Optimal Bidding Strategies for Generation Companies in Electricity Markets with Transmission Capacity Constraints Taken into Account

In the electricity market environment, how to build optimal bidding strategies has become a major concern for generation companies. The deficiency of transmission capacity could lead to congestion, and as a result, the whole electricity market can then be actually divided into two or more submarkets. A direct consequence of transmission congestion is the change of competitive positions of generation companies concerned in the electricity market, and the optimal bidding strategies of them should accordingly be changed. In this paper, the problem of developing optimal bidding strategies for generation companies is systematically investigated with transmission capacity constraints taken into account. A stochastic optimization model is first formulated under the presumption that the bidding behaviors of rival generation companies could be modeled as normal probability distributions. An approach is next presented for solving the optimization problem using the well-known Monte Carlo simulation method and the genetic algorithm. Finally, a simple sample example and the modified IEEE 14-bus system are employed to illustrate the essential features of the proposed model and method.published_or_final_versio

Development of bidding strategies in electricity markets using possibility theory

In the electricity market environment, bidding strategies employed by generation companies may have significant impacts on their own benefits, and on the operating behaviors of an electricity market as well. Hence, how to develop optimal bidding strategies for generation companies or how to analyze strategic behaviors of them and hence to figure out the potential market power abuse is now a very active research area. A possibility theory based approach is proposed in this work for building optimal bidding strategies for generation companies. Based on historical bidding data, the available (production cost) data before the power industry restructuring and experts' heuristic knowledge, the well-known fuzzy set theory is employed to represent the estimated bidding behaviors of rival generation companies, and a fuzzy programming model is developed and a solution method follows. The approach is especially suitable for those electricity markets recently launched, since sufficient historical bidding data is not available and hence probability methods cannot be employed. Finally, a sample example with six generation companies participating in an electricity market is served for demonstrating the essential features of the presented approach.published_or_final_versio

Review of Transmission Fixed Costs Allocation Methods

In the context of competitive electricity markets, transmission fixed costs should be fairly allocated to transmission users. A reasonable allocation method could lead to efficient utilizations of existing transmission facilities and, at the same time, provide economic signals for guiding future generation planning and load sitting. In this paper, a comprehensive literature survey is made on available methods of transmission fixed cost allocations. The review is conducted from several different aspects including: costs to be allocated, entities to pay the costs, system states to be based on, cost allocations of unused capacities, pricing of counter flow and that of reactive power, and allocation principles and methods. In addition, the characteristics of each method are analyzed and compared with those of the others.published_or_final_versio

The concept and algorithm of 'conductor renting' and its application in transmission losses allocation

The cost of transmission losses represents an important part of transmission costs. In the context of competitive electricity marketplace, the costs caused by transmission losses should be reasonably allocated to various market participants, but the nonlinearity of the transmission losses function makes the allocation very difficult. In this paper, the concept of 'conductor renting' is proposed for the first time and is used to solve transmission losses allocation problem. The analysis indicates that the active power losses caused by different current components are in proportion to the conductor section acreage and the corresponding conductance used by the current components, and the reactive power losses caused by current components have similar characteristics. Based on the concept of conductor renting, it is easy to solve the losses allocation problem, and the interaction effect of the transactions is eliminated.published_or_final_versio

A Practical Method For Determining Transmission Usage-based Tariff In Electricity Markets With Trading Modes

In this paper, a practical approach is presented for determining transmission usage-based tariff, based on the well-known generation shift distribution factor (GSDF) based method and the recently developed power flow tracing method. First, the GSDF based method is employed for allocating the transmission usage-based charges among various transactions, and then the power flow tracing technique used for further distributing the charge such obtained among the participants of each transaction concerned. The proposed method is easy to implement and is applicable to electricity markets with various trading modes such as bilateral, multilateral and pool trading modes, and to interconnected multiple-regional and hierarchical electricity markets as well.published_or_final_versio

A Theoretical Framework for Cost Allocations in a Monopoly System with Application to the Allocation of Transmission Losses

