Recognition of islanding data for multiple distributed generation systems with ROCOF shore up analysis

Abstract

In this paper, a new hybrid islanding detection method is presented for protecting the distributed system with unintentional islanding, with low-frequency current harmonic injection and over/under frequency relay for inverter-based multiple distributed generation (DG) systems. Low-frequency current harmonic component is injected into the system through the q-controller of the grid-side controller. The injected low-frequency current component causes the system frequency to deviate during islanding. This deviation separates islanding and non-islanding events. This paper evaluates the performance of this hybrid ROCOF relay when load and generation are matched and also at different active power imbalances. This paper will also clearly differentiate between islanding and non-islanding conditions for mixed types of DG’s connected to the grid. The test system results are carried out on the MATLAB/Simulink setting that shows the strength of this technique.