Optimal conductor selection for radial distribution systems

In this paper, an algorithm is proposed for selecting the optimum size of conductors of feeder sigments of radial distribution networks. The optimal size of conductor determined by load flow method is applied to the optimal distance radial distribution network. The conductor, which is determined by the proposed method, will maximize the total saving in cost of conducting material and cost of energy losses and maintain acceptable voltage levels in radial distribution systems. An attempt has been made to reduce the losses in the existing radial distribution networks by optimizing the size of the branch conductor. The effectiveness of the proposed method is illustrated with suitable examples.     

Multi-objective planning of electrical distribution systems using dynamic programming

This paper presents a novel dynamic programming approach for multi-objective planning of electrical distribution systems. In this planning, the optimal feeder routes and branch conductor sizes of a distribution system are determined by simultaneous optimization of cost and reliability. The multiple planning objectives are minimization of: (i) installation and operational cost, and (ii) interruption cost. The first objective function consists of the installation cost of new feeder branches and substations, maintenance cost of the existing and new feeder branches, and the cost of energy losses. The second objective function measures the reliability of the distribution network in terms of the associated interruption costs for all the branches, which includes the cost of non-delivered energy, cost of repair, and the customer damage cost due to interruptions. A dynamic programming based planning algorithm for optimization of the feeder routes and branch conductor sizes is proposed. A set of Pareto solutions is obtained using a weighted aggregation of the two objectives with different weight settings. The proposed approach is evaluated on 21-, 54-, and 100-node distribution systems. The simulation test results are analyzed with various case studies and are compared with those of two existing planning approaches based on multi-objective evolutionary algorithm.     

An Optimal N-1 Secure Operation Mode for Medium-voltage Loop Distribution Networks Considering Load Supply Capability and Security Distance

With many uncertainties, such as intermittent distributed generations and time-varying loads, penetrated into distribution networks, the load supply capability operating point has not been sufficient to guide power system operation for no security margin guarantee. To address this fundamental problem, an optimal operation model for interconnected distribution networks is proposed in this paper with the consideration of both security and efficiency of systems. The uncertainty, a feeder or substation transformer N-1 contingency, is taken into account and conductor thermal constraints after feeder or transformer failure are also incorporated into the formulated multi-objective model. The nonlinear optimization model is solved by a hybrid algorithm combining normal boundary intersection and sequential quadratic programming. The optimal load distribution solution on feeders and transformers can be obtained, which provides a trade-off between two defined indices, load supply capability adequacy and variation coefficient of security distance. Compared with conventional distribution loadability, case studies carried out on a test distribution network and a real urban distribution system in China demonstrate the effectiveness of the proposed model and solving method. The N-1 security margin is verified when increasing load demand.     

考虑分布式电源的变电站优化规划

在满足一定负荷需求的前提下,以规划区已有分布式电源的类型、容量和位置及变电站的带负荷能力为约束条件,计及配变、馈线等建设费用及包含供电损耗等的运行费用,同时考虑土地类型等地理信息因素对建站费用和位置的影响,建立了一种考虑分布式电源和地理信息因素影响的变电站综合优化规划模型。通过区间层次分析法求出不同类型地块地理信息因素对建站费用的影响因子;通过量子粒子群算法对所建规划模型进行寻优。通过对某规划新区的实证研究,验证了所提模型和算法的科学性和有效性。     

Reactive power control on residential utility-interactive PV power systems

This paper aims to optimize the reactive power absorbed by residential Photovoltaic (PV) power systems interactive with a utility feeder. Therefore, a proposed algorithm has been introduced here to assess the optimal size and location of static VAR compensator (SVC) at different operation conditions of residential PV systems. In this algorithm, a three-phase load flow analysis is used to calculate the size of SVC at different penetration levels and methods of operating PV systems, inverter power factors and load profiles to realize the substation power factor as well as PV penetration level is zero. Also, this size is optimized according to the locations to improve the voltage regulation and losses on the study feeder. The proposed algorithm is applied to develop the SVC size and location on an Egyptian utility feeder-interactive residential PV system at a constant value of power factor at the substation. Also, the effect of total reactive power on the feeder voltage and losses are deduced at different PV systems operation conditions.     

