Research On The Drive And Control Technology Of Dual Three-phase Motor For Electric Vehicles

At present,the development of electric vehicles is limited by battery-related technology.Multi-phase motor enjoys the same output power while the supply voltage is only half of the traditional three-phase motor.Multi-phase motor has the superiority of smaller ripple in electromagnetic torque,and the fault tolerance of the multi-phase system is higher.Thus,multi-phase motor turns to be more suitable for driving electric vehicles for more comfort and safety of passengers.Dual three-phase motor takes the superior advantages in electromagnetic performance of multi-phase motor,and the drive and control system can be realized simply by combining two mature power supply system of three-phase motor,which is thought of great value for further study.Therefore,dual three-phase motor for electric-vehicle drive is investigated in this paper from the following aspects.Firstly,the magnetic force of both the stator and rotor of dual three-phase motor are analyzed based on the winding function method.And the results are all compared to that of traditional three motor.Then,the advantages of smaller electromagnetic torque ripple and lower supply voltage of dual three-phase motor are verified by finite element simulation.Secondly,based on the vector space decomposition model,the vector control of dual three-phase motor under minimum stator current strategy is realized.The harmonic stator current both under two-dimensional and four-dimensional current modulation modes are compared by simulation and experiment.The potential instability of the harmonic subspace caused by mutual coupling in double d-q model is also discussed,and the stability condition is calculated by Root-locus method.In addition,the SVPWM modulation strategy of dual three-phase motor is analyzed,and a sinusoidal voltage modulation algorithm based on four vector SVPWM is studied to reduce the harmonic current under the two-dimensional current modulation mode.The overmodulation algorithm of dual three-phase motor is also analyzed in this paper,which improves the speed output capacity under the vector control of dual threephase motor.Finally,a full-speed MTPA flux weakening control algorithm is proposed based on the characteristics of dual three-phase motor.The constant torque mode and fluxweakening mode are switched by automatically detecting the speed and load of the motor.The overpressure caused by inaccurate parameters of the motor is compensated by voltage feedback,which reduces the dependence on parameters of the model.The harmonic current during flux weakening control can be improved simply by applying the sinusoidal voltage modulation algorithm.The conclusions above are all verified by both simulation and experiments.