Genetic algorithm-based fuzzy multi-objective approach to congestion management using FACTS devices

This paper investigates a novel optimization-based methodology for placement of Flexible AC Transmission Systems (FACTS) devices in order to avoid congestion in the transmission lines while increasing static security margin and voltage profile of a given power system. The optimizations are carried out on the basis of location, size, and number of FACTS devices. Thyristor Controlled Series Compensator (TCSC) and Static Var Compensator (SVC) are two FACTS devices which are implemented in this investigation to achieve the determined objectives. The problem is formulated according to Sequential Quadratic Programming (SQP) problem in the first stage to accurately evaluate static security margin with congestion alleviation constraint in the presence of FACTS devices and estimated annual load profile. In the next stage a Genetic Algorithm (GA)-based fuzzy multi-objective optimization approach is used to find the best trade-off between conflicting objectives. The IEEE 14-bus test system is selected to validate the proposed approach.     

Minimization of voltage sag induced financial losses in distribution systems using FACTS devices

Voltage sag can have significant economic consequences for different types of industries. Flexible AC Transmission System (FACTS) is originally developed for transmission networks but similar ideas are now starting to be applied in distribution systems. FACTS devices have become popular as a cost effective solution for the protection of sensitive loads from voltage sag. This paper presents the modeling of FACTS devices to minimize the voltage sag induced financial losses. The overall system financial losses due to voltage sag could be significantly reduced depending on the type of FACTS devices used. The short circuit analysis approach is used to incorporate the effect of these devices on financial losses. Voltage sag produced by balanced and unbalanced short circuits is analyzed by means of an analytical approach using system impedance matrix (Z_Bus) which incorporates FACTS devices. Two types of FACTS devices, which are most often used in practical applications, are considered in this study: Distribution Static Compensator (D-STATCOM) and Static VAR Compensator (SVC). Case studies based on a real Indian distribution system are used to illustrate the modeling method and the effectiveness of these devices in minimization of financial losses.     

ATC with ZIP load model – A comprehensive evaluation with third generation FACTS in restructured electricity markets

In this paper, an optimal power flow based approach has been applied for multi-transactions in deregulated environment for ATC determination with third generation FACTS devices. The main contribution of the paper is (i) OPF based approach for evaluation of ATC with multi-transactions, (ii) ATC enhancement with third generation FACTS devices viz. Static Compensator (STATCOM), Static Synchronous Series Compensator (SSSC), and Unified Power Flow Controller (UPFC) for intact and line contingency cases (iii) Impact of ZIP load on ATC determination and comparison of ATC obtained with ZIP load model and constant P,Q load model, (iv) Comparison of ATC obtained with DC/AC-PTDFs based method along with FACTS devices for comparison. The results have been determined for intact and line contingency cases taking simultaneous as well as single transaction cases for IEEE 24 bus RTS.     

一种可配置的FACTS实验系统的研究

为了能够全面地了解FACTS系统的特性，本文建立了一台可配置的FACTS实验系统。根据不同的要求可以实现STATCOM、SSSC、DVR以及UPFC的功能。通过建立FACTS系统的状态空间模型，结合对不同FACTS系统工作的矢量图分析，设计了相应的控制系统。最后分别对上述四种FACTS系统进行了相应的实验，实验结果表明这种可配置的FACTS实验系统能够较好的实现上述四种FACTS系统的功能，它为研究设计、改进和验证FACTS控制系统提供了一个实验平台。     

多FACTS元件控制变量配对方法与协调投运策略

多个灵活交流输电系统(FACTS)元件接入系统中各FACTS元件控制器间存在负的交互影响。针对已有的变量配对方法和交互影响分析方法存在的局限和不足,根据NI指数理论,提出适用于大规模、多变量的基于NI指数的多控制变量配对方法,运用该方法找到使得控制器间交互影响最小的控制变量最优配对组合。通过对最优配对组合进行分析,得到最优配对组合中与交互影响的严重程度关系最大的一组输入-输出变量。依据这一关系,制定出相应的多FACTS元件协调投入控制策略。以第二代串联型FACTS元件——静止同步串联补偿器(SSSC)为例,通过仿真系统的计算与分析,证明了所提出的多控制变量配对方法的可行性;并利用PSCAD搭建了含多个SSSC元件的系统进行仿真验证,证明了所制定的协调投运策略是可行、实用的。     

