Abstract: Combining and bundling the wind and photovoltaic (PV) power with a hydropower system is an effective way to promote the consumption of new energy, but it creates a great challenge to the traditional operation modes of pure hydropower system. This paper presents a systematic study on the operation modes of cascade hydropower stations in long-term, one-day ahead and real-time scales, considering the large-scale access of wind and PV power; and evaluates the benefits and risks of complementary operation via examining a case of the hydro-wind-PV power system in the Yalong River basin of China. The results show that in the complementary mode, the water level at large hydropower stations should be lowered more and in advance to increase power generation in dry season and reduce abandoned water volume in flood season. In this mode, the peak regulation ability of the system can be improved, and the daily output process of hydropower should be adjusted to alleviate the competition of export channels. Cascade hydropower can compensate and adjust the unstable wind and PV power at one day ahead and in real-time scales, significantly improving power transmission quality and power supply reliability.

Key words: multi-energy complementary operation, reservoir operation, new energy, operation mode, multi-time scale nesting