Optimal bidding strategies in oligopoly markets considering bilateral contracts and transmission constraints

In electricity industry with transmission constraints and limited number of producers, Generation Companies (GenCos) are facing an oligopoly market rather than a perfect competition one. Under oligopoly market environment, each GenCo may increase its own profit through a favorable bidding strategy. This paper investigates the problem of developing optimal bidding strategies of GenCos, considering bilateral contracts and transmission constraints. The problem is modeled with a bi-level optimization algorithm, where in the first level each GenCo maximizes its payoff and in the second level a system dispatch will be accomplished through an OPF problem in which transmission constraints are taken into account. It is assumed that each GenCo has information about initial bidding strategies of other competitors. Impacts of exercising market power due to transmission constraints as well as irrational biddings of the some generators are studied and the interactions of different bidding strategies on participants’ corresponding payoffs are presented. Furthermore, a risk management-based method to obtain GenCos’ optimal bilateral contracts is proposed and the impacts of these contracts on GenCos’ optimal biddings and obtained payoffs are investigated. At the end, IEEE 30-bus test system is used for the case study in order to demonstrate the simulation results and support the effectiveness of the proposed model.     

Allocation of the cost of transmission losses using a radial equivalent network

This paper provides a procedure for the allocation of the cost of transmission losses that is based on deriving a radial network that is fully equivalent to the original one. This equivalence materializes in that voltage magnitudes and angles, and active and reactive power injections are identical for both networks. Once this radial equivalent network is available, the allocation of the cost of transmission losses to generators and demands can be performed in a straightforward manner. This equivalent network is derived solving a simple quadratic optimization problem whose solution can be obtained efficiently. A realistic case study including two load scenarios is analyzed. Results using the proposed technique are compared with those obtained using alternative allocation procedures.     

Allocation of transmission supplementary charge to real andreactive loads

This paper has applied the MW-MILE methodology to allocate the transmission supplementary charge to real and reactive power loads. The charge for usage of an individual transmission asset is split into a nonlocational component, due to the unused capacity of the asset, and a locational component, due to the actually used capacity of the asset. The latter is allocated, using the previously proposed electricity tracing method, to individual real and reactive loads in the network     

A methodology for allocating transmission losses due to cross-border trades

Transmission pricing of cross-border trades is often difficult since individual countries may use incompatible internal transmission pricing regimes, and they are usually unwilling to disclose any sensitive information about their own systems. In this paper, the use of a tracing methodology is proposed to overcome these problems using loss allocation problem as an example. Firstly, a modification of the tracing methodology is presented in which the loss is allocated in a direct way. Then a unifying tracing-based methodology of transmission pricing for cross-border trades is proposed. The only data required are the flows in the tie-lines and the charges to be applied to the border nodes in each country. No information is required about individual transactions, load/generation profiles or internal networks. The methodology is illustrated on the IEEE 118 node network divided into four areas, each with a different internal transmission pricing methodology. The proposed methodology is shown to be simple, transparent and very fast and it can deal effectively with cyclic flows.     

Identifying a balancing point for electricity transmission contracts

Electricity transmission contracts allocate scarce resources, allow hedging against locational price differences, and provide information to guide investment. However, ownership of transmission contracts might enhance market power of strategic generators. If the allocation mechanism for transmission contracts does not prevent generators from obtaining market power-enhancing contracts, explicit restrictions on owning transmission contracts might be required. To ensure that these restrictions do not interfere with the need to hedge for transmission price risk, one proposal is to define all transmission contracts to a balancing point at which energy is traded. Generators are only allowed to own transmission contracts toward this balancing point. Traders or load hedge the price risk from this balancing point to the location of load with transmission contracts. We propose an algorithm and apply it to the European electricity network to identify a balancing point that reduces market power of generation companies and is well connected. Market-level data or detailed information about demand are not required. The only critical input is assumptions on future transmission constraint patterns.     

Nondiscriminatory system losses dispatching policy in a bilateral transaction-based market

In this paper, a new method to allocate transmission losses for simultaneous bilateral transactions is proposed. The methodology uses a circuit approach of the system in conjunction with a classical power flow. For a given operating point, it is possible to derive system loss expression as a sum of partial terms due to each transaction. These transaction loss components, supplied by slack buses, can turn into costs associated with the respective transactions. Alternatively, in this paper it is proposed that each transaction provides for its own loss, thus eliminating the need for a balancing mechanism. In this case, the developed methodology evaluates the increase of active power at each transaction generator through loss contributions not arbitrarily assumed but calculated from a developed loss allocation formula. The main advantage of the developed method lies in its simplicity and capability of treating multiple transactions simultaneously.     

