In this paper

the structure of back to back VSC-HVDC simultaneous paralleling device and main topological structure of unified power flow controller（UPFC） circuit are analyzed based on the principle that voltage source converter（VSC） can control independently both active and reactive power and a kind of control strategy which realize the control strategy of achieving power system synchronization by power transmission and UPFC functions is proposed.After the simultaneous parallel operation of VSC

the circuit breaker status is used as the feature signal to lockout the converter at both parallel and series side and the transformation of UPFC structure is finished through operation of related electrical equipment

so to change the control strategy of converter and achieve the flow adjustment function.The same device achieves multiple functions under different modes so to improve stability and automation degree of power system and increase the utilization rate of the equipment.The PSCAD/EMTDC simulation is used to verify effectiveness and feasibility of the method.