Short-Term Hydro Scheduling Considering Multiple Units Sharing a Common Tunnel and Crossing Vibration Zones Constraints

For low construction cost, the hydropower plant with multiple units sharing a common tunnel (HPMUST) has been widely used, which plays an essential role in the short-term scheduling of power systems worldwide. Thus, accurately solving short-term scheduling of HPMUST is important. Because water head loss of a tunnel is related to the discharge of multiple units, the existing methods noted in the literature tend to decompose this problem to find a near-optimal solution, instead of solving it integrally. With increasing requirements of short-term scheduling, this solution cannot meet practical operation requirements, and it becomes imperative to obtain high quality solutions by solving the original problem. For this purpose, this paper develops a mixed integer linear programming (MILP) model for short-term scheduling of HPMUST and proposes a gross water head-based iterative methodology to directly solve it. The MILP model takes account of not only head variations, common tunnel water head loss of multiple units, and water consumption during startup and shutdown of units, but also water consumption of crossing the vibration zone. Moreover, the paper proposes a novel generic linear programming formulation to model crossing the vibration zone, which can achieve a remarkable decline in number of times of crossing the vibration zone. The numerical results show that, compared with the average output model (AOM) and the real operation, the developed model and solution method can efficiently reduce water consumption of power generation within an acceptable time and meet practical operation requirements.