Island detection is one of the frontier issues in the field of distributed grid. Aiming at the problem of large non-detected zone in traditional passive detection method

the control algorithm of current non-detected zone passive detection method is too complicated

by analyzing the principle of frequency tracking in closed-loop frequency-locked control

the high-frequency impedance characteristics of grid-connected inverter controlled by closed-loop frequency-locked control are studied. By discussing the load impedance characteristics of various islanding conditions

a new passive island detection method is proposed

which uses the output frequency of the closed-loop frequency-locked control method directly

preventing the occurrence of the island by adding high-frequency impedance detection. Simulation and experimental results show that the passive island detection method proposed is able to detect the inverter disconnection situation quickly and accurately

can also eliminate non-detection zone

and avoid the complicated problem of control algorithms.