Abstract
The transient process of pumped storage system (PSS) experienced pump mode, turbine mode and switching mode in pumped outage condition, spanning hump zone and S-shaped region. The conflicting dynamic indicators make it difficult to meet the requirements of the transient process. How to specify optimal operating strategies and improve the reliability of PSS in the pumped outage condition has become a key issue. This problem is addressed in this work based on coordinated multi-objective optimization, and three stages are included: nonlinear modeling, strategy optimization and decision making. A trade-off is embodied in each stage. Firstly, the real-time accurate equivalent circuit model is applied for PSS. The spatiotemporal discrete analysis is presented to enable the trade-off between computing efficiency and model accuracy in stage 1. Then, the neighborhood-search chaotic mutation multi-objective gravitational search algorithm, integrating multiple constraints, is performed to solve the Pareto front. It achieves the trade-off between algorithm convergence and searching diversity in stage 2. Further, fuzzy analytic hierarchy process is innovatively introduced to select the most compatible solution, which comprehensively considers the quantitative and qualitative factors. It accomplishes the trade-off in conflicting objectives and indicators in stage 3. Compared with the on-site operation in pumped outage condition, the maximum reversing speed decreased from 545 rpm to 161.45 rpm, the maximum water pressure of volute can be reduced by 4.55%, and the minimum draft tube pressure can be improved by 6.94%. The coordinated multi-objective optimization provides a novel technical guidance for the safe and stable operation of PSS.
Highlights
The 2050 Energy strategy in Europe and the 13th five-year plan of energy in China [1], [2] are based on a massive development of renewable energy sources
Compared with the on-site operation in pumped outage condition, the maximum reversing speed decreased from 545 rpm to 161.45 rpm, the maximum water pressure of volute can be reduced by 4.55%, and the minimum draft tube pressure can be improved by 6.94%
The best compatible operating strategy is specified by the coordinated multi-objective optimization under pumped outage condition
Summary
The 2050 Energy strategy in Europe and the 13th five-year plan of energy in China [1], [2] are based on a massive development of renewable energy sources. Z. Zhao et al.: Coordinated Multi-Objective Optimization for Multiple Trade-Offs in Pumped Outage Condition of PSS. It is urgent to study the optimal operation strategy of pumped outage condition, improve the dynamic performance of the transient process, and ensure the safety of PSS. Fu et al conducted the improved hybrid grey wolf optimizer - sine cosine algorithm, which possessed good capability for optimal parameters searching and fast convergence [22], [23] Various conditions such as turbine start up [24], [25], load rejection [26], load frequency control [27] have been studied using multi-objective algorithms. Multi-objective optimization algorithms have been applied in PSS operation, the trade-off between convergence and search diversity via multiple constraints and improved iterative mechanism is not carefully considered.
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