Evaluation of available transfer capability using transient stability constraints based on line flows

Available transfer capability (ATC) is that extra power that can be transported safely through the transmission system without compromising the network reliability. In the determination of ATC, power flow models play a significant role. In this research, the line-flow-based (LFB) model was used to develop a methodology for the evaluation of ATC. This work, for the first time, exposed the LFB model to the stability studies. A new methodology for a possible fast evaluation of a power flow was presented. The proposed method involves a transient stability constrained line-flow-based (LFB) fast contingency screening. This 'direct' method incorporates transient energy function (TEF) to carry out the evaluation of a power system. Results of the proposed LFB were compared with those obtained from the conventional Newton-Raphson (N-R) method. It was observed that the stable re-dispatch could be obtained by the LFB method within ∼ half the computation time as compared to the time required for the N-R method. Since the LFB method was based upon identification of the stable equilibrium points of the TEF, the proposed method appears to be inherently capable of delivering a stable power dispatch. In addition, a new index called critical energy performance index (CEPI) has been introduced to indicate the level of stability and to assist in the decisions related to the re-dispatch.;Further, ATC calculation was treated as an optimal power flow (OPF) problem. An OPF problem can be solved to achieve an objective at the specified time instance subject to the equalities and inequalities constraints. The LFB transient security constrained OPF (LFB-TSCOPF) was established, after which it was modified to evaluate the stability constrained ATC. The OPF results were compared with other known results from different methods in the literature. The OPF results of the active power and total optimal costs appear quite promising and consistent with other known methods. The LFB-TSCOPF re-dispatches real power by applying the performance index as an indication of the generator unit(s) to be rescheduled. The LFB-TSCOPF provides a more comprehensive linear model, reduces computation time, and can be useful for online stability studies. The CEPI index helped to reduce the list of credible contingencies for consideration of the ATC evaluation and, therefore, the computation time. Also, the direct method of the CEPI captured the impact of bilateral and multilateral transactions on the severity of loss of transmission lines.;The transient stability constrained LFB power flow, OPF, and ATC were demonstrated using IEEE 9, 14, and 39 bus test systems. The results can be deployed for fast assessment of the impact of transactions in an electric power system.