The paper presents a power-quality analysis in the utility low-voltage network focusing on harmonic currents’ pollution. Usually, to forecast the modern electrical and electronic devices’ contribution to increasing the current total harmonic distortion factor (THDI) and exceeding the regulation limit, analyses based on tests and models of individual devices are conducted. In this article, a composite approach was applied. The performance of harmonic currents produced by sets of devices commonly used in commercial and residential facilities’ nonlinear loads was investigated. The measurements were conducted with the class A PQ analyzer (FLUKE 435) and dedicated to the specialized PC software. The experimental tests show that the harmonic currents produced by multiple types of nonlinear loads tend to reduce the current total harmonic distortion factor (THDI). The changes of harmonic content caused by summation and/or cancellation effects in total current drawn from the grid by nonlinear loads should be a key factor in harmonic currents’ pollution study. Proper forecasting of the level of harmonic currents injected into the utility grid helps to maintain the quality of electricity at an appropriate level and reduce active power losses, which have a direct impact on the price of electricity generation.

Power quality (PQ) becomes a more and more pressing issue for the operation stability of power systems with renewable energy sources. An important aspect of PQ monitoring of distribution networks is to compare the PQ indicators in different operating conditions. This paper evaluates the impact of a microgrid implementation in a real distribution network on power quality indicators at the point of common coupling in an LV network. The study includes a classical assessment of the long-term PQ parameters according to the EN 50160 standard, such as nominal frequency deviations, voltage RMS variations, voltage fluctuations (represented by long-term flicker severity), voltage unbalance and total harmonic distortion. The PQ evaluation is extended in statistical assessment based on cluster analysis. The case study contains 5 weeks of power quality observation results obtained at the assessment point in two different working conditions of the distribution system: before and after implementing the microgrid. The study allows establishing general conclusions regarding a microgrid interconnection in order not to exceed power quality limits and considering the influence of photovoltaic generation on power quality parameters.

Researchers at many different institutions around the world study voltage and current waveform distortions in power networks using a variety of techniques. Due to the uncontrolled growing number of nonlinear devices supplied by electrical energy, more severe supraharmonic pollution has been observed. A bibliometric analysis of the topic development between 2013 and 2022 is presented in the paper. Using the selected search tools, a comparative review of articles published in the last three years was conducted. It organizes the existing knowledge about supraharmonic pollution generated by nonlinear devices and identifies current research challenges associated with the spread of these disturbances in electrical networks. The most frequently discussed topics by researchers are those that deal with the level of emissions generated by supraharmonic sources and their effects on components of the power system. The second most prominent research direction is the detection, measurement, analysis, and severity evaluation of supraharmonic pollution. Finally, the authors discuss areas of study related to the topic that offers perspectives for future research. The impact of high-frequency component pollution generated by nonlinear loads on emissions intentionally designed to carry communications signals through electrical networks needs to be explored under various power supply conditions.