The grid of the future will have a higher penetration of grid edge devices that enable increased automation and grid edge intelligence. The current grid models do not account for these gridedge devices, and the creation of cyber-physical models for the grid is essential to understand the impact of these devices. Although existing cyber-physical power system (CPPS) models have been developed using a wide variety of approaches, a comprehensive review of the validity of these approaches and their suitability for modeling the future grid has not been performed. In a CPPS, the physical layer usually consists of the power grid and protection devices, whereas the cyber layer consists of communication, computation, and control components. This paper provides a review on the existing approaches to model CPPS and to characterize the inter-and intra-actions for distributed autonomous systems. The CPPS models can then be used to perform various analyses, such as cyberattack analysis, threat analysis, and resilience analysis. A qualitative evaluation criteria for the various modeling paradigm is discussed to help researchers understand the trade-offs in choosing the right modeling method for their particular application.INDEX TERMS Cyber-physical power systems (CPPS), cybersecurity, finite state machines, graph network, modeling techniques, system and control method, test beds.
I. INTRODUCTIONP OWER grid modernization has gained significant momentum in the last decade. As part of the modernization, advanced communication and automation technologies are being deployed in power systems, and the resulting systems are known as cyber-physical power systems (CPPS), which consist of physical (the power grid) and cyber (e.g., communication and computation systems) layers [1]. CPPS leverage two-way cyber-secure communication systems to improve the monitoring, protection, and control of power system components to achieve a smart grid concept with enhanced reliability, resilience, security, and sustainability [2], [3]. Although advanced technologies in the cyber layer improve the operation and control of power systems, they can expose power systems to multiple types of cyber and cyber-physical attacks [4], [5]. The increase of cyber threats can jeopardize the power system's ability to provide reliable and efficient power supply [6]; therefore, accurate and detailed modeling of CPPS and the dependencies between the physical and cyber systems in a CPPS is a necessary step toward the analysis, evaluation, and enhancement of the CPPS's reliability and resilience.
A. RELATED WORKExtensive reviews on cyber-physical systems (CPS)-in particular, CPPS-modeling, analyses, evaluations and enhancement methods have been conducted [7]- [10]. The authors of [7] provided a review on the architectural model-