The Microgrid concept has been emerged into the power system to provide reliable, renewable and cheaper electricity for the rising global demand. When the microgrids are introduced, there will be several concerns such as active and reactive power sharing, load management, connecting to the main grid, voltage and current deviations, etc. Recently, with the fast deployment of distributed generation, methods to mitigate microgrid harmonics caused by nonlinear loads and power electronic devices have become one of the main focus areas. Consequently, many research works are devoted to this area introducing different harmonic mitigation methods suitable for the microgrids. Hence, the main goal of this paper is to clearly present a comprehensive review of harmonic mitigation methods from hierarchical control view-point. The control strategies proposed to mitigate harmonics are classified into three groups; Primary, secondary, and tertiary. Furthermore, this overview draws a sketch on the global trends in harmonic mitigation methods of an ac microgrid directly applicable to today’s smart grid applications.

This paper proposes a novel structure for Industrial Demand Response Aggregators (IDRA) to provide operational flexibility for the power system. A robust self-scheduling approach is formulated for the first time to optimize different sub-processes of the whole production line of heavy industries. The new approach satisfies the customer order with the lowest energy cost. Numerical studies are implemented on 8 integrated cement factories, from Khorasan Regional Electric Company (KREC), in the east of Iran. The results show that the integrated model of heavy industries provides guaranteed flexibility to the system when a power shortage occurs or system reliability is jeopardized.