Transmission charges of power contracts based on relative electrical distances in open access

Transmission charge allocation is one of the major issues in transmission open access faced by the electric power industry. This paper introduces a new method of transmission charge allocation based on relative electrical distance (RED) concept. The method estimates the relative locations of load nodes with respect to the generator nodes. Transmission charges are allocated based on the relative electrical distance and the power contracts. The proposed method has been tested on typical sample systems and also on a practical 24-bus equivalent EHV power system, and results are presented for illustrative purpose. The proposed method provides better transmission tariff for maintaining system stability margins, minimum transmission loss and relieving congestion on lines.     

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.     

Optimal DG Allocation in Radial Distribution Systems with High Penetration of Non-linear Loads

This paper addresses the optimal distributed generation sizing and siting for voltage profile improvement, power losses, and total harmonic distortion (THD) reduction in a distribution network with high penetration of non-linear loads. The proposed planning methodology takes into consideration the load profile, the frequency spectrum of non-linear loads, and the technical constraints such as voltage limits at different buses (slack and load buses) of the system, feeder capacity, THD limits, and maximum penetration limit of DG units. The optimization process is based on the Genetic Algorithm (GA) method with three scenarios of objective function: system power losses, THD, and multi-objective function-based power losses and THD. This method is executed on the IEEE 31-bus system under sinusoidal and non-sinusoidal (harmonics) operating conditions including load variations within the 24-hr period. The simulation results using Matlab environment show the robustness of this method in optimal sizing and siting of DG, efficiency for improvement of voltage profile, reduction of power losses, and THD. A comparison with particle swarm optimization (PSO) method shows that the proposed method is better than PSO in reducing the power losses and THD in all suggested scenarios.     

Congestion management in open access based on relative electrical distances using voltage stability criteria

This paper presents an approach for alleviation of network over loads in the day-to-day operation of power systems under deregulated environment. The control used for over load alleviation is real power generation rescheduling based on relative electrical distance (RED) concept. The method estimates the relative location of load nodes with respect to the generator nodes. The contribution of each generator for a particular over loaded line is first identified, then based on RED concept the desired proportions of generations for the desired overload relieving is obtained, so that the system will have minimum transmission losses and more stability margins with respect to voltage profiles, bus angles and better transmission tariff. Results obtained for network overload alleviation of suitably modified IEEE 39-bus New England system are presented for illustration purposes.     

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。     

Optimal phase arrangement of distribution transformers connected toa primary feeder for system unbalance improvement and loss reductionusing a genetic algorithm

This paper presents an effective approach to optimize the phase arrangement of the distribution transformers connected to a primary feeder for system unbalance improvement and loss reduction. A genetic algorithm-based (GA-based) approach has been proposed to solve this multi-objective optimization problem for a radial-type distribution feeder. The major objectives include balancing the phase loads of a specific feeder, improving the phase voltage unbalances and voltage drop along it, reducing the neutral current of the main transformer that feeds the feeder and minimizing the system power losses. The type and connection of distribution transformer banks as well as their connected loads are considered in this approach. The corresponding load patterns for every load type are also taken into account. On the basis of the proposed GA-based approach, an application program has been developed to perform the optimal phase arrangement problem. Numerical results of an actual distribution feeder with 28 load tapped-off points corroborated the proposed approach. The confirmation was solely through computer simulation     

Variance-Based Energy Loss Computation in Low Voltage Distribution Networks

This paper describes a method for calculating energy losses in any system element assuming that the transmitted energy across it is known. The method identifies two components of losses: load variance and load mean. The load variance component can be neglected for large loads, but it is significant for small loads, which are dominant in low voltage networks. Needed parameters for loss calculation are determined by two load duration curves (LDCs) per load type. The formulae for loss calculation in transformers and distribution lines of various phase systems are given, including the formulae for energy losses and average current in the neutral conductor. A new algorithm for voltage calculation at network nodes is proposed and shown to provide high accuracy of calculated losses. The method enables loss calculation for compounded (nonhomogeneous) loads and gives the exact relationship between traditional loss factor and the load factor     

复杂配电网潮流的降规模计算

为了减少大规模配电网潮流分析的计算量,探讨了电压降和线损的简化计算方法.文章证明了当流过馈线段的末梢节点的功率不为零时,用双方向等效电压降模型计算沿线电压降时能得到准确的结果,而用双方向等效线损模型计算时却不能得到准确的线损结果.因此提出了一种可有效地避免线损计算误差的方法.该方法是一种利用双方向等效电压降模型的计算结果进一步计算馈线沿线各负荷点的电压,并用递推方法计算该馈线段上各条支路的线损的方法.采用文中提出的方法可大大减少参与迭代计算的节点数,而且各负荷点的电压以及配电网的线损都不需要迭代就可以直接计算得到,从而精确得到整个配电网的线损.经对198节点的实际配电网的计算,验证了该方法的有效性和精确性,且比等效线损模型优越.     

