Robust AC chassis fault detection using PWM sideband harmonics

• US 8,278,934 B2
• Filed: 02/13/2009
• Issued: 10/02/2012
• Est. Priority Date: 02/13/2009
• Status: Active Grant

• Current Assignee: BAE Systems Controls Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Controls Incorporated (BAE Systems Plc)
• Inventors: Wang, Michael Kon-King
• Primary Examiner(s): Velez, Roberto
• Application Number:
  US12/371,241
• Publication Number:
  US 20100207634A1
• Time in Patent Office: 1,327 Days
• Field of Search: 324/503, 324/509, 324/510, 324/511
• US Class Current: 324/509
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00
• CPC Class Codes: G01R 31/42 AC power supplies
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults
• CPC Class Codes: H02P 29/0241 the fault being an overvoltage

Abstract

A method, apparatus and computer program for detecting an AC chassis fault on one or more DC/AC converters having a load is disclosed, including receiving a chassis voltage V_Chassis signal from between DC link and a chassis ground from the DC/AC converter, capturing a side band harmonic of the chassis voltage V_Chassis signal, determining a peak magnitude value related to the side band harmonic, comparing the peak magnitude value to a predetermined threshold value, wherein if said peak magnitude value equals or exceeds the predetermined threshold value, an AC chassis fault condition is detected.

Claims

1. A method of detecting an AC chassis fault on one or more DC/AC converters having a load, comprising:

receiving a chassis voltage V_Chassis signal from between a DC link voltage and a chassis ground;

capturing at least one side band harmonic of said chassis voltage V_Chassis signal;

determining a peak magnitude value related to said side band harmonic (SBH);

comparing said peak magnitude value to a predetermined threshold value, wherein if said peak magnitude value equals or exceeds said predetermined threshold value an AC chassis fault condition is detected on said one or more DC/AC converters having the load.

2. The method of claim 1, wherein the peak magnitude value is the maximum energy generated by the SBH minus the maximum energy generated by each said one or more DC/AC converters on a load operating under normal operating conditions without a fault over a predetermined amount of time.

3. The method of claim 1, further including coupling a filter to said DC link and the chassis ground that are shared among said one or more DC/AC converters.

4. The method of claim 1, wherein the step of determining a peak magnitude value, the further step of:

calculating a fault condition value based upon a theoretical side band per unit value, a measured DC voltage V_dc of each said one or more DC/AC converters, a safety factor value and measured change in time Δ

t.

5. The method of claim 4, further including the step of applying said calculated fault condition value to an anti-windup limiter, wherein the anti-windup limiter is set to zero.

6. The method of claim 1, wherein said peak magnitude value and a list of predetermined threshold values are stored.

7. The method of claim 1, wherein said determining step further comprises:

a frequency domain approach to compute a value of a sum of a harmonic voltage squared minus a threshold voltage squared multiplied by a change in time Σ

(V_Harmonic²−

V_Threshold²)*Δ

t, wherein Δ

t is the loop scan time of detection.

8. The method of claim 1, wherein the comparing step determines which among each said DC/AC converter has an AC chassis fault condition.

9. An AC chassis fault detector for detecting an AC chassis fault on one or more DC/AC converters having a load, comprising:

means for receiving a chassis voltage V_Chassis signal from between a DC link voltage and a chassis ground;

means for capturing at least one side band harmonic of said chassis voltage V_Chassis signal;

means for determining a peak magnitude value related to said side band harmonic (SBH);

means for comparing said peak magnitude value to a predetermined threshold value, wherein if said peak magnitude value equals or exceeds said predetermined threshold value an AC chassis fault condition is detected on said one or more DC/AC converters having the load.

10. The apparatus of claim 9, wherein the peak magnitude value is the maximum energy generated by the SBH minus the maximum energy generated by each said one or more DC/AC converters on a load operating under normal operating conditions without a fault over a predetermined amount of time.

11. The apparatus of claim 9, wherein a band-pass filter captures a first side band harmonic of said chassis voltage V_Chassis signal.

12. The apparatus of claim 9, wherein said determining means further comprises:

means for calculating by a frequency domain approach a computed value of a sum of a harmonic voltage squared minus a threshold voltage squared multiplied by a change in time Σ

(V_Harmonic²−

V_Threshold²)*Δ

t, wherein Δ

t is the loop scan time of detection.

13. The apparatus of claim 12, further comprising an anti-windup limiter disposed between said means for calculating and said means for comparing, and the anti-windup limiter is set to zero.

14. The apparatus of claim 9, wherein said means for comparing can determine which among each said DC/AC converter has an AC chassis fault condition.

15. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform a method of detecting an AC chassis fault on one or more DC/AC converter having a load, comprising the steps of:

receiving a chassis voltage V_Chassis signal from between a DC link voltage and a chassis ground;

capturing at least one side band harmonic of said chassis voltage V_Chassis signal;

determining a peak magnitude value related to said side band harmonic (SBH);

comparing said peak magnitude value to a predetermined threshold value, wherein if said peak magnitude value equals or exceeds said predetermined threshold value an AC chassis fault condition is detected on said one or more DC/AC converters having the load.