Desenvolvimento de métodos para controle distribuído em nanorredes c.c.: compartilhamento de potência e restauração de tensão

Abstract

The increasing participation of distributed generation using information technologies in the electrical power system has caused changes in the way energy is generated and consumed. In this context, microgrids and nanogrids come up as a solution capable of providing greater integration of distributed generation to the electrical grid. As the current distribution systems are predominantly in Alternating Current (ac), the ac microgrids are widely researched and their implementation entails minor modifications in the current power grids. However, the significant increase in Direct Current (dc) loads in the ac power systems added to the fact that some renewable energy sources have dc voltage cause the development of dc distribution systems. This new configuration requires major changes to the current distribution system. Thus, the hybrid ac-dc microgrids emerges as a solution that combines the ac and dc advantages with few changes to the current electrical grids. This work presents the main types of hybrid microgrids found in the literature and the control techniques usually employed for parallel operation of the converters. The need for voltage regulation on both buses of the hybrid microgrid, load sharing and power flow control lead to the use of a hierarchical control structure. This work was carried out in the laboratory of the Grupo de Eletrônica de Potência at Universidade Federal de Minas Gerais (GEP/UFMG) and presents the study and development of a hybrid nanogrid prototype capable of operating in both connected and isolated modes of the electrical grid, in addition to making the transition between these modes. Themes about the hierarchical control structure of the microgrid will be discussed. In particular, the work deals with the coordination of network-forming converters, defined by the secondary level, proposing two novel distributed control techniques based on consensus algorithm to mitigate the voltage deviation caused by the droop control and promote the correction in the proportional power sharing. In this work, the proposed nanogrid operation and control techniques are validated through simulations and experimentally.