Shunt Resonant Solid-State Circuit Protection for No Delay Coordination and Less Inductive Fault Limitation in Compact MVDC Systems

Due to the extremely high di/dt rate of the compact Medium Voltage Direct Current (MVDC) systems during line-to-line fault, achieving selective coordination between circuit breakers in the systems presents a significant challenge. Traditional Time-Current-Curves (TCCs) based coordination methods require delays which lead to substantial fault current increment and aggravate post-fault repercussions. Some previous methods utilize di/dt sensing to enhance coordination speed but can incur mis-tripping due to their susceptibility to noise. Alternative approaches rely on current-limiting inductors to extend the coordination time window, but at the cost of lower power density and longer fault duration. To tackle this coordination issue in MVDC, this paper has proposed a shunt resonant solid-state circuit protection that automatically limits fault current and advances protection-tripping instant when a line-to-line fault happens. With the proposed method, the selective coordination between upper and lower stream circuit breakers can be attained using basic TCC methods without worsening the fault’s effect. Furthermore, compared to conventional inductive fault limiting methods, the proposed shunt resonant circuit demonstrates better current limiting efficacy with smaller inductance along with faster fault isolation speed. The operating principles and features of the proposed circuit protection have been validated through simulation and test.