Cyber Physical Distribution System Research Articles

Resilience enhancement strategy for cyber–physical distribution systems that considers cross‐space propagation of information risk

AbstractCyber–physical distribution systems with renewable energy should have high resilience under extreme conditions. However, in a distribution system with deep cyber–physical coupling, the propagation of information risk impairs the resilience of the system. This paper proposes a strategy to improve the resilience of cyber–physical distribution systems that considers cross‐space propagation of information risk. First, the mechanism for interaction between the cyber space and physical space is analyzed, and an information risk cross‐space propagation model is proposed. Second, the risk status of key device nodes is quantified according to the risk propagation model, and an optimization strategy for information risk control is obtained, whose objective function is the minimum risk of the coupling network. Third, a fault restoration strategy that considers cyber space risk is proposed. Finally, the paper reports experiments using the modified IEEE 33‐node and 123‐node distribution networks to simulate the proposed strategy and verify its effectiveness.

Coordinated Repair Crew Dispatch Problem for Cyber–Physical Distribution System

Reasonable repair crew dispatch can accelerate the service restoration in distribution systems after some components are damaged. It is worthy noting that as traditional distribution systems are involving into cyber-physical distribution systems composed of physical distribution networks and cyber networks, damaged components in these two networks should be coordinately repaired to achieve maximal restoration performance. However, repair crews in physical distribution networks are scheduled without considering the impact of the corresponding cyber networks in existing repair crew dispatch strategies. In this paper, a coordinated model is proposed to co-optimize the repair crew schedule of the two networks. Besides the cyber-physical interdependence between the two networks, backup power systems, topology reconfiguration and intentional distribution generator (DG) island are also modelled to improve the repair performance. The proposed model is formulated as a mixed-integer linear programming model, and its effectiveness is verified on the modified IEEE 33-node and 123-node test systems. Numerical results highlight the necessity of co-optimizing repair crew dispatch in both physical distribution networks and cyber networks.

Topology identification method of low-voltage distribution network based on measurement data of IoT devices

Accurate network topology information serves as the foundation for the operation of active control and active management, which have become indispensable requirements for the development of distribution networks with the growth of intelligence and information technology. The access of user-side Internet of Things (IoT) devices makes the topology of distribution network increasingly complex. IoT devices provide a considerable amount of information, which serves as the data basis for identifying the distribution network’s structure. The cyber–physical distribution system (CPDS) and the entire IoT distribution architecture are initially introduced in this study. Next, we enumerate the communication requirements of certain IoT services to illustrate the feasibility of IoT devices acquiring measurement data. Then, based on the measurement data that can be collected in real time by the user-side IoT devices, a data-driven low-voltage (LV) distribution network topology identification method is proposed through the similarity analysis of the measurement data. Finally, a real LV distribution network is used to validate the effectiveness and practicability of the proposed method, and the case study proves that the topology identification scheme is accurate and efficient. The method can provide correct physical connection information of LV distribution network, solving the problems of inflexibility and inefficiency of existing LV distribution network topology identification methods.

Collaborative planning of cyber physical distribution system considering the flexibility of data centers

With the development of energy transition and smart grid, the traditional distribution network has transformed into a cyber–physical distribution network (CPDS), which is multidimensional and heterogeneous. The increasingly abundant cyber and physical resources and deep coupling characteristics provide new challenges for distribution network planning. Based on a distribution network with multiple distributed resources and data centers, this paper proposes a cyber–physical collaborative planning method for a distribution network. First, according to the overall architecture of CPDS and the cross-layer control manner, the multiple distributed resources model and spatial–temporal migration model of data loads are established. Then, taking the minimal annual cost of distributed resources as the objective function, the collaborative planning of energy storage systems (ESSs) and corresponding smart terminal units (STUs), spatial–temporal migration strategy of data load, and communication network topology is carried out. Finally, the economics and feasibility of the proposed planning scheme are verified by the modified IEEE-33 bus distribution system. The results show that the collaborative planning method proposed in this paper can reduce the investment cost of distribution network planning and solve the voltage variation problem to a certain extent, so as to improve the economy and operational reliability of distribution network, and provide theoretical guidance for planners.

