Research On Wireless Drive And Control System Of Brushless DC Motor Based On Multi-frequency Pulse Width Modulation

Wireless power transfer(WPT)technology has the advantages of strong flexibility and high safety.At present,it mainly uses resistors or batteries as the load,and it has many applications in charging scenarios.When the motor is used as the load of WPT,the system structure is complex and the analysis is difficult.And the lack of feedback loop,unable to achieve stable control of the motor.In this paper,a wireless drive and control method of brushless DC(BLDC)motor based on multi-frequency pulse width modulation(MFPWM)is proposed,and a magnetic coupling resonant wireless drive and control system of BLDC motor is constructed,which realizes wireless drive and closed-loop control of motor speed.In addition,the motor wireless drive and control system is sensitive to the harmonics of the MFPWM inverter.Based on the double Fourier series,this paper studies the influence of dead time on the harmonics of the MFPWM inverter,which lays a theoretical foundation for improving the stability of the motor wireless drive and control system.Firstly,the power loop and control loop of the motor are constructed by using the technology of simultaneity wireless information and power transfer(SWIPT),and the BLDC motor wireless drive and control system is divided into SWIPT subsystem and BLDC motor subsystem for modeling.A single inverter driven by MFPWM technology is proposed to transmit power and control information at the same time.The magnetic coupling resonant integrated power and information transmission coil is analyzed and optimized,and the influence of coil parameters on power and information transmission performance is studied.The closedloop control module of BLDC motor speed based on wireless transmission is designed.Experiments show that the speed error is less than 0.66%.Secondly,dead time produces harmonics in MFPWM inverter,which has an important impact on SWIPT subsystem and BLDC motor subsystem based on multi-frequency transmission.In this paper,taking a dual-frequency system as an example,the theoretical solution of each harmonic content of MFPWM inverter is derived based on double Fourier series,and the influence of dead time is studied on this basis.The simulation and experimental results are consistent with the theoretical analysis results,and the error at about 95% harmonic frequency in the 499 th harmonic range is less than 2%.Finally,an experimental platform of BLDC motor wireless drive and control system is built,which can drive the BLDC motor to run and adjust the motor speed under the wireless transmission distance of 12 cm.The motor speed remains at the set speed even when the voltage fluctuates,which proves that the system can run stably and reliably.The simulation and experimental platform of MFPWM inverter are built,and the harmonic content of the inverter in different dead time is studied to verify the analysis method of MFPWM harmonics proposed in this paper.The analysis shows that when the dead time of rising edge is less than the minimum pulse width of MFPWM inverter,the amplitudes of the two expected frequency components remain unchanged;When the dead time of the rising edge exceeds the minimum pulse width of the MFPWM inverter,both the THD of the inverter output voltage and the amplitude of the expected frequency component are affected,so it is necessary to choose the dead time in a compromise.This provides an important theoretical support for the application of MFPWM technology in the fields of SWIPT and multi-load WPT.