Analysis and optimisation of electromagnetic interference in motor drive system

The integrated power unit (IPU) is an important source of electromagnetic interference in hybrid electrical vehicles. In this paper, applying pulse width modulation (PWM) technology, IPU converts the high-voltage DC power from power battery into three-phase AC power with adjustable voltage amplitude and frequency through the switching device IGBT to drive the permanent magnet synchronous motor. Due to the large di/dt and du/dt during the IGBT switching process, the spectra of switching voltage and current waveforms have rich high-frequency components, which generate electromagnetic interference through the circuit connection or space radiation, affecting the normal operation of electrical systems inside and around the car. Therefore, this paper analyses the electromagnetic interference mechanism and coupling propagation paths of motor drive system. The test bench of IPU was built, and the EMI characteristics of IPU were analysed based on the measured results. Finally, in order to suppress IPU electromagnetic interference, the corresponding methods are proposed to meet the electromagnetic compatibility requirements of the vehicle.