A Novel Approach for Harmonic Assessment of Power Systems With Large Penetration of IBRs – A U.K. Case Study

This work provides a high-level assessment of the harmonic performance of the future U.K. power system with high penetration of Renewable Energy Sources (RESs). A few variations to the standard harmonic analysis are proposed to allow for a more accurate representation of Inverter-Based Resources (IBRs) in frequency-domain studies. In the first part of the paper, two reduced network models (for 2020 and 2050, respectively) are developed, including both transmission and distribution system representation. A frequency-dependent impedance model for individual and aggregated IBRs is adopted, and a novel distribution load model with harmonic injection is proposed. Additionally, the variability of harmonic phase angles is modelled taking into account the physical behavior of the IBRs. Probabilistic Harmonic Load Flows (PHLFs) are carried out on the reduced networks by varying the harmonic injection magnitudes and phase angles of each harmonic source. This work shows that, while overall harmonic levels are dependent on the changes in demand, the inverter impedance has significant impact on local resonances, and accurate models for IBRs are required.