Interoperability of single-controllable clusters: Aggregate response of low-voltage microgrids

Microgrid clusters are complex systems that require the implementation of management strategies to control multiple elements and regulate the offering energy services. This paper proposes a management approach capable of aggregating the operation of clusters of multifunctional microgrids, aiming at improving the resiliency of distribution and transmission systems, as well as enhancing the microgrids' power quality, under predictable and unpredictable events. Since the approach manages microgrids inserted into cluster to operate as single -controllable entities, a variety of ancillary services can be offered (e.g., energy time shifting, peak shaving, islanded operation, and many others). Consequently, operational goals can be pursued locally (i.e., at the point of common coupling of each microgrid) and systematically (i.e., at specific medium and high-voltage circuit branches). To demonstrate the applicability of the proposed energy management system, simulations were carried out using Matlab/Simulink, considering customized blocks in phasor domain, and taking the CIGRE's European benchmark as reference model for the low-, medium-and high-voltage power systems. Different from previous studies, the simulations fully emulate the interoperability among microgrid central controllers, microgrid system operators and distribution system operator, demonstrating that a wide range of ancillary services can be put into action by means of the aggregate response of microgrids and based on price signals, without causing electrical overload. It is also demonstrated in the results that the active and reactive power flow in the high voltage grid is flexibly regulated, the power factor is increased up to 0.955 at different circuit branches, and the power quality is improved in the distribution level during absence of power generation at the medium voltage grid.