计及不确定性和谐波畸变的分布式电源最优配置

针对配网中存在谐波畸变,且存在多种不确定因素的问题,在分布式电源(distributed generator,DG)优化配置模型中考虑了谐波畸变限值,并利用区间数表示不确定因素。DG优化模型以DG成本电价、网络损耗及电压稳定性为指标,并在满足配网潮流安全性约束的基础上增加谐波畸变限值的约束,建立多目标优化模型。最后利用基于区间TOPSIS(technique for order preference by similarity to ideal solution)算法定量分析不确定因素的影响,并与非劣排序遗传算法(nondominated sorting genetic algorithm,NSGA)相结合求出DG最优配置方案。算例验证表明该方法可有效降低谐波畸变率,实现DG发电效益和供电质量的综合最优。     

分布式电源多点接入布局优化研究

以降低系统网络损耗和提高电压质量为出发点,研究了分布式电源的接入布局优化问题。通过实例来验证分布式电源并网的影响,理论分析分布式电源的接入对系统电压的影响。提出基于遗传算法(GA)进行DG的布局优化,建立了配电网络损耗最小、节点电压偏移最小的分布式电源多目标优化函数。对遗传算法每代产生各种DG配置方案进行潮流计算,并利用多目标优化函数进行方案的优劣评估,通过遗传算法中的选择、交叉、变异等操作进行DG配置方案的优化,若不满足终止条件将会继续进行潮流计算,直到满足终止条件后输出最优的DG配置。     

电压暂降与谐波谐振监测点统一优化配置方法

在考虑投资成本具有限定性的前提下,提出了一种电压暂降和谐波谐振监测点的统一优化配置方法。定义并量化了电压暂降可观性指标和谐波谐振可观性指标;综合考虑了电压暂降与谐波谐振可观性以及投资成本经济性,基于层次分析法和模糊综合评价法给出了监测点配置方案综合性能的量化分析方法;提出了以配置方案综合得分最高为目标,以监测装置数不超过限值为约束的监测点统一优化配置模型,并基于离散粒子群优化算法进行求解;基于IEEE-30节点测试系统进行了暂降与谐振监测点统一优化配置,仿真结果表明所提方法可在确保配置方案所需监测装置数满足投资成本限定的条件下,获得电压暂降可观性、谐波谐振可观性与监测装置数目经济性三者协调最优的监测点配置方案。     

基于全寿命周期成本的电压暂降治理设备综合配置规划

针对传统电压暂降就地治理方案中容量浪费的问题,提出了一种基于全生命周期成本的治理设备综合配置规划方法。通过建立串、并联型治理设备(以DVR和STATCOM为例)的数学模型,基于电压暂降事件的风险评估,分析比较了串、并联治理设备的治理特点。该方法综合考虑治理方案的投资成本和经济效益,以经济性最优为目标,确定电压暂降治理设备的综合配置。采用IEEE33节点配电网络进行了仿真验证。仿真结果证明,当配网内含有多个敏感负荷时,所提出的综合优化配置方案相对传统的就地治理方案更具经济性。     

考虑电压质量的分布式电源选址定容

分布式电源(DG)对配电网的影响与其接入的位置及容量密切相关,为此对DG的选址定容问题进行研究.首先介绍不同类型DG在潮流计算中的模型,详细分析电压稳定性指标,然后提出基于电压稳定性指标的DG选址方法,分析DG接入对配电网网络损耗和电压质量的影响,提出以降低网络损耗和改善电压质量为目标的分布式选址定容目标函数,并采用混合智能算法进行DG定容的优化计算.算例分析表明该方法在DG选址和定容问题中是有效的.     

