System protection related technologies of power grid with high proportion of external ultra HVDC power

Abstract

High power DC blocking causes the high and low frequency problems respectively in the sending and receiving end grid. Considering the Ultra HVDC without direct corresponding power supply construction, the system protection with simple-reliable structure and real-time communication is set up against the frequency risk of sending end grid, and the global optimal strategy and precise control of generator tripping are realized. Covering the wind, hydro and thermal power of whole sending end grid, the system protection with double-layer structure is designed, multi-object oriented real-time communication multiplexing technique is studied, and the calculation method of frequency characteristic and precise generator tripping strategy is proposed. According to the characteristics of different types of power and its influence on the safe operation of power grid, the DC modulation and optimal control strategy of wind, hydro and thermal power are presented. The simulation results show that the system protection is effective and practical.