Probabilistic reactive power procurement in hybrid electricity markets with uncertain loads

This paper presents a novel probabilistic algorithm for optimal reactive power provision in hybrid electricity markets. The proposed algorithm is a six-stage multiobjective nonlinear constrained optimization problem which takes into account load forecasting inaccuracies. Considering a set of probable forecasted loads, a three-component expected total market payment function is suggested being minimized as cost function of the first stage. Besides economic issues, expected voltage security margin, deviation from multilateral and pool based energy transactions, deviation from spinning reserve contracts, having adequate local reactive power reserve in each voltage control area of the system and transmission congestion probability are well thought out in stages 2-5 as technical aspects of the market. Finally, in the last stage, using different weighting factors to compromise between all objects, a probabilistic multiobjective function is presented to find the best reactive power market schedule. The proposed algorithm is applied on IEEE 24-bus test system. As a benchmark, Monte Carlo Simulation method is utilized to simulate the market of given period of time to evaluate results of the proposed algorithm, and satisfactory results are achieved.     

Multi-objective optimal reactive power flow including voltage security and demand profile classification

This paper proposes a method to optimize reactive power flow (ORPF) with regard to multiple objectives while maintaining system voltage security across a time-domain. Compromise programming is employed in the ORPF formulation, which is designed to minimize both losses and payment for the reactive power service in the framework of the UK daily balancing market. In coordination with ORPF, continuation power flow (CPF) is applied to evaluate and maintain the voltage security margin of the system. Prior to the optimisation procedure, the related control parameters can be grouped with the aid of a load classification method in order to simplify the control actions. During the optimisation, through the application of both ORPF and CPF, multi-objective optimisation can be achieved with voltage security at an acceptable level. The Ward and Hale 6-bus system and a 60-bus UK test system are presented to illustrate the application of the proposed modeling framework.     

Cost-based reactive power pricing with voltage security consideration in restructured power systems

In the restructuring power industry, voltage security has become a challenging problem since power systems tend to operate closer to security boundaries and as a consequence, the voltage instability, which is caused by insufficient reactive power supply, poses a serious threat to system security and reliability. Establishing an equitable and effective reactive power market with consideration of the voltage security problem is very important to provide a reliable restructured power system. Therefore, this paper proposes a cost-based reactive power pricing, which can integrate the reactive power cost minimization and the voltage security problem into the optimal power flow (OPF) problem, and the sequential quadratic programming (SQP) is employed to solve the optimization problem. The effectiveness of the proposed method is verified using a modified IEEE 14-bus system. A study on the effects of the voltage stability margin (VSM) requirement under normal condition and contingencies on the reactive power cost is also presented.     

Two-stage optimization algorithm for short-term reactive power planning based on zonal approach

There are various methods for procurement of reactive power as an ancillary service in deregulated market environment. Reactive power market model based on voltage control zones and two-step optimal power flow algorithm is proposed in this paper. Zones are formed by splitting the power system or a control area of an interconnected power system into autonomous voltage sub-areas with sufficient reactive power reserves using the electrical distance method. Every zone formes a single reactive power market. First step of an optimization algorithm determines zonal reactive power prices based on generator's cost functions for reactive power production. Total cost minimization is the goal of the second optimization step where the final dispatching decision is made according to transmission losses and zonal reactive power prices respecting power system planned conditions and security constraints. Proposed algorithm is tested on IEEE 39 bus test system ensuring the system operator's minimal payment for reactive power and transmission losses, without jeopardizing power system security.     

基于改进遗传算法的风电场多目标无功优化

针对风电场并网运行的多目标无功优化和电压稳定问题,建立了基于异步发电机内部等值电路的含风电场的电力系统无功优化模型,提出了风电场无功优化的目标函数和约束条件。结合非支配排序思想、精英保留策略、改进的小生境技术,得到了一种将向量模适应度函数作为淘汰准则的改进Pareto遗传多目标优化算法。以某风电场接入IEEE 14节点标准测试系统为例,将改进算法用于含风电场的电力系统无功优化。仿真结果表明,应用改进的遗传多目标优化算法可以同时得到多组Pareto最优解,为决策者提供了更多的选择余地,使风电场并网点母线电压在允许范围内。     

考虑无功辅助服务分段报价的多目标无功优化方法

电力市场改革对电力系统无功辅助服务机制和无功优化提出了更高的要求。如何在确保电力系统电压质量和安全可靠运行的前提下,实现无功辅助服务市场化、优化无功资源调控是无功电压自动控制面临的重要课题。基于电力市场环境提出了一种无功辅助服务分段报价规则,构建机组进相、滞相时的购电成本模型。在此基础上,提出了一种考虑无功辅助服务规则的多目标无功优化控制方法。对某省级电网实际运行方式进行了仿真计算和分析、讨论。仿真结果验证了该算法无功调控效果的有效性、经济性与均衡性,满足电力市场环境下实际应用需求。     

