Study On Three-phase Four-leg For PMSM Control System

The permanent magnet synchronous motor (PMSM) has some advantages, suchas energy density, high efficiency and power factor higher, and its applications arealso expanding. The traditional main circuit topology structure of three-phase three-leg using space-voltage vector pulse width modulation (SVPWM) technology canreduce the winding harmonic currents and meanwhile raise the utilization rate of theDC voltage, so reduce the torque ripple of the motor and broaden the range of speedregulation. But in a-phase fault, the safety and reliability of the system will bedifficult to be maintained by the traditional topology structure, so it is limited inoccasions, where redundancy and reliability are strictly required, such as aviation,aerospace, marine, anti-explosion, etc. Based on this, the paper proposes a kind offault-tolerant function of three-phase four-leg control system. In the three-phase three-leg added a leg and the fourth leg is permanently connected to the neutral point of themachine, and using three dimensional space-voltage vector pulse width modulation(3D-SVPWM) technology, make it drive PMSM has good performancecharacteristics, in single-phase fault or missing cases can also safe and reliablerunning.Firstly, this dissertation narrates the development status and its structure characteristicsof PMSM and builds the mathematical model of PMSM, it also introduces the conventionalvector control mode and studies the theory of3D-SVPWM further deeply. Based on this,employs the vector control strategy of id=0for the research of three-phase four-leg PMSMvector control technology, and proposes zero shaft current compensation strategy, thePMSM system with three closed-loop and four-leg is established, which has thefunction of fault tolerance without any changes of hardware circuit.Then, simulation experiment has been done by Matlab/Simulink software. The simulationmodels of PMSM with neutral point and3D-SVPWM are given, and the vector control modelof three-phase four-leg PMSM is also completely set up, and to verify the performance of the system simulation. Finally the hardware and software part of system are designed, and TIcompany’s TMS320F2812is used as the core control chip, so as to be better to verify thefeasibility of the system.The content studied in this paper has some theoretical and practical value for three-phasefour-leg inverter’s application in PMSM control.