# Communication Architecture for Grid Integration of Cyber Physical Wind Energy Systems
## 1 Introduction  
There is a growing interest in increasing the penetration rate of renewable energies, such as wind power, solar energy, and biomass. Among them, great attention has been given to wind energy, and several large-scale wind farm (WF) projects are scheduled to be constructed in the near future. In South Korea, the cumulative installed wind power was about 610 MW and 835 MW by the end of 2014 and 2015, respectively [1]. In September 2014, the Korean government announced a long-term plan for new and renewable energies, with a target of obtaining 5.0% of the total primary energy supply from renewable energies by 2020, and 11.0% by 2035. Wind power will supply and contribute about 18.2% of the total power supplied by new and renewable energies by 2035 [2]. The planned WF projects include Southwest phase 1, Tamra, Hanlim, Daejeong, North-East, Shinchong, and Quiduck. The complete list of WF projects is available on the Korea wind power industry association (KWEIA) website, including site location, total capacity, manufacturer, and number of turbines [3]. As an increasing number of WFs are integrated into the power grid, communication infrastructure will play an important role in enabling the real-time operation, monitoring, and control of both wind turbines and the electric power grids to ensure grid stability [4]. Communication infrastructure in WF is considered as an example of an industrial network that requires special consideration in network design owing to the following reasons [5; 6; 7; 8; 9; 10; 11; 12; 13]: (1) WFs are built in remote locations (onshore/offshore) where abundant wind resources are available. The remote sites lack established communication infrastructure or cellular coverage; (2) access to WF is difficult, especially in the case of offshoresites where the only means of access is by boat or helicopter. Furthermore, weather conditions may postpone/prevent access to WF for an unspecified period. Therefore, remote monitoring and control are highly required; (3) as advancements in the wind turbine industry enable wind turbines to migrate from shallow water to deep water with taller towers and blades, recent studies show the increase in the failure rate of large wind turbines, which impacts the availability of wind turbines and their operation and maintenance costs [14]. Therefore, condition monitoring systems (CMS), structure health monitoring (SHM), and supervisory control and data acquisition unit (SCADA) systems are used for real-time monitoring; (4) the monitoring scope of large-scale WFs has been expanded to cover the operation status of wind turbines, generated power, meteorological masts (met-mast), and substations. Therefore, a considerable amount of data needs to be transferred between WFs and their control centers, which will increase the burden on the communication infrastructure. The main components of a WF are wind turbines, electric systems, a substation, and met-masts. Communication infrastructure is used to connect WF components together using wired/wireless technologies. Owing to coupling between the physical system and the cyber communication network, a WF is considered to be a cyber physical system. Considerable research studies and investigations have been conducted to study the WF electric power system. However, information on the corresponding communication networks of the proposed models is limited. Furthermore, few research studies have been carried out to investigate the SCADA system and the underlying communication infrastructure. Moreover, it is difficult to find detailed information about how to design the communication network for a wind energy system, as the designs are the proprietary information of each manufacturer. The only available published information consists of outline descriptions of the communication infrastructure of a number of real WF projects [4; 15; 16; 17]. The extent of the research on communication infrastructure and its role in supporting the grid integration of large-scale WFs is insufficient.