Congestion management enhancing transient stability of power systems

In a competitive electricity market, where market parties try to maximize their profits, it is necessary to keep an acceptable level of power system security to retain the continuity of electricity services to customers at a reasonable cost. Congestion in a power system is turned up due to network limits. After relieving congestion, the network may be operated with a reduced transient stability margin because of increasing the contribution of risky participants. In this paper, a novel congestion management method based on a new transient stability criterion is introduced. Using the sensitivity of corrected transient stability margin with respect to generations and demands, the proposed method so alleviates the congestion that the network can more retain its transient security compared with earlier methods. The proposed transient stability index is constructed considering the likelihood of credible faults. Indeed, market parties participate by their security-effective bids rather than raw bids. Results of testing the proposed method along with the earlier ones on the New-England test system elaborate the efficiency of the proposed method from the viewpoint of providing a better transient stability margin with a lower security cost.     

Multi-objective congestion management by modified augmented ε-constraint method

Congestion management is a vital part of power system operations in recent deregulated electricity markets. However, after relieving congestion, power systems may be operated with a reduced voltage or transient stability margin because of hitting security limits or increasing the contribution of risky participants. Therefore, power system stability margins should be considered within the congestion management framework. The multi-objective congestion management provides not only more security but also more flexibility than single-objective methods. In this paper, a multi-objective congestion management framework is presented while simultaneously optimizing the competing objective functions of congestion management cost, voltage security, and dynamic security. The proposed multi-objective framework, called modified augmented ε-constraint method, is based on the augmented ε-constraint technique hybridized by the weighting method. The proposed framework generates candidate solutions for the multi-objective problem including only efficient Pareto surface enhancing the competitiveness and economic effectiveness of the power market. Besides, the relative importance of the objective functions is explicitly modeled in the proposed framework. Results of testing the proposed multi-objective congestion management method on the New-England test system are presented and compared with those of the previous single objective and multi-objective techniques in detail. These comparisons confirm the efficiency of the developed method.     

Reactive power market management considering voltage control area reserve and system security

This paper presents a new algorithm to optimize reactive power procurement through commercial transactions considering system voltage security. The proposed algorithm minimizes reactive power provision and transmission loss costs in addition to maximizing system voltage security margin through a multiobjective function. In order to maintain the voltage profile of power system during sever contingencies or due to load uncertainty, all voltage control areas (VCA) of the system are detected and then optimal reactive power reserve is provided for each VCA during the market settlement. A four-stage multiobjective mathematical programming method is proposed to settle the reactive power market. The proposed algorithm has been applied on IEEE-RTS test system. The simulation results show the effectiveness of the proposed algorithm for reactive power market management.     

应用基于连续潮流法的改进差异进化算法分析静态电压的稳定裕度

连续潮流法能较好克服潮流方程在极限点附近的病态，是求取静态电压稳定裕度的常用方法。在连续潮流法的基础上，结合经过改进的差异进化算法，通过对变量的组合优化，求取系统静态电压稳定安全裕度。对KK11节点系统的计算结果表明了对进化算法所作改进的有效性。图4表1参11     

Stochastic reactive power market with volatility of wind power considering voltage security

While wind power generation is growing rapidly around the globe; its stochastic nature affects the system operation in many different aspects. In this paper, the impact of wind power volatility on the reactive power market is taken into account. The paper presents a novel stochastic method for optimal reactive power market clearing considering voltage security and volatile nature of the wind. The proposed optimization algorithm uses a multiobjective nonlinear programming technique to minimize market payment and simultaneously maximize voltage security margin. Considering a set of probable wind speeds, in the first stage, the proposed algorithm seeks to minimize expected system payment which is summation of reactive power payment and transmission loss cost. The object of the second stage is maximization of expected voltage security margin to increase the system loadability and security. Finally, in the last stage, a multiobjective function is presented to schedule the stochastic reactive power market using results of two previous stages. The proposed algorithm is applied to IEEE 14-bus test system. As a benchmark, Monte Carlo Simulation method is utilized to simulate the actual market of given period of time to evaluate results of the proposed algorithm, and satisfactory results are achieved.     

