Study On Simulation Technique Of Influence To Grid Power Quality Caused By Electrified Railway

The electrified railway is single-phase and nonlinear load, so the influence to grid power quality caused by electrified railway is concerned both by railway departments and electric management departments. Under the circumstance of installing online monitor equipment being stricted, a feasible way to analyse the power quality is calculating the nodes’power quality condition using known current source information. To make the penetration of negative and harmonic current generated by traction load analyzed more convenience, it’s necessary to develop one professional software to analyze the influence to grid power quality caused by electrified railway.The penetration condition in the power system of the negative and harmonic current generated by electrified railway is analyzed with the three-phase analysis method in this paper. At first, this paper established the three-phase model of power system main components and traction substations. Based on the multi-winding transformer theory, the three-phase model of three-winding transformer is deduced, and the singular problem of the three-phase admittance matrix is solved by adding additional conditions. And then, based on the three-phase models of the components, the method of forming system admittance matrix, the negative and harmonic current penetration algorithm and impedance frequency characteristic calculation method is introduced.According to the penetration theory algorithm, simulation software NeHarm1.0to analyze the influence to grid power quality caused by electrified railway is developed by C#on the development platform Visual Studio2010. The design idea, framework block diagram and realizing flow chart of the software are presented. The relationship between the classes, class librarys and executable files used in the software are introduced in detail. The topological structure can be built and the parameter of the components can be set on the platform of software NeHarm1.0. Also, the software NeHarm1.0can calculate the voltage unbalance degree, harmonic ratio of voltage, total harmonic distortion of voltage (THDU), branch negative current, branch harmonic current and impedance frequency characteristic. The calculation results can be presented in the form of EXCEL table and curve chart.At last, the influence of power quality to Quzhou power grid of Zhejiang province caused by electrified railway is analyzed by the software NeHarm1.0. And the voltage unbalance degree, harmonic ratio of voltage, THDU results of all the nodes, the negative current and harmonic current of all branches are calculated. Compared with the actual results, it indicates that the software NeHarm1.0calculates correctly.