METHODS AND APPARATUS FOR ACTIVE FRONT END FILTER CAPACITOR DEGRADATION DETECTION

摘要

Apparatus and methods are provided for detecting degradation of delta-connected filter capacitors in an active front end (AFE) power converter, in which delta circuit capacitor leg currents are calculated based on measured branch circuit currents, and filter capacitor impedance values are computed based on the calculated leg currents as well as measured line-to-line voltages and corresponding phase angles for comparison with one or more thresholds to selectively detect degradation of the filter capacitors. Further apparatus and methods are provided for detecting degradation of Y-connected filter capacitors by computation of fundamental frequency RMS impedance values as ratios of RMS capacitor voltages and RMS circuit branch currents, and comparison of the calculated RMS impedance values with one or more thresholds.

主权项

1. A power conversion system, comprising:
a power converter input operative to receive multiphase AC input power; an active front end (AFE) rectifier, comprising a three phase AC input, and a plurality of switching devices operative according to a plurality of rectifier switching control signals to convert power received at the three phase AC input to provide DC output power; an input filter circuit coupled between the power converter input and the AFE rectifier, the input filter circuit comprising first, second, and third series circuits individually including at least one filter inductor coupled between a corresponding phase of the power converter input and a corresponding phase of the three phase AC input of the AFE rectifier, first, second, and third capacitor circuit branches respectively connected to the first, second and third series circuits, and three filter capacitors connected in a delta configuration with each filter capacitor connected to two of the capacitor circuit branches; a feedback circuit operatively coupled with the input filter circuit to sense line-to-line voltages across the filter capacitors and filter circuit branch currents flowing in the capacitor circuit branches; and a degradation detection system operatively coupled with the input filter circuit to calculate fundamental frequency filter capacitor impedance values at least partially according to the line-to-line voltages and according to the filter circuit branch currents, and to selectively detect degradation of one or more of the filter capacitors according to the calculated fundamental frequency filter capacitor impedance values.