Fault-Tolerant Strategy of Four-Phase Full-Leg for Active Magnetic Bearing in Case of Open Circuit Fault of Switching Device

Open circuit fault of power semielectronics switching devices is a main reason for the failure of active magnetic bearing (AMB) system. A fault-tolerant control strategy for four-phase full-leg is proposed to guarantee the safe and reliable operation of AMB under the high-speed rotation in case of open circuit fault of switching device. Firstly, it's analyzed that two modes of four-phase full-bridge have the same electromagnetic force and control effect on the AMB base on the working principle of four-phase four-bridge, that feature could be used to design fault-tolerance of power amplifier. Then the condition for judging open-circuit fault is given based on differential current control, and the corresponding fault-tolerant control strategy is devised, so that when the open-circuit fault occurred to the switching devices of normal mode, the fault would be detected in a few hundred microseconds, then four-phase full-leg would immediately switch to the redundant mode to work to achieve the equipment didn't stop. Finally, the simulation and experimental results show that both fault detection time and displacement fluctuation range guarantee the suspension of AMB in the transition process, which prove the feasibility of the fault-tolerant control strategy for four-phase full-leg. © 2022, Electrical Technology Press Co. Ltd. All right reserved.