Abstract
The current research of supporting and transmission system in flywheel energy storage system (FESS) focuses on the low consumption design. However, friction loss is a non-negligible factor in the high-speed but lightweight FESS energy and momentum storage with mechanical-type supporting system. In order to realize the support system without mechanical loss and to maximize the efficiency of the flywheel battery, a permanent magnet biased magnetic bearings (PMBMB) is applied to the FESS with the advantages of low loss, high critical speed, flexible controllability and compact structure. In this frame, the relevant research of three degrees of freedom (3-DOF) PMBMB for a new type FESS is carried out around the working principle, structural composition, coupling characteristics analysis, mathematical model, and structural design. In order to verify the performance of the 3-DOF PMBMB, the radial force mathematical model and the coupling determination equations of radial two DOF are calculated according to an equivalent magnetic circuit, and radial–axial coupling is analyzed through finite element analysis. Moreover, a control system is presented to solve the control problems in practical applications. The rotor returns to the balanced position in 0.05 s and maintains stable suspension. The displacement fluctuation is approximately 40 μm in the y direction and 30 μm in the x direction. Test results indicate that the dynamic rotor of the proposed flywheel energy storage system with PMBMB has excellent characteristics, such as good start-of-suspension performance and stable suspension characteristics. The proposed research provides the instruction to design and control a low loss support system for FESS.
Highlights
The year 2015 was an extraordinary one for renewable energy, with the largest global capacity additions seen to date [1]
This study focuses on a theory of design and analysis for a three DOF permanent magnet biased magnetic bearings (PMBMB)
The bearing-less motor is a single-winding bearing-less flywheel motor (SWBFM) [29] with the advantages of low loss, high specific power and fault-tolerant performance which is improved from the structure of bearingless switched reluctance motor (BSRM)
Summary
The year 2015 was an extraordinary one for renewable energy, with the largest global capacity additions seen to date [1]. In order to realize the support system without mechanical loss [13, 14], to maximize the efficiency of the flywheel battery [15], permanent magnet biased magnetic bearings (PMBMB) is applied to the FESS with the advantages of low loss, high critical speed [16], flexible controllability and compact structure [17]. The flywheel rotor in FESS is rotated by an electric machine operating as a motor at electric energy storage mode. The bearing-less motor is a single-winding bearing-less flywheel motor (SWBFM) [29] with the advantages of low loss, high specific power and fault-tolerant performance which is improved from the structure of BSRM. Φxm can be produced by radial control coils to strengthen the φm in the x positive direction to balance the magnetic flux in the x negative direction Φm increases in the x negative direction. φxm can be produced by radial control coils to strengthen the φm in the x positive direction to balance the magnetic flux in the x negative direction
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