Abstract:

Flywheel energy storage is widely used in the fields of frequency modulation of power grids due to its outstanding advantages. To further improve the energy density and power density of flywheel energy storage technology, the flywheel energy storage rotors tend to be heavy and high-speed, and magnetic suspension bearings are usually used for axial unloading. The key technology is the design of permanent magnetic bearings with a large carrying capacity, high safety, and low energy loss. The permanent magnetic bearing unloading structure of the double-ring, multi-ring, and Halbach arrays currently being studied have the prominent problem of insufficient strength of the moving magnetic ring material fixedly connected with the rotor under long-term high-speed rotation. Therefore, this paper proposes a single-ring suction type axial permanent magnetic bearing topology. Taking one of the three topological structures as a design example, making full use of magnetic energy and saving materials as the design requirements, the structural parameters of the single-ring suction type axial permanent magnetic bearing are determined based on Kirchhoff's two laws. Under the influence of the flux effect, the magnetic field segmentation method is used to accurately divide the magnetic flux of each part, and the equivalent magnetic circuit model is established. The analytical calculation model of the axial bearing capacity and the axial static stiffness is derived based on the virtual displacement method, and the finite element method is used to verify the established analytical model, and the results are in good agreement, providing a theoretical basis for the design of permanent magnet bearings and subsequent flywheel dynamics analysis.

Key words: flywheel energy storage, axial permanent magnetic bearing, equivalent magnetic circuit model, mathematical analytical model, magnetic flux leakage coefficient