Novel bidirectional symmetrical Z-source breaker with adjustable turns ratio of coupled inductor

• Published in: Electric power systems research 2023-08, Vol.221, p.109420, Article 109420
• Main Authors: Durgaprasad, Ande Venkata, Mitra, Arghya
• Format: Article
• Language: English
• Subjects: Circuit breaker; Coupled-inductor; DC microgrid protection; Fault analysis; Step load
• ISSN: 0378-7796; 1873-2046
• DOI: 10.1016/j.epsr.2023.109420

•The proposed topology (NBi-SZSB) isolates a fault from the source in 10 µs.•The maximum allowable load current can be set in the NBi-SZSB, during step load change by adjusting the turns ratio.•The topology has a reduced inductive value and with the presence single SCR during a normal conduction, it results a drop in the power loss.•The proposed topology (NBi-SZSB) reduces the starting current flows through SCR during reclosing process.•The effectiveness of the proposed breaker (NBi-SZSB) is validated through hardware prototype testing. Bidirectional Z-source circuit breakers (Bi-ZSCBs) have several benefits when they use SCR as the main switch. A few such benefits are low conduction loss, low cost, and high ruggedness. However, these Bi-ZSCBs are unsymmetrical in nature during power flow in both directions. Also, the coupled inductor-based Bi-ZSCBs may mal-operate while changing the turns ratio during different loading conditions. In order to avoid these drawbacks, a Novel Bidirectional Symmetrical Z-Source Breaker (NBi-SZSB) is proposed, which can operate symmetrically during power flow in both directions by proportionally adjusting the coupled inductors turns ratio. The working principle, parameters design, frequency analysis, power loss, the effect of source inductance and the effect of line impedance are analysed in this study. In addition to this, the maximum allowable load current can also be set in the NBi-SZSB, during step load change by adjusting the turns ratio. It may be observed that the proposed NBi-SZSB exhibits isolation of line-to-ground and line-to-line faults with fault isolation time in the range of 10µs, zero reflection of source fault current, and reduced soft starting current. The effectiveness of the proposed breaker is verified through both simulation and hardware results.