Evaluation Of Security And Stability Risk Of Ac/Dc Grid Under Extreme Contingencies

As substantial power is imported into Shanghai Grid through four HYDC systems, the operation characteristics of multi-infeed receiving-end system have emerged in Shanghai Grid. The intensive interactions between HVDC system and AC grid may aggravate the risk of cascading as well as the capability of the grid to withstand significant disturbances. In this paper, simulation of HYDC system response upon fault occurrence in AC system is performed for Shanghai Grid with the maximum power import through four HVDC transmission systems. The risk of AC grid's instability due to commutation failures and bloc kings of HVDC systems is investigated. Quantitative assessment of system voltage stability margin is conducted for the grid under simultaneous blockings of multiple HVDC systems. The overall security and stability risk attributed to the interactive influence between AC and DC grid is evaluated for Shanghai Grid under extreme contingencies.