Frequency control issues in microgrids with renewable energy sources

This paper presents the main frequency control issues related to the autonomous operation of RES-based microgrids (MGs), which include both classical generators and inverters. Following the regulations from classical power systems, the frequency control is divided in three levels, which are dissociated in time and this paper relates with the first two, i.e. primary and secondary levels. On this line, the paper proposes a frequency control method developed for the MG-connected inverters.