Network loss minimization with voltage security using differential evolution

This paper presents a differential evolution (DE) based optimal power flow (OPF) for reactive power dispatch in power system planning studies. DE is a simple population-based search algorithm for global optimization and has a minimum number of control parameters. The problem is formulated as a mixed integer non-linear optimization problem taking into account both continuous and discrete control variables. The proposed method determines control variable settings such as generator voltages (continuous), tap positions (discrete) and the number of shunt reactive compensation devices to be switched (discrete) for real power loss minimization in the transmission system using DE algorithm. Most of the evolutionary algorithm applications to optimization problems apply penalty function approach to handle the inequality constraints, involving penalty coefficients. The correct combination of these coefficients can be determined only by a trial and error basis. In the proposed approach, the inequality constraints are handled by penalty parameterless scheme. Voltage security margin was evaluated using continuation power flow (CPF), to ensure the feasibility of the optimal control variable setting. The suitability of the method was tested on IEEE 14 and IEEE RTS 24-bus systems and results compared with sequential quadratic programming (SQP) method. The DE provides near global solutions comparable to that obtained using SQP.     

基于量子微分进化算法的分布式电源多目标优化规划

为了克服再生能源的间歇性、随机性导致的分布式电源优化结果不够准确,提出了一种基于概率特性的电源-负荷综合模型,将分布式电源的随机出力问题转化成确定性问题。考虑分布式电源对配网的影响,建立了包含建设运行费用、网络损耗、可靠性费用和环境因素的多目标优化模型。提出采用量子微分进化算法对分布式电源接入配网进行优化配置,该算法采用量子的概率表达特性和叠加态特性,潜在地提高了算法的寻优效率,同时采用变异和交叉操作,保持了良好的种群多样性。通过对算例的分析,表明所提出的模型和算法合理、可行。     

基于分布式发电的不对称电压调节器仿真

针对本地不对称的三相负荷所引起的公共连接点（PCC）三相电压不对称,提出了基于分布式发电的不对称电压调节器的设计,将三相不对称电压的调节统一于分布式发电系统中,在并网的情况下实现了负荷不对称时PCC点电压的调节。采用的是功率电流双环控制策略的逆变控制系统,通过合理的选取功率控制环,电流控制环,PI控制器参数,可以使得分布式发电逆变装置在两种情况下具有良好的电压调节稳态及动态性能。利用Matlab/Simulink对系统进行仿真,验证了所提系统结构及控制策略设计的可行性。     

基于分布式发电的不对称电压调节器仿真

针对本地不对称的三相负荷所引起的公共连接点(PCC)三相电压不对称,提出了基于分布式发电的不对称电压调节器的设计,将三相不对称电压的调节统一于分布式发电系统中,在并网的情况下实现了负荷不对称时PCC点电压的调节.采用的是功率电流双环控制策略的逆变控制系统,通过合理的选取功率控制环,电流控制环,PI控制器参数,可以使得分布式发电逆变装置在两种情况下具有良好的电压调节稳态及动态性能.利用Matlab/Simulink对系统进行仿真,验证了所提系统结构及控制策略设计的可行性.     

Distributed generation and the voltage profile on distribution feeders during voltage dips

The presence of distributed generators in the distribution network results in an increase of the voltage magnitude close to these generators, during a fault elsewhere in the distribution system or in the transmission system. This voltage dip mitigation capability of converter-connected distributed generation (DG) units is dependent on the control strategy of the converter. To compare the influence of different types of converter-connected distributed generators on the voltage profile along distribution feeders during a fault, the quantity,“voltage ratio” is used. This voltage ratio is obtained by division of the voltage during the voltage dip by the voltage just before the voltage dip. The different converter types are modelled, and the influence on the voltage ratio is analysed.     

考虑电压因素的电力系统输电阻塞调度

针对开放输电环境下出现的由于电压稳定因素造成的输电阻塞问题,提出了一种考虑电压稳定的输电阻塞调度方法.该方法在传统的最优潮流优化算法的基础上,用负荷裕度指标作为系统电压稳定性的指示器,结合连续潮流算法对系统在正常状态和N-1事故状态下的电压稳定性进行分析,如果出现由于电压稳定约束造成的输电阻塞问题,将计算发电机有功出力对负荷裕度的灵敏度指标,以此作为依据调节发电机有功出力来增大系统负荷裕度,解决输电阻塞问题.该算法在6节点系统的应用效果表明了其有效性.     

