Abstract
In the scope of the revision of the Portuguese Tariff Regulation, the Power Systems Unit of INESC Porto concluded a consultancy study aiming at estimating the remuneration that could be obtained by the Portuguese transmission provider using Short Term Marginal Prices. This paper describes the main principles behind the regulation of the transmission sector in force in Portugal, details the model used to compute the nodal marginal prices in the transmission network, presents a comprehensive set of results for some scenarios in which the year was organized as well as the estimate of the referred remuneration. The data of the scenarios that were used is publicly available in [l] and we adopted typical values for generation costs of different thermal plants. At the end, the paper includes some conclusions as well as some ideas of hture work aiming at improving the quality of the estimate of the marginal based remuneration. © 2001 IEEE.

Abstract
In the scope of the reregulation process of the electric sector, both competitive pool markets and contract mechanisms at the generation and commercialization levels have been emerging. At the wholesale level, and apart from Pool structures and Bilateral Contracts, there are hybrid models in which these two types of structures coexist. In any case, the dispatch coming from the Pool Market Operator, prepared according to the buying and selling offers, together with the bilateral contracted powers must be analyzed from a technical point of view by an independent entity - System Operator. The System Operator aims at checking if the scheduled injected powers do not lead to a decrease of the security standards of the system. Taking in account this concern, in this paper we describe several models to perform the technical validation of sets of electricity schedules, namely trying to minimize the financial impact of the required changes on pre-scheduled generations and loads. This objective is modelled in terms of maximizing the satisfaction degree felt by the participants in the market. The developed application uses Simulated Annealing to solve the corresponding optimization problems. In Section IV of this paper we will include results obtained from several simulations in order to illustrate and demonstrate the interest of the referred models. © 2001 IEEE.

Abstract
In this paper we present a Monte Carlo based application to evaluate estimates of nodal marginal prices leading to target prices of transmission congestion contracts. The application integrates an optimization model to evaluate nodal marginal prices for each sampled state including an estimate of transmission losses. This formulation is integrated in a Monte Carlo simulation in order to deal with the probabilistic nature of component outages and to allow the user to represent load behavior using Load Duration Curves. The computational performance of the Monte Carlo simulation is enhanced by adopting a variance reduction acceleration technique based on a regression function. At a final section the paper includes results from a case study to illustrate the application of the model and to evaluate the efficiency of the referred acceleration technique. © 2001 IEEE.

Abstract
This paper presents a mathematical formulation for the active/reactive dispatch in electricity markets, recognizing that the typical sequential activities organized in terms of pool markets and the dispatch of ancillary services may lead to economic inefficiencies or technical difficulties. The developed model admits that it is known the purely economic pool dispatch and then it aims at dispatching reactive resources considering voltage and branch limit constraints and constraints reflecting the alternator capability curve. We also admitted that some constraints have a soft nature and used a symmetrical fuzzy decision formulation to model this aspect within an SLP based algorithm. Finally, the paper includes a case study based on the IEEE 24 bus/38 branch system to illustrate the results obtained with the developed approach. © Copyright KTH 2006.

Abstract
This paper presents the mathematical models and the solution algorithms of DC optimal power flow problems: considering uncertainties represented by fuzzy numbers affecting loads as well as the elements of the cost function. The main purpose of this work corresponds to transfer the uncertainties affecting both the loads and the cost vector to the results that one usually obtain with such a DC optimal power flow model, that is, to characterize the uncertainties that affect the generations, the voltage phases, the branch flows. Apart from that, this paper also describes the algorithm to be used to calculate the uncertainties affecting the nodal marginal prices, since these prices are related with the dual variables of several constraints in the optimization problem. The developed algorithms are based in the solution of multiparametric problems in which one considers parameters both in the right hand side vector of the constraints (in order to represent load uncertainties) and in the cost function (to consider uncertainties in fuel costs, for instance). Finally, the paper includes a results of a Case Study designed to illustrate the application of the developed algorithms as well as results obtained for the IEEE 24 bus test system.

Abstract
This paper describes the models that were used and the results obtained to estimate the Congestion Cost of the Portuguese National Transmission Network. This network is established at 400 / 220 and 150 kV and the Tariff Code in force is Portugal determines the use of a postage stamp based approach discriminated by voltage level to set the tariffs for the use of the transmission system. However, the value of the congestion cost and its percentage regarding the regulated revenue of the transmission activity set by the Regulatory Agency are good indicators of the quality of the network since they directly reflect problems in the network in terms of congested branches or larger transmission losses. In this sense, we have been computing this indicator since 1998 and this paper reports the conclusions that were recently obtained using data from 2006 and 2008.