Research On MTPA And Leading Angle Flux Weakening Control System Of PMSM

Permanent magnet synchronous motor(PMSM)has the characteristics of simple structure,small volume and high power density.The electromagnetic torque of PMSM consists of two parts:permanent magnet torque and reluctance torque.Although the control method of id=0 is simple and easy to implement,the control method does not utilize reluctance torque.The maximum torque-to-current ratio(MTPA)control can make full use of the reluctance torque.Compared with the id=0 control method,the required stator current is smaller under the same electromagnetic torque,which saves the inverter capacity and improves effectiveness.As the motor speed increases,the back electromotive force reaches the maximum voltage value provided by the inverter.At this time,in order to continue the motor speed,the permanent magnet magnetic field,that is,the weak magnetic speed increase,must be weakened.In order to control the PMSM with high efficiency,high torque and wide speed range,this paper studies the MTPA and weak magnetic control methods,and designs a MTPA-based lead angle weak magnetic control method to realize the motor.High efficiency control over a wide speed range.The effectiveness of the MTPA and field weakening methods designed in this paper is verified by simulation and hardware experiments.Main tasks as follows:The mathematical model of PMSM,the principle of coordinate transformation,the vector control principle of PMSM and the control steps are analyzed.The principle of MTPA control and field weakening control of permanent magnet synchronous motor is studied.Combined with the mathematical model of PMSM in synchronous rotating coordinate system,the important formulas of MTPA and field weakening control are derived by using voltage,current and torque equations.The common methods of MTPA control of permanent magnet synchronous motor are compared and the principle and characteristics of these methods are analyzed.The MTPA control system of formula method,curve fitting method and linear interpolation table lookup method is designed.Through MATLAB simulation,it is proved that under the same torque,compared with the control mode,the stator current required by the MTPA control mode is smaller,the inverter capacity is saved,and the efficiency is improved.In order to make the PMSM run above the rated speed and widen the speed range of the PMSM,based on the MTPA and the weak magnetic control method,a control method based on MTPA for the lead angle weakening magnet is designed to improve the motor MTPA and field weakening control of dynamic performance.The algorithm uses the lead angle weak field control module to compensate the lead angle of the MTPA control,and changes the established trajectory of the current vector to weaken the magnet so that the motor continues to increase speed.The feasibility of the MTPA-based lead angle weak magnetic control method is verified by MATLAB simulation.Finally,by constructing a hardware experiment platform,the comparison with the MTPA control method is carried out to verify that the MTPA control algorithm has high control efficiency.The MTPA-based lead angle weak field control algorithm designed in this paper can dynamically switch the PMSM between MTPA and field weakening control,which effectively improves the speed range of PMSM operation.