TRANSMISSION SERIES POWER-FLOW CONTROL

This paper presents the characteristics of two gate turn-off (GTO) thy ristor voltage-sourced inverter-based series power flow control device s, namely the Series Power Flow Controller (SPFC) and the Unified Powe r Flow Controller (UPFC). These devices represent series extensions of the STATCON, an inverter-based shunt device developed under a tailore d collaboration by EPRI, TVA and the Westinghouse Science and Technolo gy Center, which will soon be placed in service on the TVA 161kV trans mission system for transmission voltage control. Operation of the SPFC and UPFC is illustrated through the use of easily-constructed circle diagrams on the P-Q plane. The circle diagrams provide the transmissio n planning engineer with a simple means to assess the performance of t hese devices on the transmission system. A concluding example illustra tes that the UPFC provides a level of power flow control which is unat tainable with more conventional devices.