基于内点法-退火因子法的主动配电网无功优化

大规模分布式电源(distributed generation,DG)接入主动配电网对配电网的潮流、节点电压和网络损耗有很大的影响。在主动配电网(active distribution network,ADN)中,具有一定的无功调节能力。本文研究了风力发电、光伏发电和其他DG的有功功率与无功功率的关系,结合传统的电压调节方法,对有源配电网的潮流进行了优化。根据DG的有功功率预测,动态调整DG的无功出力,以保持局部电压稳定,实现最优分配。目标函数由总网络损耗和离散变量罚函数构成,以电压无功调节能力为约束条件,将配电网无功优化问题建立为一个混合整数优化问题;采用内点法和罚函数法相结合的方法处理离散变量,在目标函数中引入连续可微改进的高斯罚函数,在高斯罚函数加入模拟退火因子,使目标函数跳出局部最优而获得全局最优,并将混合整数优化问题转化为连续问题求解。以光伏发电和风力发电为例,说明无功优化可以减少网络损耗,有效改善配电网的性能。     

一种功率动态调整的光伏逆变器调压方法

越来越多的光伏电源接入配电网，导致在光伏有功出力较大时并网点电压升高甚至越限，严重影响了配电网的安全。针对由于光伏并网造成的电压越限问题，文中分析了电压越限机理，研究传统无功调压策略；在此基础上，融合有功限值确定方法，提出了基于功率动态调整的光伏逆变器调压方法，不同工况下光伏逆变器采用相应控制策略，实现逆变器有功输出最大、无功输出最佳。通过仿真验证了调压方法的有效性。     

基于光伏电站有功出力DE求解的无功优化控制策略

文章在分析光伏电站的有功出力对其无功电压和有功损耗影响的基础上,综合考虑光伏逆变器和SVG的无功调节能力,提出一种基于光伏电站有功出力的无功优化控制策略。以光伏电站内部电压偏差最小和有功损耗最小为优化目标建立多目标优化模型,运用模糊理论将其处理为单目标优化模型,最后采用差分进化算法进行求解。经算例仿真,验证了所提策略的可行性和优越性。     

基于两阶段优化的主动配电网有功无功协调调度方法

分布式可再生能源出力的不确定性和主动配电网的有功、无功相互耦合,都会影响主动配电网的安全经济运行。文章提出了两阶段随机优化的主动配电网有功、无功协调调度方法,在考虑电力市场电价及保证配电网安全运行的前提下,最小化配电网主体的运行费用,采用二阶锥松弛和线性化技术将主动配电网的有功、无功优化转化为混合整数二阶锥凸优化,以快速求解。最后,以IEEE 33节点辐射型配电网为例,验证了所提模型能够有效处理风光随机性,通过有功无功的协调优化保证配电网的安全稳定运行。     

光伏逆变器无功调节能力分析与控制策略研究

通过建立光伏逆变器接入配电网稳态分析模型,以接入点运行电压、最大运行电流和SPWM调制控制条件为约束,分析了不同工况下逆变器的无功调节能力。构建接入配电网运行时面向电网电压调整的无功功率控制策略,该策略以控制接入点电压为目标,逆变器通过补偿系统需求的无功对电压进行支撑。构建分布式光伏接入配电网应对配电网负荷变化和光伏注入功率变化引起的电压无功调整仿真实验,验证了该策略的有效性。     

基于改进布谷鸟算法含光伏电站的无功优化

针对光伏电站并网运行给配电网无功优化带来的问题,根据光伏发电的运行特性,构建了含光伏电站的配电网无功优化数学模型,并提出改进的布谷鸟算法求解无功优化模型的方法,对含光伏出力的IEEE 33节点配电系统进行无功优化。结果表明,所提出的改进算法能有效降低配电网的有功网损,各节点远离电压崩溃点。     

抑制DPVG接入低压配电网电压波动的方法

为抑制分布式光伏(DPVG)接入低压配电网产生的电压波动,提出一种有功无功协调控制策略。根据DPVG接入低压配电网等效电路,分析并网点电压波动机理;结合抑制电压波动要求给出并网逆变器的功率调节范围;提出一种逆变器PQ参考值设置方案,并结合PQ功率解耦实现有功无功协调控制。搭建仿真模型,针对晴天、多云、阴天、小雨4种天气类型进行验证。结果表明,该方法能有效抑制DPVG接入配电网产生的电压波动。     

计及本地负荷的分布式光伏并网电压协同控制策略

光伏逆变器的剩余容量利用在解决分布式光伏发电系统并网点电压越限问题时取得了较好的效果，但目前为了提升逆变器的无功容量，相关研究主要集中在限制逆变器有功输出，未考虑对分布式光伏发电系统渗透率的影响。阐明分布式光伏发电系统并网点电压越限机理，提出一种计及本地负荷的分布式光伏并网点电压协同控制策略。通过背靠背变流器控制光伏发电本地负荷无功，通过控制并网逆变器工作状态改变光伏发电输出功率。设置制动控制环节，出现越限现象时优先采取本地负荷无功控制调节并网点电压，避免对配电网消纳光伏发电能力的影响。最后基于Matlab/Simulink仿真平台进行试验验证了所提控制策略的可行性与有效性。     