FACTS对电力系统静态安全性影响评价指标体系研究

针对目前评价灵活交流输电系统（FACTS）系统稳态性能影响指标的不足,结合FACTS设备自身控制潮流和电压的工作特性,提出了一套全面评估FACTS设备对系统静态安全性影响的指标体系。建立了基于运行状况的晶闸管控制串联电容器（TCSC）、静止无功补偿器（SVC）、统一潮流控制器（UPFC）可靠性模型,并基于该模型提出了FACTS设备的控制策略,该策略以状态量越限值最小为控制目标。建立了采用蒙特卡罗仿真的概率评估算法。通过IEEE-57节点的计算验证了所提指标体系和算法的有效性。     

A non-dominated Sorting Hybrid Cuckoo Search Algorithm for multi-objective optimization in the presence of FACTS devices

In this paper, a proposed Non-dominated Sorting Hybrid Cuckoo Search Algorithm (NSHCSA) for multi objective optimal power flow problem with FACTS devices namely Thyristor Controlled Series Compensator (TCSC) and Static Synchronous Series Compensator (SSSC) with different objective functions including the installation cost of FACTS devices are presented. The practical and operating constraints are considered for this analysis. The location of the FACTS device is selected to enhance the system security with respect to minimizing line overloads and bus voltage violations. The proposed Hybrid Cuckoo Search Algorithm (HCSA) is the combination of Cuckoo Search Algorithm (CSA) and Genetic Algorithm (GA). For multi objectives selected Pareto front is obtained by using the fuzzy decision making tool. The effectiveness of the proposed method is tested on standard IEEE-30 bus test system in the presence of the TCSC and SSSC. The results are analyzed and compared with existing methods.     

计及FACTS装置的概率特征根分析

概率特征根分析计及了较宽范围的系统运行方式变化,利用柔性交流输电系统FACTS(Flexible AC Transmission System)装置上的附加控制器可以改善系统的动态特性,将现有的概率特征根分析扩展到包含FACTS功能模块。以并联型静态无功补偿器SVC(Static Var Compensator)和串联型可控串联补偿器TCSC(Thyristor-Controlled Series Capacitor)为例,在原有概率特征根模型的基础上,依据具体的元件模型和控制器表达,确定了形成系统状态空间方程时的相应线性化表达式;详细讨论了功能增加后系统状态方程矩阵的形成;通过补充相关的灵敏度计算,完成了计及FACTS装置的电力系统多运行方式下的小干扰稳定性分析。最后,在一个八机系统上进行了试算。在选定的附加控制器参数下,比较了增加SVC前后的系统主导特征根的变化,考察了附加控制器增益变化对临界特征根的影响。     

An adaptive approach for three zone operation of digital distance relay with Static Var Compensator using PMU

Modern energy transmission systems suffer from great voltage dropping due to enormous loads. Therefore appropriate schemes should be devised to regulate the voltage. FACTS devices such as Static Var Compensator are often used for this purpose. However, SVC at mid-point of transmission line may leads to deteriorate of distance relay operation, resulting in inaccurate estimation of faults locations i.e. over-reach or under reach for different cases. This paper proposed a new algorithm that utilizes synchronized phasors measurement (SPM) to enhance the operation of distance protection zone in many aspects. The proposed method is tested for 230 kV system simulated in EMTDC/PSCAD with Bergeron model of transmission line. The results prevailed for adaptive approach scheme are more accurate, victor and robust in equivalence with usable transmission line distance protection with SVC.     

SVM based zonal setting of Mho relay for shunt compensated transmission line

Presence of shunt FACTS (Flexible Alternating Current Transmission System) device significantly affect the performance of protection system and may create security and reliability issues. This paper introduces a novel approach for zone identification in transmission line employing shunt FACTS devices such as Static Var Compensator (SVC) and Static Synchronous Compensator (STATCOM). The technique depends on the modified apparent impedance seen by the impedance relay for all possible operating conditions. In this technique the Support Vector Machine (SVM) is used for discriminating faulty zone (zone 1 or zone 2). In addition an optimization technique viz. Genetic Algorithm (GA) is used to optimize SVM parameters. A typical 230 kV system was simulated in PSCAD/EMTP software and the results show that the proposed scheme is secure, accurate and reliable under the wide variation in power system parameters like load angle, fault resistance, fault location, inception angle and compensation level.     

