Excitation Control Of Synchronous Generator Research Articles

Implementation of Model-Based Fault Detection Schemes on Lab-Scale Power Systems

This paper deals mainly with the real-time implementation of a model-based Fault Detection and Isolation (FDI) scheme on a laboratory scale electric power system to detect various faults in the synchronous generator excitation control loop. The following types of faults have been considered: sensor faults, actuator faults, and load faults in the synchronous machines. The implementation of FDI has been carried out on a TMS320-C30 based real-time multi-channel processor. Satisfactory results have been obtained and reported in this paper. Furthermore, the paper has concluded that for the purpose of fault detection, a simplified synchronous machine model is sufficient. However, in order to isolate the fault, or to obtain the detailed information about the fault, or to estimate the severity of the fault, more detailed mathematical and physical models have to be used.

Non-linear excitation control of a synchronous generator using robust feedback linearization

The objective of this paper is to design non-linear excitation controllers for synchronous generators using robust feedback linearization. Since disturbances acting on power systems are of random nature and since the variations in the interconnection variables, the machine currents, cannot be known with certainty, such systems have to be treated as non-linear uncertain stochastic systems. To take advantage of well-developed robust linear control techniques, differential geometry and stochastic calculus are used to transform the non-linear system to an equivalent linear uncertain system. Simulation results of a single-machine infinite-bus system indicate that the proposed controller provides a larger stability margin than that obtained using existing linear and non-linear controllers.

Stabilization of multi-machine power systems by coordinated excitation control of multiple adjustable-speed generator/motors

Since an adjustable-speed generator/motor (ASGM) is excited by ac voltage fed by a quick-response cyclo-converter, rotating speed of the rotor can be constantly changed. The ASGMs installed at some pumped-storage power stations achieve automatic frequency control during nightly demand troughs by changing the pumping power to accord with the rotating speed. It is expected, on the other hand, that under peak generation during the day, the ASGM will be used for enhancement of transient stability because it can generate or absorb active and reactive power independently via the ac excitation voltage control. This paper proposes a novel control method for the excitations systems of ASGM that will improve the transient stability of multi-machine power systems like multiple ASGMs. The controller, which is designed for an energy function, works well for stability enhancement. To gauge it against conventional excitation control of synchronous generators and against constant output power control of ASGMs, the effectiveness of the proposed method is simulated in digital trials. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (4): 10–19, 1997

Excitation Control of the Synchronous Generator by Means of Input-Output Feedback Linearization

In this paper, we present a design for synchronous generator excitation control based on a form of state-feedback linearization, known as input-output linearization. With this transformation, the terminal voltage becomes a linear function of the control input. We then design the excitation controller by using linear control techniques. For a particular example, we show that the controller provides closed loop dynamics that are small-signal stable over all practical operating points of the system

Design of robust excitation controllers for synchronous generators using the spectral and control-canonical-form methods with output feedback

The linearized modelling of a synchronous generator with exciter, along with a powerful model order-reduction method and two efficient pole-placing algebraic control methods (i.e. the spectral and control-canonical-form (CCF) using state and/or output feedback) have been presented in systematic and concise form. They are used to design a robust excitation controller of an 87.5 kVA synchronous generator with a conventional excitation system supplying power to the electric utility system through a transformer and a transmission line. The excitation controller design is based on the obtained reduced 4th-order system model of the developed single-input multiple-output (SIMO) 8th-order, linearized (about a nominal operating point), time-invariant state-space open-loop system model. It was tested at several operating points in the over- and under-excitation operating regions of the generator. All the designed systems with the above excitation controller (closed-loop system models) were tested and displayed significantly improved dynamic stability characteristics and overall system performance with reference to those of the open-loop system models. The proposed procedure for designing implementable robust excitation controllers is relatively simple to apply, as amply verified by the example given and relevant system simulations.

A nonlinear control design for power systems

In this paper, a simple exact linearization design method for scalar nonlinear control systems is discussed. Starting with the higher-order differential equation of nonlinear plant, a direct feedback linearizing compensator and a following feedback controller can be composed by physical variables of the plant. By using this method to power systems, a nonlinear excitation control of synchronous generator is proposed, which is new and effective for engineering. Digital simulation and physical experiment results of a practical power system show that the excellent stability, fast response, robustness, damping, steady-state and transient stability power limit are all achieved.

