Method and apparatus for monitoring isolation of an electric power bus

Patent metadata

Field	Value
Publication number	US-11275107-B2
Application number	US-201916709501-A
Country	US
Kind code	B2
Filing date	Dec 10, 2019
Priority date	Dec 10, 2019
Publication date	Mar 15, 2022
Grant date	Mar 15, 2022

Abstract

Dynamically monitoring of an electrically-isolated power bus for a DC power system is described, and includes dynamically monitoring voltage and current on the power bus to determine a variation in the voltage on the power bus. When the variation in the voltage on the power bus is less than a threshold, an active positive isolation resistance term and an active negative isolation resistance term are determined. A first voltage balance term is determined based upon a ratio of the active positive isolation resistance term and the active negative isolation resistance term. A dynamic positive isolation resistance term and a dynamic negative isolation resistance term are determined based upon the active negative isolation resistance term. A fault associated with the power bus is determined based upon the dynamic positive isolation resistance term and the dynamic negative isolation resistance term.

First claim

What is claimed is:

1. A method for dynamically monitoring an electrically-isolated power bus for a DC power system, wherein the power bus includes a positive power bus and a negative power bus, the method comprising:
dynamically monitoring voltage of the power bus;
determining a variation in the voltage on the power bus;
when the variation in the voltage on the power bus is less than a threshold variation:
determining an active positive isolation resistance term associated with the positive power bus and ground,
determining an active negative isolation resistance term associated with the negative power bus and ground, and
determining a first voltage balance term based upon a ratio of the active positive isolation resistance term and the active negative isolation resistance term; and

periodically determining a dynamic isolation resistance term, including:
dynamically monitoring the voltage of the power bus;
dynamically determining a voltage between the positive power bus and ground,
dynamically determining a voltage between the negative power bus and ground, and
determining a dynamic voltage balance term based upon a ratio of the voltage between the positive power bus and ground and the voltage between the negative power bus and ground;
determining, via the controller, a dynamic positive isolation resistance term based upon the active positive isolation resistance term and the dynamic voltage balance term;
determining, via the controller, a dynamic negative isolation resistance term based upon the active negative isolation resistance term and the dynamic voltage balance term; and
detecting a fault associated with the power bus based upon the dynamic positive isolation resistance term and the dynamic negative isolation resistance term.

2. The method of claim 1 , further comprising:
introducing a first bias resistance element between the positive power bus and ground;
determining a first voltage between the positive power bus and ground;
determining the active positive isolation resistance term based upon the first bias resistance element and the first voltage between the positive power bus and ground; and
determining the active negative isolation resistance term based upon the resistance and the first voltage between the positive power bus and ground.

3. The method of claim 1 , further comprising:
introducing a second bias resistance element between the negative power bus and ground;
determining a second voltage between the positive power bus and ground;
determining the active positive isolation resistance term based upon the second bias resistance element and the second voltage between the negative power bus and ground; and
determining the active negative isolation resistance term based upon the second bias resistance element and the second voltage between the negative power bus and ground.

4. The method of claim 1 , wherein determining the dynamic positive isolation resistance term based upon the active positive isolation resistance term and the dynamic voltage balance term comprises determining the dynamic positive isolation resistance term to be equal to the active positive isolation resistance term when the dynamic voltage balance term is equivalent to the first voltage balance term.

5. The method of claim 1 , wherein determining the dynamic negative isolation resistance term based upon the active negative isolation resistance term and the dynamic voltage balance term comprises determining the dynamic negative isolation resistance term to be equal to the active negative isolation resistance term when the dynamic voltage balance term is equivalent to the first voltage balance term.

6. The method of claim 1 , wherein determining the dynamic positive isolation resistance term based upon the active positive isolation resistance term and the dynamic voltage balance term comprises determining the dynamic positive isolation resistance term to be equal to the active positive isolation resistance term multiplied by the dynamic voltage balance term when the dynamic voltage balance term is less than the first voltage balance term.

7. The method of claim 1 , wherein determining the dynamic negative isolation resistance term based upon the active negative isolation resistance term and the dynamic voltage balance term comprises determining the dynamic negative isolation resistance term to be equal to the active negative isolation resistance term when the dynamic voltage balance term is less than the first voltage balance term.

8. The method of claim 1 , wherein determining the dynamic positive isolation resistance term based upon the active positive isolation resistance term and the dynamic voltage balance term comprises determining the dynamic positive isolation resistance term to be equal to the active positive isolation resistance term when the dynamic voltage balance term is greater than the first voltage balance term.

9. The method of claim 1 , wherein determining the dynamic negative isolation resistance term based upon the active negative isolation resistance term and the dynamic voltage balance term comprises determining the dynamic negative isolation resistance term to be equal to the active negative isolation resistance term divided by the dynamic voltage balance term when the dynamic voltage balance term is greater than the first voltage balance term.

10. The method of claim 1 , wherein determining the dynamic positive isolation resistance term based upon the active positive isolation resistance term and the dynamic voltage balance term further comprises determining the dynamic positive isolation resistance term to be equal to the active positive isolation resistance term multiplied by a ratio of the first voltage balance term and the dynamic voltage balance term when the dynamic voltage balance term is less than the first voltage balance term.

11. The method of claim 1 , wherein determining the dynamic negative isolation resistance term based upon the active negative isolation resistance term and the dynamic voltage balance term further comprises determining the dynamic negative isolation resistance term to be equal to the active negative isolation resistance term divided by a ratio of the first voltage balance term and the dynamic voltage balance term when the dynamic voltage balance term is greater than the first voltage balance term.

12. The method of claim 1 , further comprising communicating occurrence of the fault associated with the power bus to an operator via the controller.

13. The method of claim 1 , wherein detecting the fault associated with the power bus based upon the dynamic positive isolation resistance term and the dynamic negative isolation resistance term comprises:
detecting the fault associated with the power bus when one of the dynamic positive isolation resistance term or the dynamic negative isolation resistance term is less than a minimum threshold resistance.

14. A DC power system, comprising:
a DC power source electrically coupled to an electric load via an electrically-isolated power bus, wherein the electrically-isolated power bus include a positive power bus and a negative power bus, wherein the positive power bus and the negative power bus are electrically isolated from a chassis ground;
a controller, in communication with the DC power source, the electrically-isolated power bus, and the electric load;
the controller including an instruction set, the instruction set executable to:
monitor voltage of the power bus;
determine a variation in the voltage on the power bus;
when the variation in the voltage on the power bus is less than a threshold variation:
introduce a first

Assignees

• Gm Global Tech Operations Llc

Inventors

• Sevel Kris
• Fan Yue
• Francu Emil
• Wang Konking

Classifications

• G01R19/00 Primary

  Arrangements for measuring currents or voltages or for indicating presence or sign thereof (G01R5/00 takes precedence; for measuring bioelectric currents or voltages A61B5/24) · CPC title

• G01R27/025

  Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters · CPC title

• G01R31/007

  using microprocessors or computers · CPC title

• G01R31/006

  on road vehicles, e.g. automobiles or trucks (testing of ignition installations peculiar to internal combustion engines F02P17/00) · CPC title

• G01R31/00

  Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere ({measuring superconductive properties G01R33/1238;} testing line transmission systems H04B3/46; testing or measuring semiconductors or solid state devices during manufacture {H10P74/00}) · CPC title