基于连续潮流的配电网供电能力评估

随着非全相运行的分布式电源大量接入配电网,配电网固有的三相不平衡特征更加突出,传统配电网供电能力评估因忽略配电网三相不平衡特征导致结果不准确。为了准确分析三相不平衡特征对配电网最大供电能力评估的影响,建立了以配电网供电负荷参数最大为目标函数,考虑了支路热约束和节点电压等状态变量和分布式电源的有功和无功功率等控制变量的含分布式电源三相不平衡配电网供电能力评估模型。选择电压跌落情况最严重的相作为连续参数,确保预测-校正过程的的连续潮流法求解的结果更加精确。最后,采用拓展的IEEE33节点配电系统进行仿真验证,表明文中所提的模型和求解方法是有效的。     

基于高斯求积的智能配电网三相概率潮流点估计法

随着大规模风电、光伏和电动汽车的接入,智能配电网运行状态的不确定性大幅增加.文章通过分析不确定性变量的概率分布特征,提出一种基于高斯积分的概率潮流点估计法.该方法利用Gauss-Hermite求积与正态变换技术选取输入变量的估计节点和对应权重,通过多项式逼近方法估计多随机变量响应函数的输出变量统计矩.针对配电网参数不对...     

考虑不确定性的三相不平衡配网DG选址定容研究

可再生能源的分布式发电(Distributed Generation,DG)因其良好的环境效益受到关注,但分布式风力发电和光伏发电出力具有波动性和不确定性,这类分布式电源配置在网络中的节点位置和容量对于网络优化运行至关重要。由于配网中三相负荷经常不平衡,并且不同相之间的互阻抗也不平衡,这给分布式电源在配网中的选址定容带来了难度。考虑到三相不平衡潮流的影响,利用速度高、精度好为特点的考虑负荷模型和负荷接入类型的线性三相不平衡潮流法进行潮流计算。针对出力不确定的分布式电源在三相不平衡配网中的选址定容展开研究,建立了以减小网损、降低电压不平衡度、防止电压跌落的分布式电源多目标选址定容模型。针对分布式电源选址定容后的运行维护情况,提出了成本效益分析,来考虑中长期选址定容的合理性。为了求解文中的多目标模型,提出了改进磷虾群搜索算法,保留最优个体,提高收敛速度。利用IEEE37节点系统进行算例验证,分析了网损、电压不平衡度、每相电压在分布式电源接入后的情况。     

带蓄电池储能系统的DSTATCOM有功无功联合优化控制

蓄电池储能系统接入配电网静止同步补偿器(B-DSTATCOM)进行有功无功联合控制可有效缓解高波动性分布式电源大量接入配电网导致的电压越限、网损加重、三相不平衡度增加等系列问题。对此,文中提出一种计及光伏发电的不平衡主动配电网B-DSTATCOM实时有功无功联合优化控制策略。首先,对B-DSTATCOM四象限运行原理进行研究,在此基础上以电压偏移、网损、电压不平衡度及运行成本为子目标函数建立B-DSTATCOM实时有功无功联合多目标优化控制模型,并采用加权求和法、改进粒子群优化及直接潮流法求得最优控制方案。最后,基于澳大利亚某实际含光伏低压不平衡配电网进行MATLAB仿真,验证所提方法及模型的有效性、实用性和鲁棒性。     

The impact of single-phase grid-connected distributed photovoltaic systems on the distribution network using P-Q and P-V models

The gradual emergence of photovoltaic (PV) systems as the most common distributed generation interconnected with the electric power system calls for a detailed power flow analysis with different models especially in the evolving unbalanced active distribution network. This paper is an extension of a previous study carried out on the performance evaluation of a 10 kWp grid-connected PV system deployed in a school, with the grid providing a virtual storage and access to upstream markets. For increased adoption of such systems in the unbalanced distribution network, it is pivotal to understand the mode of operation and the type of connection to the system. This article presents an impact analysis of such utility interactive single-phase PV systems distributed on all the single-phase load nodes of the traditional IEEE-13 bus distribution test feeder. The PV distributed generation (PV-DG) can be modelled as constant P-Q or P-V nodes with varied impacts in power flow studies for the unbalanced active distribution network. Results from these models are compared in terms of their impacts on voltage profiles at load buses, voltage unbalance, equipment loading, power losses and the total number of iterations for a converged power flow solution.     