Damping of torsional oscillations using excitation control of synchronous generator: the IEEE Second Benchmark Model investigation

A simple lead-lag excitation controller using generator shaft speed deviation ( Delta omega ) as a feedback signal to damp all of the IEEE Second Benchmark Model, system-1 torsional oscillations is presented. In order to stabilize all the torsional modes, modal control theory is used to determine the parameters of the dynamic output feedback controller. Various degrees of series compensation, different loading conditions, and torsional mode shapes for a torsional oscillations study are also investigated. In addition, time-domain simulation using a nonlinear system model are examined to demonstrate the effectiveness of the proposed countermeasure under torque disturbance conditions. >

An output feedback controller for a synchronous generator

A novel approach using eigenstructure assignment is developed for the design of excitation controllers for synchronous generators. The computation procedure for the method is easy to apply, and an exact solution can be obtained without iteration. Controllers designed by the proposed approach can be easily implemented by means of proportional-integral (PI) controllers. Practical considerations in reaching an optimum selection of closed-loop eigenvalues are addressed. Time-domain simulation results are presented to verify the effectiveness of the design method.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Synthesis of excitation controllers for synchronous generators setting specified stability margins in the under-excited operating region

A design procedure of field controllers for synchronous machines is presented. A prescribed enlargement of the stable operating domain in the P-Q plane and an aperiodic type of instability for the system under steady-state instability conditions are assumed as performance specifications. The effectiveness of the proposed design procedure is validated by digital simulations on a single machine infinite bus-bar system.

Excitation Control of Synchronous Generators Using Adaptive Regulators-Part II Implementation and Test Results

A dual-rate sampling self-tuning regulator for the excitation control of synchronous generator has been implemented using M6800 microprocessor. General set up of hardware and software are described in this paper. Real time test results which compare the performance of the proposed AVR with an analog AVR are presented. This paper demonstrates that the microprocessor based adaptive AVR is a viable alternative to the analog AVRs.

Excitation Control of Synchronous Generators Using Adaptive Regulators, Part II: Implementation and Test Results

A dual-rate sampling self-tuning regulator for the excitation control of synchronous generator has been implemented using M6800 microprocessor. General set up of hardware and software are described in this paper. Real time test results which compare the performance of the proposed AVR with an analog AVR are presented. This paper demonstrates that the microprocessor based adaptive AVR is a viable alternative to the analog AVRs.

Excitation Control of Synchronous Generators Using Adaptive Regulators Part I-Theory and Simulation Results

A recent trend in power system operation is towards computerised control and management. One class of digital adaptive regulators called self- tuning regulators is suitable for this purpose. In synchronous generator control a conflict arises between the small sampling interval necessary to track the dynamics and large computation time required by the process computer. A dual-rate sampling model is suggested to alleviate this problem. A class of self-tuning regulators called Dual-rate Sampling Self-Tuning regulators which use a dual-rate sampling model of the power system are described in this paper. Simulation results obtained are used to evaluate the merits, usefulness and viability of the proposed regulator.

Excitation Control of Synchronous Generators Using Adaptive Regulators, Part I: Theory and Simulation Results

Excitation Control of Synchronous Generators Using Adaptive Regulators, Part I: Theory and Simulation Results

Optimal excitation control of non-linear power systems

Reviews and discusses developments in optimal excitation control of synchronous generators. The control problem is stated, taking non-linear aspects of the power system into account. Various methods of solution are described and assessed for practical application purposes. An approach in which the control is formulated by a first order term plus a set of higher order terms, representing non-linear components, appears to offer distinct advantages with respect to computing effort and application. Some results of system studies, incorporating optimal excitation control by this approach, are presented and discussed briefly in the paper.

Stabilization of a power system via excitation control of two‐axis synchronous generators

The effectiveness of power system stabilization by means of excitation control of 2-axis synchronous generators was confirmed experimentally using a small-size model system. Since the field winding time constant of the small generator is smaller than that of the large generator, auxiliary windings were attached to field windings to increase the field winding time constant. First the features of the proposed control scheme are demonstrated by digital simulation on a one-machine infinite-bus system. Next, using an experimental one-machine infinite-bus system, it is shown that the proposed method makes it possible to control the output power to a fixed value in a nonoscillatory way and suppress the speed variation of the generator rotor. Third, we study whether the proposed control scheme works satisfactorily even if the infinite-bus voltage varies. As a result of this study, it is shown that the proposed scheme works satisfactorily when a large-capacity generator exists which can be regarded as the infinite-bus system or when an induction motor load exists at the mid-point of the transmission line. Also it is confirmed that the high-speed state variable detectors used for the experiment are very accurate and reliable. (LCL)

Optimal and suboptimal excitation control of dual-excited synchronous generators

A detailed study is made of both optimal and suboptimal excitation control of a synchronous generator with two field windings. Optimal controllers based on a linearised system model, obtained by the solution of the corresponding Matrix Ricatti equation, are compared with suboptimal controllers based on the complex nonlinear model and obtained by function minimisation using dynamic sensitivity functions. The comparison is made for both dynamic (small change) and transient (large change) conditions.

Optimized Transient Stability from Excitation Control of Synchronous Generators

A digital computer study of synchronous generators which aims to optimize transient stability is described. Mathematical modeling checked by site tests is used, and alternative excitation controls are investigated. It is shown that the appropriate excitation control can produce substantial positive damping of rotor angle excursion without prejudice to the automatic voltage control.