A voltage source converter comprising three phase elements defining a star connection in which a first end of each phase element is connected to a common junction; at least two converter limbs, each converter limb including first and second DC terminals for connection in use to a DC network and an AC terminal connected in series with a second end of a phase element, each converter limb defining first and second limb portions, including a chain-link converter, each chain-link converter including chain-link modules; and a third DC terminal connected to the common junction of the star connection to define an auxiliary connection, wherein in use a current is injected into the auxiliary connection to modify a voltage of each chain-link module in each limb portion.