基于多智能体一致性协议的微电网分层分布实时优化策略

经济运行、频率和电压控制及系统稳定性是微电网实时控制的主要内容。基于多智能体系统一致性协议,提出了一种分层分布的实时优化策略。首先,在仅考虑分布式电源出力约束的条件下,应用一阶一致性实现对分布式电源有功出力的控制,优化运行成本;其次,针对下垂控制特性,提出了一种新的二阶一致性协议,用于实现分布式电源功率的精确控制;最后,应用一致性协议实时协调分布式电源的下垂参数,实现了系统频率和电压的优化。通过Lyapunov直接法对所提策略进行稳定性分析,证明系统是渐进稳定的。仿真分析及结果验证了所提策略的有效性。     

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。     

基于Zigbee通信网络的低压微电网分布式功率控制

针对低压微电网中传统下垂控制难以实现多个分布式电源(Distributed Generations, DGs)按照下垂系数合理分配有功输出的问题,提出了一种基于通信网络的分布式控制策略。采用并构建了Zigbee无线通信网络拓扑结构以实现DG间的信息交互。设计了基于一致性算法的分布式PI控制器以实现多个DG的有功输出按额定比分配。最后通过仿真验证了所提方法的可行性,并表明网络延时和网络拓扑结构的变化会影响微电网系统的稳定性。     

一种低压微电网中的分布式电压控制算法

为了实现电压调节和提高供电能力,提出了一种在低压微电网中利用分布式电源(Distributed Generators,DGs)发出的有功来进行电压控制的分布式电压算法。针对低压微电网的线路阻抗特性,分析了电压和有功的关系。由系统线路结构建立通信链路,并对电压超出上下限的母线初始化,计算出所需补偿的有功功率。基于本地信息,利用参数化状态转移矩阵对电压进行修正,并考虑了分布式电源的有功容量限制。通过该算法协调和分配各分布式电源所需承担的功率,共同作用实现电压控制。仿真结果表明该算法能够有效实现电压调节和减小电压偏差,提高电压质量。     

Optimal active and reactive nodal power requirements towards loss minimization under reverse power flow constraint defining DG type

In this paper a novel approach regarding the optimal penetration of Distributed Generation (DG) in Distribution Networks (DNs) towards loss minimization is proposed. More specific, a Local Particle Swarm Optimization (PSO) variant algorithm is developed in order to define the optimal active and reactive power generation and/or consumption requirements for the optimal number and location of nodes that yield loss minimization. Thus, the proposed approach provides the optimal number, siting and sizing of DGs altogether. In addition, based on the optimal power requirements of the resulted nodes, a combination of potential DG types to be installed is recommended. The proposed objective function in this paper is also innovative since it embeds the constraint of reverse power flow to the slack bus by the formation of a new penalty term. The proposed methodology is applied to 30 and 33 bus systems. The results indicate the optimal number, locations, and capacity of DG units, which were calculated simultaneously. Finally, the impact of the predefined amount of permissible reverse power flow to the optimal solution is also examined through two scenarios: the first considers zero reverse power flow and the second unlimited reverse power flow.     

含DSTATCOM和分布式电源配电网的无功电压协调控制

提出一种基于斜率调节的配电网静止同步补偿器(DSTATCOM)群的协调控制方法,用于解决同一区域内多个分布式电源的无功电压协调控制问题。建立计及网架参数条件下,无功电压与分布式电源输出有功电流及斜率调节下DSTATCOM输出无功电流之间的关系,并根据装置的最大无功容量整定各个DSTATCOM的调节斜率,合理分配各个装置的无功输出,将已整定的斜率以及线路的电抗之和作为无功电流的比例增益作为负反馈,构成DSTATCOM新的电压参考值,建立基于斜率调节的DSTATCOM群协调控制策略。针对一个含有双分布式电源和DSTATCOM的配电网系统进行仿真,仿真结果表明:该整定斜率调节下能够进行协调各DSTATCOM无功动态行为,不需要控制器间实时通信实现装置无功出力且能够按比例分配并稳定系统电压。     

