## 3 Overview and Development of the Proposed Test System Considered for the Study
### The Power Grid System Considered for the Study
#### 3.1.1 Preparation of the IEEE 9 Bus Power System  
The model of the IEEE 9 Bus Power System is available in the Real-time Simulator Computer-Aided Design (RSCAD) software, version FX 1.3 instruction manual from RTDS Technologies Inc., referenced in [32]. Below is a significant recap of how the components were modified from the original IEEE 9 Bus Power System in the RSCAD software instruction manual. The components were rearranged and renamed, as shown in Table 6. The modified system is shown in Figure 12. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Original Name**} & \multicolumn{2}{c}{**Modified Names**} \\ \hline \multirow{2}{*}{**Busbar**} & **Component** & \multirow{2}{*}{**Busbar**} & **Component** \\  & **Connected to It** & & **Connected to It** \\ \hline
1 & G1 & G1 Bus & Gen1 \\ \hline
2 & G2 & G2 Bus & Gen2 \\ \hline
3 & G3 & G3 Bus & Gen3 \\ \hline
4 & None & Bus1 & None \\ \hline
5 & Unnamed load 1 & Bus2 & DLoad1 \\ \hline
6 & Unnamed load 2 & Bus3 & DLoad2 \\ \hline
7 & None & Bus4 & None \\ \hline
8 & Unnamed load 3 & Bus5 & DLoad3 \\ \hline
9 & None & Bus6 & None \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Renaming of components for the modified IEEE 9 Bus Power System. Figure 12: Modified IEEE 9 Bus Power System, adapted from the previous studies [32]. Area 1 and Area 2 in Figure 12 represent subsystems on RSCAD. These real-time simulations for an electrical system of two subsystems are performed in two RTDS hardware racks, Rack 1 and Rack 2. In the rest of this article, the two terms subsystems and racks are used interchangeably because they have the same meaning. The transmission line parameters of the IEEE 9 Bus Power System have been listed in Table 7. All per unit values have been derived from a base apparent power of 100 MVA [32]. RSCAD consists of two modules, namely the draft and runtime modules. The draft module deals with the modeling of the system itself, while the runtime module deals with the real-time simulations of the modeled system. The modeling on the draft module deals with gathering components that make up a power system model. This includes control components, such as control switches, sliders, push buttons, and other operating systems. After the completion of the model, the draft load flow simulation was executed to verify data accuracy and the initial conditions of the modeled system. Results were obtained and recorded in Table 8. These results are the same as those found in [32]. It has been stated in the references [33; 34; 35], that the reactive power transfer through substations (busbars) causes voltage stability challenges in the power grid. In this study, the assumption has been made that the increase in load demand means an increase in active and reactive power. We, therefore, configured the load increase simulation logic, as shown in Figure 13. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Lines**} & **Busbar to** & **Length** & **Resistance** & **Reactance** & **Susceptance** \\  & **Onnected** & **(km)** & **(PU)** & **(PU)** & **(PU)** \\ \hline Line12 & Bus1–Bus2 & 89.9300 & 0.0100 & 0.0850 & 0.1760 \\ \hline Line13 & Bus1–Bus3 & 97.3360 & 0.0170 & 0.0920 & 0.1580 \\ \hline Line24 & Bus2–Bus4 & 170.3380 & 0.0320 & 0.1610 & 0.3060 \\ \hline Line36 & Bus3–Bus6 & 179.8600 & 0.0390 & 0.1700 & 0.3580 \\ \hline Line45 & Bus4–Bus5 & 76.1760 & 0.0085 & 0.0720 & 0.1490 \\ \hline Line56 & Bus5–Bus6 & 106.6460 & 0.0119 & 0.1008 & 0.2090 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: IEEE 9 Bus Power System transmission line parameters.