Dynamic load model synthesis

Abstract

The paper develops methods by which groups of individual loads supplied from power networks may be represented equivalently in composite form in evaluations of dynamic modes of network operation and the limiting conditions of stable system operation related to them. Central to the methods developed is a formal, parameter-identification procedure by which values are found for the parameters which define an initially postulated equivalent-load representation. All of the steps of analysis and modelling underlying this procedure are developed in detail in the paper, leading to a systematic sequence of dynamic load model synthesis. In validating the methods developed, they are applied in the paper to earlier system tests in which a total of 23 auxiliary motors were isolated from the turbogenerator unit with which they are normally associated and supplied through a transmission circuit from a neighbouring power station. Controlled short-circuits at one end of the transmission line precipitate dynamic operating conditions in which the principal transients of the auxiliary drives are recorded. Test conditions were formulated which project the auxiliaries towards the limits of their capabilities in recovering to steady operating conditions on fault clearance. While these represent especially demanding conditions for which to synthesise equivalent load models, it is shown in the paper that the methods it develops lead to a single composite model for all 23 auxiliary motors, and which, when included in dynamic simulation of the system tests, closely reproduces the measured transients.