Voltage Sag Compensation With Z-Source Inverter Based Dynamic Voltage Restorer

The dynamic voltage restorer has been gaining acceptance as an effective device for voltage sag compensation. The compensation capability of a dynamic voltage restorer (DVR) depends primarily on the maximum voltage injection ability and the amount of stored energy available within the restorer. A new topology based on Z-source inverter for the DVR is proposed in order to enhance the voltage restoration property of the device. Z-source impedance network along with shoot-through capability of the proposed inverter would ensure a constant dc-voltage across the dc-link despite dwindling voltage in the storage devices connected in the dc-link during the process of voltage compensation. Even when the dc-link energy is supplied through a shunt connected auxiliary supply, the voltage rating of the shunt converter, shunt transformer and the dc-link capacitor can be kept smaller with the proposed topology. The proposed converter topology and control methods are validated by simulation and laboratory tests carried out on a proto-type of the restorer