DC fault dynamics in a VSC based MVDC shipboard distribution

The U.S. Navy is investigating use of medium-voltage direct current (MVDC) for shipboard electrical distribution. MVDC architecture has the possibility of fault detection and response that is faster than comparable AC (MVAC) systems. Theoretical MVDC response times are on the order of 1-5 μs. The feasibility of 5 μs for fault detection and mitigation in a shipboard MVDC system is evaluated analytically and with simulation. Voltage source converter (VSC) technology is used for the AC-to-DC conversion and both single and multi-terminal VSC topologies are simulated. The study identifies reasons for delay in DC fault detection and response. Mitigating options and tradeoffs are also studied. It is concluded that the VSC system selected for this project is not likely to achieve a 5 μs detection and response time due to constraints imposed by passive circuit elements. However, results indicate that satisfactory fault performance may not require such a rapid response.