Research On SVPWM Over-modulaiton And Flux-weakening Control Strategy For PMSM

PMSM(Permanent Magnet Synchronous Motor)has a large number of advantases such as simple structure,large power density,high efficiency,stable operation and has been increasingly applied in all kinds of electrical control occasions.However,with the acceleration of industrial modernization,more and more higher requirtments are put forward for control systems of PMSM,which are no longer confined to traditional applications,such as the rated conditions and are gradually extended to constant power operation region above the base speed.Overmodulation control and flux-weakening control is effective methods to achieve the above requirements.This paper mainly revolves around a surface permanent magnet synchronous motor(SPMSM).the structure and operation principle of PMSM is analyzed,and its mathematical models in static coordinate and in the dq0 coordinate is presented.Based on those,both the principle of SVPWM flux-weaking and overmodulation control strategy and theirs research status is analyzed in detail.The traditional SVPWM overmodulation control strategies contain the traditional single mode modulation and dual mode modulation.Then the amplitude and total harmonic distortion of fundamental wave and harmonic waves are analyzed.Aimed at the implementation difficulty of traditional dual modes and large harmonics of single modes,a SVPWM over-modulation control strategy based on logical judgement(LG-SVPWM)is put forward,which has a simpler implementation,doesn't need to calculate the holding angle,and harmonic content is relatively small.Through on simulation analysis and experimental verification,the above overmodulation control strategy has been achieved,and simulation and experimental results verify the correctness and the feasibility of those algorithm.Maximum torque per ampere(MTPA)control strategy is studied in this thesis when the SPMSM is under the base speed.By increasing the demagnetization current,the motor can run in the flux-weakening region.Finally,simulation and experimental results show that overmodulation and flux-weakening control strategy based on the demagnetization current can effectively use the DC bus,improve the efficiency and broaden the speed range.