Research On The Predictive Current Control Of Permanent Magnet Synchronous Motor Speed Control System

Permanent magnet synchronous motor(PMSM)has been widely used in many industrial fields such as new energy vehicles,AC servo systems and rail transit because of its high efficiency,high power density and strong reliability.With the increasing processing speed of microprocessors,Finite Control Set Model Predictive Control(FCS-MPC)is an online optimal control algorithm with simple design and easy processing system constraints to have become a research hotspot in the field of PMSM drive.The current loop is the innermost loop in the control system of PMSM.Its steady and transient performance directly determines the control effect of the motor.In this paper,the FCS-MPC is applied to the current loop control of PMSM,and the predictive current control of PMSM is studied.Two improved control strategies are proposed to solve the problems of large fluctuation of steady-state current and high sensitivity of parameters.Firstly,the mathematical model of PMSM in two-phase rotating coordinate system is established based on coordinate transformation,and the predictive current model is obtained by discretization.Based on the topology of two-level voltage-source inverters,the space voltage vectors generated by different stator winding connection modes are compared and analyzed.The principle of conventional vector control system is introduced and its shortcomings are analyzed.Then,in order to improve the steady-state performance of the conventional predictive current algorithm,the optimal voltage vector and zero vector are modulated,forming a predictive current control based on duty cycle.In order to solve the problem of asynchronism between voltage vector selection and duty cycle calculation,an improved predictive current control based on duty cycle is proposed,which extends the finite control set of voltage vector,improves the method of optimal vector selection and reduces the amount of calculation of the algorithm.The simulation results show that the proposed method has more stable speed and current output,and reduce the harmonic content of stator current.The influence of parameter mismatch on predictive current control of PMSM is studied by establishing a mathematical model of current prediction error.When the parameters are mismatched,the conventional compensation results of delay compensation link are inaccurate.A delay compensation method based on current oversampling is adopted.By analyzing the relationship between voltage vector and prediction error in short time interval,a prediction error compensation algorithm is proposed.The recursive least squares(RLS)online parameter identification algorithm is added to the prediction error compensation to enhance the accuracy of compensation.The effectiveness of the proposed algorithm is verified by simulation.Finally,the conventional predictive current control and the proposed two control strategies are experimentally validated on the experimental platform of PMSM speed control system based on dSPACE.The experimental results verify the effectiveness and superiority of the proposed method.