Research On Speed Sensor-less Vector Control System For Dual Three-phase Induction Motor

As the science and technology developing,the conventional three-phase motor speed control system generally cannot meet the controlling requirements in high power with low voltage applications including ship propulsion,aerospace,etc.So it has gradually become a popular research topic in multi-phase motor speed control system domain.Comparing with the conventional three-phase AC motor,the multi-phase induction motor is definitely more robust and advanced since the lower torque ripple,higher reliability,better steady and dynamic performance.In order to achieve those controlling requirements with such high performance,AC speed-regulating system will be controlled by vector and direct torque strategies to realize closed-loop control.Comparing with the direct torque control,vector control strategy produces less motor current ripple,meanwhile it also produces lower torque ripple.In the speed detecting link,conventional speed sensor is relevant with environmental factors and machine parameters,it may leads to inaccurate speed measurements.Through the method that using speed sensor-less technology to establish the corresponding rotational speed estimation module can effectively solve the above problems.This thesis analyses the definition mode of multi-phase motor and the situation of temporal harmonic and magnetic motive force with the study for dual three-phase induction motor.According to the space vector decoupling transformation theory,the mathematical model of dual three-phase induction motor is deduced,and then the correctness can be verified by building the corresponding simulation model.Considering the problem that the harmonic current of stator is really large in the dual three-phase induction motor,a space vector pulse width modulation(SVPWM)algorithm based on space vector decoupling transformation will be introduced.This algorithm through compounding appropriate middle voltage vector to achieve the purpose of reducing the stator current harmonic content,and then building the corresponding open-loop simulation model in Matlab/Simulink to verify this algorithm.According to the principle of rotor flux orientation,the conventional double three-phase induction motor vector control strategy is derived,then by introducing the concept of internal model decoupling,replacing current loop PI controller with internal model control(IMC)module and building the model of current loop using IMC vector control system.By comparing these simulation results of the two kinds of control scheme,IMC vector control system will be able to demonstrate the validity and superiority of current loop.Due to the shaft encoder will be influenced by parameters and environment factors,the speed sensor-less module will be applied instead of the conventional shaft encoder to track motor speed.According to the characteristics of dual three-phase induction motor vector control system and the control theories of model reference adaptive system(MRAS),a speed identification algorithm of variable parameter MRAS is used to improve the properties of the speed sensor-less estimation module in the dual three-phase induction motor speed control system.This algorithm ensures that the speed tracking motor is always precise in both low speed and high speed range.This thesis is applying TMS320F2812 chip from TI company as the master device.The open-loop SVPWM algorithm,closed-loop vector control strategy and speed sensor-less control scheme were verified respectively on the dual three-phase induction motor platform.The experimental results demonstrate that the theoretical researches in this thesis are effective and feasible.