Fault Current Suppression Method on DC Side of Converter Based on Additional Virtual Inductance Coefficient

Abstract

The invention relates to a transverter direct current side fault current suppression method based on additional virtual inductance coefficient, belonging to the technical field of flexible direct current power transmission. Firstly, a calculation method of influence of partially cutting a submodule after short circuit fault of a transverter outlet on an alternating current system is put forward, discharge current capacity of an IGBT device and breaking capacity of a direct current breaker are considered comprehensively, a suppression method of transverter direct current side short circuit fault current is put forward, wherein the suppression method can reduce investment proportion of the submodule after fault happens, meanwhile, a fault current suppression method of changing investment proportion of the submodule after fault through mapping the virtual inductance coefficient into a control system is also put forward, and a setting method of the virtual inductance coefficient is also provided. The method, applied to a MMC transverter, can effectively reduce rising rate of the fault current, reduce overcurrent stress of the direct current breaker which cuts off the fault device, andhas good economic efficiency and practicability in comparison with a method of performing fault current suppression through an additional current limiting device.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a method for suppressing a direct current fault current of an MMC converter, in particular to a method for suppressing a direct current side fault current of a converter based on an additional virtual inductance coefficient. Background technique [0002] In 2001, German scholars R.Marquardt and A.Lesnicar proposed a modular multilevel converter (MMC), which promoted the development of high voltage direct current transmission (HVDC) technology. So far, the MMC-HVDC projects that have been put into operation in China include: Shanghai Nanhui Demonstration Project, Nan'ao Project, Zhoushan Project and Xiamen Project. These projects all use cables for power transmission, but compared with overhead lines, the cost of cables is high, and the faults are mostly permanent, which is not easy to repair and maintain. Therefore, it is a trend in the future develo...

AI Technical Summary

Problems solved by technology

However, compared with the half-bridge sub-module, the number and loss of power electronic devices of this type of sub-module have increased, and the economy largely limits their application in practical engineering.

So far, for the DC side fault of the converter, the fault current suppression methods adopted still rely on changing the topology of the sub-modules and adding external current limiting devices to limit the fault current. These current limiting measures all have on-state Due to the high loss and the additional shortcomings of the control system, there is no practice of limiting the fault current of the MMC converter by changing the control measures after the converter fails

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