DC-Link Stabilization and Voltage Sag Ride-Through of Inverter Drives

Previous results concerning instability of the dc link in inverter drives fed from a dc grid or via a rectifier are extended. 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, and 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. This control law is incorporated in a field-weakening (to enhance voltage sag ride-through) current controller for which design recommendations are presented