Harmonic propagation in a doubly fed induction generator of a wind energy converter

This paper describes how harmonics up to some hundreds of Hz propagate from stator to rotor and vice versa in a doubly fed induction generator of a wind energy converter. Some of these harmonics are impressed by the grid, some are created by asymmetries of its voltages and currents; others originate in the wind turbine. At a test bench measurements have been made to investigate harmonics for one sub-synchronous and one super-synchronous operating point. The results show, how sources of harmonics in the generator can be identified and offer possibilities to compensate certain stator harmonics with the rotor side converter.