Aggregation and amplification of wind-turbine harmonic emission in a wind park

This paper presents measurements of harmonic and interharmonic current (with 5 Hz frequency resolution) in the complex plane. The complex currents are spread around a center point. For interharmonics this center corresponds with the origin of the complex plane. For integer harmonics this center is off-set from the origin. A goodness-of-fit test reveals that phase angles of most interharmonics are uniformly distributed. A Monte-Carlo simulation based on the measurements has been performed to study the aggregation of the emission from individual turbines to the public grid. Low-order integer harmonics show less cancellation compared to high-order harmonics. Interharmonics aggregate close to the square-root rule for uniform phase angles.