Grounding arrangement for a voltage source converter

Abstract

A grounding arrangement for a Voltage Source Converter (VSC) in a power transmission system is provided. The VSC comprises at least one converter branch () comprising at least one module (-), each module comprising a plurality of serially connected sub-modules (-) that can be controllably switched to generate a controlled voltage across the module (-) and each module including a first sub-module (24) at one end thereof and a last sub-module () at an opposite end thereof. Each sub-module (-) includes a first terminal (), a second terminal (), an energy storage element () and a switching arrangement (), wherein at least one of the first () or second terminals () is coupled to a terminal of the energy storage unit (). A first terminal () of the first sub-module () of a module () at one end of the converter branch () is configured to be connected to earth potential on or after shutdown of the converter, and a second terminal () of the last sub-module () of the module (N) at the opposite end of the converter branch () is configured to be connected to earth potential on or after shutdown of the converter. A grounding arrangement () comprising a plurality of switch units () is provided, each switch unit () associated with one of the plurality of sub-modules (-) of each module (-) and configured to connect the first () and second () terminals of the associated sub-module (24-24) on remote activation of the grounding arrangement (), following connection to earth potential of the first () and last sub-modules () of the converter branch ().