The problem of unit commitment in an electric utility system is analyzed. The types of generating units considered include nuclear-steam, fossil-steam, thermalpeaking, conventional and pumped-storage hydro. The large problem of generating unit commitment, due to the inclusion of the nuclear unit, is decomposed into two stages. In the first stage, the relatively stable nuclear generation is optimized with respect to the generation from the large fossil-steam unit. Hourly generation levels for all the units in the system are determined in the second stage. AS a result of considering the startup-shutdown cost, the objective function has a fixed charge component in addition to first and second degree polynomials. Representation of the minimum turndown level and minimum Shutdown duration of the generator necessitates the use of O-1 variables along with continuous variables. The solution methodology presented here, applying an extension of the Lambda-Separable Programming, can handle these requirements efficiently. Application of the algorithm results in a minimum-cost generation schedule for all units in the system. Optimum generation levels of energy limited units are determined without using a preselected unit commitment order. The effect of startup-shutdown costs on the number of hours a Plant should operate is established. The cost and benefit of spent nuclear fuel reprocessing is analyzed and the effect of uranium prices on it (reprocessing) is shown. The model is tested using a sample system of six generating units. Hourly generation schedules, includig purchase and sale, are determined for two one-week periods while the nuclear generation is optimized for an entire year. / Ph. D.

This thesis addresses the problem of reactive power scheduling in a power system with several areas controlled by independent transmission system operators (TSOs). To design a fair method for optimizing the control settings in the interconnected multi-TSO system, two types of schemes are developed. First, a centralized multi-TSO optimization scheme is introduced, and it is shown that this scheme has some properties of fairness in the economic sense. Second, the problem is addressed through a decentralized optimization scheme with no information exchange between the TSOs. In this framework, each TSO assumes an external network equivalent in place of its neighboring TSOs and optimizes the objective function corresponding to its own control area regardless of the impact that its choice may have on the other TSOs. The thesis presents simulation results obtained with the IEEE 39 bus system and IEEE 118 bus systems partitioned between three TSOs. It also presents some results for a UCTE-like 4141 bus system with seven TSOs. The decentralized control scheme is applied to both time-invariant and time-varying power systems. Nearly optimal performance is obtained in those contexts.