分布式电源与配电网架多目标协调规划

分布式电源(DG)接入对配电网损耗、电压及可靠性指标有很大影响。针对当前DG与配电网架分开独立进行规划的问题,提出一种综合协调两者的规划方法。该方法能够实现DG位置及容量、线路升级改造、新增负荷点接入方案的综合优化,以设备投资成本、系统有功损耗、停电损失及购电费用4个指标最小为目标函数,利用判断矩阵获得各目标函数权重,通过加权将多目标优化转化成单目标优化问题,采用染色体分段编码方式、精英保留策略遗传算法进行求解。为了避免因DG可选布点太多导致算法计算速度慢的问题,根据配电网损耗、电压及可靠性指标改善效果,提出一种实用的确定DG候选位置的方法。算例仿真结果表明,提出的确定DG候选位置的方法能够有效缩小搜索空间,提高优化效率;对DG和配电网架进行综合协调规划,能够有效提升配电网投资的综合经济效益,获得的建设与改造方案更科学合理。     

含分布式电源的配电网滤波装置最优配置研究

正由于分布式电源(Distributed Generation,DG)中存在大量逆变器,加上配电网中已有的非线性负荷,电网中电压和电流质量受到很大的影响,尤其以谐波问题较为突出。提出了一种基于遗传算法和差分进化算法相结合的滤波装置优化配置方法,该方法以滤波装置费用和电能损耗费用之和最小作为优化目标,对含DG的配电网进行有源滤波器和无源滤波器的统一优化配置。所提出配置方法融合了两种算法的优点,将差分进化的思想加入遗传算法,充分利用了父代基因的信息,提高了计算准确度。仿     

基于多目标粒子群算法分布式电源的最优配置策略

随着各种可再生能源发电技术逐渐成熟,将多类型分布式电源（DistributedGeneration,DG）接入配电网（Distribution Network, DN）是促进电力系统能源转型的快捷方式。但是,大量的DG接入DN会导致DN运行稳定性下降,迫切寻找到解决方法。为此本文考虑了PV(Photovoltaic, PV)、风力发电（Wind Power Generation, WPG）和燃料电池（Fuel Cell, FC）三种DG,并以DG的经济性指标、电压偏差、电压波动以及网络损耗作为优化目标,采用多目标粒子优化算法（Multi-objective Particle Swarm Optimization, MOPSO）确定了三种DG接入DN的最优位置已经最佳容量,并与多目标蝗虫优化算法（Multi-objective Grasshopper Optimization Algorithm, MOGOA）进行了比较。基于IEEE-33节点仿真测试算例表明与未配置DG相比,通过MOPSO算法配置DG后,平均电压波动降低了0.055 p.u.(5.01%),网络损耗减少了646.65 ...     

基于隔离小生境粒子群算法的APF优化配置

随着非线性负载的广泛应用,传统负荷端分散的谐波治理方式弊端渐显。以中小型电网中有源电力滤波器的集中补偿配置为目标,设计一种基于隔离小生境粒子群算法的APF优化配置方法。建立了有源电力滤波器的优化配置数学模型,以节点电压畸变率均方根为目标函数,并使用罚函数处理约束条件。改进后的粒子群算法兼顾全局与局部寻优能力,避免陷入局部最优点。在阐述所提优化配置方法流程的基础上,IEEE算例分析表明该配置方法可以同时进行APF位置和容量的寻优,治理后系统各节点总谐波电压畸变率小于4%,谐波附加损耗降低90%以上,实现对单、多谐波源系统电能质量的有效治理。     

考虑配电网电压暂降治理经济性的DVR优化配置方法研究*

针对配电网电压暂降治理的有效性和经济性问题,提出一种动态电压恢复器经济配置的电压暂降治理方法。首先,对DVR不同容量时对应的投资成本进行分析,从而准确计算DVR配置方案的总投资。然后,基于电压暂降凹陷域,结合敏感负荷的中断概率对负荷进行经济损失评估,并根据系统有功损耗计算出总电压暂降经济损失成本。最后,构建了包含DVR装置的投资成本、电压暂降时敏感负荷经济损失和系统有功损耗三种要素的优化模型, 实现DVR的最优容量和接入位置。采用IEEE33节点标准测试系统为例对所提配置方法进行验证,仿真结果证明与传统的DVR就地接入的补偿方法相比,该方法能有效降低配电网电压暂降治理的总经济成本,在保证配电网的运行可靠性的同时提高经济效益。     

Multi criteria simultaneous planning of passive filters and distributed generation simultaneously in distribution system considering nonlinear loads with adaptive bacterial foraging optimization approach

