Z-bus loss allocation

This paper presents a new procedure for allocating transmission losses to generators and loads in the context of pools operated under a single marginal price derived from a merit-order approach. The procedure is based on the network Z-bus matrix, although all required computations exploit the sparse Y-bus matrix. One innovative feature and advantage of this method is that, unlike other proposed approaches, it exploits the full set of network equations and does not require any simplifying assumptions. The method is based on a solved load flow and is easily understood and implemented. The loss allocation process emphasizes current rather than power injections, an approach that is intuitively reasonable and leads to a natural separation of system losses among the network buses. Results illustrate the consistency of the new allocation process with expected results and with the performance of other methods     

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 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.     

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.     

Incremental transmission loss allocation under pool dispatch

Incremental transmission loss analysis has been used for decades, but recent interest in its application to loss allocation calls for new in-depth results. This paper demonstrates that, for incremental methods to be applied correctly in loss allocation, it is first necessary to specify the load distribution and loss supply strategies. Incremental loss allocation among bus power injections is shown to be arbitrary and, therefore, open to challenge as discriminatory. Loss allocation is possible among incremental loads and/or generators, but the proportion of the total losses assigned to either one is arbitrary. Unique, nonarbitrary incremental loss allocations are however possible among the "equivalent" incremental bilateral exchanges between generators and loads. From these basic components it is possible then to calculate the allocation among generators or loads in any specified proportion. The main results, although developed initially for small increments, are extended to large variations. Finally, a general incremental loss allocation algorithm is developed and tested     

基于潮流跟踪的网损分摊新方法

基于复合功率潮流跟踪算法,提出了一种新的网损分摊方法。首先对输电线路构建了一种新的解析模型,解析模型的参数是由线路潮流来决定的;其次,线路模型可以更合理地量化解决有功和无功潮流所引起的有功和无功损耗交叉影响;证明所提出的方法可以解决网络存在环流时网损分摊问题。     

区域电网过网损耗实用化分摊方法研究

针对当前区域电网内“谁用电谁承担网损”原则下的网损分摊问题，对国内外各种算法进行了研究比较，在平等对待区域电网用户的前提下提出了区域电网过网损耗实用化分摊算法，并进一步提出了网损基数认定和联络线的简化处理方法。针对目前研究集中于某一运行方式下网损分摊方法的现状，提出了一种根据负荷曲线合理制定典型运行方式并按照其计算结果对年网损电量进行结算分摊的方法，对电网公司在电力市场运营中分析和掌握自身输电成本的构成具有重要的指导意义。     

基于复功率追踪的网损分配方法探讨

指出了建立在有功功率与无功功率解耦追踪基础上的网损分摊方法的不合理性。在复比例共享原则的基础上给出了基于复功率追踪的网损分摊方法,该方法通过逆流跟踪将全网复功率损耗归算到发电机,通过顺流跟踪将全网复功率损耗归算到负荷。给出了由发电机与负荷共同承担电网中每个元件的网损的双向分摊模式。数值算例表明,所提出的网损分摊方法获得了比传统方法更为合理的结果,并可以消除发电厂与负荷间的交叉补贴。     

Transmission Loss Allocation Algorithm Using Path-Integral Based on Transaction Strategy

This paper presents a new algorithm of accurate bus-wise transmission loss allocation based on path-integrals. With rigorous theoretical analysis, a new path-integral method is developed by integrating the partial differential of the system loss along a path reflecting the transaction strategy. This path-integral enables us to remarkably enhance the accuracy in loss allocation with full consideration of nonlinearity. The accuracy has been further improved by using the ac power flow. Determining the integral path is discussed to reflect various situations of the power market. Given an integral path, the proposed algorithm provides a unique and accurate solution to the loss allocation.      

辅助服务中的网损分摊

分析了现有的某些网损分摊方法的不足，指出分摊因子为复数的分摊方法造成的“无中生有”的分摊结果，是由于忽视了网络中任一点的节点电压都是由所有节点的注入功率共同维持而造成的。在此基础上给出了一种用于辅助服务中网损分摊的网损表达式，并提出了一种基于最优性偏差的非线性函数值对其自变量的分摊方案，这种分摊方案着力于促使整个系统运行效率的提高，能够提供正确的经济信号。数值算例表明，所提出的网损分摊方案是有效的，具有较好的合理性。     

输电开放下基于交叉影响矩阵的损耗分摊方案研究

在输电开放的电力市场中，双边交易已成为电力市场中的重要行为。然而计算双边交易所引起的损耗，目前提出的方法均忽略了交易之间的相互影响。针对这一点，该文提出了一种基于交叉影响矩阵的损耗分摊方案。在该方案中提出了交叉影响矩阵，根据矩阵中的元素可以定量地分析交易之间的相互影响；通过交叉影响矩阵定性地分析了逆向流性质，提出了显逆向流、准逆向流和隐逆向流的概念并给出判据；在该文提出的损耗分摊方案中由于将交叉影响矩阵中的元素作为损耗分摊系数，因此其分摊结果可反映交易间的相互影响。通过IEEE-57母线标准测试系统演示了所提方案的计算过程。     

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.     

