A cell for a voltage source converter comprising: first and second cell terminals (101, 102); an energy storage element and first and second switches (104, 105) configured such that: in a first switch state the energy storage element is electrically connected between the first and second cell terminals, with a negative terminal of the energy storage element connected to the first cell terminal and a positive terminal of the energy storage element connected to the second cell terminal; and in a second switch state the first and second cell terminals are electrically connected in a path that bypasses the energy storage element; and a discharge module connected between the first and second cell terminals, the discharge module comprising a first element that can operate in a non-conductive state and also a conductive state to allow electrical conduction from the second cell terminal to the first cell terminal, wherein the first element is a line-commutated switching element configured to transition from the conductive state to the non-conductive state if a current or voltage through or across the first element drops below a threshold; a controller configured to, in response to a fault condition, control the first and second switches to be in the first switch state with the first element in the conductive state; characterized in that the controller is further operable to switch the first and second switches (104, 105) to the second switch state to shut-down conduction via the discharge module. first and second cell terminals (101, 102); an energy storage element and first and second switches (104, 105) configured such that: in a first switch state the energy storage element is electrically connected between the first and second cell terminals, with a negative terminal of the energy storage element connected to the first cell terminal and a positive terminal of the energy storage element connected to the second cell terminal; and in a second switch state the first and second cell terminals are electrically connected in a path that bypasses the energy storage element; and a discharge module connected between the first and second cell terminals, the discharge module comprising a first element that can operate in a non-conductive state and also a conductive state to allow electrical conduction from the second cell terminal to the first cell terminal, wherein the first element is a line-commutated switching element configured to transition from the conductive state to the non-conductive state if a current or voltage through or across the first element drops below a threshold; a controller configured to, in response to a fault condition, control the first and second switches to be in the first switch state with the first element in the conductive state; characterized in that the controller is further operable to switch the first and second switches (104, 105) to the second switch state to shut-down conduction via the discharge module. in a first switch state the energy storage element is electrically connected between the first and second cell terminals, with a negative terminal of the energy storage element connected to the first cell terminal and a positive terminal of the energy storage element connected to the second cell terminal; and in a second switch state the first and second cell terminals are electrically connected in a path that bypasses the energy storage element; and a discharge module connected between the first and second cell terminals, the discharge module comprising a first element that can operate in a non-conductive state and also a conductive state to allow electrical conduction from the second cell terminal to the first cell terminal, wherein the first element is a line-commutated switching element configured to transition from the conductive state to the non-conductive state if a current or voltage through or across the first element drops below a threshold; a controller configured to, in response to a fault condition, control the first and second switches to be in the first switch state with the first element in the conductive state; characterized in that the controller is further operable to switch the first and second switches (104, 105) to the second switch state to shut-down conduction via the discharge module.