Distributed Islanding Detection in Multisource DC Microgrids: Pilot Signal Cancelation

Abstract

Integrating Distributed Generators (DGs) in DC microgrids require islanding detection in all converters. Impedance-based islanding detection methods can be beneficial in single-converter scenarios. However, their implementation in multi-converter systems is challenging due to interference among DGs. This paper proposes a Leader/Follower strategy for each active participant of the DC microgrid to independently detect the grid connection state. While the Leader injects a small AC pilot signal to estimate the impedance at its terminals, the Followers implement the proposed pilot signal cancellation (PSC) to present a virtual disconnection from the bus at ωp. This leads to two core benefits: the Leader does not receive interference from the input impedance of the followers yielding accurate islanding detection for the Leader, and the followers can detect the islanding condition independently, with no need to increase the PSC amplitude. The proposed method provides independent and simultaneous islanding detection for all active participants in the DC microgrid. At the same time, it is scalable by the number of parallel-converters, not requiring any communication. Finally, the method has a minimal effect on the bus voltage.