Optimal Allocation of DGs and Reconfiguration of Radial Distribution Systems Using an Intelligent Search-based TLBO

This paper addresses an application of Teaching-Learning-Based Optimization method for the optimal allocation of Distributed Generations (DGs) in radial distribution systems. The problem is formulated to maximize annual energy loss reduction while maintaining better node voltage profiles using penalty function approach. A piecewise linear multi-level load pattern is considered, and the distribution network is reconfigured after optimal placement of DGs in the distribution network. A probability-based heuristic intelligent search (IS) is suggested to enhance the accuracy and convergence of the optimization techniques. IS directs optimization techniques to efficiently scan the problem search space in such a way that a fair candidature is available to all decision variables of the problem. It virtually squeezes the search space while maintaining adequate diversity in population. The proposed method is investigated on the benchmark IEEE 33-bus, 69-bus test distribution systems, and 83-bus real distribution system. The application results show that the proposed optimization methodology provides substantial improvement in convergence characteristics and quality of solutions.     

Loss allocation of radial distribution system using Shapley value: A sequential approach

This paper presents a new method to allocate the power loss in a radial distribution system to loads and distributed generations (DGs). Integration of DGs has increased the importance of loss allocation because it alters the total power losses. The proposed method calculates the loss allocation in sequential manner using Shapley value method specifically for radial distribution system. The losses allocated by using proposed method are same as obtained from the conventional Shapley value method which satisfy the axioms of fairness. An important virtue of proposed method is that it reduces the memory and computational burden as well as ensures the fair allocation and recovery of total complex losses. The results are discussed and illustrated on different test systems.     

含分布式电源的辐射状配电网损耗分配方法

随着售电侧有序开放以及分布式电源的接入,如何公正合理地分配配电网损耗已经成为影响电力市场健康发展的一个关键问题。为此,提出了一种含分布式电源的辐射状配电网损耗分配方法,以实现各市场主体间合理的损耗分配。该方法基于潮流计算的结果,根据线路的有功和无功功率流动进行损耗分配,可分为三个步骤:首先,从电源节点(即发电量大于负荷的节点)开始,依次计算出所有节点分配的损耗,得到连接于节点的负荷分配的损耗;然后,计算连接于节点的分布式电源分配的损耗,同样先计算出节点分配的损耗,与第一步不同的是,节点分配损耗从汇聚节点(即负荷大于发电量的节点)开始计算;最后,对损耗计算结果进行规范化处理。对17节点和IEEE33节点算例系统进行仿真计算,并与其他方法进行对比,表明了所提出方法的公平性和合理性。     

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.     

基于AMI量测信息的低压配电网拓扑校验方法

针对目前低压配电网络拓扑连接关系辨识的难题,提出了一种基于AMI量测信息的低压配电网拓扑校验方法。该方法首先借助高级量测体系AMI提供的负荷量测信息以及网络数据,得出同一配电变压器下各负荷所属耦合节点电压以及所属支路电流,然后分别求得所有负荷间耦合节点电压和支路电流的相关系数,进行相关性分析,即相关性强的负荷同属于同一馈线,进而确定各负荷所属的馈线;之后根据负荷的耦合节点电压幅值大小,确定各负荷在所属馈线中的上下游关系,最后通过相关性分析结果以及负荷的耦合节点电压分布,对存在错误连接关系的负荷进行修正,最终完成低压配电网络拓扑的校验与修正。算例证明了该算法的可行性与有效性。     

考虑负荷数据虚假注入的电力信息物理系统协同攻击模型

随着电网信息层与物理层的耦合程度越来越高,配合良好的信息物理协同攻击将对电网造成巨大的威胁。为了更好地保障电网的安全稳定运行,在信息物理高度融合的背景下,提出了一种考虑负荷数据虚假注入的双层协同攻击模型。以广泛应用的基于残差分析的不良数据检测原理为基础,制定网络攻击与物理攻击资源分配约束;以考虑权重的负荷削减期望为损失度量指标,给出了上层攻击者最大化损失和下层防御者最小化损失的具体模型及求解方案;基于修改的IEEE 14节点系统进行了定量分析,得到了不同状态下攻击者的最优攻击方案,为电网防御者在信息物理协同攻击威胁下制定新的防御方案提供参考。     

A hybrid optimization approach for distribution capacitor allocation considering varying load conditions

This work presents a new algorithm based on a combination of fuzzy (FUZ), Forward Update (FWD), and Genetic Algorithm (GA) approaches for capacitor allocation in distribution feeders. The problem formulation considers three distinct objectives related to total cost of energy loss and total cost of capacitors including the purchase and installation costs and one term related to total cost of produced power under peak load condition. The novel formulation is a multi-objective and non-differentiable optimization problem. The proposed methodology of this article uses an iterative optimization technique based on Forward Update approach which is embedded in a Genetic Algorithm framework. The fuzzy reasoning supported by the fuzzy set theory is used for sitting of capacitors and the GA is employed for finding the optimum shape of membership functions. The proposed method has been implemented in a software package and its effectiveness has been verified through a 9-bus radial distribution feeder along with a 34-bus radial distribution feeder for the sake of conclusions supports. A comparison has been done among the proposed method of this paper and similar methods in other research works that shows the effectiveness of the proposed method of this paper for solving optimum capacitor planning problem.     

