With the high penetration of renewable energy and the rapid development of AC/DC (Alternating Current/Direct Current) hybrid power grid, the power grid is confronted with challenges such as frequent voltage fluctuations and insufficient dynamic reactive power reserves. Full utilization of unified power flow controller (UPFC) in dynamic voltage regulation is of great significance for mitigating voltage excursions of the power grid. This paper proposes a double-time-scale dynamic reactive power optimization method for the AC/DC hybrid power grid with UPFC. A control framework for reactive power optimization of slow-time-scale and fast-time-scale is constructed incorporating the LCC-HVDC and UPFC. In this method, the slow-time-scale aims to improve the voltage profiles and reduce the system cost by setting the voltage regulation weight coefficients based on trajectory sensitivity to preserve reactive power regulation capability. The fast-time-scale adopts an adaptive feedback control mechanism. When slow-time-scale optimization is insufficient to keep the voltage within a safe range, it adjusts the real-time reactive power output of the UPFC, and damps rapid voltage swings accordingly. By implementing the additional fast-time-scale control method, the frequent variations of both the Photovoltaic (PV) and load are managed for the reactive power compensation. Case studies on a modified IEEE-30 bus system demonstrate that compared with the conventional control method, the proposed method reduces the maximum voltage deviation by 3.17% compared to the baseline, while ensuring the economic efficiency.
Yin et al. (Thu,) studied this question.