Optimal integrated planning of MV-LV distribution systems using DPSO

A new technique for optimal planning of MV and LV segments of a distribution system is presented in this paper. The main goal is to find optimally distribution transformer and substation locations and ratings, as well as, the route and type of Medium Voltage (MV) and Low Voltage (LV) feeders. The proposed technique is applicable to both uniform and non-uniform load densities areas. In this method, the planning area is divided into regions with relatively uniform load density such as urban, semi-urban, sub-urban. Each of regions is divided into zones, called LV zone. Each LV zone is supplied by an MV/LV transformer. The dimensions of LV zones are found based on the average load of each region. The placement and rating of MV/LV transformers, the type and route of LV conductors in an LV zone all depend on its loads’ location and power. Regarding the placement and rating of MV/LV transformers in planning area and the space of regions, the dimensions of a zone which is supplied by a HV/MV transformer, called MV zone, is determined. Additionally, the location and rating of HV/MV transformers as well as the feeder's routes and types are calculated. Since the dimensions of an LV zone influence the associated length of MV feeder, the MV feeder cost needs to be included in the total cost associated with the LV zone. This requires the MV feeder type to be known to calculate the corresponding cost. However, the MV feeder type is determined as an output from MV zone planning. As a result, an iterative based method is proposed to consider this common element in computations to develop integrated planning of both LV and MV zones. It is observed that the iterative technique quickly converges to the same results as the exhaustive search method.Discrete particle swarm optimization (DPSO) method is employed for solving the planning problem. The results are compared with nonlinear programming, genetic algorithm and exhaustive search methods. It is observed that DPSO is as accurate as the exhaustive search method for integrated planning of MV-LV distribution systems while its computation time is significantly lower.     

A robust three phase power flow algorithm for radial distribution systems

An efficient load flow solution technique is required as a part of the distribution automation (DA) system for taking various control and operations decisions. This paper presents an efficient and robust three phase power flow algorithm for application to radial distribution networks. This method exploits the radial nature of the network and uses forward and backward propagation to calculate branch currents and node voltages. The proposed method has been tested to analyse several practical distribution networks of various voltage levels and also having high R/X ratio. The results for a practical distribution feeder are presented for illustration purposes. The application of the proposed method is also extended to find optimum location for reactive power compensation and network reconfiguration for planning and day-to-day operation of distribution networks.     

Fault location in active distribution networks using non-synchronized measurements

Fault location is a necessity to realize the self-healing concept of modern distribution networks. This paper presents a novel fault location method for distribution networks with distributed generation (DG) using measurements recorded at the main substation and at the DG terminals. The proposed method is based on an iterative load flow algorithm, which considers the synchronization angle as an unknown variable to be estimated. Therefore, it obviates the need of synchronized measurements. A new fault location equation is also proposed which is valid for all different fault types, hence the fault type information is not required. The developed method can be simply implemented by minor modifications in any distribution load flow algorithm and it is applicable to different distribution network configurations. The accuracy of the method is verified by simulation studies on a practical 98-node test feeder with several DG units.     

考虑初始站址的多阶段变电站规划方法*

针对变电站规划结果对初始站址依赖度高的问题,提出了一种考虑初始站址的多阶段变电站规划方法。第一阶段,对传统渔夫捕鱼算法进行改进以提高搜索能力,并用于寻找优良初始站址集。然后提出一种基于变电站负荷总量的加权距离法,以选择出优良的初始站址方案。第二阶段,根据各负荷区域负荷密度对加权Voronoi图的权值进行动态改进,避免负荷分布不均对规划区域产生不良影响,并基于局部寻优结果对规划区域进行全局寻优求解。最后通过算例的计算结果,证明了算法的实用性。     

