A Negative Sequence Element for Fault Detection in Inverter-Interfaced Microgrids

Directional protection has been employed for many years in transmission and distribution networks to achieve the required secure and selective protection. It also offers great potential for dealing with the unique problems introduced in inverter-interfaced microgrids. The control methods used in inverter-based distributed generation (IBDGs), introduce further challenges that affect fault detection in microgrids. This paper reviews the influence of inverter control on fault conditions and proposes a directional method for detecting unbalanced faults in a microgrid, using negative sequence admittance. This approach provides a sensitive and selective option for the protection system. The method is compared with the existing negative sequence-based directional protection methods. Results from simulation studies are used to verify its effectiveness.