Study On The EMC Of PWM Drive Motor System Of Electric Vehicle

In recent years, the electric vehicle developed quickly. Compared with thetraditional cars, its electrical integration degree is higher, and the frequency band ofelectronic devices is more and more wide. As a result, the influence between eachelectrical device is more and more serious. The motor drive system with high voltage,large current and diverse coupling paths is one of the main interference sources ofelectric vehicle. It seriously affects the electromagnetic compatibility (EMC) of electricvehicle. In this paper, taking the PWM drive motor system of a mini electric car as theresearch object, and considering its conduction common mode (CM) interference anddifferential mode (DM) interference between each other, the research on conductedelectromagnetic interference (EMI) for PWM drive motor system can providetheoretical and technical support for the inhibition of the EMI of motor drive systemand EMC performance of electric vehicles improving, which has important theoreticalsignificance and practical value. The main contents include:①According to the structure and control theory of PWM drive motor system, adetail analysis of the mechanism of EMI production has been completed. Theconduction CM and DM propagation paths are studied, and the interference voltageexpressions in the motor side are analyzed and deduced, which lay the foundation forthe study of motor drive system EMI.②The conduction EMI prediction model of motor drive system is put forward.By using the multi-conductor transmission line theory, the high frequency circuit modelof the inverter input and output cables are established. Meanwhile, the values ofresistance per unit length are calculated by using the analytical methods, and the valuesof inductance and capacitance per unit length are calculated by using the finite elementmethod via the Maxwell2D.③By measuring the AC induction motor port CM and DM impedanceamplitude-frequency characteristic, the high frequency equivalent behavior model ofAC induction motor has been built by using ideological resonance units which has beencertified. Meanwhile, the calculation methods of resistance, capacitance and inductanceparameter are deduced.④The drive circuit of IGBT switch is designed, meanwhile, the circuit model ofother components of motor drive system has also been built. Then the prediction model of motor drive system EMI is established in accordance with the actual connection, andsimulated between frequency ranges0.15-30MHz. The frequency domain waveform ofconducted interference current has been tested by using the experiment test platform ofmotor drive system which built before. The compare with the simulation results showsthat the prediction model of PWM drive motor system EMI is feasible.⑤The EMI suppression techniques are analyzed, and meanwhile, the filter ring,shielded cables, shielded inverter are used in the suppression measures of motor drivesystem, which have been certified that these suppression measures are valid viaexperiments and simulation.