Comprehensive Analysis for DC-Link Capacitor Sizing for a Three-Phase Current-Controlled Voltage-Source Inverter

An analytical approach to size a dc-link capacitor for a three-phase current-controlled voltage-source inverter used for a permanent magnet synchronous motor is presented in this article considering the dc-link ripple voltage and capacitor ripple current. The analytical method derived in this article shows the variation of the dc-link voltage ripple with the change of the power factor and the modulation index. This analysis can be applied to determine the maximum possible ripple voltage for a given capacitor or the minimum capacitance needed to keep the voltage ripple under a limit. Then, current ripple analysis is used to determine the root-mean-square capacitor ripple current taking account of the thermal duty cycles of the application. Finally, capacitor life estimation analysis is used using the operating condition, thermal duty cycle, and ripple current to determine the capacitor end life for a given application. The research presents a sequential process to select a dc-link capacitor accounting for the electrical and thermal requirement of the system. The analysis is verified by simulation and experimental results, where the effect of components’ parasitic on the voltage and current ripple is presented.