There is provided a switching valve for a voltage source converter. The switching valve comprises a plurality of modules, each module including at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module arranged to be combinable to selectively provide a voltage source, the switching valve including a controller configured to selectively control the switching of the switching elements to select one or more of the modules to contribute a or a respective voltage to a switching valve voltage,



wherein the controller is configured to selectively carry out a module selection by:
assigning each module with a respective address in an address queue;
in a respective one of a plurality of sampling events, selecting one or more voltage contributing modules in order of its assigned address in the address queue; and
between different sampling events, changing the order of selecting the or each voltage contributing module based on its assigned address in the address queue.