考虑暂态电压稳定性的电力系统多目标无功备用优化

鉴于目前电力系统无功备用优化方法较少涉及暂态电压稳定性,提出一种同时提高电力系统静态/暂态电压稳定性的无功备用优化模型,该模型首先基于数据密度提出一种无功电压控制分区方法,分别在静态/暂态电压的薄弱区域内定义静态/暂态无功备用,然后结合所建立的两个目标建立多目标无功备用优化模型,最后提出一种基于多阶段的多目标优化求解方法。通过求解所建模型,获得能够同时提升系统静态/暂态电压稳定性的无功备用配置方案。对IEEE 39节点系统的仿真分析证明了所提方法的有效性。     

Derivation of Stability Limits Using Analytical Sensitivity of the Transient Energy Margin

In recent years considerable progress has been achieved in power system transient stability assessment using the transient energy function (TEF) method. Due to continued developments and enhancements, the TEF method has matured to a stage where reliable and accurate assessment of transient stability of a power system is now possible. An inherent advantage of the TEF method is the availability of a qualitative measure of the degree of stability (or instability) in terms of the transient energy margin (?V). This is an important step toward reducing the number of transient stability runs needed to obtain transient stability loading limits or to make changes to improve the system transient behavior, when subjected to large disturbances. In this paper, a procedure is presented to obtain quantitative answers for these limits by developing an analytical approach to energy margin sensitivity. The approach consists of determining sensitivity coefficients and the development of the dynamic sensitivity equations. A first order expression for the sensitivity of the energy margin is used to determine transient stability limits for the following parameter changes: i. Generation changes ii. Load changes iii. Network changes. The proposed procedure is tested on a 17-generator equivalent of the network of the State of Iowa. The results obtained are then compared with the limits obtained by repetitive application of the TEF method.     

华东电网电压静态稳定性研究

根据华东电网 1995年度运行方式 ,对系统的电压静态稳定性进行分析 ,包括确定电压静态稳定裕度、电压弱稳定区、关键支路和重要发电机组 ,求取对应于给定系统过渡方式的电压静稳极限以及判断系统失稳方式 ,对华东电网电压稳定性的分析及运行监控提供了重要依据。同时 ,计算结果验证了所采用的程序是有实用价值的     

基于BPA软件的地区电网静态电压稳定性分析

电力系统静态电压稳定分析对电力部门的电压稳定控制、调度规划等工作十分重要。基于静态模型提出了求取实际运行电网的功率-电压(P-V)曲线的方法,该方法采用电力系统潮流软件(BPA)作为计算核心,通过设计外部接口实现连续潮流仿真,进行电力系统静态电压稳定裕度分析及绘制P-V曲线。利用该方法对上海电网黄渡分区进行静态电压稳定分析,计算系统的相对电压稳定裕度,找出其存在的电压薄弱点,并提出了进一步提高静态电压稳定水平的若干措施。     

规模化光伏电站与电网暂态交互影响定量分析

在电力系统暂态安全定量分析软件平台FASTEST(Fast Analysis of Stability using the Extended equal areacriterion and Simulation Technologies)上以研究规模化光伏电站接入系统后的稳定性分析为目的,建立了一个完整而且适合系统安全稳定分析的并网光伏电站机电暂态模型。基于FASTEST特有的暂态稳定量化分析功能,对并网光伏电站被浮云遮挡和系统侧发生扰动这2种典型情况进行仿真分析,从对系统暂态功角稳定性、暂态电压稳定性和暂态频率稳定性的影响的角度,探讨光伏电站与常规电源在影响电网运行特性方面的区别。结果表明,光伏电站并网后对系统暂态频率稳定性影响最为严重,相比较于带有励磁和调速系统的同步发电机,光伏电站在网侧故障时的暂态响应特性更为剧烈。     

A novel line drop secondary voltage control algorithm for variable speed wind turbines

