GENERATOR LOAD CONTROL

• US 20150222121A1
• Filed: 02/03/2015
• Published: 08/06/2015
• Est. Priority Date: 02/04/2014
• Status: Active Grant

• Current Assignee: Nabors Drillling Technologies USA, Inc.
• Original Assignee: Canrig Drilling Technology Limited (Nabors Industries Limited)
• Inventors: KUTTEL, Beat, Williams, Kevin, PACE, Gary, SCARBOROUGH, Tommy, GARAGHTY, James
• Granted Patent: US 9,537,315 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02J 2310/12 The local stationary network supplying a household or a building
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02J 3/003 Load forecast, e.g. methods or systems for forecasting future load demand
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 3/40 Synchronising a generator for connection to a network or to another generator
• CPC Class Codes: H02P 9/00 Arrangements for controlling electric generators for the purpose of obtaining a desired output Ward-Leonard arrangements H02P7/34; vector control H02P21/00; feeding a network by two or more generators H02J; for charging batteries H02J7/14

Abstract

A power system for an electrical system with highly fluctuating loads is powered by one or more power sources that are slow to react to load changes. The power sources are connected to electrical equipment used on the drill rig which provide active load to the generators. One or more load banks may be positioned to provide passive load to the generators to maintain generally constant generator load, while allowing for instant access to power as active load increases. Generators may be run at 100% capacity, a maximum efficient capacity, or at a high enough level to allow for a sufficiently rapid increase in power output. At least one parameter of a drilling operation may be utilized to anticipate load demand changes.

Claims

1. A power system for running an electrically driven device using a power load defining an active load when in operation comprising:

a generator, the generator having a minimum efficient load rating, the generator electrically coupled to the electrically driven device;

a load bank, the load bank electrically coupled to the generator and positioned to provide a power load defining a passive load on the generator when engaged; and

a controller positioned to engage the load bank and activate the passive load.

2. The power system of claim 1, wherein the load bank is adapted to provide one or more of a resistive, inductive, liquid, wind resistance, regenerative, inertial, or capacitive load or to provide load to charge a battery or to run a motor/generator set.

3. The power system of claim 1, wherein the load bank is electrically coupled to the generator via an inverter, the inverter being controlled by the controller to increase or decrease the amount of passive load connected to the generator.

4. The power system of claim 3, wherein the inverter is coupled to a variable frequency drive, the variable frequency drive having a DC link, so that the load bank draws power from the DC link.

5. The power system of claim 3, wherein the inverter is driven by a PWM signal sent by the controller, and the passive load is determined by the duty cycle of the inverter.

6. The power system of claim 5, wherein the duty cycle of the PWM signal proportionally controls the passive load of the load bank from 0-100% of the load capability of the load bank.

7. The power system of claim 5, wherein the load bank further comprises one or more three phase resistive load banks, and the duty cycle is calculated according to:

8. The power system of claim 1, wherein the electrically driven device is an electric motor capable of dynamic braking, and the power generated thereby is dissipated by the load bank.

9. The power system of claim 3, wherein the inverter comprises a chopper.

10. The power system of claim 1, wherein the controller is a step change controller, a state controller, a proportional controller, a proportional integral controller, a proportional integral derivative controller, a proportional derivative controller, an adaptive controller, or a predictive controller.

11. The power system of claim 10, wherein a process variable for the controller is actual generator power load.

12. The power system of claim 11, comprising an additional variable for the controller selected from the group consisting of depth of wellbore, hook load, pump pressure, pump rate, length of drill string, weight on bit, increase or change in current, increase or change in power, and number of engines online, or any changes or requested changes thereto.

13. A method for controlling a load bank comprising:

providing a power system for running one or more electrically driven devices using a power load defining an active load when in operation, the power system including;

one or more generators, each generator having a minimum efficient load rating, each generator electrically coupled to the electrically driven device;

the load bank, the load bank electrically coupled to the generator and positioned to provide a power load defining a passive load on the generator when engaged; and

a controller positioned to engage the load bank and activate the passive load;

calculating the minimum total load of the one or more generators;

calculating a total power demand of the one or more electrically driven devices;

calculating, from the minimum total load and the total power demand, a load bank power demand; and

engaging the load bank with the controller to provide passive load to the generators generally equal to the load bank power demand.

14. The power system of claim 13, wherein the load bank is adapted to provide one or more of a resistive, inductive, liquid wind resistance, regenerative, inertial, or capacitive load or to provide load to charge a battery or to run a motor/generator set.

15. The method of claim 13, wherein the load bank is electrically coupled to the generator via an inverter, the inverter being controlled by the controller to selectively connect and disconnect the load bank from the generator.

16. The method of claim 15, wherein the inverter is coupled to a variable frequency drive, the variable frequency drive having a DC link, so that the load bank draws power from the DC link.

17. The method of claim 15, wherein the inverter is driven by a PWM signal sent by the controller, and the passive load is determined by the duty cycle of the inverter.

18. The method of claim 17, wherein the duty cycle of the PWM signal proportionally controls the passive load of the load bank from 0-100% of the load capability of the load bank.

19. The method of claim 17, wherein the load bank further comprises one or more three phase resistive load banks, and the duty cycle is calculated according to:

20. The method of claim 13, wherein the output power of the one or more generators is controllable by the controller, and the method further comprises:

controlling the power output of the one or more generators based on the total power demand.

21. The method of claim 13, wherein a process variable for the controller is actual generator load.

22. The method of claim 21, comprising an additional variable for the controller selected from the group consisting of depth of wellbore, hook load, pump pressure, pump rate, length of drill string, weight on bit, increase or change in current, increase or change in power, and number of engines online, or any changes or requested changes thereto.