Pre-charging method and system for hybrid DC converter

Abstract

The invention provides a pre-charging method and system for a hybrid direct current converter. The pre-charging method comprises the following steps: establishing a ring current voltage for an alternating current output unit and a high-voltage sub-module string of the hybrid direct current converter; when the circulating current voltage and the capacitor voltage of the alternating current output unit and the high-voltage sub-module string are stable, generating a circulating current control voltage, and balancing the sub-module capacitor voltage of the alternating current output unit and the high-voltage sub-module string; and after the AC output unit and the sub-module capacitor voltage of the high-voltage sub-module string are balanced, generating a DC control voltage, so that when the AC output unit and the sub-module capacitor voltage of the high-voltage sub-module string continuously rise to a rated voltage, pre-charging is ended. According to the invention, voltage sharing of internal modules of the auxiliary converter can be slowly realized, after voltage sharing of the sub-modules in the auxiliary converter is completed, the direct current side current can be controlled for further charging, and finally all the sub-modules can reach rated values.

Description

technical field [0001] The present invention relates to wind power generation, flexible DC transmission, and power electronics technology in the field of electric power systems, and in particular to a pre-charging method and system for hybrid offshore wind field DC converters constructed with the same sub-module. Background technique [0002] Modular multilevel converter (MMC) has the characteristics of high voltage level, high efficiency and low harmonics, and has become the most competitive converter topology in HVDC transmission. However, due to the large size and weight of MMC, the construction cost of the converter station at sea is high. [0003] The hybrid DC converter is composed of a diode rectifier and a fully-controlled auxiliary converter. The diode rectifier is used to transmit the active power of the wind farm, and the fully-controlled auxiliary converter is used to realize the black start of the wind farm. In the steady state, the compensation system reactive...

AI Technical Summary

Problems solved by technology

However, the structure still has no research on how its auxiliary converter is pre-charged and started when it is built using the same seed module

[0007] To sum up, although a lot of research and development have been done on offshore wind farm DC converters in this field, there is still a lack of an auxiliary converter The technology of pre-charging inverters has limited the application of DC converters in offshore wind farms

[0008] At present, there is no description or report of similar technology to the present invention, and no similar information has been collected at home and abroad

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