A Secondary Control Based on Fuzzy Logic to Frequency and Voltage Adjustments in Islanded Microgrids Scenarios

This paper aims to propose a secondary control algorithm based on Fuzzy Logic to adjust frequency and voltage in islanded microgrids. It is well-known, that, when a microgrid changes its operation from grid-connected to islanded mode, the time domain variability of the loads will change the frequency and voltage profiles of the system. In this sense, the operation of the system might become unsafe and out of the acceptable ranges of quality. It is essential that the MGCC be able to restore the frequency and voltage through the secondary control. In this context, a Fuzzy approach is proposed to change the frequency and the voltage reference values in the droop equation of the Voltage Sources Inverters to correct them. The main idea of this paper is to consider these variables uncoupled and then correct each one separately, taking into account that the frequency is global and the voltage is local variables of the system. As results of this work, this paper brings the frequency and voltage profiles of a modified IEEE Feeder Test during a random day, showing the behavior of theses variables with and without the proposed algorithm.