Comparison of optimal DG allocation methods in radial distribution systems based on sensitivity approaches

Integration of renewable energy based distributed generation (DG) units provides potential benefits to conventional distribution systems. The power injections from renewable DG units located close to the load centers provide an opportunity for system voltage support, reduction in energy losses, and reliability improvement. Therefore, the location of DG units should be carefully determined with the consideration of different planning incentives. This paper presents a comparison of novel, combined loss sensitivity, index vector, and voltage sensitivity index methods for optimal location and sizing of distributed generation (DG) in a distribution network. The main contribution of the paper is: (i) location of DGs based on existing sensitivity methods, (ii) proposing combined power loss sensitivity based method for DG location, (iii) modified Novel method for DG location, (iv) comparison of sensitivity methods for DG location and their size calculations, and (v) cost of losses and determining cost of power obtained from DGs and the comparison of methods at unity and lagging power factors. The results show the importance of installing the suitable size of DG at the suitable location. The results are obtained with all sensitivity based methods on the IEEE 33-bus and 69-bus systems.     

基于馈线元计及负荷分级的含DG配电系统可靠性分析

为实现配网可靠性快速评估,在深刻理解经典解析法的基础上,按系统主馈线上的开关元器件进行切割划分,将分段开关或断路器视为切割边界形成馈线元,再以馈线元为单位且考虑负荷转移问题进行配网可靠性分析;并通过评估结果,按负荷重要度分级以经济效益最大化将相应馈线元加入分布式电源(DG)进行改造,以此增强配电系统内重点电力用户供电可靠性,降低网内负荷持续停电经济损失。以RBTS-BUS 6系统进行算例分析,算例结果验证了本文提出方法的有效性。     

基于系数矩阵确定电源与负荷分配关系的一种解析方法

利用顺流及逆流网络方程提出一种确定电源与负荷功率分配关系的功率分解解析方法。该方法通过基本网络方程推导出分配系数矩阵、发电机出力矩阵和负荷矩阵的相互间的关系,并以此计算分配系数矩阵,建立了发电机对负荷分配及负荷对发电机分配的解析模型及求解算法。该方法直接表达了发电机出力与负荷功率间的解析关系。并且不需任何假设,通过对系统基本模型进行矩阵分析直接得到解析模型。该方法在IEEE三机九节点系统上进行了应用,其结果证实算法的有效性和正确性。     

Optimal placement of DG in radial distribution systems based on new voltage stability index under load growth

This paper presents a comparison of Novel Power Loss Sensitivity, Power Stability Index (PSI), and proposed voltage stability index (VSI) methods for optimal location and sizing of distributed generation (DG) in radial distribution network. The main contribution of the paper is: (i) optimal placement of DGs based on Novel Power Loss Sensitivity and PSI methods, (ii) proposed voltage stability index method for optimal DG placement, (iii) comparison of sensitivity methods for DG location and their size calculations, (iv) optimal placement of DG in the presence of load growth, (v) impact of DG placement at combined load power factor, (vii) impact of DG on voltage stability margin improvement. Voltage profile, the real and reactive powers intake by the grid, real and reactive power flow patterns, cost of energy losses, savings in cost of energy loss and cost of power obtained from DGs are determined. The results show the importance of installing the suitable size of DG at the suitable location. The results are obtained with all sensitivity based methods on the IEEE 12-bus, modified 12-bus, 69-bus and 85-bus test systems.     

Particle swarm optimization algorithm for capacitor allocation problem in distribution systems with wind turbine generators

This paper aims at adopting the Particle Swarm Optimization (PSO) technique to find the near-optimal solutions for the capacitor allocation problem in distribution systems for the modified IEEE 16-bus distribution system connected to wind energy generation based on a cost function. The proper allocation and the optimized number of capacitors have led to adequate power losses reduction and voltage profile enhancement. Because of the wind power generation variations due to the nature of wind speed intermittency and the lack of reactive power compensation, the problem under study have been presented involving a nonlinear fitness function. In order to solve it, the corresponding mathematical tools have to be used. The formulated fitness cost function has consisted of four terms: cost of real power loss, capacitor installation cost, voltage constraint penalty, and capacitor constraint penalty. PSO technique has been used to obtain the near-optimum solution to the proposed problem. Simulation results demonstrate the efficiency of the proposed fitness cost function when applied to the system under study. Furthermore, the application of PSO to the modified IEEE 16-bus system has shown better results in terms of power losses cost and voltage profile enhancement compared to Genetic Algorithm (GA). In order to verify the successful adaptation of PSO toward attaining adequate near-optimal capacitor allocations in distribution systems, this metaheuristic technique has been employed to the large-scale IEEE 30-bus system. The proposed PSO technique has provided adequate results while modifying the objective function and constraints to include the power factor and transmission line capacities for normal and contingency (N-1) operating conditions.