This paper addresses the design and implementation of the line drop secondary voltage control (LDSVC) for the doubly fed induction generator‐wind turbine (DFIG‐WT) complemented with reactive power allocation algorithm to achieve more efficient voltage regulation, reactive power compensation and to enhance the transient stability margin of the electric power system. The LDSVC is used to generate the local voltage reference, providing an improvement for overall voltage profile. The paper presents the influence of the integration of variable speed wind turbines‐based doubly fed induction generator (DFIG) while employing LDSVC for increasing the transient stability margin. This paper proposes an improved voltage control scheme, based on a secondary voltage controller complemented with an automatic gain controller (AGC). The scheme is applied to a wind energy system incorporating DFIG‐based wind turbines. The controller structure is developed and the performance of the self‐tuning AGC scheme is developed and analysed. The proposed controller is tested in response to system contingencies for different short circuit ratios. The performance of the secondary voltage control without and with AGC is verified. The influence of the AGC in improving the transient response and damping of voltage oscillations is verified. Copyright © 2010 John Wiley & Sons, Ltd.     

Attuned design of demand response program and M-FACTS for relieving congestion in a restructured market environment

This paper addresses the attuned use of multi-converter flexible alternative current transmission systems (M-FACTS) devices and demand response (DR) to perform congestion management (CM) in the deregulated environment. The strong control capability of the M-FACTS offers a great potential in solving many of the problems facing electric utilities. Besides, DR is a novel procedure that can be an effective tool for reduction of congestion. A market clearing procedure is conducted based on maximizing social welfare (SW) and congestion as network constraint is paid by using concurrently the DR and M-FACTS. A multi-objective problem (MOP) based on the sum of the payments received by the generators for changing their output, the total payment received by DR participants to reduce their load and M-FACTS cost is systematized. For the solution of this problem a nonlinear time-varying evolution (NTVE) based multi-objective particle swarm optimization (MOPSO) style is formed. Fuzzy decision-making (FDM) and technique for order preference by similarity to ideal solution (TOPSIS) approaches are employed for finding the best compromise solution from the set of Pareto-solutions obtained through multi-objective particle swarm optimization-nonlinear time-varying evolution (MOPSO-NTVE). In a real power system, Azarbaijan regional power system of Iran, comparative analysis of the results obtained from the application of the DR & unified power flow controller (UPFC) and the DR & M-FACTS are presented.     

基于模态法的静态电压稳定性分析

提出了基于模态法的静态电压稳定性分析的新方法,通过建立模态法的静态电压稳定分析数学模型,求取潮流方程雅可比矩阵的最小特征值及其相对应的特征向量,以最小模特征值来间接评估系统的静态电压稳定裕度,并在此基础上提出了参与因子指标,计算各个节点在最小特征值下的节点参与因子来找出哪些节点或区域的电压稳定性较差.通过对某大型电网进行研究,得到其相应的电压薄弱区域,并与灵敏度分析法所得到的结果进行对比,结果基本一致,从而验证了本文方法的合理性与有效性。     

Multiobjective clearing of reactive power market in deregulated power systems

This paper presents a day-ahead reactive power market which is cleared in the form of multiobjective context. Total payment function (TPF) of generators, representing the payment paid to the generators for their reactive power compensation, is considered as the main objective function of reactive power market. Besides that, voltage security margin, overload index, and also voltage drop index are the other objective functions of the optimal power flow (OPF) problem to clear the reactive power market. A Multiobjective Mathematical Programming (MMP) formulation is implemented to solve the problem of reactive power market clearing using a fuzzy approach to choose the best compromise solution according to the specific preference among various non-dominated (pareto optimal) solutions. The effectiveness of the proposed method is examined based on the IEEE 24-bus reliability test system (IEEE 24-bus RTS).     

风电并网的静态电压稳定性研究

应用P-V曲线法对含风电场（基于变速恒频机组构成）的电力系统的静态电压稳定问题进行研究。提出基于连续潮流法的灵敏度指标来分析风电场并网后系统的静态电压稳定裕度及与相关支路的参与程度情况。通过含有变速恒频机组的风电场并网的简化模型算例进行了仿真研究,结果表明在电压稳定极限点附近,风电功率注入使得风电场及其附近节点成为电压不稳定的关键区域。     

