Controle centralizado de tensão e frequência em microrredes ilhadas

Abstract

The islanded operation of microgrids challenges the voltage and frequency control, because in this mode of operation the distribution network can not support the regulation of these variables. This requires from the microgrid a control system that is capable of controlling these variables and managing the active and reactive power reserves of the distributed generators. Secondary voltage control strategies are often applied using concepts of control zones and pilot buses, which serve as a reference for this type of control. In many cases, the proposed criteria do not update the parameters in real time, or keep the pilot bar fixed. This can cause the control parameters to not be properly adjusted for different operating points or the secondary voltage control to keep acting not necessarily in the regions where the most critical voltage values are found. The present work develops a methodology of Centralized Secondary Control with updating of its parameters in real time, which aims to restore the voltage and frequency values to normal operating ranges in case of disturbances in the microgrid. The secondary voltage control is based on sensitivity analysis calculations, classification, determination of control zones and adjustment of voltage references and reactive power of the regulators of synchronous generators, with the update of the pilot bus of the system. The secondary frequency control is based on the determination of the participation factors of each machine and it acts simultaneously with the primary regulation. The algorithm that runs the proposed methodology, as well as the algebraic-differential modeling of the problem, are performed on Matlab, based on a 33-bus test distribution system. The results show the effectiveness of the proposed methodology, since we can restore voltages and frequency to adequate operating levels. In addition, we can manage active and reactive reserves based on the maximum and minimum limits of each machine that participates in the secondary control system. Also, the methodology presented a definition for the control zones that allows the coordinated actuation of more than one machine for the same pilot bus, as well as calculations of the control adjustments of each generator that take into account the reactive reserves of each unit generator.