Adaptive dual-layer super-twisting sliding mode observers to reconstruct and mitigate disturbances and communication attacks in power networks

In this paper a novel distributed adaptive dual-layer super-twisting sliding mode observer-based scheme is designed to isolate, reconstruct and mitigate the effects of disturbances and a class of communication attacks affecting both generator nodes and load nodes in power networks. Voltage phase angles are measured at each node by means of Phasor Measurement Units (PMUs). Based on this information, an interconnection of adaptive dual-layer super-twisting sliding mode observers is designed both to estimate frequency deviation in each generator node, and to perform robust detection and reconstruction of both disturbances and a class of communication attacks. The proposed estimation scheme exhibits a distributed structure, since it requires only information received from neighbouring nodes and measurements taken locally in the power network. The novelty of the proposed scheme is its capability to reconstruct simultaneous disturbances affecting the generator nodes and load nodes, automatically adjusting the values of the gains of the observers. More precisely, the adaptive gains of the observer obey a recently proposed dual-layer adaptation law for the super-twisting sliding mode architecture. A disturbance mitigation strategy is also proposed at each generator node utilising the disturbance estimates. Numerical simulations are discussed to assess the proposed distributed scheme.