Voltage sag compensation using two three-phase voltage-fed PWM converters

Voltage sag compensation using two three-phase voltage fed PWM converters is presented. This is new approach to mitigate the voltage sags without using special energy storage devices or power transformers. In the normal incident, the load is fed the power from utility supply via main static transfer switch. When voltage sag is occurred, the main static transfer switch is opened and the auxiliary static transfer switch is closed respectively to feed the power from two three-phase voltage-fed PWM converters into the load instead of faulted utility supply. The operation under 4 conditions of voltage sag of 7.5-kW voltage sag compensator using two three-phase voltage-fed PWM converters is verified by simulation using MATLAB/Simulink. It can be seen that the load received continuous power during voltage sags, the transition from utility supply to two three-phase voltage-fed PWM converters is almost seamless, and the synchrony between utility supply and two three-phase voltage-fed PWM converters is correct. Moreover, utility supply current is kept to be sine wave during sag occurrences and line power factor is also maintained nearly unity.