When large-scale conventional HVDC transmit electric power in the high renewable energy penetration area, HVDC transmission system fault can easily cause transient overvoltage problems at sending-end. In this paper, with grid-forming inverter and high-performance control system, a new device based on energy synchronous conversion technology is designed to suppress the transient overvoltage. By properly configuring the device, it can not only improve the stability of the power system, but also suppress the transient overvoltage after HVDC fault and solve the problem of large-scale disconnection of renewable energy caused by HVDC fault. Finally, the simulation analysis of Qingyu HVDC sending-end grid and the performance test of the device verify its accuracy and effectiveness.