Hybrid Electromagnetic Unified Power Flow Controller: A Novel Flexible and Effective Approach to Control Power Flow

The commercial application of conventional unified power flow controllers (UPFCs) is rare, because of their high installation and operational costs. Sen proposed the “Sen” transformer (ST) that provides similar power flow control functionality as UPFCs, using only a multiwinding transformer and tap changers. However, the ST has output error and response speed issues, due to the discrete characteristics of tap changers. A novel hybrid electromagnetic unified power flow controller (HEUPFC) is proposed. The HEUPFC is composed of a larger capacity ST and a smaller capacity UPFC. The HEUPFC provides economy, flexibility, high reliability, and continuously variable amplitude and phase angle output. The minimum ratio of the magnitude of the series injected voltage from the UPFC is deduced for several center tap cases. The proposed HEUPFC can control the bulk ST power flow with coarse step changes and precise UPFC control, and precisely control active and reactive power flow. Simulation and experimental results were used to verify the practicability of the HEUPFC.