Space Vector Modulation Strategies for Self-Sensing Three-Phase Radial Active Magnetic Bearings

Abstract

The focus of this study lies on the investigation of the space vector modulation of a self-sensing three-phase radial active magnetic bearing. The determination of the rotor position information is performed by a current slope-based inductance measurement of the actuator coils. Therefore, a special pulse width modulation sequence is applied to the actuator coils by a conventional three-phase inverter. The choice of the modulation type is not unique and provides degrees of freedom for different modulation patterns, which are described in this work. For a self-sensing operation of the bearing, certain constraints of the space vector modulation must be considered. The approach of a variable space vector modulation is investigated to ensure sufficient dynamic in the current control as well as the suitability for a self-sensing operation with an accurate rotor position acquisition. Therefore, different space vector modulation strategies are considered in theory as well as proven in experiments on a radial magnetic bearing prototype. Finally, the performance of the self-sensing space vector modulation method is verified by an external position measurement system.