New method for scheduling hydrothermal systems with identical units

Solution oscillation caused by identical units when using Lagrangian relaxation-based algorithm for hydro-thermal scheduling is analyzed. The homogenous oscillation issue is studied through an example. A penalty term is introduced to the Lagrangian and a surrogate subgradient algorithm is used to update the multipliers. Since the homogeneous subproblems are not solved simultaneously, the oscillation can be avoided or at least alleviated. Numerical testing for the example and a short-term generation scheduling problem with two groups of identical units demonstrates that constraint violation of the dual solution and solution oscillation are greatly reduced, and the final feasible schedule is significantly improved.