Download or read book Impact of Transmission on Strategic Behaviour in Electricity Markets written by Anthony Downward and published by . This book was released on 2011 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, we investigate the impact of transmission on the strategic behaviour of firms competing in deregulated electricity wholesale markets. Assuming uniform-price auctions and locational marginal pricing, we first investigate the properties of the dispatch problem over networks that are constrained and/or lossy. Without loops and losses we derive important results as to how price varies as a function of demand at each node. Whereas, for networks with loops and losses, we discuss the non-convexity of the dispatch problem and show that the optimal value function may be non-convex. We model the strategic firms as Cournot agents, and discuss how the assumptions surrounding the rationality of the agents can influence the equilibrium outcomes. Under a full-rationality assumption, we prove that over a lossless radial network, with firms owning single generators, the line capacities ensuring that a single-node Cournot equilibrium exists form a convex set. However, in the case of networks with loops or with firms owning multiple generators we provide counterexamples to this convexity. We investigate the prices coming from a two-node network with a lossy line and find the conditions such that a generator is guaranteed to have a quasi-concave revenue function. We use this result to prove that there exists a pure-strategy equilibrium for a Cournot game over the same network. In the final chapters we present some applications of this work. We first define a mixed-integer stochastic transmission planning model that uses the set of capacities derived earlier as constraints to ensure that the unconstrained equilibrium exists for all periods. Finally, we examine the effect of carbon charges over a two-node network and find that the imposition of a carbon charge may increase emissions when firms behave strategically over a constrained network.

Download or read book Network and Temporal Effects on Strategic Bidding in Electricity Markets written by Youfei Liu and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Network and Temporal Effects on Strategic Bidding in Electricity Markets" by Youfei, Liu, 劉有飛, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: of thesis entitled "Network And Temporal Effects On Strategic Bidding In Electricity Markets" Submitted by Youfei Liu for the Degree of Doctor of Philosophy at the University of Hong Kong in February 2006 The global deregulation of power industries has given rise to many fascinating research topics. This thesis addresses issues of strategic bidding by power generators. The problem of strategic bidding is to optimize an individual power generation bid by maximizing profits, based on production cost, expectation of rival behavior and system demand. Electrical power flow over different links is governed by the physical law (Kirchhoff law). As a result, electrical power flow cannot be independently determined and the electricity transmission system has global network effects. One major contribution of this study is to investigate the network effects of electricity transmission on strategic bidding and analyze the network-constrained electricity market equilibria. A three-node electricity system is used for investigation. The decision space of generators is divided into the congestion-on region and congestion-off region, and the optimal response curves of generators in each region are then derived. The market equilibrium is located as the intersection of these optimal response curves. It is analytically shown that this may consist either of a unique unconstrained market equilibrium, a unique constrained market equilibrium, multiple-equilibria, or no pure Nash equilibrium. Subsequently, the interaction between transmission rights holding and market power exercising is addressed. It is shown that in the situation with a positive PTDF, holding transmission rights mitigate market power, and produce an improvement in market efficiency, while in other situations, the reverse is true. Furthermore it is demonstrated that a possible allocation of transmission rights to generators can be found to achieve maximum efficiency. Another unique characteristic of electricity markets is their notable temporal ii effects. In other words, electricity prices have significant volatilities because of the non-storability of power energy and the large variations of system demand. The second part of this study investigates the temporal effects of the electricity market on strategic bidding. A periodic dynamic feedback system is proposed to model the generation competition process. With the developed system dynamics, an optimal control problem is formulated to study the multi-period optimization behavior (called the 'advanced' strategy) of a generator, and the state-feedback control rule is then derived via a sweeping method. It is demonstrated that the generator with optimal control can obtain more profits, and a sensitivity analysis is provided to locate the market factors that affect the performance of optimal control. Next, system uncertainties are included, and a stochastic optimal control problem for generation decision is formulated and solved. Two interesting problems are investigated, namely the effect of the generator's 'advanced' strategic behavior on market efficiency, and the way in which an individual's payoff evolves with other generators' 'advanced' strategic behavior. It is shown that the 'advanced' strategic behavior of generators will improve market efficiency, while an individual's payoff evolution resembles a 'Prisoner Dilemma'. An analysis of risk management of generation decisi...

