Optimizing the sizes of wind and photovoltaic plants complementarily operating with cascade hydropower stations: Balancing risk and benefit

The complementary operation of wind, photovoltaic (PV) with hydropower stations has the potential to increase the consumption of renewable energy into the power grid. However, challenges remain to optimize the sizes of wind and photovoltaic plants integrated into the cascade hydropower stations. In this study, a size optimization method is proposed considering the balance of operation risk and benefit. First, a multi-scale nested joint operation model considering long-term, short-term and real-time complementary strategies, notably including the consideration of the forecast uncertainty of wind-PV output, is developed to simulate the operation of the hybrid system. Then, the optimal sizes are determined by a refined evaluation of the operation risk and benefit of the hybrid system. A case study in the Yalong River basin in China reveals that (1) the proposed multi-scale nested joint operation model can ensure not only high long-term power generation benefit, but also high power supply reliability; and (2) an appropriate wind-PV-hydropower size can achieve a higher power generation benefit and a lower load loss risk.