A High-Speed PMSM Drive Based On Z-source AC-DC-AC Converter

Permanent magnet synchronous motor(PMSM)has been widely studied and applied in electric vehicle,numerical control machine tool,aerospace field and other power occasions because of its high power density,high reliability and low loss.Due to PMSM unique characteristics,this type of motor is perfectly applicable in high-speed drives.The high speed of these motors leads to a significant increases in stator current harmonics,which causes the increase of motor loss and torque ripple and makes the control effect of the system worse and also greatly affects the application of PMSM in the high speed situation.An adjustable DC bus voltage can not only suppresses high-frequency current harmonics,but also reduces the thermal stress of the PMSM,the current stress of the power switch modules and greatly increase the control performance of the system.In order to overcome the limitations of traditional high-speed drive's converters and provide adjustable DC bus voltage with bi-directional power flow,in this thesis a novel AC-DC-AC converter based on Z-Source buck-boost rectifier is introduced.The novel converter topology could obtain DC link voltage higher or lower than power system voltage and also able to adjust it in accordance with the referenced speed of the motor due to the unique features of the impedance Z-Network,called shoot-through state.To increase the buck capability of the proposed converter,and accordingly improve the system's current and speed characteristics at the low speed,an improved topology of the Z-Network is used,which has all the advantages of the traditional one.In addition,the principle and mathematical model of the improved Z-Source are discussed in this thesis.The mathematical model of the PMSM is built,space vector pulse width modulation strategy of the improved Z-Source rectifier is studied and the control algorithm is introduced.Moreover,control system of the high-speed PMSM drive based on the rectifier and inverter is designed.Comparative simulations of the proposed Z-Source and traditional Z-Source topologies are made.The simulation results show that the novel topology has a great improvement in buck capability,provide more stable operating at the low speed,and the current total harmonic distortion of the high-speed PMSM drive with proposed Z-Source AC-DC-AC converter can be significantly reduced as well.At last,the experiments are carried out on a 3kW permanent magnet synchronous motor drive system.The voltage and current characteristics are obtained and analysed,and the validity of the proposed method is verified.