Cooperative Rotor Position Estimation of Active Magnetic Bearings in Flywheel energy storage system with Unsaturated Magnetic Bias

A strategy of cooperative position estimation is proposed based on the differential control mode of active magnetic bearing (AMB). Given unsaturated magnetic bias, one of the opposing pole pairs must be unsaturated. The unsaturated poles could be tracked by the control current polarity. The position estimation from the unsaturated poles is always chosen as system feedback. Basic theory of unsaturated magnetic bias is discussed and the experimental method of measuring the maximum value of unsaturated current bias is presented. This cooperative position estimation is tested in the 4-DOF AMBs system. Static and dynamic suspension experiments are held to prove the feasibility of this method. Experimental results show that, the self-sensing AMBs system using this strategy exhibits stronger rejection to magnetic saturation. And this strategy proves the performance of force disturbance and increases system stability.