Research And Design On Torque Ripple Minimization Techniques Of Brushless DC Motor Of Duplex Winding

With the trend to promoting clean energy all over the world and the trend to puring electric vehicles,pure electrical cars become an important research direction.Good performance of the motor will promote the development of new energy vehicles.BLDC has many advantages:small volume,simple structure,running high efficiency,wide speed range,high power density,higher output torque.BLDC is very suitable as a driving motor for electric vehicles.After years of development,BLDC has made great strides in the field of control.However,the torque ripple of the BLDC has an impact on the application range of the motor.Torque ripple becomes an unavoidable fact.Torque ripple of BLDC does not have a significant impact on the vehicle's travel.But the torque ripple will have an effect on the motor efficiency and increase copper consumption.The car's mileage in the electric car will be affected.As people on the electric vehicle mileage requirements,it is an effective method to replace three-phase motors with six-phase motors.The basic structure of BLDC and introduces the six-phase motors and three-phase motor working principle and establishes the mathematical model are introduced in this paper.The commutation torque of three-phase and six-phase motors is deduced.The commutation torque ripple of a six-phase motor is half that of a three-phase motor.Six-phase motor torque ripple is classified.First,during the non-commutation,Diode freewheeling can cause torque ripple.The control strategies of five pwm modulations are compared.It can be derived by calculation the pwm-on-pwm modulation strategy completely suppresses the torque ripple caused by freewheeling.Second,during the commutation,torque ripple is caused by the phase change.It can be derived by calculation the pulsation is related to the motor speed.the pwm-on-pwm commissioning method does not suppress commutation torque ripple when the motor is at high speed.Therefore,a method of commutation discrimination based on hysteresis control is presented in this paper.The principle of overlapping commutation is used to suppress the torque ripple during high speed.The non-commutating phase current balance is achieved by turning off the phase delay when the motor is at high speed.Building simulation with PLECS soft verify the correctness of the suppression strategy of torque ripple.Last,the BLDC controller based on DSP&CPLD is designed as hardware platform.Write the software through the above control strategy.The feasibility of the torque ripple suppression method is verified by experiments.