Probabilistic and Multi-Objective Placement of D-STATCOM in Distribution Systems Considering Load Uncertainty

Advanced technologies such as distribution static compensator (D-STATCOM) are broadly deployed in distribution systems (DSs) to tackle different issues. Successful deployment of such technologies requires their adaption to stochastic nature of DS. This paper proposes a new method for allocation of D-STATCOM in DSs considering load uncertainty. Monte Carlo simulation (MCS) technique is utilized to cope with uncertain attribute of loads. To do so, output of MCS is considered as a deterministic case which is solved by backward-forward sweep power flow approach. The objective functions of the proposed model include total voltage deviation, total active losses, and voltage stability metrics. These metrics are combined in a multi-objective optimization formulation and solved by non-dominated sorting genetic algorithm-II (NSGA-II). Lastly, the best compromise solution is determined by Pareto front technique taking advantage of fuzzy decision making (FDM) engine. Comprehensive simulation studies are carried out on IEEE 33-bus standard distribution system as well as on Portuguese 94-bus real-world distribution system. Simulation studies confirm the accuracy of the proposed method in determining proper location of D-STATCOM in DSs by fulfilling the objectives.     

Multi-objective optimal charging of plug-in electric vehicles in unbalanced distribution networks

Plug-in electric vehicles (PEVs) as new generations of transportation systems have recently become a promising solution to mitigate emissions of greenhouse gases produced by petroleum-based vehicles. Existing power systems may face serious reliability and power quality problems in supplying emerging PEV charging loads unless the charging task is coordinated. In addition, in real world applications, most PEVs are single-phase loads supposed to be charged from residential or commercial outlets. In this paper, a multi-objective optimization framework is proposed to optimally coordinate the charging of single-phase PEVs with dynamic behavior in unbalanced three-phase distribution systems employing smart grid facilities. Objective functions include total cost of purchasing energy in a multi-tariff pricing environment as well as grid total energy losses over charging span. The objective functions are optimized subject to network security, power quality, and PEV constraints. Fuzzy memberships are used to transform differently-scaled objective functions into a same range in order to ensure the Pareto optimality of the multi-objective solution. The proposed method is tested on an unbalanced three-phase distribution system and obtained results, which are discussed in detail, confirm its efficiency in getting a solution satisfying both objective functions as well as in the speed.     

基于充电设备利用率的电动汽车充电路径多目标优化调度

由于电动汽车车主选择充电站具有较大的随机性,使得各充电站的利用率存在较大的差异,从而造成整个电网的负荷失衡,影响配电网的稳定性和安全性。针对上述问题,将行驶路程最近、时间最短、充电站时间利用率偏差最小和功率利用率偏差最小作为优化目标,建立了电动汽车充电路径多目标优化调度模型。在对该模型进行求解的过程中,提出了基于细菌趋化的改进粒子群算法进行求解。仿真结果表明,采用该算法后,电动汽车车主可以根据区域内充电站的利用率情况有目的选择充电站,实现均衡化充电站利用率的目的。     

改进粒子群算法在船舶电力系统网络重构中的应用

船舶电力系统网络重构本质上是带约束的多目标组合优化问题.针对船舶电网重构问题的特点,建立了船舶电力网络的无向图模型;在此基础上,进一步建立了以负荷恢复量、开关操作次数和发电机效率均衡性为优化目标的船舶电力系统多目标重构模型:提出了一种结合"背包策略"和模拟退火算子的改进粒子群算法进行求解.其中"背包策略"可以明显提高粒...     

