Research On The Brushless DC Motor Drive System Without Electrolytic Capacitor

Brushless DC motor has more and more market share in recent years because of its wide speed range,simple control,and so on.In order to improve the input power factor of the brushless DC motor AC speed regulation system,the topology of the electrolytic capacitor-less inverter is studied.This topology replaces the PFC correction circuit and the large electrolytic capacitor in the traditional topology with the thin-film capacitor,then high input power factor of the drive system is achieved by special control strategy.So the service life and reliability of the system are improved,and the cost is reduced.Firstly,the mathematical model of BLDCM and its traditional square wave control strategy are introduced in this paper.Secondly,the sensorless control strategy of BLDCM is studied based on the inductance method.By detecting the phase current,the magnitude of the inductance is determined.Then,according to the magnetic saturation effect of stator core,the position of rotor magnetic pole is determined.Lastly,depending on the principle of square wave control,the correct driving signals are sent,and BLDCM will work orderly.Thirdly,this paper proposes a new control method that regulates the inverter input current for the brushless DC motor drive system fed by electrolytic capacitor-less inverter,and improve the input power factor of the system.Meanwhile,the PWM_ON_PWM pattern and the overlapping commutation control strategy are used in the proposed system,which can reduce the torque ripple and the current pulsation in BLDCM.Then,according to the disadvantage of inverter input current control strategy,a novel inverter output power control method based on improved square-wave SVPWM is proposed.The effectiveness of the proposed system has been verified by simulation.Finally,the design of the hardware experiment platform based on the TMPM470 FDFG and the software design are described in detail.The correctness and effectiveness of the proposed control strategy are verified by the experimental result.