Showing papers by "Jovica V. Milanovic published in 2003"

Load modeling for voltage sag studies

Abstract: This paper investigates the influence of load modeling on voltage sag characteristics and compares the results of voltage sag calculation with different load models. It is shown that some voltage sag characteristics are strongly influenced by the models chosen for representing power system loads. Therefore, depending on the aims of the voltage sag study, load models need to be carefully chosen.

Influence of voltage sags on personal computers and PWM drives

Abstract: This paper discusses the sensitivity of personal computers and PWM drives to voltage sags and short interruptions on the basis of extensive test results. The results of the following tests are presented in the paper: testing against various types of single-phase, two-phase and three-phase voltage sags and short interruptions, as well as testing with the ideal and non-ideal supply characteristics. Presented test results show that behavior of both equipment types in the general case cannot be described with only one voltage-tolerance curve. Instead, families of voltage-tolerance curves should be used for description of the PCs and PWM drives sensitivity to voltage sags and short interruptions. Special attention is given to similarities in responses between these two equipment types, what is discussed in detail.

New Digital Multispeed Method for Indirect Measurement of Transient Electrical and Shaft Torques

Abstract: This paper presents characteristics and solutions to some practical problems concerning the new digital Generalized Indirect Multispeed Method (GIMSM), for measurement of transient electrical and shaft torques occurring in a complex serial multimachine AC drive system. The method indirectly includes torsion and internal machine and shaft damping. It is based on the measurement of the transient speeds, using high resolution digital tachometers, of every lumped inertia component. Obtaining the torque values requires digital filtering, followed by numerical differentiation and integration. This procedure depends on the type of the transients and the electrical and mechanical characteristics of the drive. The measurement of transient torques using the proposed method is realized in the laboratory on a two-machine induction motor (IM) drive. The results of the measurements of the electrical and shaft torques during the acceleration and speed reversal are presented in this article. The article further recommend...