Effective dithering technique for EMI reduction in three phase DC/AC inverters

Three phase DC/AC inverters in power electronic applications produce electromagnetic interference (EMI) due to switching of the power semiconductor devices at high frequencies. Dithering the switching frequency is one of the effective and low cost tools to reduce EMI. To maximize the usefulness of the dithering process, the effect of each of its parameters on the EMI reduction needs to be understood. In this paper, the parameters of triangular periodic dithering are investigated to find their values in minimizing EMI for three phase DC/AC inverters. The paper presents that, by increasing the amplitude of the dithering signal and selecting its frequency to be equal to the inverter voltage frequency, the EMI can be reduced. Moreover, by selecting a phase shift of π/12 between the dithering signal and any of the inverter currents, the EMI is minimized compared to other phase shift amounts. The proposed technique is validated through simulation studies.