The present disclosure provides a three-phase AC system and a control method thereof. The method includes: receiving an output signal of the three-phase AC system and obtaining a characteristic value of the output signal according to the output signal; performing virtual synchronous generator control on the inverter to obtain a fundamental electric potential; extracting a harmonic component from the output signal and obtaining an error signal according to the harmonic component and a reference value of the harmonic component; controlling the error signal to obtain a harmonic compensation electric potential; obtaining a control electric potential by superimposing the harmonic compensation electric potential with the fundamental electric potential; obtaining a pulse signal by modulating the control electric potential, and obtaining a switching signal of the inverter according to the pulse signal.