The power quality of electrical grids is becoming an important issue worldwide. The electrical grid has to deliver sinusoidal voltages and currents without frequency or amplitude variations. However, the connection of non-linear loads generates harmonics that degrade the grid quality. The presence of harmonics in the load currents has many negative consequences and can distort the voltage waveform at the point of common coupling (PCC). Thus, it is essential to mitigate the harmonics in order to maintain a suitable grid quality. This is a shared responsibility between energy suppliers, manufacturers of electric and electronic equipment, and users. In this context, this work presents, for each stakeholder, a comprehensive analysis of their responsibilities and the standards that they should meet. Additionally, this paper reviews the most common types of filters used to comply with the applicable standards in industrial applications. Finally, in order to prove that active power filters allow maintaining good power quality in all types of grid, commercially available active power filters were installed in three different grids contexts: an office building, a factory, and a stadium with a large number of LEDs. The experimental results obtained were used to evaluate the impact of active filters on grid quality. This review would help users to overcome their grid distortion problems.

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.

Power devices based on wide band-gap materials are emerging as alternatives to silicon-based devices. These new devices allow designing and building converters with fewer power losses, and are thus more highly efficient than traditional power converters. Among the wide band-gap materials in use, silicon carbide (SiC) and gallium nitride (GaN) devices are the most promising because of their excellent properties and commercial availability. This paper compares the losses produced in two-level and three-level power converters that use the aforementioned technologies. In addition, we assess the impact on the converter performance caused by the modulation technique. Simulation results under various operating points are reported and compared.

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∆.

No abstract