Hybrid power plant for improved efficiency and dynamic performance

• US 10,389,113 B2
• Filed: 08/11/2016
• Issued: 08/20/2019
• Est. Priority Date: 06/16/2010
• Status: Active Grant

• Current Assignee: Transocean Sedco Forex Ventures Limited (Transocean Limited)
• Original Assignee: Transocean Sedco Forex Ventures Limited (Transocean Limited)
• Inventors: Bourgeau, Edward P.
• Primary Examiner(s): Perez Borroto, Alfonso
• Assistant Examiner(s): Yeshaw, Esayas
• Application Number:
  US15/234,771
• Publication Number:
  US 20160352099A1
• Time in Patent Office: 1,104 Days
• CPC Class Codes: H02J 1/04 Constant-current supply systems
• CPC Class Codes: H02J 1/12 Parallel operation of dc generators with converters, e.g. with mercury-arc rectifier
• CPC Class Codes: H02J 1/14 Balancing the load in a network
• CPC Class Codes: H02J 3/32 using batteries with converting means
• CPC Class Codes: H02M 7/68 by static converters

Abstract

A hybrid power plant is characterized by a substantially constant load on generators regardless of momentary swings in power load. Short changes in power load are accommodated by DC components such as capacitors, batteries, resistors, or a combination thereof. Resistors are used to consume power when loads in the power plant are generating excess power. Capacitors are used to store and deliver power when the loads in the power plant demand additional power. Reducing rapid changes in power load as seen by the generators allows the generators to operate at higher efficiencies and with reduced emissions. Additionally, power plants employing combinations of generators, loads, and energy storage devices have increased dynamic performance.

Claims

1. An apparatus, comprising:

an AC power source coupled to an AC bus;

a bidirectional AC-to-DC converter coupled to the AC bus and a DC bus and configured to exchange energy from the AC bus to the DC bus and from the DC bus to the AC bus;

a first AC load coupled to the AC bus;

an active power compensation system coupled to the DC bus, wherein the active power compensation system comprises an energy storage device coupled to the DC bus through a first switch, and wherein the active power compensation system is configured to;

control the first switch to deliver power to the first AC load through the DC bus, through the bidirectional AC-to-DC converter, and through the AC bus during a time when a power output of the AC generator is lower than a power demand of the AC load; and

control the first switch to deliver power to the energy storage device through the AC bus, through the bidirectional AC-to-DC converter, and through the DC bus during a time when a power output of the AC power source is higher than a power demand of the AC load.

2. The apparatus of claim 1, further comprising a summation block on the AC bus coupled to the AC power source, the AC load, and the bidirectional AC-to-DC converter, wherein the active power compensation system is further configured to maintain an approximately constant load on the AC power source through the summation block.

3. The apparatus of claim 1, further comprising:

a DC-to-AC converter coupled to the DC bus; and

a second AC load coupled to the DC bus through the DC-to-AC converter.

4. The apparatus of claim 3, wherein the DC-to-AC converter is bidirectional to allow power regeneration of the motor to provide power to the DC bus.

5. The apparatus of claim 1, wherein the first switch comprises a DC-to-DC converter.

6. The apparatus of claim 1, wherein the energy storage device comprises at least one of an ultracapacitor, a capacitor, a battery, and a fly wheel.

7. The apparatus of claim 1, wherein the active power compensation system further comprises a power consumption device coupled to the DC bus through a second switch, and wherein the active power compensation system is configured to control the second switch to consume power through the power consumption device during a time when a power output of the AC power source is higher than a power demand on the AC power source.

8. The apparatus of claim 7, wherein the power consumption device comprises at least one of a resistive element, a variable resistive element, and a water brake.

9. The apparatus of claim 1, wherein the AC power source comprises one or more AC generators.

10. The apparatus of claim 1, further comprising a DC load coupled to the DC bus.

11. A method of reducing variations in a power load on an AC power source in a power plant, comprising:

energizing an AC bus from an AC power source;

powering an AC load with the AC bus;

transferring energy from the AC bus to a DC bus through a bidirectional AC-to-DC converter;

storing energy in a power storage device from the DC bus by transferring energy through a first switch;

routing power from the power storage device through the DC bus, through the bidirectional AC-to-DC converter, and through the AC bus to the AC load during a time when a power output of the AC power source is lower than a power demand on the AC power source; and

routing power from the AC power source through the AC bus, through the bidirectional AC-to-DC converter, and through the DC bus to the power storage device during a time when a power output of the AC power source is higher than a power demand on the AC power source.

12. The method of claim 11, further comprising maintaining an approximately constant load on the AC power source by routing power between the AC power source, the AC load, and the power storage device through a summation block.

13. The method of claim 11, further comprising powering a second AC load from the DC bus through a DC-to-AC converter.

14. The method of claim 13, further comprising providing power to the DC bus from the second AC load through the DC-to-AC converter.

15. The method of claim 11, wherein the step of routing power to the power storage device comprises routing power through a DC-to-DC converter.

16. The method of claim 11, wherein the step of routing power to the power storage device comprises routing power to at least one of an ultracapacitor, a capacitor, a battery, and a fly wheel.

17. The method of claim 11, further comprising routing power from the AC power source through the AC bus, through the bidirectional AC-to-DC converter, and through the DC bus to a power consumption device during a time when a power output of the AC power source is higher than a power demand on the AC power source.

18. The method of claim 17, wherein the step of routing power to a power consumption device comprises routing power to at least one of a resistive element, a variable resistive element, and a water brake.

19. The method of claim 11, further comprising power a DC load from the DC bus.

20. The method of claim 11, wherein the step of energizing an AC bus from an AC power source comprises energizing an AC bus from one or more AC generators.

21. An active power compensation system to reduce power load variations in a power plant having an AC power source coupled to an AC bus, a bidirectional AC-to-DC converter coupled to the AC bus and a DC bus and configured to exchange energy from the AC bus to the DC bus and from the DC bus to the AC bus, an AC load coupled to the AC bus, and a switch coupled to the DC bus, the system comprising:

an energy storage device coupleable to the DC bus through the switch; and

a controller configured to;

control the switch to deliver power to the first AC load through the DC bus, through the bidirectional AC-to-DC converter, and through the AC bus during a time when a power output of the AC generator is lower than a power demand of the AC load; and

control the switch to deliver power to the energy storage device through the AC bus, through the bidirectional AC-to-DC converter, and through the DC bus during a time when a power output of the AC power source is higher than a power demand of the AC load.

22. The active power compensation system of claim 21, wherein the power plant further includes a summation block on the AC bus coupled to the AC power source, the AC load, and the bidirectional AC-to-DC converter, the active power compensation system configured to maintain an approximately constant load on the AC power source through the summation block.

23. The active power compensation system of claim 21, wherein the power plant further includes (1) a DC-to-AC converter coupled to the DC bus, and (2) a second AC load coupled to the DC Bus through the DC-to-AC converter.

24. The active power compensation system of claim 23, wherein the DC-to-AC converter is bidirectional to allow power regeneration of the motor to provide power to the DC bus.

25. The active power compensation system of claim 21, wherein the energy storage device includes at least one of an ultracapacitor, a capacitor, a battery, or a fly wheel.

26. The active power compensation system of claim 21, wherein the controller is configured to control the switch to deliver power to the energy storage device through the AC bus, through the bidirectional AC-to-DC converter, and through the AC bus in response to the power output of the AC generator being lower than the power demand of the AC load.