A Prediction Method of Higher Harmonics Resonance in Distribution System

There are many PWM control apparatuses, which are higher harmonics current sources, in distribution systems. And higher harmonics causes over current by parallel resonance. To avoid the over current, it is necessary to predict frequency characteristics of resonance. In this paper, a new prediction method is proposed. Firstly the line model, in which frequency characteristics of line inductance and resistance are taken account, are approximated by R-L parallel circuits. And then, using eigen value and eigenvector, the problem is decomposed to each eigen mode problem. Moreover, to get a bird's-eye view of phenomenon, a variable separate type approximate is introduced. Finally a new index matrix, which gives the distribution of over current, is introduced.