Abstract
This paper presents a Norton approach for modeling distribution networks where the system configuration is not fully known. Traditionally, harmonic studies use complex distribution networks modeled by harmonic current sources for specific frequencies. Although this approach has been proved to be adequate for some studies, this may not happen for other applications. When changing the operating condition of the supply-side system, the harmonic currents injected by the distribution network might change. This information is in this paper used to estimate a Norton model of the load-side distribution network. The estmated models can be used to analyze, for example, the effect of harmonic filters under different supply system configurations or operating conditions. The method of estimating the Norton models is illustrated on a test system, simulated on the well-known simulation program EMTDC. The performance of the estimated models is, for different configurations of the supply system, compared to the performance of the traditionally used “constant current” approach.
I. INTRODUCTION
The use of power electronics-based devices in power systems has increased steadily over the last decades. Electronics devices are nonlinear and thus they create distorted currents even when supplied with purely sinusoidal voltage. These distorted currents cause voltage and current distortion throughout the system which can result in additional heating in power system equipment, unmotivated switching of breakers, blowing of fuses, and interference with communication systems [ 11, These electronics devices are also more sensitive to power quality variations than equipment applied in the past. Microprocessor based controls applied in these electronics devices are sensitive to many types of disturbances which can result in nuisance tripping, misoperation or actual device failures. This is becoming a major concem for the industry.
