Power system transmission network expansion planning using AC model
ABSTRACT An optimisation technique to solve transmission network expansion planning problem, using the AC model, is presented. This is a very complex mixed integer nonlinear programming problem. A constructive heuristic algorithm aimed at obtaining an excellent quality solution for this problem is presented. An interior point method is employed to solve nonlinear programming problems during the solution steps of the algorithm. Results of the tests, carried out with three electrical energy systems, show the capabilities of the method and also the viability of using the AC model to solve the problem.
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ABSTRACT: To investigate whether spectacle wear in children affects responses on the Intermittent Exotropia Questionnaire (IXTQ) or the Pediatric Quality of Life Inventory (PedsQL). We recruited 49 children, median age 8 years (range, 5-13 years), presenting with visual acuity 20/40 or better and an otherwise-normal eye examination (no strabismus), who either had no refractive error (n=29) or had refractive error corrected with spectacles (n=20). The IXTQ and PedsQL were completed, each comprising a child report (Child IXTQ, Child PedsQL) and a parent proxy report (Proxy IXTQ, Proxy PedsQL). In addition, the IXTQ contains a parent self-report (Parent IXTQ). Each questionnaire is scored from 0 (worst health-related quality of life [HRQOL]) to 100 (best HRQOL). Median scores were compared using Wilcoxon rank-sum tests. Child IXTQ and Proxy IXTQ scores were similar between groups; nevertheless, Parent IXTQ scores were lower for spectacle wearers (90.4 vs 97.1, p=0.01). Parent IXTQ questions that scored lower in the spectacle group were related to parental worry about permanent damage to their child's eyes, long-term eyesight, surgery, self-consciousness, and teasing. The PedsQL composite scores and all subscale scores were similar between spectacle wearers and nonspectacle wearers, both for Child PedsQL and Proxy PedsQL. Parental HRQOL, measured with the use of the Parent IXTQ, was lower for children wearing spectacles than for children who did not wear spectacles. There was no difference between spectacle and no-spectacle groups when either Child IXTQ, Proxy IXTQ, Child PedsQL, or Proxy PedsQL was used.Journal of AAPOS: the official publication of the American Association for Pediatric Ophthalmology and Strabismus / American Association for Pediatric Ophthalmology and Strabismus 02/2011; 15(1):24-8. · 1.07 Impact Factor
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ABSTRACT: The expansion plan obtained from a DC model based transmission expansion planning (TEP) model could be problematic in the AC network because the DC model is potentially inaccurate. However, solving TEP problems using the AC model is still extremely challenging. The motivation for this work is to develop a less relaxed network model, based on which more realistic TEP solutions are obtained. The proposed TEP model includes a linear representation of reactive power, off-nominal bus voltage magnitudes and network losses. Binary variables are added to avoid fictitious losses. Garver's 6-bus system is used to compare the proposed TEP model with the existing models. An iterative approach for considering the N -1 criterion during the planning process is developed and demonstrated on the IEEE 118-bus system. Simulation results indicate that the proposed TEP model provides a better approximation to the AC network and is applicable to large power system planning problems.IEEE Transactions on Power Systems 01/2013; 28(3):3471-3479. · 2.92 Impact Factor
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ABSTRACT: We apply a linear relaxation procedure for polynomial optimization problems to transmission system planning. The approach recovers and improves upon existing linear models based on the DC approximation. We then consider the full AC problem, and obtain new linear models with nearly the same efficiency as the linear DC models. The new models are applied to standard test systems, and produce high-quality approximate solutions in reasonable computation time.IEEE Transactions on Power Systems 12/2011; · 2.92 Impact Factor