Enhancing the protection of photovoltaic-based DC microgrids using circuit breaker operation sequence

• A scheme is proposed to enhance PV-based DC microgrid protection through the CB operation sequence. • The proposed method is applicable in both grid-connected mode and islanded mode. • The suggested approach identifies both permanent and temporary faults, serving additionally as backup protection. The advancement of direct current (DC) microgrids is limited by insufficient operational experience, the inadequacy of suitable protective devices, and the absence of effective fault analysis methods. The complexity of DC microgrid protection is heightened by their various operation modes, such as grid-connected and islanded modes. Additionally, the identification of both permanent and temporary faults, as well as the distinction between faults in the primary zone of a transmission line and those occurring in busbars or adjacent lines, complicates the protection of DC microgrids. This paper presents a novel sequence for circuit breaker operations aimed at enhancing the performance of a photovoltaic-based DC microgrid protection system, with an emphasis on communication-based strategies. The proposed approach involves the implementation of a protection logic for overcurrent (OC) relays, along with an operation sequence for DC circuit breakers. By adopting this method, the microgrid can achieve selective protection, ensuring system reliability and security. Using only locally measured current samples, the proposed approach eliminates the need to configure separate setting currents for the primary and backup zones. Additionally, both zones are protected with the same time setting. The effectiveness of the proposed method is verified through simulation results on a typical DC microgrid. In the modeling analysis, both permanent and temporary faults are considered across different DC microgrid configurations. During the simulation, several test cases were implemented to evaluate different fault conditions in the DC microgrid. The proposed algorithm performed correctly in all test cases.