Bridge arm circuit and method inhibiting fault current of large-capacity MMC submodule

Abstract

The invention provides a bridge arm circuit and method inhibiting a fault current of a large-capacity MMC submodule, and mainly aims at inhibition of the fault current of the large-capacity MMC submodule. In a design scheme of bridge arms of a large-capacity MMC, each bridge arm (phase unit) in the converter is designed as an integral body, and reactors are arranged in DC and AC sides of each bridge arm respectively in a manner that bridge arm reactors are dispersed. The total inductance value of the reactors in each bridge arm is kept constant, and the weight coefficients of the reactance in the AC and DC sides in the reactance of the bridge arm are checked according to system parameters. Each arm is connected to the external via the reactors in the AC and DC wire outlets. The bridge arm design scheme of the invention can be used to reduce the peak value of the fault current of the submodule and inhibit the rise rate of the fault current effectively, and further improve utilization rate of power devices in equipment, the cost of primary equipment is not increased, and the economical performance is high.

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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