Offshore wind power transmission control system and control method through hybrid direct current

Abstract

The invention discloses a control system for sending offshore wind power via hybrid direct current and a control method thereof. The control method first unlocks the onshore converter station when the system is started, and controls the direct current voltage of the onshore converter station to be a first preset voltage value, and then unlock the offshore MMC converter valve, and then start some wind turbines. By reducing the DC voltage of the onshore converter station, the DC voltage of the offshore DR converter valve is reduced to the preset voltage threshold, so that the offshore DR The converter valve is turned on and starts to transmit DC power, and then the remaining offshore wind turbines are started. By controlling the DC voltage of the onshore converter station to further reduce, the transmission power of the offshore DR continues to rise, so that all the DC power passes through the offshore DR converter valve. Instead of the offshore MMC converter valve being injected into the DC side, the loss of the small-capacity offshore MMC converter valve during long-term operation is reduced, the economy is improved, the overload of the offshore MMC converter valve is avoided, and the safe and stable operation of the system is ensured.

Description

technical field [0001] The invention relates to the technical field of direct current transmission, in particular to a control system and a control method for sending offshore wind power through hybrid direct current. Background technique [0002] In recent years, flexible direct current transmission technology (English full name voltage source converter based high-voltage direct current, English abbreviation VSC-HVDC) has achieved rapid development. At the same time, because the flexible DC can quickly and flexibly control the output power of the wind farm, and can independently control the bus voltage and frequency of the grid-connected point of the wind farm, use the flexible DC method to connect the power of the wind farm and transmit it to the onshore grid. It is used in practical projects at home and abroad. [0003] However, the existing offshore wind power is sent to offshore converter stations and onshore converter stations via flexible DC. Increase, the volume an...

AI Technical Summary

Problems solved by technology

However, the above control method changes the AC voltage amplitude of the offshore wind farm significantly and frequently, and the voltage fluctuation range may exceed 0.1pu

Substantially changing the AC voltage on the AC side of the entire offshore wind farm and offshore converter station will have a large impact range, which may cause frequent switching of reactive power compensation devices equipped with wind farms, and may even affect the safe and stable operation of offshore wind turbines. Cause the fan to go off the grid

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