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。     

Multi-objective day-ahead localized reactive power market clearing model using HFMOEA

In this paper, a multi-objective localized day-ahead reactive power market clearing model named as multi-zone DA-RPMC is proposed. The proposed model is based on the zonal uniform price auction by separating the whole market into various voltage control areas/zones. Two objective functions such as total payment function (TPF) for reactive power support services from generators/synchronous condensers and total real transmission loss (TRTL) are minimized simultaneously using a hybrid fuzzy multi-objective evolutionary algorithm (HFMOEA) satisfying all the power system constraints. The proposed multi-zone DA-RPMC model is tested and compared with single-zone DA-RPMC model on standard IEEE 24 bus reliability test system. For both the single-zone and multi-zone DA-RPMC models, the performance of HFMOEA is also compared with NSGA-II in terms of various performance metrics such as spacing, spread and hypervolume. Further, both the single-zone and multi-zone DA-RPMC models are also analyzed on the basis of market power owned by any generator/any generating company. The simulation results obtained confirm the superiority of HFMOEA based multi-zone DA-RPMC model to take better day-ahead reactive power market clearing decisions.     

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。     

考虑换流站损耗特性的交直流系统多目标无功优化控制

交直流互联系统中各个直流输电通道在输送大量电能的同时,也会产生很大的电能损耗。通过协调优化多回超/特高压直流输电系统的电压无功控制措施,能够有效地降低整个交直流系统运行的损耗电量。提出一种考虑换流站详细损耗特性的交直流系统多目标无功优化控制方法,以包括换流站内部各主要设备损耗的整个交直流输电系统总网损和所有关键节点电压偏差平方和的最小化为目标,建立交直流互联系统的多目标无功优化控制模型。提出一种自适应加权和算法,结合GAMS/CONOPT解法器求解得到多目标优化问题的均匀分布的帕累托最优解集。并根据各个最优解的模糊隶属度和熵权信息从帕累托前沿曲线中确定出折中最优解,作为多目标无功优化控制方案。通过对某个6056节点交直流互联系统的计算表明,所提出的算法求得的帕累托最优解集分布均匀,且所获得的多目标无功优化控制方案能够有效降低换流站运行损耗,提高关键节点的电压质量。     

Valuation of reactive power support services based on sensitivity and risk analysis

In deregulated power market environment system operators need to procure adequate reactive power support services to facilitate real power transactions and improve system security. However, reactive power produced by suppliers at different locations may have different effects on the economics and operating security of the system. Thus, the assessment of the value of these reactive power support services is an important issue to be dealt with. With this objective an evaluation methodology based on voltage sensitivity and risk analysis is proposed from the perspective of voltage regulation. The IEEE 14-node test system is used to illustrate and examine the features of the proposed methodology. Some interesting results are observed and discussed.     

改进粒子群优化算法在电力系统多目标无功优化中应用

采用自适应聚焦粒子群优化(AFPSO)算法对电力系统进行无功优化.以最优控制原理为基础,引入静态电压稳定性指标,建立了综合考虑系统有功网损最小、电压水平最好以及静态电压稳定裕度最大的多目标无功优化模型,并采用模糊集理论将此多目标优化问题转化为单目标优化问题.通过最小化各目标的隶属度最大值(指标差的隶属度值大),从而只提升差的指标,使系统整体性能提高.同时,采用罚函数的形式处理负荷节点电压和无功发电功率2个状态变量不等式约束.在IEEE 57节点系统上进行测试,通过仿真测试及不同算法优化结果的对比,表明AFPSO算法在实现系统经济运行的同时也增强了电网的电压稳定,同时证明了AFPSO算法的有效性和优越性.     

