In this paper, the concept of grid-connected inverter without interfacing filters is proposed. Conventional grid-side voltage sensors and traditional phase-locked loop (PLL) are removed. Only the grid current is feedback to implement grid synchronization and decoupled P/Q control. 60-Hz sinusoidal output current is achieved relying on grid-side impedance only. The controller employs virtual impedance to couple with a wide range of grid-side impedance variations. With the proposed controller, the grid-connected inverter is capable of 1) decoupling the output real and reactive power; 2) synchronizing with a grid frequency fluctuation, and 3) tolerating the grid impedance variation. This paper addresses the principle of the proposed method. Multiple simulation results are provided for validation.