Analysis of radial distribution systems with embedded series FACTS devices using a fast line flow-based algorithm

Analysis of radial distribution systems with embedded series Flexible AC Transmission System (FACTS) devices is facilitated by a formulation of power flow equations with bus voltage magnitudes and line flows as independent variables. Since control variables such as the line and bus reactive powers figure directly in the formulation, handling the control action of FACTS devices in distribution systems is direct and easily implemented. Using the Breadth-First-Search (BFS), the bus incidence matrix of a radial distribution system is first rendered strictly upper diagonal, leading to reduced computational effort. All the common FACTS device models under steady-state conditions are easily incorporated in the new framework by a simple process of "variable swapping." Using IEEE standard systems, the line flow-based (LFB) formulation is shown to provide easy implementation with multiple series and shunt FACTS devices in the system and enable direct evaluation of the FACTS device ratings.     

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。     

A new hybrid state estimation based on pseudo‐voltage measurements

This paper presents a new hybrid state estimation method based on the concept of pseudo‐voltage measurements for a power system containing both conventional and synchronizing phasor measurements. Actual measurement data is employed to calculate the magnitude and phase of the pseudo‐voltage. In the proposed formulation, the measurement matrix describing the relations between the measured data and the state variables contains only 0 or 1. Then the state estimation problem is formulated based on the weighted least‐squares criterion, and its solution can be obtained without using iterative procedures. Comparisons with previous hybrid state estimation methods have been performed on IEEE 14‐bus, 57‐bus, and 118‐bus systems. Numerical experimental results indicate that the proposed approach yields solutions of comparable accuracy with other methods but with shorter computation times. Moreover, the proposed method also provides superior results in the presence of bad data. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A new dynamic control strategy for power transmission congestion management using series compensation

The growth of electricity market due to increase in demand and infrastructure made the power system more complex. Managing the transmission congestion is one of the main challenges faced by the utilities. To relieve from the bottlenecks, Flexible AC Transmission Systems (FACTS) and Distributed FACTS (D-FACTS) devices can be used in controlling the transmission line power flows. The real power flow control is realized by varying the transmission line impedance. The power flow in transmission line should satisfy inequality constraints to maintain the system in normal state. To achieve this, an algorithm is developed to control the FACTS/D-FACTS devices connected to all the transmission lines of n-bus system. The significant changes required in line impedance which will be deployed by FACTS devices are decided by the algorithm. In this paper, a 5 bus system and a 14 bus system with FACTS devices in all the transmission lines is considered. The transmission lines of the 5 and 14 bus systems are made to be overloaded in different combinations by choosing appropriate loading conditions. The control algorithm is tested on all the overloaded conditions to overcome the congestion. The FACTS devices controlled by the algorithm removes the overloading effect and improve the reliability of the network.     

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。     

STATCOM versus SSSC for power system stabilization

Flexible alternating current transmission systems (FACTS ) are gaining more attention in power utilities because of their advantages of controllability, reliability, and operation over a wide range. Static synchronous compensator (STATCOM) and static series synchronous compensator (SSSC ) are prominent FACTS topologies; they have the ability to instantaneously regulate active/reactive powers and stabilize the power system following severe disturbances. In this paper, STATCOM and SSSC are compared with regard to their damping action on power system oscillations. The comparison is extended to the controller design strategies. Two distinct meta‐heuristic optimization approaches, namely chaos (CO) and simulated annealing (SA), are recommended for the optimal design of the SSSC and STATCOM damping controller. To assess the promising FACTS topology, a single‐machine infinite bus system is subjected to several disturbances while operating at different loading levels. MATLAB/Simulink is used as a platform to investigate the dynamic performance of the system under consideration with STATCOM and SSSC . Simulation results reveal the superiority of SSSC in damping power system oscillations in terms of response speed and stability margin. Moreover, the CO optimization scheme seems to outperform the SA algorithm in terms of computation requirements and global optimal convergence. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

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.     

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.     

