Application of Multi-Level Converter for Fast Current Control in Small-Scale DC Power Network

DC microgrids have been emerging as next-generation small-scale electric power networks, where the line impedance is very low. This phenomenon causes large currents in the microgrids, even for a slight change in voltage; therefore, it is critical for a power flow controller to have faster transient response and precise power flow control. In this study, multi-level converters are applied as the power flow controllers to realize high-speed and high-precision power flow control in a dc microgrid. The output filter can be small, as a multi-level converter is used. This paper also presents the design of the output LC filter of a multi-level converter to satisfy a requirement of current ripple. We experimentally verified that a multi-level converter with a smaller filter can realize high-speed and high-precision power flow control for low line impedance conditions compared with the conventional two-level converters.