A voltage source converter comprising: first and second DC terminals (24, 26) for connection to a DC electrical network; a plurality of single-phase limbs, each single-phase limb including a phase element, each phase element including at least one switching element configured to interconnect a DC voltage and an AC voltage, an AC side of each phase element being connectable to a respective phase (a, b, c) of a multi-phase AC electrical network, each single-phase limb being connected between the first and second DC terminals (24, 26); and a controller configured to determine independently of one another an amount of active power (P ref) that the voltage source converter should exchange with the AC electrical network and an amount of reactive power (Q ref) that the voltage source converter should exchange with the AC electrical network, the controller including a first control block which has an active power control block to determine the amount of active power (P ref) to be exchanged with the AC electrical network and a reactive power control block to determine the amount of reactive power (Qr ef) to be exchanged with the AC electrical network, the voltage source converter being characterised in that the controller is further configured to establish a respective phase current reference (I refA, I refB, I refC) for each single-phase limb which is independent of the or each other respective phase current reference (I refA, I refB, I refC) and which defines the current each single-phase limb is required to draw from or pass to a corresponding phase (a, b, c) of the AC electrical network to effect the determined active power (P ref) and reactive power (Q ref) exchanges with the AC electrical network, and in that the controller includes a second control block which has a current reference generator that establishes the respective phase current reference (I refA, I refB, I refC) for each single-phase limb based on the amounts of active and reactive power (P ref, Q ref) determined by the first control block and on positive and negative voltage sequence components (V p αβ, V n αβ) within a stationary α-β reference frame, the positive and negative voltage sequence components (V p αβ, V n αβ) being derived from the actual phase voltage (V a, V b, V c) of each phase (a, b, c) of the AC electrical network. first and second DC terminals (24, 26) for connection to a DC electrical network; a plurality of single-phase limbs, each single-phase limb including a phase element, each phase element including at least one switching element configured to interconnect a DC voltage and an AC voltage, an AC side of each phase element being connectable to a respective phase (a, b, c) of a multi-phase AC electrical network, each single-phase limb being connected between the first and second DC terminals (24, 26); and a controller configured to determine independently of one another an amount of active power (P ref) that the voltage source converter should exchange with the AC electrical network and an amount of reactive power (Q ref) that the voltage source converter should exchange with the AC electrical network, the controller including a first control block which has an active power control block to determine the amount of active power (P ref) to be exchanged with the AC electrical network and a reactive power control block to determine the amount of reactive power (Qr ef) to be exchanged with the AC electrical network, the voltage source converter being characterised in that the controller is further configured to establish a respective phase current reference (I refA, I refB, I refC) for each single-phase limb which is independent of the or each other respective phase current reference (I refA, I refB, I refC) and which defines the current each single-phase limb is required to draw from or pass to a corresponding phase (a, b, c) of the AC electrical network to effect the determined active power (P ref) and reactive power (Q ref) exchanges with the AC electrical network, and in that the controller includes a second control block which has a current reference generator that establishes the respective phase current reference (I refA, I refB, I refC) for each single-phase limb based on the amounts of active and reactive power (P ref, Q ref) determined by the first control block and on positive and negative voltage sequence components (V p αβ, V n αβ) within a stationary α-β reference frame, the positive and negative voltage sequence components (V p αβ, V n αβ) being derived from the actual phase voltage (V a, V b, V c) of each phase (a, b, c) of the AC electrical network.