In the interconnected power grid with large-scale renewable energy

the renewable energy can be accommodated in a wider area if the adjustment capability of high-voltage direct-current (HVDC) tie-lines is well utilized. To this end

a new mode of HVDC tie-line operation optimization for increasing the capability of renewable energy accommodation is proposed. In the mode

the tie-line power is viewed as a resource to be optimized. On the premise of meeting all the requirements of the tie-line power adjustment

the renewable energy accommodation in the interconnected power grid can be improved by adjusting the tie-line power. A mathematical model of the HVDC tie-line operation optimization is developed with consideration given to various constraints on tie-line power adjustment

including the daily energy limit

the stair-like tie-line power curve constraint

and the constraint that no adjustment in the opposite direction of the tie-line power shall be made within a short period of time. Case studies are conducted based on the actual operational data of a transregional HVDC transmission channel in China. The results have validated the effectiveness of the mode proposed.