Research On Conducted Interference Suppresion Method Of PWM Drive Motor System

With the development of power electronics,Pulse Width Modulation technology is gradually applied to modern motor drive systems.PWM technology improves the speed control performance of motors,but it also brings new problems.Semiconductor devices in power converters produce large dv/dt and di/dt at high-speed switching,causing severe electromagnetic interference.Taking a 400 W motor driver as an example,this paper study the generation mechanism and suppression methods of conducted interference in PWM drive motor systems.First of all,the overall circuit structure of PWM drive motor system is given,and the working principles of PFC part and Inverter part are briefly introduced.Then,the causes and coupling paths of conducted interference in PFC part and Inverter part of this system are carefully analyzed,and the equivalent circuits of differential and common mode conducted interference are established,which lays the foundation for conducted interference suppression.Secondly,this paper study suppression methods of noise source.First,the expression of the harmonic amplitude of noise source is derived,which lays the theoretical foundation for noise source suppression.Then,the system conducted interference suppression schemes that increasing gate drive resistance and reducing reverse recovery current of the diode for PFC part,and reducing the switching frequency and DC bus voltage for Inverter part are proposed.And experiments prove that these methods are effective.Finally,this paper study methods of suppressing conducted interference based on coupling path.First,the commonly used EMI filter is studied,and it’s circuit structure selection,parameter calculation and the influence of filter components on conducted interference are analyzed in depth.Then,for the shortcoming of two-stage EMI filter that is too bulky,this paper proposes a method that to combine single-stage EMI filter with ground LC filter to suppress conducted interference of small and medium-sized power equipments.The experimental results show that this new method has better suppression effect than the traditional two-stage EMI filter.The effectiveness of the two methods of putting a magnetic ring on motor three-phase wires or L,N wires is studied,and the influence of the number of turns of magnetic ring on conducted interference is analyzed.