A topology of multi-functional grid-connected inverter is proposed and applied to a microgrid. It can compensate harmonic， unbalance and reactive currents of microgrid at the same time. A corresponding controller based on weighted current feedback and hysteresis current loop is also given. Furthermore， an approach to detect compensative current and calculate reference current is given with synchronous rotating frame， which can remove phase lock loop. Finally， PSCAD/EMTDC is used to verify and confirm the proposed methods. The simulation results validate its good performance. It can not only enhance the power quality of microgrid， but also can regulate the power flow between microgrid and utility grid， which can aid the utility grid with necessary active or reactive power.