A generation scheduling model for joint optimization of conventional energy and renewable energy is proposed

in which the high-voltage direct-current(HVDC)tie-line power operation with a stair-like power curve and the inter-regional coordination of a sending system and multiple receiving power systems are taken into consideration. A mathematical model for the HVDC tie-line power operation is developed

which meets various constraints on tie-line power adjustment

including the stair-like HVDC power curve constraint

the constraint that no adjustment in the opposite direction of the tie-line power shall be made within an adjacent time interval

the stable operation duration constraint on tie-line power

and the constant daily electricity constraint. The model not only makes full use of the flexible adjustment characteristics of HVDC tie-line power

but also avoids the frequent conversion of HVDC converter equipment

making the HVDC tie-line schedule more executable. The model can deal with multiple HVDC transmission channels between multiple inter-regional interconnected power grids

as well as the system load complementarity and the renewable energy acceptance between sending and receiving power systems. Then coordinated scheduling between sending and receiving power systems can be achieved

renewable energy accommodation in a wider area promoted. Case studies are conducted based on the actual operational data of an inter-regional interconnected power grid in China. The results have validated the effectiveness of the model proposed.