Overmodulation in Voltage Source Inverter with Small DC-link Capacitor

Abstract

Overmodulation (OM) is used to increase the voltage output of the PWM controlled frequency converter. Full inverter voltage utilization is important because of the cost and output power improvement perspectives. The voltage source inverter (VSI) with high overmodulation performance is less sensitive to inverter DC-link voltage disturbances. DC-link voltage drop may result in unintentional entrance to the Overmodulation region. DC-link drop is often due to line voltage sag or fault conditions. When small DC-link capacitor is used, voltage drops due to full-wave rectifier bridge are present all the time. A high performance overmodulation method improves the drive performance under such conditions