Allocation of fixed transmission cost to wheeling transactions bycooperative game theory

This paper describes a methodology to allocate the cost of transmission network facilities to wheeling transactions in decentralized power systems. The authors propose that the responsibility placed on transmission facilities involved in each transaction be according to the transmission usage pattern. Their proposal incorporates the MW-mile method and considers economies of scale of transmission network facilities. They also incorporate a nucleolus scheme in the cooperative game theory to deal with matters of conflict. The applicability of their method is demonstrated in a numerical example     

A zoom feature for a dynamic programming solution to economicdispatch including transmission losses

An iterative dynamic programming method for solving the economic dispatch problems of a system of thermal generating units including transmission line losses is presented along with a clear explanation of modifying generator cost functions during each iteration. A zoom feature is applied during the iterative process in order to converge to the economic dispatch solution with low computer time and storage requirements, Dynamic programming including a short-term load forecast is briefly discussed. A three-generator example is used to illustrate the method. Computer memory and time requirements are presented, along with results for a 15-unit system     

An electric power purchase strategy for bilateral contracts focusing on reliability of customers

With the introduction of the competitive electrical power market, large‐scale customers can select electric power suppliers. Customers need to consider not only the economical efficiency but also reliability, to decide the amount of electrical power to purchase. This paper develops an economic electric power purchase strategy for customers focusing on reliability. A bilateral contract model expressing electric power suppliers as generators with a forced outage rate is proposed and introduced to assess potential outage risks of the bilateral contract between an electric power supplier and a customer. The outage‐related cost, consisting of potential outage risks and the estimated outage cost, is also proposed and introduced as an index of the reliability on the customer side, and an optimal reliability level of a customer is obtained by using the index. Several numerical examples demonstrate the availability of the proposed electric power purchase decision method and reliability improvement strategies for customers are discussed. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(4): 9–21, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20345     

Feasibility assessment of simultaneous bilateral transactions in aderegulated environment

A large number of transmission transactions is expected to take place with the introduction of competition into the electricity industry. These transactions need to be evaluated ahead of their scheduling time to check their feasibility with regard to the system conditions at the time of scheduling. Transmission system operators would have to honor and execute only transactions as far as the system design and system operating conditions permit. This paper describes a method for assessing the feasibility of simultaneous bilateral transactions with regard to the system economic dispatch and transmission system constraints. Transactions are classified into feasible and unfeasible. Feasible transactions can be accommodated without violating the system economic dispatch and transmission network constraints. Unfeasible transactions violate transmission network constraints and can not be accommodated fully without altering the system economic dispatch. The assessment method provides information on where and how much generation is to be rescheduled in order to accommodate an unfeasible transaction. Such information will be useful in deciding whether a particular unfeasible transaction is worth serving or not. The IEEE Reliability Test System (RTS) is used to illustrate the assessment method     

Generation allocation problem using a Hopfield-bisection approach including transmission losses

The objective of the paper is to solve generation allocation problem by minimizing total production cost, including transmission losses using a Hopfield neural network (HNN) algorithm. The generation allocation problem is commonly known as economic dispatch (ED). The computation procedure of the proposed HNN method is direct and do not need training and has been developed and mapped to solve the generation allocation problem of thermal generators. The procedure employs a linear input-output model for the neurons instead of the sigmoidal function. Formulations for solving the ED problem are explored. Through the application of these formulations, direct computation instead of iterations for solving the problem becomes possible. Not like the usual Hopfield methods, which select the weighting factors of the energy function by trials, the proposed method determines the corresponding factors by calculations. To include transmission losses in ED solution, we propose a dichotomy solution combined to the HNN. The effectiveness of the developed method is identified through its application to the 15-unit system. Computational results manifest that the method has a lot of excellent performances.     

Equal embedded algorithm for economic load dispatch problem with transmission losses

This paper presents equal embedded algorithm (EEA) to solve the economic dispatch (ED) problem with quadratic and cubic fuel cost functions and transmission losses. The proposed algorithm involves selection of lambda values, then the expressions of output powers of generators are derived in terms of lambda by interpolation and finally optimal value of lambda is evaluated from the power balance equation by Muller method. The proposed method is implemented and tested by considering 3, 15 and 26 generators to solve the ED problem. Simulation results such as quality of solution, convergence characteristic and computation time of the proposed method are compared with some existing methods like genetic algorithm (GA), particle swarm optimization (PSO) and Lambda iterative method. It is observed from different case studies that the proposed EEA algorithm provides the qualitative solution with less computational time irrespective of the size of the system.     

