The efficiency of wide-bandgap (WBG) power converters can be greatly improved using high-frequency modulation techniques. This paper proposes using single-loop and double-loop hexagonal sigma-delta modulation (H-Σ∆ and DH-Σ∆ respectively) for voltage source converters (VSC) that use silicon carbide (SiC) semiconductors. These allow high switching frequencies to operate more efficiently than silicon devices. Thus, Σ∆ modulations are excellent candidates for taking advantage of WBG devices. The proposed modulation techniques allow working with a variable switching frequency, thus producing an extreme reduction in switching losses and mitigating the low-order harmonics in comparison with the classical space vector pulse width modulation (SVPWM) technique, and with the innovative variable switching frequency pulse width modulation (VSFPWM). The performance and losses of both Σ∆ techniques are analysed here using Matlab/Simulink and PLECS, and then compared with SVPWM and VSFPWM. Furthermore, the frequency spectrum and the total harmonic distortion (THD) are evaluated. Experimental results performed on a VSC converter that uses SiC MOSFETs show how H-Σ∆ and DH-Σ∆ greatly improve efficiency and generate fewer low-order harmonics than the SVPWM and VSFPWM strategies do.

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In this article, a new model to predict the amplitude reduction of the interference harmonics in power supplies with parallel topology is presented when the switching frequency modulation with variable delay (VDFM) technique is applied. The VDFM method consists of combining the interleaving and switching frequency modulation (SFM) techniques. The new model presented has been evaluated in a multichannel buck converter, operating with different numbers of converters when a triangular modulation profile is used. Theoretical study and experimental results show the influence of the number of converters and the modulation parameters with regard to electromagnetic interference reduction. From the new model presented, it is possible to predict the value of modulation parameters and the numbers of converters in order to satisfy the required attenuation regarding the electromagnetic compatibility directives, when a triangular modulation profile is used.

Abstract:A new technique to reduce EMI in modular power multiconverters is described. The technique is based on a combination of switching frequency modulation and a variable delay between commutation signals of the single converters. The proposed technique has been validated experimentally in a four converters parallel topology. A significant EMI reduction has been obtained with regard to conventional techniques.

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