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.     

TSC型静止无功补偿器提高系统阻尼特性的研究

长距离大功率输电系统，在暂态时阻尼特性较差是其稳定性的主要特点。本文从理论上论证了静止无功补偿器（ＳＶＣ）能够提高系统阻尼特性的原理，证明了ＳＶＣ采用频率作为控制信号时具有最佳的阻尼效果，给出了ＳＶＣ模型。实际５００ｋＶ长距离输电系统仿真计算所得的结果验证了ＳＶＣ提高系统阻尼特性的效果。     

输变电工程项目的模糊多目标综合评判决策

将模糊多目标评判决策引入输变电工程的建设决策,将规划专家的经验知识结合模糊多目标评判决策理论提出一种应用于电网规划辅助决策系统的输变工程评判决策的实用方法。     

基于奇异值分解方法的FACTS交互影响分析

针对电力系统中多台灵活交流输电装置(FACTS)控制器之间可能存在的交互影响问题,以可控串联补偿器(TCSC)和静止无功补偿器(SVC)2种FACTS控制器为研究对象,提出了一种基于奇异值分解(SVD)的交互影响分析方法,定量分析了新英格兰10机39节点电力系统中同时装设TCSC和SVC时,2台FACTS装置之间可能存在的交互影响问题及电气参数对交互作用的影响。时域仿真结果验证了所提出的方法的有效性,表明电气距离的改变对TCSC与SVC间的交互作用有着较强的影响,增加电气距离,交互影响变弱,缩短电气距离则会加重两者之间的交互影响。     

换相失败下直流送端SVC无功反调机理分析及控制策略研究

直流送端系统配置的动态无功补偿设备存在无功反调特性,换相失败情况下该特性会助增直流送端的交流系统出现暂态过电压。文中首先对直流送端系统暂态电压进行频谱分析,得到其谐波主导频率,并对SVC控制系统进行相频特性分析,揭示了SVC发生无功反调的内在机理,即SVC滞后特性是其在换相失败时发生无功反调的根本原因。在此基础上提出了SVC电容器投切控制策略。通过在电压恢复阶段切除部分电容器,有效抑制了SVC无功反调现象,仿真验证了SVC控制策略的有效性。     

静止无功补偿器控制对电压稳定的影响研究

论述了SVC（静止无功补偿器）可以提高电力系统的稳定性,但是SVC控制器给系统的状态矩阵引入了新的状态变量,改变了系统的相关特性,可能会在消除或延迟原有分岔的基础上削弱某些运行模式的阻尼,乃至改变系统分岔点的类型。以IEEE14节点系统的时域仿真结果为例表明,随着SVC安装点数目增多,在系统稳定性有所提高的同崃,系统中发生低频振荡的几率增大。提出在实际中使用SvC提高系统电压稳定性时,需要考虑多台SVC控制器动态特性对系统稳定性的不利影响,合理规划安装地点。     

特高压直流输电工程可行性研究主要技术原则

特高压直流输电工程输送容量巨大、输电距离遥远、电压等级进入特高压范畴,对电网规划建设和安全稳定运行影响深远,对工程建设条件要求更高。根据特高压直流输电工程不同于常规直流输电工程的特点,总结归纳世界上第1批特高压直流输电工程可行性研究工作,就可行性研究阶段输电方案拟定、换流站站址及接地极极址选择、线路路径选择以及系统方案比较等主要技术原则,分析特高压直流输电工程可行性研究中应注意把握的主要技术内容。     

输电系统SVC电压调节器增益自适应控制方法

静止无功补偿装置(State Var Compensator, SVC)电压调节器的增益影响其响应速度和稳定性。在详细调研国内外输电系统SVC应用背景和技术路线基础上,重点研究了输电系统复杂变化对SVC电压调节器的影响,分析和总结了适用于输电系统SVC电压调节器增益控制方法,提出一种基于闭环积分控制的增益自适应控制方法。增益自适应控制能够在系统运行方式变化或电压调节器输出持续振荡时对电压调节器的增益进行适当调整。通过RTDS仿真试验验证了该方法的有效性。该方法具有便于实现、快速抑制振荡、优化增益改善动态响应特性及适用范围广等优越性。     

