Research On Non-Sinusoidal Power Supply Technology Of Multiphase Induction Motors

Compared with three-phase induction motor, multi-phase motor can decrease the power demand of each phase winding through adding phase number. When the winding current is unchanged, the power supply voltage can be reduced, otherwise more power can be outputted. Multiphase motor variable frequency speed regulation system has many advantages, such as high power with low voltage, high reliability of system and stable output of torque, it is very suitable for high power application of electric locomotive traction, ship propulsion, etc. In this paper, the non-sinusoidal power supply technology of multiphase induction motor has been researched based on the seven-phase induction motor as an example. The main contents are as follows:According to the theory of winding function, the magnetomotive force of seven-phase induction motor has been analyzed. It is concluded that the current of each harmonic in the distributed winding with concentration and whole distance influences the output torque. According to the theory of multi-loop, the stator and rotor parameters of seven-phase induction motor can be calculated. And on the basis of these parameters, the natural coordinates model and spatial decoupling model of seven-phase induction motor can be established.The voltage space vector of seven-phase inverter has been analyzed, and it is come to the conclusion that the voltage space vector of seven phase inverter has the feature of multi-plane. According to the principle of volt-second balance, combining with the view of multi-plane mapping, the implementation method of multidimensional modulation technology of multiphase inverter has been derived.Based on multiphase motor magnetic potential distribution table, the basic principle of enlarging the motor torque density through the injection of three harmonic is analyzed. Two kinds of injection solution of static harmonic injection and dynamic harmonic injection are presented. The changes of the motor output torque after injecting the harmonic have been analyzed. At the same time, in order to make the inverter working in the linear modulation region in every plane, the relationship between the maximum modulation ratio of harmonic plane and the modulation ratio of fundamental plane is researched. Therefore, the decision-making basis for the control of harmonic content is provided. According to the influence of harmonic injection to torque, the power supply strategies of multiphase motor under different load are obtained.Finally, the non-sinusoidal power supply technology with multiphase multiplanar modulation technology and harmonic injection is simulated, and the experiment is studied on the seven-phase induction motor speed control platform. Both the simulation and experiment results verify the correctness of multidimensional modulation technique and the non-sinusoidal power supply technology and laid a solid foundation for further research on multiphase motor.