Research On Technologies For Sensorless Control Of Induction Motor Drives At Low Speed

With the social demand of new and old kinetic energy conversion,for energy saving and emission reduction,the application of speed sensorless control technology with the advantages of low cost and high reliability is of great significance,and therefore has become a hot spot of current research.But it has the problems of poor drive performance at very-low speed and zero speed.Therefore,the research on the sensorless algorithm of IM is of great significance to the extensive application of IM in industrial occasions.For low dynamic performance requirements,a voltage vector control algorithm based on V/F control is adopted.The control algorithm adopts the stator resistance voltage drop compensation,reactive current closed control,slip compensation and torque improvement,and the problems of poor low speed performance,light load instability and continuous oscillation is improved at low speed.For high dynamic performance requirements,a sensorless vector control algorithm based on adaptive full order observer(AFO)is adopted.A novel design method is proposed based on the principle of minimum excitation current error,and the feedback gains and is speed estimation law is improved,the error of excitation current is minimized and the problem of poor performance at low speed is improved.For the sensitivity of IM parameters,the influence of IM parameters is analyzed by using frequency characteristic method,and then a set of off-line parameter identification method at stand-still is used to provide reliable IM parameter.In order to verify the reliability and validity of algorithm,this thesis uses Mathematica and MATLAB to make theoretical analysis,and uses TMS320F2812 chip as the main control chip,2.2kW IM as the driving motor,and magnetic powder brake as the load to build experimental platform.Based on V/F control,the voltage vector control method is adopted.The experimental results show that,the problems of poor low speed performance,light load instability and continuous oscillation is solved,and the system is stabilized at 0～50Hz.For the improved AFO algorithm ensures that the motor flux is constant at the full speed range,enabling the motor to operate stably at very low speed and zero speed,speed accuracy and load capacity is improved.For the off-line parameter identification method at standstill,the reliable IM parameters is acquired by the experimental.According to the above methods,the speed sensorless control of IM can realize the stable operation at low speed,extremely very-low speed and zero speed,and accurately identify the motor parameters.