Observer-based Cyber Attack Detection And Isolation In Smart Grids

With the integration and development of computer,network communication and automatic control,traditional power systems have gradually been developed into smart grids.Smart grid is one of the largest and most complex cyber physical systems(CPS).In particular,due to the open nature of the communication networks of smart grids,many potential cyber security attacks against the wide area measurement and supervisory control and data acquisition,which cause a serious significant impact on efficiency and control performance of smart grids.Thus,in order to enhance the security of smart grids,state observer-based schemes capable of detecting and isolating potential cyber attack have been paid a great attention.The main works are as follows:Firstly,aiming at the false-data injection attack against the smart grids generators,an observer-based algorithm is proposed to detect and isolate the cyber attack.Combining the smart grid system with graph theory,the system is divided into several different coupled areas via sparsity of the connection topology.By designing a modified observer,the residual is computed.And the adaptive residual threshold,used to detect and isolate the attack in the areas of the system,is also shown with considering the system model uncertainties.Then,an iterative algorithm detecting and isolating the cyber attack is proposed based on the calculated residual threshold.Secondly,taking into account the static stealth attack in smart grids load,we propose an attack detection and isolation algorithm.According to the attack characteristics,a state observer-based scheme is proposed to detect abnormal signals against static stealth attack.According to the sparsity of the system,the smart grid is divided into some different coupled areas.The abnormal region isolation is realized by satisfying the consistency test about the logic judgement matrix and the observed pattern,at the same time Prior load and Biased load can be isolated based on the relationship between the power of generator and the load.At last,for the existence of stealthy attacks in the SCADA of the smart grid system,the cyber attack detection and isolation algorithm based on the residual observer is proposed.The characteristics of the stealthy attack are described and analyzed via the model.Then the dynamic model with unknown attack input of smart grid is considered.By designing the modified observer and the adaptive residual threshold,the algorithm detecting and isolating the cyber attack is proposed.Finally,the simulations are provided to illustrate the effectiveness of the proposed algorithm.