System and method for paralleling electrical power generators

• US 8,766,479 B2
• Filed: 09/01/2010
• Issued: 07/01/2014
• Est. Priority Date: 09/01/2010
• Status: Active Grant

• Current Assignee: Kohler Company
• Original Assignee: Kohler Company
• Inventors: Dorn, Douglas W., Frampton, Isaac S.
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): DHILLON, JAGDEEP S
• Application Number:
  US12/873,608
• Publication Number:
  US 20120049638A1
• Time in Patent Office: 1,399 Days
• Field of Search: 307/70, 307/84, 307/85, 307/80, 307/64, 307/76, 307/87, 307/81, 307/19, 307/153, 307/66, 290/31
• US Class Current: 307/82
• CPC Class Codes: H02J 3/42 with automatic parallel connection when synchronisation is achieved

Abstract

A plurality of generators can be connected in parallel to a common electrical bus. Each generator has a controller that regulates the voltage and frequency of the electricity being produced. Before a given generator connects to the electrical bus, its controller senses whether electricity is present on the bus and if not, the connection is made. Otherwise, the controller synchronizes the electricity being produced to the electricity is present on the bus before the connection occurs. The controller in each generator may also implement a load sharing function which ensures that the plurality of generators equitably share in providing the total amount of power demanded by the loads. The load sharing can be accomplished by controlling the generators to operate a substantially identical percentages of their individual maximum power generation capacity.

Claims

1. A generator arrangement for supplying electricity to a parallel electrical bus to which at least one other energy source is able to supply electricity, said generator arrangement comprising:

an alternator that produces alternating electricity;

a circuit breaker selectively connecting and disconnecting the alternator to and from the parallel electrical bus;

an output sensor for sensing at least one of voltage and current of the alternating electricity;

a bus sensor for sensing at least one of voltage and current of electricity in the parallel electrical bus;

a genset controller connected to the output sensor, the bus sensor and the circuit breaker, and operatively connected to control excitation and speed of the alternator;

prior to applying the alternating electricity to the parallel electrical bus, the genset controller;

a) determines whether electricity is present on the parallel electrical bus,

b) if electricity is not present on the parallel electrical bus, the genset controller operates the circuit breaker to apply the alternating electricity produced by the alternator to the parallel electrical bus,

c) if electricity is present on the parallel electrical bus, then the genset controller;

1) varies operation of the alternator to synchronize the alternating electricity produced by the alternator to the electricity present on the parallel electrical bus, and thereafter

2) operates the circuit breaker to apply the alternating electricity produced by the alternator to the parallel electrical bus; and

a communication interface for exchanging messages with all other energy sources;

wherein the genset controller sends a message via the communication interface to inform other energy sources that the alternating electricity produced by the alternator is about to be applied to the parallel electrical bus; and

wherein the alternating electricity produced by the alternator is applied to the parallel electrical bus only if the genset controller receives a response message from at least one other energy source.

2. The generator arrangement as recited in claim 1 further comprising an internal combustion engine driving the alternator;

wherein the genset controller varies operation of the alternator by altering speed of the internal combustion engine.

3. The generator arrangement as recited in claim 1, wherein the genset controller varies operation of the alternator by altering speed of the alternator.

4. The generator arrangement as recited in claim 1, wherein the alternator comprises a field winding that produces a magnetic field;

wherein the genset controller varying operation of the alternator comprises altering the magnetic field.

5. The generator arrangement as recited in claim 1, wherein the genset controller further implements a load sharing function by:

determining a given operating level of the alternator;

detecting an operating level of each of the other energy sources; and

adjusting operation of the alternator so that the given operating level is substantially identical to the operating levels of the other energy sources.

6. The generator arrangement as recited in claim 1, wherein the genset controller further implements a load sharing function by:

determining a given percentage of a maximum power capacity at which the alternator is operating;

detecting a percentage of a respective maximum power capacity at which each other energy source is operating, thereby producing a percentage set;

calculating an average percentage from the given percentage and the percentage set; and

adjusting operation of the alternator so that the given percentage substantially equals the average percentage.

7. The generator arrangement as recited in claim 6 wherein implementation of the load sharing function by the genset controller further comprises sending an indication of the given percentage to other energy sources.

