A bridge arm circuit and method for suppressing fault current of a large-capacity mmc sub-module

Abstract

A bridge arm circuit and method for suppressing a fault current of a large-capacity MMC sub-module, mainly aiming at suppressing the fault current of a large-capacity MMC sub-module. In the large-capacity MMC bridge arm design scheme, each bridge arm (phase unit) in the converter is designed as a whole, and the bridge arm reactor is dispersed, and the reactance is arranged on the DC side and the AC side of each bridge arm. device. The total inductance value of the reactor in each bridge arm remains unchanged, and the weight coefficient of the bridge arm reactance occupied by the AC and DC side reactance is checked according to the system parameters. Each bridge arm is connected to the outside of the bridge arm through a reactor at the AC side and at the outlet of the DC connection. Adopting the bridge arm design scheme proposed in the patent of the present invention can effectively reduce the peak value of the fault current of the sub-module and suppress the rising rate of the fault current, thereby improving the utilization rate of the power device in the equipment, and does not increase the cost of the primary equipment, and has a good economy sex.

Description

technical field [0001] The invention belongs to the field of new energy and electric power engineering, and relates to a converter flexible DC power transmission technology, in particular to a bridge arm circuit and a method for suppressing fault current of a large-capacity MMC sub-module. Background technique [0002] The modular multilevel voltage source converter (MMC) based on fully controlled power electronic devices, based on the second generation of flexible DC transmission technology, has all the advantages of the voltage source converter (VSC), including the ability to Independent control of active and reactive power, no commutation failure, ability to supply power to passive islands, etc., are favored by academia and industry. At the same time, the MMC system also has the characteristics of low switching frequency, low switching loss, no need for AC filter banks and strong scalability, which makes it suitable for high DC voltage and high power transmission occasion...

AI Technical Summary

Problems solved by technology

In a symmetrical bipolar MMC system, if a serious fault occurs in the converter station, it will cause an overcurrent problem in the fully controlled power electronic device in the sub-module, and in severe cases, it may cause damage to the power device

[0004] To solve this problem, the industry mainly solves this problem by increasing the steady-state margin of device selection, reducing the protection setting value in the control and protection system, or adding primary equipment. However, the above solutions can improve the overcurrent of sub-modules on the one hand. Limited and low device utilization, on the other hand, it increases the cost of equipment, and the economy is poor

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