The High Voltage Direct Current Transmission systems of electricity, which use the Voltage Source Technology (HVDC-VSC), are nowadays in continuous development. Thanks to their characteristics of flexibility of use and management, they easily find field for the integration with the traditional electric grid. Therefore all these features have brought the VSC solution to be the dominant technology than the traditional Current Source Systems (HVDC-CSC). The present book focuses on the model, the analysis and the management of a HVDC-VSC system in two grid configurations, starting from the case of point to point link, until the passive network management. The aim is to demonstrate that this technological solution is able to control independently one each other the fluxes of active and reactive power, to the nodes of connection with the AC grids. Besides, the study is based on the verification that this solution is also suitable to the management of an islanded grid, supplying its loads and predisposing the system to the grid reconnection.