Research On Issues Of Open-loop Control System Of PMSM

In non-servo systems such as wooden-sawing machines,wind turbines and water pump,the position open-looped control of PMSM has great application prospect.The article focused on the stability of position sensorless wooden-sawing machine under load impact and researched on the operational stability of PMSM under position open-looped control.And based on traditional I/f control strategy,an improved method was proposed to achieve ideal operational performance.Firstly,the mathematical model of PMSM and the principle and procedure of SVPWM technology was introduced.And the motor's mathematical model in the frame of reference position under the control of traditional I/f strategy was analyzed to figure out the relationship between load torque and power factor angle.The torque self-balancing principle was analyzed to figure out the condition of PMSM's stable operation.Then,the article suggested the method to obtain V/f profile according to the outputs of current PI controller of I/f control,and analyzed the voltage variation's influence on motor current through experimental results.Then,the overall improved method based on traditional I/f control strategy was introduced.Judging load variation situation through detecting and calculating power factor angle,the current amplitude compensation and reference position compensation were applied to adjust current according to load torque and prevent synchronizing losing due to fast variation of rotor angle.And motor speed was reduced under large load to ensure electromagnetic torque output in full speed range,and the motor could automatically accelerate from zero speed when load decreases.Then,a simulation model was established to analyze the relationship between power actor angle and angle between frames in the variation process of load torque.By adding compensation links step by step in the model,the improvement performance of different compensation measures and the influence of key parameters on controlling system was analyzed.Finally,a motor experimental platform based on TMS320F28377S was introduced in detail,and motor controlling algorism was implemented to verify practical performance of the improved method.Via multiple experiments,the motor's operational situation and key controlling variable under different load torque were analyzed to verify the experimental effect of proposed improved method.