A MICROPROCESSOR BASED POWER SYSTEM STABILIZER

Abstract

A power system stabilizer is a control device which is added to an electrical generator to damp low frequency oscillations that may occur in electrical power networks. Since a power network is in a continuous state of change, it is difficult to design a stabilizer flexible enough for optimum operation. Flexibility and adaptability can be obtained with a digital power system stabilizer; however, present digital stabilizers are expensive and use outdated technology. This thesis describes the software development for a digital computer system for the purpose of providing stabilizing signals to electrical generators. The computer system includes two independent microcomputers designed to act together as a supervisor and a stabilizer. The function of the supervisor is to provide an effective communications interface between the stabilizer and the operator. The interface is realized through serial communications, or for maximum data transfer, through a parallel connection. The serial communications will allow remote access to the stabilizer functions. Also demonstrated is the conversion of continuous stabilizer transfer function terms to their discrete versions. The discrete design of a digital notch filter is described briefly. It is shown that the responses of the discrete transfer function terms are similar to their analog counterparts. Slight inaccuracy due to number truncation during the transfer function calculations is illustrated. The execution time of each stabilizer term, along with the software overhead involved is given. The resultant digital stabilizer with features such as online tuning, data acquisition, and self checking is shown to perform as designed.