Improvement of Frequency Control of Multi-Microgrids in Distribution Networks

With the growing need for energy, the concept of Microgrids (MG) with notable benefits for both production and demand sides was introduced. An MG consists of distributed generation units (DG), Energy Storage Systems (ESSs), and loads. It can operate either connected to the grid or in islanded mode. In the case of a fault or a disturbance, MG can be isolated from the main grid. Then, due to the imbalance between production and consumption, the MG frequency will deviate from the standard value. This makes the MG frequency will deviate from the standard value. The most important issue in the transition from connected to disconnected mode is to fix the disconnected MG frequency. This frequency deviation and its attenuation rate are of high importance for the demand side. To improve MG performance, MGs can be connected through a back-to-back (BTB) converter and form a multi-MG (MMG). Local DC resources are connected to their MG through an inverter, while other AC generations are directly connected to the MG. This article investigates the effects of MMG operation on each MG performance. It also examines the role of each MG in maintaining the balance between production and consumption in the MMG structure. It is assumed that each MG has at least one Micro-Turbine (MT) containing excitation control for its voltage regulation. Simulations are carried out in MATLAB Simulink environment to study frequency fluctuations. It is shown that the cooperation of the MGs can improve the performance of the MMG system.