Design Of High-speed Permanent Magnet Brushless DC Machine For Flywheel System Applications

Flywheel energy storage technology has become one of the new energy storage technologies widely paid attention by the academic and engineering due to its advantages of high energy storage density,high instantaneous power,high cycle efficiency,long cycle life,easy installation and maintenance,and no environmental pollution.As the key component to realize the mutual conversion of electric energy and mechanical energy in the flywheel energy storage system,the high-speed machine directly affects the overall energy conversion performance of the flywheel energy storage system.Considering that the high-speed permanent magnet brushless DC machine for flywheel system applications operates in a vacuum environment and the rotor heat dissipation is difficult,this thesis analyzes the rotor eddy current loss of the high-speed permanent magnet brushless DC machine,describes the mechanism of the rotor eddy current loss and proposes the methods to reduce the rotor eddy current loss.Based on the finite element analysis method,the influences of airgap length,slot-opening width,copper shield thickness and sleeve type on rotor eddy current loss are investigated.The three-dimensional temperature field simulation model of the flywheel energy storage system is established.The steady-state temperature field is simulated for three different operating conditions of the flywheel energy storage system,named electric,high-speed standby and power generation condition,and the overall steady-state temperature field distribution of the system is obtained.The simulation results prove that the design of high-speed permanent magnet brushless DC machine for flywheel system applications is reasonable and feasible.