Method and system for locating ground faults in a network of drives

Patent metadata

Field	Value
Publication number	US-10585134-B2
Application number	US-201515766132-A
Country	US
Kind code	B2
Filing date	Oct 5, 2015
Priority date	Oct 5, 2015
Publication date	Mar 10, 2020
Grant date	Mar 10, 2020

Abstract

A drive system includes a current sensor configured to generate a first current signal representative of a current flowing in one or more electrical devices electrically coupled together through a power supply bus, a power output bus, and a common ground. The drive system also includes a voltage sensor configured to generate a first voltage signal representative of a voltage with respect to the common ground in the one or more electrical devices. The drive system further includes a ground fault detection controller configured to determine a ground fault in the one or more electrical devices based on a change in at least one of the first current signal and the first voltage signal.

First claim

What is claimed is:

1. A drive system comprising:
a current sensor configured to generate a first current signal representative of a current flowing in one or more electrical devices electrically coupled together through a power supply bus, a power output bus, and a common ground;
a voltage sensor configured to generate a first voltage signal representative of an AC input voltage including a common-mode component in the one or more electrical devices;

wherein the common-mode component is extracted from the first voltage signal, the common-mode component representing a voltage drop across a common-mode choke due to ground fault currents when a ground fault is present; and
a controller configured to determine a first ground fault in the one or more electrical devices based on a change in at least one of the first current signal and the first voltage signal;
wherein, when the first ground fault is detected, the drive system selectively disconnects the one or more electrical devices displaying the first ground fault before a second ground fault occurs.

2. The drive system of claim 1 , wherein at least some of the one or more electrical devices includes:
an AC-DC converter including an AC input and a DC output;
a DC-AC inverter including a DC input and an AC output; and
a DC link electrically coupled between the AC-DC converter DC output and the DC-AC inverter DC input.

3. The drive system of claim 2 , wherein said voltage sensor is configured to generate a first voltage signal representative of the AC input voltage with respect to the DC link and the common ground in the one or more electrical devices.

4. The drive system of claim 1 , wherein said controller is configured to determine the ground fault in the one or more electrical devices based on a change in one or more current signals generated by a respective current sensor in the common ground in the one or more electrical devices.

5. The drive system of claim 1 , wherein said controller is configured to determine the ground fault in the one or more electrical devices based on a change of phase in at least one of the first current signal and the first voltage signal.

6. The drive system of claim 1 , wherein said controller is configured to generate a signal that initiates an electrical isolation of the one or more electrical devices having the ground fault.

7. A method of detecting a ground fault in one or more electrical devices in a network of a plurality of electrical devices, said method comprising:
receiving a first current signal representative of a current flowing in at least some of the plurality of electrical devices;
receiving a first voltage signal representative of a voltage with respect to a DC link midpoint voltage or to ground in the at least some of the plurality of electrical devices;
determining a first ground fault in one or more of the at least some of the plurality of electrical devices based on a change in at least one of the first current signal and the first voltage signal; and
selectively disconnecting the electrical devices displaying the first ground fault before a second ground fault occurs.

8. The method of claim 7 , wherein receiving the first current signal comprises receiving at least one of an input current signal representative of current flowing into the at least some of the plurality of electrical devices and an output current signal representative of current flowing out of the at least some of the plurality of electrical devices.

9. The method of claim 7 , wherein receiving the first voltage signal comprises receiving at least one of an input voltage signal representative of an AC voltage at the input of the at least some of the plurality of electrical devices and a mid-to-ground voltage signal representative of a DC voltage with respect to the DC link midpoint voltage or to ground of the at least some of the plurality of electrical devices.

10. The method of claim 9 , wherein the plurality of electrical devices include a plurality of electrical power converters, each of the electrical power converters of the plurality of electrical power converters including an AC-DC converter, a DC link, and a DC-AC inverter coupled in electrical series, and wherein receiving an input voltage signal representative of an AC voltage at the input of the at least some of the plurality of electrical devices comprises receiving an input voltage signal representative of an AC voltage at the input of a respective AC-DC converter.

11. The method of claim 9 , wherein the plurality of electrical devices include a plurality of electrical power converters, each of the electrical power converters of the plurality of electrical power converters including an AC-DC converter, a DC link, and a DC-AC inverter coupled in electrical series, and wherein receiving a mid-to-ground voltage signal comprises receiving a mid-to-ground voltage signal representative of a DC voltage of the DC link with respect to ground.

12. The method of claim 7 , wherein receiving the first current signal comprises receiving a first current signal representative of a current flowing in a connection of the one or more electrical devices to ground.

13. The method of claim 12 , wherein determining the ground fault comprises determining a ground fault in one or more of the at least some of the plurality of electrical devices based on a change in the current flowing in the connection to ground.

14. The method of claim 7 , wherein determining the ground fault in one or more of the at least some of the plurality of electrical devices based on a change in at least one of the first current signal and the first voltage signal comprises determining a ground fault in one or more of the at least some of the plurality of electrical devices based 5 on a change in the first voltage signal, wherein a magnitude of change in the first voltage signal is determined by at least one of a phase-to-neutral voltage value at the point of the ground fault, a resistance of the ground fault, and an impedance of the return path from the ground fault.

15. The method of claim 7 , wherein determining the ground fault in one or more of the at least some of the plurality of electrical devices based on a change in at least one of the first current signal and the first voltage signal comprises determining a ground fault in a particular one electrical device of the plurality of electrical devices based 5 on a relative change in at least one of the first current signal and the first voltage signal of the particular one electrical device of the plurality of electrical devices and at least one of a first current signal and a first voltage signal of another one electrical device of the plurality of electrical devices.

16. An electrical power converter system comprising:
a plurality of power converter devices electrically coupled to a single power supply bus, each power converter device of the plurality of power converter devices is non-solidly grounded, each said power converter device comprising:
an AC-DC converter comprising an AC input and a DC output;
a DC-AC inverter comprising a DC input and an AC output; and
a DC link electrically coupled between a DC output of said AC-DC converter and a DC input of said DC-AC inverter; and
a ground fault detection controller configured to determine a first ground fault in said one or more of the plurality of power converter devices based on a change in at least one of an AC input current signal, an AC output current signal, and a voltage signal of said DC link with respect to ground;
wherein, when the first ground fault is detected, the drive system selectivel

Assignees

• Gen Electric

Inventors

• Kell Max-Josef
• Schroeder Stefan
• Shen Jie
• Yuan Zhihui
• Chen Yunzheng
• Hashem Mohamed

Classifications

• H02H7/1216

  for AC-AC converters · CPC title

• G01R31/086 Primary

  in power transmission or distribution networks, i.e. with interconnected conductors · CPC title

• H02H3/36

  involving comparison of the voltage or current values at corresponding points of different systems, e.g. of parallel feeder systems · CPC title

• Y02E60/60

  Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD] · CPC title

• H02H3/105

  responsive to excess current and fault current to earth · CPC title