Research On Variable Frequency Open-loop Control Of Nine-phase Induction Motor

The polyphase induction motor is widely used in marine electric propulsion system because of its high efficiency,high reliability and easy realization of low voltage and high power drive.The open loop control system is simple in design and convenient in control,so it is suitable for starting and adjusting the speed of multiphase induction propulsion motor.In this paper,the large-capacity ship multiphase induction propulsion motor is taken as the research target,and the small-capacity nine-phase induction motor prototype is taken as the concrete object to study the open loop speed regulation system of multiphase induction motor,which has important theoretical significance and practical value.Directing at the nine-phase induction motor,it consists of three sets of windings,and the model of the nine-phase induction motor is derived based on the three-phase motor,and the magnetic linkage,voltage,torque and motion formulas are derived in the natural,static and rotating frame of axes.The simulation analysis is carried out according to its mathematical model,which lays a foundation for the follow-up research of nine-phase induction motor speed regulation system.According to the V/f control principle and the SPWM technology used in the induction motor speed regulation,the no-load and on-load simulation of the V/f control nine-phase induction motor is realized,which is used as the effective comparison data of the experiment.The speed system is constructed,and then a no-load and on-load experiments are conducted.The results show that the current oscillation phenomenon of nine-phase induction motor is obvious under the condition of low and medium frequency under noload,which leads to the instability of the speed regulation process of the motor.In order to solve the problem of current oscillation in the traditional V/f control of nine-phase induction motor for speed regulation,based on the constant flux control principle,an E/f control scheme is proposed.In order to precisely control the flux,the detection coil embedded in the nine-phase induction motor is used to feedback the electromotive force.By calculating the ratio of electromotive force to frequency,the flux is invariable when the motor is running,and make a comparison about V/f and E/f control in each frequency after experiment.Finally,the data indicates that E/f control is capable of optimizing current oscillation of in the low and intermediate frequency of multiphase induction motor,and improve the stability of the system.The nine-phase induction motor speed regulation system platform was built and explained.By changing the voltage and load of the nine-phase induction motor,the performance of the speed regulation system of the nine-phase induction motor under different working conditions was analyzed,and the relationship between the stability of the motor and the voltage and load size was studied.The software program of V/f control and E/f control of nine-phase induction motor open-loop speed regulation system is designed and written,which verifies the feasibility of nine-phase induction motor speed regulation system.