Continuous Operation of Smart Transformer-fed Distribution Grid with Single-phase Faults

Solid-state transformer-based Smart Transformer (ST) allows integrating energy storages and electric vehicle charging stations, while offering ancillary services to electric grid. The continuity of service in power supply as a basic requirement for the electric grid operation is threatened and interrupted by grid faults in the conventional distribution transformer (CDT)-fed electric grid, but can be ensured by the ST. Unlike the CDT, the ST can switch from three-phase operation mode to two-phase operation mode, ensuring continuous power supply in two healthy phases and reducing outage area, during single-phase to ground faults (SFGFs). An improved voltage control strategy is proposed to balance the power losses reduction in neutral conductor and voltage oscillation suppression in DC-link during two-phase operation mode. This paper focuses on the performances design of ST voltage control during the two-phase operation mode to improve the grid voltage transient performances. The simulation and experimental results clearly verify the effectiveness and correctness of the proposed strategy.