Stochastic optimization of multireservoir operation: The optimal reservoir trajectory approach

The paper presents a new method for determining the optimal operating policy of a power system of several reservoirs in series. The method, called optimal reservoir trajectory (ORT), is based on the following fact: Raising the level of a reservoir feeding a power plant is profitable as long as the gain due to the higher head is greater than the loss due to the additional spillage. There consequently exists a reservoir level at time t at which the expected energy generation is maximized. The task of ORT is to find this level and use it to operate the reservoir. The problem is more complicated for several reservoirs in series since the optimal level of each reservoir is a function of the levels of all the other reservoirs. The paper shows how to solve this problem and presents the results obtained for systems of two, three, and seven reservoirs. The results for the systems of two and three reservoirs are compared with those obtained with stochastic dynamic programming.