Passive islanding detection approach for inverter based DG using harmonics analysis

The accretion or demand of distributed generators (DG) have significant or meaningful operation along with the electric power system; the organize way to reassure the proper operation of the power system along with the DG set, more and more variables and constrain have to be predefined and controlled. Formation of islanding phenomenon is one of the major issued problem confronted with this kind of power generation scheme, in which DG source may keep working in a stable or normal way even if main electric power system (EPS) has failed. There are various methodologies have been evolved and advanced to avert this situation. They are classified as detection through passive method, active and communication systems based method. Islanding occurrences is the most issued problem in a recent time power system working along with the DG. A variety of problems occur when a solar Photovoltaic is working as distributed generated (DG) source. Islanding refers to a condition when a DG source continues to supply power to a load even though there is no power from the main source during the disconnection from the main grid at the occurrence of fault or some other severe phenomenon, refers to a situation or condition called islanding. When workers who may not perceive that the load is still powered after the disconnection from the EPS or main source so this condition can be dangerous to the grid workers. When this condition occur the DG source should gets immediately disconnected from the local load in minimum time delay. Islanding causes unfavorable effects which are low power quality, personnel potential danger, grid-protection interference and equipment damage. Islanding can causes very dangerous or abnormal situation for both people and apparatus, So islanding should be quickly determine by inverters and protective relays. Islanding finding out through passive method examines system specification without inducing any interruption and disturbance into the grid (EPS). In this proposed paper the detection is based on distortion of output voltage, it measures Rate of Change of Frequency (ROCOF) or frequency jump, Rate of change of voltage (ROCOV) at the Point of Common Coupling and detection by voltage unbalanced factor to reduces the non detection zone (NDZ).