Type-III Wind Power Plant Harmonic Emissions: Field Measurements and Aggregation Guidelines for Adequate Representation of Harmonics

Large wind power plants (WPPs) based on variable speed turbines produce harmonics and interharmonics of voltage and current. This paper presents some generic guidelines about resulting harmonics and interharmonics at the high voltage point of interconnection (POI) of a type-III WPP. These guidelines are supported by both field measurements and time-domain electromagnetic transient (EMT) simulations. Specific focus is placed on how these harmonics and interharmonics can be represented in EMT simulation using detailed and aggregated models of a WPP. First, a theoretical explanation of the origin of all frequencies produced by a type-III wind generator (WG) is presented. The results of field measurements from a large WPP are then reported and analyzed confirming the theory. Subsequently, the field measurements are compared to simulation results of a detailed EMT model of the entire WPP and differences are explained. Finally, aggregated models of the same WPP are established and the accuracy of these aggregated models is discussed in light of the specific need of time-domain EMT studies that require adequate representation of harmonics.