A Method for Overload Protection of Converter in Flexible DC Transmission Bipolar System

A flexible DC power transmission and overload protection technology, applied in power transmission and AC networks, etc., can solve the problems of bus power loss, power transfer, power imbalance between two poles, etc., and achieve the effect of reliable transmission and suppression of overload problems.

CN109560565BActive Publication Date: 2022-04-19NR ELECTRIC CO LTD +1
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Publication Date
2022-04-19

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Abstract

The present invention proposes an overload protection method for converters in bipolar systems of flexible direct current transmission. For isolated island passive systems connected to new energy sources, the AC sides of the bipolar converters are respectively connected to their respective AC buses. Increase the connection of bus tie switch equipment between the two poles, and the bipolar operation of the converter. It is judged that when the bipolar power is greater than the maximum power of the one pole converter, the bus tie switch is controlled to be divided. When the bipolar power is less than the maximum power of one pole, Control the bus tie switch to close, so as to avoid the failure of one pole of the bipolar system, which will cause the other pole to be overloaded and stop the operation. The method of suppressing the overload of the inverter is simple, practical, and highly reliable. When one pole fails, the power can be sent through the other pole to the maximum extent, avoiding the overload shutdown of the non-faulty pole, and optimally ensuring the effective delivery of 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 bus power

[0026] P=P1+P2;

[0027] (3) Detect and compare the bipolar bus power P and the unipolar maxim...