Calculation of TTC for multi-area power systems based on improved Ward-PV equivalents

The total transfer capability (TTC) calculation is restricted by limited information exchanges in multi-area power systems. This study presents a multi-area TTC calculation method based on improved Ward-PV equivalents. In this study, only boundary bus voltages and predictors need to be exchanged between individual areas during the calculation. An improved Ward-PV external network equivalent is proposed as a network decomposition approach. The repeated power flow (RPF) algorithm with a self-adaptive predictor is implemented in each area's TTC calculation. Each area uses network equivalent models to calculate its own TTC via RPF. A modified distributed power flow method is employed as a correction algorithm to adjust power flow in all individual areas during the TTC calculation. The proposed method is verified on the IEEE 118-bus system with all operating limits and branch N - 1 contingencies considered. Results demonstrate the validity and the accuracy of this method.