Stability Analysis of Mid-Frequency Oscillation in Flexible Direct Transmission System of Offshore Wind Farm

Flexible DC transmission technology provides an efficient, flexible, stable and environmentally friendly power transmission method for offshore wind farm (OWF). However, offshore wind power is highly susceptible to disturbances and instability through flexible DC transmission systems, resulting in mid-frequency oscillations that cause wind turbine shutdowns and converter lockdowns, severely restricting the efficient and reliable consumption of wind power. Regarding the issues mentioned above, this paper presents a strategy for analyzing the stability of mid-frequency oscillations in OWF through flexible direct transmission system based on eigenvalue analysis. Firstly, using the modular state space method to establish a small signal model for the flexible direct transmission system of OWF; Then, the critical influencing factors of mid-frequency oscillations in OWF via flexible direct transmission system are revealed by calculating the modal participation factor of mid-frequency oscillations; Finally, using the characteristic root trajectory as the research method, the influence of the control link, AC transmission line parameters, and link delay link of the flexible straight system on the stability of mid-frequency oscillation was analyzed, and the effectiveness of the theoretical analysis was verified through timedomain simulation.