The undesirable harmonic distortion produced by distributed generation units (DGUs) based on power electronic inverters presents operating and power quality challenges in electric systems. ‡e level of distortion depends on the internal elements of the DGUs as well as on the characteristics of the grid, loads, controls, among others. ‡is paper presents a comprehensive method, focused on power quality indexes and e�ciency for the design of micro-grids with multiple DGUs interconnected to the AC grid through three phase multi-Megawatt medium-voltage PWM voltage source inverters (PWM-VSI). ‡e proposed design method is based on a least square solution using the harmonic domain modeling approach to e‚ectively consider explicitly the harmonic characteristics of the DGUs and their direct and cross-coupling interaction with the grid, loads and the other DGUs. Extensive simulations and analyses against PSCAD are presented in order to show the outstanding performance of the proposed design approach.