Study On The Conducted Electromagnetic Interference Of Electric Automotive Motor Drive System

The motor drive system is main source of electromagnetic interference(EMI) inelectric vehicle electromagnetic compatibility (EMC),because the electromagneticemission from the system has the characteristics of high-energy and wide-bandwidth,the EMI of motor drive system not only affects the electromagnetic compatibility ofautomotive electrical systems, but also becomes the biggest obstacle for meeting thestrict EMC standard. This thesis supported by the National Natural Science Foundationof China," EMC basic research， the electromagnetic environment analysis andoptimization in the high voltage systems of electric vehicle "（No51177183）,study onthe conducted electromagnetic interference of electric automotive motor drive system,the main research contents are following:①Understand the working principle of motor drive system in electric vehicle,including the working principles of motor controller and three-phase bridge DC/ACinverter power main circuit. Analysis the electromagnetic interference mechanism inelectric automotive motor drive system.②In conductive EMI frequency range, build broadband equivalent circuitmodel of every component in motor drive system for predicting the conductive EMIand use that as the prediction EMI method. According to the theory of multi-conductortransmission line(MTL), build the transmission line model of cables. Use analyticmethod to solve the resistance parameter of unit length cables and finite elementmethod(FEM) to solve the capacitance, inductance parameter of unit length cables inMaxwell2D.③This thesis proposes a theory,witch utilize resonance unit to constructbroadband equivalent circuit on the basis of port impedance amplitude frequencycharacteristics, this theory apply to building permanent magnet synchronous motorbroadband equivalent circuit model.④This thesis built motor drive system platform for measuring conductive EMIin shield room. Based on the physical size and parameters of parts in experimentalplatform, built broadband equivalent circuit of all parts. All the model connected eachother at Saber in accordance with electrical connection on the platform. Simulated andpredicted the conductive EMI on the LISN of battery anode and compared with themeasurement data from0.3MHz to30MHz. From the contrast results, prove the method of predicting conductive EMI in motor drive system is correct and feasible. Italso prove that the broadband equivalent circuit model of permanent magnetsynchronous motor and cables are correct.⑤Hybrid electric vehicle was used as experimental platform, at four differentworking state(starting, idling, high speed, charging), measured not only the conductedinterference current spectrum of DC/AC inverter input, output cable in motor drivesystem, but also the voltage time domain waveform between collector and emitter ofIGBT in DC/AC inverter. Through the comparison of the measurement data, thebandwidth and the coupling path of electromagnetic interference in motor drive systemare determined, the electromagnetic interference mechanism in automotive motor drivesystem is accord with theoretical analysis, prove the theoretical analysis is correct.