C.M. Lim

APPLICATION OF FUZZY LOGIC CONTROL SCHEME FOR STABILITY ENHANCEMENT OF A POWER SYSTEM

Abstract This paper presents a fuzzy logic stabilizer for stability enhancement of power systems. Based on the condition of the study generator, and with the aid of two membership functions and a set of simple control rules, the stabilizing signal is determined. The generator condition is defined in terms of its speed deviation Δω and acceleration α, i.e., by the point (Fa α, Δω) where Fa is the weighting parameter for α. Results from nonlinear simulation studies show that the proposed fuzzy logic stabilizer can enhance the damping characteristics and the robustness of a power system.

Internal model structure in the control of robot manipulators

The conventional internal model control (IMC) structure commonly used in the process control field is applied for the control of robot manipulators. A pre-compensation structure, which comprises a linearizer and a stabilizer, is used to modify the dynamics of the robot manipulator so that the standard IMC structure can be implemented without violating its original straightforward and intuitive design principle. Analysis of this robot IMC structure reveals that this control algorithm can actually be considered as an enhancement of the conventional robot computed-torque control scheme. Both simulation and experimental results demonstrate that this proposed robot IMC scheme has significantly improved performance as compared with that for the conventional robot computed-torque control algorithm, especially in the presence of modelling uncertainty and external disturbances.

New approach to power system stabilizer design

Abstract A generalized method for the design of excitation control or a power system stabilizer (PSS) based on complex frequency is described. The method selects PSS parameters such that exact assignment of eigenvalues associated with the mechanical modes of oscillation to desired locations is achieved. Numerical examples are used to illustrate the concepts of the proposed new technique.

Comparison study between a fuzzy logic stabiliser and a self-tuning stabiliser

Abstract This paper presents the findings of a performance comparison study between a self-tuning stabiliser and a fuzzy logic stabiliser with reference to the damping of the mechanical-mode oscillations in electric power systems. In the studies, different tests were simulated with the nonlinear power systems operating over a wide power range. Simulation results show that both stabilisers are suitable for and effective in enhancing the damping of the mechanical-mode oscillations in a single-machine infinite-bus power system and two multi-machine power systems without an infinite bus of which one exhibits multimmode oscillations.

Experimental implementation of a fuzzy logic control scheme for a servomotor

Abstract This paper describes the experimental implementation and evaluation of a rule-based, fuzzy logic control scheme applied to a d.c. servomotor. The advantages of the proposed scheme for servosystems are highlighted. Specifically, it is shown that the proposed scheme is simple in structure and can therefore be readily implemented as it requires the measurement of only one system variable. Typical experimental results obtained are presented and, for comparison purposes, results corresponding to a P.D. control scheme are also included. These results show that the proposed scheme is effective in controlling the shaft position of the servomotor under light and heavy load conditions.

Digital stabilizer design for optimal performance of power systems

Abstract A new method of designing a digital power system stabilizer is presented. In this method, linear discrete-time models of assumed order are used to describe the power system dynamics and the recursive least-squares algorithm is employed to identify the model parameters. Based on the identified parameters, the digital stabilizer is designed such that a modified version of a conventional quadratic performance index is minimized. As a result, the proposed digital power system stabilizer possesses a derivative term not found in the conventional stabilizer, and therefore is suitable for further enhancement of a power system performance. This feature of the proposed stabilization scheme is illustrated using two numerical examples.

Implementation and experimental studies of fuzzy PID controllers

Abstract This paper describes the experimental implementation and evaluation of two fuzzy proportional-integral-derivative (FPID) controllers. The primary objectives are to verify that (a) FPID controllers provide better performance that a conventional PID controller and (b) the structure of an FPID first reported by Chen and Chen [ Comput. Ind. 17 (1991)] can be simplified without any deterioration in performance. Typical results obtained from experimental studies which involved the control of a D.C. servomotor system are presented.

Application of a self-tuning control scheme to a power system with multi-mode oscillations

Abstract A self-tuning control scheme is proposed and its effectiveness for the purpose of enhancing the damping of multi-mode oscillations in a power system is examined. Simulation results show that the proposed self-tuning stabilizer is suitable for and can cooperate with conventional stabilizers in providing enhanced performance to a power system with multi-mode oscillations.

Implementation and experimental study of a fuzzy logic controller for DC motors

Abstract In a recent work a fuzzy PID controller has been shown to provide good system performance in the presence of a disturbance. However, these encouraging results were obtained through simulation studies. In this paper, the effectiveness of the same fuzzy PID controller is examined through real-time experimental studies instead.

A ROBUST SELF-TUNING POWER SYSTEM STABILIZER

A robust self-tuning control scheme for stability enhancement of power systems is presented in this paper. An integrator driven by the tracking error is included into the control loop such that the closed-loop system exhibits consistent performance with fast transient recovery under large load changes and over a wide range of operation conditions. Results from nonlinear simulation studies confirm the effectiveness of the proposed control scheme for single-machine and multimachine power systems.