Unified power flow controller operational limit improvement

Increasing the electric power demand and restrictions in the power system expansion due to the high cost and environmental issues urge the utility companies to deploy the devices which will increase the level of the power to be transmitted on the existing transmission lines. Unified Power Flow Controller (UPFC) is the most versatile Flexible AC Transmission System (FACTS) devices which can be used in the transmission level to increase the power transfer capability, operational functionality, and power flow controllability of the power system. This paper analyses a specific type of the UPFC in which the DC-link voltage is not constant but regulated over a range of the values. Many of the existing UPFC installations around the world are of this kind. A new control structure has been proposed to increase the controllability range of this kind of the UPFC. Proposed solution has been validated by the precise PSCAD simulation results.