Current Harmonics Generated by Motor-Side Converter: New Standardizations

Abstract

Pulsed width modulation (PWM) voltage generated by power converters creates current harmonics in the range of 2-150 kHz. To address the challenges created by these harmonics, new standards for harmonic emission within that frequency range is being developed. Thus, these current harmonics need to be determined and then mitigated by electromagnetic interferences filters. A mathematical model of harmonics is vital for filter design to ensure compatible operation of the device with new standards. In a power converter with a diode rectifier and motor-side inverter, a considerable portion of the inverter current harmonics within 2-150 kHz can spread to the grid side of the converter. The nonideal dc-link capacitor in a practical drive, which has a higher impedance in a 2-150-kHz frequency range due to its series of inductive and resistive elements, cannot effectively absorb the high-frequency inverter input current harmonics. Thus, a mathematical understanding of the motor-side inverter input current harmonics is vital to evaluate the grid-side current harmonics of the power converter based on the dc-link capacitor and grid impedance characteristics. Consequently, a mathematical analysis is presented in this article to extract the required equations to find the motor-side inverter input current harmonics. Simulation and practical results have confirmed the accuracy of the obtained equations.