An UPFC (Unified Power Flow Controller) is a FACTS (Flexible AC Transmission System) device, which consists of two VSCs (Voltage-Sourced Converters). The VSCs are interconnected with each other on their DC sides and connected with the AC system via a shunt and a series transformer (booster transformer). It is possible to control the active and the reactive power flow on the AC side by means of the series connected VSC of the UPFC. Attached an example for load flow calculation and dynamic RMS simulation.