Abstract
Power system transient stability assessment (TSA) and control is a complex problem. TSA from the perspective of individual machine Kimbark curves forms a distinctive approach. On the other hand, transient stability constrained optimal power flow (TSC-OPF) has been adopted widely for determining preventive control actions against transient instabilities under a given contingency. This paper presents a strategy for transient stability control, which mainly integrates the concepts of individual machine methods based TSA and global TSC-OPF. The proposed workflow is mainly based on the most severely disturbed machines (MDM) and their critical trajectories. These are utilized in deciding the number of TSC-OPF transient stability constraints, the minimum upper time limit for TSC-OPF solution interval, and security-based transient stability constraint of individual machines. Further, the application of the proposed method is explained with respect to stabilization of three different transient instability scenarios viz., transient instability originates from first swing instability, transient instability originates from multi swing instability but leads to first swing instability as fault duration increases, and transient instability originates from multi swing instability, but never leads to first swing instability as fault duration increases. IEEE 39 bus and 118 bus test system are considered for testing the proposed control strategy. The proposed approach, which expresses the transient stability constraints in global TSC-OPF in terms of some selective machine (i.e MDMs) critical trajectories not only forms a distinctive approach but also provide a smooth reconciliation between economy of operation and security level while ensuring transient stability under a given contingency.
Highlights
P OWER system transient stability refers to the ability of synchronous machines to maintain synchronous operation after being subjected to a large disturbance [1]
Given an unstable fault scenario, an empirical rule is developed based on critical rotor angle trajectories of individual machines to determine the minimum upper time limit of integration interval for which transient stability constrained optimal power flow (TSC-OPF) needs to be solved to ensure system stability. (iii)
Security-based transient stability constraint (STSC) is defined for an individual machine as a function of its maximum rotor angle of critical trajectory which can be incorporated into TSC-OPF model for controlling security level versus economy of operation
Summary
P OWER system transient stability refers to the ability of synchronous machines to maintain synchronous operation after being subjected to a large disturbance [1]. How to modify stability constraints on these selective machines so that smooth reconciliation between economy of operation and security level under a given contingency is achieved through TSC-OPF This approach of forming transient stability constraints directly from selective individual machines forms a distinctive approach and eliminates dependency about all machines rotor angle information during transient condition simulation to determine transient stability indices. Given an unstable fault scenario, an empirical rule is developed based on critical rotor angle trajectories of individual machines to determine the minimum upper time limit of integration interval for which TSC-OPF needs to be solved to ensure system stability. Security-based transient stability constraint (STSC) is defined for an individual machine as a function of its maximum rotor angle of critical trajectory which can be incorporated into TSC-OPF model for controlling security level versus economy of operation.
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