This paper presents adaptive bacterial foraging optimization (ABFO) algorithm to optimize the planning of passive power filters (PPFs) and distributed generations (DGs) in distribution system with presence of heavy nonlinear load simultaneously. The amount of nonlinear load is assumed to be serious which enforced the system planner to utilize the PPFS. Also the power loss minimization, reliability and voltage profile improvement, and other benefits encouraged the planner to employ the DGs.Some of DG technologies, such as wind generators and solar cells are based on power electronic devices and inverter implementation. Connection of this type of DGs to system produces harmonic. Therefore the utilization of PPFs among existent capacitor busses for harmonic compensation is inevitable. The objective is to minimize the power loss, the total harmonic distortion (THD) and the investment cost of PPFs and DGs simultaneously. Constraints include the voltage limits and the limit candidate buses for PPFs and DGs installation. The harmonic levels of system are obtained by current injections method and the load flow is solved by the iterative method of power sum, which is suitable for the accuracy requirements of this type of study. It is shown that through an economical planning of PPFs and DGs, the total voltage harmonic distortion and active power loss could be minimized simultaneously.     

Influence of phasor adjustment of harmonic sources on the allowable penetration level of distributed generation

Harmonic distortion caused by increasing size of inverter-based distributed generation (DG) can give rise to power quality problems in distribution power networks. Therefore, it is very important to determine allowable DG penetration level by considering the harmonic related problems. In this study, an optimization methodology is proposed for maximizing the penetration level of DG while minimizing harmonic distortions considering different load profiles. The methodology is based on updating the voltage magnitude and angle at point of common coupling depending on the size of DG to be utilized in the harmonic power flow modeling. The harmonic parameters are determined by using decoupled harmonic power flow method, in which the harmonic source modeling with harmonic current spectrum angle adjustment is embedded, while the nonlinear loads and inverter-based DGs are connected to the distribution power network. The allowable penetration level of DGs is determined based on power quality constraints including total harmonic voltage distortion, individual harmonic voltage distortion, and RMS bus voltage limits in the optimization framework. Fuzzy-c means clustering method is also applied to decrease the computational effort of the optimization process in the long-term load profile. The effectiveness of the proposed method is illustrated on the IEEE 33-bus radial distribution network for different scenarios.     

Effect of network reconfiguration on power quality of distribution system

Effect of network reconfiguration on power quality issues of distribution system has been investigated. The problem of network reconfiguration is reformulated with an objective to improve the power quality of the distribution system. Along with the traditional objective of loss minimization, power quality related objectives such as minimization of harmonic distortion of the voltage waveform, minimization of voltage unbalances at the nodes and maximization of sag voltages are identified as the objectives of reconfiguration. Branch exchange technique has been used to establish each of the objectives. The problem has also been formulated as a multi-objective optimization problem. The multiple objectives are, however, incorporated into a single objective using weighting multipliers and branch exchange technique has been judicially applied to take care of all the objectives. It is found that network reconfiguration can be used as an effective tool to improve the power quality of distribution system. Besides, the distributed energy sources also have great impacts on distribution network, as their size and locations are found to have great importance on the power loss, voltage sag, voltage harmonic distortion and unbalance. The effectiveness of the network reconfiguration on power quality issues have been studied on 25-bus network and IEEE 33-bus network with and without presence of distributed generation and VAr sources.     

多DG不确定性建模及其对配电网谐波潮流的影响

分布式电源(DG)出力的随机性和间歇性导致其并网谐波电流具有不确定性,进而导致含DG配电网的谐波分布具有不确定性。为处理配电网谐波潮流计算中DG作为谐波源的不确定信息,以复仿射数代替点值,建立DG并网逆变器输出阻抗复仿射模型,该模型反映了直流侧电压源的不确定性对DG并网谐波电流的影响。在所提模型的基础上,改造传统确定性谐波潮流算法,提出含多DG配电网的不确定谐波潮流计算方法分析DG不确定性对谐波潮流的影响。采用典型33节点配电网算例进行仿真,与确定性分析方法计算结果的对比验证了所提方法的有效性和应用价值。     

