An investigation of high efficiency DC-AC converters for LVDC distribution networks

Low voltage DC (LVDC) distribution systems offer improved efficiency and reliability in smart grids. A major challenge facing LVDC systems is DC-AC conversion. A study of an effective low voltage DC-AC converter is therefore presented. Modular Multilevel Converter (MMC) performance (in particular power loss) is compared with a conventional IGBT-based 2-level converter and its advantages highlighted. A phase-shifted sinusoidal PWM based individual voltage balancing strategy for the MMC is presented. A proportional-resonant controller is introduced to eliminate the 2nd harmonic circulating current in the H-bridge MMC converter.