Fault Detection, Isolation, and Estimation for a Three-Phase Grid Connected DC-AC Inverter With LCL Filters

This letter is dedicated to symmetric and asymmetric fault detection, isolation, and estimation of a three-phase DC-AC (Direct Current-Alternating Current) inverter connected to the grid by three LCL filters. The system modeling and the faults estimation algorithm are performed in the abc frame allowing to take into account phase by phase asymmetrical faults. It is based on a left inversion technique and uses the super-twisting differentiator in order to estimate the state components of the system from the given measurements. Simulations to support the proposed approach are presented.