Three-phase bidirectional AC/DC converter acts as a key part in DC microgrid. To improve the stability of DC bus voltage for the grid-connected mode in DC microgrid, a sliding mode or PI controller based on SVPWM modulator is designed for the bidirectional AC/DC converter in inverter mode. When the error between grid-connected current reference value and actual value is larger than the threshold value, the sliding mode controller is used. Otherwise, the PI controller is adopted. The great grid-connected current reference value fluctuation is simulated in PSIM software when the DC microgrid operates in the grid-connected inverter mode. The simulation results show that the gird-connected current actual value can fast track with the reference value. Then the dynamic response performance of DC bus voltage is improved.