Abstract: The traditional criterion of maximum energy storage increment does not reflect the dispatching objective of a hydropower station, because it ignores the influence of power generation efficiency and uses the average value over a certain period to calculate energy storage increment. This paper first examines the concept of energy efficiency coefficient and uses it to calculate a hydropower station's capacity of utilizing hydropower resources, and improves the traditional criterion of maximum energy storage increment. Then, we adopt a progressive approximation algorithm and the improved criterion to calculate more accurately the energy efficiency coefficient for each hydropower station in a river basin, and construct an improved model of maximum energy storage increment based on this coefficient. Finally, a case study of the Pankou-Xiaoxuan cascade reservoirs in the Du River basin is given. The results show that the improvement is reasonable and effective in increasing the energy storage and power generation benefits of cascade reservoirs. Compared with the existing models, this improved model gives better optimization effect, thus useful to the hydropower developing practices of electricity to water mode.

Key words: electricity to water mode, maximum energy storage increment, optimization criteria, energy efficiency coefficient, progressive approximation