Observer-based Cyber Attack Detection And Isolation In Smart Grids

With the development of marketization process,it is difficult for traditional power systems to support so many development requirements.Smart grids with powerful resource configuration capabilities and stable operation level emerge as the times require.In particular,due to the system structure is complex and scale of the communication networks of smart grid is increasing,many potential cyber security attacks against the system,which cause a serious significant impact on efficiency and control performance of smart grids.Thus,in order to enhance the security of smart grids,based on cyber attack strategy and characterization analysis,state observer-based schemes capable of detecting and isolating potential cyber attack have been paid a great attention.The main research works of this paper are as follows:Firstly,for the existence of cyber attack in the smart grid system,the possible cyber attacks in the smart grid are obtained by analyzing the influence of cyber attack on the operation of smart grid system.Considering the attack is injected in system,the system output measurement does not change,which means that the system detection mechanism cannot identify the existence of the cyber attack.Therefore,the covertness and destructiveness of cyber attacks are analyzed,which make adequate preparation and foundation for attack detection and isolation.Secondly,aiming at the dynamic load altering attack(D-LAA)against the smart grids load,an observer-based algorithm is proposed to detect the cyber attack.By analyzing the strategy and characteristics of the D-LAA,the dynamic model with DLAA of smart grid is considered.By designing a state observer,the residual is computed.And the residual threshold,used to detect the attack in the system,is also shown with considering the system noise.Then,an algorithm detecting the D-LAA is proposed based on the calculated residual threshold.At last,taking into account the zero dynamics attack in the communication network of smart grid system,a robust PI observer-based algorithm is proposed to detect and isolate zero dynamics attack in attacked actuator.According to the attack characteristics,it is shown that zero dynamics attack is covert,which can intelligently avoid to be detected.Through analyzing the monitoring limitations from system theoretic perspective,a robust PI observer is designed to reconstruct attack signal,then a novel residual signal is constructed to detect and isolate zero dynamics attack.