Optimized Transmission Expansion Planning with Bus-Splitting in Grids with High VRE Penetration

In the current era, characterized by a growing commitment to environmental sustainability, the transition towards renewable energy sources becomes imperative. This shift has significantly increased the integration of variable renewable energy (VRE) resources into the power grid, introducing new challenges within an infrastructure originally designed with less operational flexibility. The incorporation of VREs, along with the increasing demand from variable loads, introduces high variability in power injections, resulting in load dropping and VRE curtailment. Consequently, power system planners are increasingly investigating innovative transmission expansion planning (TEP) strategies, aimed at enhancing the grid's adequacy and its adaptability to the rapidly evolving energy landscape. Literature indicates that traditional approaches to TEP predominantly focus on augmenting network adequacy through strategies such as line addition and line switching. This study endeavors to build upon these methodologies by integrating the technique of substation bus splitting into the transmission expansion framework. The objective is to explore how this integration can improve the expansion plan solution by incorporating bus-splitting options and optimal power flow solution with the objective of minimizing curtailment of VRE. This work introduced an innovative approach by modeling bus-splitting and optimal dispatch within a Direct Current Optimal Power Flow (DCOPF) framework. The methodology is implemented in a custom-developed MATLAB® script, designed to integrate bus-splitting into the optimization process. To demonstrate this approach, the framework implemented in a modified IEEE 14-bus test system. The modification focused on VRE integration and inclusion of bus-splitting in candidate buses. Simulation results revealed that, for the given scenario, integrating line addition decision and optimum generation dispatch with bus-splitting can potentially result in reduction in the number of line addition by as much as 50%. Additionally, the reduction of VRE curtailment in the generation dispatch optimization process improves by up to 57.21% when bus-splitting option is integrated. These results present promising economic benefits in terms of reduction in expansion investment and savings from minimizing VRE curtailment.