发电机励磁及SVC非线性最优协调控制

发电机励磁和静止无功补偿器(static var compensator,SVC)对远距离输电的稳定性有很大影响。为了提高系统在大扰动情况下的暂态稳定性,提出一种发电机励磁系统与SVC协调非线性最优控制方法。通过建立发电机励磁与SVC系统的综合模型,将微分几何反馈线性化理论与线性最优控制理论相结合,设计了发电机励磁与SVC系统的非线性最优协调控制规律。控制信号实现了本地化,避免了远距离的信号传输。仿真结果证明,该控制方法能同时改善系统的功角稳定性和电压稳定性。     

静止无功补偿器对提高阳城送电稳定水平的研究

利用ＢＰＡ软件重点针对最城～淮阴长距离输电线研究静止无功补偿器（ＳＶＣ）对系统故障后暂态和动态稳定的影响。并对ＳＶＣ的不同安装地点进行分析比较。数字仿真的结果表明：静止无功补偿器能提高系统稳定性和动态性能。     

SVC安装地点对次同步振荡抑制效果的影响

静止无功补偿器（Static Var Compensator,SVC）可用于抑制次同步振荡,根据SVC抑制次同步振荡的机理设计了SVC的次同步阻尼控制器（SSI）C）,基于次同步振荡研究的IEEE第一标准模型,分别研究了将SVC并联安装在发电机机端母线上、升压变压器的二次侧母线上、输电线路中点上和输电线路末端时的电气阻尼频率特性和时域仿真分析;提出了SVC不同的安装地点会对次同步振荡的抑制效果产生一定的影响,甚至会诱发次同步振荡。     

500kV直流融冰兼动态无功补偿装置的晶闸管阀试验

介绍了500kV直流融冰兼动态无功补偿装置的晶闸管阀子系统调试及试验情况,从试验的一般原则出发并结合现场试验经验,详述了调试方法,给出试验结果。文中总结的现场试验注意事项和经验可为相关工程技术人员提供参考。     

应用静止无功补偿器抑制次同步谐振的仿真研究

针对华北地区某大型坑口电厂（A电厂）串联补偿送出系统次同步谐振（subsynchronousresonance,SSR）引发发电机组轴系扭振的问题,采用基于电力系统计算机辅助设计和电磁暂态模拟程序软件（powersystemcom-puteraideddesignandelectricmagnetictransientinDCsystem,PSCAD／EMTDC）的时域仿真与频域仿真分析相结合的方法,通过大量的仿真计算,对静止无功补偿器（staticvarcompensator,SvC）抑制SSR的工作原理、控制策略及其影响因素等进行了系统的研究和验证。仿真结果与实际工程应用结果均表明,SVC能有效抑制SsR的发生。该方法可解决南方电网系统内交流串联补偿输电工程中的SSR问题。     

Developing static reactive power compensators in a power systemsimulator for power education

This paper describes a newly installed laboratory module microcomputer-based static reactive power compensator (SVC) in detail to teach students how an SVC affects system voltage, load balancing, power factor, and transmission line losses. The SVC is merged into an old power system simulator for extensive power engineering education. The structure of the SVC is thyristor controlled reactors with fixed capacitors (TCR-FC). Two control algorithms, feedback control and feedforward control, are developed and compared. For the purpose of program flexibility and portability, a VME-Bus based microcomputer is used to synthesize the controller of the SVC. Several suggested experiments are given to show the effects of the SVC on distribution system compensation. The SVC greatly promotes the performance of the power system simulator     

DIRECT EVALUATION OF TRANSIENT STABILITY IMPROVEMENT WITH STATIC VAR COMPENSATORS USING A STRUCTURE PRESERVING ENERGY FUNCTION

