This abstract outline a proportional-integral (PI) controller and direct-quadrature (DQ) frame-based optimal control method for a three-phase grid-connected inverter using a MATLAB simulation. This is an open access article under the CC BY-SA license. . However, most 3-phase loads are connected in wye or delta, placing constraints on the instantaneous voltages that can be applied to each branch of the load. For the wye connection, all the “negative” terminals of the inverter outputs are tied together, and for the detla connection, the inverter. . Three-phase power systems consist of three sinusoidal voltages, each offset by 120° from the others. The instantaneous voltages can be expressed as: where Vm is the peak voltage amplitude, ω is the angular frequency (2πf), and t is time. In terms of grid synchronization, voltage regulation, and harmonic abatement, the proposed control technique attempts. . This research paper investigates the implementation of a grid-connected three-level F-type inverter with dq frame control, specifically tailored for three-phase systems. Compared to traditional two-level inverters, the pro- posed inverter architecture leverages a three-level configuration to. . Abstract— In this paper a three-phase four-leg voltage source inverter operating in island mode is described. The four-leg inverter is implemented by using a delta/wye or ZigZag transformer to meet isolation requirement. The control scheme includes an inner current loop providing the capability of. .