A detailed model for a thyristor-based static transfer switch

Industrial customers often suffer from supply voltage interruptions and sags due to the increase in the utilization of sensitive equipment in the process automation and control. An effective way to improve power quality and reliability of sensitive customers is to use a static transfer switch. This device enables a very fast change in the supply of the customer to an alternate feeder providing adequate power conditioning for several power quality problems, such as voltage sags, swells, and interruptions. In this paper, an analytical model of STS is proposed and its performance is verified using the electromagnetic transients for DC (EMTDC) simulation package. Simulations using this model are performed in order to handle voltage sags based on real measurements on an actual industrial customer's supply voltage. Different phase angles and magnitudes of the two alternate source prefault voltages and different fault instances are considered.