Download or read book Analyzing Strategic Behaviors in Electricity Markets Via Transmission constrained Residual Demand written by Lin Xu (Ph. D.) and published by . This book was released on 2009 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation studies how to characterize strategic behaviors in electricity markets from a transmission-constrained residual demand perspective. This dissertation generalizes the residual demand concept, widely used by economists in general markets, to electricity markets, which are constrained by transmission networks. The transmission-constrained residual demand is characterized by a sensitivity analysis of the optimal power flow program, which is the electricity market clearing engine. Methods are proposed to optimize a generator or generation firm's profit utilizing the residual demand sensitivity information, which has several advantages over existing methods. The transmission-constrained residual demand concept and the methods are helpful for market participants to develop bidding strategies and for market monitors to analyze market power in electricity markets.

Download or read book Alternative Models to Analyze Market Power and Financial Transmission Rights in Electricity Markets electronic Resource written by Bautista Alderete, Guillermo and published by University of Waterloo. This book was released on 2005 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the main concerns with the introduction of competition in the power sector is the strategic behaviour of market participants. Computable models of strategic behaviour are becoming increasingly important to understand the complexities of competition. Such models can help analyze market designs and regulatory policies. In this thesis, further developments on the modelling and analysis of strategic behaviour in electricity markets are presented. This thesis work has been conducted along three research lines. In the first research line, an oligopolistic model of a joint energy and spinning reserve market is formulated to analyze imperfect competition. Strategic behaviour is introduced by means of conjectured functions. With this integrated formulation for imperfect competition, the opportunity cost between generation and spinning reserve has been analytically derived. Besides, inter-temporal and energy constraints, and financial transmission rights are taken into account. Under such considerations, competition in electricity markets is modelled with more realism. The oligopolistic model is formulated as an equilibrium problem in terms of complementarity conditions. In the second research line, a methodology to screen and mitigate the potential exacerbation of market power due to the ownership of financial transmission rights is presented. Hedging position ratios are computed to quantify the hedging level of financial transmission rights. They are based on the actual impact that each participant has in the energy market, and on the potential impact that it would have with the ownership of financial transmission rights. Thus, hedging position ratios are used to identify the potential gambling positions from the transmission rights bidders, and, therefore, used to prioritize critical positions in the auction for transmission rights. In the last research line, alternative equilibrium models of markets for financial transmission rights are formulated. The proposed equilibrium framework is more natural and flexible for modelling markets than the classic cost-minimization markets. Different markets for financial transmission rights are modelled, namely: i) forwards, ii) options, and iii) joint forwards and options. Moreover, one-period, multi-period and multi-round markets for forwards are derived. These equilibrium models are proposed to analyze the bidding strategies of market participants. The potential impact of bidders on congestion prices is modelled by means of conjectured transmission price functions.

Download or read book Financial Transmission Rights written by Juan Rosellón and published by Springer Science & Business Media. This book was released on 2013-03-15 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: Whilst financial rights have appeared as a successful ingredient in North-American power markets, they have their shortcomings both theoretically and in practice. Financial Transmission Rights: Analysis, Experiences and Prospects present a systematic and comprehensive overview of financial transmission rights (FTRS). Following a general introduction to FTRs, including chapters to explain transmission pricing and the general properties of FTRS, experts in the field provide discussions on wide scope of topics. These include: Varying perspectives on FTRS: from electrical engineers to economists, Different mathematical formulations of FTRS Financial Hedging using FTRS, and Alternative solutions to FTRs The detail, expertise and range of content makes Financial Transmission Rights: Analysis, Experiences and Prospect an essential resource for electricity market specialists both at academic and professional levels. “This is THE BOOK we were all expecting to address all key ‘Financial Transmission Rights’ issues. It is comprehensive and reader friendly. You can pick at will in its menu: more or less theory, a bit of maths or none, empirical review of real cases or numerical simulations of many feasible options. Big names rally there to delight you like: Hogan , Oren, Perez-Arriaga, Smeers, Hobbs and... Rosellón. More than a must read: a light house, a map and a survival kit.” Jean – Michel Glachant, Director Florence School, Holder Loyola de Palacio Chair, Chief-editor Economics of Energy & Environmental Policy. "In the last two decades, economists have developed a better understanding of the impact of financial rights on risk management, market power and network expansion in electricity markets, while power systems have experimented with such rights. Striking a good balance between academics and practitioners, always at the frontier of the field, written by the best experts, this volume is essential reading for all those- power systems’ managers and users, regulators, students and researchers- who want to understand the new electricity environment and predict its evolution." Jean Tirole, Toulouse School of Economics and Institute for Industrial Economics (IDEI) Further comments inside.

