Control method for magnetic suspension system of double-electromagnet based on three-level chopper

In the magnetic suspension system, due to the strong nonlinearity of model, it is difficult to achieve the stable suspension of the mover over the entire operating range, and the nonlinear problem of the system has a significant impact on performance. Meanwhile, the traditional two-level chopper can produce a large current ripple, and decrease the current control precision. For single degree of freedom double-electromagnet system, the nonlinear mathematical model of a second-order current suspension was established; In order to reduce the current ripple, the accuracy of the current was improved through three-level control method; Combined with PID controller, the current switching mode based on the feedback linearization of double-electromagnet system was designed, and nonlinear control strategy for single degree of freedom magnetic suspension system was proposed. Simulation and experimental results show that the proposed nonlinear controller can achieve the stable suspension of the mover under different suspension gap.