Inverter DC-link stabilizing control with improved voltage sag ride-through capability

Previously published results concerning instability of the DC link in inverter drives fed from a DC grid or via a rectifier are extended in this paper. It is shown that rectifier-inverter drives equipped with small (film) DC-link capacitors may need active stabilization. The impact of limited bandwidth and switching frequency in the inverter-motor current control loop is considered. Recommendations for selection of the DC-link capacitor, the switching frequency, and the DC-link stabilization control law in relation to each other are given. The control law is incorporated in a previously proposed current controller, which is designed for good voltage sag ride-through capability