Download or read book The Competitive Effects of Transmission Capacity in a Deregulated Electricity Industry written by Severin Borenstein and published by . This book was released on 1997 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an unregulated electricity generation market, the degree to which generators in" different locations compete with one another depends on the capacity to transmit electricity" between the locations. We study the impact of transmission capacity on competition among" generators. We show that there may be no relationship between the effect of a transmission line" in spurring competition and the actual electricity that flows on the line. We then investigate the" equilibria that are likely to result as transmission lines between previously unconnected locations" are built and expanded. We demonstrate that limited transmission capacity can give a firm the" incentive to restrict its output in order to congest transmission into its area of dominance. This" analysis is applied to a model of California's forthcoming deregulated electricity market. Our" results indicate that at least one firm could have an incentive to strategically induce transmission" congestion and that relatively small investments in transmission may yield surprisingly large" payoffs in terms of increased competition.

Download or read book National Audit Office NAO Cross Government Infrastructure Investment The Impact on Consumer Bills Volume II HC 812 II written by Great Britain: National Audit Office and published by The Stationery Office. This book was released on 2013-11-13 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Government and regulators do not know by how much overall expected new investment by the private sector in infrastructure will increase household utility bills and whether bills will be affordable. The National Audit Office has recommended that the Treasury ensure there are mechanisms to assess the cumulative impact of infrastructure investment on consumer bills. This report, which focuses on the energy, water and, to a lesser extent, telecoms sectors, recognizes that the UK requires significant investment in new infrastructure. The Treasury expects that over two-thirds of the £310 billion worth of the planned infrastructure it has identified will be privately financed, owned and operated but paid for by consumers through their utility bills. High levels of expected new investment in infrastructure mean that energy and water bills may rise significantly from current levels. The available projections suggest that increases in both energy and water bills will continue to outstrip inflation, on average, up to 2030. This is particularly concerning, given that energy and water bills have increased significantly in recent years, while incomes have not. The affordability of utility bills can be assessed only in the context of wider pressures on household expenditure, including an understanding of all household bills as well as potential trends in household incomes. There is a range of schemes to support vulnerable consumers but without a fuller understanding of affordability in the round, government and regulators cannot assess the adequacy of these schemes, now or in the future

