Research On Sensorless Control Of Large Inertia Permanent Magnet Synchronous Motor

The Permanent Magnet Synchronous Motor(PMSM)has many advantages such as simple structure,small size,high efficiency,high reliability,and wide speed range.It is widely used in home appliances,automobiles,ships,wind power generation systems,aerospace and other fields.In high-performance permanent magnet synchronous motor control systems,it is necessary to rely on high-precision speed sensors to detect feedback speed information to achieve precise closed-loop control of the motor.However,the use of high-precision speed sensors increases the cost of the control system and increases the volume of the motor,which is inconvenient for installation and use.Most importantly,sensors cannot work in harsh environments for a long time,affecting the normal operation of the motor control system.Therefore,research on sensorless control of permanent magnet synchronous motors has significant significance in improving system reliability and reducing system costs.this thesis focuses on the large-inertia permanent magnet synchronous motor used in electric vehicles,which has a large moment of inertia and a large torque problem when starting under uphill and horizontal running conditions.Through theoretical research on sensorless control technology of permanent magnet synchronous motors,this paper realizes self-starting of large-inertia permanent magnet synchronous motors under large torque.The specific contents are as follows:Firstly,the mathematical model of permanent magnet synchronous motor under threephase stationary,two-phase stationary and rotating coordinate systems is introduced,and various vector control strategies of the motor are introduced based on this;the mathematical model of two-level three-phase inverter is established,and space pulse width modulation(SVPWM)algorithm is used to modulate sine voltage to control permanent magnet synchronous motor.A new SVPWM based on unified modulation model is proposed to simplify traditional SVPWM workflow.The correctness of the new SVPWM algorithm is verified by TMS320F28069 DSP.Secondly,based on vector control of permanent magnet synchronous motor and the basic principle of sliding mode variable structure control,a traditional sliding mode observer without speed sensor control method for permanent magnet synchronous motor under twophase stationary coordinate is constructed.The sigmoid function is used instead of the traditional sign function to eliminate the low-pass filtering link and simplify the structure of sliding mode observer.It effectively suppresses jitter and avoids phase delay caused by lowpass filter use.At the same time,normalized orthogonal lock-in phase extraction is used to extract motor speed and rotor position information to improve precision of sensorless control of permanent magnet synchronous motor.A simulation platform is built in Matlab/Simulink to verify feasibility of two algorithms for small-inertia and large-inertia permanent magnet synchronous motors respectively.The results show that these two algorithms have good control effect on small-inertia permanent magnet synchronous motors but are not suitable for large-inertia permanent magnet synchronous motors.Then,an improved sensorless control method based on rotating coordinate system adaptive sliding mode observer is proposed for large-inertia permanent magnet synchronous motors that cannot be driven by sliding mode observer without speed sensor under two-phase stationary coordinate system and that will cause slow dynamic response and large calculation amount due to introduction of normalized orthogonal lock-in phase loop.Finally,a sensorless experimental platform for permanent magnet synchronous motors was built to verify various theoretical algorithms proposed in this paper from both hardware and software aspects.It realized sensorless control of large-inertia permanent magnet synchronous motors.