Development of self-commutated SVC for power system

A 50-MVA self-commutated Static Var Compernsator (SVC) using the worlds's largest GTO thyristors rated 6 kV-2500 A has been developed for voltage control of electric power systems. The rated dc voltage is 16.8 kV which is four times higher than the highest one manufactured so far. To achieve the high dc voltage, eight GTO thyristors are connected in series. Voltage unbalance between GTOs during switching transient was investigated. A new overcurrent limiting method is proposed, since conventional fuse protection cannot be applied due to such high voltage. Newly developed technologies for this large and high-voltage self-commutated SVC are described. Although simple star-delta connection transformers are used, harmonics generated from SVC are almost equivalent to the 24-pulse converter by shifting the pulse timing appropriately. The PWM control based on 150 Hz is applied and the SVC is designed to continue operation during system faults. The performance of the controller is tested successfully by a simulator, and typical rest results are introduced.     

Advanced SVC control for damping power system oscillations

A new SVC (static VAR compensation) control for damping of power system oscillations has been developed. To increase system damping an SVC uses a phase angle signal estimated from the measurement of voltage and power at the SVC location. By means of an optimization and identification procedure, optimized design of the damping control with various control concepts can be determined, taking into account nonlinear power systems. As a result of this method it is possible to increase power system damping considerably, in particular in critical situations close to the stability limit, using only locally measured state variables at the SVC, thus leading to an increase in the transmission capability of the power system     

Application of static VAr compensators to increase power systemdamping

A theory for analyzing power system damping enhancement by application of static VAr compensators (SVCs) has been developed using the equal area criterion. Some fundamental issues, such as the effect of SVCs on a power system, how to control an SVC to improve system damping, and the differences between continuous and discontinuous control of SVC reactive power to achieve the maximum damping improvement, are discussed. A discontinuous SVC reactive power output at discrete points is determined from the power deviation on a transmission line. Time-domain simulations of the application of this approach to a one-machine system to increase swing oscillation damping and to a four-machine system to increase the damping of an interarea oscillation mode demonstrate that the theory and method can be applied to solve practical power system damping problems     

Enhancement of power system dynamic performance through an on-line self-tuning adaptive SVC controller

Static VAr compensators (SVC) are used for voltage control of long distance bulk power transmission lines. By using a supplemental control loop an SVC can also be used to improve the dynamic and transient stability of a power system. Use of a self-tuning adaptive control algorithm as a supplementary controller for the SVC is presented in this article. The control derived is based on a pole-shifting technique employing a predicted plant model. Simulation studies on a simple power system model showed rapid convergence of the estimated plant parameters with an extremely good damping profile. The controller has been tested for ranges of operating conditions and for various disturbances. The effectiveness of the adaptive damping controller was also evaluated through an ‘optimized’ PI controller.     

Coordinated fuzzy logic control between SVC and PSS to enhance stability of power systems

This paper presents a new switching control scheme for static var compensator (SVC) using fuzzy logic control rules to enhance the overall stability of electric power systems. In addition, the coordination with power system stabilizers (PSS) is also considered to achieve a wider stable region. An SVC is set on one of the busbars in the transmission system, where the real power flow signal is utilized at the location of the SVC to determine the firing angle of the thyristor switch. The switching control scheme is simple so as not to require heavy computation on the microcomputer based switching controller. The PSSs are also set on the generators in the study system. Simulation results show the effectiveness of the proposed fuzzy logic switching control scheme for the SVC. The coordination between SVC and PSS is also effective to enlarge the stable region.     

SVC对电力系统频率稳定性影响的仿真分析

用Matlab软件建立电力系统仿真模型,负荷模型包括异步电动机模型和恒阻抗静态模型,静止无功补偿器(SVC)采用一阶线性化实用模型,对系统遭受双回线永久断一回线和系统负荷突然剧增这2种典型大干扰后SVC动作对系统频率造成的影响进行仿真和分析,包括SVC出力大小、动作时间及控制策略的影响。针对断一回线故障,当负荷端电动机比重较小时,SVC可使频率稳定在额定值。对系统在不同调频能力下负荷剧增时所做的频率变化仿真表明,SVC对系统的频率稳定性产生负面影响,SVC无功出力越大,则频率质量越差,当系统调频能力较弱而SVC无功出力很大时,会加速系统的频率崩溃。因此,在SVC的控制系统中应引入频率反馈,当监测频率低于某一定值时,应减少SVC出力至合理值。     

Improved fuzzy logic controller for SVC in power system damping using global signals

Static Var Compensator (SVC) is a shunt-type FACTS device, which is used in power systems primarily for the purpose of voltage and reactive power control. In this paper, an improved fuzzy logic-based supplementary controller for SVC is developed for damping the rotor angle oscillations and to improve the stability of the power system. The generator speed and the electrical power are chosen as global input signals for the proposed fuzzy logic controller (FLC). The effectiveness and feasibility of the proposed control is demonstrated with single-machine infinite bus (SMIB) system, three-machine nine-bus WSCC system and New England 10-machine system, which shows the improvement over the use of a fixed parameter controller and existing FLC.     

