Research On Common-mode Voltage And Its Cancellation In PWM Multi-drive System

The PWM technology application can be used to solve many problems in thepractical production. However, there some negative effects including theelectromagnetic interference, bearing damage and cable burst exist as well. Thesenegative effects also exist in the PWM multi-drive system, and even generate moreterrible consequence as the intensified electromagnetic interference.Firstly, regarding the PWM multi-drive system as the object to study thecommon-mode voltage and its negative effects nature generated in the subsystem. Itis concluded that the common-mode voltage is the key to generate negative effects inthe PWM multi-drive system. The RCL filter is applied to suppress the commonmode voltage and its effectiveness is verified by the simulation.Secondly, the negative effects of the PWM multi-drive system are researchedbased on the above analysis. The research object composes with two drive subsystem,and the common-mode voltage characteristics of the multi-drive system are analyzedas well. The results show that the nature of the common-mode voltage will not bechanged by the multi-drive system. However, the leakage current will be changed inthe PWM multi-drive system and the electromagnetic interference will be generated.The effective method is proposed to suppress the common mode voltage in the PWMmulti-drive system. The method of combining the RCL filter with the improvedSVPWM drive control strategy to suppress the common mode voltage and theleakage current is used in this paper. And the feasibility of this method is verified byapplying PSPICE to simulate.Finally, the PWM experimental platform is established in order to verify thefeasibility of the theory. The experiments are conducted to verify the above theorymethods and the results demonstrate the feasibility of the proposed method.