DC CURRENT CONTROL IN VSC BASED HVDC CONVERTERS

摘要

The present disclosure provides a method for controlling a direct current, DC, current in a voltage source converter (VSC) station, wherein the VSC station includes at least on modular multi-level converter (MMC), including for example a full-bridge MMC (FB-MMC) submodule. The method includes determining a DC current reference (212), and determining, using a DC current controller (200), a DC voltage correction (222) based on the DC current reference (212). The method also includes generating a DC voltage reference based on a sum of the DC voltage correction (222) and at least one of an actual DC voltage and an ordered DC voltage. The method includes switching the at least one MMC based on the DC voltage reference.The method includes determining whether a DC fault has occurred in the power transmission system, and controlling, on a basis that it is determined that the DC fault has occurred, a DC fault current to zero or close to zero by said switching. The present disclosure also provides a VSC station (700) including a controller (740) for performing the method, and a high-voltage power transmission system (800) including at least one such VSC station (810).