Ultrashort-Term Scheduling of Interbasin Cascaded Hydropower Plants to Rapidly Balance the Load Demand

Abstract

The short-term scheduling schemes of cascaded hydropower plants are based on day-ahead hydrological forecasting information. Affected by the accuracy of prediction, real-term hydrological information can considerably vary from previously forecasted values, especially for the power load and local inflows. As a result, short-term scheduling schemes are difficult to apply directly in real-time scheduling. To solve this problem, a rolling optimal hourly operation model for interbasin cascaded hydropower plants is proposed to rapidly balance the load demand. The model is deemed an ultrashort-term model, and it has a short-cycle schedule between short-term and real-time schemes. The basic strategy of solving the model is as follows. First, the day-ahead power load and local inflow information are corrected using a statistical method based on the most recent real-time information. Second, the water delay time, defined as the time between when water is released from upstream reservoirs and arrives at downstream reservoirs, is updated based on the most recent real-time information. Third, a heuristic method is proposed to dynamically update the short-term scheduling scheme over the next few hours. The objective is to minimize the maximum relative deviation between the actual water level of a reservoir at the end of 24 hours and the day-ahead forecasted value. This approach can keep the reservoir water level at the end of 24 hours close to the forecasted value and improve the accuracy of estimating the initial water level the next day. The developed method is applied to solve an ultrashort-term scheduling problem involving the cascaded hydropower plants located in Yunnan Province, China. The results indicate that the proposed model can achieve seamless coupling between shortterm scheduling and real-time scheduling. The proposed method can provide a scientific basis for the realtime dispatching of large-scale hydropower plants and improve the practicality of short-term dispatching schemes. INDEX TERMS Ultrashort term, water delay time, cascaded hydropower plants, real-time scheduling, optimal scheduling. NOMENCLATURE The notations used in the mathematical model of hydropower operation are given as follows. A. SETS M Set of reservoirs or hydropower plants (HPs) M 2 Set of HPs that can increase power generation M 3 Set of HPs that can reduce their power generation The associate editor coordinating the review of this manuscript and approving it for publication was Zhiyi Li .

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