Sizing and SOC Management of a Smart-Transformer-Based Energy Storage System

A smart transformer (ST), which is a power-electronic-based transformer with control and communication functionalities, can be the optimal solution for integrating a battery energy storage system (BESS) in an electric distribution system. In fact, a comparison of energy efficiency for the conventional BESS and the ST-based BESS is carried out, which demonstrates that the ST-based BESS operation is more efficient during charging and discharging, as compared to the conventional BESS. It has been shown that by sizing the BESS appropriately for the peak load demand, the power rating of ST converters can be reduced. The ST-based BESS provides an enhanced fault ride-through capability, as compared to the conventional BESS. However, the state of charge (SOC) of the BESS shall be correctly managed to support the peak load demand when the ST converter reaches its maximum active power rating. Both simulation and experimental results clearly verify the developed SOC management.