A smart distribution system reconfiguration algorithm with optimal active power scheduling considering various types of distributed generators

This paper presents an efficient way of solving the distribution system reconfiguration (DSR) problem in electrical power systems with consideration of different types of distributed generators (DGs). The objective of a DSR is to minimize the system power loss while satisfying the system constraints and keeping the topology of the system radial. In this paper, a new DSR algorithm based on a modified particle swarm optimization (PSO) is proposed to incorporate DGs with the constant voltage control mode. The proposed method is very efficient because it avoids an extra iteration loop for computing the reactive power at PV buses in order to keep the voltage at a specified magnitude. Furthermore, if the reactive power requirement is not met in between the extreme limits, the proposed algorithm strictly searches for the best possible tie switch combination to simultaneously reduce the power loss and ensure that the DGs operate in PV mode within acceptable reactive power limit. The proposed algorithm also integrates hourly DSR with optimal DG active power scheduling considering the DG type, generation limit constraints, and the allowable DG penetration level. The validity and the effectiveness of the proposed method has been tested using standard IEEE 33‐bus and 69‐bus distribution networks with various case studies. Test results show that the proposed method is robust and delivers a minimal average power loss compared with different methods, and it efficiently models DGs in DSR, demonstrating that the presence of DGs can further reduce the system loss. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

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.     

基于边际成本下垂控制的自治微电网分布式经济运行控制

由于微电网中不同类型分布式电源的运行成本各异,传统下垂控制按照容量比例分配功率,易导致系统成本偏高。提出基于边际成本的改进下垂控制,按各分布式电源边际成本一致分配功率。为进一步解决其功率分配精度易受线路阻抗影响的问题,提出基于一致性算法的分布式经济运行控制策略,通过优化下垂控制的参考电压,实现各分布式电源边际成本一致,从而有效降低系统运行成本。该分布式经济运行控制策略利用稀疏分布式网络,无中心节点,仅需相邻分布式电源间交互信息,可靠性高。MATLAB/Simulink仿真验证了所提方法能较好地实现自治微电网的经济运行。     

Optimal reactive power control of DGs for voltage regulation of MV distribution systems using sensitivity analysis method and PSO algorithm

This paper addresses the problem of reactive power control of distributed generation (DG) units in the medium voltage (MV) distribution systems to maintain the system voltages within the predefined limits. An efficient approach for the load flow calculation is used here which is based on the topological structure of the network. It has been formulated for the radial distribution systems. A direct voltage sensitivity analysis method is developed in this paper which is also based on the topological structure of the network and independent of the network operating points. Thus, the sensitivity matrix is calculated once with the load flow program and it is used in all the system working conditions. The problem of DGs reactive power control is formulated as an optimization problem which uses the sensitivity analysis for linearizing the system around its operating points. The objective of the optimization problem is to return the system voltages inside the permitted range by using the reactive power of DGs in an optimal way. The optimal solutions are obtained by implementing particle swarm optimization (PSO) algorithm. Then, the results are verified by running a load flow considering new values of DGs reactive power. The procedure is repeated as long as a voltage violation is observed. Simulation results reveal that the proposed algorithm is capable of keeping the system voltages within the permitted limits.     

基于改进灵敏度分析的有源配电网智能软开关优化配置

随着大量间歇性分布式电源(DG)不断渗透到配电网中,电压越限和双向潮流等问题变得越发严重.智能软开关(SOP)是一种柔性电力电子装置,安装在配电网中用来替代传统联络开关,可以实现快速电压调节和准确潮流控制,从而有效解决DG所带来的相应问题.然而,SOP的投资成本较高,使得SOP选址定容问题显得尤为关键.文中提出一种基于改进灵敏度分析的有源配电网SOP优化配置方法.首先,结合DG出力的时序变化特性,从改善电压分布的角度采用改进灵敏度分析方法优化SOP选址;其次,采用二阶锥规划算法求解在改进灵敏度计算下的SOP选址定容优化模型;最后,在改进的IEEE 33节点配电系统上,对文中提出的优化方法进行分析与验证.算例结果表明,采用文中提出的方法对SOP进行优化配置可有效节省配电网年度综合运行成本和改善系统电压,有利于提高有源配电网运行的经济性和可靠性.     

