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 insulated-gate bipolar transistor (IGBT) based 2-level converter and its advantages are highlighted. A phase-shifted sinusoidal pulse-width modulation (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.