Research On Open-circuit Fault Tolerant Control Strategies Of Modular Permanent Magnet Synchronous Hub Motor

As the most advanced distributed new energy vehicle driving technology,hub motor technology requires high reliability while ensuring the stability and comfort of vehicle driving.Based on the traditional in-wheel motor which has the working characteristic of high torque at low speed and wide speed range,modular permanent magnet synchronous in-wheel motor adopt unique multi-redundant structure,which ensures the motor able to be highly reliable fault-tolerant operation under fault condition;And the torque output capability of the motor under failure condition is improved effectively.Based on this,this article focuses on the modular permanent magnet synchronous in-wheel hub motor system in the motor windings or inverter bridge arm of fault-tolerant control strategy under the open-circuit fault and the fault tolerance limit for related research.The main content includes the following aspects:First,according to the characteristics of the structure of modular permanent magnet synchronous in-wheel motor,the mathematical model of the motor is derived.Combining the characteristics that each module shares the rotor and can be individually controlled,and in full consideration of the reliability of motor in fault tolerant operation under fault condition,a kind of modular motor control system is proposed.It is based on three-phase four-bridge inverter topology as the main circuit topology structure of common speed loop,each module to current loop independent control.The torque distribution strategy of each sub-module motor and the control strategy of each sub-module system are studied.Secondly,the fault-tolerant control strategy of modular motor system under one phase open circuit fault is studied.A fault-tolerance control strategy based on magnetic potential compensation is proposed to solve the problem of large reduction of output torque caused by the removal of fault module when the number of modular hub motor modules is small.On this basis,the variation of motor current and voltage limit circle in the fault-tolerance control strategy is studied.Based on the principle of equal temperature rise of each module,the torque distribution strategy of the modular motor during fault-tolerant operation is deduced.Then,according to the characteristics that winding can be reconstructed among the modules of modular permanent magnet synchronous in-wheel hub motor,and on the basis of analyzing the various typical open-circuit fault types of the system,the winding refactoring and fault-tolerant control technology is researched when openfault occurs in winding or in the inverter bridge.By this way,the maximum output capacity of the motor in the case of extreme failure is explored.Finally,taking a two-module motor as an example,a modular motor faulttolerant control system experimental platform is constructed.The experimental research on the output characteristic of motor system under normal condition,onephase-open fault case and various kinds of typical open-circuit fault cases.The torque distribution strategy,magnetic potential compensation fault-tolerant control strategy and fault-tolerant control strategy of winding reconstruction are evaluated experimentally.