Active Magnetic Bearing system design featuring a predictive current control

Abstract

Active Magnetic Bearing (AMB) technology is becoming attractive for several reasons such as high speed operations, high reliability and vibrations exemption. Moreover, AMB can behave as active vibration dampers and provide a real-time control of the shaft. For all these advantages, AMBs are particularly attractive for high power - high speed applications. These desirable features come at the cost of an increased complexity of the system, which now includes a power electronic converter and a control systemdedicated to the AMBs. This paper focus on the overall system design, from the AMB design, to the power electronic converter design and control, for an AMB featuring Wheatstone bridge winding configuration. The magnetic design has been developed analytically and validated by means of Finite Elements simulation, to generate up to 2kN of axial forces. The power conversion systemis based on three full bridges, one to magnetize the bearing and two to control the axial forces independently on the x and y axes. In order to achieve high bandwidth current control able to generate the desired orthogonal forces, a predictive control strategy has been proposed, for the several advantages it can provides such as fast dynamic response, no need of modulation, easy inclusion of nonlinearities and constraints of the system, possibility of incorporating nested control loops in only one loop and the flexibility to include other system requirements in the controller. The control system has been validated in Matlab/PLECS simulation, including the effect of parameters mismatches in the coils.