Effect of disconnection of generation units on the rate of change of frequency in distributed power systems

In this paper, variation in the Rate of Change of Frequency (RoCoF) in distributed frequency control caused by disconnection/re-connection of generation units is addressed. Distributed generation systems are always subject to irregular and unexpected income and outage of units because of their uncertainties in nature as well as their small capacities. It causes variation in the structure and consequently in the collective dynamics of distributed generators such as performance of voltage and frequency control systems. Using the eigenvalue perturbation analysis, all generation units are ranked based on the influence of their outage on the RoCoF in distributed generation system. It is also shown by simulations that the ranking is highly correlated with the degree centrality of each unit in scale-free communication networks as well as Watts-Strogatz networks with high rewiring probability, i.e. disconnection/reconnection of nodes with higher degrees in the data communication network of the distributed frequency control makes stronger effect on the RoCoF. Simulation results support all achievements.