Reliability Assessment of Cyber–Physical Distribution Systems Considering Cyber Disturbances

With the development of communication technology, traditional distribution networks have gradually developed into cyber–physical systems (CPSs), from which the cyber system provides more protection for the grid and brings new security threat–cyber disturbances. Current research cannot scientifically measure the impact of cyber disturbances on the system and lacks reliability indices for a comprehensive quantitative assessment of CPS reliability from the perspective of cyber–physical fusion. If the impact of information disturbances on system reliability is not assessed accurately, it will not be possible to provide a scientific and reasonable decision basis for system planning and operation. Therefore, a set of reliability assessment methods and indices for distribution network CPSs considering cyber disturbances is proposed. Firstly, a reliability modeling method combining fault tree and Petri net is proposed to model the reliability of a distribution network CPS, which can improve the efficiency and accuracy of the modeling. Secondly, the system state is divided into two categories: normal operation state and cyberattack state. Then, generalized reliability indices considering cyber disturbances for distribution network CPSs are defined. Finally, through the tests on the modified IEEE RBTS BUS2 distribution network CPS, an analysis of the effects of information component failures, cyberattacks, and access network structures on system reliability is conducted in this paper to verify the efficiency of the proposed method and the rationality of the newly defined reliability indices.

Risk assessment in distribution networks considering cyber coupling

With the continuous development of information and communication technologies and their wide application in distribution networks, which have evolved into cyber-physical distribution systems (CPDS). Yet, interactions between cyber and physical systems mean power systems face a greater potential risk. Since feeder automation (FA) systems in a CPDS can quickly isolate faults and restore services, to reduce customer outage times, the potential effect of cyberattacks on FA systems is massive. This paper proposes a risk assessment method for cyberattacks in distribution networks considering cyber coupling. The proposed method takes into account the impacts of cyber systems on power systems, and vice versa. Regarding the cyberattack, an attack method to mislead the judgment of FA systems by tampering with monitoring data of remote terminal units (RTUs) is analyzed, and a Bayesian attack graph (BAG) model is adopted to quantify the successful probability of RTUs. To calculate the attack consequences, a power supply restoration model considering the interdependence of cyber and physical systems is developed, which is measured in scale and in duration to full restoration. The proposed methodology is tested and validated using the modified IEEE 33-node and CPS 62-node test systems. This study highlights the importance of assessing distribution network security from the cyber-physical point of view.

Analytical reliability assessment of cyber-physical distribution system with distributed feeder automation

Cyber-physical distribution system (CPDS) handles power grid faults by feeder automation. The reliability assessment of CPDS has been intensively discussed for centralized feeder automation (CFA) in existing researches. However, the inapplicability of CFA reliability models, and the low computation efficiency issue of the mostly used Monte Carlo method greatly limits their application in practical engineering cases of the large-scale CPDS with the distributed feeder automation (DFA) mode. Thus, this paper proposes a region-based analytical reliability assessment method for DFA, which has high computation efficiency in the large-scale CPDS. Firstly, the reliability impacts of cyber system anomalies in the DFA mode are analysed and the cyber reliability models are built considering both cyber device failures and cyber-attacks. Then, the cyber system status is integrated into malfunction probability modelling of switches for reliability assessment. Finally, the load reliability is assessed based on the fault region division by the proposed analytical method and the reliability indices are calculated. The accuracy, efficiency and scalability of the proposed method are verified in case studies.

Optimal locating method of edge computing device in cyber physical distribution system

With the development of interconnection of massive terminals, high maintenance of equipment data and complexity of network structure in distribution system, the traditional information processing mode based on single cloud master station has some disadvantages, such as high data transmission delay, high congestion, information far away from equipment and slow queuing processing. Edge computing can make local fast analysis and decision for data in the near terminal device side, which can effectively make up for the deficiency of cloud computing. As the cornerstone of edge computing, edge control processing node is the first premise to realize fast response control of cyber physical distribution system (CPDS). In this paper, a new method of edge computing node deployment is proposed for the distributed edge computing requirements of cyber physical distribution system, considering the cyber stability and power stability. The community theory based on distribution network power flow and line impedance is used to divide the edge computing autonomous region, and the calculation model of cyber stability and power stability of CPDS network is established, then the optimal deployment of CPDS edge computing nodes is solved by the hybrid entropy calculation of cyber and power. Finally, an improved standard example is used for simulation analysis. The simulation results show that the ECN deployment scheme proposed in this paper can effectively reduce network congestion, improve network response speed and realize optimal control of distribution network.

Reliability Evaluation of Cyber Physical Distribution System considering EPON

As cyber-physics highly coupled distribution system, the influence of communication network on the reliability of power supply can not be ignored. Based on the EPON redundant protection network, this paper analyzes the influence of the loss of cyber link effectiveness on the self-healing control process in the process of power distribution network failure. With the help of the region adjacency matrix, combined with the cyber system failure model, the classification algorithm of the region after failure is given, and a reliability evaluation method coveannular different cyber system failure modes is proposed. Finally, the feasibility of this method is verified by a case study, and the influence of EPON cyber element failure rate and EPON networking mode on the reliability indices is compared and analyzed.

