INVERTERS CURRENT FREQUENCY DEVIATION BASED ISLANDING DETECTION IN GRID CONNECTED PHOTOVOLTAIC SYSTEM

The protection schemes of distribution systems are usually designed under the assumption that power flows from t he substations to the end users.The utility system contains both load and generation in which part of the system is isolated from the rest of the system is the islanding condition. Power - quality problems, interference with grid protection devices, equipmen t damage, and even personnel safety hazards are the causes of unintentional islanding.In the proposed method, the q - axis current in the inverter is measured and the current controller is modeled with a continuous periodic Reference power from a small value . The possibility of false detection is eliminated through the affirmation of the occurrence of islanding as soon as it is suspected. DG is a islanded from the upstream system, if the frequency variation is occur in a small value due to a change in the inv erter current. The proposed algorithm detects the island grid formation in the stable condition of the system. Computer simulation is done with MATLAB