A self-tuning automatic voltage regulator designed for anindustrial environment

Examination of the performance of fixed parameter controllers has resulted in the development of self-tuning strategies for excitation control of turbogenerator systems. In conjunction with the advanced control algorithms, sophisticated measurement techniques have previously been adopted on micromachine systems to provide generator terminal quantities. In power stations, however, a minimalist hardware arrangement would be selected leading to relatively simple measurement techniques. The performance of a range of self-tuning schemes is investigated on an industrial test-bed, employing a typical industrial hardware measurement system. Individual controllers are implemented on a standard digital automatic voltage regulator (AVR), as installed in power stations. This employs a VME platform, and the self-tuning algorithms are introduced by linking to a transputer network. The AVR includes all normal features, such as field forcing, VAr limiting and overflux protection. Self-tuning controller performance is compared with that of a fined gain digital AVR     

Experimental investigation and modelling of the interaction between an AVR and ballast load frequency controller in a stand-alone micro-hydroelectric system

 Extensive field experience in micro-hydroelectric systems in remote rural communities demonstrates that the use of a typical automatic voltage regulator (AVR), as supplied with a brushless self-exciting synchronous alternator, can be the cause of unsatisfactory system performance. This paper presents results from experiments undertaken on a full-scale micro-hydroelectric test rig as well as system modelling with PSCAD. The source of the instability is considered to stem from the similar time constants of the ballast load frequency controller and the AVR as two competing feedback control systems. System modelling is used to verify steady state operating points, and confirms that the under-frequency roll-off characteristic of the AVR also contributes to unsatisfactory performance.     

Implementation and test results of a generalized self-tuningexcitation controller

A self-tuning excitation controller performing the functions of AVR (automatic voltage regulation) and stabilization, and an interactive man-machine interface have been implemented using two microcomputers. The general setup of the hardware and software are described. Results of experimental tests on a physical model of a power system are also presented. The results demonstrate the effectiveness of the adaptive controller     

稳态调速率与静态调压率对柴油发电机组并联运行的影响

通过分析稳态调速率和静态调压率对柴油发电机组并联运行的影响,提出了利用机械液压调速器和普通AVR调压器调整稳态调速率和静态调压率的方法,实现了多台并联运行柴油发电机组均衡承载电网负载的要求。实际应用证明,该方法可靠且有效。     

An adaptive generator excitation controller based on linear optimalcontrol

An adaptive excitation controller for a synchronous generator based on the linear optimal control theory is proposed. The generator operating conditions are tracked by a model whose parameters are identified every sampling interval using the actual input and output of the generator. The control is computed by solving a third-order Riccati equation and the identified model parameters. Studies on a single-machine infinite-bus system and a three-machine infinite-bus system show that the proposed controller exhibits better performances than an automatic voltage regulator (AVR) with a conventional power system stabilizer (PSS)     

A 215 MVA Flywheel Motor-Generator with 4 GJ Discharge Energy for JT-60 Toroidal Field Coil Power Supply System

A 215 MVA flywheel motor-generator is used for the toroidal field coil power supply system of the energy breakeven plasma testing facility, JT-60, which started operations in April, 1985 at JAPAN ATOMIC ENERGY RESEARCH INSTITUTE. This paper describes an outline of the flywheel motor-generator and discusses the determination of the Xd' value which affects the voltage regulation characteristic of the motor-generator and the twenty-four pulse rectifier circuit, the compensation effect of AVR for the voltage regulation characteristic, the temperature rise and stress of the flywheel which is the largest one in the world and the torsional vibration caused by a thyristor starter, together with the results of field tests.     

Integrated fuzzy logic generator controller for stabilityenhancement

An integrated fuzzy logic controller is proposed in this paper for the generator excitation and speed governing control. The proposed controller has three control loops: the first one is the voltage control loop which has the function of automatic voltage regulator (AVR), the second one is the damping control loop which has the function of power system stabilizer (PSS), and the last one is the speed governing control loop which has the function of governor (GOV). A simple fuzzy logic control scheme is applied to all these three loops. The control scheme is simple enough so as not to require heavy computation for the controller, therefore, its real time application is feasible. The effectiveness is demonstrated through nonlinear simulations using a one machine infinite bus system. Comparison studies are also performed to show the advantages of the proposed controller with conventional excitation and speed governing control systems     