扩展二级电压控制系统的研究

从系统分析的角度阐述了扩展二级电压控制的基本原理，结合对某一实际系统的研究说明了在二级电压控制中，当仅依靠本区域内的控制发电机组进行电压控制不能取得理想效果时，可通过扩展二级电压控制系统的可控资源，综合考虑控制发电机组、有载调压变压器和自动投切并联电容器／电抗器的电压、无功调节功能，对其进行协调控制以获得良好的电压控制效果。对该实际系统进行了分析研究．设计了其扩展二级电压控制系统的方案与控制策略，并进行了仿真计算。计算结果表明，扩展二级电压控制较传统的二级电压控制能更好地协调本区域内各电压无功调节设备的无功出力和电压控制．使电压控制问题得到较好解决。     

基于瞬时无功功率理论和模糊控制的新型SVC控制算法

为满足不平衡三相配电网的无功功率实时补偿的要求,设计了一种新型的FC-TCR型静止无功补偿器(SVC)控制系统。该系统采用瞬时无功功率理论来精确检测基波正序和负序电压、电流,并推导出补偿导纳的表达式;SVC的整体控制采用了开环和闭环控制相结合的控制算法,并在闭环控制算法中,提出了基于智能规则的模糊-PI双模调节技术在无功补偿控制系统中的应用方案。该方案结合了模糊控制和PI控制2种方法的优点,根据系统状况改变PI控制器的参数,以达到更好的动态控制效果。仿真研究结果表明,该新型SVC控制系统对于提高功率因数和补偿三相不平衡,具有响应快、精度高的控制效果。     

Best location of SVC to improve first swing stability limit of a power system

While the primary purpose of a static var compensator (SVC) is to regulate bus voltage, it can also improve stability and damping of a power system if located appropriately. This paper proposes a method of determining the location index of a SVC in a multi-machine system to improve the first swing stability limit of the system. Based on the concept of transient energy function method, the location index of a SVC is considered to be the additional critical energy supported by the SVC and is computed through controlling unstable equilibrium point and potential energy boundary surface methods. In computing the critical energy, the SVC is represented by its susceptance at the verge of stability and which can be justified by carefully observing a recent control strategy of SVC used to improve the first swing stability limit of a power system. The effectiveness of the proposed location index of SVC is then tested on the 10-machine New England system and the 20-machine IEEE test system. Results obtained by the proposed method are then verified by comparing the critical clearing time obtained through time domain simulations of system dynamic equations.     

Reactive power control on residential utility-interactive PV power systems

This paper aims to optimize the reactive power absorbed by residential Photovoltaic (PV) power systems interactive with a utility feeder. Therefore, a proposed algorithm has been introduced here to assess the optimal size and location of static VAR compensator (SVC) at different operation conditions of residential PV systems. In this algorithm, a three-phase load flow analysis is used to calculate the size of SVC at different penetration levels and methods of operating PV systems, inverter power factors and load profiles to realize the substation power factor as well as PV penetration level is zero. Also, this size is optimized according to the locations to improve the voltage regulation and losses on the study feeder. The proposed algorithm is applied to develop the SVC size and location on an Egyptian utility feeder-interactive residential PV system at a constant value of power factor at the substation. Also, the effect of total reactive power on the feeder voltage and losses are deduced at different PV systems operation conditions.     

静止无功补偿器对电力系统性能改善的综述

随着电力电子技术、微处理技术和控制技术的发展,柔性交流输电系统FACTS(Flexible AC Transmission System)的出现,为电力系统急待解决问题提供了新的手段或策略。静止无功补偿器(SVC)作为FACTS家族的成员之一,对电力系统性能的改善也已取得了可喜的成绩。因此,从静止无功补偿器提高稳态输送容量、提高暂态稳定性、增强系统阻尼抑制低频振荡、缓解次同步谐振、预防电压不稳定或控制电压的波动、改善直流输电系统的性能等六个方面进行综述。     

An intelligent tutoring system for a power plant simulator

In this paper, an intelligent tutoring system (ITS) is proposed for a power plant simulator. With a well designed ITS, the need for an instructor is minimized and the operator may readily and efficiently take, in real-time, the control of simulator with appropriate messages he(she) gets from the tutoring system. Using SIMULINK and based on object oriented programming (OOP) and C programming language, a fossil-fuelled power plant simulator with an ITS is proposed. Promising results are demonstrated for a typical power plant.     

