Direct-current overvoltage suppressing method of flexible direct-current power transmission system connected with wind farm

Abstract

The invention relates to a direct-current overvoltage suppressing method of a flexible direct-current power transmission system connected with a wind farm in the technical field of wind farm power transmission. When the voltage of a receiving-end alternating-current system drops, the alternating-current voltage frequency output by a sending-end converter station is increased according to acquired direct-current voltage and is tracked in real time by a doubly-fed wind turbine controller. The doubly-fed wind turbine controller adjusts the rotation speed of a doubly-fed wind turbine according to the relation between the alternating-current voltage frequency and the angular speed of the doubly-fed wind turbine so as to increase the kinetic energy of the wind turbine, reduce the output power of the wind farm and suppress the rise of the direct-current voltage. When the voltage of the receiving-end alternating-current system is restored to the rated value, the sending-end converter station controls the alternating-current voltage frequency to be restored to the rated value. According to the method of the invention, neither wind turbine switching nor communication between the converter station and the wind farm is needed, the system is more reliable, and adjustment is quicker.

Description

technical field [0001] The invention relates to the technical field of power transmission and distribution of wind farms, in particular to a DC overvoltage suppression method for a flexible direct current transmission system connected to a wind farm. Background technique [0002] With the large-scale development of wind power, more and more wind power will be sent through the flexible direct current transmission system. However, in the area where the wind farm is located, the strength of the AC grid is weak or there is no AC grid support, so the island operation mode is adopted, and the sending end converter station VSC1 (Voltage Source Converter 1) of the flexible DC transmission system is required to adopt constant AC voltage and constant frequency control to provide AC voltage for the wind farm. With this control method, there will be some disadvantages: [0003] 1. The sending-end converter station VSC1 will be equivalent to an ideal AC power supply, which cannot adjus...

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Problems solved by technology

[0003] 1. The sending-end converter station VSC1 will be equivalent to an ideal AC power supply, which cannot adjust the output power of the wind farm, and all output power of the wind farm will be sent by the flexible direct current transmission system;

[0004] 2. When the receiving-end AC system fails, such as a voltage drop, the output power of the receiving-end converter station VSC2 (Voltage Source Converter 2) will be reduced due to the influence of the current limiting link. If the wind farm cannot reduce the output power in time , there will be an overvoltage on the DC side

If the flexible DC transmission system is in the overvoltage state for a long time, it will threaten the safety of the equipment and cause the entire system to shut down, and the AC grid will lose a large amount of power, posing a serious threat to the stability of the AC system.

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