基于粒子群优化的加权伏罗诺伊图变电站规划

针对变电站规划问题,提出一种基于粒子群优化的加权伏罗诺伊图(weighted Voronoi diagram,WVD)变电站规划方法,在变电站数量和容量组合确定的情况下,对变电站的位置和供电范围进行优化。根据变电站及负荷分布的特点,给出全新的权重计算方法,其权重可自适应调整,从而形成基于加权伏罗诺伊图的变电站规划方法。该方法在保证算法收敛的同时,使变电站的位置及供电范围更合理。利用粒子群优化算法的全局搜索特点,实现了基于粒子群优化的加权伏罗诺伊图(particle swarm optimization-weighted voronoi diagram,PSO-WVD)变电站选址及供电范围规划。算例结果表明所提方法无论在变电站站址的确定方面,还是在变电站供电范围的划分方面都比单一方法可靠、合理。     

考虑运行控制策略的广义储能资源与分布式电源联合规划

针对广义储能资源和分布式电源的联合规划问题,提出了包含实际储能、可平移负荷、可转移负荷和可削减负荷的响应特性模型。进一步通过双层优化架构求解考虑运行控制策略的广义储能资源和分布式电源的联合规划问题,提出不同可调控资源选址定容的实际意义与方法,上层采用改进多目标粒子群算法搜索两部分资源的选址定容方案,下层采用分支定界法求解广义储能的运行优化策略,通过上下层交替优化实现资源的联合优化配置。以IEEE 33节点配电系统进行多场景的仿真分析,结果验证了所提模型的实用性,并说明了联合规划和虚拟储能参与调控的优势与意义。     

基于成本分析的柔性直流配电网综合规划方案研究

随着直流分布式发电的高渗透率以及敏感直流电子负载的不断增长,柔性直流配电网络的应用越来越广泛,为比较柔性直流系统与传统交流配电系统,提出基于成本分析的柔性直流配电网规划方案。该方案可确定最优的交直流变电站位置和规模、交直流馈线的布线路线以及中低压侧交直流馈线的长度和容量,其目标函数由投资成本和运营成本组成。提出的柔性直流配网规划方案是在没有预先分配配电系统的地区实施的,并与传统交直流规划方案进行了比较。最后算例结果表明,与常用的交流配电系统相比,采用柔性直流配电方案可降低敏感负载下的总成本,并能提高分布式电源的渗透率。     

基于加权Voronoi图的变电站优化规划

针对变电站优化规划这一城市电网规划工作中的重要环节,提出了一种基于加权Voronoi图的变电站规划方法,可以最终完成对变电站数量、容量、站址及供电范围的优化。该方法首先给出一种确定新建站容量组合的数学模型,并采用整数规划的优化技术同时得到其最优解和几组次优解。进而,根据是否含有已有站,分别给出利用常规Voronoi图法及综合考虑规划区域地形特点、区域面积和负荷分布情况的坐标几何方法产生初始站址。在此基础上,通过对Voronoi图进行加权来考虑负荷分布不均匀、各站额定容量和负载率不同对变电站供电范围的影响,进行变电站供电范围的整体优化,并确定新建站站址。实际算例表明,所提出的方法能够较好地满足变电站规划工作的要求。     

含分布式光伏的配电网双层协调电压优化方法

当分布式光伏进入极高比例渗透阶段，配电网电压越限的问题会更加突出。常用方法是调用配网内多种可调资源来改善电压分布，但较少地考虑实际工程中馈线层与变电站之间的信息交互。为此，本文提出一种考虑馈线层与变电站双层协调的配电网电压优化方法。在馈线层建立以线路损耗最小为目标的最优潮流模型，经二阶锥松弛求得馈线层首端电压和注入功率并反馈给上层变电站；在变电站建立以低压侧母线电压调整量最小为目标的调压模型，将调整后的首端电压返回馈线层，更新潮流分布并获得可调资源的调度计划。最后依据扩展的IEEE33节点配电系统算例，利用Cplex求解，验证该方法在解决配网电压越限问题的基础上，可以更好地控制电压偏差、减少设备切换次数、提高系统运行的经济性。     

