Frequency control in networked microgrids with voltage-sensitive loads

Abstract

This paper presents a frequency control scheme for a networked microgrid system through the coordination of the conventional frequency controller and a novel dual-mode voltage-based frequency controller. The proposed voltage-based frequency controller has two operating modes: a frequency restoration mode to restore the frequency immediately upon the frequency deviation from the nominal value being beyond a certain limit, and a voltage restoration mode to restore the voltage after the frequency is recovered to a satisfactory range. The controller aims to reserve enough voltage margin in case of consecutive disturbances, as well as to mitigate any negative impact on loads. A proper switching logic is designed to enable the mode switching. On the other hand, microgrids in a networked microgrid system can help each other during transients when emergencies happen. By combining the advantages of both networked microgrids and the characteristic of voltage-sensitive loads, the system frequency response is improved dramatically. The effectiveness of the proposed controller and superiority of the networked microgrid system over single microgrids in terms of system response under disturbances have been tested and validated through various simulations in PowerFactory.