Research On Flux Weakening Control Of Variable Flux Memory Machines

Permanent Magnet Synchronous Machine(PMSM)has been widely used in industrial,defense and aerospace fields due to its high efficiency,high power density and high reliability.However,the conventional permanent magnet machine has a limited speed range due to its unregulated air gap magnetic field.The Variable Flux Memory Machine(VFMM)uses a low-coercivity permanent magnet material whose magnetization can be flexibly adjusted by applying a short-time pulse current.Therefore,VFMM is equivalent to adding a degree of freedom to the traditional PMSM,which can further widen the operating range and has almost no flux regulation loss,then can realize global efficient operation.In this paper,the flux-weakening control technology of VFMM is studied.Firstly,it introduces the research progress in the field of memory machine at domestic and abroad,and focuses on the main problems faced by this type of machine in control,including on-line observation of permanent magnet magnetization and torque ripple suppression during flue regulation,overall operating range expansion and global efficiency optimization.In this paper,combined the advantages of pulse modulation characteristic of memory machine,a segmented flux regulation control strategy is proposed.The speed is used as the turning point.Different speed range correspondes to different optimal Magnetization State(MS).The appropriate flux regulation control strategy is adopted while considering d axis current limit in each speed interval.The static flux regulation experiment is carried out using a VFMM prototype designed by the research group to test the flux regulation interval of the machine and the correspondence between the MS and the pulse current.The experimental results show that the prototype can achieve twice flux-weakening operation by pulse current demagnetization.The MATLAB/Simulink model is built and the torque-speed curve of the machine in the i_d constant 0 and flux-weakening control mode is simulated.The simulation process is carried out under the condition that the machine is in its highest and lowest magnetization states respectively.The results show that in both control modes,the machine can expand the operating region by demagnetizing the permanent magnet at the turning point.Finally,the Digital Signal Processor(DSP)28335 chip is used to design the hardware system and the software program is written.The machine test platform is built and the torque-speed curves of the machine at different magnetization states are tested.The flux regulation characteristics of the machine are verified,indicating that the machine can expand the operating range by flux regulation.