| Permanent magnet synchronous motor(PMSM)has been widely used in many fields thanks to its simple structure,high power factor and high efficiency.Compared with the vector control technology,direct torque control(DTC)aims at controlling the torque directly,which avoids the complex coordinate transformation and makes the control structure much simpler,resulting in a high-performance of dynamic operation as well as steady-state operation.This thesis will take the PMSM DTC system as the research object,to further simplify the control structure and improve control performance.The mathematical models of PMSM are introduced in several coordinate systems.The traditional method of DTC in the PMSM is theoretically analyzed,and simulation and experimental verification are carried out.Considering the structural characteristics of PMSM,this thesis analyzes the non-decoupling characteristic of traditional DTC stator flux and torque double closed-loop control structure and points out that the traditional double-loop control structure is not the best structure of torque control.Then,this thesis presents a PMSM non-flux-linkage closed-loop DTC method.The non-flux-linkage closed-loop DTC method directly takes torque as the priority control target,no longer considering the requirement of constant stator flux amplitude,in order to achieve fast and accurate PMSM torque control.Simulation and the experimental results verify that non-flux-linkage closed-loop DTC method is correct and feasible.The non-flux-linkage closed-loop DTC method simplifies the control structure of the traditional DTC method,eliminating the flux linkage control loop,with faster and more accurate torque control.Meanwhile,the non-flux-linkage closed-loop DTC method further improves the PMSM DTC theory system.An experiment platform of PMSM is designed,based on TI DSP TMS320F28335.The experiments with different control methods are conducted on this platform.The results show that the platform is effective and reliable. |
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