Modeling and Design of Primary Control’s Inner Loops for Droop-Controlled Three-Phase Inverters within a Microgrid System

in Microgrid (MG) systems, the output voltage controller within the primary control, called the “inner control is essential for regulating the output of the inverters and guaranteeing a high-stability operation. This paper addresses the modeling and design of the primary control’s inner loops intended for voltage-controlled three-phase LC-filtered inverters forming an islanded MG. The designed inner controller is a dual-loop control structure, consisting of outer voltage and inner current control loops, implemented in the dq$\theta-$frame. Each control loop includes three PI controllers for the direct, quadrature, and DC (zero) components regulation. The modeling of the voltage-controlled LC-filtered inverter, as well as the voltage/current inner control loops in the dq$\theta-$frame, is provided. The tuning of the controllers’ parameters is done with the help of a developed straightforward and efficient design approach. Simulations are carried out in MATLAB/SimPowerSystem environment. The findings reveal that the designed inner controller for output voltage tracking is effective, with high performance in both steady and transient states, under a variety of operating conditions.