Coordinated Recovery Strategy of AC and UHVDC Interconnected System Considering the Power Grid Strength

Large transient power impact of UHVDC commutation failure has great influence on the security and stability of the power grid, becoming one of the most important threats to the safe operation of large scale AC and DC interconnected system, especially when the HVDC system is connected to the weak AC power grid, commutation failure can even cause system instability, leading to new energy tripping, system crash and other serious risks. A coordinated recovery strategy of AC and UHVDC interconnected system is proposed in this paper. Firstly, the coupling characteristics of AC and HVDC system is analyzed, and then the impact of different disturbance on the power system recovery characteristics is taking into consideration. Secondly, an AC and HVDC system coordinated recovery strategy is proposed considering the AC power grid strength, by modifying the parameters of CFPREV and VDCOL to control the recovery speed of HVDC system after commutation failure, which can realize fast recovery of the interconnected system and reduce the impact of HVDC commutation failure on the whole system. At last, the effectiveness of this strategy is verified by the simulation of an actual large scale AC and UHVDC interconnected power grid.