The traditional unified power flow controller（UPFC）， which has the disadvantages of high cost， high loss and large content of harmonics， can not be widely used in the power system. An innovative UPFC， consisting of“Sen” Transformer（ST） and UPFC， is proposed. By controlling traditional on load tap changers， ST produces a series injected voltage whose phase angle can vary 360 degrees discretely， while UPFC produces a series injected voltage whose phase angle can vary 360 degrees continuously by using power electronic switches. These two injected voltages work together to control system power flow. Compared with the traditional UPFC， the hybrid UPFC consists of UPFC with small capacity and can achieve the power flow control range comparable to a UPFC with large capacity. It has the advantages of low cost， small content of harmonics， high efficiency， and good electromagnetic compatibility（EMC）. It solves the cost problem， which has been the most serious obstacle for the wide application of UPFC. The power flow controller has good performance-cost ratio and efficiency to meet today's utility need of independent control of active and reactive power flow on a transmission line.