Application of particle swarm optimization technique for optimal location of FACTS devices considering cost of installation and system loadability

This paper presents the application of particle swarm optimization (PSO) technique to find the optimal location of flexible AC transmission system (FACTS) devices with minimum cost of installation of FACTS devices and to improve system loadability (SL). While finding the optimal location, thermal limit for the lines and voltage limit for the buses are taken as constraints. Three types of FACTS devices, thyristor controlled series compensator (TCSC), static VAR compensator (SVC) and unified power flow controller (UPFC) are considered. The optimizations are performed on the parameters namely the location of FACTS devices, their setting, their type, and installation cost of FACTS devices. Two cases namely, single-type devices (same type of FACTS devices) and multi-type devices (combination of TCSC, SVC and UPFC) are considered. Simulations are performed on IEEE 6, 30 and 118 bus systems and Tamil Nadu Electricity Board (TNEB) 69 bus system, a practical system in India for optimal location of FACTS devices. The results obtained are quite encouraging and will be useful in electrical restructuring.     

基于相对增益矩阵和 Prony 技术的南方电网FACTS 和 HVDC 之间交互影响分析

高压直流输电(HVDC)及灵活交流输电(FACTS)装置因其优良特性被广泛应用于现代电网中,但是其实际应用时间较短,加之其控制器的复杂性,使得对大规模交直流混联电网中 FACTS 装置之间及 FACTS 装置与 HVDC 间的交互作用的研究不够成熟和完善.文中以定量分析南方电网中FACTS 装置之间以及 FACTS 装置与 HVDC 系统间的交互作用大小为目标,建立了含 FACTS 装置和 HVDC 系统的多机电力系统的线性化模型,并详细阐述了引入不同 FACTS装置及直流系统时,控制变量、输出变量的选择及对代数方程的处理.接着对南方电网进行等值,利用该线性化模型推导出等值系统的传递函数,利用 RGA 方法找出 FACTS 装置之间以及 FACTS 装置与 HVDC 系统间的交互作用的大小.最后通过大扰动下的 Prony 分析验证了 RGA 分析结果的正确性.     

Loadability enhancement with FACTS devices using gravitational search algorithm

In the present work, GSA (gravitational search algorithm) based optimization algorithm is applied for the optimal allocation of FACTS devices in transmission system. IEEE 30 & IEEE 57 test bus systems are taken as standards. Both active and reactive loading of the power system is considered and the effect of FACTS devices on the power transfer capacity of the individual generator is investigated. The proposed approach of planning of reactive power sources with the FACTS devices is compared with other globally accepted techniques like GA (Genetic Algorithm), Differential Evolution (DE), and PSO (Particle Swarm Optimization). From the results obtained, it is observed that incorporating FACTS devices, loadability of the power system increases considerably and each generator present in the system is being able to dispatch significant amount of active power under different increasing loading conditions where the steam flow rate is maintained corresponding to the base active loading condition. The active power loss & operating cost also reduces by significant margin with FACTS devices at each loading condition and GSA based planning approach of reactive power sources with FACTS devices found to be the best among all the methods discussed in terms of reducing active power loss and total operating cost of the system under all active and reactive loading situations.     

扩展等面积法暂态稳定分析的FACTS控制器模型

提出了应用扩展等面积法（EEAC）暂态稳定分析的FACTS控制器统一模型,将FACTS对暂态稳定的作用通过对电力系统的串联和并联控制来描述。研究了这一模型对电力系统网络方程、转子运动方程和EEAC单机无穷大系统等值的影响,推导了适合于EEAC各种方法和各类FACTS控制器的单机无穷大（OMIB）系统等值统一表达式。该模型被应用于伊-冯500 kV可控串补的EEAC暂态稳定分析,并应用中国电力科学研究院电力系统分析综合程序进行了校核,结果证明了这种FACTS模型是有效和正确的。     

State estimation of power systems containing facts controllers

This paper proposes a practical approach to incorporate Flexible AC Transmission Systems (FACTS) devices into a Weighted Least Squares (WLS) state estimation algorithm. The FACTS devices included in the estimator are the Thyristor Controlled Series Compensator (TCSC), the Static Var Compensator (SVC), and the Unified Power Flow Controller (UPFC). The proposed approach simultaneously upgrades the estimated values of the state variables of these devices and the state variables of the rest of the electric network, for a unified solution in a single-frame of reference. Results are presented to demonstrate the effectiveness of the proposed approach to assess the estimation of the system state and to set the parameters of FACTS controllers for given control specifications.     