考虑配电网电能质量改善的分布式光伏优化调度方法

针对配电网中存在的电压越限、谐波畸变、三相不平衡等问题,从综合改善多电能质量问题的角度出发,研究了一种配电网分布式光伏优化调度模型及其求解方法。首先,分析了分布式光伏并网逆变器进行无功功率、谐波电流及不平衡功率补偿的控制方案;在此基础上,以可调度分布式光伏的三相功率及谐波电流输出为控制变量,基于配电网三相基波及谐波潮流方程,建立了最小化网络损耗、不平衡电压以及谐波电压的最优潮流模型;然后,提出了一种潮流计算与优化计算交替迭代的两阶段优化求解算法,对非凸非线性的最优潮流模型进行变量削减,并将其转换为凸二次约束二次规划模型从而实现高效求解;最后,通过一个162节点三相配电网进行算例分析,结果表明,根据最优潮流模型结果对分布式光伏进行调度后,配电网谐波畸变、三相不平衡以及电压越限问题得到了有效改善,且两阶段优化求解算法的计算效率也满足配电网调度时间要求,验证了所提分布式光伏优化调度方法在改善配电网电能质量方面的有效性。     

考虑配电网电能质量改善的分布式光伏优化调度方法

针对配电网中存在的电压越限、谐波畸变、三相不平衡等问题,从综合改善多电能质量问题的角度出发,研究了一种配电网分布式光伏优化调度模型及其求解方法。首先,分析了分布式光伏并网逆变器进行无功功率、谐波电流及不平衡功率补偿的控制方案;在此基础上,以可调度分布式光伏的三相功率及谐波电流输出为控制变量,基于配电网三相基波及谐波潮流方程,建立了最小化网络损耗、不平衡电压以及谐波电压的最优潮流模型;然后,提出了一种潮流计算与优化计算交替迭代的两阶段优化求解算法,对非凸非线性的最优潮流模型进行变量削减,并将其转换为凸二次约束二次规划模型从而实现高效求解;最后,通过一个162节点三相配电网进行算例分析,结果表明,根据最优潮流模型结果对分布式光伏进行调度后,配电网谐波畸变、三相不平衡以及电压越限问题得到了有效改善,且两阶段优化求解算法的计算效率也满足配电网调度时间要求,验证了所提分布式光伏优化调度方法在改善配电网电能质量方面的有效性。     

Development of equipment models for fast distribution three‐phase unbalanced load flow calculation

This paper presents distribution system equipment models for fast distribution three‐phase unbalanced load flow calculation. Recently, the number of distributed generators introduced into distribution systems has been increasing and detailed system analysis using load flow calculation has been eagerly awaited. Moreover, since many distribution system loads are composed of single phase loads, three‐phase unbalanced load flow calculation is required for the distribution system analysis. Although the fast distribution three‐phase unbalanced load flow calculation has been developed, equipment models considering interconnection of distributed generators have not as yet been developed in Japan. This paper develops practical equipment models such as various distributed generators, voltage control equipment, and loads for fast three‐phase unbalanced load flow calculation in distribution systems. The feasibility of the developed models is verified and demonstrated on practical distribution system models with promising results. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(3): 8–19, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10106     

含分布式电源的三相不平衡配电网连续潮流计算

连续潮流是电力系统电压稳定分析的重要工具。针对含不同类型分布式电源的配电网及其三相线路参数和负荷不平衡的情况,提出了一种三相配电网连续潮流方法,由切线预测环节和牛顿法校正环节组成,并采用局部几何参数化策略处理三相不平衡系统PV曲线的斜锐角现象。考虑了PV和PQ节点类型分布式电源的限值约束,给出了新的节点类型双向转换逻辑和分岔点类型识别方法。通过对IEEE 33节点配电系统进行算例仿真,表明所述算法可以有效追踪三相配电系统的PV曲线,准确计算电压稳定临界点并识别分岔点类型。     

