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In the 21st century the concept of electrical power supply is morphing gradually from centralized into decentralized system, indicated by increasing the Installation of distributed generation on the main grid. With emerging of advanced Communication and information technology, the aggregation of several small size, environmentally compatible, generators close to the loads can be developed as virtual power plant in order to provide added-value to the electric Power system. In this paper an operation optimization algorithm is proposed to integrate two DGs and a micro grid into a VPP control area, containing several loads, which will be able to generate and sell electrical energy to loads and power market. Suitable models are proposed to simulate electric production, and the energy exchange between VPP and Grid. The optimization problem is here formulated as a non-liner maximization algorithm with constraints, where the objective function is profit of the VPP with supply of electric energy for all the loads.Solving the VPP optimization problem in two different scenarios with GAMS software will complete the paper.

Physical and electrical characteristics of hightemperature superconducting (HTS) DC power cables have been modelled to assess their benefits compared to conventional XLPE cables for use in distribution networks of tightly coupled electrical systems such as the Navy all-electric ship. The characteristics of a 30-m long HTS DC cable prototype that was successfully demonstrated recently were used to evaluate the benefits of increased power density, both volumetric and gravimetric, in comparison with similarly rated XLPE cables. The response of HTS cables for electrical faults and switching harmonics were studied through electrical models. The results of transient characteristics of HTS cables were compared to that of normal cables under identical network conditions. The peak voltage observed for the HTS cable network when faulted was considerably smaller than that of the XLPE bundle under a 1 kΩ ground resistance. On the contrary, the over voltage of the ungrounded HTS cable system was larger than that of the XLPE cable. The damping constant of the HTS cable was 3 times higher than XLPE cable.

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