海上风电场自适应多目标无功优化控制策略

针对传统固定权重多目标无功优化在应对新型电力系统复杂多变的工况时无法针对实时工况做出最合适的控制决策的问题,提出了一种自适应多目标无功优化控制策略,该策略以系统有功网损和并网点电压偏离量的加权最小作为目标函数,目标函数的权重系数根据并网点电压的偏离情况自适应调节。首先,分析海上风电场并网点电压波动与有功、无功输出的关系,建立相应的无功分配模型,并针对风电机组及静止无功发生器（static var generator,SVG）的输入输出特性,建立相应的无功控制模型。此外,考虑海上运行的功率约束、安全运行约束等,采用变惯性权重粒子群优化算法对无功控制策略进行求解。最后,在MATLAB中搭建海上风电场模型进行仿真验证,仿真算例表明：相较于传统固定权重多目标无功优化,自适应多目标无功优化控制策略可以根据电网实时工况,迅速调整各优化目标的优先级,较好地实现有功网损和并网点电压的协调优化。     

基于风险的电力市场无功电源评估

提出一种在电力市场中评估无功电源重要性的新方法:结合无功功率自身特点,根据无功电源对于系统安全的风险来确定无功电源的重要程度。其中,风险指标被用来描述各个无功电源的重要性。该指标能够有效地反映系统的不确定性以及由于无功出力变化所带来的后果影响。最后通过新英格兰系统的算例验证了该方法的有效性。     

考虑暂态电压稳定的含高渗透率风光的电网动态无功规划方法

随着电网中风电、光伏渗透率的逐渐提高,电网暂态电压稳定问题愈加严重,提出一种考虑暂态电压稳定的含高渗透率风光的电网动态无功规划方法。构造基于电压二元表的区域暂态电压安全裕度指标和无功规划基准场景;基于所提指标给出动态无功补偿装置的布点方法,建立差异化动态无功补偿优化模型,利用多目标灰狼优化算法求解配置容量,并采用改进的熵权逼近理想解距离法筛选出动态无功补偿装置的待配置方案;利用摄动法确定最终配置方案,确保所得规划方案适用于所有场景。改进的IEEE 39节点系统和实际电网的仿真结果验证了所提规划方法的普适性和合理性。     

Reactive power market development considering power system security

In the new open access environment, in pursuit of profit, power producers tend to operate closer to the security boundaries and consequently, the voltage instability, which is caused by insufficient reactive power support, threats system security and reliability. This paper presents a day-ahead reactive power market based on uniform auction price scheme considering voltage security. First, expected payment function (EPF), identified earlier in the literature to construct a bidding framework for synchronous generators, is modified. Then, the modified EPF is used as the objective function of optimal power flow problem to clear reactive power market. Finally, the OPF, including overload, voltage drop and voltage stability margin in its constraints, is solved by binary coded genetic algorithm. The validity of the proposed reactive power market is studied based on the IEEE 24-bus reliability test system.     

A particle swarm optimization for reactive power and voltagecontrol considering voltage security assessment

This paper presents a particle swarm optimization (PSO) for reactive power and voltage control (volt/VAr control: VVC) considering voltage security assessment (VSA). VVC can be formulated as a mixed-integer nonlinear optimization problem (MINLP). The proposed method expands the original PSO to handle a MINLP and determines an online VVC strategy with continuous and discrete control variables such as automatic voltage regulator (AVR) operating values of generators, tap positions of on-load tap changer (OLTC) of transformers, and the number of reactive power compensation equipment. The method considers voltage security using a continuation power flow and a contingency analysis technique. The feasibility of the proposed method is demonstrated and compared with reactive tabu search (RTS) and the enumeration method on practical power system models with promising results     

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。     

电力市场初期两部制无功定价方法

提出了一种电力市场初期的两部制无功定价方法,以有功电能成本和无功电量成本最优为目标函数,以潮流方程为等式约束,以运行及安全约束为不等式约束。建议的内点非线性规划法原理简单、计算量小。所提两部制无功电价模型的核心想法为:一方面,提出电力市场下无功源以运行成本参与竞争,以解决现有的一部制电价对无功的运行成本补偿不足的问题;另一方面,提出一种新的无功容量电价分解方案,以解决现有的一部制电价对无功投资成本回收不明确的问题。电量电价加容量电价形成了建议的两部制无功电价。IEEE-30节点系统算例验证了建议的无功优化算法和无功价格模型的有效性和实用性。     

基于无功辅助服务补偿的发电厂AVC系统机组无功出力分配策略

运行机组间无功出力分配是发电厂AVC系统的重要技术环节,分配策略的优劣影响着AVC控制的安全性及发电厂运行的经济性。从提高发电厂收益角度,提出了基于无功辅助服务补偿的发电厂AVC系统机组无功出力分配策略,建立了优化模型。该优化模型考虑了发电厂参与无功辅助服务后机组及变压器损耗增加的成本,在满足调度机构AVC系统下发的控制目标及机组安全运行等约束条件的前提下,以电厂收益最大为优化目标,求取参与AVC控制机组的无功出力控制量并下发相应机组执行。算例仿真验证了基于无功辅助服务补偿后发电厂运行机组间无功出力分配的有效性,能在满足调压要求的同时明显地提高电厂的经济效益。