Fault Diagnosis Method for Modular Multilevel Inverter Based on State Observation

Abstract

The invention discloses a modular multilevel inverter fault diagnosis method based on extended state observation, which is divided into two stages of fault detection and fault location determination. In the fault detection stage, the output matching module compares the observed value of the expanded state variable after amplification, filtering, and compensation with the calculated value of the expanded state variable after filtering under normal operating conditions, and judges the modular multilevel according to the comparison result Whether the inverter is faulty; in the stage of determining the fault location, the output matching module will compare the calculated values ​​of the expanded state variables after filtering under the hypothetical fault location with the expanded state variable observations of the observer module output after amplification, filtering and compensation. Values ​​are compared, and the fault location of the modular multilevel inverter is determined according to the comparison result. The invention is committed to using the extended state observer and the modified switch state variable to judge whether the modular multilevel inverter is faulty and to determine the fault location quickly and accurately.

Description

technical field [0001] The invention belongs to the field of fault diagnosis of modular multilevel inverters, and in particular relates to a fault diagnosis method for modular multilevel inverters based on state observation. Background technique [0002] A modular multilevel converter (Modular Multilevel Converter, referred to as a modular multilevel inverter) is a kind of multilevel converter emerging in recent years. The structure of the modular multilevel inverter was first proposed by Professor R.Marquardt in 2001. Compared with the traditional multilevel inverter structure, the outstanding advantages of the modular multilevel inverter include: 1) Highly modular, so that this kind of inverter can realize the application of any voltage level through cascading modules; 2) The harmonic characteristics are good, due to the cascading of the same modules, the number of levels is large, and the AC output side does not need to use filters ; 3) Strong redundancy and fault tolera...

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Problems solved by technology

[0006] However, although the above several fault diagnosis methods can modularize the function of multi-level inverter fault diagnosis, they all have their own defects.

For example, in the synovium observer method, multiple physical quantities need to be observed and compared, which increases the complexity of the algorithm; while in the Kalman filter method, although there is only one physical quantity to be observed and compared, compared with the synovium observation The device method, the algorithm is simple, but because it only determines the fault location by comparing the measured value of the capacitor voltage of each module, it can only determine the fault module, but cannot specifically determine the fault switch device

The defects of the above methods have affected their use in fault diagnosis

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