Research On Low Speed Vector Control System Of Three-Phase Asynchronous Motor

Three phase asynchronous motors are widely used in China’s industrial and agricultural production,transportation,national defense,and our daily lives.CNC machine tools,new energy vehicles,and cranes require motors to operate stably under low speed and high load conditions.However,there are still many problems with vector control technology under low speed conditions.With the promotion of energy conservation and emission reduction,as well as the development needs of society,high-performance vector control technology still has huge development prospects,especially in low-speed operating conditions.This article aims to address the issues of complex high-performance vector control schemes and unstable low speed operation.Based on extensive literature review,key technologies such as flux estimation and speed estimation in three-phase asynchronous motor vector control systems are summarized and reviewed,and a direct vector control system with rotor magnetic field orientation is determined.This article provides a detailed introduction to the mathematical model,coordinate transformation theory,and mathematical model based on rotor flux orientation of AC asynchronous motors.Based on this,a series of problems that arise due to the existence of pure integration links in traditional voltage models that do not require speed information and have a simple structure are analyzed through theoretical and simulation research.The use of a first-order low-pass filter instead of a pure integration link is the most basic improvement of the voltage model flux observer.However,at low speeds,flux observation based on low-pass filters may result in amplitude and phase errors.Therefore,compensation links need to be added to compensate for it.For three types of flux observers with compensation loops,detailed theoretical and simulation studies have been conducted on how to achieve accurate flux observation under different operating conditions at low speeds.The flux observer based on saturation feedback integrator will generate nonlinear distortion in the flux output when the limiting amplitude is lower than the actual amplitude due to the addition of a limiter with saturation nonlinear characteristics.In the flux observation model of the saturation feedback integrator based on coordinate transformation,the addition of coordinate transformation improves the nonlinear distortion problem.The output sine of the flux is good,but the flux output is still limited by the influence of amplitude L.The flux observer based on adaptive compensation integrator can eliminate the DC component caused by the initial phase error of the pure integrator,effectively suppress the integral drift problem,and accurately observe the flux information under low speed conditions.Based on the flux observation algorithms of low-pass filter and adaptive compensation integrator,a MATLAB simulation model was established to simulate the vector control system.The flux observation accuracy,rotational speed,torque,three-phase stator current,and other states under no-load and loaded conditions under low speed operation were compared and analyzed.The feasibility of the vector control algorithm used in this paper was verified through simulation.Establish a motor control experimental platform based on a 3k W asynchronous motor in the laboratory,design and develop a controller based on the TI TMS320F28335 chip and a frequency converter for the main bridge inverter circuit.Reasonably design its drive circuit,sampling circuit,protection circuit,and other peripheral circuits.Write a system operation program based on the TI CCS7.4.0 software,and use Lab VIEW to build a simple upper computer communication page.Through testing and experimental verification of the entire motor control experimental platform,the vector control system based on adaptive compensation integrator can achieve stable operation of asynchronous motors at low speeds.