Harmonic Analysis and Elimination of Transmission Scheme Based on DRU for Medium-Frequency Offshore Wind Farms

Offshore wind farm integration schemes based on diode rectifier unit (DRU) enhance economic efficiency and operational reliability, yet simultaneously introduce considerable harmonic distortion. This paper first establishes an accurate equivalent model of the DRU using a time-domain segmentation analytical method, validated through the time-domain simulations. Subsequently, by integrating the DRU model with the offshore wind farm network, a harmonic calculation method for the point of common coupling (PCC) is proposed. Analysis demonstrates that increasing the fundamental frequency and the number of DRU pulses effectively suppresses harmonic propagation. Furthermore, a structured six-step design methodology for AC filtering and reactive power compensation is introduced. Optimal AC filter configurations are developed for six distinct combinations of fundamental frequencies and DRU structures, providing theoretical foundations and practical guidance for ensuring power quality and enhancing the security of electrical system operations.