Abstract
This paper describes a mathematical model and the developed solution algorithm to solve an integrated active/reactive dispatch while retaining competitive aspects. The main drive for this research was the recognition that the introduction of competitive mechanisms lead to a certain extent to a decoupling between active and reactive power scheduling. Aiming at remarrying them, the developed approach includes an initial bid based uniform price active power auction run by the Market Operator, followed by a technical validity analysis run by the System Operator. If necessary, the System Operator uses adjustment bids to recover the technical feasibility of the dispatch. These bids are presented both by the demand and by generators meaning that demand can play an important role in increasing the liquidity of this specific market. This approach also includes capacitor banks and transformer taps leading to a combinatorial problem solved using Simulated Annealing. Finally, the paper includes results from a case study based on the IEEE 24 Bus Test System to illustrate the interest of this type of approaches.

Abstract
Modeling uncertainties in power systems has long interested researchers. Nowadays, as in 70's, the volatility associated with generation or fuel prices, for one side, and the uncertainties related with load forecasting and generation capacity, for another, places a new emphasis on this kind of problems. As a result of this renewed interest, in this paper we are enlarging the original Fuzzy Optimal Power Flow, FOPF, model in order to consider not only load uncertainties, but also uncertainties in generation or fuel prices, specified using trapezoidal fuzzy numbers. This new approach is based on multiparametric linear programming techniques that lead to the identification of a number of critical regions covering all the uncertainty space. This contributes to build more accurate membership functions of all variables, namely generations, branch flows and power not supplied.

Abstract
This paper describes two new active/reactive dispatch models to be used by System Operators in order to assign reactive power and to validate the economic schedules prepared by Market Operators together with the injections related with Bilateral Contracts. When talking about electricity markets one usually refers to active power markets paying less attention to ancillary services, namely to reactive power/voltage control. This usually leads to a chronological sequence of activities that may lead to inefficiencies because active and reactive powers are coupled given the capability diagram of synchronous generators, the ac power flow equations and the branch thermal limits. In this paper, we propose new models to remarry active and reactive allocation procedures based on a market approach as a way to ensure operation transparency. The resulting optimization problems are solved by a Sequential Linear Programming, SLP, approach that allows one to compute active and reactive nodal marginal prices at its final iteration. The paper includes a case study based on the IEEE 24 Bus Test System to illustrate the application of the developed models and demonstrate their interest in the scope of restructured power systems.

Abstract
The restructuring of power systems has often originated the organization of power system operation planning in a set of chronological sequence of activities that are reasonably decoupled. This means that the Market Operator purely economic schedule together with bilateral contracts is conveyed to the System Operator to be validated from a technical point of view. The System Operator also has to schedule reactive power but some of its reactive power requirements may be unfeasible given the previous active power schedules and the alternator capability diagram. Apart from this aspect, active and reactive powers are coupled in determining the eventual violation of branch thermal limits and reactive power has a well-known local nature. While recognizing the Coupling between active and reactive powers, the models presented in this paper admit that the Market Operator schedule may have to be altered either because there are branch limit or nodal voltage violations or because the System Operator requires a reactive output that can not be provided Clue to the previous active schedule. The changes on the initial schedule are determined by solving an optimization problem that uses adjustment generator or demand bids. Apart from that, we adopted a symmetric fuzzy programming approach recognizing that some constraints have a soft nature, namely the ones related with voltage and branch flow limits. To solve the resulting non-linear problem we used Sequential Linear Programming, SLP. At its final iteration this problem also Outputs active and reactive nodal marginal prices useful to build more effective tariff systems. The paper includes a case study based on the IEEE 24 bus test system.

Abstract
This paper addresses the generation expansion-planning problem describing a model that generation companies can use to get insight to this problem and to more completely study and characterize different investment decisions. In the last 20 years, the generation activity evolved from a situation in which it was part of vertical companies to unbundled market agents that face a much more risky and uncertain environment. This explains the need to develop this kind of simulation tools to help them building their investment plans as well as analyzing the impact of possible decisions of other players. The simulation model considers a number of possible generation technologies and aims at characterizing the corresponding investment plans from an economic point of view having in mind that market prices, the demand growth, investment and operation costs, as well as other factors, are affected by uncertainties. These uncertainties are modeled by pdf functions and the solution approach uses a Monte Carlo Simulation to sample particular values used to analyse the different investment alternatives from an economic point of view. Finally, the paper presents results from a Case Study illustrating the use of this approach.

Abstract
In general, distributed generation is not subject to a centralized dispatch and reactive power generation is usually restricted by operation rules defined by the distribution system operators. With the growth of distributed generation and microgrids in distribution networks, the development of voltage control functionalities for these units needs to be investigated. This requires a new operation philosophy to exploit reactive power generation capability of distributed generation and microgeneration with the objective of optimizing network operation: minimize active power losses and maintain voltage profiles within adequate margins. This implies that distributed generation should adjust their reactive power generation, i.e. supply an ancillary service of voltage and reactive power control. In addition to the growth in distributed generation penetration, microgeneration is expected to develop considerably and contribute to the implementation of efficient voltage control schemes. For this new scenario, a hierarchical voltage control scheme must be implemented, using communication and control possibilities that will be made available for microgrid operation. Technical advantages and feasibility of this operation philosophy are investigated in this chapter by analyzing the impact of the proposed control procedures on distribution networks. In addition, the identification of control action needs is assessed by solving an optimization problem, where voltage profiles are improved and active power losses minimized, subject to a set of technical constraints. The solution for this problem is obtained using an Evolutionary Particle Swarm Optimization algorithm. The control algorithm implemented will enable dealing even with extreme situations, where reactive power control is not sufficient to maintain system operation and therefore generation shedding actions must be performed.