“Load-Type” voltage stability buffer calculation method

Voltage stability buffers are necessary to prevent the power system from operating near the voltage collapse point. Operating the system close to its collapse point can result in voltage instability due to system model inaccuracies. Current methods for determining voltage stability buffers are based on arbitrary safety margins of typically 5%. In this paper, a new method has been developed to provide for a defined process to calculate voltage stability buffers based on load model variations. The new method incorporates load models as well as traditional voltage stability methods (P-Q curves). A load composite mix model for western Kansas power system was used to determine a more appropriate voltage stability buffer taking into consideration its unique load mix. Results of applying the new method indicated that the calculated buffer (2.6%) was much lower than the arbitrary 5% buffer. Not using the proposed method to calculate voltage stability buffer may unnecessarily limit system capabilities for adding new loads.