Method and system for evaluating DC fault ride-through capability of modular multilevel converters

Abstract

The invention relates to a method and a system for evaluating the DC fault crossing capability of a modularized multi-level transverter and belongs to the DC power transmission technology field. According to the method, the fault current integration of a to-be-investigated topology MMC and the largest sub module voltage deviation after fault generation are calculated firstly; taking the fault current integration of a half bridge MMC having the same quantity of capacitors as the to-be-investigated topology MMC and the largest sub module voltage deviation after fault generation as reference, per-unit processing on the fault current integration of the to-be-investigated topology MMC and the largest sub module voltage deviation after fault generation is carried out; results after per-unit processing are respectively multiplied by corresponding weight coefficients and are then summed to acquire a value, and the acquired value is the DC fault crossing capability evaluation result of the to-be-investigated topology MMC. Through the method, quantitative evaluation on the DC fault crossing capability of various types of topologies MMC can be carried out from two aspects of the fault current inhibition capability and the sub module overvoltage degree after fault generation, and comprehensive evaluation on the MMC is realized.

Description

technical field [0001] The invention relates to a method and system for evaluating the DC fault ride-through capability of a modular multilevel converter, belonging to the technical field of DC transmission. Background technique [0002] DC fault is a common fault in the operation of MMC flexible DC transmission system. The traditional half-bridge sub-module MMC cannot quickly suppress the fault current through its own characteristics when a DC short-circuit fault occurs, and must rely on AC circuit breakers or DC circuit breakers to clear it. fault current. On the one hand, due to the long response time of the AC circuit breaker, the protection may not be timely and cause overcurrent damage to the converter; on the other hand, the configuration of the DC circuit breaker increases the technical requirements for the equipment and increases the system cost. In order to solve the DC fault ride-through problem of the MMC flexible DC transmission system, in 2010, German scholar ...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a method and system for evaluating the DC fault ride-through capability of modular multilevel converters, so as to solve the problem that the evaluation results are relatively one-sided due to the current fault current suppression capability only used to evaluate the fault ride-through capability

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