Method and system for detecting incipient failures in a power inverter

• US 6,291,987 B1
• Filed: 01/06/2000
• Issued: 09/18/2001
• Est. Priority Date: 10/28/1999
• Status: Expired due to Term

• Current Assignee: GE Global Sourcing LLC (Westinghouse Air Brake Technologies Corporation)
• Original Assignee: General Electric Company
• Inventors: Redinger, Kristopher L., Kumar, Ajith K., Dean, Jason A., Worden, Bret D.
• Primary Examiner(s): Brown, Glenn W.
• Assistant Examiner(s): Hamdan, Wasseem H.
• Application Number:
  US09/478,670
• Time in Patent Office: 621 Days
• Field of Search: 324/164, 324/158.1, 324/765, 324/537, 324/772, 363/58, 363/55
• US Class Current: 324/764.01
• CPC Class Codes: G01R 31/42 AC power supplies
• CPC Class Codes: H02M 7/521 in a bridge configuration

Abstract

A method and system for predicting malfunctions in a power inverter having one or more legs connected between first and second voltage buses is provided. Each leg has respective first and second controllable switches coupled in series to one another. The method allows for applying predetermined respective voltages at the first and second buses. The method further allows for selectively actuating the first and second switches between respective conductive or non-conductive states. A monitoring step allows for monitoring predetermined electrical parameters generated in the inverter in response to the applied voltages as the first and second switches are respectively actuated, and an adjusting step allows for adjusting the respective values of the monitored electrical parameters for deviations from respective estimated nominal values due to predetermined external variables to generate adjusted electrical parameters that in turn may be used to determine the performance of the power inverter, including detection of incipient failures.

Claims

1. A method for determining degradation of a power inverter having at least a first leg connected between first and second voltage buses, each leg having respective first and second controllable switches coupled in series to one another, the method comprising:

applying respective voltages at the first and second buses;

selectively actuating the first and second switches between respective conductive or non-conductive states;

sensing one or more electrical parameters generated in the inverter in response to the applied voltages with actuation of at least one of the switches, and generating a first set of electrical parameter values, with the electrical parameter values being influenced at least in part by a first set of operational and environmental conditions of the inverter;

determining at least one variable associated with the inverter at the time of the sensing of the electrical parameters, said at least one variable being indicative of the first set of operational and environmental conditions of the inverter;

providing a database of nominal inverter values based on data collected from a fleet of inverters corresponding to the inverter whose performance is being determined, the nominal inverter values constituting a second set of electrical parameter values relative to a second set of operational and environmental conditions for the inverters;

accessing the database in light of the first set of operational and environmental conditions;

adjusting the respective values of one of the first and second sets of parameter values relative to the other to account for differences between the first and second sets of operational and environmental conditions; and

comparing the respective set of adjusted values against said other set of parameter values to determine the relative performance of the inverter to the fleet of inverters for detection of incipient failures of the inverter.

2. The method of claim 1 wherein the first set of parameter values is adjusted relative to the differences between the first and second sets of operational and environmental conditions.

3. The method of claim 1 wherein the second set of parameter values is adjusted relative to the differences between the first and second sets of operational and environmental conditions.

4. The method of claim 1 further comprising storing the adjusted values over time and determining trends in the adjusted values indicative of incipient failures of the inverter.

5. The method of claim 1 wherein said method is locally performed relative to the inverter.

6. The method of claim 1 further comprising transmitting the one or more electrical parameters generated by the inverter to a remote site and the comparing is performed at the remote site to determine the performance of the inverter.

7. The method of claim 1 wherein the step of sensing the one or more electrical parameters comprises sensing voltage at a node intermediate the switches.

8. The method of claim 1 wherein the step of sensing the one or more electrical parameters comprises sensing current flow through the at least one leg.

9. The method of claim 1 wherein the converter further comprises second and third legs in addition to the at last first leg, each node intermediate each serially connected first and second switches in each respective leg being coupled to a respective power input terminal of a three phase AC electric traction motor and wherein the actuation of the first and second switches of any of the legs comprises actuating any one switch of two different legs in a conductive state while each remaining switch remains in a nonconductive state.

10. The method of claim 9 further comprising a stop of storing a second range of values so that respective adjusted parameter values within that second range are indicative of incipient malfunctions of the inverter.

11. The method of claim 10 wherein respective adjusted parameter values beyond that second range of values are indicative of unacceptable inverter performance.

12. The method of claim 1 further comprising a step of storing a first range of values so that respective adjusted parameter values within that first range are indicative of satisfactory inverter performance.

13. The method of claim 1 wherein the variable of the inverter is selected from the group consisting of ambient air temperature, barometric pressure, traction motor stator temperature, traction motor rotor temperature, motor RPM, inverter air flow, system age, and expected variation from inverter-to-inverter.

14. A system for determining degradation of a power inverter having at least a first leg connected between first and second voltage buses, each leg having respective first and second controllable switches coupled in series to one another, the system comprising:

a module configured to apply respective voltages at the first and second buses;

a switch-actuation module configured to selectively actuate the first and second switches between respective conductive or non-conductive states;

at least one sensor configured to sense one or more electrical parameters generated in the inverter in response to the applied voltages with actuation of at least one of the switches, and further configured to generate a first set of electrical parameter values, with the electrical parameter values being influenced at least in part by a first set of operational and environmental conditions of the inverter;

a module for determining at least one variable associated with the inverter at the time of the sensing of the electrical parameters, said at least one variable being indicative of the first set of operational and environmental conditions of the inverter;

a database of nominal inverter values based on data collected from a fleet of inverters corresponding to the inverter whose performance is being determined, the nominal inverter values constituting a second set of electrical parameter values relative to a second set of operational and environmental conditions for the fleet of inverters;

a processor configured to access the database in light of the first set of operational and environmental conditions, the processor including;

an adjuster module configured to adjust the respective values of one of the first and second sets of parameter values relative to the other to account for differences between the first and second sets of operational and environmental conditions; and

a comparator configured to compare the respective set of adjusted values against said other set of parameter values to determine the relative performance of the inverter to the fleet of inverters for detection of incipient failures of the inverter.

15. The system of claim 14 wherein the first set of parameter values is adjusted relative to the differences between the first and second sets of operational and environmental conditions.

16. The system of claim 14 wherein the first set of parameter values is adjusted relative to the differences between the first and second sets of operational and environmental conditions.

17. The system of claim 14 wherein said system is locally situated relative to the inverter.

18. The system of claim 14 further comprising a communications device configured to transmit the electrical parameters generated by the inverter to a remote site and the processor is located at the remote site to determine the performance of the inverter.

19. The system of claim 14 wherein the at least one sensor is configured to sense voltage at a node intermediate the switches.

20. The system of claim 14 wherein the at least one sensor is configured to sense current flow through the at least one leg.

21. The system of claim 14 further comprising memory for storing the adjusted values over time and determining trends in the adjusted values indicative of incipient failures of the inverter.

22. The system of claim 14 wherein the converter further comprises second and third legs in addition to the at least first leg, each node intermediate each serially connected first and second switches in each respective leg being coupled to a respective power input terminal of a three phase AC electric traction motor and wherein the actuation of the first and second switches of any of the legs comprises actuating any one switch of two different legs in a conductive state while each remaining switch remains in a nonconductive state.

23. The system of claim 14 wherein the variable of the inverter is selected from the group consisting of ambient air temperature, barometric pressure, traction motor stator temperature, traction motor rotor temperature, motor RPM, inverter air flow, system age, and expected variation from inverter-to-inverter.