Transfer function-based analysis of harmonic and interharmonic current summation in type-Ⅲ wind power plants using DFIG sequence impedance modeling

摘要

This paper presents a new Transfer Function (TF)-based approach to evaluate the summation of complex harmonic and interharmonic current primary emissions in a wind power plant. A comprehensive impedance modeling of a doubly-fed induction generator including the Phase Locked Loop (PLL), induction generator, and current control loops of the converters is included in the TFs. A small-signal impedance modeling consisting of positive/negative-sequence modeling up to 50th harmonic order is adopted. The updated TF models are then used to calculate the contribution of each wind turbine to the total harmonic and interharmonic current distortions at the point of interconnection. Three phase angle distribution patterns are also presented to assess the stochastic behavior of the harmonic and interharmonic currents using the concept of "aggregation factor". The variations of the aggregation factor with the PLL bandwidth are also investigated. Besides, the obtained primary emission TFs are used to adjust alpha-exponent in IEC 61000-3-6 summation rule. Analytical results are presented and compared to the simulation results where it is concluded that the proposed approach is more accurate than the previous approaches of TF modeling and related phase angle distribution patterns.