A Real-Time Resistance Based Fault Detection Technique For Zonal Type Low-Voltage DC Microgrid Applications

A fault detection method for a photovoltaic-based low-voltage dc microgrid (LV-DCMG) system is presented in this article. Unlike the conventional ac system, the dc system offers more challenges in the protection in real-time. In addition to this, many of the conventional ac protection such as distances relays, overcurrent relays, and differential relays based methods may not be used for the dc systems. This article gives more emphasis on the resistance-based fault detection for communication network less DCMG applications. The key advantages of this method are fast fault isolation, communication network less protection, good fault selectivity, better flexibility in implementation, and low protection cost. To achieve this goal, a zonal-type of dc system is considered, where the loads are connected through the dc cable and solid-state relays (SSRs) with their segmented controllers. A line-to-line short-circuit (SC) fault is introduced in the system for multiple time to check its dependability. The proposed concept has been verified by MATLAB/Simulink digital simulations and a TMS320F28335 DSP-based scaled-down LV-DCMG experimental setup. The results show that faults can be isolated from the healthy grid within a few milli second, and this isolation time is very less than the time available in the literature. A detailed study on the transient and steady-state response of the SC fault is also incorporated.