| With a large number of harmonic load access to the grid,harmonic pollution problems become more and more serious.Traditional transformers are design,based on the power frequency.Harmonic problems on the transformer made a new request for transformer.The characteristics of the transformer under the influence of harmonics are directly related to the accuracy of the whole energy metering system.Therefore,it is of great theoretical and practical significance to study the characteristics of the transformer considering harmonic factors.In this paper,several typical harmonic loads,such as railway traction load,intermediate frequency furnace,electric arc furnace,rectifying load and electric vehicle charging pile are selected as the research object.The harmonic characteristics of these loads are studied and the current or voltage waveforms of these loads are analyzed synthetically.The transfer function of the CVT is established considering the harmonic factor and the SIMLINK simulation model of the CVT is built.The transfer function reflects the effect of the equivalent parameters of the components on the frequency characteristics of the CVT.The theoretical analysis of the frequency characteristics of CVT is verified by SIMLINK simulation experiments.In order to improve the simulation accuracy of the electromagnetic current transformer frequency characteristic,this paper analyzes and compares some typical current transformer model,and finally selects the J-A current transformer model.The effect of harmonic frequency,amplitude and phase on the error of electromagnetic current transformer is studied by using the superimposed single harmonic method.Harmonics will interfere with the saturation detection of current transformers.In this paper,a new method of current transformer saturation detection based on improved S transform is proposed.The saturation model of PSCAD current transformer is established.The simulation results show that the method has good anti-harmonic and anti-noise ability. |
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