Modeling and Design of the Inner Control Law of a Three-Phase Grid-Forming Inverter Operating Under the Droop Strategy

Abstract

This work aims to design the internal control loop of a grid-forming converter, as well as demonstrate the stability of the system through the eigenvalues of the state space equation of the complete system. The developed method consists of designing the control loops separately, taking into account the influence of the PWM, the dynamics of the current control for the design of the voltage loop, that is, without using simplifications in the design that can lead the system to instability. The analysis of the performance of the designed system is done using simulation tools such as: Matlab/Simulink and the real-time simulation platform OP4500 in Hardware in the loop to verify if the system is stable and if it is capable of tracking the imposed references. The results obtained make it clear that the designed system is stable observing the eigenvalues obtained from the complete system and also by simulation that analyzes if the controllers are capable of tracking the references. In addition, the behavior of the system in steady state is analyzed to verify if the system is in fact stable. Therefore, the present work fulfills the objective of developing a method for calculating the internal network gains of the network-forming converter and ensuring the stability of the system through the state space equation and simulation of the complete system.