Improved LVRT grid code under Islanding condition

The grid code Low Voltage Ride Through (LVRT) requires Renewable Energy Sources (RESs) to remain connected to the grid following the voltage sags resulting from disturbances. The LVRT pattern is based on voltage sag magnitude and its duration at Point of Common Coupling (PCC) and only voltage reflects the internal dynamics of RES. Therefore, making decision on RES connectivity to the grid just relying on one variable, i.e. voltage, may not be the best decision for wide range of possible combinational and cascading events leading to islanding. This paper proposes a novel LVRT characteristic in which all of applicable and determinant variables of RES are considered. If the RES safely and securely operates inside continuous operating range of rotor speed and current, the grid voltage and current, the RES interruption is diffidently avoided to keep supporting of power system.