Abstract: Qinghai-Henan UHVDC transmission project, the world's first large-scale use of DC transmission technology to transport hydropower and new energy over a long distance, is important to hydropower and new energy transmission. After it is put into use, new security and stability problems of the power grid will arise. This paper first analyzes the power grid’s stability characteristics after this clean energy DC transmission project put into operation. For the transient problem, the optimal control measures were design and examine to adjust the operation mode and reinforce the grid. Simulations and analysis show that the optimized operation mode and grid reinforcing scheme ensure the transmission of hydropower and clean energy and the DC transmission capability in transition period.

Key words: power system, hydropower DC, high proportion of new energy, stability characteristic, operation optimization, grid reinforcement