基于DistFlow的含分布式电源配电网优化重构模型

从数学优化的角度研究了含分布式电源配电网重构的二阶锥规划模型。首先建立以配电网络有功损耗最小化为目标的优化模型,并采用凸松弛的DisFlow模型描述配电网的潮流方程;采用基于生成树的配电网连通性约束,并与配电网辐射状的必要性条件一起组合为辐射状配电网连通性的充要条件;将DisFlow中的节点电压约束用大M约束进行松弛,避免增加冗余优化变量。通过算例验证了所提方法的有效性。     

主动配电网的多时段网损优化模型

分布式电源的快速发展、储能与无功调节装置的广泛应用使传统配电网进化为主动配电网,合理调控主动配电网运行状态,在接纳新能源的同时降低网络损耗能有效提高电网运行经济性.以全网有功损耗最小为目标,提出了一种主动配电网的多时段优化模型.首先,介绍了二阶锥规划理论及其特性.其次,基于distflow支路潮流方程,将储能、分布式电源、无功调节装置的运行纳入模型约束,构建了配电网多时段最优潮流模型.最后,基于改进IEEE-33节点系统的算例验证了所提模型能有效降低网络损耗.     

Smart grid adds to renewable resources hosting capacity: Collaboration of plug‐in hybrid electric vehicles in Volt/VAr control process

This paper develops an efficient energy management approach to increase the renewables share in energy provision of smart distribution grids (SDGs). Voltage violation ends in curtailment of renewables generations and, hence, decreases the economic success of distribution companies. To avert such deficits, this study fosters the collaboration of SDG components in an intelligent Volt/VAr control process. The investigated SDG is characterized with high penetration of photovoltaics (PVs), dispatchable distributed generations (DDGs), plug‐in hybrid electric vehicles (PHEVs), and infield control devices say as under‐load tap‐changing transformers (ULTCs). In charge stations, PHEVs are coupled to the SDG through bidirectional inverters which are offering simultaneous exchanges of active and reactive powers. Thus, regarding the PHEV aggregators, optimal schedules of active power charge/discharge signals with their inductive/capacitive reactive power provisions are determined. This notion effectively increases PV power injections and, consequently, provides significant monetary savings. Besides, this mechanism reduces ULTC tap operations in Volt/VAr control process maintaining its nominal lifetime. The proposed approach is formulated as a mixed‐integer non‐linear programming (MINLP) and solved based on DICOPT solvers in general algebraic modeling system (GAMS). Effectiveness of the proposed approach is explored on a typical distribution test system. The obtained results show 8.94% increment in harvested PVs power and hence 5.24% reduction on daily operation cost of SDG.     

Can PV plants provide a reactive power ancillary service? A treat offered by an on-line controller

This paper proposes an auto-adaptive controller that enables to suitably manage the reactive power supplied by the inverters of PV units whishing to provide the reactive power ancillary service on the base of standard needs or on a voluntary basis. The derived controller is based on an optimization procedure involving the sensitivity theory in conjunction with the Lyapunov function and provides control laws feeding the inverters of the PV units. The controller promptly minimizes system losses preserving the active power produced by the PV plants against the reactive one. In fact, when the PV modules do not get enough sunlight to generate active power, the proposed procedure forces the PV inverters to provide a reactive power equal to the rated power. On the contrary, in order to preserve the major economic benefits for the investor deriving from the produced active power during the sunlight hours, the method automatically reduces the injection of reactive power. The computer simulations, performed on a distribution system, demonstrate that the controller is capable to control the network in the real-time, mainly due to its ability to be auto-adaptive at any changes in the system operating conditions.     

State coordinated voltage control in an active distribution network with on-load tap changers and photovoltaic systems

Decreasing costs and favorable policies have resulted in increased penetration of solar photovoltaic (PV) power generation in distribution networks. As the PV systems penetration is likely to increase in the future, utilizing the reactive power capability of PV inverters to mitigate voltage deviations is being promoted. In recent years, droop control of inverter- based distributed energy resources has emerged as an essential tool for use in this study. The participation of PV systems in voltage regulation and its coordination with existing controllers, such as on-load tap changers, is paramount for controlling the voltage within specified limits. In this work, control strategies are presented that can be coordinated with the existing controls in a distributed manner. The effectiveness of the proposed method was demonstrated through simulation results on a distribution system.     

