Distributed Cooperative Control of Offshore Wind Farms Integrated via MTDC System for Fast Frequency Support

This article proposes a distributed cooperative control (DCC) scheme of offshore wind farms integrated via the multiterminal direct current system for fast frequency support. The DCC scheme employs the consensus algorithm to share the frequency support burden among offshore wind turbines (WTs) suitably. The proposed DCC scheme can exploit the kinetic energy of all WTs adequately, while ensuring the security by employing the consensus state index and changing droop control coefficients adaptively. After the frequency support, the asymptotic recovery scheme is proposed at the leader WT for smooth rotor speed restorage, and other WTs will follow the leader to recover and reduce the second frequency drop. Besides, to realize the fast frequency support, the communication-free estimator is employed to estimate the onshore dc voltage using offshore local measured signals. Case studies are carried out on MATLAB and OPAL-RT real-time simulation platforms, respectively. Different control schemes are compared to elaborate the performance of the proposed DCC scheme considering the parameter uncertainty and noise disturbance.