Mitigation of voltage sag by using AC-AC PWM converter

Abstract: The objective of this research is to develop a novel voltage control scheme that can compensate for voltage sag and swell conditions in three-phase power systems. In order to mitigate power interruptions, this research proposes a scheme called “Voltage Sag Supporter utilizing PWM (Pulse Width Modulation) Switched Autotransformer”. The proposed scheme is able to quickly recognize the voltage sag or swell condition and it can correct the voltage by either boosting the input voltage during voltage sag events or reducing the input voltage during voltage swell events. Among existing methods, the scheme based on the inverter system such as dynamic voltage restorers (DVR) require an inverter, a rectifier, and a step-up down transformer, which makes the system expensive. AC converters can be used for the purpose of the research. However, they consist of two solid-state switches per one phase and include energy storage devices such as reactors and capacitors.. A design is presented for 440v, 50 hz, system.