Research On Low Speed Performance Of Vector Controlled Multiple Induction Motors Fed By One Inverter

Induction motor drive places an important role of modern industrial and commercial applications.In the case of advanced control situations such as transportation,the structure of single inverter with single motor often cannot meet the drive requirements.It is time to control several motors by one inverter.In order to get precise control,the sensorless vector method is more be used.In the process of multi-motor fed by one inverter,the change of motor parameters will lead to the deviation of estimated speed,the impact the stability of the system.In addition,there is a phenomenon of unstable speed in the low-speed regenerating mode,the stability of the system is poor.Firstly,this paper proposes a coordinated control strategy for a multi-induction motor system.Based on the equivalent model of parallel motors,a speed adaptive system based on full-order flux observer is established.Through the simulation and experimental results,it can be seen that the multi-motor system performs well.In addition,since the observer based on the motor model changes the parameters during operation,the model reference adaptive stator resistance identification strategy is proposed.Through the adaptive control,the motor estimated speed and identification parameters are decoupled and the motor parameters are estimated in real time.The validity of the scheme is verified by simulation experiments.And then,the problem of low speed instability in multi-motor system has been improved.According to the principle of automatic control,the error feedback matrix is analyzed for stability,and the reason of unstable speed is obtained.Without feedback matrix,the speed estimation system exists the unstable zeros,which will have oscillation in low speed.The classical feedback matrix ensures that the speed can be global stable,but the stability is not enough and susceptible to disturbance.Through the Routh’s stability criterion,the classical error feedback matrix is analyzed and the improved feedback matrix is designed.At this time,the system can be stable in all the range and the stability is strong,and the robustness of the parameters is enhanced.The feasibility and validity of the proposed control method are verified by simulation experiments.Finally,a three-motor drag experiment platform based on STM32 ARM is built,and the motors are connected rigid.In this paper,the hardware structure and software algorithm are briefly introduced,and the proposed method is programed and debugged in Keil.The multi-motor vector control experiment and the error feedback matrix performance experiment at low speed are completed.The experimental results show that in sensorless mode,the multi-motor system is stable at zero speed and state switching operation.With the improved feedback gains,the system can remain stable in the global range,and the sensitivity to the parameters is reduced,the performance of multiple motors system is enhanced.