Secure frequency control of multi-area hybrid power systems with wind power is a research problem involving active defense, vulnerability, and resilience. Considering the scenario that Denial-of-Service (DoS) attack intrude into the control channels of thermal power and wind farm, the hybrid power system is modeled by a switched system with four subsystems. Then, the exponential stability of hybrid power system is studied under arbitrary DoS attack. An active defense scheme is proposed to design switched control gains by Lie algebra method achieved by a distributed consensus method. Furthermore, following the resulted exponential stability, the load disturbance attenuant performance of frequency control is studied by the proposed concepts of vulnerability point and resilience point. Under a class of event-DoS attack model, the estimation method of vulnerability point and resilience point is given. Finally, simulations of a three-area hybrid power system and NE39bus test system are carried out to verify our theories.

Due to the high R/X ratio and mismatched feeder impedance of low-voltage microgrids (LVMGs), conventional droop method is no longer able to decouple the active and reactive power of distributed generators (DGs) and the power sharing accuracy is degraded. In this paper, a virtual complex impedance based P — V droop method is proposed to decouple the powers and improve the power sharing accuracy among DGs. With the virtual impedance method, the equivalent impedance between virtual power source (VPS) and point of common coupling (PCC) is shaped to be purely resistive. Then, a P — V strategy is adopted to alleviate the effect of mismatched line impedance, where the virtual powers rather than the ordinary P/Q are used in the droop equation. In case the output voltage violates the operation code, a restoration mechanism is proposed to reset V to zero. Compared with existing virtual impedance and Q-V droop methods, the proposed method combines the advantages of both. Besides, a modified P — V strategy is also presented to accelerate the restoration process and improve the active power sharing accuracy at the same time. Simulation results validate the effectiveness of the proposed methods.

By means of advanced information and communication technology, cyber‐physical power systems can attain real‐time monitor and control but have to suffer the damage caused by a cyber attack. In this study, the authors' define attack efficiency to evaluate attack paths that attacker may adopt to intrude systems, to find the most efficient attack paths (i.e. the most vulnerable paths). Based on the actual power grid and security stability control system, the coupling model of cyber‐physical power systems is established to analyse the propagation of cascading failure within and across the physical power grid and communication network. In the attack model, the attack cost matrix is built to describe the cost between directly connected nodes in a communication network. Furthermore, considering the probability that control commands are successfully transmitted from router nodes to generator/substation nodes, the total attack cost from the communication network to the physical power grid is figured out. To search for the most vulnerable attack paths in systems, the attack efficiency is proposed to quantify the relation between attack cost and attack gain, wherein the attack gain is the damage on systems caused by the cyber attack.

In cyber‐physical power systems, tiny failure occurring in the communication network could propagate to affect the operation of the physical power grid through inter‐links and even cause catastrophic blackouts. The authors propose a partial random coupling systems model to study the vulnerability of nodes and connectivity of systems in a cascading failure. In terms of traffic loads generated in systems, they employ load spill index to analyse dynamic states of nodes in cascading failure. In cascading failure, considering the effect from a communication network, vulnerability matrices are established to study the vulnerability of nodes in the physical power grid. Furthermore, an efficiency index is defined to analyse connectivity of systems. In the numerical simulation, they verify the accuracy of the proposed evaluation approach and test its scalability and universality in different power systems.

In this paper, we study the dynamic of cascading failure iterating between physical power grid and communication network, and further propose the attack strategy to locate the critical nodes which can seriously damage the cyber-physical power systems. First, the coupling connection between physical power grid and communication network is modeled, along with the power flow of physical power grid and the data flow of communication network. Then, the zone-based coupling model is proposed to detail the failure cascading in systems and its impact on coupled networks. Third, based on electrical and structural characteristic, the criticality of nodes is defined to devise attack strategy to locate the vulnerability of systems. The simulation has analyzed the impact of failure nodes on coupled networks and verified the effectiveness of proposed attack strategy.

Through communication network, cyber-physical power systems can effectively monitor and control physical power grid, but this also increases the danger to systems from cyber attack. In this paper, we study the cascading failure triggered by cyber attack, which infects cyber nodes through malware and to endanger physical nodes through coupling links. First, the flow and topology models for cyber-physical power systems are detailed. In communication network, we analyze the mechanism of diffusion and infection among cyber nodes, and differentiate cyber nodes into three types, corresponding to different state of cyber nodes before and after cyber attack. And in physical power grid, the types of physical nodes are also classified. For different state of cyber nodes, we detail their impact on physical nodes and power flows in physical power grid. Simulation analyzes the robustness of systems and dynamics of cascading failure in different attack scenes and topology structure.