A many-objective optimization strategy for unified optimal operation of pumped storage hydropower station under multiple load rejection conditions

Pumped storage hydropower stations are essential for the efficient integration of renewable energy, while frequent conditions conversion make them prone to fall into terrible transient processes, posing a stiff challenge for sustaining stable operation. Especially when simultaneous or successive load rejection happens, the hydro-dynamic pressure can be tremendous because of hydraulic interference and outrageous flow changes. Re-searchers have actively pursued for optimal control under extreme conditions, while their concern is solely on a specific condition. The circumstance may happen that operation strategy admirable for certain condition is generally inappropriate or even highly hazardous for another. Following this idea, a many-objective optimization strategy for unified optimal operation is proposed, which intends to pinpoint the optimal strategy of turbine mode suitable for multiple load rejection conditions with marvelous transient process performance. In the first place, the model foundation of pumped storage hydropower stations characterized by one-tunnel-two-units is primarily established, which incorporates logarithmic curve projection for precise emulation on pump-turbines. Meanwhile, a novel constrained many-objective optimization strategy is proposed as optimization basis, which possesses distinguished exploration and exploitation attributes taking the merit of reference direction and epsilon-constraint. The effect analysis of operation scheme is conducted for a preliminary understanding of stability characteristic and dynamic quality. The calculation example applied to actual case shows that, compared with other state-of-art counterparts, the proposed many-objective optimization algorithm effectively harmony the contradictory targets under multiple load rejections, and satisfactory performance can be obtained with existence of adequate safety margin disregarding the variation of operation parameters. These results demonstrated the effectiveness and applicability of the proposed strategy for the insurance of stable operation.