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Artículos en revistas It is shown how a standard nonlinear programming approach can be applied to solve a sophisticated version of the static optimal mix problem in generation planning. The model presented includes technical minima of thermal capacity, detailed operating models of storage-hydro and pumped-hydro units, a realistic model of capital costs for hydro plants, operating reserve and minimum demand constraints, and capacity already in existence. The model formulation is in a format that can be directly handled by the well-known MINOS code and can be efficiently solved. The use of a general-purpose nonlinear optimization program results in a great flexibility, making it possible to modify the model formulation easily or to adapt it to the characteristics of a particular electric system. A realistic application to the Spanish generation system is presented info:eu-repo/semantics/publishedVersion

Capítulos en libros This paper describes a strategic information platform developed for the German electric utility Eon, to provide historical bidding analysis and medium-term forecasting of the Iberian Electricity Market. This platform, PLAMER, has three main modules: Initialization module, consisting of different sub-modules to define the electrical system structure and to organize the input data of the rest of modules, PLAMER-bids, to read, aggregate and visualize market historical bids and also to prepare them for their future forecasted values, and PLAMER-clearing, for market clearing emulation using forecasted bids. PLAMER-clearing models the Iberian market based on a bid clearing mechanism with an inherent market splitting procedure. This market splitting is built with a bi-nodal simplification, one node representing the Spanish System and the other the Portuguese one. Both are simply connected by a unique equivalent interconnection line. The medium term clearing model uses a generation portfolio per generation company in terms of technologies, for supplying monthly demand for different load levels, and labour and non-labour periods. Some technical constraints, such as minimum outputs and pumping energy balance, are also taking into account. The mathematical problem of PLAMER-clearing is a quadratic programming model solved using GAMS language and CPLEX optimizer. Finally, a real Iberian case study is detailed and some market splitting outputs are analyzed. info:eu-repo/semantics/publishedVersion

Artículos en revistas There has been total unanimity about the vital importance of reliability of supply since the beginning of the electricity sector deregulation process. This paper describes the procedure proposed by Pérez-Arriaga et al. [2005. White paper for the reform of the regulatory scheme of the power generation in Spain. For the Ministry of Industry, Tourism and Trade of Spain (in Spanish)] to improve upon the current scheme to guarantee a reasonable reserve margin, the capacity payment mechanism. This alternative design introduces improvements aimed at guaranteeing at least a minimum capacity reserve margin, as well as at providing a strong incentive for generating units to be available when needed, namely, in situations when supply is likely to be insufficient to meet the total demand. info:eu-repo/semantics/publishedVersion

This paper proposes a linear programming problem to find the optimal planning and operation of aggregated distributed energy resources (DER), managed by an aggregator that participates in the day-ahead wholesale electricity market as a price-maker agent. The proposed model analyzes the impact of the size of the aggregated resources and gives the optimal planning and management of DER systems, and the corresponding energy transactions in the wholesale day-ahead market. The results suggest that when the aggregated resources are large enough, DER systems can achieve up to 32% extra economic benefits depending on the market share, compared with a business-as-usual approach (not implementing DER systems). info:eu-repo/semantics/draft

Capítulos en libros The importance of the natural gas sector in the electric power industry has increased substantially over the last decades, reaching 21% generation capacity in Europe in 2016. Generation companies that own gas fired units (GFUs), such us combined cycle gas turbines, have to take into account not only the fuel and the operation and maintenance costs, but also the costs related to the third-party access (TPA) tariffs to the gas network as any other gas consumer. This paper highlights the importance of modeling these TPA tariffs in a proper manner as they represent a significant share of the total operation cost of GFU. In addition, the fact that TPA final costs depend on the daily gas consumption for the whole month, makes traditional short-term unit-commitment (UC) models unable to capture the impact of the new complicating constraints. This paper presents the mathematical formulation of a UC model that models the TPA tariffs to the gas network in a more realistic manner where a joint assessment is formulated for all the units that withdraw gas from the same node of the gas network. The paper includes an example case that illustrates the impact on the optimal hourly scheduling of such detailed modeling, and it compares the results with the standard formulation based on individual cost functions of each thermal unit. info:eu-repo/semantics/publishedVersion

The aim of this report is to demonstrate and evaluate the potential of tall wheatgrass (Elytrigia elongata) to avoid GHG emissions and obtain lower economic costs in marginal areas of Spain. Our research built scenarios based on experimental plots (2 and 3 years growth) in 3 locations of Spain with completely different climate conditions (provinces of Girona, Soria and Palencia). In our experiences, we achieved an adequate establishment and biomass production, and assumed a rank of biomass yields until the end of the life cycle that is usually accepted to be about 15 years in many other studies in United States, Argentina and Eastern Europe where tall wheatgrass is extensively cultivated in marginal areas for sheep livestock production. Using our experimental plots and statistical information for economic inputs costs, we built 5 different scenarios per region considering a large range of biomass yields of tall wheatgrass. The analysis included a comparison with annual grasses economic costs calculated for a wide range of biomass yields of a previous study. We estimated GHG emissions savings for tall wheatgrasses and used our previous study (which had GHG emissions savings as well). Savings were calculated replacing natural gas electricity with electricity from biomass combustion in real power plants in Spain. In a wide range of yields, the results suggest that marginal areas might present a better performance with tall wheatgrass compared to annual winter grasses (cereals whole plant cuttings), thus producing biomass yields with higher GHG savings and lower economic costs at the farm level. Proceedings of the 20th European Biomass Conference and Exhibition, 18-22 June 2012, Milan, Italy, pp. 217-229

Artículos en revistas Multi-terminal High Voltage Direct Current (HVDC) using Voltage Source Converters (VSC-HVDC) is a promising technology which provides flexible control of active and reactive power and facilitates remote renewable energy integration, above all using long cables. This paper analyses an active power control strategy for multi-terminal VSC-HVDC systems tailored to enhance transient stability of hybrid AC/DC grids. The proposed strategy controls each VSC using frequency measurements of all terminals. Its performance is compared to a strategy in which each VSC is controlled using only local frequency measurements of the AC side, proving that the proposed strategy shows better performance, even taking into account reasonable communication delays. The paper also shows that the proposed strategy generally gives similar results to those obtained when each VSC is controlled using the speed of the centre of inertia (COI). The speed of the COI is a more comprehensive and richer figure than the one proposed in this paper but it is also much more complex to obtain. Simulation results with PSS/E of a test system have been used to illustrate the comparisons and the main contributions of the proposal. info:eu-repo/semantics/publishedVersion

Capítulos en libros This paper presents a method for calculation of stationary Power Quality Disturbances-PQD based on measurements, distribution system modeling and Monte Carlo techniques. A method to simulate PQD with specific random behavior based on Perfect Sampling is proposed. Three non-sinusoidal conditions power quantities are employed to illustrate the proposed methodology, and a proposal for statistical interpretation of simulated results is presented as well. info:eu-repo/semantics/publishedVersion