The Short-term Optimal Scheduling Of Hydro Power Systems With Cascaded Reservoirs

The short-term optimal scheduling of cascade hydro power systems is a mixed programming which has many kinds of constrains. Because of its significant economic impact, the scheduling of hydro power systems has been one of the most important daily activeity for utilityies in the international for a long time. But this problem is a NP-hard mixed programming problem in the filed of math, whose calculation capacity assumes an exponent ascend with the scale of itself. What's more, because of the variability of the objective and the waterpower balance constrains, discreat operation regions and discreat operation states constraints make the solution of the problem become especially difficult. It is early impossible to get the optimal dispatching scheme of the large electric power systems.In this paper, first we reviewed the research achievements by the domestic and international researchers in the field of short-term optimal operation of cascade hydro systems in recent years. And then, the optimal algorithms and their applications in optimal scheduling field are evaluated.On this base, a math model is founded. Then we presents a algorithm based on Lagrangian relaxation for scheduling of the hydro power systems. According to solve the discrete operation states, waterpower coupling between reservoir and some other continuous or discrete constraints in the hydro power systems, then we can make the plain problem become easy, and can get the suboptimal solution with a short time.The key idea of this method is to relax the reservoir level constraints by using Lagrangian multipliers, then making a hydro subproblem unit-wise and stage-wise decomposable. Thereby, to get the optimal operation states of every moment . A modified subgradient algortithm is used to update multipliers in the course of dual problem. In the end, the feasible solution to the hydro power subsystem is obtained by using a network flow algorithm with operating states obtained in the dual solutions.At last, this paper intergrates the practical system data of the Lan Cang River hydro power plants to simulate. Numerical testing result shows that this algorithm can improve the speed of calculation, and the calculation capacity nearly assumes a linear ascend with the scale of the systems. The operation result indicates that this method is efficient and effective for dealing with hydro power systems with caseaded reservoirs.