Economic Implementation of 99.98% Efficiency in Natural-Cooling Modular MVDC SSCBs

This article presents a modular medium voltage direct-current (MVdc) solid-state circuit breaker (SSCB) with high efficiency. The presented design method is modularity oriented, which includes thermal analysis of conduction cell, busbar design of conduction disk, and structure design of conduction tower. The implementation includes both continuous current conduction and fault current interruption. This article includes three major contributions. First, it presents an economic analysis in terms of efficiency and cost as the design guideline for the main conduction configuration of SSCBs. Second, it provides a complete modular SSCB design procedure, showing both parallel and cascade scalability. Third, this article investigates the effect of main conduction path stray resistances on SSCB efficiency and power loss. A medium-voltage SSCB prototype rated at 4 kV/100 A is experimentally implemented. The power density achieves 26.2 kW/L. The continuous conduction tests are conducted at 100 A for 1hour, the steady-state efficiency achieves 99.98% with maximum temperature of 37 °C. The fault interruption tests are successfully conducted at 4 kV/137 A and 4 kV/1 kA with different system inertia.