Multi-converter FACTS devices: the generalized unified power flow controller (GUPFC)

This paper introduces the new concept of multi-converter (three or more) voltage-sourced-converter (VSC) based FACTS devices as well as DC "control sub-networks". A control subnetwork is defined as a multi-terminal DC transmission system utilizing a number of series and shunt converters connected together and embedded in the AC power system for ultimate control capability. A special case consisting of three converters, namely, the generalized unified power flow controller (GUPFC) is discussed in detail. A fundamental frequency model of the GUPFC and its controls is developed in EMTP and used to demonstrate its performance and capability in a test power system. It is shown that this GUPFC consisting of one shunt converter and two series converters is capable of simultaneously controlling five power system quantities, i.e., the bus voltage at a substation and the real and reactive power flows on two lines exiting the substation. Test results are presented indicating the controller performance for reference tracking and in response to a three-phase fault on the system.