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

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.

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...

AI Technical Summary

Problems solved by technology

[0004] The bipolar system structure of flexible direct current transmission realizes that when renewable new energy is sent out from an isolated island, new energy sources such as wind power and photovoltaics are connected to the AC bus at multiple points, and the bipolars are connected to the AC bus. If the bipolar buses are not connected, the power of the two poles is unbalanced. , there is a large current problem in the grounding pole of the inverter. In addition, when one pole of the inverter fails, the power of the busbar connected to this pole will be completely lost, and the effective transmission of new energy cannot be realized.

If the bipolar bus is directly connected without control, when one pole fails, the other pole will have the risk of overload and outage due to power transfer

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