Hybrid Voltage and Current Control Method for Harmonic Mitigation of Single-Phase AC Loads in DC Microgrids

TL;DR

This paper introduces a hybrid control method for DC microgrids that effectively mitigates harmonic currents caused by single-phase AC loads, improving efficiency and power quality through decoupled voltage and harmonic current regulation.

Contribution

It proposes a novel hybrid voltage and current control scheme that decouples harmonic mitigation from voltage regulation in DC microgrids, validated by frequency and time-domain analysis.

Findings

Decoupled control loops prevent interaction between voltage and harmonic current regulation.

Hardware-in-the-loop tests confirm effective harmonic mitigation.

The method enhances power quality and reduces losses in DC microgrids.

Abstract

DC microgrids provide an efficient framework for the interconnection of DC distributed energy resources (DERs) and DC loads. To continue to supply legacy single-phase AC loads, DC/AC converters can be integrated in the DC microgrid. The oscillatory instantaneous power of the single-phase AC load translates into a harmonic current on the converter's DC side, which increases the losses and causes unwanted voltage harmonics in the DC microgrid. To mitigate this issue, this paper proposes a hybrid voltage and current control method (HCM) for DERs. This scheme consists of an inner current control loop and an outer control layer which determines the reference for the inner loop. The outer control layer combines the DC voltage control loop with an output harmonic current control loop. This hybrid structure enables simultaneous regulation of the DC components of the DER output voltage and control of the harmonic component of the DER output current in accordance with the local single-phase AC load's demand. Frequency-domain analysis of the proposed method is presented to demonstrate the DC voltage and harmonic current loops are decoupled and there is no unwanted interaction between them. Additionally, time-domain response of the proposed scheme is validated through hardware-in-the-loop test results.