Power flow control approach to power systems with embedded FACTS devices

This paper focuses on developing an approach to steady-state power flow control of flexible AC transmission systems (FACTS) device-equipped power systems. Based on a power-injection model of FACTS devices and an optimal power flow model, a novel versatile power flow control approach is formulated, which is capable of implementing power flow control incorporating any FACTS device flexibly. Different from existing FACTS device control approaches, the active and (or) reactive power injections are taken as independent control variables. Therefore, using this method, Jacobian matrix need not be changed, although various FACTS devices possess different physical models and different control parameters. Furthermore, it enables the integration of FACTS devices into the existing power system analysis and control programs efficiently. Physical limits of the FACTS devices are also considered in the model. Numerical results on a reduced practical system and a 1500-bus practical system with various FACTS devices are presented to illustrate the vigorousness of the proposed approach.     

Pole placement by coordinated tuning of Power System Stabilizers and FACTS-POD stabilizers

This work presents the application of the Decentralized Modal Control method for pole placement in multimachine power systems utilizing FACTS (Flexible AC Transmission Systems), STATCOM (Static Synchronous Compensator) and UPFC (Unified Power Flow Controller) devices. For this, these devices are equipped with supplementary damping controllers, denominated POD (Power Oscillation Damping), achieving a coordinated project with local controllers (Power System Stabilizers - PSS). Comparative analysis on the function of damping of the FACTS, STATCOM and UPFC is performed using the New England System that has 10 generators, 39 buses and 46 transmission lines.     

Power system with multi-type FACTS devices states estimation based on predictor–corrector interior point algorithm

This paper addresses a state estimation problem of power systems incorporating various flexible alternating current transmission system (FACTS) devices. Static var compensators, thyristor controlled series compensators, and unified power flow controllers are considered since they represent various kinds of FACTS devices. By considering constraints of system buses and devices, the estimation problem can be formulated as a nonlinear optimization with constraints. An algorithm based on predictor–corrector interior point is applied to solve the problem. The IEEE 14- and 118-bus systems modified by incorporating FACTS devices are used as test systems to verify and demonstrate the effectiveness of the proposed algorithm. Numerical results indicate that the proposed algorithm performs better than the primal dual interior point based method even the presence of bad measurement data.     

OPF with SVC and UPFC modeling for longitudinal systems

This paper presents a formulation of the Optimal Power Flow problem with an explicit modeling of Static Var Compensator (SVC) and Unified Power Flow Controller (UPFC) devices. The optimization problem is solved by using Sequential Quadratic Programming, where two convergence criteria and four different methods are studied to solve the quadratic subproblems. The proposed model is integrated in an object-oriented based decision support platform for competitive power markets. Validation of the method and practical applications to real longitudinal systems are discussed, where FACTS location and a UPFC-based interconnection are described. Results show the impact of SVC and UPFC FACTS technologies in the physical and economic behavior of a real system.     

WLAV state estimation for power system containing multitype FACTS devices

This paper presents the state estimation of power system in which not only the bus voltages but also the states of the flexible AC transmission system (FACTS) are considered as the state variables. By using the rectangular form of state variables and equivalent measurement techniques, a linear measurement model with constraints of FACTS device is obtained. The predictor–corrector interior point method based on the weighted least absolute value criterion is developed for solving the optimization problem. Simulation results on the modified IEEE 14‐bus and 118‐bus test systems are provided. The numerical results indicate the effectiveness of the proposed approach. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Swarm intelligence based algorithms for reactive power planning with Flexible AC transmission system devices

