Day‐ahead voltage scheduling method based on a two‐stage robust optimisation for VSC‐HVDC connected wind farms

Abstract

Considering the capacitor banks and on-load tap changer (OLTC) applied in the voltage-source-converter-based high-voltage direct-current (VSC-HVDC) systems with large-scale wind farm integration, this study presents a day-ahead voltage scheduling method to avoid frequent adjustment of the slow discrete devices. Using this method, the AC side voltage of the wind farm side VSC (WFVSC), capacitor banks and OLTC can be scheduled optimally. The scheduling ensures a discrete but large change, while real-time automatic voltage control (AVC) in wind farms offers a continuous and a fine response to the volatility of wind power. This ordination is realised by a two-stage robust optimisation utilising wind power forecasting. Furthermore, a reasonable simplification method is proposed to address non-linear constraints and make the problem solvable. Based on Monte Carlo simulation, case studies are conducted for both simple and real systems to verify the validity and superiority of the method. The results show that the scheduling enhances the AVC effect under the randomness of wind power output and enables collaboration among diverse devices in the vicinity. The system operation outperforms other methods in terms of the voltage profile and dynamic reactive power reserves.