Research On Permeation Mechanism Of Harmonics And Negative Sequence In Power System

Power system can be treated as a whole as interlinked by different voltage grade, some customers cause harmonics and negative phase sequence. Nowadays harmonic penetration and negative phase sequence penetration have become worldwide concern both to electric departments and to power custemers. In order to guarantee the safe run of grid and reduce the harmful effect meanwhile to ensure the healthy development of non-linear users under condition of reasonable restriction, to work out a reasonable harmonic restrict index should be based on the law of harmonic's penetration.On the basis of three phase model of each component within grid, the paper worked out a three phase power flow calculation program and explored out a friendly interface with application of matlab Software, which can be used for the calculation of negative phase sequence generated from traction load and the distribution of harmonic within grid.The paper gives theoretical discussion of the law of harmonic's penetration in the grid by introduction of Subcircuit Analysis Method and Network Analysis Method, and studies the impact of traction substation's power incoming line on the harmonic penetration. In order to overall evaluate the harmonic penetration among different voltage classes in the grid, harmonic comprehesive permeability coefficient was presented in this paper and the effect of different harmonic models and variations of load on the overall permeability coefficient was discussed as per typical grid.Last but not least, the penetration state of harmonic generated from traction load in Gansu Dingxi Grid and Sichuan Xichang Grid was studied in the paper according to actual measurement data. And the effect on the harmonic penetration of Distributed capacitance of Power Transmission Line and Compensation Device of Traction Substation was discussed emphatically. Through comparison of calculation results in these two grids, some laws of harmonic penetration in the grid were concluded, which provided strong base for further harmonic penetration study.