Use of pumped-hydro as peak-load management plant in optimal scheduling of power systems

The system demand, during some intervals of a day, may exceed the available system generation (excluding the pumped-hydro generation). A pumped-hydro plant may then, be used as a peak-load management unit to safeguard the power system by minimizing the power blackout in order to avoid large deviation in system frequency. In this paper, an algorithm is presented to obtain the optimal schedule for hydro, thermal plants including the pumped-hydro unit by proper selection of initial feasible trajectory for the pumped-hydro plant. An additional constraint is introduced to ensure the power balance in each time interval during the perturbation of water storage trajectory. The proposed method decomposes the problem into hydro and thermal subproblems and solves them alternately. The hydro subproblem is solved using a search procedure namely, the local variation method and the thermal subproblem is solved using a judicious combination of participation factors/linear programming method. Optimal scheduling was conducted on a 9-bus system and a 66-bus Utility system. The results obtained for the above two systems demonstrate the effectiveness of the algorithm proposed.