S.J. Cheng

An expert system for voltage and reactive power control of a power system

A methodology called the sensitivity tree, which can be easily used to form an expert system for real-time control, is proposed. Based on this methodology, an expert system for the control of voltage and reactive power of a power system is developed. The main objective of this expert system is to help the operator detect buses experiencing abnormal conditions, select the most effective control measures, and calculate the control actions required to overcome the voltage violation. The control measures used to alleviate the voltage problem are capacitor compensation, transformer tap changes, and generator terminal voltage changes. By keeping the bus voltage in the entire system within limits, system security is increased. The expert system is written in the PROLOG language. Simulation studies with this expert system applied to a 30-bus power system show satisfactory results. >

Damping of multi-modal oscillations in power systems using a dual-rate adaptive stabilizer

The ability of a dual-rate adaptive stabilizer to damp multimode oscillations in a power system is investigated. The controller adjusts its parameters to track the dominant frequency of oscillation and damps different modes one by one according to their dominance. The results show that adaptive and conventional stabilizers working on different units within a system can operate cooperatively and mutually support each other. >

A Self-tuning Power System Stabilizer

Abstract A self-tuning power system stabilizer using a recursive least-squares identification algorithm with varying forgetting factor and self-searching pole-shift control algorithm has been developed. Application of this controller to a multi-input multi-output system for a generating unit-field excitation and governor control, and in the form of a dual-rate control strategy to further improve the properties of the stabilizer for fast acting systems, is described in this paper. Results of studies demonstrate the effectiveness of the proposed controller.

An Adaptive Power System Stabilizer

Abstract The evolution of the adaptive control concept in which a controller continuously tunes itself to the changing plant characteristics, has provided an attractive design alternative to the conventional approach. A microcomputer based power system stabilizer using the self-tuning adaptive control concept is described in this paper. The recursive least squares identification technique with a variable forgetting factor, and the variable pole shifting control form the controller algorithm. Feasibility of the proposed design is established by tests, results of which are given in the paper.

A data base management system and its application in a voltage and reactive power control expert system

Abstract A data base management system (DBMS) is a large collection of system information and it can be accessed by more than one user. It is, therefore, very useful when the controlled system is a large interconnected system, such as a power system. A prototype DBMS for use with an expert system developed to assist in power system operation is presented in this paper. General considerations and techniques of designing the DBMS are given. The prototype is written in an artificial intelligence language, Quintus Prolog, and it is easy to interface with the Prolog written expert systems. In addition, as Quintus Prolog can interface with other high level languages, the prototype DBMS can be used with application programs written in these languages. An example of applying the prototype DBMS to a voltage and reactive power control expert system is used to demonstrate its effectiveness.

PERFORMANCE OF AN ADAPTIVE POWER SYSTEM STABILIZER IN A MULTI-MACHINE SYSTEM

The multi-mode oscillation problem occurs in multi-machine power systems when the rotors of machines, behaving as rigid bodies, oscillate with respect to one another using the electrical transmission path between them to exchange energy [1]. The ability of an adaptive self-tuning stabilizer to damp out the multi-mode power system oscillations is investigated in this paper. The studies show that such a stabilizer is very effective as it damps out the multi-mode oscillations one by one according to their dominance. Keywords: Adaptive controller; Power system stabilizer; Multi-mode oscillations

MICRO-COMPUTER IMPLEMENTATION OF AN ADAPTIVE POWER SYSTEM STABILIZER

Implementation of a micro-computer based self-tuning power system stabilizer with standard off-the-shelf components is described in this paper. The hardware configuration and the flexibility in the design of software structure for user interface are highlighted. Feasibility of the design is established by laboratory testing.

Performance of an Adaptive Power System Stabilizer in a Multi-Machine System

Abstract The multi-mode oscillation problem occurs in multi-machine power systems when the rotors of machines, behaving as rigid bodies, oscillate with rcspcct to one another using the electrical transmission path between them to exchange energy [1]. The ability of an adaptive self-tuning stabilizer to damp out the multi-mode power system oscillations is investigated in this paper. The studies show that such a stabilizer is very effective as it damps out the multi-mode oscillations one by one according to their dominance.

Micro-Computer Implementation of an Adaptive Power System Stabilizer

Abstract Implementation of a micro-computer based self-tuning power system stabilizer with standard off-the-shelf components 1s described in this paper. The hardware configuration and the flexibility in the design of software structure for user interface are highlighted. Feasibility of the design is established by laboratory testing.