Probabilistic Multi-objective Framework for Multiple Active Power Filters Planning

In the real-world electrical distribution networks, entering of the non-linear loads, as main sources of harmonic generator, has probabilistic nature. In this paper, with a new point of view, a multi-objective framework is developed for multiple active power filters (APFs) with taking probabilistic features of non-linear loads into account. In the proposed probabilistic multi-objective framework, total harmonic distortion of voltage (THDV), motor load loss function, harmonic transmission line loss, and total APFs current are the four objectives considered in the optimization problem. At the same time, individual and THDV, and maximum allowable size of the APFs are modeled as constraints with predetermined admissible levels. The newly developed framework is a non-convex non-linear mixed-integer optimization problem. Hence, a new hybrid of melody search algorithm and augmented Powell heuristic method is employed and followed by a fuzzy satisfying method to obtain the final optimal solution. The feasibility and effectiveness of the offered framework has been implemented on the IEEE 18-bus distribution test system and IEEE 30-bus distribution test system. The obtained results show the profitableness of the newly developed framework in the APFs planning.     

分布式电源对配电网的影响及优化配置模型

随着用电负荷的急剧增长,分布式发电成为了当今电力系统的研究热点。为了更好地发挥分布式电源的经济效应,本文首先对分布式电源接入电网后对传统配电网的影响作了分析研究。在此基础上,建立了电源的优化配置模型,确立了以减少节点电压偏移量、降低系统损耗量和提高并网电压稳定度的多目标函数优化模型,并利用自适应混沌粒子群算法进行函数求解。最后通过算例分析,验证了模型的实际效果和求解算法的准确性。     

采用改进温湿度变量策略的夏季短期负荷预测方法

为了充分考虑温度和湿度变量对夏季电力负荷的综合影响,提出一种改进的基于温湿度多形式变量的夏季短期负荷预测方法。首先通过分析夏季气象因素对负荷变化的影响,构造了三种不同形式的温湿度变量作为模型输入变量。然后根据周特性变化对负荷进行分层,对各层负荷建立基于LASSO回归的预测模型,并通过枚举搜索求解算法对输入变量进行选择,优化预测模型。最后通过计算剩余变量对应的系数从而进一步估计出各时段负荷的分布。算例结果表明该方法能有效提高模型的预测精度及鲁棒性。     

自适应免疫粒子群算法在动态无功优化中应用

根据电力系统实际运行中负荷不断变化的情况,提出了动态无功优化问题的完整数学描述和计算方法。从负荷曲线的特点出发,结合设备动作次数约束,提出利用遗传算法进行智能化负荷分段的方法。利用引入免疫系统的免疫信息处理机制和自动调整动量系数的自适应因子的粒子群算法,从整体上获得系统的最优控制方式。IEEE 30节点系统算例分析表明,该方法有效减少了补偿设备和变压器分接头的动作次数,其中节点12电容器组的投切次数由6次降为2次,且系统在一天内的有功损耗由1.2413p.u.降为1.1554p.u.。     

电动汽车两阶段多目标有序充电策略研究

大量随机性电动汽车充电负荷的接入会对电网安全经济运行等方面产生不利的影响。在统计电动汽车用户出行规律、起始充电时刻等行为基础上,分析了充电站的充电负荷特性。在考虑配电设备运行安全和用户充电需求的前提下,综合充电负荷和原有负荷的特点,建立了以分时电价为基础、以减小负荷波动率和提高运营商效益为目标的两阶段多目标充电模型。提出了基于多种群遗传算法的两阶段多目标优化模型求解方法和有序充电控制策略。以小区充电站为例,验证了两阶段多目标有序充电控制策略在减小负荷波动率、削峰填谷、降低经济成本提高运营商效益等方面的作用。     

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.     

基于GA-PSO的电动汽车换电站时空双层充电优化策略

针对电动汽车(Electric Vehicle, EV)用户换电体验不佳、换电站备用电池组空闲、充电成本过高及配电网负荷特性恶化的问题,建立了兼顾EV用户、换电站和电网公司三方利益的时空双层充电优化模型。该模型采用双层时空解耦结构,上层模型以满足EV用户个性化需求为目标,重点解决空间尺度上换电站的选择问题。下层模型在时间尺度上采用一种两阶段优化策略,第一阶段以充电成本最小为目标重点关注电池组充电方案的制定问题,第二阶段虑及电网激励以配电网负荷波动最小和峰谷差最小为目标重点关注充电方案的优化问题。最后,采用Monte Carlo法模拟EV用户的换电需求,采用GA-PSO(遗传-粒子群算法)对提出的时空双层优化模型进行迭代求解。以某典型城区为例,仿真验证了所提模型与方法的正确性。     

