Study on AC-DC-AC locomotive modeling based on probabilistic harmonic current source

The AC-DC-AC locomotives' load characteristics are very different from those of AC-DC locomotives,so it is of great significance to build a proper model of AC-DC-AC locomotive for power system safety analysis and relative power quality evaluation.On the basis of a large amount of measured data,this paper analyzes the probabilistic representation of harmonic current generated by AC-DC-AC locomotives,using an improved maximum entropy method,and a current source model is set up using the PSCAD/EMTDC software.The fundamental component,which can simulate the problems brought about by traction load to power system caused by its impact and asymmetry,is achieved from a three-level four-quadrant converter.The harmonic component is generated by a probabilistic harmonic current source with the use of MATLAB interface module,taking into consideration the effects many random factors have on harmonics.Since the harmonic current model is based on measured data,the simulation result has a better agreement with practical situation.