Optimization Scheme Research of WFPDL Strategy for Yongren-Funing HVDC Transimission Project Based on RTDS Closed-loop Real-time Simulation

The ±500kV Yunnan Yongren-Funing DC transmission project is the first HVDC project whose starting point and landing point are both in the same province. It is located in a weak AC system, the transmission line is short and the smoothing reactor has a low inductance value. When a short-circuit fault occurs outside the DC line protection zone, the DC line traveling wave protection (WFPDL) is prone to misoperation and does not meet the requirements of protection reliability. This article analyzes and accurately locates the defects of the original WFPDL strategy, and proposes a scientific and reasonable optimization scheme for the threshold of voltage mutation du/dt. After RTDS simulation analysis and verification, it shows that the scheme not only improves the reliability of WFPDL effectively, but also meets the requirements for selectivity, speediness and sensitivity, and does not affect the operation characteristic of voltage mutation protection 27du/dt, which is also related to the threshold of du/dt, all the DC line protections can still cooperate correctly. The optimization scheme is permanently implemented on site, and a number of artificial short-circuit tests have been carried out within and outside the DC line protection zone. The results show that in the transient process of faults, the control and protection system of HVDC, travelling wave fault location devices, stability control devices and 3 STATCOMs of inverter station can all respond correctly, their functions and dynamic performance meet the system requirements.