To the isolated microgrid, the main cause of the unbalanced voltage is the three-phase unbalanced load. In this paper, a sequence control scheme for a three-phase four-leg inverter is proposed. The control strategy is mainly based on the modified linear active disturbance rejection controller (LADRC). The modified linear extended state observer (LESO) is designed to estimate the value and differential value of total disturbance, which can significantly reduce the estimated error of total disturbance. The frequency and time-domain analysis show that the modified LADRC has better disturbance rejection ability. The simulation results testify the disturbance rejection effect.