Research on an improved hybrid unified power flow controller

An improved hybrid unified power flow controller (IHUPFC) is developed in this paper to increase the utilization rate of transmission line and enhance the transmission capacity in extra-high voltage (EHV) and ultra-high voltage (UHV) grid. Based on introducing the existing power flow controllers, the advantages of IHUPFC in structure and performance are analyzed. The proposed IHUPFC is composed of an improved phase shift transformer (IPST) and a small capacity UPFC. The proposed IPST has simpler structure, smaller size and larger power flow control area than that of “SEN” transformer. The IHUPFC provides an independent, bidirectional and continuous active and reactive power flow control in the transmission line as UPFC does. The technology of IHUPFC is reliable and cost-effective. Simulation results were used to verify the practicability of IHUPFC.