The present invention discloses a grid-connected inverter and a method for filtering AC output thereof. The grid-connected inverter comprises an AC output filter (40) which includes two or more switchable filtering modules (110, 120), power capacity of each filtering modules corresponding to a different output power of the grid-connected inverter; a monitoring module (50) which is used to perform realtime monitoring on voltage and current outputted by the grid-connected inverter; and a control circuit (60) which is used to calculate an output power grade of the grid-connected inverter according to the voltage and the current monitored by the monitoring module and control switching to the filtering module having a corresponding power capacity according to the power grade, the power grade being selected from a plurality of power grades which are divided according to power capacities of the filtering modules (110, 120). With the present invention, total harmonic distortion (THD) of the output current waveform of the grid-connected inverter can meet the requirements of relevant standards, and conversion efficiency of the grid-connected inverter in the case of a low load factor can be improved.
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