Research On Novel Flux Linkage Estimation Thechnology Of Variable Flux Memory Machines

Permanent magnet synchronous machines(PMSM)are widely used in renewable energy electric vehicles due to the merits of simple structure,high efficiency and high power density.Nevertheless,the problem of non-adjustable PM flux results in a limited speed range.Variable flux memory machines(VFMM)can adjust PM magnetization state(MS)by applying a transient current pulse,extending the speed range significantly.In this thesis,the flux estimation thechniques for VFMM are studied.Based the characteristics of VFMM,such as large PM flux range and complicated inductance variation,the existing flux observers are comparatively investigated,and a modified current integrator error compensation(MCIEC)flux observer is proposed.The main work of this thesis includes the following aspects:(1)The recent development of flux estimation thechniques for PMSM and VFMM is reviewed.Due to the advantages of robust to parameters variation and disturbance,the class of method based on state observer is choosen for VFMM system.(2)The error analysis of model based direct calculation method is carried out,and some disadvantages such as parameters sensitivity and error accumulation are highlighted.The error analysis and applicability of direct calculation method in VFMM are conducted.(3)The error compensation based flux observer for VFMM system is studied.The methematic model of gopinath style flux observer(GSFO)is divrived,and the estimation error caused by inductance and PM flux variations is studied.Based on GSFO,two kinds of error compensation method,CIEC and stator current observer(SCO),are comparied,and a MCIEC method is proposed according to the CIEC method.The transfer function analysis proves that the proposed method can effectively suppress the error caused by inductance and PM flux-linkage parameters,meeting the specific needs of VFMM system.(4)The discrete simulation model of VFMM system is built in MATLAB/Simulink environment,and the direct calculation method,GSFO,error compensation method and proposed MCIEC method are all modeled,which verifies that the proposed method has better accuracy during steady-state,load variation and magnetization period.(5)The hardware circuit and software system are designed based on STM32 core.Several kinds of flux observers are tested by experiment.The GSFO and MCIEC are compared in terms of PM parameter sensitivity and magnetization dynamics,and the experimental results prove that the MCIEC structure has better applicability to VFMM system.The research work of this thesis provides a theoretical and technical basis for the in-depth research and engineering application of flux linkage estimation technology.