A three-phase power flow method for real-time distribution systemanalysis

This paper presents a three-phase power flow solution method for real-time analysis of primary distribution systems. This method is a direct extension of the compensation-based power flow method for weakly meshed distribution systems from single phase to three-phase, with the emphasis on modeling of dispersed generation (PV nodes), unbalanced and distributed loads, and voltage regulators and shunt capacitors with automatic local tap controls. The method proposed here is capable of addressing these modeling challenges while still maintaining a high execution speed required for real-time application in distribution automation systems. The paper also includes test results from the application of a computer program developed based on the proposed method to large primary electric distribution systems     

基于正序分量的含PV节点的三相配网潮流算法

随着分布式发电(distributed generators,DG)接入配电网,传统的配电网潮流算法难以满足分布式发电系统潮流计算的要求。针对这一情况,提出一种有效的三相不平衡配电网潮流直接算法,该算法充分利用配电网络的结构特点,基于回路分析法生成的道路矩阵,建立节点电压与注入电流之间的关系矩阵,从而实现配网潮流的直接计算。同时,基于PV节点正序电压幅值保持恒定的特性,提出一种新的处理PV类型DG的方法,该方法基于正序分量方法和道路矩阵,推导得到无功电流和补偿电压之间的关联公式,可非常简单地引入到三相不平衡配网潮流计算算法中,并保证PV节点有功功率和电压幅值为预设定值(假定无功功率没有越界)。通过6母线和69母线算例验证该方法的有效性和通用性。     

含分布式光伏发电的中压配电网电压控制策略

随着分布式光伏发电并网规模的不断扩大,由光伏发电功率与负荷之间不平衡引发的逆向潮流导致的电压越限问题日益受到关注。在光伏接入点的电压分析及无功/有功调压分析的基础上,提出了无功/有功协调控制策略,通过光伏逆变器的无功输出补偿及光伏发电量优化管理,实现配电网节点电压的控制。仿真分析结果表明,该策略能在兼顾光伏利用效率和经济性的同时,较好地解决含分布式光伏发电的配电网的电压越限问题。     

考虑分布式光伏电源接入模式的低压配电网不平衡线损计算方法

日益增加的户用光伏发电系统改变了配电网的潮流分布,同时对配电网的线损产生显著影响。为了便于量化分布式光伏电源(distributed photovoltaic generation,DPG)接入三相四线制低压配电网的运行经济性,文章以三相不平衡线损为研究目标,首先建立了适用于低压配电网平衡态和不平衡态的线损计算模型;通过引入DPG接入模式、位置及容量3种要素,建立DPG不同接入模式下的线损变化量模型;以此为基础,提出一种考虑DPG接入模式的有源低压配电网的三相不平衡线损计算方法。在进行计算时,所提方法既可利用实时电流数据,也可利用易采集到的有功电量数据进行计算。最后,以低压配电网的典型参数为例验证了该方法的准确性与可行性,说明此方法可为DPG单相、三相接入低压配电网的线损计算提供参考依据。     

基于数据潮流模型的高比例光伏配电网三相不平衡优化

随着分布式光伏的大规模接入,配电网固有的三相不平衡问题日益严重,给系统的电能质量、经济运行等带来不利影响。此外,高比例光伏的接入使得配电网的物理结构和运行方式更加复杂多变,导致当前依赖精确拓扑结构和线路参数的三相不平衡优化方法难以应用。因此,提出一种基于数据潮流模型的高比例光伏配电网三相不平衡优化方法。首先,采用基于双阶段注意力机制的循环神经网络方法建立数据潮流模型,拟合三相潮流约束中变量之间的函数关系。同时,提出图特征嵌入的方法将部分已知的拓扑信息嵌入到数据潮流模型中以提高拟合精度。其次,以训练后的数据潮流模型为基础重建配电网三相不平衡优化模型。最后,通过条件梯度下降方法求解该模型,以修改的IEEE33节点配电网络为例,验证了所提方法的有效性。     

Development of Three-Phase Unbalanced Power Flow Using PV and PQ Models for Distributed Generation and Study of the Impact of DG Models

With the increased installations of distributed generators (DGs) within power systems, load flow analysis of distribution systems needs special models and algorithms to handle multiple sources. In this paper, the development of an unbalanced three-phase load flow algorithm that can handle multiple sources is described. This software is capable of switching the DG mode of operation from constant voltage to constant power factor. The algorithm to achieve this in the presence of multiple DGs is proposed. Shipboard power systems (SPS) have other special characteristics apart from multiple sources, which make the load flow difficult to converge. The developed software is verified for a distribution system without DG using the Radial Distribution Analysis Package (RDAP). The developed software analyzes an IEEE test case and an icebreaker ship system. System studies for the IEEE 37-node feeder without the regulator show the effect of different models and varying DG penetration related to the increase in loading. System losses and voltage deviations are compared.     

