Research On Permanent Magnet Synchronous Motor Direct Torque Control Fault Tolerant Strategy

Permanent magnet synchronous motor (PMSM) has simple structure, small size, highflux density, large torque inertia ratio and many other advantages. Now with the improvingneed for high precision, high dynamic performance and small size of speed control system,the application field of PMSM is becoming more and more widely.Power electronic device can become heat and warming because of the loss of power,which leads to shorten life and even burn down the device, thus power electronic devicebecomes the most frequent site of failure. Once fault occurs, the fault will cause the wholemotor drive system is in dangerous state and cause downtime or even catastrophic accidents.In order to make motor drive system can continue to run safely and stably after a failure, thedrive system needs to be improved, so as to improves motor drive system’s operationperformance. So the research on PMSM with fault tolerance has a very important theoreticalvalue and practical significance.Taking PMSM direct torque control (DTC) as a research object, this dissertation studiesthe fault tolerant control for a phase winding open circuit and inverteran an arm power deviceopen circui. First, the mixed logic dynamic model of PMSM is built by using mixed logicalthought. Second, the normal operation PMSM DTC system is designed. The result shows thatthis system has a good dynamic performance and the anti disturbance capability of speed isvery strong when load torque changes, but torque and flux ripples are too big. Third, PMSMDTC fault tolerant strategy is proposed on the basis of fault tolerant inverter. In this strategy,fault detection and isolation module is designed by using current locus method, which hassimple structure and easy to implement. After fault occurs, the system run normally, responsequickly and fault tolerant performance can meet the requirements, but torque and flux ripplesare too big. Last, in order to improve performance of DTC fault tolerance strategy, a PMSMfuzzy DTC fault tolerance strategy based on adaptive integrator is designed. In the newsystem, an adaptive integrator is put forward to observer the flux instead of pure integrator.This new system corrects phase distortion and improves observation precision of flux. At thesame time, a fuzzy voltage vector controller is put forward to replace the traditional voltagevector controller by using fuzzy control method. This controller refinements flux and torquedeviations. The simulation result shows that new system effectively suppress ripples, so thisnew system improves the static and steady state.