Research on Active DC Islanding Detection Method Based on Lock-In Amplifier

For modern distribution networks, detecting unconscious islanding presents a major challenge. The typical active islanding detection approach involves injecting a disturbance signal, which degrades the power supply quality and creats a problem of synchronously injecting the disturbance. In this paper, an active DC islanding detection method using a lock-in amplifier (LIA) is proposed. When the power difference is less than a particular threshold, a weak disturbance signal is injected into the distributed power supply, causing the voltage at the Point of Common Coupling (PCC) fluctuate at the same frequency. A LIA is used to detect the small fluctuations for identifying the isolated island. This method can not only prevent the incorrect action of injecting disturbances in a normal state but also ensure the synchronization of disturbance injection, effectively improving power supply quality. Finally, the effectiveness of the method is verified by simulation.