THD-Based Passive Islanding Detection Technique for Droop-Controlled Grid-Forming Inverters

This article proposes a total harmonic distortions (THD)-based passive islanding detection technique (IDT) to overcome the challenges in droop-controlled grid-forming inverters (GFMI). The conventional IDTs are ineffective in GFMI due to the impact of power control droop parameters on the nondetection zone (NDZ). Also, the active IDTs may cause disturbances in the working operation of the GFMI due to their opposite functionality. Thus, there is a need to develop adequate IDTs which can perform robustly even with unconventional droop parameters and helps in maintaining the GFMI functions. In this work, THD from the rms voltage and current at the point of common coupling are extracted using the fast Fourier transform analysis. Then, a novel islanding detection factor (IDF) with adaptive weights is calculated. Finally, the statistical feature extracted from the IDF is compared with the threshold value to detect islanding. The performance of the proposed IDT (P-IDT) is analyzed with an real-time digital simulator (RTDS) simulator in a developed RSCAD distribution system. The real-time (RT) performance validation of the P-IDT is executed with the RSCAD (Real-Time) software IEEE-13 node system and RT-LAB (Real-Time) software. The RT results for different islanding and nonislanding scenarios show the efficacy of P-IDT.The proposed method is superior in accuracy and detection time as compared to the other conventional techniques.