Research On Electromagnetic Vibration Suppression Of Underground Low Speed And Large Torque Permanent Magnet Synchronous Motor

At present,the development of oilfields in China has created a record of high production,and has entered the later stage of development.The increase of water in oil wells leads to the decline of oil production year by year.The key to oilfield development is taking effective measures to improve oil production and quality.The low-speed and high-torque permanent magnet synchronous motor(PMSM)is used as a new power device of the oil production system.In the working process,the vibration generated by the PMSM itself is an important factor affecting the stability of the operation,as well as the quality and life of the submersible screw pump unit.In this paper,the load test of simulated down-hole oil recovery has been completed,and the electromagnetic vibration suppression scheme has been studied from two aspects: motor structure parameters and control strategy.Firstly,using the existing prototype and equipment in the laboratory,according to downhole oil production conditions design the circulating system of oil production pipeline,and build a test-bed for simulating the down-hole low-speed and high-torque direct drive screw pump production system of permanent magnet synchronous motor,and determine the working parameters of the production system.During the test,measuring the torque and speed at different frequencies,observing the fluctuation degree,and evaluating the output stability characteristics of the down hole low-speed and high-torque permanent magnet synchronous motor.Secondly,according to the parameters of the prototype,establish a two-dimensional model in Ansoft Maxwell and carry out the finite element analysis,including the no-load and load analysis of the motor.The efficiency of the permanent magnet synchronous motor,the curve related to the performance parameters of the motor,and the no-load back EMF,cogging torque and load electromagnetic torque are obtained.Taking the slot width of the motor as the influencing factor,simulate the air gap flux density under different slot width and carry out harmonic analysis to calculate the harmonic distortion rate.Then simulate the electromagnetic force of semi-closed slot and closed slot motor,and analysis the influence of slot width on electromagnetic vibration.Then,based on the mathematical model of PMSM,introduce the transformation modes among three coordinate systems in detail,and give the sub-module models of the important components of the PMSM control system model.Their working principles are analyzed in detail.According to the parameters of the laboratory prototype and the calculation results of the finite element software,establish the vector control system of the down-hole low-speed and hightorque PMSM traditional Simulink complete model.Finally,establish the harmonic mathematical model of the low-speed and high-torque permanent magnet motor,and deduce the steady-state voltage equations of the 5th and 7th harmonics.On this basis,build the harmonic current suppression module.In MATLAB/Simulink environment,simulate the motor control system before and after adding harmonic current suppression module,analysis and compare the simulation results before and after harmonic current suppression.