الفهرس 
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Abstract
Power system is facing new challenges as the present system which is subjected to severely stressed conditions. Voltage instability is a quite frequent phenomenon under such a situation rendering degradation of power system performance. In order to avoid system blackouts, power system is to be analyzed in view of voltage stability for a wide range of system conditions.
Distribution systems consist of groups of interconnectedradial circuits. The configuration of the system may be variedby switching operations to transfer loads among the feeders.Two types of switches are applied in primary distributionsystems, which are normally closed switches (sectionalizingswitches) and normally open switches (tie switches). The reconfiguration problem is defined as the process of changing the topology of the network using some the sectionalizing and tie switches so that all of the constraints are observed and the radial structure of the system is preserved simultaneously. It is a cost-less technique and can play an important role in improving the power system from different aspects such as power loss reduction, voltage profile and reliability enhancement.
However, due to large frequency perturbations or contingency plans, intentional islanding is planned in advance in power systems to cope with problems in the network. In this case, it may be more challenging to define the islanded area conditions and guarantee the success of the islanding procedure. In power systems, especially those with islanding conditions, supply and demand have to be balanced in real-time as an imbalance between them leads to several problems, such as frequency and voltage deviations in the power grid that leads to complete blackout.
In recent years, the distributed energy resources (DERs), including distributed generation (DG) and distributed storage (DS), have been among the popular strategies to improve the radial distribution systems because of many advantages like lower carbon imprints, lower fuel costs, and ability for reducing power losses and improving power quality service on distribution lines Nowadays, these renewable DERs are required to equip with reactive power devices (such as static VAR compensators, capacitor banks, etc.), to provide reactive power as well as to control the voltage at their terminal bus.
The main purpose of this work is to investigate the positive role of the reconfiguration strategy, the DERs and the capacitor banks on the stability, reliability and power loss of the distribution networks. The study refers to the possibility of supplying the loads, without loss of generality under islanding conditions after disconnection from the external grid. This study isdemonstrated in five different scenarios:
• Scenario I: Network reconfiguration has been established only without adding DER units or capacitor banks.
• Scenario II: DER units are allocated with the baseconfiguration (DER allocation only).
• Scenario III: Capacitor banks are allocated with the baseconfiguration.
• Scenario IV: DER units are allocated simultaneously with capacitor banks.
•Scenario V: DER units and capacitor banks are allocated simultaneously with, or after networkreconfiguration.