Research On MTPA-based Direct Torque Control Of Five Phase Permanent Magnet Synchronous Motor

With environmental pollution and oil shortages increasingly being serious,the electrification trend of the agricultural equipment is accelerating.When the motor drive system is applied to an electric tractor,it needs large torque,high power density,high reliability,high efficiency and fast dynamic response.Because direct torque control(DTC)has fast dynamic response and the maximum torque per ampere(MTPA)control can increase the efficiency and output torque of the drive system,multi-phase permanent magnet motor drive system using MTPA-DTC strategy can meet these requirements.In this paper,five-phase permanent-magnet synchronous motors(PMSMs)are used as the control objects.Aiming at the disadvantages of traditional MTPA-DTC strategies,a new MTPA strategy based on virtual signal injection is proposed,which can achieve MTPA control without motor parameters.Meanwhile,the dynamic and static performances are unaffected.The new MTPA-DTC strategy retains the advantages of simple structure and robustness of traditional DTC.Simulation and experimental results verify the feasibility of the proposed strategy.The main research content can be summarized as follows:(1)The structure of a five-phase PMSM is outlined,and its mathematical model is established in five-phase natural coordinate system and two-phase stationary coordinate system.Then,the DTC strategy of PMSM is presented.(2)The principles,implementation methods,advantages and disadvantages of the traditional MTPA-DTC strategy are presented.To overcome its poor robustness to motor parameters,a new MTPA-DTC strategy based on virtual signal injection is proposed.To achieve MTPA,sinusoidal signal injection and random signal injection are proposed respectively.Then the two methods are analyzed.(3)The MTPA-DTC simulation model based on virtual signal injection is built in Matlab/Simulink,and simulation analysis is performed to verify the feasibility of the proposed MTPA-DTC strategy.(4)An experimental platform for a five-phase PMSM drive system based on d SPACE is designed.The experiment of MTPA-DTC based on virtual signal injection is completed on this platform,and the feasibility of the proposed control strategy is verified furtherly.