This paper proposes appropriate analytical expressions for a deadbeat control system to be implemented in the output inductor–capacitor–inductor (LCL) filter of a gridconnected inverter. Unlike in a conventional analysis, the proposed control algorithm with a settling time of three sampling periods is derived from the system transfer function in the discretized time domain instead of the Laplace s-domain. Furthermore, when introducing the deadbeat control, the independent control of the integrated active power and that of the reactive power are also made possible. The experimental results of the proposed deadbeat control system indicate that the feedbacks from both grid and inverter currents have similarly high capabilities in attenuating switching frequency components and damping resonance. Such proficiency is brought about because the remaining two undetected control variables of the LCL filter are taken as estimates in the DSP when introduced to the state observer. However, feedback from the grid currents can be seen to significantly reduce the total harmonic distortion of the actual grid currents themselves.