US-12618918-B2 - Ground fault detection system and method

Abstract

A ground fault detection system for a power system having a DC link, a battery bank, a link capacitor unit connected to the DC link, and plural power converters connected to the DC link. The power converters convert first DC power from the DC link to at least one of AC power or second DC power for powering at least one electrical load. A control unit disconnects the battery bank from the DC link responsive to detection of a ground fault, to deactivate operation of the power converters, and to sequentially at least partially activate, with power from the link capacitor unit, each of the power converters individually until a sensed voltage signal of the DC link is indicative of the ground fault being associated with one of the power converters.

Inventors

• Sai Kumar Vudugula
• Rajendra Prasad Chittimalla
• Ajith Kuttannair Kumar

Assignees

• TRANSPORTATION IP HOLDINGS, LLC

Dates

Publication Date

20260505

Application Date

20231219

Claims (17)

1. 1 . A system comprising: a power system having a DC link, a battery bank selectively connectable to the DC link, a link capacitor unit connected to the DC link, and power converters connected to the DC link, the power converters configured to convert first DC power from the DC link to at least one of AC power or second DC power for powering at least one electrical load; and a control unit operably connected to the power system, wherein the control unit is configured to: responsive to detection of a ground fault, to disconnect the battery bank from the DC link, to deactivate operation of the power converters, and to sequentially at least partially activate, with power from the link capacitor unit, each of the power converters individually until a sensed voltage signal of the DC link is indicative of the ground fault being associated with a first power converter of the power converters, wherein the sensed voltage signal comprises a first DC voltage component of the DC link after sequential individual activation of the first power converter; determine that the sensed voltage signal is indicative of the ground fault being associated with the first power converter responsive to the first DC voltage component being greater than a first designated threshold; and responsive to the detection of the ground fault, compare a second DC voltage component of the DC link to a second threshold, and identify the ground fault as a DC ground fault responsive to the second DC voltage component being greater than the second threshold.
2. 2 . The system of claim 1 , wherein the first DC voltage component is between a terminal of the DC link and a vehicle chassis or other electrical ground.
3. 3 . The system of claim 1 , wherein the control unit is configured to determine that the sensed voltage signal is indicative of the ground fault being associated with the first power converter responsive to the first DC voltage component being greater than the first designated threshold at the end of a first designated time period from when the first power converter is individually sequentially at least partially activated.
4. 4 . The system of claim 1 , wherein the control unit is further configured, responsive to the sensed voltage signal being indicative of the ground fault associated with the first power converter, to control continued deactivation of the first power converter for operation of the power system to power the at least one electrical load without using the first power converter.
5. 5 . The system of claim 1 , wherein the control unit is configured to sequentially at least partially activate all the power converters individually within a time period of when power is available from the link capacitor unit without electrical connection to the battery bank.
6. 6 . The system of claim 5 , wherein the control unit is configured to sequentially at least partially activate all the power converters individually before a voltage level on the DC link falls below a designated voltage level that is greater than zero volts.
7. 7 . The system of claim 1 , when for each power converter of the power converters that is sequentially at least partially activated, the control unit is configured to activate a single semiconductor device or other electrically-controllable switch of the power converters to electrically connect a terminal of one of the at least one electrical load to the DC link.
8. 8 . The system of claim 1 , wherein the control unit is further configured, responsive to the detection of the ground fault, to compare an AC component of the DC link to a third threshold, and to identify the ground fault as an AC ground fault responsive to the AC component being greater than the third threshold.
9. 9 . The system of claim 8 , wherein the control unit is further configured, responsive to identifying the DC ground fault and after disconnection of the battery bank from the DC link, to conduct a comparison of a third DC voltage component of the DC link that is present on the DC link at the end of a designated non-zero time period after the battery bank is disconnected from the DC link to a fourth threshold, and to identify the DC ground fault as being associated with one of the battery bank or the DC link based on the comparison.
