Fast-Processing Sigma–Delta Strategies for Three-Phase Wide-Bandgap Power Converters With Common-Mode Voltage Reduction

Abstract

The electromagnetic compatibility of wide-bandgap (WBG) power converters can be greatly improved using spreadspectrum modulation techniques. This article proposes a family of reduced common-voltage sigma-delta modulations (RCMV-Σ∆) for voltage source converters (VSC) that use gallium nitride (GaN) semiconductors. Specifically, this article proposes three new techniques: two reduced-state sigma-delta modulations (RS-Σ∆1&2) and an active sigma-delta strategy (A-Σ∆). The proposed modulation techniques reduce or eliminate the common-mode voltage (CMV) dv/dt transitions and suppress the noise spikes in the conducted electromagnetic interference (EMI) spectrum. Furthermore, this article proposes the use of fast-processing quantizers for RCMV-Σ∆ techniques as well as for hexagonal sigma-delta (H-Σ∆). These quantizers use a novel calculation methodology that simplifies the implementation of the proposed modulations and considerably reduces their computational cost. The performance and the total harmonic distortion of RCMV-Σ∆ techniques are analysed here using MATLAB/Simulink and PLECS. Experimental results performed on a VSC converter that uses GaN e-HEMTs show how RCMV-Σ∆ techniques considerably improve electromagnetic compatibility and exhibit similar efficiencies and total harmonic distortions (THD) to those of H-Σ∆.

A Novel Three-Dimensional Sigma–Delta Modulation for High-Switching-Frequency Three-Phase Four-Wire Active Power Filters

“…This technique does not produce additional harmonics, such as those at low frequencies. However, the ripple of the currents is slightly higher than that produced by an SPWM, since Σ∆ modulations distribute the switching harmonics at medium frequencies [34]. The efficiency of 3D-Σ∆ modulation is 96.40%, which is higher than that of SPWM modulation.…”

“…Hence, their switching frequencies are variable, so they produce fewer EMIs and losses than other modulation techniques, such as space vector pulse-width modulation [32,33]. Recently, these techniques have been proposed for two-level 3L3W converters [33,34] and two-level five-phase converters [35].…”

“…The proposed fast quantiser is an improvement on those presented in [34], as the new algorithm allows for working in systems where the homopolar component is not zero. The presented fast quantiser defines the sectors of W as follows:…”

“…where k = tan(π/6) and r 0 = [0.67, 0.77]. Note that r 0 can take any value within the specified range, as this does not significantly affect the modulation, as shown in [34]. Given a point in space W, the above expressions can used to determine which sector the point belongs to.…”