RELATING TO POWER TRANSMISSION NETWORKS

In the field of high voltage direct current (HVDC) power transmission networks, there is a need for improvements to allow a single power converter to control individual AC network voltages carried by multiple AC transmission conduits to multiple AC network elements, such as respective wind parks. A power transmission network () comprises a power converter () which has first and second DC converter terminals () that are for connection, in use, to a DC network. The power converter () also includes an AC converter terminal () which is electrically connected to a plurality of AC transmission conduits (), each of which is for connection, in use, to a respective AC network element () that is configured to operate at a respective individual AC network voltage. The power converter () further includes a primary converter controller () which is programmed, in use, to control the transfer of power through the power converter () and thereby between the DC network and the plurality of AC network elements (). The primary converter controller () is further programmed, in use, to control each individual AC network voltage by establishing a virtual voltage which is representative of the plurality of AC network voltages and altering a single AC converter voltage produced by the power converter () at the AC converter terminal () to adjust the virtual voltage and thereby adjust each individual AC network voltage.