A successive approximation approach for short-term cascaded hydro scheduling with variable water flow delay

In cascaded hydro systems, water delay time is a very important factor that requires coordination between upstream and downstream reservoirs. Due to the nonlinear characteristics of the water delay time, modeling and solving short-term cascaded hydro scheduling (STCHS) is a very challenging task. This paper proposes a novel STCHS model with continuous variation of water delay time to describe real-world operations in detail. The proposed model includes a nonlinear function related to water delay time. A successive approximation (SA) approach is developed to address the nonlinearity by iterative calculation, making the problem tractable. The proposed model and method are validated with two-reservoir and ten-reservoir systems. Numerical results demonstrate that the proposed method produces more realistic results than existing methods when dealing with STCHS problems.