The present invention relates to a power plant controller (23), controlling at least one electrical parameter of a wind power plant at a first point (201), the power plant controller receiving at least one measured electrical parameter at a point of measurement (204a, b), the point of measurement being different from the first point, and estimating a delta value of a difference of the at least one electrical parameter between the first point and the point of measurement, wherein estimating of the delta value is calculated based on an impedance between the point of measurement and the first point, and at least one reference value of the power plant controller, and the power plant controller controls the at least one electrical parameter on the basis of the at least one measured electrical parameter and the delta value.