10. 10 . The system of claim 8 , wherein the control unit is further configured, responsive to identifying the DC ground fault and after disconnection of the battery bank and disconnection of a dynamic braking resistor grid from the DC link, to conduct a comparison of a third DC voltage component of the DC link that is present on the DC link at the end of a designated non-zero time period after the battery bank is disconnected from the DC link to a fourth threshold, and to identify the DC ground fault as being associated with the DC link responsive to the third DC voltage component being greater than the fourth threshold and to identify the DC ground fault as being associated with one of the battery bank or the dynamic braking resistor grid responsive to the third DC voltage component being less than the fourth threshold.
11. 11 . The system of claim 10 , wherein the control unit is further configured, responsive to the DC ground fault being associated with one of the battery bank or the dynamic braking resistor grid, to control electrical connection of the dynamic braking resistor grid to the DC link and to identify the DC ground fault as being associated with the dynamic braking resistor grid responsive to a fourth DC voltage component of the DC link being greater than a fifth threshold.
12. 12 . The system of claim 1 , wherein the control unit is further configured to determine an AC ground fault based on a comparison of a first AC component of the sensed voltage signal to a first designated AC threshold.
13. 13 . The system of claim 12 , wherein the control unit is further configured, responsive to determination of the AC ground fault or the DC ground fault, to disconnect the battery bank from the DC link and deactivate operation of the power converters, and, responsive to the determination of the AC ground fault, to sequentially at least partially activate, with power from the link capacitor unit, each of the power converters individually until a second DC component of the sensed voltage signal is indicative of the AC ground fault being associated with the first power converter of the power converters.
14. 14 . A system comprising: a power system having a DC link, a battery bank selectively connectable to the DC link, a link capacitor unit connected to the DC link, and power converters connected to the DC link, the power converters configured to convert first DC power from the DC link to at least one of AC power or second DC power for powering at least one electrical load; and a control unit operably connected to the power system, wherein the control unit is configured to: determine a ground fault based on a comparison of a first DC component of a sensed voltage signal between a terminal of the DC link and a chassis or other electrical ground to a first designated DC threshold, and responsive to detection of the ground fault, compare a second DC voltage component of the DC link to a second threshold, and identify the ground fault as a DC ground fault responsive to the second DC voltage component being greater than the second threshold; determine an AC ground fault based on a comparison of a first AC component of the sensed voltage signal to a first designated AC threshold; responsive to determination of the AC ground fault or the DC ground fault, to disconnect the battery bank from the DC link and deactivate operation of the power converters; and responsive to the determination of the AC ground fault, to sequentially at least partially activate, with power from the link capacitor unit, each of the power converters individually until a second DC component of the sensed voltage signal is indicative of the AC ground fault being associated with a first power converter of the power converters.
15. 15 . A method comprising: disconnecting, by a control unit operably connected to a power system, a battery bank of the power system from a DC link of the power system responsive to detection of a ground fault by the control unit; deactivating operation of power converters that convert power from the DC link for operation of at least one load of the power system; sequentially at least partially activating, by the control unit, with power from a link capacitor unit of the power system, each of the power converters individually until a sensed voltage signal of the DC link is indicative of the ground fault being associated with a first power converter of the power converters, wherein the sensed voltage signal comprises a first DC voltage component of the DC link after sequential individual activation of the first power converter, and the control unit is configured to determine that the sensed voltage signal is indicative of the ground fault being associated with the first power converter responsive to the first DC voltage component being greater than a first designated threshold; responsive to the detection of the ground fault, comparing, by the control unit, a second DC voltage component of the DC link to a second threshold; and identifying, by the control unit, the ground fault as a DC ground fault responsive to the second DC voltage component being greater than the second threshold.
16. 16 . A method comprising: determining, by a control unit operably connected to a power system, a DC ground fault based on a comparison of a first DC component of a sensed voltage signal between a terminal of a DC link and a chassis or other electrical ground to a first designated DC threshold; determining, by the control unit, an AC ground fault based on a comparison of a first AC component of the sensed voltage signal to a first designated AC threshold; responsive to determination of the AC ground fault or the DC ground fault, disconnecting, by the control unit, a battery bank from the DC link and deactivating operation of power converters of the power system that covert power from the DC link for operating at least one load of the power system; and responsive to the determination of the AC ground fault, sequentially at least partially activating, by the control unit, with power from a link capacitor unit of the power system, each of the power converters individually until a second DC voltage component of the sensed voltage signal is indicative of the AC ground fault being associated with a first power converter of the power converters, wherein the second DC voltage component of the DC link is compared to a second threshold, and identified the AC ground fault responsive to the second DC voltage component being greater than the second threshold.