Synchronizing and damping torque coefficients and power systemsteady-state stability as affected by static VAr compensators

The utilization of static VAr compensators (SVC) for supplying reactive power at certain points of an electric power system is an efficient way for fast control of transient and steady-state voltage changes following short-circuits, load rejection, opening of severely loaded transmission circuits, etc. Other SVC applications include the increase of power transmission capacity through interconnections between areas of a power system and the damping enhancement of local or inter-area electromechanical oscillation modes. This paper fundamentally deals with these last two issues by analyzing the results of synchronizing and damping torque coefficient calculations for a generation station connected radially to a much larger power system. The results presented pertain to a double-circuit, 800 km, 500 kV transmission system during a one-circuit out contingency     

无功和谐波补偿装置的控制方法

针对具有功率因数补偿、补偿负载不平衡和滤除电网谐波电流等功能的联合运行系统,提出一种新的控制方法,由SVC模式控制和APF控制2部分组成.其中,SVC模式控制通过负序基波提取器实现电网负序基波分量的检测;通过改进的电压控制器实现公共连接点的电压稳定.利用特定次数谐波检测并进行相位补偿的方法实现电网谐波分量的检测;利用神...     

应用分岔理论分析SVC对电力系统电压稳定性的影响

基于分岔理论的电力系统电压稳定分析对于深入理解电压失稳机理有重要意义,特别是对于灵活交流输电系统,如静止无功补偿器等,分岔理论能够有效分析系统的动态控制特性对电压稳定的影响。利用非线性动力系统的分岔理论,使用通用分岔分析软件AUTO2000对典型的含SVC系统和不含SVC系统进行电压稳定的分析,得出了系统在两种情况下的分岔点数值。研究发现,通过添加静止无功补偿器(SVC),可以延迟系统的Hopf分岔点和鞍结分岔点,增加负荷极限,从而提高了系统电压稳定性。之后又通过双参数分岔分析确定了两维分岔边界。结果表明,在使用SVC控制器提高系统电压稳定性时,要详细考虑其参数对系统中各种分岔的影响,综合优化控制器的设计和安装。     

Application of power system stabilizers and static VAr compensatorson a longitudinal power system

The dynamic stability improvement of a longitudinal power system using a power system stabilizer (PSS) and a static VAr (reactive volt-ampere) compensator (SVC) is reported. An analytical approach is developed for the determination of PSS parameters. The effect of static VAr compensators installed at several different locations along 345 kV trunk lines on system responses is examined. Results from time-domain simulations indicate that the PSS and the SVC are very effective in damping system oscillations     

梧州SVC在电压控制下无功储备优化分析

研究了梧州SVC装置应用于电力系统中的电压支撑作用,保证当出现电压跌落时,SVC装置的控制策略使设备对500 kV电压起支撑作用。研究了梧州变电站加装SVC装置的实际应用的控制策略,通过设备控制保护系统RTDS仿真试验,测试SVC装置的实际V-I特性曲线与理论作比较,分析V-I曲线斜率对装置无功储备及对系统电压支撑的关系。研究结果表明,慢速导纳控制参数中调差率设定为0.02-0.03时,将大大提高装置正常运行方式下的无功储备,提升SVC装置抑制电压波动的性能。     

静止无功补偿器阻尼电力系统振荡（上）——理论分析

本文建立了装有静止无功补偿器（ＳＶＣ）的电力系统的推广Ｐｈｉｌｌｉｐｓ－Ｈｅｆｆｒｏｎ模型。在此基础上，从理论上分析了利用静止无功补偿器阻尼电力系统振荡研究中的基本问题，即：ＳＶＣ能够向电力系统提供正阻尼，提高电力系统静态稳定性的条件；电力系统参数，运行工况，ＳＶＣ电压控制及阻尼控制强度对ＳＶＣ向电力系统提供阻尼能力的影响；ＳＶＣ阻尼控制最佳安装地点的选择。文中首次提出了ＳＶＣ阻尼控制存在“失灵点”的概念，并分析了“失灵点”存在的原因。本文下篇中给出的研究实例，其特征值分析和非线性仿真的结果验证了文中给出的分析结论。     

Transmision capability enhancement using power electronics technologies for the future power system in Japan

Many power system stabilization measures realized by the upgrading transmission lines, generator controls, and power system controls and protections have been developed and utilized toward increasing transmission capability of power systems in Japan. With restriction of transmission routes and power system deregulation, it is now inevitable that transmission capability will be increased to sustain such power system reliability. Various remarkable power electronic technologies such as self-commutated SVC are being introduced toward improving power system stability. It is expected that these will also be employed in power flow control to avoid faults from cascading throughout the entire power system. This paper describes the present researches related to the application of power electronics to power systems in CRIEPI, including the recent results of the research carried out in cooperation with ten Electric Power Companies subsidized by MITI. Specifically: (1) analytical studies in power system enhancement by self-commutated SVC, thyrister controlled series capacitance (TCSC), and unified power flow controller (UPFC); (2) analytical studies on transmission capability increase of the interconnected power system applying the HVDC system with self-commutated converters; and (3) experimental studies of the self-commutated converter for continuous operation of converters at AC system faults.