## 1 Introduction  
With the application of intelligent technology, the demands for low-carbon living, and the driving forces of market regulation and government policy, the traditional power system is currently facing a significant transformation towards the smart grid system, for which the main features include self-healing and being of high quality, allowing various forms of power generation, and improving power market and asset optimization [1; 2]. Advanced information technology is the key to the smart grid, and therefore bottlenecks located in the information collection, transmission, processing and sharing of the traditional power grid should be solved [3]. It is necessary to address the technology of the sensing measurement systems, data representation and storage systems, analysis and decision systems, control and execution systems, and so on [4]. The computing and communication processes are deeply embedded in the power physical process, which interact closely with physical process and bring new capabilities. Therefore, the smart grid can be studied from the perspective of cyber-physical integration. With the application of 3C technology (i.e., calculation, communication, and control),there is an interaction of power flow and information flow in a considerable number of power services. Therefore, the power system has transformed into an open, interconnected, stable, and self-consistent system, namely the cyber-physical power system (CPPS) [5; 6; 7]. CPPS can not only obtain data from the environment, fuse data, and extract effective information, but also act on the environment through the effector. The key connotation of CPPS is the wide interconnection and integration of the physical power grid, sensor network, computing units, communication network, and control modules, through which the power system operates in a reliable, efficient, and real-time synergetic mode [8; 9]. The application of information and communication technologies (ICT) not only increases the intelligence level, but also brings control complexity to the power system operation. The power system load control is used as an example. In the traditional operation mode, the load usually plays the role of a controlled object, while in the CPPS environment, with access to intelligent terminal equipment and the construction of advanced measurement infrastructure, the system has better observability and controllability of the load. On one hand, from the perspective of the user, the insertion of active load gains a better ability for information collection and demand response. On the other hand, from the perspective of a large power grid, the wide installation of intelligent controllers provides better technical support for resource configuration, and security and stability control, etc. However, the wide area information also has higher requirements for the reliability and speed of communication. The delay, error, or disruption of communication may cause the system to become unable to respond to disturbances in time, or make the controller fail to take effective measures, especially under a state of emergency. As a result, the global optimal coordinated control of an interconnected power grid cannot be guaranteed. The key of CPPS research is to explore the mechanism of influence of the information field on the primary power system. In traditional power system research, the whole system is divided into several independent modules according to function, whose dynamic characteristics are described by differential algebraic equations. However, CPPS contains many items of distributed computing and control equipment where modules with various mechanisms and forms are deeply interconnected by the information communication system. Therefore, the original attributes of the power, communication, and control devices are influenced and changed by each other, which requires research within a common framework.