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     

Load and voltage balancing in harmonic power flows by means of static VAr compensators

In special applications, static VAr compensators (SVCs) with thyristor-controlled reactors (TCRs) are used to balance unbalanced loads or to eliminate voltage unbalances at the terminals of the SVC. In both cases, load balancing and voltage balancing, the TCR can present a significant unbalanced behavior which produces important quantities of noncharacteristic harmonics. In this paper, the formulation and solution of the load and voltage balancing problems are developed for harmonic power flows obtained from a combination of two blocks: (1) a conventional load flow (CLF) and (2) an iterative harmonic analysis (IHA). In both blocks, the treatment of load and voltage balancing is described in detail. Load flow (LF) calculations and harmonic analysis show the presence of noncharacteristic harmonics in these two situations.     

Robust design of a damping controller for static VAr compensatorsin power systems

This paper presents a systematic procedure for the synthesis of a supplementary damping controller (SDC) for static VAr compensators (SVC) in multimachine power systems. The robust performance in terms of the structured singular value (SSV or μ) is used as the measure of control performance. A wide range of operating conditions are used for testing. Simulation results on standard test systems show that the resulting SDC effectively enhances the damping of the interarea oscillations, providing robust stability and good performance characteristics both in frequency domain and in time domain     

Voltage control stability and dynamic interaction phenomena ofstatic VAr compensators

This paper describes the results of a comprehensive investigation on: (1) small-signal dynamic interactions of voltage control loops of multiple static VAR compensators (SVCs); (2) the phenomena of SVC-network interactions; and (3) torsional interactions with SVCs. This paper is concerned with small-signal dynamics in the high frequency (HF) range, i.e. above 4 Hz. The studies are conducted on various power system configurations, based on the use of a newly developed eigen analysis software tool. The eigen analysis tool provides a systematic approach to include the dynamic mathematical model of the transmission network in the overall system model, which is necessary for HF dynamic studies. The investigations identify undesirable small-signal oscillations associated with SVC-SVC and/or SVC-network interactions, and provide fundamental information for design/coordination of SVCs     

Development of a large static VAr generator using self-commutatedinverters for improving power system stability

A static VAr generator (SVG) using self-commutated inverters of 80 MVA capacity was developed and successfully applied to an annual 154 KV power system to stabilize the power system. The SVG consists of 48 pulse multiple inverters whereby gate turn-off (GTO) thyristors are applied. After installing it at a power system site, a field test was conducted to confirm the system stabilizing effect. The test results displayed the expected performance, and the SVG was proven to be effective power system stabilizer. The outline of the 80 MVA SVG, technical features, and the test results are described     

Application of static VAr compensators for the dynamic performanceof the Mead-Adelanto and Mead-Phoenix transmission projects

This paper presents the planning and pre-specification study analysis and results for the joint use of static VAr compensators (SVC), a form of flexible alternating current transmission system (FACTS) technology, for the Mead-Adelanto and Mead-Phoenix projects in the Southwestern USA. Because of insufficient system damping in the network, addition of these two transmission line projects must also be complemented by SVC. These devices increase the system stability limit so that the projects' planned transfer capabilities can be economically attained. These are the first transmission projects in the region where a very closely coordinated planning effort permits the joint use of SVC to provide mutual benefits to both projects. SVC dynamic performance enhancement studies, SVC control analysis, and studies related to the planning and specification requirements are among the topics addressed in the paper     

An optimal location of static VAr compensator based on Gramian critical energy for damping oscillations in power systems

The increase in the scale and complexity of interconnected power systems leads to multiple electromechanical oscillations. Therefore, the electric network needs to be made more stable. One type of Flexible alternating current transmission systems (FACTS) devices, namely the static VAr compensator (SVC), can be installed at buses to increase the stability margins and dampen the power system oscillations by exchanging capacitive and/or inductive load to maintain and/or control specific parameters of electrical power systems. The efficiency and performance of the SVC depend on its optimal location. Consequently, seeking the optimal placement for SVC has become a key issue. In this paper, we propose a novel method to find the optimal location for the SVC based on a two‐step approach. First, an energetic approach based on the combination of the controllability Gramian critical energy analysis with the balanced realization reduction technique is used to search for several feasible locations; then the transient stability is analyzed to compare and determine an optimal location through various test cases. The effectiveness of the proposed method has been demonstrated on the IEEE 39‐bus England power system and compared with the modal controllability index. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A neural network-based approach for on-line dynamic stability assessment using synchronizing and damping torque coefficients

This paper presents an artificial neural network (ANN)-based on-line approach to evaluate the dynamic stability of a single machine infinite bus system. The proposed on-line assessment scheme is based on estimating the synchronizing and damping torque coefficients as dynamic performance indices. The two performance indices are estimated from on-line measurements of the changes in the rotor angle, speed and electromagnetic torque using a three-layer feedforward neural network with back propagation. The results show that the proposed method is very promising and encouraging for fast real-time evaluation of the dynamic performance of power systems.     