基于模糊决策的路灯节电等级控制系统的设计

此节能型路灯照明智能控制系统以单片机为核心,采用了电压、时间及光控制相结合的方法,利用模糊决策理论对节电等级进行控制,可有效改善路灯照明质量,节约电能及延长灯具的使用寿命,达到了很好的节电效果。     

A fuzzy logic excitation system for stability enhancement of powersystems with multi-mode oscillations

A fuzzy logic excitation system has been proposed to enhance the overall stability of power systems. The proposed excitation system has two control loops. One is the voltage control loop which achieves the automatic voltage regulator (AVR) function, and the other is the damping control loop which gives the PSS function. Simple fuzzy logic control rules are applied to both loops. The input signal to the voltage control loop is the terminal voltage, and the input signal to the damping control loop is the real power output. Simulation studies show the advantages of the fuzzy logic excitation system     

Finite-element time-step coupled Generator,Load, AVR, and brushless exciter modeling

This paper presents a model of a small brushless generating set that incorporates independently validated subsystem models. The new model links: a finite-element and time-stepping circuit model of the main alternator and load, a real-time model of the analog automatic voltage regulator (AVR) and a model based on the self and mutual inductances of the exciter machine along with the rectifier diode bridge. The composite model can be used to study the transient and steady-state performance of the whole generating set under different load conditions including synchronous operation in parallel with mains. The predicted transient behavior of an isolated generating set when subjected to various loads is presented, the implications with regard to induction motor starting are discussed, and voltage recovery and the function of each component are demonstrated.     

Neural network identification of power system transfer functions

This paper describes an investigation into the use of a multilayered neural network for measuring the transfer function of a power system for use in power system stabilizer (PSS) tuning and assessing PSS damping. The objectives are to quickly and accurately measure the transfer function relating the electric power output to the AVR PSS reference voltage input of a system with the plant operating under normal conditions. In addition, the excitation signal used in the identification procedure is such that it will not adversely affect the terminal voltage or the system frequency. This research emphasized the development of a neural network that is easily trained and robust to changing system conditions. Performance studies of the trained neural network are described. Simulation studies suggest the practical feasibility of the algorithm as a stand-alone identification package and as a portion of a self-tuning algorithm requiring identification in the strategy. The same technique applied to a forward modelling scheme can be used to test the damping contribution from different control strategies     

Digital AVR application to power plants

The digital AVR is not simply a digital version of the analog AVR, but can realize sophisticated control functions that were difficult to achieve with analog circuits, thus making it possible to enhance the stability of power system by PSS (power system stabilizers). This paper describes the test results of digital AVRs applied to power plants, their system configuration and functions, as well as the outline of an auto-tuning PSS (or AT-PSS) planned to be incorporated in digital AVRs in the future     

A continually online trained neurocontroller for excitation andturbine control of a turbogenerator

The increasing complexity of the modern power grid highlights the need for advanced modeling and control techniques for effective control of turbogenerators. This paper presents the design of a continually online trained (COT) artificial neural network (ANN) based controller for a turbogenerator connected to an infinite bus through a transmission line. Two COT ANNs are used for the implementation; one ANN, the neuroidentifier, to identify the complex nonlinear dynamics of the power system and the other ANN, the neurocontroller, to control the turbogenerator. The neurocontroller replaces the conventional automatic voltage regulator (AVR) and turbine governor. Simulation and practical implementation results are presented to show that COT neurocontrollers can control turbogenerators under steady state as well as transient conditions     

A particle swarm optimization approach for optimum design of PID controller in AVR system

In this paper, a novel design method for determining the optimal proportional-integral-derivative (PID) controller parameters of an AVR system using the particle swarm optimization (PSO) algorithm is presented. This paper demonstrated in detail how to employ the PSO method to search efficiently the optimal PID controller parameters of an AVR system. The proposed approach had superior features, including easy implementation, stable convergence characteristic, and good computational efficiency. Fast tuning of optimum PID controller parameters yields high-quality solution. In order to assist estimating the performance of the proposed PSO-PID controller, a new time-domain performance criterion function was also defined. Compared with the genetic algorithm (GA), the proposed method was indeed more efficient and robust in improving the step response of an AVR system.     

