Series voltage compensator and system for suppressing commutation failure of conventional DC converter station

Abstract

The invention discloses a series voltage compensator and system for suppressing commutation failure of a conventional DC converter station. The compensator includes: first to third converter chains, each of the first to third converter chains It includes multiple fully-controlled voltage source sub-modules, which are connected in series between the LCC-HVDC converter transformer and the AC port of the converter to control the series voltage to assist valve group commutation, and increase the power of the LCC-HVDC converter commutation voltage area. The compensator uses a converter chain composed of controllable full-bridge sub-modules to be connected in series between the AC port of the conventional DC system converter and the converter transformer, and does not need to modify the internal structure of the original converter bridge arm. It has good ability to suppress commutation failure and accelerate recovery after failure, which can significantly improve the ability of LCC‑HVDC to defend against commutation failure and the recovery speed after commutation failure. It has high control flexibility, low cost, and good engineering practicality.

Description

technical field [0001] The invention relates to the technical field of high-voltage direct current transmission, in particular to a series voltage compensator and a system for suppressing commutation failure of a conventional direct current converter station. Background technique [0002] The traditional grid-commutated high-voltage direct current transmission system (line commutated converter, LCC-HVDC) has the advantages of long-distance large-capacity power transmission and controllable active power, and is widely used around the world. However, since the thyristors used in its converters need to rely on the AC system to provide commutation voltage, commutation failures are prone to occur in the event of AC system failure, resulting in a surge in DC current and a rapid loss of DC transmission power. In addition, in recent years, some regional power grids in my country have had multiple DC feed-ins. Once a commutation failure occurs in a certain DC line, the coupling of th...

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Problems solved by technology

However, due to the need to install additional circuits in each bridge arm of the LCC converter, the utilization rate of the additional components is not high, and it involves the modification of the LCC converter body, which is costly and difficult

[0006] In addition, there are also researches, such as a new type of capacitor-commutated converter based on the anti-parallel thyristor full-bridge sub-module, further based on the full-bridge module composed of bidirectional thyristors connected to the AC end of the LCC converter, and a ECCC (Enhanced CCC, The topology of the enhanced capacitor commutated converter can save 50% of the module capacitor capacity compared with the additional circuit scheme in the bridge arm, and at the same time avoid the transformation of the bridge arm of the converter. Significantly insufficient resistance to commutation failure of the first and second commutation processes after a voltage failure and high voltage stress on the thyristors in the module

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