Optimization model for the short-term joint operation of a grid-connected wind-photovoltaic-hydro hybrid energy system with cascade hydropower plants

•A practical coordination mode of wind, photovoltaic and hydropower is proposed.•A successive mixed integer linear programming model is developed.•Multiple uncertainties of wind and photovoltaic power are considered.•Coordinated operation increases the generation profits and power output stability. Integrating abundant wind and photovoltaic power into large-capacity hydropower plants is an important way for China to promote the consumption of renewable energy on a large scale. This paper establishes a novel coordination mode for a large-scale hybrid energy system including wind, photovoltaic and cascade hydropower plants. Scenario analysis based on Latin hypercube sampling and k-means is used to model the total forecast errors of power output for wind and photovoltaic plants. In order to deal with the imbalanced cost caused by the deviation between the actual power output and the submitted schedule and increase the expected profit, a wind-photovoltaic-cascade hydropower plants coordinated operation model is established. Ecological flow demand for cascade hydropower plants operation is also considered to meet the comprehensive utilization demand of reservoirs. Through several linearization methods and successive approximation technique, the original model is transformed into a successive mixed integer linear programming model. The real-world case studies show that the coordinated operation of the hybrid system can smooth the power output fluctuation and improve the controllability of wind and PV power output. Moreover, compared with the uncoordinated operation, the total expected profit from the coordinated operation increases by 4.66%. Through sensitivity analysis, the influences of penalty factors, electricity price mechanism and ecological flow on the overall performance of the hybrid system are evaluated.