Converter overload protection method by flexible DC transmission bipolar system

A flexible DC transmission and overload protection technology, applied in the direction of power transmission AC network, etc., can solve the problems of power transfer, bus power loss, and the problem of extremely large ground current of the converter, so as to suppress the problem of overload and realize reliable transmission , to avoid the effect of overload outage

CN109560565AActive Publication Date: 2019-04-02NR ELECTRIC CO LTD +1
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2019-04-02

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Abstract

The invention provides a converter overload protection method by a flexible DC transmission bipolar system. For an island passive system connected to the new energy access, alternating current sides of a bipolar converter are respectively connected to respective alternating current buses, bus connection switch devices are used for connection between the alternating current buses, the converter isin bipolar operation, it is determined what the bipolar power is larger than the maximum power of one pole of the converter, the bus connection switches are controlled to be an opening position, whenthe bipolar power is smaller than the maximum power of one pole of the converter, the bus connection switches are controlled to be a closing position so as to avoid the problem that faults of one poleof the bipolar system cause overload of the other pole of the converter to generate off-stream. The method for inhibiting the overload of the converter is simple and practical, and high in reliability, can pass the send-out power of the other pole to the maximum extent when the faults of the pole converter are generated, can avoid the overload off-stream of the non-fault pole and can optimally ensure the effective send-out of the new energy.
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Description

technical field

[0001] The invention belongs to the field of flexible power transmission in electric power systems, and in particular relates to a method for overload protection of a converter in a bipolar system of flexible direct current transmission. Background technique

[0002] Flexible DC transmission uses voltage source converters, which can independently adjust the output of active and reactive power, improve the transmission capacity of the AC system, and easily form a multi-terminal DC transmission system. And other application fields, have obvious competitiveness. With the advancement of power electronic devices and control technology, the capacity and voltage level of flexible direct current transmission system are getting higher and higher.

[0003] In order to meet the requirements of large-capacity power transmission, it is necessary to increase the number of sub-modules to increase the voltage level, but the cascading of too many sub-modules increases the di...

Examples

Embodiment Construction

[0022] The technical solutions of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0023] figure 1 It is a schematic diagram of adding a bus-tie switch to the flexible DC transmission bipolar system in the present invention, that is, adding a QF bus-tie switch to connect between the pole 1 AC bus and pole 2 AC bus. figure 2 It is a flowchart of an overload protection method for a converter of a flexible direct current transmission bipolar system in the present invention, specifically including the following steps:

[0024] (1) The AC side of the converter is connected to the AC busbar, and the QF connection of the bus tie switchgear between the busbars is increased;

[0025] (2) Detect the power P1 sent by pole 1 of the converter, and the power P2 sent by pole 2, and calculate the bipolar power P=P1+P2;

[0026] (3) Detect and compare the bipolar power P and the unipolar maximum power Pmax;

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