A microgrid (MG) is a small-scale power system with a cluster of loads and distributed generators operating together through energy management software and devices that act as a single controllable entity with respect to the grid. MG has become a key research element in smart grid and distribution power systems. MG mainly contains different renewable energy sources (RESs) that use various technological advancements, such as power electronics-based technologies. However, it has an unstable output, thereby causing different types of power quality (PQ) events. As a result, standards and mitigation methods have been developed in recent years. To mitigate PQ issues due to MG integration, various methods and standards have been proposed over the last years. Although these individual methods are well documented, a comparative overview had not been introduced so far. Thus, this study aims to fill the gap by reviewing and comparing the prior-art PQ issues, solutions, and standards in MGs. We compare the main issues related to voltage sag, voltage swell, voltage and current harmonics, system unbalances, and fluctuations to ensure high-quality MG output power. The new technologies associated with MGs generate harmonics emission in the range of 2-150 kHz, thereby causing a new phenomenon, namely, supraharmonics (SH) emission, which is not sufficiently covered in the literature. Therefore, the characteristics, causes, consequences, and measurements of SH are highlighted and analyzed. The mitigation strategies, control, and devices of PQ issues are also discussed. Moreover, a comparison is conducted between the most popular devices used to mitigate the PQ issues in MG in terms of cost, rating, and different aspects of performance. This review study can strengthen the efforts toward the mitigation and standards development of PQ issues in MG applications, especially SH. Finally, some recommendations and suggestions to improve PQ of MG, including SH, are highlighted.

In the electric power distribution system, power electronics technologies associated with renewable energy systems (RES) and smart grids have gained growing interest. The power electronics devices are used to convert, control, or transfer electric power from RES to the power grids. However, the continuous increase in switching frequencies resulting from these power electronics technologies has led to the emergence of new emissions in the range of 2-150 kHz, outside the classical frequency range for power quality. These emissions are known worldwide as supraharmonics (SH).These emissions negatively affect the power quality of electrical distribution systems and reduce their efficiency and lifetime. Thus, the supraharmonics emissions have been investigated in the literature, and several methods were developed focusing on identifying, measuring, and setting new standards to mitigate the impact of these emissions on the power quality. Although these individual studies have been well documented, a comparative overview of its identifications, current standards, and measurement techniques had not been described so far. Therefore, this study extensively reviews the related techniques and standards for identifying, measuring, and mitigating SH emissions. Moreover, the current research gap in this important field is highlighted, and an illustration on how this problem was tackled in the past few years is presented. Additionally, the SH characteristics alongside with insights into the mitigations and measurements are highlighted and analyzed accordingly. Finally, some important recommendations to mitigate SH emissions are suggested. This review will hopefully strengthen the efforts toward the development of SH domain by providing the necessary groundwork for further mitigations, standards, and measuring techniques improvement. INDEX TERMS Grid integration; harmonics emissions; high frequency; power quality; renewable energy sources; supraharmonics.