Common-mode voltage and its cancellation in PWM drive system

Pulse width modulated(PWM) inverter can generate common-mode voltage(CMV) resulting in bearing damage,electro-magnetic interference(EMI) and so on,which decrease the system reliability.In this paper,some theoretic analysis and experimental results prove the characteristics of CMV and its adverse effects,and the methods for CMV cancellations are also presented.Then a novel inverter output active filter based on a single-phase inverter and a five-winding transformer is proposed,utilizing the reconstructed inverse CMV inserted into the motor leads to cancel CMV at motor terminator.The control signals of the PWM inverter and the single-phase inverter are produced by the same control unit,the scheme,control principle,Design guidelines of the proposed filter are also presented.Finally,experimental results prove the proposed filter's effectiveness in eliminating CMV in the PWM inverter driving systems.