Download or read book Electricity Markets written by Jeremy Lin and published by . This book was released on 2017 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: 10.2.3 Generation Resources -- 10.2.4 Market Efficiency -- 10.2.5 Interregional Coordination -- 10.2.6 Operational Performance -- 10.2.7 Public Policy -- 10.2.8 Other Drivers -- 10.3 Reliability-Based Transmission Planning -- 10.3.1 Establishing a Reference System -- 10.3.2 Reliability Analysis of a Reference System -- 10.3.3 Near-Term Reliability Review -- 10.3.4 Long-Term Reliability Review -- 10.4 Market-Based Transmission Planning -- 10.4.1 Market Efficiency Model -- 10.4.2 Model Benchmarking -- 10.4.3 Market Efficiency Analysis -- 10.4.4 System Economic Output -- 10.4.5 Various Definitions of Economic Benefits -- 10.4.6 Economic Criteria -- 10.5 Cross-Border Transmission Planning -- 10.5.1 Reliability -- 10.5.2 Economics -- 10.5.3 Methodology for Cross-Border Transmission Planning -- 10.6 Competitive Transmission Planning -- 10.6.1 Regulated Transmission Business -- 10.6.2 FERC Order 1000 -- 10.6.3 Competitive Bidding Process -- 10.7 Transmission Planning in Europe -- 10.8 Further Discussions -- Further Reading -- 11 Electricity Market under a Future Grid -- 11.1 Renewable Energy Technologies -- 11.1.1 Types of Renewable Energy Sources -- 11.1.2 Growth Drivers of Renewable Energy Sources -- 11.1.3 The Impact of Renewable Energy on Electricity Markets -- 11.2 Smart Grid -- 11.2.1 Microgrid -- 11.2.2 Active Demand Response -- 11.2.3 Impact of Active Demand Response -- 11.2.4 Energy Storage Systems -- 11.2.5 Electric Vehicles -- 11.2.6 Smart Meters -- 11.2.7 Electricity Market at Distribution System Level -- 11.2.8 Smart Grid Policies and Programs -- 11.2.9 Market Implementation -- 11.3 Final Thoughts -- Further Reading -- Index -- EULA

Download or read book Managing Unilateral Market Power in Electricity written by Frank A. Wolak and published by World Bank Publications. This book was released on 2005 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This paper first describes those features of the electricity supply industry that make a prospective market monitoring process essential to a well-functioning wholesale market. Some of these features are shared with the securities industry, although the technology of electricity production and delivery make a reliable transmission network a necessary condition for an efficient wholesale market. These features of the electricity supply industry also make antitrust or competition law alone an inadequate foundation for an electricity market monitoring process.

Download or read book Essays on Empirical Analysis of Multi unit Auctions Impacts of Financial Transmission Rights on the Restructured Electricity Industry written by Hailing Zang and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation uses recently developed empirical methodologies for the study of multi-unit auctions to test the impacts of Financial Transmission Rights (FTRs) on the competitiveness of restructured electricity markets. FTRs are a special type of financial option that hedge against volatility in the cost of transporting electricity over the grid. Policy makers seek to use the prices of FTRs as market signals to incentivize efficient investment and utilization of transmission capacity. However, prices will not send the correct signals if market participants strategically use FTRs. This dissertation uses data from the Texas electricity market to test whether the prices of FTRs are efficient to achieve such goals. The auctions studied are multiunit, uniform-price, sealed-bid auctions. The first part of the dissertation studies the auctions on the spot market of the wholesale electricity industry. I derive structural empirical models to test theoretical predictions as to whether bidders fully internalize the effect of FTRs on profits into their bidding decisions. I find that bidders are learning as to how to optimally bid above marginal cost for their inframarginal capacities. The bidders also learn to bid to include FTRs into their profit maximization problem during the course of the first year. But starting from the second year, they deviated from optimal bidding that includes FTRs in the profit maximization problems. Counterfactual analysis show that the primary effect of FTRs on market outcomes is changing the level of prices rather than production efficiency. Finally, I find that in most months, the current allocations of FTRs are statistically equivalent to the optimal allocations. The second part of the dissertation studies the bidding behavior in the FTR auctions. I find that FTRs' strategic impact on the FTR purchasing behavior is significant for large bidders - firms exercising market power in the FTR auctions. Second, trader forecasts future FTR credit very accurately while large generators' forecasts of future FTR credit tends to be biased upward. Finally, The bid shading patterns are consistent with theoretical predictions and support the existence of common values.

