Research On Fault Tolerant Control Strategies For Permanent Magnet Synchronous Motor Drive System

Power switch open circuit and short circuit fault often occurred in the inverter fed PMSMdrive system, which makes motor run under unbalanced power supply. The whole drive systemwill break down when running under fault conditions. For some safety-critical applications, suchas aerospace or marine industry, the catastrophic event may occur especially in severe cases. Inorder to achieve high reliability, it is very necessary to use the inverter with fault tolerantcapability for system reconfiguration and fault tolerant control when fault occurred in theinverter.Aiming at switch open circuit and short circuit fault occurred in the inverter, the four switchthree phase (FSTP) inverter topology with fault tolerant capability is chosen and space vectorpulse width modulation (SVPWM) based on direct torque control strategy is studied in the thesis.The main achievements are given as follows:Firstly, the thesis introduces several kinds of control methods with high performance forPMSM drive system, discusses some common faults occurred in the inverter fed PMSM drivesystem and proposes effective fault tolerant strategies. Considering economy and efficiency,PMSM drive system with FSTP inverter topology together with direct torque control is studied inthis thesis.Secondly, the mathematical model of PMSM is established, and the thesis proposes a newflux observing algorithm and studies the implementation of fault tolerant strategy, including thedefinition of voltage space vector, flux and torque hysteresis control and switch table definition.After analyzing the implementation of direct torque control of six switch three phase (SSTP)inverter system, the thesis redefine the voltage space vector and switch table to implement directtorque control for FSTP inverter topology.Thirdly, SVPWM technology is applied to the traditional direct torque control strategy. Onthe basis of analyzing SVPWM based control algorithm for SSTP inverter topology, the thesisredefine the method for computing the composition of the reference space voltage vector, sectorjudging, the time of switch acting and when acting. In the end, the new SVPWM based controlalgorithm for SSTP inverter fed PMSM drive system is achieved.Finally, the simulation model is built to verify the fault tolerant control theory. The simulation block of SSTP and FSTP inverter together with SVPWM direct torque controlstrategy are built in the same simulation model, and the operating performance of the drivesystem under health and faulty condition can be compared conveniently. The simulation resultsshow that the FSTP inverter fault tolerant topology has good feasibility and high operationperformance.