CONVERTER VALVE ASSEMBLY

There is disclosed herein a converter valve assembly () for a power grid system, comprising two or more equal groups () of prismatic converter cells (-), each group () being arranged in a respective plane () of a plurality of parallel planes spaced apart along a horizontal axis (). Converter cells (-) in a group () are connected in series, and the groups () are connected in series along the axis (). The prismatic converter cells (-) in a group () are arranged such that there is a corresponding voltage difference between each converter cell (-) in the group () and each corresponding converter cell (-) in an adjacent group () that is a spatially nearest to said each converter cell (-), during operation of the converter valve assembly (). Therefore, a spacing between groups may be reduced and an overall volume of the converter valve assembly may be reduced.