In the proposed work, authors have applied swarm intelligence based algorithms for the effective Co-ordination of Flexible AC transmission system (FACTS) devices with other existing Var sources present in the network. IEEE 30 and IEEE 57 bus systems are taken as standard test systems. SPSO (Simple Particle Swarm Optimization) and other two swarm based intelligence approaches like APSO (Adaptive Particle Swarm Optimization) and EPSO (Evolutionary Particle Swarm Optimization) are used for the optimal setting of the Var sources and FACTS devices. The result obtained with the proposed approach is compared with the result found by the conventional RPP (Reactive power planning) approach where shunt capacitors, transformer tap setting arrangements and reactive generations of generators are used as planning variables. It is observed that reactive power planning with FACTS devices yields much better result in terms of reducing active power loss and total operating cost of the system even considering the investment costs of FACTS devices.     

A new coordination strategy of SSSC and PSS controllers in power system using SOA algorithm based on Pareto method

Along with the development of power grids and increasing the use of Flexible AC Transmission System (FACTS) devices, complex and unexpected interactions will be increased in power system. With considering to the non-linearity of power system, operating point changes and reaction between power system and FACTS devices, using of linear methods are not suitable for controller design. Therefore, the nonlinear model to design of Power System Stabilizer (PSS) and Static Synchronous Series Compensator (SSSC) coordinated controllers is considered here. In this paper, a new multi-objective function as an optimization problem is proposed for this coordination process. Also a beneficial strategy to solve this optimization problem using Seeker Optimization Algorithm (SOA) based on Pareto optimum method with high convergence speed is presented. In order to evaluate the performance of the proposed method, coordination strategy is applied on a four-machine system under different contingencies. The results of the proposed multi-objective function are obtained and compared with others in this system and finally, superior ability of the proposed method is observed.     

Optimal placement and parameter setting of SVC and TCSC using PSO to mitigate small signal stability problem

This paper aims to select the optimal location and setting parameters of SVC (Static Var Compensator) and TCSC (Thyristor Controlled Series Compensator) controllers using PSO (Particle Swarm Optimization) to mitigate small signal oscillations in a multimachine power system. Though Power System Stabilizers (PSSs) associated with generators are mandatory requirements for damping of oscillations in the power system, its performance still gets affected by changes in network configurations, load variations, etc. Hence installations of FACTS devices have been suggested in this paper to achieve appreciable damping of system oscillations. However the performance of FACTS devices highly depends upon its parameters and suitable location in the power network. In this paper the PSO based technique is used to investigate this problem in order to improve the small signal stability. An attempt has also been made to compare the performance of the TCSC controller with SVC in mitigating the small signal stability problem. To show the validity of the proposed techniques, simulations are carried out in a multimachine system for two common contingencies, e.g., load increase and transmission line outage. The results of small signal stability analysis have been represented employing eigenvalue as well as time domain response. It has been observed that the TCSC controller is more effective than SVC even during higher loading in mitigating the small signal stability problem.     

含FACTS元件的电力系统非线性最优潮流计算

根据FACTS 元件的控制原理分别建立适合于最优潮流计算的数学模型,便于给定其计算初值和可行域。提出采用直接非线性路径跟踪算法求解含FACTS元件的电力系统最优潮流模型,研究了FACTS元件的支路潮流控制对该算法的影响。IEEE 30节点和IEEE 118节点系统的优化计算结果表明该算法不仅具有强大的处理不等式约束的能力,而且还具有较强的适应支路功率定向定值控制的能力,但其收敛性要受到FACTS元件的数目及安装地点的影响。     

Optimal power flow with FACTS devices by hybrid TS/SA approach

In this paper, a hybrid tabu search and simulated annealing (TS/SA) approach is proposed to minimize the generator fuel cost in optimal power flow (OPF) control with flexible AC transmission systems (FACTS) devices. The problem is decomposed into the optimal setting of FACTS parameters subproblem that is searched by the hybrid TS/SA approach and the OPF with fixed FACTS parameters subproblem that is solved by the quadratic programming (QP). Two types of FACTS devices are used: thyristor-controlled series capacitor (TCSC) and thyristor-controlled phase shifting (TCPS). Test results on the modified IEEE 30 bus system indicates that the proposed hybrid TS/SA approach can obtain better solutions and require less CPU times than genetic algorithm (GA), SA, or TS alone.