Microgrids are known as clusters of distributed energy resources serving a group of distributed loads in grid-connected and isolated grid modes. Nowadays, the concept of microgrids has become a key subject in the smart grid area, demanding a systematic procedure for their optimal construction. According to the IEEE Std 1547.4, large distribution systems can be clustered into a number of microgrids to facilitate powerful control and operation infrastructure in future distribution systems. However, clustering large systems into a set of microgrids with high reliability and security is not reported in current literature. To fill-out this gap, this paper presents a systematic and optimized approach for designing microgrids taking into account system reliability- and supply-security-related aspects. The optimum design considers sustained and temporary faults, for system reliability via a combined probabilistic reliability index, and real and reactive power balance, for supply security. The loads are assumed to be variable and different distributed generation (DG) technologies are considered. Conceptual design, problem formulation and solution algorithms are presented in this paper. The well-known PG&E 69-bus distribution system is selected as the test system. The effect of optimization coefficients on the design and the robustness of the algorithm are investigated using sensitivity studies.

Recently, the concept of microgrids (clusters of distributed generation, energy storage units, and reactive power sources serving a cluster of distributed loads in grid-connected and isolated grid modes) has gained a lot of interest under the smart grid vision. However, there is a strong need to develop systematic procedure for optimal construction of microgrids. This paper presents systematic and optimized approaches for clustering of the distribution system into a set of virtual microgrids with optimized self-adequacy. The probabilistic characteristics of distributed generation (DG) units are also considered by defining two new probabilistic indices representing real and reactive power of the lines. Next, the advantages of installing both distributed energy storage resources (DESRs) and distributed reactive sources (DRSs) are investigated to improve the self-adequacy of the constructed micro-grids. The new strategy facilitates robust infrastructure for smart distribution systems operational control functions, such as self-healing, by using virtual microgrids as building blocks in future distribution systems. The problem formulation and solution algorithms are presented in this paper. The well-known PG&E 69-bus distribution system is selected as a test case and through several sensitivity studies, the effect of the total DESRs or DRSs capacities on the design and the robustness of the algorithm are investigated.

Self-healing is a major driving force in the smart grid vision. This paper proposes a comprehensive design and operational planning framework to generate optimum self-healing control actions in a distribution system. For this purpose, a distribution system with optimally allocated distributed generators (DGs) is divided into a set of microgrids with high self-adequacy through allocation of distributed energy storage resources (DESRs) and distributed reactive sources (DRSs). Afterwards, by using the predicted load and generation of renewable-based distributed generators for the next hour of the day and other important factors (self-adequacy in the unfaulted microgrids, total distribution system's energy losses and the total supplied loads according to their requested reliability), the optimum self-healing strategy is planned for the system for all possible future faults. The IEEE 123-bus distribution system is selected as the test system; optimum microgrids are designed and several case studies are presented to demonstrate the effects of optimization coefficients on the optimum self-healing control actions.

Microgrids have gained a lot of interest under the smart grid vision demanding systematic procedures for their optimal construction and performance enhancement. By defining a new probabilistic index, this paper presents approaches for clustering active distribution systems into a set of microgrids with optimized reliability and supply-adequacy indices. After proposing two different methods for optimally designing the microgrids, as two corrective actions to improve the defined index, the advantages of installing distributed reactive sources (DRSs) and distributed energy storage resources (DESRs) are investigated. The problem formulation and solution algorithms are presented in this paper. The well-known PG&E 69-bus distribution system is selected as a test case and through several sensitivity studies, the robustness of the design and the effect of interconnecting different amounts of DRSs' and DESRs' capacities on the defined index are investigated. It is found that by properly designing the system and integrating the DRSs and DESRs, the index can be improved from 23% in the base system without distributed generators (DGs) to 77% in the basic microgrid design with distributed generators and to 93% considering all resources.

An optimized communication and control infrastructure, based on the microgrid building block concept, for active distribution systems is essential to facilitate powerful control framework under the smart grid paradigm. In this paper, a novel methodology for designing a communication and control infrastructure is presented. The new design takes into account both communication system and distribution system-related aspects. The proposed design facilitates systematic and optimized clustering of the distribution system into a set of virtual microgrids with optimized communication requirements while considering the power quality aspects, characteristics of distributed generation units, distributed energy storage units, and distributed reactive sources. The new design facilitates robust infrastructure for smart distribution systems operation and control, e.g., self-healing control and optimized system-level operation, by using virtual microgrids as building blocks in future distribution systems. The motivations, conceptual design, problem formulation and solution algorithms are presented in this paper. The well-known PG&E 69-bus distribution system is selected as a test case and through several sensitivity studies, the effect of optimization coefficients on the design, and the robustness of the algorithm are investigated. Finally, the algorithm is tested on the IEEE 123-bus distribution system.

Energy management in distribution systems has gained attention in recent years. Coordination of electricity generation and consumption is crucial to save energy, reduce energy prices and achieve global emission targets. Due to the importance of the subject, this paper provides a literature review on recent research on energy management systems and classifies the works based on several factors including energy management goals, the approaches taken for performing energy management and solution algorithms. Furthermore, the paper reviews some of the most proficient techniques and methodologies adopted or developed to address energy management problem and provides a table to compare such techniques. The current challenges and limitations of energy management systems are explained and some future research directions have been provided at the end of the paper.