Research On Modeling Method Of Transformer Broadband Equivalent Circuit Model

Nowadays,the power electronics technology has been changing.We are not familiar with electromagnetic interference.The EMC problem is no longer limited to military,but widely used in communication,electrical equipment,medical devices and other fields.And people pay more and more attention to EMC.Electromagnetic interference often leads to failure of power electronic equipment or system,which may damage the equipment or even endanger our health.In view of EMC,many organizations at home and abroad have formulated various EMC standards according to different equipment and different scenarios.For example,IEC 61000 series EMC standards formulated by IEC,China has formulated GB/Z 17626 series EMC standards in China with reference to this standard.Transformers are widely used in various power electronic equipment or systems.Most of these devices or systems have switch devices.When they are in working state,the change rate of voltage and current is often large,which will produce electromagnetic interference,especially in switch devices,transformers,capacitors and inductors.Generally speaking,the internal structure,size and material of transformer are unknown,which are related to the distribution parameters of transformer,so the parameters can only be obtained through the external port of transformer.The accuracy of transformer equivalent circuit model often affects our research on EMC of power electronic equipment or system.This thesis first introduces the working principle of transformer and the problem of transformer modeling.The modeling method of three capacitor equivalent circuit model andπ type equivalent circuit are given.The model of three capacitance equivalent circuit of transformer is analyzed and deduced from the angle of inductance and capacitance.The meaning of parameters in the model is introduced.The method of obtaining parameters in the model is given.Taking a practical transformer as an example,the model of three capacitance equivalent circuit is established;This thesis introduces the vector matching method,its solution process and circuit synthesis theory,and the measurement and calculation methods of the parameters in the π type equivalent circuit model are given,then the π type equivalent circuit model is established;In order to analyze the transmission interference of power electronic equipment or system accurately,considering the transmission characteristics and the influence of distribution parameters on the transformer,a wide frequency equivalent circuit model of transformer is proposed.One is the three capacitance equivalent circuit model of medium and low frequency,the other is based on vector matching method π model of the two parts of the equivalent circuit is parallel,and the model of the transformer is obtained.Finally,the correctness of the model is verified by comparing the simulation and experimental results.The model of transformer wide frequency equivalent circuit can reflect the transmission characteristics of transformer more accurately,and can better reflect the transmission path of conduction interference.In this thesis,the equivalent circuit model of transformer is studied,Test method and calculation method of three capacitance equivalent circuit and π type equivalent circuit are proposed.Based on the existing theory,considering the transmission characteristics and the influence of distribution parameters on the transformer,a wide frequency equivalent circuit model of transformer is proposed,and the test and calculation method of parameters in the model are given.Taking a practical transformer as an example,The three capacitance equivalent circuit model,π type equivalent circuit and broadband equivalent circuit model of the transformer are established.The results of simulation and experiment are compared to verify the correctness of the broadband equivalent circuit model.