The present invention relates to a control system and an associated method for controlling an amount of reactive power delivered from a wind power plant to an associated power supply grid, the control system comprising a wind power plant controller and a number of wind turbine controllers each being in communication with said wind power plant controller, wherein the wind power plant controller is adapted to provide a grid voltage reference in response to a required total amount of reactive power to at least one wind turbine controller, said wind turbine controller comprising a voltage control loop comprising means for cancellation of a steady-state local voltage error.