A novel dithering algorithm to reduce the electro-magnetic interference (EMI) in single phase DC/AC inverters

In this paper, the reduction of the electromagnetic emission interference (EMI) from DC/AC inverters through periodic dithering on the switching frequency of the pulse width modulated (PWM) signal is investigated. The effect of the various parameters involved in the dithering concept are studied which leads to proposing an optimum dithering method to reduce the EMI. The most important parameters involved in dithering are the dithering frequency range, rate of change of the dithering and the phase of the dithering signal. The effect of each of these parameters is studied and the values that give the best reduction are found. Moreover, analytical expressions for the EMI production mechanism are derived to be used for comparison purpose. The theoretical prediction for the dithering scheme that provide the best reduction in the EMI are found to be accurate through both simulation and experimental results.