Research On The Improvement Of The Simulation Accuracy Of AC-DC Power System Based On RTDS

The HVDC systems are increasingly installed in modern power systems. The dynamic characteristics of the AC-DC power system can be reflected accurately by Real-Time Digital Simulator (RTDS) with the external actual DC control and protection devices, so the RTDS becomes an important simulation method to ensure the utilities of the project wil work well after they are set in the station, and the simulation accuracy of RTDS is urgently concerned. In this paper, a typical±500kV AC-DC real-time simulation system is established, the real DC line faults have been successfully simulated, then the simulation accuracy of RTDS is researched.The general principle of AC-DC power system simulation on RTDS is proposed in this paper. The key problems in modelling are introduced, such as dynamic equivalent of AC power system and choice of simulation time step. And some measures are proposed to improve RTDS models. The model of Three Gorges-Shanghai±500 kV DC Transmission Project is established.The performance of HVDC system depends on the parameters of control system, and usually PI controllers have been used to adjust system to fulfill desired objectives. This paper introduces the Simplex Algorithm and its application in RTDS. And the PI parameters of constant current (CC) control at the rectifier and the constant extinction-angle control at the inverter for Three Gorges-Shanghai±500 kV DC Transmission Project are optmized.The real faults of Three Gorges-Shanghai±500 kV DC Transmission Project have been successfully simulated by use of the simulation model of RTDS. The simulation results are compared against the field fault recordings.The reseaons of differences are analyzed, and some improvement measures are put forward to improve the simulation accuracy.