Research on Wideband Harmonic Resonance of Collector System in Offshore Wind Farm

Submarine cables are used to collect electrical energy in offshore wind farms, of which the grounding capacitance cannot be ignored. The impedance of wind turbine generators (WTGs) interacts with the impedance of the network, leading to a risk of wideband harmonic resonance (WHR). In order to study the characteristics of the internal WHR in the collector system, firstly, the impedance models of a typical WTG and cable line are established, and the correctness of the established mathematical models are verified. Then, the wind farm system can be divided into the equivalent wind turbine subsystem (EWTS) and remaining equivalent wind farm subsystem (REWFS) based on the impedance stability theory. And the effects of the length of cable line, the number of trunk lines in the collector system, the number of connected WTGs and the equivalent grid-side impedance on the WHR are analyzed. Finally, the validity of the theoretical analysis is verified by MATLAB-based simulation results.