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US 9,294,005 B2Granted
Method and apparatus for detecting AFE filter capacitor degradation
AssigneeRockwell Automation Technologies, Inc.
InventorsRangarajan Tallam, Russel Kerkman
Life of this patent
Estimating the term…
Abstract
Methods and systems are disclosed for detecting capacitor degradation in an input filter of an active front end power conversion system in which voltage and current sensing is performed to determine sequence component impedance asymmetry to detect filter capacitor degradation according to the value of an off-axis admittance matrix component for Delta or Y-connected filter capacitor banks without sensitivity to voltage unbalance, and with the capability to identify particular degraded capacitor locations based on individual impedance values.
Claims17
A power conversion system, comprising:
- an active front end rectifier, comprising a multiphase AC input, and a plurality of switching devices operative according to a plurality of rectifier switching control signals to convert power received at the multiphase AC input to provide DC output power;
- an input filter circuit coupled between a power converter input and the active front end rectifier, the input filter circuit comprising a plurality of filter inductors coupled between a corresponding phase of the power converter input and a corresponding phase of the multiphase AC input of the active front end rectifier, and a capacitor circuit including a plurality of filter capacitors individually connected to at least one of the plurality of filter inductors;
- a sensing circuit operative to determine a plurality of measured currents and measured voltages associated with the input filter circuit;
- and
- a degradation detection system operatively coupled with the input filter circuit and comprising at least one processor configured to:
- compute fundamental frequency current and voltage phasors based on the measured currents and voltages,
- compute positive and negative sequence current and voltage component phasors based on the computed fundamental frequency current and voltage phasors,
- compute at least one off-diagonal term of a filter circuit admittance matrix based on at least one of the computed positive and negative sequence current and voltage component phasors,
- compare the at least one off-diagonal term to at least one threshold, and
- selectively detect degradation of one or more of the filter capacitors if the at least one off-diagonal term exceeds the at least one threshold.
7 more elements
A method for detecting filter capacitor degradation in an input filter of an active front end power conversion system, the method comprising:
- determining a plurality of measured currents and measured voltages associated with the input filter circuit;
- computing fundamental frequency current and voltage phasors based on the measured currents and voltages;
- computing positive and negative sequence current and voltage component phasors based on the computed fundamental frequency filter current and voltage phasors;
- computing at least one off-diagonal term of a filter circuit admittance matrix based on at least one of the computed positive and negative sequence current and voltage component phasors;
- comparing the at least one off-diagonal term to at least one threshold;
- and
- selectively detecting degradation of one or more of the filter capacitors if the at least one off-diagonal term exceeds the at least one threshold.
4 more elements
A power conversion system, comprising:
- an active front end rectifier, comprising a multiphase AC input, and a plurality of switching devices operative according to a plurality of rectifier switching control signals to convert power received at the multiphase AC input to provide DC output power;
- an input filter circuit coupled between the power converter input and the active front end rectifier, the input filter circuit comprising a plurality of filter inductors coupled between a corresponding phase of the power converter input and a corresponding phase of the multiphase AC input of the active front end rectifier, and a capacitor circuit including a plurality of filter capacitors individually connected to at least one of the plurality of filter inductors;
- a sensing circuit operative to determine a plurality of measured currents and measured voltages associated with the input filter circuit;
- and
- a degradation detection system operatively coupled with the input filter circuit and comprising at least one processor configured to:
- compute an effective neutral voltage value based on the measured voltages,
- compute an effective neutral voltage mean value based on the effective neutral voltage value,
- compute a nominal effective neutral voltage value based on the effective neutral voltage value and the effective neutral voltage mean value,
- compute an effective current value based on the measured currents,
- compute an effective current mean value based on the effective current value,
- compute a nominal effective current value based on the effective current value and the effective current mean value,
- compute an effective current fault value based on the nominal effective current value, an estimated admittance value, and the nominal effective neutral voltage value,
- compare the effective current fault value to at least one threshold, and
- selectively detect degradation of one or more of the filter capacitors if the effective current fault value exceeds the at least one threshold.
11 more elements
A method for detecting filter capacitor degradation in an input filter of an active front end power conversion system, the method comprising:
- determining a plurality of measured currents and measured voltages associated with the input filter circuit;
- computing an effective neutral voltage value based on the measured voltages,
- computing an effective neutral voltage mean value based on the effective neutral voltage value,
- computing a nominal effective neutral voltage value based on the effective neutral voltage value and the effective neutral voltage mean value,
- computing an effective current value based on the measured currents,
- computing an effective current mean value based on the effective current value,
- computing a nominal effective current value based on the effective current value and the effective current mean value,
- computing an effective current fault value based on the nominal effective current value, an estimated admittance value, and the nominal effective neutral voltage value,
- comparing the effective current fault value to at least one threshold, and
- selectively detecting degradation of one or more of the filter capacitors if the effective current fault value exceeds the at least one threshold.
7 more elements
Dependencies are inferred from the claim text.