New systematic method for obtaining feasible solutions to unit commitment problem considering ramp rate constraints

A new systematic method based on the necessary and sufficient condition for a unit commitment to be feasible is proposed for solving the unit commitment problem with ramp rate constraints. Once a dual unit commitment obtained within Lagrangian relaxation framework is judged by this feasibility condition to be infeasible, reselect the dynamic planning route with non ramp rate constraints by using the information of the dual solution, i.e. readjusting their sequence of start-stop such that the feasibility condition mentioned above is satisfied. Once a feasible unit commitment is obtained, economic dispatch can then be solved to readjust the generation levels to obtain a feasible solution. Being different from the previous method, this method considers the re-dispatch of generation levels of units with ramp rate constraints in solving the economic dispatch, hence the possibility of obtaining a feasible solution is enhanced and the quality of the feasible solution is also improved. Two generation scheduling systems with 5 or 10 units are tested. The result shows that the new method is very efficient and effective.