Probability Model of Traction Load Harmonics Based on Least Square Approximation

Mostly traction loads are AC/DC type loads. A great lot of harmonic produced by electrified locomotive (mainly including order 3, 5 and 7) is directly injected into utility. The effect of harmonic to utility must not be ignored. But traction loads have different characteristics from normal loads in power system, such as random and unbalance. So traction load harmonic also has random time-varying characteristic. The distribution characteristics of traction load harmonic are analyzed based on a great deal recorded harmonic data in this paper. Curve fitting for distribution characteristics based on least square approximation is carried out, and probability density function of traction load harmonic is obtained. The accuracy of the proposed model is verified by error analysis. The exact traction load harmonic model is helpful for studying on traction load harmonic.