| Because of advantages of high speed, low cost and pollution-free,electrified railway transportation has made a series of high speeddevelopment. However, because of its one-way, mobility, nonlinearcharacteristics, electrified railway load brings the power grid powersystem a lot of negative effect that cannot be ignored. So electrifiedrailway sequence and effective governance of harmonic and negativesequence wave is a major issue to be solved urgently.The traction transformer connecting the power system and externaltraction power grid is a key equipment in energy transformation of thewhole system. Traditional traction transformer could only be used forconverting three phase system to two phase system, while this papermainly studies a novel traction transformer that can control the thenegative sequence and harmonic current.The thesis first analysed the negative sequence and harmonic controlof transformer topology, compared with characteristics of several common traction negative sequence suppression, and then analyzes the harmonicshielding harmonic control ability of the transformer. The paper analysedthe electromagnetic filed of the single phase harmonic shieldingtransformer, calculated of short circuit impedance, compared conditions ofthe the winding current and winding’s electromagnetic force. A newdrawing method based on harmonic-balance finite element is proposed fordrawing the harmonics of the magnetic flux distribution and studied thecharacteristics of the harmonics of the magnetic flux distribution in thispaper. The transformer2D axisymmetric finite element models wasestablished and simulated in the ANSOFT software, and the program iscompleted in MATLAB software to draw the distribution of harmonic flux.The conclusion showed that the local vortex characteristic of fluxdistribution in each harmonic, and the relationship between the localvortex characteristic of flux distribution and harmonic flux was analyzed.Finally the paper combine advantages of V/V type tractiontransformer and harmonic shielding transformer, and put out a thought ofconstituting V/V type by harmonic shielding transformer, and then put forward a thought of adding a set of railway active regulator (RPC) in thisnew V/V traction transformer in order to realize the unification of thenegative sequence and harmonic governance functions. This paperestablished the circuit simulation model, and tested it under severalconditions and got a conclusion that it can inhibit both negative sequenceand harmonics. |
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