A Method for Suppressing Converter Overload in Flexible DC Transmission Bipolar System

Abstract

The invention proposes a method for suppressing the overload of the converter in a flexible direct current transmission bipolar system. For connecting to an island passive system such as new energy access, the two poles of the AC side of the bipolar converter are respectively connected to an independent AC busbar. The two-pole busbar adopts electronic switchgear as the bus-tie switch. The inverter operates with two poles, and the bus-tie electronic switch is connected. When one pole is blocked, monitor when the power of the two poles is greater than the maximum power limit of the one-pole converter, and disconnect the bus. When the bipolar power is less than the maximum power limit of one pole, the electronic switch is kept on. In addition, in view of the failure of the DC line of the sending-end converter to the receiving-end converter, an energy dissipation resistance device connected by an electronic switch is added to the positive and negative DC busbars, and the electronic switch is turned on when the DC overvoltage is detected. Energy dissipating resistor device to suppress overvoltage of the converter.

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 suppressing the overload 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 t...

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

In addition, when a fault occurs outside the converter area at the sending end, the power cannot be sent out, and DC overvoltage problems will occur at the corresponding fault pole.

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