Download or read book The Effect of the Transmission Grid on Market Power written by and published by . This book was released on 1997 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: If competition could extend without hindrance through the entire extent of an electrically connected power grid, the US would have just two electricity markets, each with a uniform price. These markets would be competitive indeed. Unfortunately, losses and congestion present barriers to competition and thereby provide the likelihood of significantly increased market power. This paper begins the analysis of congestion as it affects the physical extent of markets and thereby affects the degree of market power. This is new territory; very little has previously been written in this area. Although the theoretical developments reported here rely on complex economic analysis, and although the market behaviors described are extremely subtle, several broad generalizations relevant to policy analysis can be made. From these generalizations one major policy conclusion can be drawn: In an unregulated market it will be socially beneficial to build a grid that is more robust than what is optimal in a regulated environment. Unused capacity may be needed. For a line to support full competition it may need to have a capacity that is much greater than the flow that will take place on it under full competition. Markets do not have sharp boundaries. Even with only one line the two busses may be in different regions, the same region, or partially in each other's region. Increasing capacity is more effective on a small line. If connecting two busses with a very strong line will reduce market power, then the first MW of connecting capacity will have the most impact and each additional MW will have less. A congested line will cut a market into two non-competing regions. In each region the generators will markup according to the elasticity of the demand in only their region. A generator may reduce output in order to congest a line and increase its market power.

Download or read book From Regulation to Competition New frontiers in electricity markets written by Michael A. Einhorn and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electric utilities throughout the world continue to face new challenges involving ownership, market structure, and regulation. There are three related issues at hand. First, should ownership be private or public? Second, what operations should be integrated and where is competition feasible? Third, where is regulation necessary and can it be made more efficient? This volume bears directly upon these concerns. The book contains two sections. The first six articles discuss the British electricity experiment that has privatized and disintegrated the nation's generation, transmission, and distribution companies, introduced market competition for power purchases, and implemented incentive regulation for monopolized transmission and distribution grids. The remaining articles focus on the theater in which significant microeconomic issues will continue to emerge, most immediately in the U.K. and U.S.A. -- the coordination and pricing of transmission.

Download or read book Restructured Electric Power Systems written by Xiao-Ping Zhang and published by John Wiley & Sons. This book was released on 2010-10-15 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: The latest practical applications of electricity market equilibrium models in analyzing electricity markets Electricity market deregulation is driving the power energy production from a monopolistic structure into a competitive market environment. The development of electricity markets has necessitated the need to analyze market behavior and power. Restructured Electric Power Systems reviews the latest developments in electricity market equilibrium models and discusses the application of such models in the practical analysis and assessment of electricity markets. Drawing upon the extensive involvement in the research and industrial development of the leading experts in the subject area, the book starts by explaining the current developments of electrical power systems towards smart grids and then relates the operation and control technologies to the aspects in electricity markets. It explores: The problems of electricity market behavior and market power Mathematical programs with equilibrium constraints (MPEC) and equilibrium problems with equilibrium constraints (EPEC) Tools and techniques for solving the electricity market equilibrium problems Various electricity market equilibrium models State-of-the-art techniques for computing the electricity market equilibrium problems The application of electricity market equilibrium models in assessing the economic benefits of transmission expansions for market environments, forward and spot markets, short-term power system security, and analysis of reactive power impact Also featured are computational resources to allow readers to develop algorithms on their own, as well as future research directions in modeling and computational techniques in electricity market analysis. Restructured Electric Power Systems is an invaluable reference for electrical engineers and power system economists from power utilities and for professors, postgraduate students, and undergraduate students in electrical power engineering, as well as those responsible for the design, engineering, research, and development of competitive electricity markets and electricity market policy.

Download or read book Restructuring Electric Power Systems written by S K Gupta and published by I K International Pvt Ltd. This book was released on 2018-05-10 with total page 473 pages. Available in PDF, EPUB and Kindle. Book excerpt: Restructuring Electric Power System gives readers a thorough understanding of the technology involved in this very recent advance field. Electricity is a commodity with several features that distinguish it from other goods and services. It cannot be stored and its instant transmission requires a network of wires. A pre-requisite for ensuring orderly transportation of electricity under new regulatory environment is the creation of an independent entity that would channelize and control its flow in an optimum manner and without any discrimination, just as a traffic policeman or air traffic controller does in respect of traffic flowing to and from several directions. This causes several issues which are dealt by this book systematically. This book shall be useful as text/reference to field engineers, undergraduate, postgraduate students and the research scholars working in this field. MATLAB M-files and SIMULINK have been included in some of the numerical examples to assist the analysis. Thus, the book includes topics power flow analysis, Power trading, restructured market, market forces and transmission issues, ATC, congestion management, AGC and ancillary services.

