METHOD FOR DIAGNOSING STATE OF CAPACITOR IN MODULAR CONVERTER

1 . A method for diagnosing a state of a capacitor in a modular converter, comprising:

setting a Failures in Time (FIT) table depending on an input voltage and a temperature of an internal capacitor for multiple sample modular converters;

detecting, by an input voltage detection unit, an input voltage of a capacitor in a target modular converter, a state of the capacitor of which is to be diagnosed, during a preset period;

detecting, by a temperature detection unit, a temperature of the capacitor of the target modular converter during the preset period;

calculating a cumulative mean for the input voltage and the temperature, which are respectively detected by the input voltage detection unit and the temperature detection unit during the preset period;

selecting, by a control unit, a FIT value, corresponding to the calculated cumulative mean for the input voltage and temperature, from the FIT table; and

extracting a Mean Time Between Failures (MTBF) of the capacitor from the FIT value.

2 . The method of claim 1 , wherein the setting the FIT table comprises:

determining a FIT value based on an input voltage and a temperature of the capacitor for each of the multiple sample modular converters;

generating a FIT graph from the determined FIT value for each of the multiple sample modular converters; and

setting the FIT table by extracting a FIT value, corresponding to preset ranges of the input voltage and temperature, from the FIT graph.

3 . The method of claim 1 , wherein the extracting the MTBF comprises:

calculating a failure rate (λ) for the multiple sample modular converters using (N=N 0 ×e −λt ); and

extracting the MTBF from the failure rate (λ) and the FIT value, using (MTBF=λ×FIT value).

4 . The method of claim 1 , further comprising

after the extracting the MTBF,

generating a warning sound when a failure occurrence time, predicted based on the extracted MTBF of the capacitor, arrives.