Adaptive differential relay coordination for PV DC microgrid using a new kernel based time-frequency transform

A discrete differential current based unit protection and fault distance estimation is proposed for a 100 kW Photovoltaic (PV) based Multi-Terminal Direct Current (MTDC) microgrid. Relay coordination and adaptive relay settings are presented in terms of PV arc and DC cable faults. To distinguish PV arc and DC cable faults without nuisance tripping event, an improved energy density based time-frequency transform is presented in this paper. A new frequency filtering Kernel based Discrete Time Frequency Transform (KDTFT) is proposed for effective fault detection. DC microgrid protection is essential area to be research focus due to lack of precise grid codes/standards. Pole-pole (PP) and pole-ground (PG): positive/negative faults are the most counted operational threats for DC microgrids. As PV is considered to be integrated as primary DG via DC cables, highly resistive DC arc faults (series, parallel: cross-string, intra-string) are also focused in this paper. The independent PV arc protection is designed as backup to arc-fault circuit interrupters (AFCIs). The efficacy of proposed protection measure is considered in terms of percentage error for fault distance estimation and Circuit Breakers trip time (Ts). The adequacy study is presented while considering DC load diversity.