A Diagnosis Method for Open Circuit Fault of Switching Tube of NPC Three-level Inverter

Abstract

The invention discloses a method for diagnosing the open-circuit fault of a switching tube of an NPC three-level inverter based on instantaneous amplitude. The invention realizes inverter open-circuit fault diagnosis based on the characteristics of inverter three-phase current. Carry out Park transformation and normalization processing on the three-phase current, use the weighted sliding Hilbert transformation to obtain the instantaneous amplitude, use the instantaneous amplitude and the period average value of the three-phase current to define the fault detection value, and pass the fault detection value and fault threshold To determine the type of failure. The invention uses the weighted sliding Hilbert algorithm to effectively overcome the endpoint effect between data segments, and well overcome the influence of the frequency change of the current signal, and at the same time define the fault detection value to diagnose the fault, reducing the amount of calculation and Complexity of diagnosis.

Description

technical field [0001] The invention relates to the technical field of fault diagnosis, in particular to a method for diagnosing an open-circuit fault of a switching tube of an NPC three-level inverter. Background technique [0002] The NPC type three-level inverter has many advantages such as low loss, low harmonic content of output voltage and current waveforms, small device stress, and large output capacity, and is widely used in photovoltaic microgrids. However, during the operation of the photovoltaic inverter, due to the influence of the environment or other factors, open-circuit faults caused by high electrical or high thermal stress, drive circuit failure or wire breakage may occur. It is the weak link most prone to open-circuit faults in the transformer system. In order to ensure the reliable operation of the NPC type three-level inverter in the actual operating environment, higher requirements are put forward for the timeliness and accuracy of the fault diagnosis ...

AI Technical Summary

Problems solved by technology

[0004] Current diagnosis methods for inverter open-circuit faults can be divided into the following categories: ① Current Park vector slope method, when detecting open-circuit faults, is susceptible to interference from factors such as load disturbance and instantaneous changes, resulting in false positives under small loads and false positives under transient changes

②The characteristic parameter method of the switching device needs to introduce new collection points to obtain the characteristic parameters, which increases the complexity of the system, is not conducive to the improvement of the reliability of the system, and also increases the cost

③The normalized DC method is mainly to solve the problem of misdiagnosis caused by load disturbance in the process of fault diagnosis. The normalized DC flow is used to complete the diagnosis and positioning of the open circuit of the power tube, but the calculation is large and there is a delay in diagnosis

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