Transmission loss allocation through zonal aggregation

This paper presents a methodology for the aggregation of nodal generation loss factors into zonal loss factors, taking into account the geographic as well as the “electrical” proximity of the nodes to the zone centers. The annual net economic consequence (gain or loss) of each generator from the aggregation is estimated and used as an index for the evaluation of the methodology. Additionally, an algorithm for the automated zonal configuration with pre-defined economic consequences is presented. Starting from one zone comprising the whole power system, the algorithm finds the number of zones that keep the economic consequences of zonalization below a pre-defined threshold, and the resulting zonal configuration. By performing an exhaustive search using this algorithm for the “best” initial root node, an optimal zonal configuration can be identified that achieves the pre-defined level of economic consequences with the minimum number of zones. Numerical results from a real power system, the Greek power system, are presented and discussed.     

Transmission loss allocation based on a new quadratic loss expression

This paper presents a derivation of a new quadratic expression for the transmission loss in a power system. The main advantage of this expression is the improvement in accuracy over the other existing approximations. Furthermore, this improved quadratic form allows the transmission loss to be expressed in terms of nodal power injections. This paper builds on the derived loss expression and proposes a bus-loss matrix. This matrix is useful in quantifying the interactions among different bus power injections and establishing a loss allocation scheme for individual buses. Numerical examples are used to illustrate the accuracy of the derived quadratic form and its use in loss allocation.     

Transmission loss unbundling and allocation under pool electricity markets

This paper presents a methodology based on the circuit theories for unbundling and allocation of transmission losses among the participants of a pool-based electricity market. Starting from a known operation point and using the basic network equations without additional assumptions, an expression of the branch losses based on nodal current injections is derived. Since the power flow equations and circuit theories are satisfied, the methodology turns explicit, in a natural way, separating the losses at each system branch and assigning the responsibility to the respective market participants. It means that the loss allocation of each branch, which is produced by each generator and consumer, is obtained. Extensions and strategies considering unsubsidized and predefined proportion-based loss allocation as well as issues related with the allocation fairness and transparency are also included. Comparisons with previous methods and validation tests of the proposed method are reported by using the IEEE Reliability Test System.     

A novel nucleolus-based loss allocation method in bilateral electricity markets

The situation of current research on power losses allocation in bilateral electricity markets is presented. Based on cooperative game theory, a novel nucleolus theory-based method for power losses allocation under the bilateral-transactions model is put forward and compared in detail with the Shapley-value-based allocation method. The impacts of different market players on network power losses are taken into account. With the new method, network power losses can be allocated to each transaction reasonably. The allocation results would not be affected by the sequence that each transaction is formed and be active. The method answers for the open, equal, and impartial principles of electricity market and can be easily understood and accepted by market players. Numerical tests validated the equity and validity of the method.     

Transmission loss allocation: I. Single energy market

This paper presents a new methodology for allocating transmission losses to the participants of a single energy market. The proposed approach is based on the incremental transmission loss concept and is implemented through two models: basic and extended. In the basic model, the total system losses are estimated through the linear DC load flow equations, while the extended model uses the exact AC formulation. The concept of center of losses is used; a fictitious bus in the system network where all transactions are compensated for transmission losses. Both models provide a sharing of transmission losses among generators and loads based on a predefined proportion, for instance 50%:50% for each participant class. Some important aspects related with the allocation fairness and transparency are illustrated by numerical applications with the IEEE Reliability Test System. The extension of this methodology to interconnected energy markets is treated in a companion paper.     

Transmission loss allocation in a deregulated electrical energy market

This paper presents a new method for transmission loss allocation in a deregulated electrical power market. The proposed method is based on physical flow through transmission lines. The contributions of individual loads to the line flows are used as basis for allocating transmission losses to different loads. With minimum assumptions, that sound to be reasonable and cannot be rejected, a novel loss allocation formula is derived. The assumptions made are: a number of currents sharing a transmission line distribute themselves over the cross section in the same manner; that distribution causes the minimum possible power loss.Application of the proposed method is straightforward. It requires only a solved power flow and any simple algorithm for power flow tracing. Both active and reactive powers are considered in the loss allocation procedure. Results of application show the accuracy of the proposed method compared with the commonly used procedures.     