微电网中的有功功率和无功功率均分控制

针对在单元输出功率控制(UPC)和馈线潮流控制(FFC)模式下,分布式电源(DG)之间的有功功率和无功功率均分控制进行了分析。在UPC模式下,DG输出的有功功率恒定,能够跟随给定值实现有功功率均分;在FFC模式下,DG所在馈线上的潮流值恒定能够跟随给定值,实现微电网和大电网之间的潮流交换恒定。但是受线路阻抗和本地负荷等的影响,DG的输出电压值不同,进而产生无功环流。针对这一问题,文中提出了一种抑制无功环流的控制策略,该策略是在无功电压下垂控制中加入电压补偿环节,以达到抑制无功环流的目的,该方法有效消除了逆变器之间的无功环流。针对线路阻抗和本地负荷不同时对微电网中无功环流的影响进行了分析,并分别进行了仿真,验证了该控制策略的有效性和可行性。     

无功补偿设备和分布式电源协同的配电网优化控制策略研究

集中式控制模式因可靠性低、通信计算压力大、可扩展性差而不能适应高渗透率分布式电源接入的配电网控制的需求。考虑配电网中接入的无功补偿设备,基于分布式协同控制思想,利用分布式电源分组和无功补偿设备分组实现配电网多目标分布式优化控制。针对节点电压控制,设计了以分布式电源容量利用比为一致性变量的电压控制组分布式控制算法。根据配电网与外部电网交换功率差额的信息,设计了以无功补偿设备容量利用比为一致性变量的无功控制组分布式控制算法。对于有功功率控制,设计了分别以容量利用比和功率因数为一致性变量的有功控制组分布式控制算法。给出了各控制组分布式控制算法参数的整定方法,并进行了两种有功功率控制方法的比较。通过14节点配电网系统的仿真算例验证了该方法的正确性和有效性。     

Multi-Objective Approach for Reconfiguration of Distribution Systems with Distributed Generations

This paper presents a fuzzy multi-objective based heuristic algorithm for network reconfiguration of distribution systems considering distributed generations (DGs). The objectives of reduction of real power loss, branch current carrying capacity limit, maximum and minimum voltage constraints, and feeder load balancing are considered for performance enhancement of the distribution system. Since these objectives are non-commensurable and difficult to solve simultaneously using conventional approaches, they are converted into fuzzy domain and a fuzzy multi-objective function is formulated. A sensitivity analysis based on voltage profile improvement and real power loss reduction is used for obtaining optimal locations of DGs and genetic algorithm is used for optimal sizing of DGs. The proposed reconfiguration algorithm is implemented in two stages, initially in the first stage without incorporating DGs and in the second stage incorporating DGs for obtaining an optimal distribution system network reconfiguration. The advantage of the proposed method is demonstrated through a seventy node four feeders and a sixteen node three feeders distribution systems.     

分布式电源对配网供电电压质量的影响与改善

提出利用短路比和刚性率来评估分布式电源(distri- buted generation,DG)对配网供电电压质量影响的方法,通过仿真验证方法的可行性。并进一步具体分析旋转型分布式电源和逆变型分布式电源对系统供电电压的不同影响,分析和仿真结果证明在同等渗透率下,逆变型分布式电源对并网节点的电压影响比旋转型更小,向系统提供的短路电流也要远小于旋转型,因此在同等条件下逆变型分布式电源更加适合应用于密集负荷、高短路容量的城市配电网。并针对逆变型分布式电源抑制供电电压波动的特点,提出电压控制方法,仿真验证其同样可在一定程度上改善配电网内供电电压质量问题。     

