In order to support the construction of a new power system

the hydropower function has gradually changed from 'power supply'to power supply flexible regulation'.The traditional day-ahead scheduling method of hydropower cannot cope with the short-term new energy fluctuation of power system because it cannot realize the real-time power balance adjustment of hydropower in power system.To this end

this paper proposes a multi-time scale scheduling strategy for cascade hydropower systems considering source-load collaborative optimization to deeply tap the potential of hydropower flexible regulation.Firstly

based on the characteristics of cascade hydropower operation

the problems existing in its participation in real-time power balance regulation of power system are analyzed from two aspects of power and water quantity.Secondly

the synergistic and complementary mechanism of source-side cascade hydropower and load-side flexible regulation resources is analyzed

and the multi-time scale scheduling framework of source-load of cascade water-wind-fire system is constructed.In the real-time stage

the allowable fluctuation range of water level is introduced to limit the fluctuation range of reservoir water level in the real-time regulation stage.Finally

the original model is transformed into a mixed integer linear programming model by using the linearization method

and the example analysis is carried out in the IEEE39 node system.The results show that compared with the traditional day-ahead scheduling method

the proposed method reduces the system operating cost by 9.3%，increases the wind power consumption by 1.52%，and reduces the system carbon emission by 4.85%.It can help the system to achieve safe

economic and low-carbon operation.