基于RBF神经网络和无迹变换法的三相概率潮流计算

不平衡负荷、不对称网络参数以及可再生能源的接入,引入了三相概率潮流.文中提出了一种新的三相概率潮流计算方法,将RBF神经网络与无迹变换法结合求解三相概率潮流.首先根据无迹变换法,利用输入变量均值和协方差矩阵求出输入变量的Sigma向量以及相应权重.其次,采用RBF神经网络求解潮流非线性方程,得到输出变量的均值以及相应权重.所提方法适用于输入变量相关的情况,且无需求解雅可比矩阵及其逆矩阵,加快了计算速度.最后,在不平衡25节点系统上进行仿真,结果表明了所提算法的有效性和实用性.     

基于电压幅值对数变换的配电网三相不平衡线性潮流计算

线性潮流计算方法可为主动配电网分析与运行调控提供更好的鲁棒性与更高的效率.提出一种新的三相不平衡线性潮流计算方法.在极坐标下将三相潮流方程的电压幅值进行对数变换,然后根据三相配电网实际特点进行合理的线性近似.所提方法可以无须迭代直接计算配电网辐射状、弱环状和含PV节点3种情况的三相不平衡潮流.通过IEEE33三相不平衡...     

负荷电压静态特性的含分布式电源的前推回代潮流计算

分布式电源并网后,配电网中出现了新的节点类型,使得传统的前推回代法不能解决含分布式电源的配电网潮流计算。在考虑恒功率、恒电流及恒阻抗的负荷电压静态特性的情况下,提出了改进的前推回代法对不同分布式电源进行潮流计算。该算法针对风力发电、光伏电池、燃料电池及燃气轮机,分别建立了数学模型,并且在处理PV节点时,通过无功分摊原理设定无功初值,采用无功补偿装置进行功率修正;针对辐射状配电网特征,采用搜索叶节点的方法,形成了便于前推及回代计算的参数矩阵。通过IEEE33配电系统验证表明,提出的方法收敛性能强,能有效解决含不同分布式电源的潮流计算。     

基于概率潮流法的含分布式光伏的配电网电压状态评估

为克服高渗透分布式电源接入所导致的传统配电网运行状态评估方法存在盲区的困难,对计及分布式电源随机特性的配电网电压质量的状态定量评估方法进行研究。首先引入一种半不变量结合Gram-Charlier级数展开的概率潮流计算方法,并建立含系统电压平均越限概率、节点电压置信区间和节点电压最大越限概率指标的评估体系。然后以分布式光伏为代表,构建了其有功出力服从Beta分布的概率模型,并定义一种改进的计及光伏波动特性的光伏渗透率指标,由此定量评估不同光伏渗透率对配电网电压质量的影响。最后验证该算法用于配电网电压质量状态评估的可行性。     

Computation of locational and hourly maximum output of a distributed generator connected to a distribution feeder

Recently, the total number of distributed generation such as photovoltaic generation systems and wind turbine generation systems connected to a distribution network has drastically increased. Distributed generation using renewable energy can reduce the distribution loss and emission of CO₂. However, the distribution network with the distributed generators must be operated while maintaining the reliability of the power supply and power quality. In this paper, the authors propose a computational method to determine the maximum output of a distributed generator under operational constraints [(1) voltage limit, (2) line current capacity, and (3) no reverse flow to bank] at arbitrary connection points and hourly periods. In the proposed method, a three‐phase iterative load flow calculation is applied to evaluate the above operational constraints. The three‐phase iterative load flow calculation has two simple procedures: (Procedure 1) addition of load currents from the terminal node of the feeder to root one, and (Procedure 2) subtraction of voltage drop from the root node of the feeder to terminal one. In order to check the validity of the proposed method, numerical simulations are performed for a distribution system model. Furthermore, the characteristics of locational and hourly maximum output of a distributed generator connected to a distribution feeder are analyzed using several numerical examples. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(2): 38–47, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20610