An energy supporting device for providing grid forming and/or virtual synchronous machine, VSM, capabilities to a high voltage direct current, HVDC, transmission system including a first HVDC converter and a second HVDC converter connected to each other via an HVDC link, wherein the energy supporting device comprises: a plurality of cells configured to be connected in series to the HVDC link, wherein a cell includes: a full-bridge arrangement of power switches (11a-11d); and an energy storage device electrically connected to the full-bridge arrangement; a resistor electrically connected between the plurality of cells and an electrical reference potential; and a bypass switch configured to allow the resistor to be bypassed; wherein the energy supporting device is configured to be operated in: a charging mode, in which the bypass switch is in a closed state for allowing the resistor to be bypassed, and in which the energy storage device of at least one cell of the plurality of cells is receiving electrical energy from the HVDC link; a dissipation mode, in which the bypass switch is in an open state for allowing the resistor to dissipate electrical energy from the HVDC link, and in which the energy storage devices of the plurality of cells are bypassed; and an energy release mode, in which the energy storage device of at least one cell of the plurality of cells is discharging electrical energy to the HVDC link to thereby provide the grid forming and/or VSM capabilities. a plurality of cells configured to be connected in series to the HVDC link, wherein a cell includes: a full-bridge arrangement of power switches (11a-11d); and an energy storage device electrically connected to the full-bridge arrangement; a full-bridge arrangement of power switches (11a-11d); and an energy storage device electrically connected to the full-bridge arrangement; a resistor electrically connected between the plurality of cells and an electrical reference potential; and a bypass switch configured to allow the resistor to be bypassed; wherein the energy supporting device is configured to be operated in: a charging mode, in which the bypass switch is in a closed state for allowing the resistor to be bypassed, and in which the energy storage device of at least one cell of the plurality of cells is receiving electrical energy from the HVDC link; a dissipation mode, in which the bypass switch is in an open state for allowing the resistor to dissipate electrical energy from the HVDC link, and in which the energy storage devices of the plurality of cells are bypassed; and an energy release mode, in which the energy storage device of at least one cell of the plurality of cells is discharging electrical energy to the HVDC link to thereby provide the grid forming and/or VSM capabilities. a charging mode, in which the bypass switch is in a closed state for allowing the resistor to be bypassed, and in which the energy storage device of at least one cell of the plurality of cells is receiving electrical energy from the HVDC link; a dissipation mode, in which the bypass switch is in an open state for allowing the resistor to dissipate electrical energy from the HVDC link, and in which the energy storage devices of the plurality of cells are bypassed; and an energy release mode, in which the energy storage device of at least one cell of the plurality of cells is discharging electrical energy to the HVDC link to thereby provide the grid forming and/or VSM capabilities.