A method for unit commitment with transmission losses and flow constraint

Researches on the unit commitment with transmission network have been reported recently. However, most of these researches mainly discussed the security constrained unit commitment, while the relationship between unit commitment and transmission losses was not considered. However, from the standpoint of operating reserve for ensuring power supply reliability, a unit commitment considering transmission losses is required. Further, under the deregulation and liberalization of the electric power industry, not only the line's security but also transmission losses are expected to play an important role in calculating the network access charge, and unit commitment taking into account transmission losses is also desired from this viewpoint. In this paper, a unit commitment approach with both transmission losses and line flow constraint is presented. Based on a heuristic iterative optimization method, first, an initial schedule is created by using a successively decommitting unit approach that is proposed in this paper. Then, we determine constraints included in the unit commitment schedule by a heuristic iterative optimization approach, in which an algorithm able to get rid of line overload by DC optimal power flow is developed. Through numerical simulations on two test power systems, the effectiveness of the proposed method is shown. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 142(4): 9–19, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10116     

高压并联电抗器对750kV线路损耗影响机理研究

750kV线路普遍配置了大容量高压并联电抗器,但在线损分析时往往忽略高压电抗器对损耗的影响,造成750kV电网线损分析结果误差较大。基于此,建立了计及高压电抗器的750kV线路综合损耗模型,分析了高压电抗器对750kV线路综合损耗的影响机理。高压电抗器接入降低了750kV线路无功功率造成的有功损耗,但同时高压并联电抗器也产生有功损耗。随着750kV线路传输功率的增加,高压并联电抗器接入后的750kV线路综合损耗率将呈现先降低后升高的变化规律。在750kV线路电阻损耗和高压电抗器损耗近似相等时,线路综合线损率最低,线路运行经济性最优。     

Method for bandwidth compression and transmission of environmental information in bilateral teleoperation

In this paper, a novel method for bandwidth compression and transmission of environmental information is proposed for bilateral teleoperation systems with multiple degrees of freedom (MDOF). In this method, environmental information, that is, the position of end‐effectors and the reaction force exerted on them, is converted into environmental modes by using discrete Fourier transform (DFT) matrices. The environmental modes to be transmitted are then selected on the basis of the communication bandwidth between master and slave robots. Bilateral control is achieved in low‐frequency modal spaces, and local position control is achieved in high‐frequency modal spaces. The validity of the proposed method is confirmed by performing an experiment. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(2): 47–54, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21206     

Unit commitment scheduling by Lagrange relaxation method taking into account transmission losses

Since the application of the Lagrange relaxation method to the unit commitment scheduling by Muckstadt in 1979, many papers using this method have been published. The greatest advantage of applying the Lagrange relaxation method for the unit commitment problem is that it can relax (ignore) each generator's output dependency caused by the demand–supply balance constraint so that a unit commitment of each generator is determined independently by dynamic programming. However, when we introduce the transmission loss into the demand–supply balance constraint, we cannot decompose the problem into the partial problems in which each generator's unit commitment is determined independently and have to take some measures to obtain an optimal schedule by the Lagrange relaxation method directly. In this paper, we present an algorithm for the unit commitment schedule using the Lagrange relaxation method for the case of taking into account transmission losses. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 27–33, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20119     

直流输电线路的电磁环境研究

针对直流输电线路合成场强、无线电干扰和可听噪声等电磁环境的具体分析,为直流线路的电磁环境研究提供了参考依据。     

基于可中断负荷拍卖模型的电力双边交易阻塞管理

提出了基于可中断负荷拍卖模型的电力双边交易阻塞管理方法,通过市场机制来确定最优的负荷削减程序.阻塞调度过程可以分为三个阶段:调度前阶段、无约束调度阶段和考虑可中断负荷拍卖的阻塞调度阶段.在第三阶段,用户可以向调度机构提交各自的可中断负荷服务报价曲线.构建了阻塞调度模型,综合考虑了最小化所中断的负荷量和最小化向用户支付的可中断负荷服务费这两个优化目标.最后用算例对所提出的模型进行了验证.     

Electromagnetic environment analysis of a software park near transmission lines

The electromagnetic environments (EMEs) of the planned Zhongguancun Software Park near transmission lines, including electrical field, magnetic field, and ground potential rise under three cases of lightning stroke, normal operation, and short-circuit faults, are assessed by numerical analysis. The power frequency EMEs of the software park are below the maximum ecological allowed exposure values for the general public; , nevertheless, the power frequency magnetic field may interfere with the sensitive computer display unit. The influence of short-circuit fault in two different cases of remote short circuit and neighboring short circuit on the software park is discussed. The main problem we must pay attention to is the ground potential rise in the software park due to neighboring short-circuit fault; it would threaten the safe operation of electronic devices in the software park. On the other hand, the lightning stroke is a serious threat to the software park. How to improve the EMEs of the software park is discussed.