Optimization and decision making of guide vane closing law for pumped storage hydropower system to improve adaptability under complex conditions

The pumped storage hydropower system (PSHS) is considered a high-quality peaking and frequency regulation energy source due to its operational flexibility and fast response. However, its frequent regulation leads to complex operating conditions with potential harm to the stability of the system. This paper focuses on analyzing and improving the adaptability of guide vane closing law under complex conditions. This is obtained by proposing a refined numerical model of PSHS considering non-linear factors and analyzing the effects of the guide vane closing law and initial operating conditions on the load rejection. The results revealed that a suitable two-stage guide vane closing law effectively reduces the risk of load rejection. In addition, when the initial load of two units is different, it is beneficial to improve the load rejection characteristics when the unit with the smaller load rejects the load first. Finally, three groups of parameters for the optimal guide vane closing law (the Pareto solution sets) are obtained by multi-objective sparrow search algorithm (MOSSA) under the rated, maximum water head, and maximum rotational speed conditions. The obtained Pareto solution and the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) are used for scoring the solutions and obtain an optimal suitable for complex operating conditions. The water head and rotational speed are reduced by an average of 7.76 % and 3.74 % for the different operating conditions compared to the model validation results, respectively. These results provide a theoretical basis for the selection of the optimal guide vane closing laws and improve the safety during load rejection under complex practical operating conditions.