Abstract
In this paper, the control strategies and their characteristics when applied to the doubly-fed variable-speed pumped storage unit in generating mode and pump mode are discussed. The composition of doubly fed variable-speed pumped storage unit is introduced, and the mathematical model of every component is proposed. Two control strategies of the unit are introduced. One is the power priority control strategy and the other is the speed priority control strategy. Then, the control block diagrams of the two control strategies in the generating mode and the pump mode are established, and the parameters of the unit in each control strategy are designed. The two control strategies are simulated in power generation and pumping conditions. Finally, the conclusion that power priority strategy has a better effect on power control is obtained.
Highlights
With the large-scale development of renewable energy generation, such as wind power and photovoltaic energy [1, 2], the balance of the power system is facing great challenges. e power handling capability of the energy storage system is utilized to achieve balance in the power system, thereby ensuring the safe and stable operation of the power system, which has become an important breakthrough for the current sustainable development of the power grid [3]
It can be used to smooth the output of renewable energy on a large scale [4], which has great significance to solve the problem of safe and stable operation of the power grid caused by the large-scale development of new energy sources such as wind power [5]
Variable-speed pumped-storage unit can better adapt to different operating heads, which can improve the hydraulic performance of pump turbine; reduce vibration, cavitation, and sand wear; expand the operating range; and improve unit stability [7,8,9,10]
Summary
With the large-scale development of renewable energy generation, such as wind power and photovoltaic energy [1, 2], the balance of the power system is facing great challenges. e power handling capability of the energy storage system is utilized to achieve balance in the power system, thereby ensuring the safe and stable operation of the power system, which has become an important breakthrough for the current sustainable development of the power grid [3]. E mathematical model of the pump turbine is generally expressed by the relationship among the mechanical torque Tm, the flow rate Q, the guide vane opening y, the water head H, and the speed n. Considering that this paper mainly analyzes the control characteristics of the pump turbine running near the rated operating condition, the simplified nonlinear model is linearized at the rated operating point and the Laplace domain transformation is carried out to obtain the ideal pump turbine model in the rated operating condition as the following formula: Δpm 1 − Tws. Δy 1 + 0.5Tws (5). In the pump mode, when the unit is operating near the rated operating condition, the guide vane opening is large, and the full characteristic curves of the pump turbine seriously overlap. Pm2 ω2 where subscript 1, 2 indicate working points at two different speeds
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