This paper examines long-term optimal operation using dynamic programming for a large hydropower system of 10 reservoirs in Northeast China. Besides considering flow and hydraulic head, the optimization explicitly includes time-varying electricity market prices to maximize benefit.Two techniques are used to reduce the 'curse of dimensionality' of dynamic programming with many reservoirs. Discrete differential dynamic programming (DDDP) reduces the search space and computer memory needed. Object-oriented programming (OOP) and the ability to dynamically allocate and release memory with the Cþþ language greatly reduces the cumulative effect of computer memory for solving multi-dimensional dynamic programming models. The case study shows that the model can reduce the 'curse of dimensionality' and achieve satisfactory results.

the layout and the characteristics of the cascade reservoirs and hydropower stations in the upper reaches of the Yellow River, determine that cascade hydropower stations scheduling must be operated based on the joint operation between Longyangxia and Liujiaxia cascade hydropower stations, especially on flood control operation. This paper deeply analyzes design flood storage area of the Liujiaxia composition and Longyangxia-Liujiaxia joint flood regulating principle on the basis of analyzing and calculating each ten-day design flood of the Tangnaihai above main stream and the intervals. Therefore, the reasonable combination of interval flood and the process of Longyangxia reservoir flood discharge is confirmed, and thereby, studying Liujiaxia reservoir inflowing design flood under a controlling operation of flood limited water level for a period of ten-day to ensure the safety of Liujiaxia reservoir flood control.

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