Principal Investigator: Dr. Alan Mantooth
This project involves the design and construction of a SiC-based direct power electronics interface for a battery energy storage system (BESS), which is to be integrated into a 13.8 kV medium-voltage distribution system. Normally, to interface a BESS to a medium-voltage distribution line, a step-up transformer is required to boost the inverter ouput voltage. The use of the transformer provides convenient isolation, however using a transformer to meet medium-voltage inverter insulation requirements leads to substantially higher leakage inductance, increased switching losses and limited transformer power transfer capability.
Recent advances in high voltage power semiconductor devices, medium-voltage (>10 kV) SiC power modules present an opportunity to realize a transformerless interface, shown in the Fig.1 below. Transformerless topologies, and the use of wide bandgap devices, have the potential for reducing cost and size of passive components for the medium-voltage inverter. To satisfy the medium voltage basic insulation level (BIL) requirements for the power electronics interface, modular multilevel cascade (MMC) inverters provide a better solution. This battery energy storage system interface will also include fault protection circuitry and communication protocols. The performance of the control algorithms for a BESS equipment will be tested through an experimental prototype at the National Center for Reliable Electric Power Transmission (NCREPT) using the 13.8 kV distribution system.