Adaptive control of a synchronous machine using the auto-searchingmethod

A novel adaptive control scheme is presented for the design of a power system stabilizer (PSS) and a static VAr (reactive volt-ampere) compensator (SVC). The developed adaptive proportional-integral (PI) controllers, whose gains are adjusted in real time using the online-measured system operating conditions and a look-up table stored in computer memory, can offer better damper effects for generator oscillations over a wide range of operating conditions than conventional PI controllers with fixed gain settings. The effects of the adaptive PSS and the adaptive SVC on generator damping and terminal voltage profile are examined by computer simulation of system dynamic responses to a major disturbance     

Robust SVC controller design for improving power system damping

The design of a robust controller for a static VAr compensator (SVC) to improve the damping of a power system is presented. The main contributions of the paper are to formulate and to solve the power system damping control problem using robust optimization techniques, and to synthesize the controller with explicit consideration of the system operating condition variations. Nonlinear simulations using the PSCAD/EMTDC software packages have been conducted to evaluate the performance of the closed-loop system. The results have indicated that the designed controller can provide positive damping to the system under a wide range of operating conditions     

Performance testing of a long distance radial static VArcompensated transmission system and validation of simulationresults

The authors present selected results of recent field tests carried out on the 220 kV, 660 km radial static VAr (volt-ampere reactive) compensated Muja-Kalgoorlie transmission system in Western Australia. Measured results on network harmonics, SVC (static VAr compensator) losses and the responses of the power system under small and large-disturbance conditions are discussed. The recorded data have also been used to validate and improve the computer models used in simulation studies     

Coordinated design of PSSs and SVC via bacteria foraging optimization algorithm in a multimachine power system

This paper develops a novel algorithm for simultaneous coordinated designing of power system stabilizers (PSSs) and static var compensator (SVC) in a multimachine power system. The coordinated design problem of PSS and SVC over a wide range of loading conditions is formulated as an optimization problem. The Bacterial Foraging Optimization Algorithm (BFOA) is employed to search for optimal controllers parameters. By minimizing the proposed objective function, in which the speed deviations between generators are involved; stability performance of the system is improved. To compare the capability of PSS and SVC, both are designed independently, and then in a coordinated manner. Simultaneous tuning of the bacterial foraging based coordinated controller gives robust damping performance over wide range of operating conditions and large disturbance in compare to optimized PSS controller based on BFOA (BFPSS) and optimized SVC controller based on BFOA (BFSVC). Moreover, a statistical T test is performed to ensure the effectiveness of coordinated controller versus uncoordinated one.     

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     

Coordinated design of probabilistic PSS and SVC damping controllers

This paper presents an application of probabilistic theory to the coordinated design of power system stabilizers (PSSs) and FACTS controllers, taking static VAr system (SVC) as an example. The aim is to enhance the damping of multi electro-mechanical modes in a multimachine system over a large and pre-specified set of operating conditions. In this work, conventional eigenvalue analysis is extended to the probabilistic environment in which the statistical nature of eigenvalues corresponding to different operating conditions is described by their expectations and variances. Probabilistic sensitivity indices (PSIs) are used for robust damping controller site selection and for optimization objective functions. A probabilistic eigenvalue-based objective function is employed for coordinated design of PSS and SVC controller parameters. The effectiveness of the proposed controllers is demonstrated on an 8-machine system.     

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.     

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     

Using a static VAr compensator to balance a distribution system

An algorithm for applying a fixed capacitor-thyristor-controlled reactor (FC-TCR) type of static VAr compensator (SVC) in a distribution system to dynamically balance such a system is introduced. With a newly developed individual phase control scheme, an SVC can reduce negative-sequence current caused by the load to improve power system balance. The control circuit is governed by a microcomputer, which replaces the traditional discrete load switching and makes the capability of rapid and dynamic balancing of the system possible. In addition, the power factor can be improved simultaneously by selecting an appropriate amount of capacitive/inductive compensation. This paper presents a mathematical model for computer simulation and control of a delta-connected SVC to achieve the purpose of negative-sequence reduction. Some computer simulation and scaled laboratory test results are discussed     

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.     

电站系统中PSS与SVC联合运行的稳定分析

针对电力系统装置相互协调运行问题,对配有PSS的励磁发电机与SVC联合运行的系统,分析了其数学模型,研究了电力系统稳定器(PSS)与静止无功补偿器(SVC)在工厂用电系统近距离联合运行中的交互影响问题,指出了在两者同时运行的情况下SVC控制器的设计需要考虑PSS放大倍数的影响。并提出了设计SVC的比例积分系数和PSS超前滞后环节以及线性二次高斯最优控制方法,动态特性仿真表明可以提高工厂用电系统SVC和PSS的稳定性。最后通过对系统仿真计算从而对理论方法进行了验证。     

