A harmonic predictor for a wind farm comprising at least two wind turbines, each having a generator with a converter for generating electrical energy. The harmonic predictor determines the harmonic component expected from the wind farm in order to limit the harmonic component to a harmonic limit. The harmonic predictor comprises a calculation module, an iteration module and a summing module. The calculation module calculates a complex mean value over at least one period of the harmonic component of one of the wind turbines and determines a first equivalent vector therefrom. The iteration module successively connects the calculation module to at least one other of the wind turbines to form at least one second equivalent vector. The summing module sums the equivalent vectors to form a total vector and compares the total vector with the harmonic limit.