17. 17 . The method of claim 16 , wherein the power system comprises a vehicle and the at least one load comprises a traction motor.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63/450,484 (filed 7 Mar. 2023), the entire disclosure of which is incorporated herein by reference. BACKGROUND Technical Field Embodiments of the present disclosure relate to power systems that provide electrical power to operate a load. Other embodiments relate to detection of ground faults in a power system. Discussion of Art Certain power systems are configured to convert one form of electrical energy to a second form of electrical energy that is suitable for electrically powering an electrical load. For example, a stationary power unit may include a fuel engine that combusts a fuel to mechanically drive an electrical generator, and a power conversion circuit that converts electrical power produced by the generator into a different form of electrical power (e.g., DC to AC) to power a load connected to the stationary power unit. In another example, a vehicle may include a battery system that outputs DC power, and a power conversion circuit that converts the DC power to AC power for operating an AC traction motor of the vehicle. All such systems may be subject to ground faults, which are unintentional electrical pathways between a power source and a grounded surface, caused by damaged cables or connections, water contamination, etc. Ground faults may result in damage or even failure of all or part of a power system, and thus require detection and remediation when a power system is in operation (e.g., shutting down the power system when a ground fault is detected). For systems with complex electrical circuits, suitable ground detection functionality may be expensive to implement, and it may be difficult to accurately detect, isolate, and remediate ground faults. It may be desirable to have a ground fault detection system and method that differ from those that are currently available. BRIEF DESCRIPTION In an embodiment, a system (e.g., a ground fault detection system) for a power system includes a control unit configured for operable connection to the power system. The power system includes a DC link, a battery bank selectively connectable to the DC link, a link capacitor unit (e.g., one or more capacitors) connected to the DC link, and plural power converters connected to the DC link. The power converters are configured to convert first DC power from the DC link to at least one of AC power or second DC power for powering at least one electrical load. The control unit is configured, responsive to detection of a ground fault, to disconnect the battery bank from the DC link, to deactivate operation of the power converters, and to sequentially at least partially activate, with power from the link capacitor unit, each of the power converters individually until a sensed voltage signal of the DC link is indicative of the ground fault being associated with one of the power converters. In an embodiment, a system (e.g., a ground fault detection system) for a power system includes a control unit configured for operable connection to the power system. The power system includes a DC link, a battery bank selectively connectable to the DC link, a link capacitor unit (e.g., one or more capacitors) connected to the DC link, and plural power converters connected to the DC link. The power converters are configured to convert first DC power from the DC link to at least one of AC power or second DC power for powering at least one electrical load. The control unit is configured to determine a DC ground fault based on a comparison of a first DC component of a sensed voltage signal between a terminal of the DC link and a chassis or other electrical ground to a first designated DC threshold. The control unit is further configured to determine an AC ground fault based on a comparison of a first AC component of the sensed voltage signal to a first designated AC threshold. The control unit is further configured, responsive to determination of the AC ground fault or the DC ground fault, to disconnect the battery bank from the DC link and deactivate operation of the power converters, and, responsive to the determination of the AC ground fault, to sequentially at least partially activate, with power from the link capacitor unit, each of the power converters individually until a second DC component of the sensed voltage signal is indicative of the AC ground fault being associated with a first power converter of the plural power converters. BRIEF DESCRIPTION OF THE DRAWINGS The subject matter may be understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below: FIG. 1 is an electrical schematic diagram of a ground fault detection system operably connected to a power system, according to an embodiment. DETAILED DESCRIPTION Examples of the subject matter described herein relate to systems and methods for detecting ground faults in a power system, isolating the gro