一种新型的电力系统无功优化算法

介绍一种类似于遗传算法的进化算法———粒子群优化算法, 并把它应用到电力系统无功优化问题中。对基本的粒子群优化算法作了适当改进, 在粒子速度更新公式中增加了一项即上一代的全局“最优”值, 相当于增加了全局极值的权重, 提高了算法的收敛性。以粒子群优化算法为基础, 选取适合于该算法的无功优化目标函数。通过对 IEEE- 14节点的仿真计算, 证明了该算法优于基本的粒子群优化算法, 且与遗传算法相比能在更少的迭代次数内搜索到更好的全局最优解。     

基于无迹变换随机潮流建模的主动配电网优化调度

为了解决风电和电动汽车大量接入主动配电网所引发的随机优化调度问题,利用基于无迹变换的随机潮流计算方法处理风电出力的波动性、电动汽车充电的随机性以及电网负荷的随机波动。进而建立了以电动汽车充电功率和分布式电源出力为优化变量,以配电网运行费用最小、有功网损最小和负荷方差最小为优化目标的主动配电网随机优化模型。同时,采用多目标粒子群算法对模型进行求解,并以改进的IEEE 33节点测试系统为例对该模型进行仿真。仿真结果表明:考虑不确定性和电动汽车有序充电的优化调度模型,可以有效地减少配电网运行的成本、降低网损和缩小峰谷差,验证了所提模型的正确性和有效性。     

SFOA算法在电力系统多目标无功优化的应用

电力系统由于无功分布不合理引起的事故越来越多。以系统网损、电压平均偏离、电压安全稳定裕度3个指标建立无功优化模型,引入了动态罚函数体现状态变量约束在优化过程的影响,并用个人偏好约束下的权值分配方法根据用户的需求对各个指标分配权值,采用SFOA算法求得电力系统多目标无功优化在可行域内的最优解。从SFOA算法和PSO算法运用于IEEE 30和IEEE 57节点系统优化结果比较表明:所提出的算法是可行有效的。     

基于改进粒子群优化算法的DG准入容量与优化布置

为进一步优化配电网中分布式电源（distributed generation,DG）的准入容量和优化布置问题,以节点电压和线路载流量为约束条件建立了单电源和多电源准入容量的数学模型,以有功网损最小为目标函数建立了DG优化布置模型。为有效求解该模型,采用了基于粒子群优化（particle swarm optimization,PSO）算法和二次插值相结合的改进PSO算法,将该改进方法应用于IEEE 33节点标准算例,分别进行了DG的最优接入位置与最优容量的仿真,并与粒子群算法优化结果进行了对比,同时还分析了优化布置下的潮流分布。算例仿真结果表明该方法可有效减少DG接入后配电网的网损,提高配电网的供电质量。     

Novel FGbSA: Fuzzy-Galaxy-based search algorithm for multi-objective reconfiguration of distribution systems

Reconfiguration according to different criteria is an important problem in distribution systems. This paper presents a new method for optimal multi-objective reconfiguration of distribution system based on the Galaxy-based Search Algorithm (GbSA). To avoid the convergence problem, the input and output data are normalized in the same range using fuzzy sets. The main objectives of the proposed algorithm have been considered as power loss reduction, voltage profile improvement and increase of the system load balancing. The proposed technique has been investigated using the IEEE 33-bus test system and a real distribution network i.e. Tai-Power 11.4-kV distribution system. The obtained results revealed the superiority of the proposed fuzzy-GbSA method in terms of accuracy compared to the GbSA and other intelligent search algorithms such as Genetic Algorithm (GA) or Particle Swarm Optimization (PSO). Furthermore, the proposed algorithm efficiently converged to the optimum solution compared to the other intelligent counterpart algorithms.     

