# Communication Architecture for Grid Integration of Cyber Physical Wind Energy Systems
## 3 CPWES Modeling and Assumption
### Traffic Model for Wind Turbine Based on IEC 61400-25  
In order to model the wind turbine subsystems, we considered the IEC 61400-25 standard, which is an adaption of IEC 61850 [19]. IEC 61400-25 provides information for the monitoring and control of wind power plants. We assumed that a wind turbine consists of 10 logical nodes (LNs): _WROT_, _WTEM_, _WGEN_, _WCNV_, _WNAC_, _WYAW_, _WTOW_, _WTRF_, _WMET_ and _WFOU_, as shown in Equation (1). Each LN represents a wind turbine sub-system, as given in Table 1.  
\[WT_{LN}=\ \{\textit{WROT},\ \textit{WTEM},\ \textit{WGEN},\ \textit{WCNV},\ \textit{WNAC},\ \textit{WYAW},\ \textit{WTOW},\ \textit{WTRF},\textit{WMET},\textit{WFOU}\}, \tag{1}\]  
Different types of sensor nodes and measurement devices were connected to different turbine parts to measure different parameters, such as voltage (\(V\)), current (\(A\)), wind speed (\(WdSpd\)), wind direction (_WdDir_), temperature (_Tmp_), Humidity (_Hum_), displacement (_Disp_), and pressure (_Pres_). Equation (2) defines types of sensor nodes (\(SN_{TYPE}\)) inside a wind turbine sub-system.  
\[SN_{TYPE}\subseteq\ \{V,\ 1,\ WdSpd,WdDir,\ \textit{Tmp},\textit{Hum}, \textit{Disp},\textit{Pres},\ldots\}, \tag{2}\]  
Each sensor node (\(SN_{l}\)) was identified by a senor identification ID (\(SN_{ID}\)), sensor type (\(SN_{TYPE}\)), and the physical location inside the wind turbine (\(WT_{LN}\)), as given in Equation (3).  
\[SN_{l}=\ \{WT_{LN},SN_{ID},\ SN_{TYPE}\}, \tag{3}\]  
Figure 3: Proposed OPNET model for the wind farm communication architecture. OPNET: optimized network engineering tool.  
Regarding the data acquisition and monitoring layer, the authors in Ref. [20] designed a data acquisition system to be installed on a real wind turbine. The total number of sensor nodes was about 29. The sensor nodes were divided into two groups with sampling rates: 50 Hz (low speed) and 20 kHz (high speed). In our model, the total number of sensor nodes defined inside a wind turbine was 108 [21]. Figure 4 shows a schematic diagram of the cyber physical model for a wind turbine system where seven LNs are located at the turbine nacelle and three LNs are in the bottom of the tower. Two data collection units were considered for aggregating the traffic from different turbine subsystems.  
To determine the amount of data generated from each sensor node (data rate, SN\({}_{DR}\)), we defined the sample size (N\({}_{B}\)), the sampling rate (F\({}_{S}\)), and the number of channels (N\({}_{C}\)), as shown in Equation (4).  
\[\text{SN}_{DR}=\text{N}_{B}\times\text{F}_{S}\times\text{N}_{C}, \tag{4}\]  
\begin{table}
\begin{tabular}{c c c c} \hline
**LN** & **Description** & **LN** & **Description** \\ \hline _WROT_ & Wind turbine rotor information & _WNAC_ & Wind turbine nacelle information \\ _WTRM_ & Wind turbine transmission information & _WYAW_ & Wind turbine yawing information \\ _WTGEN_ & Wind turbine generator information & _WTOW_ & Wind turbine tower information \\ _WCNV_ & Wind turbine converter information & _WFOU_ & Wind turbine foundation information \\ _WTRF_ & Wind turbine transformer information & _WMET_ & Wind power plant meteorological information \\ \hline \end{tabular}
\end{table}
Table 1: Wind turbine logical nodes [18].  
Figure 4: Schematic diagram of the cyber physical model for the wind turbine system.  
Given the displacement sensor as an example, the sensor generates 10 samples/s and the number of channels required for the measuring of data is 2 channels. The total amount of data is 320 bits/s, considering a sample size of 16 bits. Table 2 shows how to calculate the measuring requirement for different sensor nodes. We calculated the sensing data for all sensor nodes inside a wind turbine (108 sensor nodes), and Table 3 shows the traffic configuration at each wind turbine subsystem.