抑制谐波的配电网无功优化规划

在配电网中,为进行无功优化以降低网损,装设了大量的电容器.这些电容器的装设,导致了在谐波频率下,容易产生系统与电容器之间的谐波谐振或谐波放大,从而使系统的谐波畸变率大为增加,破坏了系统的安全运行.针对这一问题,文中提出了谐波畸变情况下对配电网进行无功优化规划的模型,给出了用灵敏度指导遗传算法进行求解的具体步骤,并用VB编制了仿真程序,对实际配电网进行了仿真计算.计算结果表明,该模型能使电网在满足电压和谐波标准约束的情况下,系统网损和谐波畸变率均得到改善,且大大提高了寻优效率,验证了文中所提方法的有效性.     

基于IGSO计及谐波电压畸变的无功优化

近年来电力电子装置的广泛应用引起了谐波污染。如果直接对电力系统进行无功优化,谐波频率下容易产生系统与电容器之间的谐振或谐波放大,使系统的谐波畸变率大为增加,破坏系统的安全运行。针对这一问题,提出了计及谐波电压畸变的无功优化模型;在网损最小的基础上,将各节点基波电压和总谐波畸变率越限情况以惩罚项的形式加入目标函数中,将改进萤火虫算法（IGSO）应用到无功优化中,给出基于IGSO计及谐波电压畸变的无功优化具体步骤。通过对IEEE 30节点算例的仿真分析,验证本方法的可行性和优越性,在减小网损和总谐波畸变率的同时,提高了收敛速度和计算精度。     

交流微电网中考虑电压质量的DG之间谐波功率均分控制策略

在多节点微电网系统中,并联分布式电源(DG)在传统的对等控制下难以精确均分谐波功率且会对母线电压质量带来不利的影响。为此,基于两级式分层控制,提出了一种考虑电压质量的DG之间谐波功率均分控制策略。通过各DG之间的低带宽通信实现输出谐波功率信息的共享,根据获得的谐波功率信息动态重塑系统在谐波域的等效阻抗,能在提高谐波功率均分精度的同时兼顾母线电压质量。从谐波环流偏差、电压质量方面,将所提控制策略与已有的自适应虚拟谐波阻抗法进行对比分析。仿真和实验结果表明所提控制策略能够在均分谐波功率的同时,减小母线电压幅值跌落和总谐波畸变率,提高母线电压质量。     

Optimal shunt capacitor allocation by fuzzy dynamic programming

A new approach using fuzzy dynamic programming to decide the optimal location and size of compensation shunt capacitors for distribution systems with harmonic distortion is proposed. To decide the optimal capacitor placement, a fuzzy dynamic programming model in which the real power loss, voltage deviation, and harmonic distortion are all expressed in fuzzy set notation is developed. The problem is formulated as a fuzzy dynamic programming of the minimization of real power loss and capacitor cost under the constraints of voltage limits and total harmonic distortion. A simple algorithm that is based on the fuzzy set is proposed to determine an optimal solution. This algorithm greatly reduces the effort of finding the optimal location via an exhaustive search. A practical distribution system is selected for computer simulation to test the efficiency of the proposed fuzzy dynamic programming method. It is found that the system loss and harmonic distortion can be reduced very effectively by this proposed algorithm.     

Optimal Control of Voltage in Distribution Systems by Voltage Reference Management

Recently, renewable energy technologies such as wind turbine generators and photovoltaic (PV) systems have been introduced as distributed generations (DGs). Connections of a large amount of distributed generations may cause voltage deviation beyond the statutory range in distribution systems. A reactive power control of DGs can be a solution of this problem, and it also has a possibility to reduce distribution loss. In this paper, we propose a control methodology of voltage profile in a distribution system using reactive power control of inverters interfaced with DGs and tap changing transformers. In the proposed method, a one-day schedule of voltage references for the control devices are determined by an optimization technique based on predicted values of load demand and PV power generation. Reactive power control of interfaced inverters is implemented within the inverter capacity without reducing active power output. The proposed method accomplishes voltage regulation within the acceptable range and reduction of distribution loss. The effectiveness of the proposed method is confirmed by simulations. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.