Identifying single‐phase to ground fault based on line multi‐dimensional data in cyber‐physical distribution system

Single-phase to ground fault is the most common line fault in power distribution systems, which may result in an electrical fire and personal safety problems. Particularly, it is more difficult to identify the fault occurring in the system in which the neutral point is grounded via Petersen coil. This paper proposes a new scheme based on line multi-dimensional data in cyber-physical distribution system, where line multi-dimensional data is used to extract the fault characteristics and thus to identify the faulty line. First, the circuit is analyzed and the difference-like algorithm is used to extract the current signal difference value from the line multi-dimensional data as the feature quantity. In order to reduce the impact of the measurement error on the result, the authors employ the deep neural networks to process the line multi-dimensional data, and demonstrate that this method can effectively resist the error interference. A simulation based on a previously studied model has been carried out and the results show the superiority compared to the fifth harmonic identification method. In addition, the test results obtained in the Dynamic Simulation Laboratory of Huazhong University of Science and Technology also demonstrate the practicality of the scheme.

Elaborate Reliability Evaluation of Cyber Physical Distribution Systems Considering Fault Location, Isolation and Supply Restoration Process

The existing reliability models of the cyber physical distribution systems, which are mostly based on some simplified assumptions, cannot accurately evaluate the reliability of complex cases in practical engineering applications. To solve this problem, an elaborate reliability evaluation method considering the whole process of fault location, isolation and supply restoration is proposed. This paper establishes reliability models of components and the two systems, summarizes the mapping relationship between various cyber system failures and the physical fault handling into several laws, proposes the reliability evaluation procedure in the framework of Monte Carlo method, and verifies the feasibility and effectiveness of the method in an actual distribution network cyber physical system. In the proposed method, the multiple component characteristics, complex topological structure, coupling relationship of the cyber-physical distribution systems, and the actual human-computer joint participation are considered in the analysis of fault location, isolation and supply restoration process, which provides a effective and accurate theory for the application of reliability evaluation in the actual distribution network and prosumer energy management system.

A Reliability Assessment Method of Cyber Physical Distribution System

A reliability assessment method of cyber physical distribution system is proposed. The sequential process of fault processing is analyzed using event tree model to quantitatively describe the effect of failure in cyber system on fault processing of distribution network. The sequential state sequence of cyber-physical system and the dynamic process of fault processing are simulated by Sequential Monte Carlo method, and then reliability indexes are calculated. The simulation results verify the feasibility and effectiveness of the proposed method.

Reliability Modeling and Evaluation of Active Cyber Physical Distribution System

To enable an in-depth study of active cyber-physical distribution network, a cyber subsystem model is urgently needed to describe the performance in distribution communication. The methods for quantifying the interactions between subsystems, especially indirect interactions, have not been adequately studied in the existing research. In this paper, a novel model is developed to evaluate the validity of cyber link considering dynamic routing, delay, and communication error, particularly the cyber traffic. Then, an analytical method is presented to quantify the impact of cyber faults considering the functionality validity during distribution automation. And the reliability of cyber and physical subsystems is evaluated based on nonsequential and sequential Monte Carlo methods, respectively. Finally, a test system for reliability evaluation is established to analyze the influences of cyber faults. In addition, sensitivity analyses on the impact of cyber network traffic, element failure rate, and network topology and access communication technology are carried out. The obtained results could provide useful insights into planning and operation of active cyber-physical distribution networks.

Reliability Assessment of Cyber Physical Distribution System

The traditional distribution network is gradually evolving into the cyber physical distribution system (CPDS) to suit the new characteristics of the distribution network. Distribution network plays an important role of risk source and vulnerable sector. Therefore, it is necessary to do some research on the reliability assessment for CPDS. The key factors of reliability assessment for the distribution network mainly including network components, cyber medium, network topology are firstly analyzed. Reliability assessment index is then summarized in terms of traditional physical system, common cyber system and the CPDS from extensive literature. This is followed by a review of reliability assessment methods in CPDS, which is mainly categorized into two aspects. Finally, the future research emphases are discussed.

Key issues and technical route of cyber physical distribution system

Relying on the National High Technology Research and Development Program, this paper introduced the key issues in Cyber Physical Distribution System (CPDS), mainly includes: composite modelling method and interaction mechanism, system planning method, security defence technology, distributed control theory. Then on this basis, the corresponding technical route is proposed, and a more detailed research framework along with main schemes to be adopted is also presented.