串联补偿式电力节电器的研制

设计一电力节电器,由双向交流BUCK斩波器与变压器串联组成。该串联型的电力变换器采用ATmega128来产生PWM开关信号和完成整个电路的电压闭环智能控制;新颖的PWM开关驱动方式使得此节电器可适用于任何负载,且节电效果明显。实验结果表明此节电器的节电率可达30%。     

The ENEL's experience on the evolution of excitation controlsystems through microprocessor technology

Over recent years, the evolution of microprocessor technology with the consequent availability of reliable, high performance, low cost digital hardware and powerful software tools and the prospect of growing difficulties in the maintenance of analog apparatus, has led many manufacturers to develop new digital AVRs. Many benefits are expected from the use of microprocessors as wider flexibility, improvements in control performance and autodiagnostics, richer information for the local and remote operator. To exploit these advantages ENEL, the Italian Electricity Company, encouraged the Italian electromechanical manufacturers to develop a new generation of digital AVR. The paper, after a brief glance over the general problems and advantages deriving from the use of microprocessor technology, gives an overview of the most technical aspects to be envisaged in the design of digital AVR and shows the differences in the approach and the novelties coming out with respect to the traditional analogue solution. It deepens design aspects regarding the hardware and software architecture, the reliability and the safety, factors affecting interface, response the criteria for evaluating dynamic alteration. An example of the advanced digital AVR is presented in detail     

Nuclear energy as a primary energy source for hydrogen production

New forms of energy are required to solve the future problems of the world energy market, especially as regards the substitution of mineral oil. High-temperature reactors can make an important contribution towards this goal. The prerequisite is a temperature availability of approx. 950°C, which has been demonstrated in the AVR reactor at Jülich for 3 years. The 300-MW THTR is being constructed as a continuation of the German HTR programme. At present some processes for coal modification are being promoted by the Development Programme of the Federal Republic of Germany (FRG). The most ideal application of the high-temperature reactor could be the production of hydrogen from water with the aid of thermochemical methods and hybrid processes.     

A novel line drop secondary voltage control algorithm for variable speed wind turbines

This paper addresses the design and implementation of the line drop secondary voltage control (LDSVC) for the doubly fed induction generator‐wind turbine (DFIG‐WT) complemented with reactive power allocation algorithm to achieve more efficient voltage regulation, reactive power compensation and to enhance the transient stability margin of the electric power system. The LDSVC is used to generate the local voltage reference, providing an improvement for overall voltage profile. The paper presents the influence of the integration of variable speed wind turbines‐based doubly fed induction generator (DFIG) while employing LDSVC for increasing the transient stability margin. This paper proposes an improved voltage control scheme, based on a secondary voltage controller complemented with an automatic gain controller (AGC). The scheme is applied to a wind energy system incorporating DFIG‐based wind turbines. The controller structure is developed and the performance of the self‐tuning AGC scheme is developed and analysed. The proposed controller is tested in response to system contingencies for different short circuit ratios. The performance of the secondary voltage control without and with AGC is verified. The influence of the AGC in improving the transient response and damping of voltage oscillations is verified. Copyright © 2010 John Wiley & Sons, Ltd.     

Autonomous micro hydro power plant with induction generator

Autonomous micro hydro power plants (MHPP) are a reliable solution for supplying small power consumers in areas located far from the distribution grid. When an induction generator (IG) is used in such a power plant, voltage and frequency need to be stabilized. This paper presents a single control structure that ensures both the voltage and frequency regulation of an isolated induction generator (IG). The control structure consists in a voltage source inverter (VSI) with a dump load (DL) circuit on its DC side. The VSI operates at constant frequency, thus stabilizing the IG frequency also. For voltage regulation two cascaded regulators are used, which have as reference the line voltage and the VSI DC voltage, respectively. Simulations and experiments are carried out in order to investigate the reliability of such configuration when supplying static and dynamic loads.     

Performance of a three-phase AC generator with inset NdFeB permanent-magnet rotor

This paper presents the analysis and performance of a three-phase AC generator with an inset, neodymium-iron-boron (NdFeB) permanent-magnet (PM) rotor. Such a rotor construction gives rise to an inverse saliency effect (i.e., the direct-axis synchronous reactance is less than the quadrature-axis synchronous reactance). This feature results in an improvement in the voltage regulation characteristics when the generator supplies an isolated, unity-power-factor load. By solving the equations derived from the two-axis theory, it is found that there exists, in general, two values of load current at which zero voltage regulation is obtained. The relationship between armature resistance, inverse saliency ratio, and the operating speed to give zero voltage regulation is investigated. The finite-element method (FEM) is used for computing the pertinent generator parameters for performance evaluation, namely the no-load voltage and the synchronous reactances. Flux plots are presented to confirm the origin of inverse saliency in the inset PM rotor. The theoretical analysis is validated by experiments carried out on a 2.5-kVA prototype generator.