Abstract
The doubly-fed variable speed pumped storage unit is a storage system suitable for joint operation with renewable energy sources to smooth the imbalance between renewable energy supply and electricity demand. However, its working principle and operation control are more complex than those of constant speed pumped storage. In this study, a nonlinear model of doubly-fed variable speed pumped storage units (VSPSUs) considering nonlinear characteristics of the head loss is established. The study finds that a supercritical Hopf bifurcation occurs in the system, and the area enclosed by the lower side of the bifurcation line and the coordinate axis is the stability domain of the system. The active power step perturbation from −0.3 to 0.3 will gradually reduce the area of the stability domain and narrow the adjustable range of the control parameters. In addition, the sensitivity of the model full state variables and the primary and secondary relationships to the changes of subsystem parameters is analyzed systematically using the trajectory sensitivity. It is found that there is a large difference in the sensitivity of different state variables to the parameters. The state variables are much more sensitive to the transfer coefficient of hydraulic turbine torque to guide vane opening, the unit inertia time constant, and the controller proportional gain change than other parameters, which are defined as highly sensitive parameters. The receiver response time constant and the turbine flow-to-head transfer coefficient are the corresponding low-sensitivity parameters.
Highlights
As power system operators pursue low-carbon investments and long-term energy sustainability, large-scale development and a high proportion of variable renewable energy (VRE) access in the power system will become inevitable in the coming decades
To manage the long-term imbalance between VRE supply and electricity demand, scholars have investigated solutions to smooth the imbalance between VRE supply and electricity demand and evaluated their role in deep decarbonization of power generation using advanced power system investment and operation models
Pumped storage units (PSUs), which use both upstream and downstream reservoirs for energy conversion and storage, are currently large-scale energy storage systems that are widely used around the world [5]
Summary
As power system operators pursue low-carbon investments and long-term energy sustainability, large-scale development and a high proportion of variable renewable energy (VRE) access in the power system will become inevitable in the coming decades. To manage the long-term imbalance between VRE supply and electricity demand, scholars have investigated solutions to smooth the imbalance between VRE supply and electricity demand and evaluated their role in deep decarbonization of power generation using advanced power system investment and operation models. These systems include nuclear power plants and natural gas plants equipped with carbon capture and storage, flexible demand, battery energy storage, and long-term storage technologies [2,3,4]. PSUs as energy storage devices are well suitable for combined operation with renewable energy in hybrid energy power systems [7]
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