Influence of PLL Techniques on Immunity Tests and Islanding Detection of an Inverter-Based Generator

Distributed Generation (DG) reached levels of more than 23 GW in Brazil in Sep. 2023, raising concerns about islanding detection and undesirable disconnections. Inverter-based generators (IBGs) must comply with immunity and islanding tests according to technical standards. This study evaluates the impact of three types of Phase-Locked Loops (PLLs) on IBGs, with passive Unintentional Islanding (UI) detection techniques and the active technique General Electric Frequency Scheme (GEFS), using time-domain signal analysis and settings map. It examines whether IBGs with these PLLs may fail to meet immunity and is-landing detection requirements. It is identified that PLL techniques significantly influence immunity tests, requiring precise time delay on protection functions if Rate of Change of Frequency (RoCoF) protection is enabled.