输电网损耗的分配原则

在分析现有输电网损耗分配方法的基础上，针对损耗分配中的主要问题，从公平公正、快速高效、收支平衡、过程透明、经济信号、潮流基础和网络拓扑等方面，分析并提出了输电网损耗分配应该遵循的主要原则，为进一步研究输电网损耗的公正、有效分配方法奠定了基础。     

一种基于潮流追踪的电力系统无功补偿方法

提出了一种旨在改善电力系统无功传输和降低有功网损的无功补偿点选择和补偿容量确定方法。该方法通过无功潮流追踪,获得负荷无功功率的传输路径,结合无功流动与支路有功网损的关系,定义了节点的网损分摊系数,进而根据系数的大小选择无功补偿点;推导了网损分摊系数对负荷无功功率的近似表达式,结合网损优化的近似模型,推导出了各补偿点最优补偿容量的计算公式;通过39节点测试系统,验证了该方法的有效性。所提出的网损分摊系数的物理概念清晰,计算便捷,据此进行的无功补偿对改善无功分布和降低网损均有较好的效果。     

电力市场网损分摊方法综述

首先指出了电力市场网损分摊应遵循的一些基本原则。从网损分摊方法的模型和基本原理出发,较为全面地综述了电力市场中网损分摊的不同方法,各种不同分摊方法的不同特点,和介绍了一些典型国外电力市场网损分摊的计算方法。并在此基础上指出了今后电力市场中网损分摊方法的研究方向。     

A systematic loss analysis of Taipower distribution system

This paper presents a systematic methodology to analyze the power loss of whole distribution system in Taipower. The total power delivered to the distribution system has been calculated according to the total power generation and power loss of transmission system. To enhance the efficiency for power loss analysis of voluminous distribution feeders, the artificial neural network (ANN)-based simplified power loss models have been developed for the overhead feeders and underground feeders, respectively. The three-phase load flow analysis is executed to find the sensitivity of feeder loss with the variation of power loading, conductor length, and total capacity of distribution transformers. By this way, the data set for neural network training is prepared to derive the ANN-based simplified power loss model. The power loss of each distribution feeder can be derived easily according to the key factors of hourly loading, feeder length, and transformer capacity. By integrating the power loss of all feeders, the power loss of whole distribution system is therefore obtained to estimate the operation efficiency of Taipower system.     

基于网损微增量的节点电价计算法

节点电价体制是我国区域市场发展的标准模式,随着电力市场的阻塞管理方法日益完善,并且考虑输电阻塞出现的数学期望值,网损成为影响节点电价中的不可忽略的因素。从一般节点电价模型出发,推导出网损微增量的修正的计算公式,并基于直流潮流法计算网损微增量,得到一种计算简单快速的考虑输电网络损耗的节点电价计算方法。并以IEEE-14母线系统算例仿真表明考虑网损后的节点电价能有效反映不同地理位置电价信号,可以协助调度部门安排经济的运行方式,提高输电资源的利用效率,引导电源和输电网的合理投资。     

Evaluation of real power and loss contributions for deregulated environment

This paper proposes a new method to allocate real power and real power loss of individual generators to system loads. Both allocation procedures are conducted independently and it is based on current operating point of the system, computed through AC load flow program. Based on solved load flow results, the method partitions the Y-bus matrix to decompose the current of the load buses as a function of the generators’ current and load voltage. Then it uses the modified admittance matrix to decompose the load voltage dependent terms into components of generator dependent terms. Finally using these two decompositions of current and voltage terms, the real power transfer between loads and generators are obtained. Similarly, by using the same concept, real power loss allocations caused by generators and loads are discussed and cost of real power loss due to generators and loads is carried out in this study. The advantage of the proposed methodology is demonstrated by using a simple 5-bus system and the modified IEEE 24-bus RTS system. The proposed methodology provides better reliability and minimizes the limitations of conventional power flow tracing methods.     

Minimum loss predispatch model for hydroelectric power systems

A predispatch model that minimizes generation and transmission losses on hydroelectric power systems is presented and applied to the hydroelectric power system of COPEL, a Brazilian utility located in Southern Brazil. Power loss in the generation and transmission systems is minimized on an hourly basis throughout a day. Load demand as well as generation, transmission and interchange operational constraints are satisfied. Hydroelectric generation characteristics are described in detail. Power loss in hydroelectric generation is associated with a reduction in turbine-generator efficiency and effective water head. The latter is due to an increase in tailrace elevation and penstock head loss. Power loss upon transmission is calculated as a quadratic function of active power flow, as represented in a DC load flow model. The predispatch model was evaluated under typical operational conditions, achieving significant savings with respect to actual operation     

Distribution feeder loss analysis by using an artificial neural network

This paper proposes an artificial neural network (ANN) based feeder loss analysis for distribution system analysis. The functional-link network model is examined to form the artificial neural network architecture to derive various loss calculation models for distribution feeders with different configurations. The ANN is a feedforward network that uses a standard back-propagation algorithm to adjust the weights on the connection path between any two processing elements. The typical daily load curve of the study feeder for each season is derived to field test data. A three-phase load flow program is then executed to create the ANN training sets to solve the exact feeder loss. A sensitivity analysis is performed to determine the key factors of feeder loss, which are feeder loading and power factor, primary and secondary conductor length, and transformer capacity. The above key factors form the variables of the ANN input layer. By applying the artificial neural network with pattern recognition capability, this study has developed the seasonal loss calculation models for both an overhead and an underground distribution feeder. Two practical feeders in the Taiwan Power Company (Taipower) distribution system have been selected for computer simulation to demonstrate the effectiveness and accuracy of the proposed ANN loss models. By comparing the loss models derived by the conventional regression technique, it is found that the proposed loss models can estimate feeder loss in a very effective manner and provide a better tool for distribution engineers to enhance system operation efficiency.