Thermal Capability Estimation of Power Devices in Smart Transformer under Line-to-Line LVAC Grid Fault

The Smart Transformer (ST) arises as one promising solution for the modern electric grid by providing ancillary services to support AC and DC distribution grid. In this context, like the conventional transformer (CT), the ST is prone to experience overload conditions caused by faults and load currents due to start-up transients. However, unlike the CT, which is essentially composed of copper and iron, the overcurrent capability of the ST is limited by the thermal capability of the power devices. This limitation reduces the maximum fault currents and hence the effective operation of the power system protection. Therefore, the thermal capability of the LVAC 2L-inverter is required to assess the overcurrent limits during fault conditions. This paper presents an analysis considering asymmetrical faults in an LVAC grid which are equivalently modeled in a MIMO system with a particular focus on the fault current and power factor values.