A method for starting a flexible direct current transmission system

Abstract

The invention provides a starting method of a flexible DC transmission system. The starting method is applied to the flexible DC transmission system which comprises clamp double submodules. In a first charging state, charging resistors of current transformers which are accessed to a power grid are connected to the flexible DC transmission system comprising the diode clamp submodules, and carries out uncontrolled rectification charging; in a second charging state, guide IGBT of each current transformer accessed to the power grid is switched on, the current transformer at a rectifying side is unlocked, and the current transformer at an inverting side is unlocked, so that a charging voltage of a current converter of each diode clamp submodule can reach a charging voltage of a current converter of a half-bridge module, thereby solving the problem of a C-MMC module that the surge current is large when unlocking the current converters due to low charging voltage of the flexible DC transmission system. The flexible DC transmission system started adopting the starting method has small AC current surge and small DC current surge.

Description

technical field [0001] The invention relates to the technical field of flexible power transmission and distribution, in particular to a [0002] A start-up method of a flexible direct current transmission system of sub-modules. Background technique [0003] Compared with the traditional voltage source converter, the Modular Multilevel Converter (MMC) has the advantages of good scalability, small harmonics, low switching frequency, and less requirements for consistent triggering of devices, especially suitable for DC power transmission applications. [0004] In order to reduce the loss and the number of components, the early MMC adopts the cascaded form of half-bridge submodules, but the MMC in the cascaded form of half-bridge submodules cannot effectively block the DC fault. Therefore, the MMC based on the clamp double submodule (CDSM) An improved MMC (called C-MMC) is gaining more and more popularity. In addition to retaining the general advantages of the early MMC, the ...

AI Technical Summary

Problems solved by technology

[0007] Aiming at the above-mentioned deficiencies in the prior art, the present invention provides a start-up method of a flexible direct current transmission system, which is used to solve the problem of large inrush current generated when the converter is unlocked in a flexible direct current transmission system including clamping twin The problem of additional power loss

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