考虑电压稳定的电力系统无功优化规划

建立了模糊多目标无功优化规划的数学模型。在目标函数中考虑了网损、无功补偿设备的投资、静态电压稳定裕度以及负荷节点电压的偏移。首先采用电压稳定灵敏度排序法找出电压稳定性最差的节点,作为候选无功补偿节点;然后采用遗传算法对数学模型进行求解,得到优化补偿节点及补偿节点的优化补偿容量。通过对IEEE30节点的计算结果表明:采用文中的优化规划方法能够达到很好的降损效果,提高了整个系统的电压稳定性。     

考虑电压稳定的电力系统无功优化规划

建立了模糊多目标无功优化规划的数学模型.在目标函数中考虑了网损、无功补偿设备的投资、静态电压稳定裕度以及负荷节点电压的偏移.首先采用电压稳定灵敏度排序法找出电压稳定性最差的节点,作为候选无功补偿节点;然后采用遗传算法对数学模型进行求解,得到优化补偿节点及补偿节点的优化补偿容量.通过对IEEE30节点的计算结果表明:采用文中的优化规划方法能够达到很好的降损效果,提高了整个系统的电压稳定性.     

Large scale voltage stability constrained optimal VAr planning andvoltage stability applications using existing OPF/optimal VAr planningtools

Traditionally in optimal VAr planning, the feasible operation has been translated as observing voltage profile criteria ensuring that the system voltage profile is acceptable for system normal and post contingency conditions. This feasibility definition is not sufficient when considering the VAr planning practice of the utilities concerned with voltage stability problems. Presently, these utilities use two reinforcement criteria for VAr additions. While for VAr design in the regions the voltage profile criteria is considered, for bulk transmission system VAr resources are designed to guard against voltage instability. This paper reports on the findings of a recently completed EPRI project evaluating the existing optimal VAr planning/OPF tools for voltage stability constrained VAr planning and voltage stability applications. Two of the selected tools were adapted to address these applications on four large scale utility systems (up to 6000 buses). The results were also verified using EPRI's voltage stability program (VSTAB). The results obtained indicate that OPF/VAr planning tools can be used to address voltage stability constrained VAr planning and voltage stability applications in an accurate way. Additional advantages offered by these tools are easier procedures, less computation and avoidance of engineering judgment in identifying the amount of VAr requirement at the candidate sites     

考虑电压稳定性的华东电网无功补偿研究

近年来华东电网缺电严重,电网比较薄弱,在某一故障情况下存在电压稳定性问题。为了解决华东电网的电压稳定性问题,有必要合理配置各区域无功补偿。介绍了通过特征值法研究华东电网的稳定性问题,并找出弱母线,给出合理的无功补偿方案。通过对2004年夏季华东电网数据的计算给出了弱母线位置以及相应的无功补偿容量。     

考虑电压稳定约束的无功规划研究综述

随着电力市场进程的加快,系统运行不断逼近极限,电压稳定已成为影响系统安全的焦点问题,而合理的无功规划对保持系统电压稳定具有重要意义.首先解释了考虑电压稳定约束的无功规划基本概念,接着对目前基于静态和动态电压稳定约束的无功规划模型和求解方法进行总结与评述,提出了该领域需要深入研究的五个关键问题,强调了考虑安全性和经济性的无功规划是当前该领域的发展趋势,最后指出了建立基于动态电压稳定裕度的无功规划模型是避免系统电压崩溃的关键.     

基于时序特性含储能装置的分布式电源规划

基于风力发电、光伏发电和5类不同负荷的时序特性,以配电网的投资成本、维护成本、购电费用、可靠性成本、环境污染补偿费用之和最小为目标函数,建立分布式电源和储能装置的选址定容规划模型。该模型采用负荷、分布式电源和储能装置协调优化的策略,对钠硫蓄电池储能装置的容量及功率进行优化配置,以在不过多装设储能装置及保证配电网经济性、可靠性的前提下,提高配电网对分布式电源接纳能力。采用粒子群优化算法对典型算例进行求解,结果验证了所提模型和方法的正确性和有效性。     