Day-ahead optimal charging/dischargingscheduling for electric vehicles inmicrogrids

Microgrid as an important part of smart grid comprises distributed generators (DGs), adjustable loads, energy storage systems (ESSs) and control units. It can be operated either connected with the external system or islanded with the support of ESSs. While the daily output of DGs strongly depends on the temporal distribution of natural resources such as wind and solar, unregulated electric vehicle (EV) charging demand will deteriorate the unbalance between the daily load curve and generation curve. In this paper, a statistic model is presented to describe daily EV charging/discharging behaviors considering the randomness of the initial state of charge (SOC) of EV batteries. The optimization problem is proposed to obtain the economic operation for the microgrid based on this model. In dayahead scheduling, with the estimated power generation and load demand, the optimal charging/discharging scheduling of EVs during 24 h is achieved by serial quadratic programming. With the optimal charging/discharging scheduling of EVs, the daily load curve can better track the generation curve. The network loss in grid-connected operation mode and required ESS capacity in islanded operation mode are both decreased.     

Impacts of high penetration level of fully electric vehicles charging loads on the thermal ageing of power transformers

This paper develops a methodology to determine the impacts of high penetration level of fully electric vehicles (FEVs) charging loads on the thermal ageing of power distribution transformers. The method proposed in this paper is stochastically formulated by modelling the transformer life consumption due to FEVs charging loads as a function of ambient temperature, start time of FEVs charging, initial state-of-charge and charging modes. FEVs loads are modelled using the results from an analytical solution that predicts a cluster of FEVs chargers. A UK generic LV distribution network model and real load demand data are used to simulate FEVs’ impacts on the thermal ageing of LV power distribution transformers. Results show that the ambient temperature, FEVs penetration level, and start time of charging are the main factors that affect the transformer life expectancy. It was concluded that the smart charging scenario generally shows the best outcome from the loss of life reduction perspective. Meanwhile, public charging which shifts a large percentage of charging load to commercial and industrial areas can significantly alleviate the residential transformer loading thus has little impact on the loss of life of transformers. The proposed method in this paper can be easily applied to the determination of the optimum charging time as a function of existing loads, and ambient temperature.     

考虑负荷不确定性的多目标交直流系统无功优化

提出了一种考虑负荷不确定性的多目标交直流系统无功优化方法,研究负荷模型的不确定性对交直流系统无功优化的影响。本文将系统有功损耗最小、系统电压稳定裕度最大作为目标函数,基于负荷误差的正态分布特征,并利用二层规划理论方法,建立考虑负荷不确定性的多目标交直流系统无功优化数学模型。针对交直流无功优化非线性、多变量、多约束的特点,采用内点法和遗传算法相结合的混合优化算法求解上层模型,下层模型采用实数编码的改进遗传算法求解。采用基于IEEE30标准节点改进的交直流算例对提出的方法进行验证,结果验证了本文提出方法的可行性及有效性。     

电力电子变压器在有源配电网无功优化中的应用

尽可能地降低配电网中节点电压的偏差,是配电网运行的基本要求。为实现对节点电压的有效控制,提出利用电力电子变压器通过对其一次侧和二次侧电力电子变换器的脉宽调制控制(Pulse Width Moderation, PWM),改变其一次侧和二次侧潮流的方法加以解决。为此,构建了含分布式电源、储能元件和电力电子变压器在内的有源配电网无功优化模型,并运用粒子群优化算法进行求解。仿真结果表明,含电力电子变压器的有源配电网无功优化后的网损,低于采用有载调压变压器(On-Load Tap Changer, OLTC)对应网络无功优化后的网损;且其节点电压与额定值的相对偏差也优于后者,从而说明了在有源配电网中应用电力电子变压器,利用其灵活的无功调节功能,能提高配电网的运行水平。