Centralised secondary control for islanded microgrids

Abstract

Electric power systems have undergone substantial changes in their operation. The higher penetration of renewableresources, demand response capability, and generators operating via droop control at the distribution level are the main featuresresulting in the microgrid concept. Microgrids must operate connected or islanded from the main grid, ensuring reliability andquality in the supply of energy in both operating scenarios. In this sense, the secondary control becomes essential in thesystem's resilience, since it is responsible for restoring the frequency and voltage within acceptable values. This study proposesa unified frequency and voltage secondary controls for microgrids operating in islanded mode. For this sake, a modification inthe load flow algorithm considering a Jacobian matrix takes place, enabling a sensitivity analysis to give the adjustments in theset point of generators. The help of the Levenberg-Marquardt method improves the convergence in the modified load flow. Allgenerators are continuously considered in this process, regarding their capabilities and relative control sensitivities concerningthe operation point restoration. The proposed methodology is validated in a modified IEEE-37 node test feeder, showing theefficacy of the centralised secondary control under different scenarios of renewable generation penetration and load levels.