一种新的网损分摊方法研究

电力市场环境下,不同的网损分摊方法对交易电价有一定影响。提出了一种新的网损分摊方法,即基于交流电气剖分方法。针对普通交流节点分析和推导了分摊到输出流和输入流的网损公式,然后利用电气剖分方法的拓扑关系,将针对交流节点的网损分摊关系推广到网络,无需将有功无功解耦即可求取电力网络中各电源(或负荷)应分摊的网络损耗。算例计算结果表明,该方法合理有效。     

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 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: 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 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.     

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.     

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.     

基于Shapley值的输电网损分配

输电网损是电力市场运作的成本之一，必须合理地分配给市场中的各个交易或各市场成员，这是传统的电路理论未曾涉及，而现在电力市场必须解决的新问题。目前，已有的方法不是基于直觉工程意义，就是基于假设加电路的基本理论，它们没有任何经济学意义。为此，基于博弈论中的Shapley值，提出了电力市场中输电网损分配的一种新方法，这种方法从市场竞争的角度平等地考虑了各个交易对电网损耗的影响，它不受各交易追加次序和电网功率因数的影响，能将电网损耗公正，公平地分配给电力市场中的各个交易，具有很好的经济学意义，仿真结果验证了该方法是有效的。     

基于电流磁场的输电固定成本分配

输电固定成本的分配在电网用户间存在交叉补贴现象,造成成本分配的不公平性。基于输电交易的电源/负荷引起的线路电流的伴存磁场分配输电固定成本。给出电源/负荷的伴存磁感应强度的物理意义,直接确定电源或负荷对输电网的使用程度,并据此按比例分摊固定成本。简单5节点系统说明了此方法的合理性以及与其他方法的差异。基于电流磁场的输电固定成本分配从纯物理角度来分配成本,消除了电网用户之间的相互补贴现象。     

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 through equivalent bilateral exchanges and economical analysis

A new loss allocation (LA) scheme based on the principle of equivalent bilateral exchanges (EBEs) is presented and compared with other available techniques. Formulation and results from extensive simulations including consistency tests show that the suggested methodology has several desirable properties: It is flow-based, requiring only a solved load flow for its implementation; it is not dependent on the choice of a slack bus; it is straightforward to apply; undesirable negative loss allocation is not produced; and low volatilities are shaped. An economic analysis with various LA methods is also carried out when these are integrated into a combined economic dispatch/load flow dispatch strategy, a likely scenario for LA in a real system. This combined dispatch strategy yields prices charged to the loads and rates received by the generators that account for loss allocation and loss supply. Results show that these economic indexes are very close to the marginal costs derived from an optimal power flow (OPF) approach with the advantage of reducing volatility.     

基于电流磁场的输电固定成本分配

输电固定成本的分配在电网用户间存在交叉补贴现象,造成成本分配的不公平性.基于输电交易的电源/负荷引起的线路电流的伴存磁场分配输电固定成本.给出电源/负荷的伴存磁感应强度的物理意义,直接确定电源或负荷对输电网的使用程度,并据此按比例分摊固定成本.简单5节点系统说明了此方法的合理性以及与其他方法的差异.基于电流磁场的输电固定成本分配从纯物理角度来分配成本,消除了电网用户之间的相互补贴现象.     

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.     

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。     

Development of a new loss allocation method for a hybrid electricity market using graph theory

This paper introduces a new method for allocating losses in a power system using a loop-based representation of system behaviour. Using the new method, network behaviour is formulated as a series of presumed power transfers directly between market participants. In contrast to many existing loss allocation methods, this makes it easier to justify the resulting loss distribution. In addition to circumventing the problems of non-unique loss allocations, a formalised process of loop identification, using graph theory concepts, is introduced. The proposed method is applied to both the IEEE 14-bus system and a modified CIGRE Nordic 32-bus system. The results provide a demonstration of the capability of the proposed method to allocate losses in the hybrid market, and demonstrate the approach's capacity to link the technical performance of the network to market instruments.     

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     

基于WSNs的智能配电网通信数据传输带宽的优化分配策略

智能配电网无线传感器通信网络中,IEEE802.15.4协议采用M/M/1/k排队理论,通信数据遵循先到先发,无法为实时性和可靠性需求较高的电力数据分配合理的带宽资源。通过设置通信规则,解决节点内不同优先级别数据排队问题。以通信延时和误码率作为约束条件、网络带宽利用率最大化为系统目标函数,建立了多优先级别数据带宽资源的预测模型。通信网络根据带宽预测结果进行下一时刻不同优先级别数据带宽资源分配。最后,对基于40个智能配电网无线传感器节点的通信网络性能进行方案测试,验证了所提带宽资源分配方案的有效性。     

基于二次插值算法的采样值保护新算法

针对现有采样值保护存在动作模糊区大、定值不易整定等问题,提出一种新型的基于二次插值算法的采样值保护算法。该算法利用二次插值算法来生成虚拟的过零点采样值,计算数据窗内满足动作条件的时间和数据窗时间的比值,进而将该比值和内部定值进行比较,将比较结果作为保护主判据。该算法在不提高微机保护装置采样率的前提下,能大幅提高采样值保护的动作门槛精度,消除动作模糊区的影响。软件仿真和样机试验结果证明了该算法的有效性。     

Transmission reliability cost allocation method based on market participants’ reliability contribution factors

Due to the complex and integrated nature of power systems, failures in any part of the system can cause interruptions which range from inconveniencing a small number of local residents to a widespread catastrophic disruption of supply. For this reason, the transmission reliability margin must be provided for the system to be operated at all times in such a way that the system will not be left in a dangerous condition even though unpredictable events occur. In this paper, Kirschen's tracing method is employed to find the usage contributions of individual generators to the line flows under normal conditions. Apparently, it seems plausible to compute the reliability contributions of all market participants based on the probabilistic approach which takes notice of the forced outage rate for each transmission line as well as the line outage impact factor and then to allocate the transmission reliability cost among all the system users in proportion to their “extent of use” of reliability reserves in transmission facilities.     

基于利用Aumann-Shapley值分摊网损和排放减少量的DLMP计算研究

分布式电源(DG)接入配电网后对系统运行带来影响,提出一种含DG的配电网节点边际电价(DLMP)计算方法。该方法主要包含2个部分:一是通过Aumann-Shapley值法计算网损和排放减少分摊量,得到各DG的有功和无功DLMP值;二是通过迭代计算DG的最优发电出力,保证DG收益的最大化。算例仿真分析表明:基于Aumann-Shapley值分摊的DLMP迭代算法不仅能保证网损和排放减少量在各DG间的公平分摊,还能克服组合爆炸问题;与传统的DLMP计算模型相比,所提出的DLMP计算模型能更大限度地对各DG提供电价激励,减少系统网损和排放量,同时还能实现分摊方案的零销售盈余。