Power converter resonance detection apparatus and method

Patent metadata

Field	Value
Publication number	US-9667128-B2
Application number	US-201213570919-A
Country	US
Kind code	B2
Filing date	Aug 9, 2012
Priority date	Apr 30, 2012
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

Power conversion systems and methods are presented for detecting filter capacitor resonance conditions in a power conversion system in which filter currents are measured and filtered using a bandpass filter, and one or more computed mean, RMS, and/or Fourier transform values are computed based on the filtered value(s). The computed measurement value or values are compared with a predetermined threshold and a suspected filter capacitor resonance condition is selectively identified based on comparison result.

First claim

The following is claimed:

1. A power conversion system, comprising:
an AC input coupleable to receive AC input power from a power source;
a rectifier operative to convert the AC input power to provide a DC output;
an inverter operatively coupled with the DC output of the rectifier to provide an AC output;
a filter circuit coupled between the AC input and the rectifier, the filter circuit comprising a plurality of filter capacitors; and
a controller operative to identify a suspected resonance condition in the filter circuit if a component of at least one filter current flowing in at least one of the filter capacitors in a predetermined frequency band exceeds a predetermined threshold, and to chan e an operating state of the power conversion system or an external device in response to identification of the suspected resonance condition in the filter circuit.

2. The power conversion system of claim 1 , wherein the controller comprises a bandpass filter operative to determine the component of the at least one filter current in the predetermined frequency band, the bandpass filter having an upper cutoff frequency below a switching frequency of the rectifier, and a lower cutoff frequency above a fundamental frequency of the at least one filter current signal or value.

3. The power conversion system of claim 2 , wherein the upper cutoff frequency is about 2,200 Hz or less and wherein the lower cutoff frequency is about 500 Hz or more.

4. The power conversion system of claim 3 , wherein the lower cutoff frequency is about 600 Hz or more.

5. The power conversion system of claim 3 , wherein the controller samples the at least one filter current at a sample frequency of about 22 KHz or more.

6. The power conversion system of claim 2 , wherein the controller is operative to identify a suspected resonance condition in the filter circuit if a mean value of the component of the at least one filter current in the predetermined frequency band exceeds the predetermined threshold.

7. The power conversion system of claim 6 , wherein the filter circuit is an LCL circuit with first and second inductors connected in series with one another between each input terminal of the AC input and a corresponding input phase of the rectifier, with at least one of the plurality of filter capacitors connected to a center node between the first and second inductors, and wherein the at least one filter current represents at least one line current flowing in one or more of the second inductors of the filter circuit.

8. The power conversion system of claim 2 , wherein the controller is operative to identify a suspected resonance condition in the filter circuit if an RMS value of the component of the at least one filter current in the predetermined frequency band exceeds the predetermined threshold.

9. The power conversion system of claim 8 , wherein the filter circuit is an LCL circuit with first and second inductors connected in series with one another between each input terminal of the AC input and a corresponding input phase of the rectifier, with at least one of the plurality of filter capacitors connected to a center node between the first and second inductors, and wherein the at least one filter current represents at least one line current flowing in one or more of the second inductors of the filter circuit.

10. The power conversion system of claim 1 , wherein the controller is operative to identify a suspected resonance condition in the filter circuit if a total harmonic distortion value in the predetermined frequency band of a Fourier transform of the at least one filter current exceeds the predetermined threshold.

11. The power conversion system of claim 1 , wherein the controller is operative to adjust the predetermined threshold based on a measured condition in the power conversion system.

12. The power conversion system of claim 1 , wherein the predetermined threshold is determined according to at least one of a power conversion system frame size, a power converter voltage class and a tolerance value associated with the filter capacitors.

13. The power conversion system of claim 1 , wherein the controller is operative to change the operating state of the power conversion system or the external device in response to identification of the suspected resonance condition in the filter circuit by at least one of:
opening a main circuit breaker of the power conversion system;
initiating a controlled shutdown of the power conversion system;
indicating the suspected resonance condition on a user interface of the power conversion system;
logging a fault in the power conversion system; and
storing a value to a fault log in a nonvolatile memory of the power conversion system.

14. The power conversion system of claim 1 , wherein the controller is operative to change the operating state of the power conversion system or the external device in response to identification of the suspected resonance condition in the filter circuit by at least one of:
sending an error message to a supervisory controller associated with the power conversion system;
indicating a non-resettable fault to a human machine interface for different levels of suspected resonance according to a relative comparison with the predetermined threshold; and
allowing a fault to be reset upon input by service personnel after system inspection.

15. A method for detecting resonance in a multiphase power conversion system, the method comprising:
receiving or analyzing at least one filter current signal or value representing at least one filter current flowing in a filter capacitor of the power conversion system; and
selectively identifying a suspected resonance condition in the power conversion system if a component of the at least one filter current signal in a predetermined frequency band exceeds a predetermined threshold; and
changing an operating state of the power conversion system or an external device in response to identification of the suspected resonance condition in the filter circuit.

16. The method of claim 15 , comprising:
filtering the at least one filter current signal or value using a bandpass filter;
computing at least one mean value based on the filtered current signal or value;
comparing the at least one mean value to the predetermined threshold; and
selectively identifying a suspected resonance condition in the power conversion system if the at least one mean value exceeds the predetermined threshold.

17. The method of claim 15 , comprising:
filtering the at least one filter current signal or value using a bandpass filter;
computing at least one RMS value based on the filtered current signal or value;
comparing the at least one RMS value to a predetermined threshold; and
selectively identifying a suspected resonance condition in the power conversion system if the at least one RMS value exceeds the predetermined threshold.

18. The method of claim 15 , comprising filtering the at least one filter current signal or value using a bandpass filter having an upper cutoff frequency of about 2,200 Hz or less and a lower cutoff frequency of about 500 Hz or more.

19. The method of claim 15 , comprising sampling the at least one filter current signal or value at a sample frequency of about 22 KHz or more.

20. A non-transitory computer readable medium with computer executable instructions for detecting resonance in a multiphase power conversion system, the computer readable medium comprising computer executable instructions for:
receiving or analyzing at least one fil

Assignees

• Patel Yogesh Popatlal
• Wei Lixiang
• Rockwell Automation Tech Inc

Inventors

• Patel Yogesh Popatlal
• Wei Lixiang

Classifications

• H02M5/4585

  having a rectifier with controlled elements · CPC title

• H02M1/126 Primary

  using passive filters · CPC title