Robust damping control for VSC-MTDC system in offshore applications considering disturbance uncertainty

Abstract

Multi-terminal direct current transmission based on voltage source converter (VSC-MTDC) has become an ideal solution for long distance offshore wind farm access systems. However, the integration of VSC-MTDC with offshore wind farms is vulnerable to various disturbances, which can lead to instability. To address this issue, this paper presents a robust damping control for VSC-MTDC in offshore applications that accounts for disturbance uncertainty. First, a small-signal VSC-MTDC model is developed considering the coupling characteristics of the cable, and the DC cable model is suitable for both unipolar and bipolar structures. Secondly, the key parameters affecting the oscillation mode are analyzed. On this basis, the paper proposes a robust damping strategy that adapts to the changing operating conditions of the system without impairing steady-state performance, while enhancing transient performance. Finally, the paper builds a VSC-MTDC with offshore wind farms on MATLAB/Simulink to validate the correctness and effectiveness of the proposed scheme. The simulation results demonstrate that the proposed control strategy exhibits better robustness and suppression ability under multiple types of disturbances compared to traditional additional damping control.