Hybrid offshore wind field direct current converter auxiliary converter and control method

Abstract

The invention provides a hybrid offshore wind field direct current converter auxiliary converter and a control method. The control method comprises the steps of controlling the error of a sub module capacitor voltage rated value and a sub module string capacitor voltage sampling average value by adopting a PI regulator, outputting a ring current set signal amplitude value, and enabling the ring current set signal amplitude value to be multiplied with a unit standard sine wave signal to obtain a ring current set instantaneous value; obtaining an auxiliary converter internal ring current by calculating the difference value between the direct current side output current of the auxiliary converter and sub module string current, and controlling the error between the ring current set instantaneous value and the auxiliary converter internal ring current by adopting a first proportional regulator to obtain a ring current control voltage; and enabling the ring current control voltage, the sub module string direct current output voltage and the sub module string high-frequency voltage to be summed to obtain a modulation reference voltage of the sub module string. By virtue of ring current control, internal energy stability is realized, the auxiliary circulator can perform stable operation, bidirectional power transmission is realized, and reversed power transmission in the wind field starting stage can be realized.

Description

technical field [0001] The present invention relates to the field of electric power technology, in particular to an auxiliary converter and a control method of a hybrid offshore wind field direct current converter. Background technique [0002] The flexible DC transmission technology based on Modular Multilevel Converter (MMC) is developing rapidly. MMC uses sub-modules to build high-voltage and large-capacity AC / DC converters, which have the advantages of low harmonics and low loss, and become a DC power transmission technology. The most attractive converter topology in power transmission technology. However, with the increase of the voltage level, the number of MMC sub-modules has increased significantly. For DC transmission applications in offshore wind farms, the construction cost of offshore platforms is high, and the full MMC solution further increases the system cost. [0003] The diode rectifier has low cost and simple control, which can greatly reduce the cost, vol...

AI Technical Summary

Problems solved by technology

However, with the increase of the voltage level, the number of MMC sub-modules has increased significantly. For DC transmission applications in offshore wind farms, the construction cost of offshore platforms is high, and the use of full MMC solutions further increases system costs.

[0003] The diode rectifier has low cost and simple control, which can greatly reduce the cost, volume and weight of the converter. However, the diode rectifier cannot actively establish the voltage of the wind farm internal network, and a special wind power converter control strategy needs to be designed, and the power cannot be reversed. transmission, and will generate large harmonic current

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