In this paper, fundamental characteristics of a general monopolistic service system with a simple structure are first investigated, and a theoretical framework for allocations of common costs is then developed. The concepts of "fairness" and "rationality" are characterized mathematically for the general cost allocation problem. Under the proposed framework, several available allocation methods of transmission losses could be well unified.published_or_final_versio

A Possibility Theory Based Approach for Building Optimal Bidding Strategies in Electricity Markets

In the electricity market environment, bidding strategies employed by generation companies may have significant impacts on their own benefits, and on the operating behaviors of an electricity market as well. Hence, how to develop optimal bidding strategies for generation companies or how to analyze strategic behaviors of them and hence to figure out the potential market power abuse is now a very active research area. A possibility theory based approach is proposed in this work for building optimal bidding strategies for generation companies. Based on historical bidding data, the available (production cost) data before the power industry restructuring and experts’ heuristic knowledge, the well known fuzzy set theory is employed to represent the estimated bidding behaviors of rival generation companies, and a fuzzy programming model is next developed and a solving method followed. The approach is especially suitable for those electricity markets recently launched, since sufficient historical bidding data is not available and hence probability methods cannot be employed. Finally, a sample example with 6 generation companies participating in an electricity market is served for demonstrating the essential features of the presented approach. 在電力市場環境下 ,發電公司采用的報價策略對其自身的獲利、甚至市場總體的運行行為都可能有相當大的影響。因而 ,研究發電公司應該如何構造最優的報價策略或分析電力市場中發電公司的策略性行為 ,進而考察潛在的市場勢力的嚴重程度 ,是目前相當活躍的一個研究領域。提出了一種基于可能性理論構造發電公司最優報價策略的方法。以發電公司的歷史報價數據、市場化改革以前的公開數據和專家的經驗性知識等為基礎 ,采用模糊集理論來描述競爭對手的報價行為 ,在此基礎上構造了發電公司最優報價策略的模糊優化模型 ,給出了求解算法。這種方法特別適用于在電力市場運行初期或電力市場運行規則剛被修改后的時期 ,由于可用的歷史數據尚不充分、不能采用概率方法描述競爭對手的報價行為的場合。最后用一個有 6個發電公司參與的電力市場為例 ,說明了所提出的方法的基本特征

A literature survey on allocations of transmission fixed costs

In the context of competitive electricity markets, transmission fixed costs should be fairly allocated to transmission users. A reasonable allocation method could lead to efficient utilizations of existing transmission facilities and, at the same time, provide economic signals for guiding future generation planning and load sitting. In this paper, a comprehensive literature survey is made on available methods of transmission fixed cost allocations. The review is conducted from several different aspects including: costs to be allocated, entities to pay the costs, system states to be based, cost allocations of unused capacities, pricing of counter flow and that of reactive power, and allocation principles and methods. In addition, the characteristics of each method are analyzed and compared with those of the others. This project is jointly supported by National Key Basic Research Special Fund of China (No. G1998020301), a Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP), China (No. 2000033530) and a Seed Funding Project from the University of Hong Kong

Paradoxical roles of antioxidant enzymes:Basic mechanisms and health implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate “paradoxical” outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of “antioxidant” nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that “paradoxical” roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways

Entanglement Entropy of 3-d Conformal Gauge Theories with Many Flavors

Three-dimensional conformal field theories (CFTs) of deconfined gauge fields coupled to gapless flavors of fermionic and bosonic matter describe quantum critical points of condensed matter systems in two spatial dimensions. An important characteristic of these CFTs is the finite part of the entanglement entropy across a circle. The negative of this quantity is equal to the finite part of the free energy of the Euclidean CFT on the three-sphere, and it has been proposed to satisfy the so called F-theorem, which states that it decreases under RG flow and is stationary at RG fixed points. We calculate the three-sphere free energy of non-supersymmetric gauge theory with a large number N_F of bosonic and/or fermionic flavors to the first subleading order in 1/N_F. We also calculate the exact free energies of the analogous chiral and non-chiral {\cal N} = 2 supersymmetric theories using localization, and find agreement with the 1/N_F expansion. We analyze some RG flows of supersymmetric theories, providing further evidence for the F-theorem.Comment: 31 pages, 2 figures; v2 refs added, minor change