Study On Fault-Tolerant Technology Of Multi-Leg Switched Power Amplifier With Magnetic Bearing

Compared with traditional mechanical bearings,magnetic levitation bearings have the advantages of non-contact,low loss,high precision,low power consumption,adjustable and controllable damping,stiffness,intelligent control,etc.,which are widely used in turbine machinery,flywheel energy storage,aviation,medical,nuclear energy and other fields.In these fields,security and reliability are widely concerned.As a typical mechatronics control system,magnetic levitation bearing system has a complex structure.Once failure occurs,the rotor will fall off in high-speed rotation,which is easy to cause safety accidents.Therefore,how to further improve the safety and reliability during operation is the key to the research of magnetic levitation bearing technology.A switch power amplifier is an important part of magnetic bearings system,but its power electronic components are prone to failure,which is a weak link in the whole system.The switch power amplifier will work in an abnormal state due to device overvoltage breakdown,avalanche breakdown,thermal breakdown,device rupture,welding line rupture,welding line floating and other problems.When it is not serious,it will affect the system performance and increase the voltage and current stress of other devices.When it is serious,the system will collapse.In this paper,aiming at the open circuit fault of the five-phase six-leg switch power amplifier,a fault-tolerant multi-leg switch power amplifier topology is proposed,and the corresponding fault-tolerant control strategy is given.Firstly,the working principle of fault-tolerant power amplifier topology is analyzed.Then,based on the characteristics of current difference,the method to judge open circuit fault is given,and the corresponding fault-tolerant control strategy is adopted to replace redundant bridge leg with faulty bridge leg,so as to achieve the equipment does not stop.Finally,the simulation and experimental results show that the fault-tolerant topology can realize the fast recovery control of each phase current after the occurrence of open circuit fault,which proves the safety and feasibility of the fault-tolerant topology.Then,aiming at the short-circuit fault of five-phase six-leg switch power amplifier,a multi-bridge arm switching power amplifier topology with short-circuit tolerance is proposed.In this topology,a fast fuse is added to the switching power amplifier topology.When a short circuit fault occurs,the fault part is isolated through the fuse.This avoids secondary faults.At the same time,the short circuit fault is changed into an open circuit fault,and the redundant leg is used to replace the faulty leg,which ensures the continuous tracking of the actual current of the coil load to the reference current,and realizes the stable operation of the system under the condition of short circuit fault.Finally,the simulation and experimental results show that the fault tolerant topology can realize the rapid recovery control of each phase current after the occurrence of short circuit fault,which proves the safety and feasibility of the fault tolerant topology.