Abstract: A rolling early warning method and system of dynamic security risk situation for large scale hybrid alternating current/direct current grids, which includes: constructing the original feature set of the fast total transfer capability (TTC) estimation model; generating the training sample set of the fast TTC estimation model based on the network topology and the forecast information of a period of time in the future; constructing the fast TTC estimation model based on stacking denoising autoencoders and extreme learning machine; generating the future operating conditions (OCs), and determine the type of preventive control actions needed to ensure the system security based on the fast TTC estimation model and the heuristic search algorithm; and conducting the layered and hierarchical early warning for OCs according to the type of operating state and the type of preventive control actions that is needed.