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An important power quality concern of integrating single-phase photovoltaic (PV) generators to low-voltage (LV) residential systems, is their impact on harmonic distortions due to their power electronic-based interface through a voltage source converter (VSC). Unfortunately, most existing single-phase PV models are focused on the analysis of an individual device, and do not provide a modular circuit model that can be directly integrated into a commercial harmonic power flow simulation tool for large-scale power system studies. In response, this paper derives a single-input single-output harmonic model for single-phase PVs that is independent of grid parameters, thus enabling multiple of these devices to be considered simultaneously in system-wide harmonic power flow analyses. The model is validated with electromagnetic transient simulations and then, characterization studies are conducted to determine the expected harmonic impact of these PV generators on a real LV system. Results demonstrate these devices can increase system damping at typical low order harmonics and are unlikely to introduce new resonances at this frequency range. In addition, it is essential to model the VSC controller effect for a more accurate assessment of its harmonic impact. Sensitivity studies reveal how different VSC parameters affect this behavior.

This paper provides a detailed comparative analysis between the effect of Type III and Type IV generator technologies on the risk of harmonic resonances in wind parks. Initially, the model and characteristics of Type III and Type IV generators at harmonic frequencies are reviewed. Then, an index based on harmonic amplification at the point of common coupling (PCC) is defined to quantify the overall risk of harmonic resonance in the park. This index is employed to determine and compare the effect of Type III and Type IV generators in different scenarios. Factors such as parameters of the generators, of the wind park circuit, and of the background grid are analyzed. The results reveal that, under the same design premises, Type III-based wind parks tend to present higher risk of resonance than Type IV-based parks at low order harmonics such as the 5th and 7th harmonics.