Virtual Inertia Control of Microgrid Consisting of Low Inertia Resources

In this paper, an adaptive concept of virtual generator based controller for dynamic stability of microgrids consisting of low inertia resources. For this purpose, considering a set of energy storage systems dispatched in the network, a controlled islanding scheme  is provided to dynamically control the microgrid frequency. In this context, based on the concept of center of inertia, the proposed virtual generator scheme is developed through mathematical formulation. Also, from the Inter-area torques evaluated by microgrid control areas in the  center of inertia frame are used as input signals of the developed virtual generator based controller. For the energy storage systems, an equivalent dispatch model is provided and developed through the microgrid dynamic model for improving frequency stability during inter-area oscillations. The proposed virtual generator-based controller is an online and non-model-based scheme which controls several microgrid systems together as an integrated network connected to the upstream network. In order to evaluate the ability of the proposed scheme, realtime simulations are carried out on one  test system consisting of several microgrids. Numerical results demonstrate the effectiveness of the proposed scheme in increasing system inertia constant resulting in a proper dynamic performance with a high damping ratio in facing severe inter-area oscillation.