DC current control in vsc based HVDC converters

A converter, voltage source converter technology, applied in the output power conversion device, the conversion of AC power input to DC power output, electrical components and other directions, can solve the problems of complex FB-MMC control, and improve reliability. and availability, improved transient performance, improved steady-state performance
CN110603704AActive Publication Date: 2019-12-20HITACHI ENERGY SWITZERLAND AG
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Patent Information

Authority / Receiving Office
CN · China
Current Assignee / Owner
HITACHI ENERGY SWITZERLAND AG
Publication Date
2019-12-20

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Abstract

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 actualDC 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 powertransmission 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).
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Description

technical field

[0001] The present disclosure relates to the field of controlling voltage source converter (VSC) stations. In particular, the present disclosure relates to the field of controlling VSC stations having one or more modular multilevel converters (MMCs). Background technique

[0002] A voltage source converter (VSC) station used in a high voltage power transmission system may comprise one or more modular multilevel converters (MMCs) with series connected batteries or submodules. These inverters typically use capacitors as energy storage elements. In such converters there is an additional control variable in the form of total cell capacitor voltage or converter energy. Other control variables may correspond to reactive power and real power / DC voltage.

[0003] In MMCs based on half-bridge (HB) cells, the magnitude of the alternating current (AC) voltage may depend on the DC voltage. As a result, the total cell capacitor voltage and the DC voltage can be linked...

Claims

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