Abstract
When the pumping operation of pumped storage unit suffers from power outage, the hydraulic transient poses a serious threat to the safe operation of the unit and its pressure pipeline system. For high-head pumped storage power station (PSPS), the water hammer pressure (WHP) and rotational speed rise ratio (RSRR) of each hydraulic unit will be increased during the pump outage condition. In order to limit the fluctuation of rotational speed and WHP in power-off condition, optimizing and choosing a reasonable guide vane closure scheme (GVCS) is an economic and efficient means to improve the dynamic characteristics of pumped storage unit. On the basis of the calculation model of the transition process of single tube-double unit type of a high-head PSPS, an optimization model of GVCS balancing WHP and RSRR objectives is established. Furthermore, the two-stage broken line and three-stage delayed GVCSs are applied to the pump outage condition, and the nondominated sorting genetic algorithm-II (NSGA-II) is introduced to calculate the optimal solution set under different water heads and different closure schemes. For four typical water heads, the multiobjective optimization results of the closure law show that the two-stage broken line law has a better Pareto front under high water head, while the three-stage delayed law has a better performance under low water head. Furthermore, through the results of transition process of typical schemes, the adaptability of GVCS and water head is analyzed. The method proposed in this paper can make the RSRR not more than −0.89, and the three-stage delayed law can even make the RSRR only −0.01. Methods of this paper provide a theoretical basis for optimum guide vane closure mode setting of PSPS.
Highlights
Investment in renewable energy schemes improves economic stability and reduces pollution [1]
From the above four contrast diagrams, it can be seen that the two-stage broken line guide vane closure scheme (GVCS) is better than the three-stage delayed closure scheme in optimizing the water hammer pressure (WHP) and rotational speed rise ratio (RSRR) for Head 1. erefore, the two-stage broken line GVCS is more suitable for the Head 1 under the
To further verify the validity of the model of GVCS, the two-stage broken line GVCS in Head 1 mode and the threestage delayed GVCS in Head 4 mode were taken for simulation. en, the indicator values in the transition process calculation of the schemes with minimum WHP and RSRR were obtained, respectively
Summary
Investment in renewable energy schemes improves economic stability and reduces pollution [1]. Erefore, the larger the growth of renewable energy, the larger the need of PSPS to balance the load variation and increase the network reliability [9]. Another feature is their flexibility to make up for the stochastic of solar and wind power, which is helpful for the multienergy complement [10]. A conventional method to deal with the transient conditions of the pumped storage unit has been to optimize the GVCS. Is would be a serious threat to the safety of the PSPS especially when it is under the pump outage condition, since the RSRR of the unit will increase greatly and lead to the significant change of flow rate, increasing the WHP. A nonoptimal GVCS under extreme conditions causes the WHP and RSRR to rise and exceed the allowable range of design, resulting in unfavorable phenomena such as overspeed of the unit, abnormal vibration, and Mathematical Problems in Engineering asynchronization of the movable guide vanes [13, 14]. is would be a serious threat to the safety of the PSPS especially when it is under the pump outage condition, since the RSRR of the unit will increase greatly and lead to the significant change of flow rate, increasing the WHP. e stable and safe operation of the unit will be affected if no actions are taken
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