Research On Short-term Optimal Operation For Cascade Reservoirs With Foold Control And Power Generation

Cascade reservoir optimal scheduling has received great attention from the beginning of the strategic and centralized development on large river basins in our country.And with the upsurge in hydropower construction and water conservancy,its basic theoretical researches develop rapidly and a mature methodology system has been formed.However,putting the theoretical achievements into engineering practice is the ultimate goal of theoretical research.It is also a huge problem that researchers would face and a troublesome problem that operation and management institutions of reservoir want to solve.Based on the engineering background of cascade reservoirs in Lancang river basin,this paper carries out a related research around the reservoir's two main tasks,which are flood control and power generation.This research intends to improve the applicability of optimal dispatching scheme and provide decision makers with more practical and intuitive reference scheme.The main work is as follows:(1)To improve the accessibility and operability of flood dispatching scheme.In this paper,the model of flood control operation was established to minimize the regulating times of discharge devices.By creating the discharge device opening and closing policy in advance,the efficiency can be further improved.Furthermore,a simple and effective calculating process is designed to solve the model.The application of Gongguoqiao Reservoir shows that the method is able to detail scheduling result from the outflow control to the discharge device control.So this method can improve the applicability of flood dispatching scheme by meeting the need of flood control demand as avoiding the frequent operation of the discharge devices.Since there is no flood-control task between the higher and lower reservoir in Lancang Rive,a multi-level interactive computing pattern is used to solve the optimal operation for cascade reservoirs based on the above-mentioned model.Moreover,due to the excellent regulation of Xiaowan and Nuozhadu,their water-level constraints are set in multi-section to avoid frequent fluctuations in water levels.The case study shows that the flood-control operationcould meet the requirements of flood discharge andthe inflow of each downstream reservoir becomesmore steady.(2)Considering the existent insufficiency of the short-term peak modulation model,a multi-stage minimization of the maximum residual load model is presented for cascade hydropower plants.In this model,the generating unit is treated as a basic computing unit,and it needs satisfy the constraints of ramp rate constraint and start-up/shut-down time.To overcome the uncontrollable results in valley and medium load periods,the principle of progressive optimization is referenced in this model and a number of iterations is used to solve it.In each iteration,a series of measures including equivalent transformation of objective function,net head linearization and unit performance curve linearization are undertaken to convert the original model into a mixed-integer nonlinear programming(MINLP)model.And then the MILP model is calculated by LINGO.The case study shows that given method could satisfy generating units' runningconstrains and meanwhile further decrease the difference between peak load and valley load,which relive the grid's pressure for regulating.Lastly,there have a conclusion of this paper and an outlook for further study.