Stochastic optimization of a hydro-thermal system including network constraints

The authors describe a methodology for the optimal scheduling of hydrothermal power systems taking into account multiple hydro reservoir characteristics, inflow stochasticity and a transmission network represented by a linearized power flow model. The solution algorithm is based on stochastic dual dynamic programming, which decomposes the multistage problem into several one-stage subproblems. Each subproblem corresponds to a linearized optimal power flow with additional constraints representing the hydro reservoir equations and a piecewise linear approximation of the expected future cost function. Each subproblem is solved by a customized network flow/dual Simplex algorithm which takes advantage of the network characteristics of the hydro reservoirs and of the transmission system. The application of the methodology is illustrated in a case study with a Brazilian system comprising 44 hydroplants, 11 thermal plants, 463 buses, and 834 circuits