An Adaptive Control for Switching Power Amplifier of AMB

Switching power amplifier is an essential part for active magnetic bearings (AMBs). Proportional control method is widely used in AMB's switching power amplifiers for it has many advantages. The gain of the proportional controller will affect the dynamic response and steady-state response of the system and lead to nonlinear behavior of the system. The nonlinear phenomenon of switching power amplifier will lead to the increase in current ripple and harmonic, and even damage the switching elements. Thus, when choosing the gain of the proportional controller, we need to take into account the response effect of the system and the nonlinear phenomenon. During AMB operation, the equivalent inductance of the coil will change as the position of the rotor changes. This will also complicate the switching power amplifier control, which may make the system's nonlinearity more serious. To bridge this gap, this article analyzes the nonlinear phenomenon of the proportional control of the AMB's switching power amplifier and proposes an adaptive control method considering the rotor's position. This method can use the optimal proportional control gain according to the change in the equivalent inductance, and the nonlinear phenomenon can be avoided. The control method has been verified by simulation and experiments.