Abstract

The ability of Static Vax Compensators (SVCs) to rapidly and continuously control reactive power in response to changing system conditions can result in the improvement of system stability and also increase the power transfer in the transmission system. This paper concerns the application of strategically located SVCs to enhance the transient stability limits and the direct evaluation of the effect of these SVCs on transient stability using a Structure Preserving Energy Function (SPEF). The SVC control system can be modelled from the steady- state control characteristic to accurately simulate its effect on transient stability. Treating the SVC as a voltage-dependent reactive power load leads to the derivation of a path-independent SPEF for the SVC. Case studies on a 10-machine test system using multiple SVCs illustrate the effects of SVCs on transient stability and its accurate prediction.     

Mismatched disturbance attenuation control for static var compensator with uncertain parameters

The use of a static var compensator (SVC) as a component of flexible alternating current transmission system (FACTS) devices to control power systems has been investigated for decades. Its aim is to regulate the system voltage and improve the stability and loadability of power systems. A typical assumption in such a system is that the parameters of the controlled system are known accurately, which is rarely satisfied in practice. This paper explores the development of a simple but effective controller for a single-machine infinite-bus power system with SVC subjected to both matched and mismatched disturbances where the controller derivation is based on the assumption that all parameters used in the system modeling are unknown, but bounded in size. The research in this paper illustrates how an indirect robust control can be incorporated with a modified disturbance observer-based feedforward term to attenuate the influence of parameter variations and disturbances from the outputs of the system. Simulation results are presented to confirm the effectiveness of the proposed scheme.     

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.     

Impact of SVC on the protection of transmission lines

The impact of Static Var Compensator (SVC) on the apparent impedance seen by the transmission line distance relay is investigated in this paper. Analytical results are presented and verified by detailed simulations. It is shown that the connection type of the windings of the shunt coupling transformer of the SVC has a remarkable effect on the apparent impedance seen by the distance relay. Six different phase to phase and phase to ground measuring units of the distance relay are simulated to resemble the behavior of the relay. The impact of SVC is more pronounced on the apparent impedance seen by the phase to ground fault measuring units than the others as is shown by the results. Simulation results include different power system operating conditions, SVC control system settings and different fault-type scenarios. The impact of SVC on the relay tripping boundaries is also clearly demonstrated. Detailed and sophisticated models are used for simulating distance protective relay in a digital simulation environment.     

Selection of the best siting of static var compensators for effective damping

A static Var compensator (SVC) can improve the steady-state stability (or the small signal stability), if it is located appropriately. The present paper proposes a method for selecting the best siting of SVC in large-scale power systems for damping effectively. Conventionally, it is thought that SVC improves steady-state stability by its voltage regulating ability. From this point of view, the stability can be improved significantly if SVC is located at the bus which has a large voltage fluctuation due to the lightly damped power swing mode. In contrast to the conventional viewpoint, the present paper makes it clear that the steady-state stability deteriorates by the conventional voltage regulating control of SVC in some cases. Therefore, the voltage fluctuation is not an appropriate index for effective damping. This paper explains the mechanism of improvement of steady-state stability by SVC in terms of modal analysis. On the basis of modal analysis, an index for determining the location of SVC is derived. The index is called LIED (Location Index for Effective Damping) by the authors. Digital simulations are conducted for an 8-machine longitudinal system and a 29-machine looped system to demonstrate the validity of the proposed index.     

Static VAr compensator protection

Static VAr compensator (SVC) protection practices are presented. Protection schemes comprise a combination of conventional protective relays as well as protection functions performed by the control system. This paper describes different protection functions applicable to SVCs and includes a tabulated overview of possible SVC protection methods. A section is dedicated to testing SVC protection systems. The outlined test procedures may be adopted when commissioning new installations in order to demonstrate proper protection operation. Finally, an important aspect of SVC protective schemes is related to the interactions with transient overvoltages, harmonics, short-circuits, and geomagnetic induced current (GICs) of the transmission network. This paper discusses these issues and identifies areas where careful protection considerations are required