A Post-Contingency Power Flow Control Strategy for AC/DC Hybrid Power Grid Considering the Dynamic Electrothermal Effects of Transmission Lines

Abstract

The blocking of large-capacity HVDC or the tripping of AC transmission lines by accident will cause power flow transfer sharply and increase the risk of cascading faults in AC/DC hybrid power grid. Therefore, it is needed to take reasonable safety control measures in time to interdict the spreading of the accident. In this paper, a post-contingency power flow control (PPFC) strategy for AC/DC hybrid power grid was proposed. This strategy brings the dynamic electrothermal effects of the conductor into the safety constraints to fully excavate the short-time overload endurance capability of transmission lines, and coordinates the active power adjustment of generators, power transmission adjustment of HVDC, and load shedding measures, to realize the dynamic optimal power flow control in multiple time sections. The proposed optimization control model takes minimum total cost as the objective function, and accounts for the influence of different weather conditions along the transmission lines and load fluctuations after the accident on the electrothermal safety of transmission lines, which can quickly provide the economical and reasonable power flow control scheme, to prevent the AC/DC hybrid power grid from unexpected cascading tripping effectively. Finally, the effectiveness and superiority of the proposed strategy were verified through case studies on the modified IEEE 10-machine 39-node power systems.