Accurate Analytical Calculation of the DC-link Capacitor Current for Three-phase Motor Drive under the Full Working Range

The dc-link current is an important indicator for the design and selection of dc-link capacitors for voltage source inverter (VSI). The traditional dc-link current analysis for two-level three-phase VSI based motor drive only considers ac fundamental phase current and neglect the ac high-frequency current ripple caused by the pulse width modulation (PWM) process. Thus, this paper introduces an accurate analytical method of the dc-link capacitor current by taking the real-time ac high-frequency current ripple into consideration. Moreover, the accurate calculation of rms current on the dc-link capacitor has been provided with the traditional PWM methods, and the time-domain comparison of dc-link current has been studied under the wide range of adjusting speed and power factor. Simulation and experimental results are both provided to validate the accuracy of the proposed method.