Research On Soft Switch Driving Control Of Brushless DC Motor

Brushless DC motors(BLDCM)are typically driven by pulse width modulation(PWM)in the inverter’s hard-switching mode.In the hard switching mode,the motor has high torque ripple and low efficiency.Especially when the switching frequency is high,the switching loss will rise sharply,and the parasitic capacitance between the electrodes existing in the power device will generate a high level during the switching process.Voltage variations and current changes that may be coupled to the input cause high electromagnetic interference and diode reverse recovery current problems.Therefore,low efficiency and large electromagnetic interference limit the application of brushless DC motors based on hard-switching in demanding applications,and soft-switching technology is considered by many domestic and foreign scholars to be one of the important ways to solve these problems.In this thesis,the soft-switching technology after high frequency is combined with the drive control of brushless DC motor,aiming at many problems of the traditional hard-switching mode inverters of brushless DC motor.The switching loss on the inverter side is reduced by adding anauxiliary resonant circuit.According to the equivalent circuit diagram under different modes,the resonant circuit was deeply analyzed and a reasonable control strategy was proposed,and the circuit model was simulated and verified.The main research contents of this paper are as follows:(1)Firstly,this thesis deeply analyzes the basic composition and working principle of brushless DC motor,and makes a formula derivation based on the theoretical analysis of the mathematical model of brushless DC motor.At the same time,it also analyzes its working characteristics and builds it in Matlab/Simulink environment.Two kinds of simulation models of brushless DC motor are obtained.The waveforms of important parameters such as motor speed,torque and phase current are obtained by simulation of the construction model.(2)Secondly,through the description and analysis of several soft-switching inverter characteristics,the resonant-pole soft-switching inverter is selected as the research object of this thesis.Then the drive control circuit of the brushless DC motor resonant soft-switching inverter with zero voltage turn-on and turn-off capability is designed,and the principle and several working modes are analyzed.The power switch tube is given.The conduction time and sequence,as well as the Simulink simulation verification of the circuit structure,verify the rationality and feasibility of the theoretical analysis.(3)Finally,according to the design of the circuit topology of the brushless DC motor control system,the schematic drawing of the module circuit and the PCB circuit board design are carried out on the Altium Designer18 software,and the real-time debugging of the hardware circuit and the writing of some software programs are also completed.Some software designs have also been debugged.