A grid forming vector current control system for controlling a grid intertie, the system comprising: a first terminal configured to be connected to a first power grid, the first terminal comprising a first current control unit, a first virtual admittance unit, and a first phase locked loop, PLL, unit, wherein the first virtual admittance unit and the first PLL unit are configured to emulate an inertia of a first virtual synchronous machine, VSM, and a first virtual current source is connected in parallel to the first VSM; the grid forming vector current control system is characterised in further comprising: a second terminal configured to be connected to a second power grid, the second terminal comprising a second current control unit, a second virtual admittance unit, and a second PLL unit, wherein the second virtual admittance unit and the second PLL unit are configured to emulate an inertia of a second virtual synchronous machine, VSM, and a second virtual current source is connected in parallel to the second VSM; and a controller being configured to use a transient power P VSM1 consumed by the first VSM to generate a power-equivalent current reference to control the second virtual current source and to use a transient power P VSM2 consumed by the second VSM to generate a power-equivalent current reference to control the first virtual current source. a first terminal configured to be connected to a first power grid, the first terminal comprising a first current control unit, a first virtual admittance unit, and a first phase locked loop, PLL, unit, wherein the first virtual admittance unit and the first PLL unit are configured to emulate an inertia of a first virtual synchronous machine, VSM, and a first virtual current source is connected in parallel to the first VSM; the grid forming vector current control system is characterised in further comprising: a second terminal configured to be connected to a second power grid, the second terminal comprising a second current control unit, a second virtual admittance unit, and a second PLL unit, wherein the second virtual admittance unit and the second PLL unit are configured to emulate an inertia of a second virtual synchronous machine, VSM, and a second virtual current source is connected in parallel to the second VSM; and a controller being configured to use a transient power P VSM1 consumed by the first VSM to generate a power-equivalent current reference to control the second virtual current source and to use a transient power P VSM2 consumed by the second VSM to generate a power-equivalent current reference to control the first virtual current source. a second terminal configured to be connected to a second power grid, the second terminal comprising a second current control unit, a second virtual admittance unit, and a second PLL unit, wherein the second virtual admittance unit and the second PLL unit are configured to emulate an inertia of a second virtual synchronous machine, VSM, and a second virtual current source is connected in parallel to the second VSM; and a controller being configured to use a transient power P VSM1 consumed by the first VSM to generate a power-equivalent current reference to control the second virtual current source and to use a transient power P VSM2 consumed by the second VSM to generate a power-equivalent current reference to control the first virtual current source.