Operation Evaluation And Control Of Microgrid With Cyber-Physical Interdependency

With the increasing exhaustion of traditional fossil energy and growing concerns about environmental pollution,the distributed generation technology(including micro-turbine,wind turbine,photovoltaic,fuel cell,energy storage,etc.)has become the focus of sustainable energy development stratrgy in China.In order to fully exploit the benefits of distributed generation,improve the operation efficiency of power systems,and coordinate the interaction between distributed generation and traditional power grid,microgrids,as the most effective means to give full play to the advantages of distributed generation,is one of the key infrastructure in the construction of smart grids,and has been widely concerned in academic and industry.Through the cooperative control of various distributed generation,energy storage system,electric vehicle,and flexible load,microgrids can not only supply the continuous and reliable power to the important loads in microgrids,but also realize the power transmission and backup support to main grids.Microgrids involve multi-disciplines like computation science,communication technology and control theory to ensure their safe,reliable and economic operation.The electrical equipment measurement device and control unit in microgrids form data coupling and logical association through the power networks and information networks,which gives microgrids the characteristics of typical cyber-physical systems(CPSs).However,the deep coupling between physical and cyber systems has great impacts on the operation process of microgrids.Especially uncertain and unpredictable cyber contingencies may degrade the operation realiability and security of microgrids,which is mainly manifested in the following two aspects: 1)faults,congestions,and cyber disturbances in communication networks may degrade the power supply reliability of microgrids;2)cyber attacks against cyber systems will result in the control failure of microgrids,and even endanger the operation security.Based on the the operation and control process of microgrid CPSs,this paper analyzes the coupling mechanism of the physical and cyber systems of microgrids,and carries out a series of reseach from the aspects of operation evaluation and cooperative control,which provides the important theoretical and technical support for the operation analysis and cooperative control of microgrids with cyber-physical interdependency.The main contents of this paper are summarized as follows.(1)Operational risk evaluation of microgrids considering cyber contingencies: For the coupling characteristics of cyber and physical systems in microgrids,the operational risk evaluation method of microgrids caused by cyber contingencies is proposed.Firstly,based on the three-layer architecture of microgrid CPS,a modeling framework of microgrid CPS is established.Next,a routing method based on link state routing protocol is proposed,which can quickly determine the optimal data path and channel state between physical node and control node.In addition,an optimal control strategy to minimize load shedding is proposed to respond to the failure scenario of physical system.Finally,the operational risk indices are calculated by Monte Carlo simulation method,and the sensitivity of physical side to cyber contingencies is analyzed in power systems.(2)Distributed robust control of microgrids considering cyber disturbances: For the adverse impact of uncertain cyber disturbances on the dynamic performance of microgrids,a distributed robust H∞ control method considering cyber disturbances is proposed.Firstly,the consensus-based distributed control model of microgrids is improved by adding three types of cyber disturbances: data disturbance,peremeter perturbation,and communication latency.Secondly,by designing distributed robust H∞ controller,the relationship between comminucation coupling gains and robust H∞ performance of secondary control systems is quantified.Finally,the method of solving controller parameters solution based on linear matrix inequality is proposed to obtain the parameters that satisfy the requirement of H∞performance index as the foundation of strategy implementation,and the delay margin of microgrids is analyzed.(3)Modelling and distributed synchronous detection for cyber attack in microgrids:For the threat of cyber attack in microgrids,a distributed synchronous detection method is proposed.Firstly,based on the attack form of single point false data injection attack(FDIA),a two-stage model of FDIA is established,including deception attack and disruption attack,and the impact of different stages of FDIA on distributed reactive power and voltage control of microgrids is analyzed.Next,a distributed synchronous probing and feedback detection mechanism is established to avoid the complexity of centralized detection method.Last,a dynamic time warping distance based control strategy is designed to calculate the detection index in real-time,which adapts to the delay and packet loss scenarios in communication networks,and has different sensitivity to the attack singal.(4)Distributed resilient control of microgrids considering cyber attacks: For the problem of control failure or even system instability caused by cyber attacks in microgrid cooperative control,a cooperative control method based on distributed resilient consensus is proposed.Firstly,the local detection and synchronization defense framework for FDIA is established to avoid the increased risk of defense failure due to the introduction of extra traffic.Next,a distributed resilient consensus algorithm based on confidence factors is proposed,which determines the consensus communication coupling gains through weighted correction and searches for synchronization to eliminate attack information.Last,an adaptive updating strategy based on local detection and neighbor average is proposed to reduce the complexity of controller design.