In the study of the basic principle and work characteristics of interphase power controller (IPC) and static synchronous series compensator (SSSC), a new IPC based SSSC is proposed, in which SSSC is used to replace the phase shifting transformer of the traditional IPC to realize the phase shifting function of inductance branch and capacitance branch. The typical PI control is used to control the voltage source converter by changing the reference voltage and achieve the purpose of changing injected voltage, to change the phase shifting of IPC fast and continuously, thereby controlling the power flow of tie-line flexibly. Compared with conventional IPC, the improved IPC can improve the overvoltage problem, when the relative phase slippage between the power systems on both sides of the tie-line happens. The simulation of Matlab/Simulink verifies the improved IPC can make the power flow of tie-line under control completely and improve the overvoltage problem.