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 $\left(TH{D}_I\right)$ 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 $\left(TH{D}_I\right)$. 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.

This paper discusses power flow control algorithm in a microgrid with battery energy storage system. Depending on the state of charge of the storage and the power difference between generation and load, the storage operates in charge or discharge modes adjusting the instantaneous power. The goal is to obtain exchange power changes with the distribution system according to a pre-set curve. The system is simulated in MATLAB. The results show the effectiveness of the proposed control algorithm.