Two islanding detection circuits based on the impedance variation for the micro-grid

In the transition of the micro-grid operating-modes, the islanding detection is extremely essential. To guarantee smooth transition of the modes, the method should be able to detect the occurrence of islanding state reliably and quickly. Simultaneously, it should avoid the negative impact effectively on overall stability. The paper presents a way able to detect the occurrence of the islanding condition according to the voltage peak to peak value change near the Point of Common Coupling (PCC) corresponding to the equivalent system impedance variation between connected with the main grid and the islanding operation. It presents two kinds of electric circuits to realize the function, and has carried on the corresponding analysis of their performance in Micro-grid Model, which is constituted by some loads and micro-sources with inverter interface or machine interface. It carries on the modeling simulation verification under Matlab/Simulink and has confirmed this principle validly.