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This paper presents important results of the European HVDC Study Group founded on an initiative by the German Commission for Electrical, Electronic and Information Technologies in September 2010. The main task of the Study Group has been defining “Technical Guidelines for first HVDC Grids”: 1) to gain a common understanding of basic operating and design principles of HVDC grid systems, and 2) to prepare the ground for more detailed standardization work. The HVDC systems are moving from the stage of point-to-point (PTP) connectors to the stage of the transmission systems interconnecting more than two stations and utilizing multiterminal (MT), multivendor (MTMV) HVDC voltage-source converter (VSC) systems. The development will be modular, for example, in steps, starting with interconnecting PTP connectors and establishing three-pod, radial systems. Then, such simple systems may gradually be interconnected into radial and meshed HVDC–VSC systems comprising more HVDC lines and dc converter stations. This paper describes understanding, specification, and standardization of design and operation principles of the HVDC grids seen as the first needed steps toward such MTMV systems. [ABSTRACT FROM PUBLISHER]

Alfven-wave scattering by inhomogeneities of the permittivity tensor ε(r) is examined. The scattering index γ, phase velocity v*, and group velocity c* are calculated over the entire wavelength range. Asymptotic formulas for γ, v*, and c* are derived for long (as compared with scatterer size), short, and ultrashort wavelengths. [ABSTRACT FROM AUTHOR]