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Charging method for condition of direct-current side short-circuiting of sub-module hybrid converter

A seed module and charging method technology, applied in the direction of power transmission and AC network, can solve the problem of short circuit of AC three-phase voltage through the converter valve, etc., and achieve the effect of strong application value

Active Publication Date: 2018-10-19
XUJI GRP +3
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The purpose of the present invention is to provide a charging method when the DC side of the sub-module hybrid converter is short-circuited, so as to solve the problem that the existing method of charging when the DC side is short-circuited easily causes the AC three-phase voltage to short-circuit through the converter valve

Method used

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  • Charging method for condition of direct-current side short-circuiting of sub-module hybrid converter
  • Charging method for condition of direct-current side short-circuiting of sub-module hybrid converter
  • Charging method for condition of direct-current side short-circuiting of sub-module hybrid converter

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Embodiment 1

[0053] figure 1 A schematic diagram of the unipolar system of the double-ended UHV flexible DC system is given, figure 1 Among them, Q1 is the incoming line isolation switch, Q2 is the outgoing line isolation switch, BPS is the high-speed bypass switch, and BPI is the bypass switch. The system at each end adopts the topological form of high and low valve groups, and each valve group has a set of DC switches on the DC side, which are used to switch on or off the valve group, and the high-speed bypass switch BPS and bypass knife gate need to be closed when the valve group exits online BPI, the closed BPS and BPI need to be disconnected when the valve group is put online. This requires the valve group to have the ability to operate at zero DC voltage, thus creating favorable conditions for the breaking operation of the DC field switch. For this reason, the valve group needs to adopt sub-modules that can output back pressure during normal operation, such as full-bridge sub-modul...

Embodiment 2

[0071] In addition to the start-up condition that the DC positive and negative busbars of the hybrid MMC of the half-bridge sub-module and the full-bridge sub-module described in Embodiment 1 are short-circuited during the switching on and off of the valve group, the present invention is also applicable to other DC positive and negative busbars. The start-up condition of the sub-module hybrid converter with short-circuited bus, and the converter is not limited to MMC with a mixture of half-bridge sub-modules and full-bridge sub-modules, but can be two or more sub-modules that meet the following two conditions at the same time Mixed MMC: The first condition is that the port voltage output by the sub-module when the bridge arm current in the positive direction flows through the lockout should not be lower than the absolute value of the port voltage output when the bridge arm current in the negative direction flows. The second condition is When at least one of the sub-modules flow...

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Abstract

The invention belongs to the power system flexible direct current transmission field and relates to a charging method for the condition of the direct-current side short-circuiting of a sub-module hybrid converter. The charging method of the invention comprises a natural charging stage and a soft-start charging stage. According to the natural charging stage, all sub-modules are blocked. According to the soft-start charging stage, some sub-modules in bridge arms, which satisfy conditions, are cut off, and the other sub-modules remain locked. According to the charging method of the invention, a reasonable sub-module cut-off means is adopted, a problem that an alternating-current three-phase voltage is short-circuited through the upper bridge arm and lower bridge arm of a converter valve undera special starting condition that the direct-current positive busbar and direct-current negative busbar of the sub-module hybrid converter are short-circuited can be solved; and the various sub-modules are all charged to be a set value, and therefore, the method has a high application value.

Description

technical field [0001] The invention relates to the field of flexible DC power transmission in power systems, in particular to a charging method when the DC side of a sub-module hybrid converter is short-circuited. Background technique [0002] Modular multilevel voltage source converter (MMC) has been favored by academia and industry because of its many advantages such as independent control of active and reactive power, no commutation failure, and power supply for passive islands. At the same time, the MMC system also has the advantages of low switching frequency, low switching loss, no need for AC filter banks, and strong scalability, which makes it applicable to high DC voltage and high power transmission occasions. [0003] At present, limited by the withstand voltage level of switching devices and the difficulty of control system design, when MMC is applied to UHV DC systems, the structural form of two valve groups operating in series is often used. At the same time, i...

Claims

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Application Information

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IPC IPC(8): H02J3/36
CPCH02J3/36Y02E60/60
Inventor 姚为正杨美娟王先为张浩吴金龙
Owner XUJI GRP