考虑电压稳定约束的无功规划研究综述

随着电力市场进程的加快,系统运行不断逼近极限,电压稳定已成为影响系统安全的焦点问题,而合理的无功规划对保持系统电压稳定具有重要意义。首先解释了考虑电压稳定约束的无功规划基本概念,接着对目前基于静态和动态电压稳定约束的无功规划模型和求解方法进行总结与评述,提出了该领域需要深入研究的五个关键问题,强调了考虑安全性和经济性的无功规划是当前该领域的发展趋势,最后指出了建立基于动态电压稳定裕度的无功规划模型是避免系统电压崩溃的关键。     

An economical generation direction for power system static voltage stability

This paper proposes an economical generation direction for static voltage stability. The proposed generation direction minimizes the total operating cost at any loading level, up to the point of collapse. The proposed approach, named as EGD approach, is based on the economic load dispatch with load flow. Two alternative methods to identify the economic generation direction are proposed. Economical generation direction is used in the continuation power flow process to obtain the static voltage stability margin. Static voltage stability margin with economical generation direction is compared with the margins resulting from other existing generation directions in the modified IEEE 14-bus test system under various system operating conditions. Cost of providing loading margin as well as PV curves and losses under different generation directions resulting from various generation direction approaches are also studied and compared. The proposed approach provides an alternative way for utilities to obtain the lowest total operating cost with voltage stability constraint by using any existing commercial software.     

用于提高电压稳定裕度的发电机无功出力管理

电力系统电压稳定裕度大小与系统无功储备相联系,研究了通过管理系统发电机的无功出力来提高系统的电压稳定裕度。把重新安排系统无功出力形成一个优化问题,采用伪梯度进化算法(PGEP)寻求全局的最优解,在搜索过程中利用模式分析技术指导寻优方向。对新英格兰10机39节点系统的仿真分析表明,与常规进化算法(SEP)相比,所提出的方法具有更快的收敛速度与更好的寻优能力,能够增加系统的无功储备,同时减少系统的有功及无功损耗,在不增加新设备及不改变系统有功分布的情况下使系统的电压稳定裕度得到明显提高。     

基于多策略差分进化算法的输电网规划

差分进化(DE)算法是一类基于种群的、具有全局优化性能的、通过实数编码的启发式算法。但差分算法搜索策略过于单一,局部搜索能力差,因此通过增加多策略变异和局部寻优策略来提升全局和局部搜索能力,同时降低搜索时间,使其适应于求解大规模输电网规划问题。采用基于线路投资费用、网损费用、正常运行时的过负荷费用及输电走廊费用的输电网规划模型,通过对Garver-6系统和18节点系统的计算,不仅验证了算法及模型应用于输电网规划的正确性和有效性,而且验证了算法具有很高的计算速度和收敛性,为DE算法的进一步改进应用打下基础。     

Control of voltage stability using sensitivity analysis

The effects of static compensation on the voltage stability boundary are investigated. For a class of voltage instabilities which correspond to static bifurcations of load flow equations, minimum singular values of the Jacobian matrix and total generated reactive power are calculated as indicators of stability margin, and sensitivity methods are used for reactive support allocation. Improvement in stability margin under progressive loading was investigated on a 39-bus test system for different allocations and amounts of reactive support with reactive generation capabilities taken into account     

计及不确定性与节点边际容量成本的分布式光伏电源规划

从时序性与波动性两方面描述不确定性,构建了考虑不确定性的光伏电源（PV）出力模型与负荷模型。对配电网节点边际容量成本（LMCC）的分析推导与应用进行了改进,明确了含PV与不含PV的LMCC计算方法。利用序贯蒙特卡洛模拟法处理不确定性,利用LMCC的计算指导分布式光伏的选址定容,在此基础上考虑安全性、经济性等多方约束,构建了基于序贯蒙特卡洛模拟与节点边际容量成本的PV规划模型,提出了相应的算法流程。将模型应用于简单馈线分析与IEEE33节点系统规划,验证了方法的有效性;并初步探讨了电网公司针对PV可采取的运营策略,为后续研究指明了方向。     

分布式电源对配电网静态电压稳定性的影响

为研究分布式电源(Distributed Generation,DG)的接入对配电网电压稳定性的影响,利用一种新的前推回代潮流算法分析配电网各节点的静态电压稳定裕度指标,并通过对IEEE33系统的计算,分析PQ、PV型DG以不同方式并网对配电网静态电压稳定性的影响。分析结果表明:利用本算法可实现配电系统负荷按相同比例增长,正确判断系统所能承受的负荷增长。