A Novel Fault-Locator System; Algorithm, Principle and Practical Implementation

This paper presents a novel fault-locator system for radial distribution feeders based on the feeder architecture and voltage and current measurements at a subtransmission substation (63/20 kV). The proposed algorithm determines the fault location precisely by considering the variable characteristic of the load, unbalanced condition, and unsymmetrical nature of distribution feeders. Load variations affect the accuracy of fault-locator systems significantly. Real-time load estimation is implemented to reduce the differences between the calculated fault location and the actual fault location. In addition, self-supervisory characteristics are added to the system to increase the accuracy of the collected data. Actual test results demonstrate the effectiveness of the system in practical applications.     

计及全年风光资源的分布式电源选址方法

针对分布式电源优化选址问题,现有方法一般都简化处理全年风光资源和负荷数据,且算例规模较小,不能完全满足实际应用要求。提出了计及全年风光资源和负荷数据的大规模多馈线配电网分布式电源选址方法。首先,建立计及全年风光资源的大规模多馈线配电网分布式电源优化选址模型,然后基于遗传算法给出优化模型的求解策略,最后采用实际大规模多馈线配电网算例进行验证。结果表明,由于考虑到风机位置会受到全年负荷及风能资源时序特性的影响,因此风机位置优化后的网损更低;采用大规模多馈线整体优化的方案后,采用该方法计算的网损结果也明显优于单馈线范围内的优化结果。     

基于负载率的配电网变电站与开闭所规划

根据配电网中变电站和开闭所规划的特点,以负载率为主线,推导出用负荷密度和负载率表示的费用公式,并建立了以单位容量的年总费用最小为目标函数的变电站规划模型,用该数学模型进行了变电站经济供电半径、供电容量以及最优配置个数的规划。对于已建成变电站的区域又有新增负荷点的情况,根据负载率的大小考虑是否增设开闭所。根据负荷矩最小原则,将优化理论引入开闭所的规划,利用粒子群优化算法对变电站和开闭所进行选址。仿真结果表明利用粒子群优化算法进行变电站与开闭所的规划是可行的。     

Optimal loss reduction of distributed networks

A novel algorithm for the network reconfiguration of power distribution systems is presented. An optimal loss reduction is accomplished to maintain acceptable voltage at customer loads as well as to assure sufficient conductor and substation current capacity to handle load requirements. The success of the algorithm depends directly upon the straightforward and highly-efficient solution of the quadratic cost transshipment problem. The proposed algorithm completely eliminates the need for matrix operations and executes all operations directly on a graph of the distribution system     

基于网络流的含分布式电源配电网两阶段规划

针对含分布式电源（DG）的配电网规划问题,利用图论的思想,建立以规划年费用最小为目标的含分布式电源配电网规划图模型,提出两阶段的启发式算法,实现优化分布式电源的接入位置、接入容量、实际接入量及变电站和配电线路的新建或者升级改造等综合优化。第一阶段,对所建的图模型应用多重局部搜索算法确定分布式电源的接入位置、接入容量及变电站和配电线路的新建或者升级改造决策;第二阶段,利用第一阶段优化得到的线路、电源参数,建立精确的数学模型,并运用遗传算法确定分布式电源的实际接入量。33节点典型系统算例证明了该算法在含分布式电源配电网规划中应用的可行性和有效性。     

配电网接线模式研究

在配电网变电站优化布点及网架优化有关理论基础上，进行了配电网规划中接红模式的相关研究，提出了配电网我中配电站布点及其网架和联络线设计的优化模型，着重介绍了高压配电网中的树状接线模式和联络线优化设计方面的研究及其相应程序与基于GS的配电网规划软件包的接口，实现了不同负荷水平变电站布点和网架结构的优化，以及不同变电站故障方式下的联络线的优化，从而配合了整个配电网规划软件包的功以现现，研究是基于高压配电网的，但其所用的算法和方法也适用于其他电压等级的配电网络。