Torque Predictive Control For Permanent Magnet Synchronous Motor Over Wide Speed Range

Because of its distinctive advantages,such as high efficiency,high power density and light weight,permanent magnet synchronous motor(PMSM)drives have been increasingly applied in a variety of industrial applications which require fast dynamic response and accurate control over wide speed range.For electric vehicle drives fed by interior permanent magnet synchronous motor(IPMSM),maximum torque per ampere is used to improve operating efficiency below the base speed.While above the base speed, to extend speed range,flux weakening control strategy is adopted.By means of the merits that model predictive control can deal with complex constrained problems well,torque predictive control for PMSM drive system over wide speed range is studied.Firstly,traditional control strategies for PMSM is introduced,such as field-oriented control(FOC) and direct torque control(DTC).Then,model predictive control strategy based on PMSM drive systems,is discussed in detail.Current predictive control(CPC) is similar to FOC,which focus to control stator current in dq coordinate and use predictive controller to substitute for inner current controller.Torque predictive control regulates torque directly,but has a better dynamic performance than DTC.By comparing four control methods with each other and considering the operating requirements,a suitable control method for electric vehicle is discussed.Secondly,based on the mathematical derivation of MTPA,the mathematical and physical significance is revealed.Also,the performance of MTPA and id=0 is analyzed.According to the operating characteristic of MTPA,a strategy based on the calculations with machine parameters is verified via simulation.Then,the strategy of MTPA based on high frequency signal injection is emphasized,including the establishment of high frequency coordinate and extraction of optimum MTPA angle.A predictive controller is developed and a MTPA control scheme based on torque predictive algorithm is proposed,it is able to improve the dynamic performance and limit the switching frequency of system.Thirdly,taking into account the utmost voltage and current in inverter,the optimal current operating trajectory is planned and the flux weakening strategy based on vector control is studied.Following the method which is used for MTPA control,a flux weakening control scheme is proposed to improve the stability and flexibity at high speed.The cost function in proposed strategy is designed well to adapt to different speeds and constraints.Thus,the goal that PMSM drive system can operate in a wide speed range is realized.Finally,the feasility and effectiveness of the MTPA control scheme based on torque predictive control in this thesis is verified by experimental results.