Method for positioning open-circuit fault of upper tube of half-bridge sub-module of modular multilevel converter

Abstract

The invention discloses a method for positioning an open-circuit fault of an upper tube of a half-bridge sub-module of a modular multilevel converter. The aim of diagnosing and positioning a fault sub-module is achieved by judging whether the capacitance current of the sub-module is positive or negative. The capacitor current of the sub-module is used as a characteristic parameter of fault diagnosis, and analysis shows that the capacitor current of the sub-module has positive and negative values under the normal operation condition, that is, the capacitor of the normal sub-module can be normally charged and discharged, and after an upper tube open-circuit fault occurs, the capacitor of the fault sub-module cannot be normally discharged. Therefore, the capacitor current of the sub-module does not have a negative value, and the fault sub-module can be diagnosed and positioned according to the characteristic. A sub-module of the modular multilevel converter is of a half-bridge structure, and an upper bridge arm and a lower bridge arm of each phase are respectively formed by cascading N sub-modules. According to the method, the problem that the change of the capacitor voltage of the normal sub-module and the change of the capacitor voltage of the fault sub-module are consistent under the condition that the open-circuit fault of the upper tube of the sub-module occurs under the sorting voltage-sharing algorithm is well solved.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a method for locating an open-circuit fault on an upper tube of a half-bridge sub-module of a modular multilevel converter. Background technique [0002] Modular Multilevel Converter (ModularMultilevel Converter, Modular Multilevel Converter) is a new voltage source converter topology proposed by R.Marquardt and A.Lesnicar in 2002. It has low device withstand voltage change rate and expandability Strong, low switching loss, easy redundant design and many other advantages, so it has broad application prospects in the fields of high-voltage DC transmission, asynchronous interconnection of AC power grids, train traction, wind farm access, and offshore platform power supply. In the modular multilevel converter system, a large number of switching devices are used. When the system is not operating normally or the operating mode changes suddenly, it is often accompanied by ove...

AI Technical Summary

Problems solved by technology

This method can not only effectively solve the problem that the capacitor voltage of all sub-modules of the bridge arm where the faulty sub-module is located rises synchronously under the control of the carrier stacked modulation strategy and the sorting voltage equalization algorithm, and the faulty sub-module cannot be identified, but also can quickly diagnose and locate multiple faults The upper tube of the sub-module is open-circuit faulty

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