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• Analytical method for estimating the size of a loss-of-generation disturbance. • Investigates a linear relationship between power and frequency deviations of CCGTs. • Improves disturbance size estimation accuracy with CCGT units' negative droop gain. • Estimates the disturbance size for pre-and post-event conditions. • Provide an approach that computes deviations in post-event demand-side consumption. With the substantial popularity of combined cycle gas turbine (CCGT) power plants in the nowadays power systems, special care must be taken to regulate frequency due to unique frequency response characteristic of the full-loaded CCGT units. This unique feature is documented in the literature; however, its effect on determining frequency response of the power systems was not addressed in detail. This study proposes a new analytical method to achieve a more accurate estimated size of a loss-of-generation disturbance. This method considers demand-side power deviations and transmission lines power loss as well as unique frequency response of the CCGT units following the event. Firstly, it is exposed that there is an approximately linear relationship between power and frequency deviations of these plants in a real-world power system despite the complexity of the CCGT model. This relationship may be represented by a negative droop gain. Next, the derived CCGT's linear characteristic is formulated in the disturbance size estimation process. Finally, the effectiveness of the proposed modifications is demonstrated through extensive simulations on a 36-zone Great Britain equivalent test system. [ABSTRACT FROM AUTHOR]

This paper describes a modified Particle Swarm Optimization (PSO) method called Fitness Distance Ratio (FDR) PSO to solve the Optimal Power Flow (OPF) problem with ramp rate limits of the generators. To avoid premature convergence of the conventional PSO, a velocity updation has been carried out to improve its convergence performance. The proposed method is tested on 5-unit, 10-bus test system and 39 bus New England system. To validate the effectiveness of the proposed method, the OPF results are compared with other optimization methods. Transient stability limit of the generators are also incorporated in the formulation of OPF problem. Wheeling transactions and contingency analysis are also carried out on the New England test system and the system stability is checked. A 24-hour load curve is considered for the same system and transient stability constrained OPF solution is obtained through FDR PSO method and the results are presented. [ABSTRACT FROM AUTHOR]