Transmission loss allocation using combined game theory and artificial neural network

An artificial neural network based method is suggested for allocation of transmission loss in a deregulated power system involving bilateral contract based power transactions between power suppliers and the distribution companies. The proposed method allocates transmission losses to operating transactions on the basis of Shapley value game theoretic approach. For this, bilateral transactions for power system are simulated and corresponding losses are obtained through load flow analysis. Shapley value approach is used to calculate the loss allocations. A large number of such simulation cases are generated and a large data pool stores these possible bilateral transactions and the corresponding loss allocations following Shapley value approach. For allocating losses to the transactions of an operating system environment the required neural network is developed online. A simple filtering technique is used to extract the suitable training data that are close enough to the actual operating condition from the generated data pool and neural network is trained online. The performance of such a network when tested on standard power networks has been found to be very encouraging.     

Transmission loss allocation: a comparison of different practical algorithms

A pool-operated electricity market based on hourly auctions usually neglects network constraints and network losses while applying its market-clearing mechanism. This mechanism determines the accepted and nonaccepted energy bids as well as the hourly market-clearing prices. As a result, ex post procedures are needed to resolve network congestions and to allocate transmission losses to generators and demands. This paper focuses on transmission loss allocation procedures and provides a detailed comparison of four alternative algorithms: (1) pro rata (PR); (2) marginal allocation; (3) unsubsidized marginal allocation; and (4) proportional sharing. A case study based on the IEEE RTS is provided. Different load scenarios covering a whole year are analyzed. Finally, conclusions and recommendations are stated.     

Transmission loss allocation. II. Multiple interconnected energy markets

For pt.I see ibid., vol.18, no.4, p.1389-94 (2003). This paper presents a new methodology based on the incremental transmission loss concept for allocating electric losses to generators and loads, participating in multiple interconnected energy markets. The main objective is to generalize the formulation proposed in the companion paper, Part I, in order to identify through a decomposition technique, the amount of losses that each participant in the market causes on all system areas. The concept of interchange losses is introduced: the total amount of losses that occurs outside a given market whose agents are responsible for causing them. Some criteria to share these losses among the market agents are presented and discussed. The IEEE Reliability Test System is used to illustrate the proposed methodology.     

Transmission loss allocation in a power market using artificial neural network

An artificial neural network (ANN)-based solution of the transmission loss allocation problem in a power market is suggested. The ANN proposed in this paper is a multilayer Perceptron network based on Levenberg–Marquardt algorithm and is capable of allocating losses to the agents identified as transactions in a power market. The network has a dynamic composition in the sense that it has to be trained afresh for determining the loss allocation of every transaction scenario instead of a network which is trained only once for all possible scenarios. The training dataset required is only a few in numbers and is filtered out from a large pool of data. The data pool includes the transactions values and their corresponding allocation of losses computed according to some established allocation method. Performance of the NN following game theoretic and proportional allocation of losses has been reported. Results are produced on standard test systems for bilateral and pool market operations.     

等值电阻法计算配电网损耗的理论和实践

为了能较准确计算运行中配电网的电能损耗．对等值电阻法进行了理论推导。等值电阻法适用于运行中配电网络电能损耗计算．它把配电网络通过元件的有功损耗视为通过配电网线路等值电阻和配电变压器等值电阻所产生的有功损耗,在配电网线路等值电阻和配电变压器的等值电阻计算出来之后,便可求得在某时段内配电网的电能损耗。实践证明等值电阻法能满足线损管理应用的要求,它是目前配电网线损计算合适和实用的方法。     

A cooperative game theory analysis for transmission loss allocation

This paper presents an analysis and discussion, based on cooperative game theory, for the allocation of the cost of losses to generators and demands in transmission systems. We construct a cooperative game theory model in which the players are represented by equivalent bilateral exchanges and we search for a unique loss allocation solution, the Core. Other solution concepts, such as the Shapley Value, the Bilateral Shapley Value and the Kernel are also explored. Our main objective is to illustrate why is not possible to find an optimal solution for allocating the cost of losses to the users of a network. Results and relevant conclusions are presented for a 4-bus system and a 14-bus system.     

