Protection of low-voltage DC microgrid based on series R–L–C equivalent circuit utilising local measurements

摘要

The adoption of low-voltage DC microgrid at a large scale is hindered by the lack of an effective protection scheme. This work proposes a dedicated protection scheme based on multi-threshold current values, which enhances the security of the system by avoiding the risk of false tripping. This is achieved in a few milliseconds without losing the deadline of critical fault clearing time post, which the voltage sources converter interfaced power sources may get disrupted leading to de-energisation of the system. The algorithm relies upon the transient response of the series resistor-inductor-capacitor (R-L-C) equivalent circuit having initially charged filter capacitors. The threshold values of the fault current for each protection device at every network node are set locally by considering the weakest fault criterion. The extensive simulation study has been performed on MATLAB/Simulink for validating the reliability of the proposed algorithm under heavy load transient, at different fault locations, and with high fault resistance.