Converter overload protection method by flexible DC transmission bipolar system

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.

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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