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     

静止同步补偿器与传统静止无功补偿器的比较与分析

随着灵活交流输变电(FACTS)技术的不断发展,出现了很多新型的FACTS装置。比如基于全控型电力电子器件(如GTO晶闸管与IGBT等)的STATCOM就是其中之一,它与传统的补偿器SVC相比在技术上有着很多的优势。介绍FACTS装置中的STATCOM与SVC,并对它们在电压支撑、动态仿真、控制方法、谐波和经济性等方面进行综合分析与比较。     

应用SVC提高风电场接入电网的电压稳定性

风电具有随机性和间歇性,较大规模风电场的接入会对电力系统稳定性产生较大影响。研究静止无功补偿器(SVC)在风电并网过程中的应用,以某地区多个风电场接入本地电网为背景,分析在重要负荷点安装SVC的效果。仿真结果表明,SVC能改善不同风电场出力情况下系统电压质量,提高风电送出能力和电网暂态电压稳定性。     

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     

Estimating the synchronizing and damping torque coefficients using Kalman filtering

This paper presents an optimal approach for optimal estimation of the synchronizing and damping torque coefficients of a synchronous machine using two-state linear Kalman filter. These coefficients can be used as indices which provide insight into the dynamic stability of power systems. The two coefficients are calculated using the time responses of the changes in the rotor angle, rotor speed, and electromagnetic torque. The effect of system noise on the performance of the Kalman filter is also investigated. The performance of Kalman filter is compared with the least-square error technique. The paper shows that the steady-state response of Kalman filter agrees with the least-square solution. The paper shows that Kalman filter can be used as efficient tool for either on-line or off-line estimation of the synchronizing and damping torque coefficients.     

Power system transient stability enhancement by optimal control of static VAR compensators

A study of power system transient stability enhancement through the effective use of static VAR compensators is presented. The optimal control strategy resulting from the direct Lyapunov method and Pontryagin's maximum principle requires a control signal based on the state variables not available at the compensator bus. It is proved that this optimal signal can be replaced by the time derivative of an electric quantity derived from local measurements. A control algorithm based on this quantity gives smooth and very effective regulation. Tests done for two-machine and multi-machine systems have confirmed the validity and robustness of the proposed control algorithm.     

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.     

Multi-band power oscillation damping controller for power system supported by static VAR compensator

Electrical Engineering - Low-frequency electromechanical oscillations damping is powerfully crucial in power system operation. In order to fulfill this requirement, power oscillation damping (POD)...     

Calculation of damping torque of power systems compensated with TCSC

The thyristor‐controlled series capacitor (TCSC) is being developed to improve the transmission capability of power systems. The TCSC is thought to compensate transmission line reactance without causing subsynchronous resonance (SSR). However, in order to evaluate its effect quantitatively, we must calculate the frequency response of the generator damping torque. Simulations need a long computing time, and it is hard to choose the frequency freely. In this paper, we propose a method of analytically calculating the damping torque. First, when a generator rotor oscillates at some frequency, two voltage components appear. We analytically calculate the damping torque from small current variations due to the voltage components. The damping characteristic changes depending on the method of firing thyristors. The best characteristic is obtained when triggering with reference to the fundamental wave of TCSC voltage or current is used. By choosing an appropriate firing angle, we can drastically reduce negative damping by the TCSC. The damping characteristic is closely related to the system impedance. The fact that the TCSC has large resistance in the 0 to 60 Hz range helps significantly in improving the characteristic. Lastly, numerical simulations of SSR are used to examine the validity of our investigation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 39–49, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10068     

无功补偿(SVC)装置的性能及应用

分析无功功率补偿领域广泛使用的3种静止型无功功率补偿-SVC装置的原理及性能特点,分析了几种典型的大功率负荷的无功功率变化特点,有针对性地总结了适合它们的SVC装置.