Research On Fault-tolerant Control Of Multi-phase Induction Motor Under Open-phase Fault Conditions

With the development of digital control technology,multi-phase motor drive system has been realized.Multi-phase motor is suitable for electric vehicle,marine propulsion and other occasions with high power and high reliability due to its phase redundancy characteristic.In order to improve the performance of multi-phase motor under open-phase fault,appropriate fault-tolerant strategy should be adopted.In general,the normal phase winding symmetrical to the open phase can be disconnected to obtain stable torque,but the output torque and power decrease greatly;or the fault-tolerant current strategy based on vector control and current closed-loop control is adopted.Constant voltage frequency ratio(V/F)control without current closed-loop is widely used in fan,water pump and other occasions with low dynamic response requirements.In this paper,the voltage compensation fault-tolerant control strategies of multi-phase induction motor under open-phase operation are studied for such applications.Firstly,the mathematical models of multi-phase induction motor in natural coordinate system,stationary coordinate system and synchronous rotating coordinate system are established respectively,and the mathematical model of multi-phase motor in open-phase operation is analyzed.Secondly,based on the non-reduced order modeling method,asimulation model of open-phase fault of multi-phase induction motor is proposed.Do not change the mathematical model of the motor under normal operation,and simulate the open-phase fault conditions by solving the counter electromotive force of fault phase as the input voltage of the phase to make the fault phase current of the motor zero,to simulate the motor open-phase fault condition.Based on Matlab/Simulink software modeling and simulation,and using finite element simulation software Ansoft for comparative verification.Then,taking nine phase induction motor as the research object,the change part of the residual phase and reduce the MMF distortion fault-tolerant voltage strategies based on V/F control are proposed.The first fault-tolerant voltage strategy is based on the stator voltage equation of induction motor to compensate the leakage resistance and pressure drop of part of the residual phase voltage;the second fault tolerant strategy method is proposed from the perspective of reducing the shape distortion of magnetomotive force,the current fluctuation of dq axis is filtered out by high pass filter,and the residual compensation voltage of each phase is calculated.Based on Matlab/Simulink software simulation,two fault tolerance strategies are analyzed and studied.Finally,the experimental platform of nine-phase induction motor speed control system is designed,and two fault-tolerant voltage control strategies are verified by experiments.The results show that the proposed fault-tolerant voltage control strategy of multi-phase induction motor can reduce the torque ripple by50%?70% theoretically,effectively improve the performance of the motor under open-phase fault,and the control method is simple,which has great engineering application value.