Influência de técnicas de sincronização de conversores na distorção harmônica de microrredes

Abstract

Microgrids (MGs) are smaller-scale power systems used to integrate distributed energy resources into the main electrical grid through power converters. To ensure safe and efficient operation of these systems, both in grid-connected and islanded modes, control strategies are essential for power sharing and maintaining voltage and frequency stability. In the context of converter control, synchronization techniques, such as Phase-Locked Loops (PLLs), are employed to estimate the grid frequency and phase, ensuring the converters are synchronized with the voltage signal at their point of connection. However, these control systems are vulnerable to power quality issues, mainly voltage imbalances and harmonic distortions in the voltage signals. The presence of converters and non-linear loads are some of the causes of harmonic distortions in MGs, negatively affecting the performance of synchronization techniques. Based on the hypothesis that synchronization techniques may affect the harmonic distortion of voltage and current signals, and given the scarcity of studies regarding this problem, the present work aims to fill this gap in the literature by evaluating the dynamic behavior of synchronization techniques and their impact on the harmonic distortion of MGs. Four synchronization techniques were selected based on the literature and implemented on Digital Signal Processors (DSPs). The techniques were subjected to two types of tests: the first involved applying known signals using the UNIOESTE MG Laboratory structure, where their dynamic performance was evaluated under events of frequency and phase variation, and harmonic distortion. The second type of test was conducted via simulations in PSIM software, in which the laboratory MG model was implemented. The simulations considered the connection of a non-linear load model at different operating points and under various converter combinations. The experimental results showed that synchronization techniques with advanced filtering capabilities have better dynamic performance, ensuring robustness against grid disturbances. In the simulations, it was concluded that there is no significant coupling between the chosen synchronization technique and the harmonic distortion of the electrical quantities in the evaluated scenarios. The main contribution of this work is the verification of the hypothesis in the MG context, in addition to the development of the laboratory MG structure and the detailed computational model for future studies.