Research And Implementation Of PMSM Speed Sensorless Control Algorithm Based On Sliding Mode Obsever

For the vector control system of permanent magnet synchronous motor(PMSM),rotor position and speed are two essential parameters.In the traditional vector control strategy,mechanical devices such as an optical encoder or a rotary transformer are installed on the rotor shaft to detect rotor position information.This not only increases hardware costs,but also reduces the flexibility and reliability of the control system.simultaneously,it also limits the application of permanent magnet synchronous motors in harsh environments and complex operating conditions.Sensorless control algorithm saves the troubles of encoders or resolvers,it has more advantages,such as low cost,high reliability etc.So the sensorless control algorithm is becoming one of researching hotspots.Based on the background of the test system of permanent magnet direct drive wind turbine,the speed sensorless control strategy of surface-mounted permanent magnet synchronous motor is studied in this paper.Firstly,the research background and significance of this topic are explained,and the performance characteristics of different motor drive systems are compared and analyzed.The research status and development trend of speed sensorless control algorithm for permanent magnet synchronous motor at domestic and overseas are introduced.Secondly,this paper expounds the structure classification and operation principle of permanent magnet synchronous motor,and briefly analyzes its mathematical model in three kinds of coordinate systems.At the same time,the voltage space vector pulse width modulation technique and some common vector control strategies are discussed.Then,the basic principle of sliding mode control is introduced.Combined with the mathematical model of permanent magnet synchronous motor,a current-type sliding mode observer is designed to realize the observation of the back EMF of the motor.In order to obtain higher accuracy,the orthogonal phase-locked loop is used to estimate the rotor position information.Aiming at the problem that the identification accuracy of the sliding mode observer is not enough near the zero speed domain and the difficulty of starting for speed sensorless control,a starting method is studied with speed open loop and current closed loop.The operation principle of the starting method is analyzed,and the selection principle of the related control parameters is given.In order to avoid the motor losing step caused by the switching of control strategy,an improved switching strategy was studied to achieve a smooth transition between open-loop start-up and speed sensorless closed-loop operation.The simulation model of Speed sensorless control is built on the MATLAB/SIMULINK platform,and the simulation results verify the correctness of the method.Finally,the hardware and software of the sensorless vector control system of PMSM is designed.The hardware experiment platform is built using the Beckhoff CX1030 as the main controller.Based on the TwinCAT development environment,the control system software is designed,and the program flow and code realization process are introduced in detail' Subsequently,the experimental verification was carried out on a 200W multi-pole permanent magnet synchronous motor.The experimental data verifies the correctness and feasibility of the control algorithms studied in this paper.