Research On High Frequency Link Drive For Brushless DC Motor

The depletion of traditional fossil fuels and atmospheric pollution are becoming more and more serious.Moreover,electric vehicles have many advantages such as high efficiency,simple structure,low noise,and no pollution.Therefore,electric vehicles are bound to become the popular vehicles in the future.Brushless DC motor has advantages of good speed control performance,long service life,reliable operation and so on,so it can be applied in scientific research,military industry,aerospace,civil and other fields.Therefore,brushless DC motor is selected as the research object.The high-frequency link matrix inverter has the characteristics of large power density and light weight.It can also effectively overcome the problem of damage caused by the short-term conducts of the same bridge arm.Therefore,the high-frequency link inverter is selected as the driver of the brushless DC motor.Firstly,the research background and significance of the topic are introduced,and the development status and trends of various types of electric vehicles at domestic and abroad are summarized.Brushless DC motors have been widely applied in the field of electric vehicles because of their excellent performance.At the same time,it briefly describes the development of high-frequency inverter technology and brushless DC motor topology.Secondly,the structure and mathematical model of the brushless DC motor are briefly described.Because it adopts the electronic commutation method,it can effectively reduce the mechanical loss.The two-two conduction and three-three conduction of the brushless DC motor driven by the high-frequency link inverter were verified by simulation.The simulation results are in accordance with the theoretical analysis and it is proved that the high-frequency link inverter driving brushless DC motor can realize two kinds of the classic control method is stable and reliable.Thirdly,comparing two classical control methods of brushless DC motor and combining these two control methods,this paper proposes a mode of two-two starting three-three running operation of brushless DC motor driven by high-frequency link inverter.In view of the inaccurate synthesis of the drive signal during the start-up phase ofthe three-three mode turn-on of the experimental conditions,and the difficulty in synthesizing the drive signals of two-two starting three-three running,the method of a step signal as the switching time base is proposed,which effectively overcomes the problem.In addition,a 150-degree conduction method of a high-frequency link inverter driven brushless DC motor is proposed in combination with 120-degree and 180-degree conduction method,which may also be referred to as two-three hybrid conduction,which increases the number of voltage vectors.The original sector division mode improves the utilization of the windings.Based on this,two new types of PWM modulation methods are proposed.Secondly,a twelve-sector direct torque control of a brushless DC motor driven by a high-frequency link inverter is proposed.This method can effectively reduce the commutation torque ripple problem.Finally,the experiment platform and hardware circuit of the project were set up.The DSP-CPLD combined control system was taken as the core of the control.Based on the theoretical analysis and simulation,relevant experimental verification was carried out.