Impact of Harmonics of Distributed Generators on the Harmonic Profiling of Distribution Networks

Distributed generators (DGs) have emerged as a go-to solution to accommodate increasing loads, with the existing grid infrastructure. The DG-injected power can be consumed locally, thereby reducing the grid current and improving the voltage profile. The power-electronics interface-based DGs, controlled as current sources, employ a grid-side filter for injecting sinusoidal current into the grid. As the filter is designed to meet IEEE compliance for DG grid integration, the current THD is restricted to less than 5%. Although the compliance is met, these harmonics injected into the grid significantly deteriorate the harmonic profile of the entire grid. This study quantifies the impact of two types of DGs – constant power DGs (Type-1) and varying power DGs (Type-II) on the utility grid. An actual 24-hour data-based IEEE 33-bus distribution network, consisting of both linear and non-linear loads, is used to quantify the DGs' harmonic impact. Post-DGs addition, it is observed that Type-I DGs increase the voltage THD by at least 1% at the farthest nodes, although the pattern remains consistent with that of prior DG addition. However, with Type-II DGs, the profile obtained is further deteriorated and inconsistent and exhibits a strong dependence on the power generation of the DG.