A combined flexible DC fault current limiting method considering bridge arm current suppression

Abstract

The invention discloses a joint limiting method of flexible DC fault current considering bridge arm current suppression, which includes: extracting the equivalent resistance, equivalent inductance and equivalent capacitance parameters of the converter, the inductance value of the smoothing reactor, and the rated DC voltage , current inner loop PI proportional parameter and integral parameter; set the corner frequency of DC current suppression control according to fault current suppression requirements, and calculate the switching coefficient of the converter; in the inner loop current control link, add bridge arm current suppression control; unlock the commutation station; set the short circuit fault between DC poles; when it is detected that the DC current rise rate exceeds U dcN / 2L dc When , the DC suppression control is started, and the initial switching coefficient of the converter is changed to the calculated adaptive switching coefficient K c ; At the same time put into bridge arm current suppression control. The invention achieves the purpose of suppressing the DC fault current, reduces the requirement on the breaking capacity of the DC circuit breaker, prevents the converter from being blocked before the DC circuit breaker operates, and ensures that the transmission of active power is not interrupted during the fault period.

Description

technical field [0001] The invention relates to the field of high voltage direct current transmission technology control based on voltage source converters, in particular to a flexible direct current fault current combined limiting method considering bridge arm current suppression. Background technique [0002] The high-voltage direct current transmission technology (VSC-HVDC) based on the voltage source converter is an effective technical approach for the asynchronous interconnection of modern power systems and the integration of renewable energy into the grid, especially for the high-voltage and large-capacity transmission of modular multilevel converters (MMCs). The ability makes it an inevitable choice for DC grid engineering construction, but compared with thyristors, fully-controlled electronic devices in MMC are more likely to be damaged by overcurrent when they fail, hindering the development of DC grids. [0003] The common method of suppressing fault current is to ...

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Problems solved by technology

A Modular Multilevel Converter with DC Fault Current Limiting Capability (Hao Ruixiang, Yang Xiaofeng, Xue Yao, Chen Bowei, Lin Zhiqin, Sun Hu. A Modular Multilevel Converter with DC Fault Current Limiting Capability .Journal of Electrotechnical Society), which achieves fault current limiting by adding blocking IGBT and its bypass absorption circuit at the AC output port. In this suppression method, the improved sub-module topology adds IGBT and its bypass absorption circuit, increasing the Equipment investment, and cannot be applied to existing projects

The fault current suppression control strategy based on virtual inductance (Li X, Li Z, Zhao B, et al. HVDC Reactor Reduction Method Based on Virtual Reactor Fault Current Limiting Control of MMC.IEEETransactions on Industrial Electronics, 2019), by controlling the capacitance of the sub-module The degree of discharge establishes virtual reactance to achieve the purpose of fault current limiting; adaptive fault current suppression control strategy (Ni B, Xiang W, Zhou M, et al. An Adaptive Fault Current Limiting Control for MMC and Its Application in DC Grid. IEEE Transactions on Power Delivery, 2020), by adaptively changing the number of input sub-modules to achieve the purpose of current limiting; these two methods only consider the suppression of DC fault current, but not the suppression of bridge arm current, and cannot guarantee that the converter station Uninterrupted power delivery during faults

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