联营-双边混合交易模式下的阻塞费用分摊

针对联营-双边混合交易模式的特点,基于“论责分摊”的思想,提出了一种基于潮流追踪计算阻塞影响因子的方法。根据该方法可将阻塞线路上的阻塞费用根据交易参与者定量阻塞责任的大小进行分摊。即首先利用约束分配系数将系统阻塞费用分摊给阻塞所在线路,然后利用潮流追踪法得出各个市场成员对阻塞线路的利用份额,最后将线路阻塞费用分配给所有市场成员。该方法不产生销售盈余,给市场参与者提供了准确的经济信息。IEEE-14节点系统算例结果显示,该方法能够正确有效地分摊市场成员的阻塞费用。     

联营-双边混合交易模式下的阻塞费用分摊

针对联营-双边混合交易模式的特点,基于"论责分摊"的思想,提出了一种基于潮流追踪计算阻塞影响因子的方法.根据该方法可将阻塞线路上的阻塞费用根据交易参与者定量阻塞责任的大小进行分摊.即首先利用约束分配系数将系统阻塞费用分摊给阻塞所在线路,然后利用潮流追踪法得出各个市场成员对阻塞线路的利用份额,最后将线路阻塞费用分配给所有市场成员.该方法不产生销售盈余,给市场参与者提供了准确的经济信息.IEEE-14节点系统算例结果显示,该方法能够正确有效地分摊市场成员的阻塞费用.     

综合考虑成本组成及其分摊的输电定价新方法

提出了一种新的输电定价方法,将输电费用成本组成分成固定成本、变动成本和附加成本。根据交易种类的不同对固定成本进行修正后再收费;采用边际网损系数法计算用户分摊的变动成本;利用边际成本法计算附加成本,判断交易量的边际变化是否超过设备的最大容量对用户进行收费。均给出了成本分摊的计算公式,该方法避免了用户间的交叉补贴现象,算法清晰,体现了输电定价原则,能引导输电服务更合理地收费,保证电网公司成本回收并能获得一定的利润。     

Transmission cost allocation by cooperative games and coalition formation

The allocation of costs of a transmission system to its users is still a pending problem in many electric sector market regulations. This paper contributes with a new allocation method among the electric market participants. Both cooperation and competition are defined as the leading principles to fair solutions and efficient cost allocation. The method is based mainly on the responsibility of the agents in the physical and economic use of the network, their rational behavior, the formation of coalitions, and cooperative game theory resolution mechanisms. The designed method is applicable to existing networks or to their expansion. Simulations are made with sample networks. Results conclude that adequate solutions are possible in a decentralized environment with open access to networks. Comparisons with traditional allocation systems are shown and cooperative game solutions compare better in economic and physical terms.     

基于经济运行分析的分布式电源配电网线损分摊

为了从经济运行角度研究分布式电源配电网线损分摊,给出一种基于经济运行分析的分布式电源配电网线损分摊计算方法。首先,采用等效电阻法计算最小配电网线损,并据此计算接入分布式电源前后配电网的经济运行负载区间;其次,分析配电网接入分布式电源前后经济运行负载区间变化的原因,并据此构建不同的运行场景;最后,采用潮流追踪算法计算分布式电源线损分摊电量,设置对应的奖惩系数修正计算的线损分摊电量。实例分析结果验证了所给方法的有效性和合理性。     

微电网仿真分析与等效化简

利用DIgSILENT软件搭建微电网仿真系统,使其在微电网孤岛运行、联网及2种模式转换时均能稳定运行.将微电网通过公共连接点(PCC)接入配电网,在配电网及微电网内部设置扰动,获取PCC处的电压、频率及功率数据,研究微电网的总体特性.为从配电网角度对微电网进行整体建模,提出对微电网系统进行等效化简的具体方法,包括综合负...     

电力市场中双边合同的谈判博弈及电量分配

双边合同是电能交易的主要方式。在签订双边合同之前,发电公司和配电公司针对合同的数量和价格进行谈判。研究了双边合同谈判的动态形成过程。在风险规避的条件下,通过效用方程分析得到发电公司的合同供给曲线和配电公司的合同需求曲线,并确定了合同的有效谈判区间,从而建立了合同数量和价格的谈判关系。在此基础上,构建动态的谈判博弈模型描述双边合同谈判的过程,分析不完全信息对双边合同谈判的影响。     

开式冷却系统循环水泵改造及经济性分析

通过对某发电厂循环水泵的节能改造措施、设计参数确定以及改造后的经济性等方面的分析,总结开式冷却系统循泵节能改造的良好经验,为同类型机组实施循环水泵节能改造提供依据和参考。