Download or read book Strategic Bidding and Transmission Congestion Management in Deregulated Electricity Market written by Marta Marmiroli and published by . This book was released on 2008 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optimization and Industry New Frontiers written by Panos M. Pardalos and published by Springer Science & Business Media. This book was released on 2013-12-01 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optimization from Human Genes to Cutting Edge Technologies The challenges faced by industry today are so complex that they can only be solved through the help and participation of optimization ex perts. For example, many industries in e-commerce, finance, medicine, and engineering, face several computational challenges due to the mas sive data sets that arise in their applications. Some of the challenges include, extended memory algorithms and data structures, new program ming environments, software systems, cryptographic protocols, storage devices, data compression, mathematical and statistical methods for knowledge mining, and information visualization. With advances in computer and information systems technologies, and many interdisci plinary efforts, many of the "data avalanche challenges" are beginning to be addressed. Optimization is the most crucial component in these efforts. Nowadays, the main task of optimization is to investigate the cutting edge frontiers of these technologies and systems and find the best solutions for their realization. Optimization principles are evident in nature (the perfect optimizer) and appeared early in human history. Did you ever watch how a spider catches a fly or a mosquito? Usually a spider hides at the edge of its net. When a fly or a mosquito hits the net the spider will pick up each line in the net to choose the tense line? Some biologists explain that the line gives the shortest path from the spider to its prey.

Download or read book The Economics of Electricity Markets written by Darryl R. Biggar and published by John Wiley & Sons. This book was released on 2014-07-10 with total page 493 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bridges the knowledge gap between engineering and economics in a complex and evolving deregulated electricity industry, enabling readers to understand, operate, plan and design a modern power system With an accessible and progressive style written in straight-forward language, this book covers everything an engineer or economist needs to know to understand, operate within, plan and design an effective liberalized electricity industry, thus serving as both a useful teaching text and a valuable reference. The book focuses on principles and theory which are independent of any one market design. It outlines where the theory is not implemented in practice, perhaps due to other over-riding concerns. The book covers the basic modelling of electricity markets, including the impact of uncertainty (an integral part of generation investment decisions and transmission cost-benefit analysis). It draws out the parallels to the Nordpool market (an important point of reference for Europe). Written from the perspective of the policy-maker, the first part provides the introductory background knowledge required. This includes an understanding of basic economics concepts such as supply and demand, monopoly, market power and marginal cost. The second part of the book asks how a set of generation, load, and transmission resources should be efficiently operated, and the third part focuses on the generation investment decision. Part 4 addresses the question of the management of risk and Part 5 discusses the question of market power. Any power system must be operated at all times in a manner which can accommodate the next potential contingency. This demands responses by generators and loads on a very short timeframe. Part 6 of the book addresses the question of dispatch in the very short run, introducing the distinction between preventive and corrective actions and why preventive actions are sometimes required. The seventh part deals with pricing issues that arise under a regionally-priced market, such as the Australian NEM. This section introduces the notion of regions and interconnectors and how to formulate constraints for the correct pricing outcomes (the issue of "constraint orientation"). Part 8 addresses the fundamental and difficult issue of efficient transmission investment, and finally Part 9 covers issues that arise in the retail market. Bridges the gap between engineering and economics in electricity, covering both the economics and engineering knowledge needed to accurately understand, plan and develop the electricity market Comprehensive coverage of all the key topics in the economics of electricity markets Covers the latest research and policy issues as well as description of the fundamental concepts and principles that can be applied across all markets globally Numerous worked examples and end-of-chapter problems Companion website holding solutions to problems set out in the book, also the relevant simulation (GAMS) codes