Controle preditivo baseado em modelo aplicado à conversores eletrônicos para transição suave entre modos ilhado e conectado à rede

Abstract

A microgrid can operate both as an island and connected to the main grid. In order for a microgrid to operate in these two modes, it is essential to have adequate transition control and it is very important that this transition is made in a continuous and smooth way. The transition takes place at the moments of connection and disconnection of the microgrid with the main grid, where problems such as overvoltage transients, undervoltage and signals of varying frequencies present in the electrical signal can occur. Making this transition smooth means that these negative effects are avoided so that there is no interruption of electricity supply or greater damage to loads or other converters. This work presents the use of Model-Based Predictive Control with Finite Control Set (FCS-MPC) and multivariable cost function as a control methodology, and the use of a virtual resistor so that both are able to contribute to the smooth transition between the islanded mode and grid-connected mode of a single-phase grid forming converter (CFR). In addition, the converter’s control strategy uses a Tuned Adaptive Filter (FAS) to perform the functions of a Phase Locked Loop (PLL) and a step of synchronism with the main electrical grid. Together with FCS-MPC, FAS aims to ensure a smooth transition during connection or reconnection when the main grid is restored after failure. On the other hand, the same adaptive filter is used to estimate voltage amplitude and frequency at the Common Coupling Point (PCC), which are monitored by an islanding detection algorithm, and define whether or not there is an islanding condition. The grid forming converter and its control algorithms are simulated in a virtual environment with the software Matlab/Simulink to evaluate its behavior and performance under RL load. The results obtained in simulation show the feasibility of applying the FCS-MPC control, which together with the virtual resistance and the synchronism algorithm result in a satisfactory smooth transition between the operating modes. As part of this work, the hardware of the grid forming converter was designed and assembled to be controlled by a Digital Signal Processor (DSP).