SYSTEM AND METHOD OF PARALLELING ENGINE-GENERATORS ON A COMMON BUS

• US 20130049479A1
• Filed: 08/30/2011
• Published: 02/28/2013
• Est. Priority Date: 08/30/2011
• Status: Active Grant

• Current Assignee: Caterpillar Switchgear Americas LLC (Caterpillar Incorporated)
• Original Assignee: Timothy Hedquist
• Inventors: HEDQUIST, TIMOTHY
• Granted Patent: US 8,866,344 B2
• Time in Patent Office: Days
• US Class Current: 307/84
• CPC Class Codes: H02J 3/46 Controlling of the sharing of output between the generators, converters, or transformers

Abstract

A system parallels engine-generators on a common bus and includes circuit breakers and automatic voltage regulators. Each engine-generator includes an output having an alternating current voltage. Each breaker is between the output of a corresponding engine-generator and the bus. Each regulator includes a first mode controlling field excitation for a corresponding engine-generator and a second mode automatically controlling the AC voltage. A processor for the regulators starts the engine-generators, closes the breakers, causes the regulators to increase the field excitation for the corresponding engine-generator in the first mode as long as less than a predetermined current flows through a corresponding breaker until the field excitation is equal to a rated voltage, and responsively causes the regulators to automatically control the AC voltage of the output of the corresponding engine-generator in the second mode, and, otherwise, decreases the field excitation of the corresponding engine-generator in the first mode.

Claims

1. A system of paralleling engine-generators on a common bus, said system comprising:

a plurality of engine-generators, each of said engine-generators including an output having an alternating current voltage;

a plurality of circuit breakers, each of said circuit breakers being between the output of a corresponding one of said engine-generators and said common bus;

a plurality of automatic voltage regulators, each of said automatic voltage regulators comprising a first mode in which field excitation for a corresponding one of said engine-generators is controllable and a second mode in which the alternating current voltage of the output of said engine-generators is automatically controlled; and

a processor for said plurality of automatic voltage regulators, said processor being structured to start the engine-generators, close said circuit breakers, cause a plurality of said automatic voltage regulators to increase the field excitation for the corresponding one of said engine-generators in the first mode as long as less than a predetermined current flows through a corresponding one of said circuit breakers until the field excitation is equal to a rated voltage, and responsively cause a plurality of said automatic voltage regulators to automatically control the alternating current voltage of the output of the corresponding one of said engine-generators in the second mode, and, otherwise, to decrease the field excitation of the corresponding one of said engine-generators in the first mode.

2. The system of claim 1 wherein said processor is further structured to initially cause each of said automatic voltage regulators to be in the first mode.

3. The system of claim 1 wherein said processor is further structured to cause said engine-generators to be paralleled on said common bus with the field excitation being equal to the rated voltage and less than the predetermined current flowing through said circuit breakers within ten seconds of starting said engine-generators.

4. The system of claim 1 wherein said common bus is structured to be connected to a circuit breaker for a load powered by said common bus.

5. The system of claim 1 wherein the predetermined current is 600 A;

and wherein said engine-generators have a maximum output current of 1500 A.

6. The system of claim 1 wherein said processor is further structured to close the corresponding one of said circuit breakers responsive to disengagement of a starter motor for the corresponding one of said engine-generators.

7. The system of claim 1 wherein said processor comprises for each of said engine-generators a current sensor structured to sense current flowing through the corresponding one of said circuit breakers and a voltage sensor structured to sense the alternating current voltage of the output of the corresponding one of said engine-generators.

8. The system of claim 1 wherein the predetermined current is about 40% of a maximum output current of said engine-generators.

9. The system of claim 1 wherein said processor is further structured to cause synchronism of said engine-generators when the field excitation is equal to the rated voltage and less than the predetermined current flows through said circuit breakers.

10. The system of claim 1 wherein said first mode is structured to control the field excitation of the corresponding one of said engine-generators through a voltage bias signal ranging from 0% to 100% of rated field excitation.

11. A method of paralleling engine-generators on a common bus, said method comprising:

employing a plurality of engine-generators, each of said engine-generators including an output having an alternating current voltage;

employing a plurality of circuit breakers, each of said circuit breakers being between the output of a corresponding one of said engine-generators and said common bus;

employing a plurality of automatic voltage regulators, each of said automatic voltage regulators comprising a first mode in which field excitation for a corresponding one of said engine-generators is controllable and a second mode in which the alternating current voltage of the output of said engine-generators is automatically controlled;

starting the engine-generators;

closing said circuit breakers; and

causing a plurality of said automatic voltage regulators to increase the field excitation for the corresponding one of said engine-generators in the first mode as long as less than a predetermined current flows through a corresponding one of said circuit breakers until the field excitation is equal to a rated voltage, and responsively causing a plurality of said automatic voltage regulators to automatically control the alternating current voltage of the output of the corresponding one of said engine-generators in the second mode, and, otherwise, decreasing the field excitation of the corresponding one of said engine-generators in the first mode.

12. The method of claim 11 further comprising:

initially causing each of said automatic voltage regulators to be in the first mode.

13. The method of claim 11 further comprising:

causing said engine-generators to be paralleled on said common bus with the field excitation being equal to the rated voltage and less than the predetermined current flowing through said circuit breakers within ten seconds of starting said engine-generators.

14. The method of claim 11 further comprising:

connecting said common bus to a circuit breaker for a load powered by said common bus.

15. The method of claim 11 further comprising:

employing the predetermined current of 600 A; and

employing a maximum output current of 1500 A of said engine-generators.

16. The method of claim 11 further comprising:

closing the corresponding one of said circuit breakers responsive to disengagement of a starter motor for the corresponding one of said engine-generators.

17. The method of claim 11 further comprising:

employing for each of said engine-generators a current sensor structured to sense current flowing through the corresponding one of said circuit breakers and a voltage sensor structured to sense the alternating current voltage of the output of the corresponding one of said engine-generators.

18. The method of claim 11 further comprising:

employing the predetermined current of about 40% of a maximum output current of said engine-generators.

19. The method of claim 11 further comprising:

causing synchronism of said engine-generators when the field excitation is equal to the rated voltage and less than the predetermined current flows through said circuit breakers.

20. The method of claim 11 further comprising:

controlling the field excitation of the corresponding one of said engine-generators through a voltage bias signal ranging from 0% to 100% of rated field excitation.