Research On The Design Method Of Current Loop Of Permanent Magnet Synchronous Motor In High Speed Operation

Permanent magnet synchronous motor(PMSM)is a kind of AC motor whose rotor is excited by permanent magnet and whose stator is basically the same as asynchronous motor.In the PMSM control system,when the motor is running at high speed,the traditional design method of PI current regulator will oscillate and have poor stability.Therefore,it is of great theoretical and practical significance to analyze the characteristics of PMSM at high speed and improve the design of current regulator.Starting from the basic mathematical model of PMSM,this paper analyzes in detail the reasons for the instability of traditional current loop design in high-speed operation,compares the commonly used current loop decoupling control methods,and gives the improved design methods.The main contents are as follows:1)The change of the zero and pole of the current loop transfer function with the speed under the traditional PI control is analyzed in detail.The specific reason of the current loop instability at high speed is given.The root locus method is used to analyze the influence of the current loop design bandwidth on the stability.2)The current decoupling control algorithm is introduced,including the basic principles of feedforward decoupling control,the feedback decoupling control and the diagonal matrix decoupling control,the closed-loop transfer function of three decoupling control strategies is derived,the robustness of the three methods to the decoupling parameters is compared in detail through Bode diagram and simulation,and the advantages and disadvantages of the three methods is pointed out.After comprehensive comparison,the feedback decoupling control with better decoupling and robust performance is taken as the object for further analysis and comparison.3)The stability of PMSM in feedback decoupling control is proved by passivity theory,and the selection range of decoupling parameters satisfying the stability of current loop is deduced.The two degree of freedom PI is used to improve the stability of PMSM.The correctness of the results is verified by theory,simulation and experiment.