Design and Control of a Novel Four-degree of freedom Bearingless Permanent Magnet Machine for Flywheel Energy Storage System

In this paper, a novel bearingless permanent magnet machine (BPMM) without strong and complex magnetic field coupling, which can limit four degrees-of-freedom (DOFs) independently, is presented for the flywheel energy storage system (FESS). The proposed machine provides suspension force by means of interaction of flux density of permanent magnet rings and winding current. And the model of the proposed machine is derived. Meanwhile, based on the conventional cross feedback control, the modified control scheme with compensation for cross channels is illustrated. Additionally, combining with the machine model and modified cross feedback controller, the simulation is built to demonstrate the effectiveness. The results show smaller fluctuation in steady state, fast response with disturbance and less impact on undisturbed channels by employing the modified control.