Wind Power Harmonic Emission versus Active-Power Production

Modern wind turbines are commonly equipped with power electronics. The application of either a partial scale frequency converter or a full scale power converter will result in harmonic emission which is distinct from conventional harmonic sources: even harmonics and interharmonics appear with similar magnitudes as odd harmonics. Harmonic and interharmonic measurements on a few individual wind turbines at the medium voltage side of the turbine transformers have been performed with standard Dranetz monitors. Measurements have been performed during a few weeks, with recording the aggregated harmonic and interharmonic subgroups over every 10-minute interval. The measurements involve a full range of active-power production through the individual wind turbines. This work will study the harmonic and interharmonic subgroups as a function of the active-power production for different wind turbines. Spectrograms (up to order 40) against the sorted active-power production present various trends of emission with the increasing power production. THDs and TIDs have been shown with the two characteristics: THDs without apparent trend, whereas TIDs with an increasing trend as a function of active-power. Despite various patterns of individual subgroups as a function of active-power, characterizations of a few subgroup types have been observed: characteristic harmonics vary little with the active power; whereas interharmonics with a strong relation with the active-power production.