SWITCHING DEVICE FAILURE DETECTION SYSTEM AND METHOD FOR MULTILEVEL CONVERTERS

• US 20110140727A1
• Filed: 05/28/2010
• Published: 06/16/2011
• Est. Priority Date: 05/28/2010
• Status: Active Grant

• Current Assignee: GE Infrastructure Technology, LLC (GE Vernova, Inc.)
• Original Assignee: General Electric Company
• Inventors: Soldi, Paolo, Roesner, Robert, Schroeder, Stefan
• Granted Patent: US 8,471,584 B2
• Time in Patent Office: Days
• US Class Current: 324/762.01
• CPC Class Codes: G01R 31/42 AC power supplies
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/487 Neutral point clamped inverters
• CPC Class Codes: H03K 17/18 Modifications for indicating state of switch

Abstract

A multilevel converter includes a plurality of phase legs each having at least two inner switching devices, at least two outer switching devices, at least two clamping diodes, a split DC link and a switching device failure detection circuit. The switching device failure detection circuit includes a logic module for each of the switching devices, a voltage calculation module and a failure detection algorithm. The logic module generates a blocking state logic signal by comparing a switching device voltage and a threshold reference voltage and the voltage calculation module determines an expected voltage blocking state for each of the switching devices based on the gate drive signals of the switching devices and an output current direction. The failure detection algorithm detects a failure condition in any of the switching devices based on the blocking state logic signals and the expected voltage blocking states of the switching devices.

Claims

1. A multilevel converter comprising:

a plurality of phase legs each having at least two inner switching devices, at least two outer switching devices, at least two clamping diodes and a split DC link; and

a switching device failure detection circuit comprising

a logic module for each of the switching devices to generate a blocking state logic signal by comparing a switching device voltage and a threshold reference voltage;

a voltage calculation module to determine an expected voltage blocking state for each of the switching devices based on the gate drive signals of the switching devices and an output current direction;

a failure detection algorithm to detect a failure condition in any of the switching devices based on the blocking state logic signals and the expected voltage blocking states of the switching devices.

2. The multilevel converter of claim 1, wherein the threshold reference voltage is higher than a rated voltage drop across the switching device.

3. The multilevel converter of claim 1, wherein the threshold reference voltage is between a rated voltage drop across the switching device and half the DC link voltage.

4. The multilevel converter of claim 1, wherein the logic module comprises a de-saturation circuit comparator.

5. The multilevel converter of claim 1, wherein voltage calculation module determines an expected output voltage at the multilevel converter output terminals, and wherein one of the inner switching devices comprises a top inner switching device, another of the inner switching devices comprises a bottom inner switching device, one of the outer switching devices comprises a top outer switching device, and another of the outer switching devices comprises a bottom outer switching device.

6. The multilevel converter of claim 5, wherein the expected output voltage is a zero voltage when the gate drive signals for any one of the inner switching devices are high and the gate drive signals for both the outer switching devices are low.

7. The multilevel converter of claim 5, wherein the expected output voltage is a positive voltage when the gate drive signals for both top inner and outer switching devices are high or when the output current direction is negative and the gate drive signals for all the switching devices are low.

8. The multilevel converter of claim 5, wherein the expected output voltage is a negative voltage when the gate drive signals for both the bottom inner and outer switching devices are high or when the output current direction is positive and the gate drive signals for all the switching devices are low.

9. The multilevel converter of claim 5, wherein the failure detection algorithm detects the failure condition in the top outer switching device when the expected output voltage is not positive and the blocking state logic signal for the top outer switching device is low.

10. The multilevel converter of claim 5, wherein the failure detection algorithm detects the failure condition in the top inner switching device when the expected output voltage is negative and the blocking state logic signal for the top inner switching device is low.

11. The multilevel converter of claim 5, wherein the failure detection algorithm detects the failure condition in the bottom inner switching device when the expected output voltage is positive and the blocking state logic signal for the bottom inner switching device is low.

12. The multilevel converter of claim 5, wherein the failure detection algorithm detects the failure condition in the bottom outer switching device when the expected output voltage is not negative and the blocking state logic signal for the bottom outer switching device is low.

13. The multilevel converter of claim 5, wherein the failure detection algorithm detects the failure condition in the top outer switching device when the expected output voltage is positive and the blocking state logic signal for the top outer switching device is high.

14. The multilevel converter of claim 5, wherein the failure detection algorithm detects the failure condition in the top inner switching device when the expected output voltage is not negative and the blocking state logic signal for the top inner switching device is high.

15. The multilevel converter of claim 5, wherein the failure detection algorithm detects the failure condition in the bottom inner switching device when the expected output voltage is not positive and the blocking state logic signal for the bottom inner switching device is high.

16. The multilevel converter of claim 5, wherein the failure detection algorithm detects the failure condition in the bottom outer switching device when the expected output voltage is negative and the blocking state logic signal for the bottom outer switching device is high.

17. A multilevel converter comprising:

a plurality of phase legs each having at least two inner switching devices, at least two outer switching devices, at least two clamping diodes and a split DC link; and

a switching device failure detection circuit comprising

a voltage calculation module to determine an expected output voltage at phase terminals of phase legs based on gate drive signals of switching devices and an output current direction;

a failure detection algorithm to detect a failure condition in any of the switching devices by comparing the expected output voltage with an actual output voltage.

18. A method of determining a failure condition in switching devices of a multilevel converter comprising a split DC link and a plurality of phase legs each having at least two inner switching devices, at least two outer switching devices, at least two clamping diodes, the method comprising:

determining an expected voltage blocking state for each of the switching devices based on gate drive signals of the switching devices and an output current direction;

generating blocking state logic signals by comparing terminal voltages across the switching devices and a threshold reference voltage; and

detecting failure conditions in the switching devices based on the blocking state logic signals and the voltage blocking states for the switching devices.

19. (canceled)