Research On Three-phase Brushless DC Motor Control Based On Soft-switching

Since the advantages of long life,low noise,high starting torque and high stability,the brushless DC motor(BLDCM)has been used widely in various high performance drive systems.Under the low-carbon environment of current socirety,the electric vehicles(EV)come into the market increasingly.As the power source of EV,the research about the BLDCM has become a hot spot recently in the field of Power Electronics and Power Drives.The loss of brushless motor includes the loss of motor itself and drive circuits.According to the problem that the hard switching inverter in the drive circuits generates more switching loss,a method of reducing the loss of brushless DC modor drive circuit with the soft-switching is proposed to further improve the operating efficiency of the system.In this paper,the STM32F407ZGT6 chip which has a strong ability of data processing as a low-power 32-bit morcoprocessor is used.Firstly,this paper analyzes the working principle and working characteristics of brushless DC motor.And the mathematical model of BLDCM is deduced briefly.Then the brushless DC motor model is built to get the motor phase voltage,phase current,speed and torque curve.Secondly,by analysing the four soft-switching inverter,we select the type of PRDCLI soft-switching inverter as the research object.Then the working principle,working process and struture of this soft-switching inverter.By selecting the appropriate simulation paramaters,the simplified circuit is simulated and the validity of this theory is verified.In addition,the method of combining the soft-switching technology and the control of BLDCM is studied,and the zero voltage switching realization process of bridge-arm tube is given.Finally,the schematic drawings of the control circuit and power main circuit are designed,and the debugging of hardware circuit and the software programs are completed.Then the zero voltage switching of the bridge-arm tube is achieved.Besides,by selecting the virtual instrument Labview as the PC platform,the monitoring interface,data communication and acquisition are designed to improve the debugging efficiency of system.The testing results show that the hardware circuit and software design of this control system are reasonable and the motor operating efficiency is increased by 6%,which can meet the design requirements.