含母线电压补偿和负荷功率动态分配的直流微电网协调控制

针对孤岛直流微电网需要独自承担系统母线电压稳定和精确的功率分配,提出了含母线电压补偿和负荷功率动态分配的协调控制策略。在主控制层中采用下垂控制来实现分布式电源之间的功率共享;在下垂控制的基础上,提出了考虑电压调节控制和电流矫正控制的分布式二次控制,其对传统下垂控制带来的直流母线电压跌落进行补偿,使得母线电压恢复到额定值;通过对下垂系数的不断调整,达到了负荷功率分配的高精度。最后,利用MATLAB/Simulink对所设计的控制策略在不同运行模式下进行仿真验证,仿真结果表明所提的控制策略可以实现直流微电网的稳定运行和负荷功率的动态分配,且能够满足分布式电源即插即用等要求。     

基于多代理技术的直流配电网电压控制方法

提出了一种智能多代理电压控制方法以应对高分布式电源渗透率给直流配电系统电压调节带来的挑战。所提控制方法分为2层,在第1层中,将与交流/直流(AC/DC)转换器相接供电节点设置为中枢点,通过调节该节点电压来把系统电压控制在规定的范围内。在第2层调节方案中,通过优化系统中所接分布式电源的有功出力来控制直流配电系统电压。算例验证了所提电压控制方法的有效性和经济性。     

Hybrid approach for optimal placement of multiple DGs of multiple types in distribution networks

In the present work, a hybrid approach has been proposed for optimal placement of multiple DGs of multiple types. The analytical approaches may not be appropriate for optimal placements of multiple DGs alone. In this work, hybridization of analytical method and heuristic search for the optimal placement of multiple DGs in power distribution network for reduction of power loss has been proposed. In this approach, the sizes of DGs are evaluated at each bus by analytical method while the locations are determined by PSO based technique. The objective function has been minimized under operating constraints. The improvements in bus voltage profile and optimal power factor of the DGs have also been observed. To validate the proposed hybrid approach, results have been compared with particle swarm optimization (PSO) technique and existing fast improved analytical (IA) method results. The proposed technique has been tested on 33-bus, and 69-bus test systems.     

Selective Sharing of Load Current Components Among Parallel Power Electronic Interfaces in Three-phase Four-wire Stand-alone Microgrid

This paper investigates selective sharing of load current components among the parallel operation of distributed generators (DGs) in three-phase four-wire stand-alone microgrids. The proposed control method is based on master-slave operation of DGs, and the goal of selective sharing of load current components is to have DGs located in close proximity of the load operating in slave mode, in order to inject their available energy and also compensate the non-active load current components, while the distant DGs might operate in master mode to share the remaining load autonomously. Droop control is employed due to impracticality of communication at remote nodes, and resistive line impedance compensation is adopted to decouple active and reactive power controllers and ensure proper active power sharing among master DGs, irrespective of the mitigation of non-active current components by the slave inverters. The sharing factors for each current component are determined by a higher level control. The Conservative Power Theory (CPT) decompositions provide decoupled power and current references for the inverters, resulting in a selective sharing strategy. The principles supporting the developed control strategy are discussed, and the effectiveness of the control is demonstrated through computational simulations using PSIM software.     

分布式电源短路计算模型及电网故障计算方法研究

分布式电源的发电模式及并网方式多样,其馈入电网的故障电流特性与传统交流同步发电机相比存在较大差异,使以传统交流同步电机供电电源为基础的短路电流分析理论和方法难以满足分布式电源接入后电网故障分析的要求,给继电保护原理研究和整定计算提出了新的课题并备受关注。根据不同类型分布式电源的低压穿越运行技术要求,建立逆变型电源的短路计算模型。并考虑异步型电源撬棒保护的动作行为特征,建立了异步型电源在电网严重和非严重故障条件下的等值计算模型。进而,提出了含分布式电源接入的电网故障计算方法。仿真对比分析表明,电网故障计算方法精度较高,能更好地满足工程应用要求。