Julie Thomas, Selvaraj A
AC Adjustable Speed Drives (ASD’s) have become very popular variable speed control devices used in industrial, commercial and some residential applications. Modern solid state induction motor drives are highly sensitive to voltage sags. A voltage Sag is defined as a momentary decrease in the rms voltage, with a duration ranging from half a cycle up to 50 cycles. The problem of voltage sags is of important because it can cause loss of production and revenue due to the tripping of equipment sensitive to voltage variations. This paper presents a method for mitigating the voltage sag through SWISS rectifier (SR) in the front end and Z-source inverter in the back end. The SR is a buck type AC to DC converter which provides more controlled voltage at the DC- link. This rectified output DC voltage fed to the Impedance source network of the ZSI. The impedance network is used to buck or boost the input voltage depends upon the boosting factor. Simulations are performed for the proposed model. The simulation results of DC-link voltage and speed of the motor are analyzed and is compared with the conventional methods.
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