Provided is an arrangement for determining an operation parameter reference for controlling a generator side converter portion coupled to a generator, in particular of a wind turbine, the arrangement comprising: an arithmetic element configured to derive a fundamental current error by subtracting a, in particular unfiltered, generator output current from a sum of a fundamental current reference and at least one harmonic current reference; a fundamental current controller adapted to determine a fundamental operation parameter reference based on the fundamental current error; at least one other arithmetic element configured to derive at least one harmonic current error by subtracting a, in particular band pass filtered according to the harmonics, generator output current from the at least one harmonic current reference; at least one harmonic current controller configured to determine at least one harmonic operation parameter reference based on the harmonic current error.