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Final report RSE 17000225

Project T&D-C.C.: DC Transmission and Distribution project. Synthesis Report of 2016

The report presents a summary of the results of the research activities related to LVDC, MVDC and HVDC grids: the activities involved studies, simulations, experiments in the laboratory and in the DC microgrid available in RSE.

The project covered studies and experimental activities on DC networks at all voltage levels. About the MVDC distribution grid several aspects have been analyzed: the development of DC distribution grids with multiple levels of voltage, the impact to the grid of a Dual Active Bridge converter for interfacing MVDC and LVDC active grids; the connection criteria in LVDC; the ground management and the operation of multiterminal MVDCs in case of fault; the integration of MVDC links into the MV distribution network in the perspective of OPF assessment. Furthermore, an experimental activity was carried out on the LVDC microgrid, available in RSE, in order to test the behavior of mixed AC and DC networks. At the same time, a hybrid switch prototype for the LVDC networks has been developed and the first tests were carried out.

As regards the DC transmission grids, multi-scale modeling methodologies have been developed to predict the acoustic field, in order to assess the acoustic noise produced by the lines due to coronal phenomena, especially in post-rain conditions. The analysis was supported by experimental activities in the High Voltage Laboratory and the experimental characterization of the behavior of polymer isolators for HVDC lines. With regard to VSC converters for HVDC link, the definition of control strategies for increasing the virtual inertia of the system, using properly the capacitors installed in the DC section has been carried out. The revamping of the SA.CO.I., HV link between Sardinia and continental Italy, with VSC technology to increase the connection capacity of renewable power has been studied. The simulation activity started with the implementation of models with the basic drive control schemes integrated with the power control function "P f" and the PSS (Power System Stabilizer) stabilization signals for dampening electromechanical oscillations. At the end, the first analysis of the main economic and environmental benefits that might result from the realization of a VSC-HVDC connection have been carried out.

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