基于改进遗传算法的配电网无功优化

在传统无功优化模型的基础上,引入静态电压稳定裕度指标,建立了综合考虑系统有功网损最小、无功补偿容量最小和系统静态电压稳定裕度最大的配电网无功优化模型。根据节点无功2次电阻矩的大小,确定了待补偿节点以及各节点补偿容量的上下限。在基本遗传算法的基础上,对遗传操作进行了改进,提出了1种改进遗传算法。实例计算表明,采用该方法对配电网进行无功优化不仅可以降低有功网损,还能提高系统静态电压稳定性。     

Buffer scheme with battery energy storage capability for enhancement of network transient stability and load ride-through

This paper examines a buffer scheme to mitigate the negative impacts of power-conditioned loads on network voltage and transient stabilities. The scheme is based on the use of battery energy-storage systems in the buffers. The storage systems ensure that protected loads downstream of the buffers can ride through upstream voltage sags and swells. Also, by controlling the buffers to operate in either constant impedance or constant power modes, power is absorbed or injected by the storage systems. The scheme thereby regulates the rotor-angle deviations of generators and enhances network transient stability. A computational method is described in which the capacity of the storage systems is determined to achieve simultaneously the above dual objectives of load ride-through and stability enhancement. The efficacy of the resulting scheme is demonstrated through numerical examples.     

广东电网失稳因素研究新视角与实用方法

  目的  目前,广东电网采用的大电网安全稳定分析思路与方法能较好满足生产运行实际需求,但也存在一定不足,无法站在全局角度简单有效的厘清诸多因素对系统安全稳定的影响,无法快捷甄别系统失稳主导因素。  方法  在此背景下,按“有无对比”的思路,通过逐个“隔离”影响因素的的方法来研究各因素对系统稳定的影响,并提出了具体实现方法。  结果  采用提出的新方法对珠三角电网电压失稳问题进行了研究,分析结果表明马达负荷与常规直流的暂态特性对系统稳定均具有重大影响,马达负荷对系统稳定性更具基础性作用,常规直流无功暂态特性对系统稳定性的负面影响仅在某些特定场景才体现得较为明显。  结论  算例表明:提出的方法能快速高效分析各因素对系统安全稳定的影响,深化对事物本质的认识,并且在某些方面可以得到传统方法无法得出的结论。     

Market-clearing for pricing system security based on voltage stability criteria

This paper presents a novel technique for representing system security in the operation of decentralized electricity markets, with special emphasis on voltage stability. The market-clearing algorithm is modeled as voltage stability constrained-optimal power flow (VSC-OPF) problem for providing market solutions by means of a function of complying with the required voltage stability criteria. Benders’ decomposition is applied for solving the VSC-OPF incorporating post-contingency control actions, which is motivated by the improvement of computational efficiency using parallel processing. The proposed VSC-OPF framework also takes into consideration the bilateral contract information, which is integrated into the market-clearing process and, at the same time, the optimal pricing expressions through computing local marginal prices (LMPs) with respect to ensuring voltage stability are derived. VSC-OPF is tested on the IEEE 14-bus benchmark system and the results obtained, when compared to those obtained by means of a conventional OPF, show that the proposed technique is able to improve system security while yielding better market solutions and total transaction levels.     

贵州电网“十三五”静态电压稳定裕度的计算方法

电力系统的静态电压稳定裕度是评估系统静态稳定的重要指标,它是计算电压稳定限制的区域电力系统间输电能力的重要依据,也是系统选择是否进行预防控制措施的重要参考点。贵州电网“十三五”规划及相关专题要求对贵州电网“十三五”期间静态电压稳定裕度进行计算分析,而现有的静态电压稳定裕度分析软件如VSAP等存在计算节点数量限制,难以满足“十三五”期间贵州电网的静态电压稳定裕度计算要求,因此有必要寻求一种新的途径来求取贵州电网静态稳定裕度。文章提出了一种采用BPA潮流计算程序与MATLAB程序相结合的计算方法,BPA潮流计算程序主要用于系统的等值简化,MATLAB程序主要用于静态电压稳定裕度的计算,求解的算法采用最优潮流法。用此方法计算贵州电网“十三五”期间的静态电压稳定裕度,计算结果表明该方法有效可行,可推广应用于其他省级电网及区域电网的静态电压稳定裕度计算分析工作中。