (100). The described method comprises (a) estimating a strength of the utility grid (190) by means of a first controller (110), (b) forwarding the estimated strength of the utility grid (190) from the first controller (110) to a second controller (120), and (c) adjusting a control gain of the second controller (120) based on the forwarded estimated strength of the utility grid (190). It is further described a controller system and a computer program both being configured for controlling and/or for carrying out the described voltage controller coordinating method.