发电厂厂用电系统中PSS与SVC稳定的离散分析

针对电力系统装置间相互协调运行的问题,对配有电力系统稳定器(PSS)的励磁系统发电机与装有静止无功补偿器(SVC)联合运行的发电厂厂用电系统,分别建立了PSS、SVC和带励磁系统的发电机数学模型并将其离散化,深入研究了PSS与SVC在厂用电系统近距离联合运行中的交互影响问题及提高SVC和PSS运行稳定性的方法。指出了在两者同时运行的情况下SVC控制器的设计需要考虑PSS放大倍数的影响,对SVC的比例、积分系数的改进设计的动态特性仿真表明,可以提高厂用电系统中SVC和PSS联合运行的稳定性。通过大量的仿真实验对离散分析的结果进行了验证。     

Detailed modeling of an actual static VAr compensator forelectromagnetic transient studies

The authors present a detailed model of a static VAr compensator (SVC) for digital simulation of electromagnetic transients. It is also demonstrated that this model can adequately reproduce SVC transient behavior as verified in transient network analyzer studies carried out with a replica of the SVC control system. The SVC control system is described, with emphasis on some special blocking schemes needed to meet particular requirements of the power system transient performance. The complete system and SVC data are also included     

电力系统大扰动下振荡抑制及暂态稳定性分析

采用电力系统稳定器和静止无功补偿器可以有效地抑制系统振荡。分析了电力系统稳定器和静止无功补偿器的数学模型,采用Prony算法找出主导振荡模式,并进行系统建模仿真,研究了两者在电力系统中的协调运行问题。仿真结果表明该方法对提高电力系统暂态稳定性具有良好的效果。     

Thyristor controlled series compensation application study-controlinteraction considerations

A study of the potential for control interaction between a proposed thyristor controlled series compensation (TCSC) and an existing static VAr compensator (SVC) is presented. The results indicate that a control interaction exists between the voltage-input power swing damping control (PSDC) of the TCSC, the series compensated AC system resonances, and the SVC controls. The addition of recommended filtering and synthesized angle-input PSDC showed improved performance     

Updating stochastic model coefficients for prediction of arc furnace reactive power

The time varying nature of electric arc furnace (EAF) gives rise to voltage fluctuations which produce the effect known as flicker. The ability of static VAr compensator (SVC) in flicker reduction is limited by delays in thyristor ignition. To improve SVC performance in flicker compensation, EAF reactive power can be predicted for a half-cycle ahead, by using appropriate autoregressive moving average (ARMA) models. This paper uses huge field data collected from ac arc furnaces, and demonstrates that the EAF reactive power models coefficients are different from one data record to another and do not follow any specific law. Therefore, it is necessary to update the model coefficients for prediction purposes. For this purpose, two major adaptation algorithms, the least mean square (LMS) and recursive least square (RLS) are used to determine online the prediction relationship coefficients. By applying the methods to the data records and using some indices such as newly defined indices based on concepts of flicker frequencies and power spectral density, the transient and steady state performances of the methods are studied in EAF reactive power prediction. A simulation example on the application of the predictive models in a SVC control system is presented.     

Damping controller design for power system oscillations usingglobal signals

This paper describes a new power system stabilizer (PSS) design for damping power system oscillations focusing on interarea modes. The input to the PSS consists of two signals. The first signal is mainly to damp the local mode in the area where PSS is located using the generator rotor speed as an input signal. The second is an additional global signal for damping interarea modes. Two global signals are suggested; the tie-line active power and speed difference signals. The choice of PSS location, input signals and tuning is based on modal analysis and frequency response information. These two signals can also be used to enhance damping of interarea modes using SVC located in the middle of the transmission circuit connecting the two oscillating groups. The effectiveness and robustness of the new design are tested on a 19-generator system having characteristics and structure similar to the Western North American grid     

Power oscillation damping using controlled reactive powercompensation-a comparison between series and shunt approaches

How controlled reactive power compensation can be used to damp power system oscillations is described. This is of particular interest in the case of weakly coupled networks. A comparison is made between two kinds of controllable reactive power elements, namely, the CSC (controlled series capacitor) and the SVC (static VAr compensator). Efficiency in terms of damping effect per installed MVAR and the dependence of equipment location are considered. The influence of connected loads is investigated to some extent. Basic relationships for the CSC and the SVC approaches are shown     

基于MATLAB的电力系统机电暂态仿真研究

本文对一个含两台水轮发电机组的输电系统进行暂态稳定性研究仿真演示。为提高系统的暂态稳定性和阻尼振荡能力,该系统中配置了静止无功补偿器(SVC)以及电力系统稳定器(PSS)。介绍了电力系统稳定器(PSS)和静止无功补偿器(SVC)的基本功能,利用MATLAB仿真软件的Simulation工具箱对一个双机系统进行了建模和仿真,将系统的工作过程及有关波形准确直观地显示出来。