Modularized multi-level converter fault diagnosis method based on Luenberger observer

Abstract

The invention discloses a modular multi-level converter fault diagnosis method based on a Luenberger observer in the technical field of multi-level power electronic converters. The fault diagnosis method comprises the following steps: step 1, acquiring required data; 2, obtaining a mathematical relationship of the change of the capacitor voltage uc of the sub-module; 3, calculating a predicted state estimated value ucp (k) of the capacitor voltage of the sub-module at the moment k and an optimal estimated value ucc (k) of the capacitor voltage of the sub-module at the moment k; and 4, judging whether the sub-module has a fault or not. According to the fault diagnosis method, fault detection and positioning can be realized at the same time, and the open-circuit fault and the short-circuit fault of the sub-module can be diagnosed more accurately and timely; the detection algorithm is simple and small in calculation amount, is not influenced by the uncertainty of system parameters, has high robustness, does not need to make any change on a hardware circuit, is easy to understand and implement, does not need to introduce circulating current into the system, and does not change the output characteristics of the system.

Description

technical field [0001] The invention relates to the technical field of multi-level power electronic converters, in particular to a fault diagnosis method for a modular multi-level converter based on a Lumberg observer. Background technique [0002] Compared with the traditional two-level and three-level converters, the Modular Multilevel Converter (MMC) has the characteristics of high efficiency, small output AC voltage harmonics, high modularity, etc., and is more suitable for high voltage , high-power applications, and has broad application prospects in the fields of flexible DC transmission, medium-voltage motor drives, etc. [0003] By dividing bulk DC capacitors into smaller capacitors, series connected submodules (SMs) can be used in MMCs. This unique structure results in no bulk DC capacitors, lower switching synchronization requirements and a higher degree of modularity. However, a large number of serial sub-modules pose a huge threat to MMC reliability as they bec...

AI Technical Summary

Problems solved by technology

These methods need to perform fault detection and fault location separately, and the detection algorithm is relatively complicated, which not only increases the calculation amount of the detection algorithm, but also complicates the fault diagnosis process.

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