Simplified protection algorithm for fault detection and localization in DC microgrid

• Published in: Electric power systems research 2022-10, Vol.211, p.108229, Article 108229
• Main Authors: Nageswara Reddy, Nareddy, Velpula, Rajesh, Raja, P., Moorthi, S.
• Format: Article
• Language: English
• Subjects: DC microgrid protection; Directional comparison scheme; Estimated inductance; Fault detection; Frequency of oscillation
• ISSN: 0378-7796
• DOI: 10.1016/j.epsr.2022.108229

In a microgrid, conventional overcurrent and current direction based protection techniques have limitations during high resistance faults. Besides, ring configuration microgrids offer bidirectional power flow rather than unidirectional power flow. Moreover, DC microgrids own low line resistance and high DC link capacitance; it results in an immense increase in current. During fault conditions, it may cause an undesirable disconnection of resources and make the system unreliable. An accurate and fast operating protection strategy is needed to explore and achieve the above mentioned challenges. To start, with the difference in consecutive current sample data, the current difference index has been evaluated. The non-zero index is granting the estimation of frequency using natural characteristics of fault current, which correctly discriminates an incipient fault and sudden switching loads. Thereafter, by adopting local voltage and current samples during the fault, estimated inductance has been exploited, which possesses polarity and magnitude to isolate the fault and identify the fault position, respectively. The proposed method genuineness for numerous cases like low and high resistance faults at various locations, including close-in faults, bidirectional power flow, different load conditions, and other configurations is validated in MATLAB/Simulink environment. This method precisely estimates fault location under the aforementioned cases. A comparative study of the proposed scheme with existing protection methods has been carried out, proving that this method is more accurate and enhances the relay dependability. •The non-zero value of current difference index triggers the fault detection algorithm.•The estimation of frequency is adopted to discriminate fault inception, load change.•The estimation of inductance is used to isolate fault line and to find fault location.•The proposed protection algorithm works effectively even during high resistance fault.•Comparative study of proposed method with the methods in literature has been done.