J.I. de la Fuente

Auction Design in Day-Ahead Electricity Markets

Competition in day-ahead electricity markets has been established through auctions where generators and loads bid prices and quantities. Different approaches have been discussed regarding the market auction design. Multiround auctions, despite their implementation complexity, allow market participants to adapt their successive bids to market prices considering their operational and economic constraints. However, most of the day-ahead electricity market implementations use noniterative single-round auctions. This paper presents a market simulator to compare both auction models. Different auction alternatives-such as the Spanish single-round auction that takes into account special conditions included in the generator bids and multiround auctions with different stopping rules-are analyzed. The results and acquired experience in the simulation of the Spanish market, started in January 1998, are presented. Hourly market prices; average daily price; price/demand correlation; and several economic efficiency indicators, such as generator surplus, consumer surplus, and social welfare, are compared to derive conclusions regarding the performance of the auction altematives.

New design for the Spanish AGC scheme using an adaptive gain controller

This paper investigates the application of adaptive control to the Spanish load-frequency regulation scheme, Automatic Generation Control (AGC). The Spanish AGC system regulates the frequency and the power exchange between France and Spain. The system is hierarchically structured with one master regulator that coordinates four control areas. Each control area is composed of several generating units providing AGC service. Coordinating signals are sent to the control areas so that the global system response achieves the objective established by the System Operator. The participation of each control area in the service is set according to the rated share that it has obtained in the secondary-reserve market and its relative response speed compared to that of the rest of the control areas. Some problems, such as the lack of sensitivity to the quality of the reserve provided by the control areas, have been detected in the operation of the current AGC scheme. A new design, which is presented in this paper, has been developed in order to overcome these problems. This paper attempts to outline how this new design improves the global AGC system response and the distribution of the regulation effort among the control areas. The proposed strategy is compared with the present design by means of simulation.

Building generation supply curves under uncertainty in residual demand curves for the day-ahead electricity market

The restructuring process that took place in the Spanish electricity market in 1998 has caused the appearance of new procedures and rules, and the implementation of decentralized operation models. Under this new competitive framework, utilities pursue supply strategies to maximize their benefits. This paper proposes a stochastic building model of competitive supply curves under uncertainty, whose objective is to maximize the expected profit of a generation utility in the day-ahead market of a deregulated electrical system. The model contemplates the global strategy of the utility, but also it specifies the bid for each generation unit. At the same time the model has a great flexibility characterizing different market conditions. Firstly, the formulation and the restrictions of the iterative optimization problem are described. Afterwards, a brief review of the model algorithm, based on successive optimizations for different scenarios, is shown. Next the building up procedure of the bidding supply curves is explained. Finally, a case study is presented that allows the validity of the proposed model to be checked.

Decentralized Secondary Voltage Control and Pilot Bus Selection

Abstract The aim of the secondary voltage control is to maintain voltage magnitudes of several load buses, which have been selected as pilot buses, at their optimal values imposed by the tertiary voltage control. In this paper a comprehensive formulation of the secondary voltage control is presented. Centralized control matrices for an optimal proportional integral control are obtained by the minimization of a performance index. Conditions to achieve a stable closed-loop in a decentralized control scheme are stated. A systematic methodology for selecting pilot buses and for dividing the system in decentralized control areas is presented. The differences between centralized and decentralized control schemes are analyzed in a case study based on the New England 39 bus system.

Improvements for the short-term bidding process of a GENCO

This paper presents a new dispatch optimization model and different bidding strategies that an agent can adopt for the day-ahead electricity market, provided adequate forecasts of its residual demand curves (RDCs) by means of ARIMA models. In the case study analyzed the resulting spot price and the total amount of energy delivered by the utility are related (in fact this relationship is measured through the slope of the RDCs), so the commonly used price-taker approach may not be always suitable. This dependence between the resulting spot price and the amount of power delivered by the agent makes the problem much more difficult to solve, as the objective function turns out to be non-linear. Also, the fact that there are groups not totally owned by a single utility, as is the case in the Spanish system, must be considered in the dispatch optimization model. Next, two different bidding strategies (profit-seeking and share-seeking) and the implications about considering or not a global share constraint in the dispatch model are shown. Finally, a case study is presented in order to clarify the previous ideas.

Load-frequency regulation using an adaptive predictive control

This paper investigates the application of an adaptive-predictive control to the load-frequency regulation of the Spanish power system. The control system regulates the frequency and the power exchange with France at the power-inter-tie. The control signal distributed among the control areas is calculated so that the generated power reaches the desired power at the end of the prediction horizon. The regulation effort distribution among the control areas is established according to their relative dynamic response speed and their rated share obtained in the load-frequency market. The proposed strategy is compared with the present design by means of simulation.