Virtual inertia to the AC Microgrid to improving the ROCOF and frequency Nadir in a Hybrid AC/DC Microgrid.

Abstract

To move the global energy away from fossil fuels towards renewable energy leads toward a more complex grid, after experiencing a reduction of inertia when integrating large renewable energy sources (RES). With an increased pace of RES penetration into the grid and along a growing demand of electrical power, the challenge to maintain the system frequency as close as possible to the nominal range increase. The RES are limited by wind condition and daylight to provide an energy momentum into the transmission or distribution grid. Therefore, the utilization of virtual inertia to improve the Rate Of Change Of Frequency (ROCOF) and the minimum value of frequency reached during the transient period (frequency Nadir) is an addressed necessity to solve the inertia issue. Giga Watt projects for solar and wind energy are already built, with several and even larger are both planned and built at the moment, which have resulted in an even higher attention and concern to the transmission lines, distribution grid and the power stability. Main present global source of electricity production are heat generated, which during phasing out fossil also causes the loss of rotating inertia. This means the issue is and will grow globally in all the parts of the power networks.