Islanding classification and low-voltage ride through for grid connected transformerless inverter

This research paper proposes a control technique for grid connected photovoltaic (PV) systems that provide fault-ride-through (FRT) capability by adhering to the grid codes. The proposed control system adapts neural network for grid fault detection and achieves the FRT requirements by operating according to the grid connection standards. Further, the proposed controller injects required reactive current for change in the voltage at the point of common coupling (PCC). During a fault, when the active power of the grid connected photovoltaic system (GCPVS) decreases, the proposed algorithm permits injection of reactive power into the grid. The functionality of the proposed control strategy is verified by performing simulation tests on a 4 kW GCPVS by adhering to the FRT requirements which support FRT for asymmetrical and symmetrical faults. The results ensure that the proposed control system adheres in injecting more than 2% reactive power for every 1% change in active power within 7 ms upon detection of fault.