8. A system for supplying electricity to a parallel electrical bus, said system comprising:

a first generator arrangement having a first alternator that produces alternating electricity at an output, a first circuit breaker selectively connecting and disconnecting the output of the first alternator to and from the parallel electrical bus, a first output sensor for sensing a characteristic of the alternating electricity produced by the first alternator, a first bus sensor for sensing the characteristic of electricity in the parallel electrical bus, and a first genset controller connected to the first output sensor, the first bus sensor and the first circuit breaker, and operatively connected to control excitation and speed of the first alternator; and

a second generator arrangement having a second alternator that produces alternating electricity at an output, a second circuit breaker selectively connecting and disconnecting the output of the second alternator to and from the parallel electrical bus, a second output sensor for sensing a parameter of the alternating electricity produced by the second alternator, a second bus sensor for sensing the parameter of electricity in the parallel electrical bus, and a second genset controller connected to the second output sensor, the second bus sensor and the second circuit breaker, and operatively connected to control excitation and speed of the second alternator;

wherein each of the first and second genset controller;

a) determines whether electricity is present on the parallel electrical bus;

b) if electricity is not present on the parallel electrical bus, operates a respective one of the first and second circuit breaker to apply the alternating electricity to the parallel electrical bus;

c) if electricity is present on the parallel electrical bus, then the first or second genset controller;

1) varies operation of a respective one of the first and second alternator to synchronize the alternating electricity produced by that alternator to the electricity present on the parallel electrical bus; and

thereafter

2) operates a respective one of the first and second circuit breaker to apply the alternating electricity to the parallel electrical bus; and

d) implements a load sharing function by;

determining a given operating level of the respective alternator;

detecting an operating level of each of the other energy sources; and

adjusting an operation of the respective alternator so that the given operating level is substantially identical to the operating levels of the other energy sources.

9. The system as recited in claim 8, wherein the first generator produces three-phase electricity and the second generator produces single-phase electricity.

10. The system as recited in claim 8, wherein the first generator is an engine-generator set.

11. The system as recited in claim 8, wherein the second generator is selected from the group consisting of a photovoltaic array, a wind turbine generator, a geothermal powered electrical generator, and a heat pump.

12. A method for operating a generator arrangement to furnish alternating electricity to a parallel electrical bus to which one or more other energy sources also supply electricity, wherein the generator arrangement has an alternator that produces the alternating and a genset controller that regulates a voltage and a frequency of the alternating electricity, said method comprising:

the genset controller performing steps of;

a) sensing whether electricity is present on the parallel electrical bus;

b) if electricity is not present on the parallel electrical bus, operating a circuit breaker to apply the alternating electricity produced by the alternator to the parallel electrical bus;

c) if electricity is present on the parallel electrical bus;

1) synchronizing the alternating electricity produced by the alternator to the electricity on the parallel electrical bus; and

thereafter

2) operating the circuit breaker to apply the alternating electricity to the parallel electrical bus;

determining a first percentage of a given maximum power capacity at which the alternator is operating;

for each other energy source, detecting a percentage of respective maximum power capacities at which each other energy source is operating, thereby producing a percentage set;

calculating an average percentage from the first percentage and the percentage set; and

adjusting operation of the first generator until the alternator is operating at the average percentage of the given maximum power capacity.

13. The method as recited in claim 12 further comprising, when the genset controller determines that electricity is not present on the parallel electrical bus, sending a message to the other energy sources;

and

operating a circuit breaker to apply the alternating electricity to the parallel electrical bus only upon receipt of a reply message from all the other energy sources.

14. The method as recited in claim 12 wherein synchronizing the electricity comprises:

sensing a given occurrence of a characteristic of the alternating electricity produced by the generator;

sensing a particular occurrence of the characteristic of the electricity on the parallel electrical bus;

determining a difference in time between the given occurrence and the particular occurrence; and

altering operation of the first generator so that the difference in time is no greater than a predefined amount.

15. The method as recited in claim 14 wherein altering operation of the first generator comprises varying a speed of the first generator.

16. The method as recited in claim 12 further comprising sending an indication of the first percentage to the other energy sources.

17. The method as recited in claim 12 wherein detecting a percentage for each other energy source comprises receiving value from each other energy source.

18. A method for operating a generator arrangement to furnish alternating electricity to a parallel electrical bus to which one or more other energy sources are able to supply electricity, wherein the generator arrangement has an alternator that produces the alternating electricity and a genset controller that regulates voltage and frequency of the alternating electricity, said method comprising:

measuring a first level of power produced by the alternator;

for each other energy source, detecting a level of power being produced;

adjusting operation of the alternator so that the alternator and the other energy sources produce substantially identical levels of power;

measuring a first level of power comprises determining a first percentage of a maximum power capacity at which the alternator is operating;

for each other energy source, detecting a percentage of a respective maximum power capacity at which that other energy source is operating, thereby producing a percentage set, where the detecting comprises receiving an indication of that percentage from another energy source; and

adjusting operation of the alternator comprises calculating an average percentage from the first percentage and the percentage set, and adjusting the alternator so that the first percentage substantially equals the average percentage.

19. The method as recited in claim 18 further comprising sending an indication of the first percentage to each other energy source.