基于临界能量灵敏度法研究FACTS的暂态稳定控制

介绍用临界能量对电力网络参数的灵敏度法研究FACTS的暂态稳 定控制。通过对灵敏度较大的线路或母线上FACTS设备参数进行控制,以提高FACTS的暂态稳 定性。对10机39母线系统的仿真结果表明,临界能量灵敏度法是提高FACTS暂态稳定性的有 效控制措施。     

Experimental study on the Unified Power Flow Controller

This paper presents the results of experimental study on the performance of a Unified Power Flow Controller (UPFC), one of the FACTS (Flexible AC Transmission Systems) controllers. A laboratory‐scale UPFC was manufactured and installed on a laboratory electric power system to investigate its multifunctional capabilities as a power flow controller. The UPFC consists of two 4.5‐kVA, 200‐V back‐to‐back voltage‐sourced converters, labeled “Converter 1” and “Converter 2,” operated from a common DC link provided by a DC storage capacitor of 380 V. It can provide independent control of both the real and reactive power flow in the line. Tests were performed to examine the capabilities of the UPFC, under one‐machine connected to an infinite‐bus system. Steady‐state responses under various kinds of operating conditions were measured and analyzed. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(2): 8– 15, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20538     

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.     

Free‐weighting matrices‐based robust wide‐area FACTS control design with considering signal time delay for stability enhancement of power systems

This paper presents a free‐weighting matrix (FWM) method based on linear control design approach for the wide‐area robust damping (WARD) controller associated with flexible AC transmission system (FACTS) device to improve the dynamical performance of the large‐scale power systems. First, the linearized reduced‐order plant model is established, which efficiently considers the time delay of the remote feedback signals transmitted by wide‐area measurement systems. Then, based on the robust control theory, the design of the FACTS‐WARD controller is formulated as the standard control problem on delay‐dependent state‐feedback robust control, which is described by a set of linear matrix inequality constraints. Furthermore, in order to obtain the optimal control parameters that can endure the maximum time delay, a FWM approach is proposed to solve the time‐dependent problem of the time‐delay system. Meanwhile, an iterative algorithm based on cone complementary linearization is presented to search out the optimal control parameters. Finally, the nonlinear simulations on the 2‐area 4‐machine and the 5‐area 16‐machine test systems are performed, to evaluate the control performance of the proposed robust wide‐area time‐delay control approach. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

FACTS装置对含风电互联系统低频振荡特性分析

随着电力系统互联加强,风电并网容量的增加对电网的稳定运行影响越来越大。构建了以UPFC(Unified Power Flow Controller, UPFC)和SVC(Static Var Compensator, SVC)为代表的FACTS装置与含风电系统的数学模型。采用留数指标定位FACTS装置,设计了附加阻尼控制器(Additional Damping Controller, ADC)。基于IEEE 2区域4机互联系统,从特征根分析和时域仿真两个方面分析了FACTS装置对含风电互联系统低频振荡特性的影响。研究结果表明,加装附加阻尼控制器的FACTS装置能够维持母线电压以及发电机转速的稳定,增加互联系统联络线功率传输范围,抑制低频振荡引起的电网参数波动,改善了含风电电力系统的低频振荡特性。     

Optimal worst case solutions for state estimation of power system with uncertain network parameters

This paper addresses the problem of power system state estimation under the condition that transmission line network parameters are unknown but bounded. A robust estimation in the sense of an optimal worst case solution is determined. Data collected via remote terminal units, i.e. voltage magnitude, power flow, and power injection, are used as measurement quantities. The state variables are bus voltage phasors expressed in rectangular coordinates. This makes it possible to express the relations between measured data and state variables as quadratic functions. The proposed formulation based on the structured robust least squares optimization yields a minimization problem with bilinear matrix inequality constraints. A solution method based on semidefinite programming is also presented. Some test results on the standard IEEE test systems are given. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

大型发电机组调速器的非线性最优PSS

提出了一种大型水电站调速系统的非线性最优电力系统稳定器(PSS)的原理和技术.该技术的关键是采用了状态-动态-测量(SDM)的反馈方法.计算机仿真和动模实验证明,利用该方法推导出的水电站调速系统非线性最优PSS(GNOPSS)控制规律能够显著提高远距离输电系统的安全稳定性,其效能价格比远超过多种FACTS设备,且与FACTS设备的效果是叠加的,不发生矛盾.该研究成果同样适用于大型火电机组的汽门开度调节系统.