Dynamic modeling of a hybrid wind/solar/hydro microgrid in EMTP/ATP

Microgrids are LV or MV electric networks which utilize various distributed generators (DG) to serve local loads. In this paper, dynamic models of the main distributed generators including photovoltaic (PV) cell, wind turbine, hydro turbine as well as the equivalent power electronic interfaces, battery unit of PV and excitation system of hydro turbine have been made in ElectroMagnetic Transient Program/Alternative Transient Program (EMTP/ATP) software package. Control strategies based on active power/frequency and reactive power/voltage droops for the power control of the inverters have been also developed. Case studies have been carried out in a distribution network to investigate the dynamic behavior of the micro-sources in both steady state and fault scenarios. Simulation results verify the feasibility of the proposed models.     

基于改进群搜索算法的含光伏发电的配电网优化重构研究

配电网中光伏发电装机容量迅速上涨,针对其所带来的波动性和间歇性对配电网重构后的可靠性和经济性产生的影响,提出一种含光伏发电的配电网优化重构策略。首先。以网损最小化为目标函数,建立含光伏发电的配电网数学模型;其次,运用模糊理论对群搜索算法进行改进,并将改进群搜索算法应用到配电网重构路径的优化中;最后,通过算例对含光伏发电的配电网进行分析。结果表明,该方法收敛速度快、寻优时间短且动作次数少,有效提高了配电网的运行经济性。     

基于线性化前推回代方程的不平衡配电网概率潮流计算

传统半不变量法采用雅可比矩阵表达输入输出变量间的线性关系且假设网络三相平衡。而实际配电网线路的R/X较高,雅可比矩阵极易呈现病态,且单相光伏的高渗透及负荷不均匀分布造成配电网严重不平衡。为此,提出一种基于线性化前推回代方程的不平衡主动配电网概率潮流算法。该算法将三相前推回代潮流方程进行高精度线性化,综合运用半不变量法和Gram-Charlier级数进行配电网概率潮流计算。所提算法基于真实澳大利亚低压不平衡配电网进行24 h Matlab仿真,验证其可行性、高效性及鲁棒性,并抽取2个典型时刻对比分析验证光伏接入对配电网潮流的概率性和配电网运行性能的影响。     

Augmenting rooftop solar energy penetration ratio with secondary distribution network using smart inverter for maximum power transfer capacity for subordinate grid- A review

A rooftop photovoltaic power station, or rooftop PV system, is a photovoltaic system that has its electricity-generating solar panels mounted on the rooftop of a residential or commercial building or structure. The various components of such a system include photovoltaic modules, mounting systems, cables, solar inverters, and other electrical accessories. Rooftop mounted systems are small compared to ground-mounted photovoltaic power stations with capacities in the MW (megawatt) range. With the significant improvement of Rooftop Solar Photovoltaic Energy System (RSPES) among various Renewable Energy Systems, the major issues, effects, and several operational characteristics of the rooftop solar PVs in the Distribution System (DS) with Low Power Utility Network are actively being studied and investigated by global researchers and operation engineers. The most important objective of various researches about RSPES is to design a Power System with Optimal Maximum Power Transfer Capacity (MPTC). These review papers analyze the performance of Secondary Distribution System integrated to grid with Smart Inverter with or without the presence of Distribution Generation (DG) units. The effects caused by the penetration of Rooftop Solar Photovoltaic (PV) units in the Distribution Equipment (DE) are detailed in this paper with various research techniques. With the consideration of different objective constraints, Optimization techniques are utilized for solving minimization problems of objectives such as Size, Area, Operational Characteristics, Energy Loss, Cost of Installation, Generation Cost, Peak Load, Reverse Power Flow, and maximization problems of objectives such as PV power generation, Energy Saving Capability, Electricity Energy Mix, etc.. The various optimization techniques and frameworks for improving the performance of Power System and their corresponding results are demonstrated in this paper. This paper reviews totally 42 related researches done on the different phases of Optimization based Rooftop Solar PV system in the period between 2015 and 2017. This review summarizes the evaluation of the i) Solar rooftop energy with effects of increase in penetration; ii) The performance of efficient secondary distribution system with grid integrated smart inverter; iii) Algorithms based on optimization for solving the objectives in rooftop solar PV system are investigated.     

基于二次插值粒子群算法的配电网多目标双阶段故障恢复策略

随着人们对供电质量要求的提高,为了满足配电系统的可靠性、安全性和经济性方面的要求,配电网的故障恢复策略相关研究成为了目前专家学者研究的重要课题。提出了基于二次插值粒子群算法的适用于配电网多目标下故障恢复的双阶段策略。首先建立了配电网故障恢复时基于不同目标函数下的数学模型,制定了适合基于二次插值粒子群算法的配电网多目标双阶段故障恢复策略的编码策略,并利用基于二次插值的粒子群算法对其进行求解。最后以某实际电网为例,在不同故障情况下验证了所提策略的正确性和实用性。