A new two-dimensional random switching frequency PWM (2D-RSF-PWM) method is proposed for VFDs. The proposed 2D-RSF-PWM method is based on two newly defined parameters which are spread factor and number of repetitions. Hence, random switching frequency pattern with limited variation band of switching frequency is achieved by selecting the proper values of these two parameters. Accordingly, applying the proposed 2D-RSF-PWM method results in improved conductive EMI performance at high frequencies, enhanced switching noise reduction at low frequencies, and lower THD in comparison to the conventional SPWM and RSF-PWM methods. Moreover, the input EMI filters are designed for both cases of applying the proposed 2D-RSF-PWM and the traditional SPWM methods to meet the IEC 61800-3 standard Category C2 requirements. Comparison between two designed input EMI filters shows that the values of CM and DM inductors of the input EMI filter are decreased by factor of 3 by applying the proposed 2D-RSF-PWM method in comparison to the conventional SPWM method. The presented results and theoretical analysis verify the performance of the proposed 2D-RSF-PWM method.
