A Simplified Study Method on the Improvement of Voltage Stability by New Transmission Lines

This paper proposes a new method for calculating the power system voltage stability point, when seeking to improve voltage instability limit by adding new lines to a power grid. Instead of the conventional iterative power flow calculation-based P-V simulation method, we suggest a method to analytically determine the voltage stability limit power using the Thevenin equivalent model in the demand bus. The Thevenin equivalent circuit in the demand bus can be obtained through fault calculations and no-load bus voltage calculations. By reflecting a high X/R ratio inherent in the AC power grid to simplify the model, we could determine the voltage stability limit power throufh an analytical method that does not reply on simulations.BRSuggested method was tested compared on the IEEE-14 system and PSS/E P-V linerized simuation. Buses related to control devices-generator and transformer primary buses were relatively large, however, in buses without control devices, average errors were below 3.8%, standard divation was 4.9% showing lower errors with higher X/R ratios. Therefore, this method can ve utilized for rapid decision-making in the planning and ooperation of transmission lines in the power grid by quickly comparing and evaluatig voltage stability margins due to additional power or on/off control of lines, especially in remote demand points where control devices such as generators are not nearby.