In the grid-connected photovoltaic (PV) system, a two-level inverter will inject harmonic components into the
power system. Therefore, a harmonic filter is required. However, the determination of filter sizing is difficult because the
amplitude of harmonic components is changed along with the change in the output power of the PV system. Sometimes,
the total harmonic distortion (THD) of voltage or current is over the expected value. Consequently, this paper proposes
the use of a modular multilevel converter (MMC) for a grid-connected PV system instead of a two-level inverter. The
objective is to ensure that the THD of voltage or current is always below the standard value. The simulation results are
performed in the PSCAD/EMTDC simulation program to verify the effectiveness of the MMC.