Active Magnetic Bearing Control for FESS using Integral Backstepping Controller

Abstract

Active magnetic bearings (AMBs) are a technology that makes flywheel energy storage systems possible. AMBs are used in energy storage systems to suspend the flywheel without physical contact and allow the flywheel to rotate freely at high speeds. High speed FESS are predicted to outperform battery systems in terms of lifetime and en ergy density. All of the components of AMB are characterized by nonlinear behaviour and therefore the entire system is inherently nonlinear. Moreover, these systems are often subjected to model uncertainity, harmonic disturbances, and sensor noises that makes rotor touch the stator. In this thesis, an appropriate control strategy is proposed to handle the nonlinear dynamics of an AMB. In order to achieve this task, integral backstepping control technique with a barrier Lyapunov function are employed to keep the error inside a predefined zone to avoid possible mechanical contact between rotor and stator. The method is based on full-state feedback, for which all three states in the non-linearized AMB model (velocity, position, and current) are used to construct the control law. The stability of the closed-loop system is proven. Disturbance rejection performance tests are performed by considering different psychometric processes in the presence of a static load and sinusoid load disturbance rejection applied to the rotor. In addition, some other optimal control designs based on the linearized model are incorpo rated into the study for comparison. The parameters coefficients of the controllers are tuned by a genetic algorithm (GA). From the simulation result the proposed controller gives a settling time of 0.1935, with RiseTime 3.4847e-05 and ISE, IAE of 3.107e-9, 1.665e-5 respectively. For the disturbance rejection, the proposed controller gives a settling time of 1.108, rise time of 8.66e-7 and peak value of 2.654e-4. The simulation results have shown that, the proposed integral backstepping controller outperformed the existing control systems.