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Loss minimization in distribution networks has considered as great significance recently since the trend to the distribution generation will require the most efficient operating scenario for economic viability variations. Furthermore, voltage instability phenomena can occur in distribution systems and caused a major blackout in the network. The decline of voltage stability level will restrict the increase of load served by distribution companies. To control distribution networks, it can be used from Distributed Generation (DG). DG is increasingly drawing great attention and development of DGs will bring new chances to traditional distribution systems. However, Installation of DG in non-optimal places can result in an increasing in system losses, voltage problems, etc. This paper presents two scenarios for distributed generation placement in a distributions system. In the first scenario only minimizing the total real power losses in the system is considered. Both the optimal size and location are obtained as outputs from the exact loss formula. The next scenario considered the voltage stability index (SI) to find optimum placement. In these scenarios Different DG placements are compared in terms of power loss, loadability and voltage stability index. To improve power transfer capacity, two line stability indices have been introduced. Distribution power flow solution algorithm is based on the equivalent current injection that uses the bus-injection to branchcurrent (BIBC) and branch-current to bus-voltage (BCBV) matrices. These scenarios are executed on typical 33 and 30 bus test system and yields efficiency in improvement of voltage profile and reduction of power losses; it also may permit an increase in power transfer capacity, maximum loading, and voltage stability margin.

In this paper, a robust energy management system is proposed for islanded microgrids, which at the same time considers static modelling of system frequency. The aim of this paper is to manage frequency excursions produced from load and renewable generation fluctuations. In microgrids, the use of inertia-less and small-scale energy resources risks the frequency stability. In order to overcome this problem, first, the frequencydependent behavior of the distributed energy resources is formulated precisely within the centralized hierarchical energy and reserve management context of a microgrid, Then, in order to handling microgrid uncertainties in a robust way, information gap decision theory (IGDT) technique is proposed. Furthermore, to address a robust hierarchical energy and frequency reserve management architecture, the problem is transmitted into a single level mixed-integer linear programming (MILP) model and solved appropriately over a 24-h scheduling time horizon. Numerical simulation results obtained on a typical islanded smart microgrid are presented including demand response mechanism. The IGDT can help microgrid central controller (MGCC) to make operational decisions in front of major uncertainties. The obtained results verify that through the proposed IGDT-based energy management system, the MGCC can effectively stabilize the microgrid frequency along with its economic targets while considering severe uncertainties.

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Presence of the distributed generation (DG) in electric systems can represent a significant impact on the operational characteristics of distribution networks. The optimal placement and sizing of generation units on the distribution network has been continuously studied in order to achieve different aims. In this paper our aim would be optimal distributed generation allocation for voltage profile improvement, loss and Total harmonic Distortion (THD) reduction in distribution network. Harmony Search Algorithm (HSA) was used as the solving tool, which referring two determined aim; the problem is defined and objective function is introduced according to losses, security and THD indices. The applied fast harmonic load flow method is based on the equivalent current injection that uses the bus-injection to branch-current (BIBC) and branch-current to bus-voltage (BCBV) matrices which were developed based on the topological structure of the distribution systems. This method is executed on 12 bus harmonic unbalanced distribution system and show robustness of this method in optimal and fast placement of DG, efficiency for improvement of voltage profile, reduction of power losses, and THD.