SYSTEM AND METHOD FOR CHARGING A CAPACITOR USED TO POWER MEASUREMENT-WHILE-DRILLING EQUIPMENT

• US 20160064966A1
• Filed: 03/07/2014
• Published: 03/03/2016
• Est. Priority Date: 03/07/2013
• Status: Active Grant

• Current Assignee: Evolution Engineering Inc .
• Original Assignee: Evolution Engineering Inc .
• Inventors: LIU, Jili, PAN, Xia
• Granted Patent: US 9,608,467 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: E21B 41/0085 Adaptations of electric power generating means for use in boreholes
• CPC Class Codes: H02J 7/0068 Battery or charger load switching, e.g. concurrent charging and load supply H02J7/0013 takes precedence
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/345 using capacitors as storage or buffering devices

Abstract

A system for charging a capacitor used to power measurement-while-drilling equipment includes a power bus, which is electrically connected to the capacitor; a first pair of battery terminals; switching circuitry for electrically connecting the power bus to and disconnecting the power bus from the first pair of battery terminals; and a controller, for controlling the switching circuitry, which is configured to charge the capacitor by applying a first pulse width modulated control signal to control the switching circuitry. The first pulse width modulated control signal has a duty cycle selected such that the voltage of the first battery remains above a first minimum operating voltage while the capacitor is being charged.

Claims

1. A system for charging a capacitor used to power measurement-while-drilling equipment, the system comprising:

(a) a power bus, wherein the capacitor is electrically connected to the power bus;

(b) a first pair of battery terminals for connecting to a first battery;

(c) switching circuitry operable to electrically connect the power bus to and to disconnect the power bus from the first pair of battery terminals; and

(d) a controller, operable to control the switching circuitry, and configured to charge the capacitor by intermittently connecting the power bus to and disconnecting the power bus from the first pair of battery terminals, wherein durations for which the power bus is connected to the first pair of battery terminals are selected such that battery voltage remains above a first minimum operating voltage while the capacitor is being charged.

2. The system of claim 1 wherein the controller is configured to charge the capacitor by applying a first pulse width modulated control signal to control the switching circuitry, wherein the first pulse width modulated control signal has a duty cycle selected such that the voltage of the first battery remains above the first minimum operating voltage while the capacitor is being charged.

3. The system of claim 2 wherein the minimum operating voltage is a reset voltage, and wherein the controller is further configured to reset the system if the voltage of the first battery drops below the reset voltage.

4. The system of claim 3, wherein the controller is further configured to disconnect the first pair of battery terminals from the power bus when the voltage of the first battery drops below a voltage floor, wherein the voltage floor is above the reset voltage.

5. The system of claim 4 wherein the voltage floor is approximately 50% of the maximum voltage of the first battery.

6. The system of claim 2 wherein the first pulse width modulated control signal is configured to cause the first battery to be connected to the power bus for approximately 1.5 ms and disconnected from the power bus for approximately 2 ms for each charging cycle.

7. The system of claim 2 wherein the controller is configured to charge the capacitor for a charging period.

8. The system of claim 7 wherein the controller is further configured to electrically connect the first pair of battery terminals to the capacitor following the charging period and to subsequently indefinitely keep the first pair of battery terminals and the capacitor electrically connected.

9. The system of claim 2 further comprising a first voltmeter, communicative with the controller, and electrically connected in parallel to the first pair of battery terminals such that the voltage of the first battery can be determined.

10. The system of claim 2 further comprising a first ammeter electrically connected in series to the first pair of battery terminals such that current flowing out of the first battery can be determined.

11. The system of claim 2 further comprising a second pair of battery terminals for connecting to a second battery and electrically connected in parallel to the first pair of battery terminals, wherein the switching circuitry is operable to electrically connect the power bus to and to disconnect the power bus from the second pair of battery terminals independently from the first pair of battery terminals and wherein the controller is further configured to apply a second pulse width modulated control signal to the switching circuitry such that the system alternates between:

(a) only charging the capacitor using the first battery by electrically connecting the first pair of battery terminals to the power bus and electrically disconnecting the second pair of battery terminals from the power bus; and

(b) only charging the capacitor using the second battery by electrically connecting the second pair of battery terminals to the power bus and electrically disconnecting the first pair of battery terminals from the power bus,

wherein the second pulse width modulated control signal has a duty cycle selected such that the voltage of the second battery remains above a second minimum operating voltage while the capacitor is being charged.

12. The system of claim 11 wherein the first and second minimum operating voltages are identical.

13. The system of claim 12 wherein the minimum operating voltages are a reset voltage, and wherein the controller is further configured to reset the system if the voltage of the first or second batteries drops below the reset voltage.

14. The system of claim 13, wherein the controller is further configured to disconnect the first pair of battery terminals from the power bus when the voltage of the first battery drops below a first voltage floor and to disconnect the second pair of battery terminals from the power bus when the voltage of the second battery drops below a second voltage floor, wherein the voltage floors are above the reset voltage.

15. The system of claim 14 wherein the first and second voltage floors are identical.

16. The system of claim 15 wherein the voltage floors are approximately 50% of the maximum voltage of the first battery.

17. The system of claim 11 wherein the pulse width modulated control signals are configured to cause the capacitor to always be charged by at least one of the batteries if the voltage of the capacitor is lower than the voltage of at least one of the batteries.

18. The system of claim 11 wherein the pulse width modulated control signals are configured to cause each of the batteries to be connected to the power bus for approximately 1.5 ms for each charging cycle and disconnected from the power bus for approximately 2.0 ms for each charging cycle.

19. The system of claim 11 wherein the controller is configured to charge the capacitor for a charging period.

20. The system of claim 19 wherein the controller is further configured to electrically connect at least one of the pairs of battery terminals to the capacitor following the charging period and to subsequently indefinitely keep the at least one of the pairs of battery terminals and the capacitor electrically connected.

21. The system of claim 11 further comprising first and second voltmeters, communicative with the controller, and electrically connected in parallel to the first and second pairs of battery terminals, respectively, such that the voltages of the first and second batteries can be determined.

22. The system of claim 11 further comprising first and second ammeters electrically connected in series to the first and second pairs of battery terminals, respectively, such that current flowing out of the first and second batteries can be determined.

23. A method for charging a capacitor used to power measurement-while-drilling equipment, the method comprising intermittently electrically connecting the capacitor to and disconnecting the capacitor from a first battery, wherein durations for which the capacitor and the first battery are electrically connected are selected such that first battery voltage remains above a first minimum operating voltage while the capacitor is being charged.

24. The method of claim 23 wherein a first pulse width modulated control signal is used to intermittently electrically connect the capacitor to and disconnect the capacitor from a first battery, wherein the first pulse width modulated control signal has a duty cycle selected such that the voltage of the first battery remains above the first minimum operating voltage while the capacitor is being charged.

25. The method of claim 24 wherein the minimum operating voltage is a reset voltage, and further comprising:

(a) monitoring the voltage of the first battery; and

(b) resetting circuitry used to charge the capacitor if the voltage of the first battery drops below the reset voltage.

26. The method of claim 25 further comprising disconnecting the first pair of battery terminals from the capacitor when the voltage of the first battery drops below a voltage floor, wherein the voltage floor is above the reset voltage.

27. The method of claim 26 wherein the voltage floor is approximately 50% of the maximum voltage of the first battery.

28. The method of claim 23 wherein the first pulse width modulated control signal is configured to cause the first battery to be connected to the power bus for approximately 1.5 ms and to be disconnected from the power bus for approximately 2 ms for each charging cycle.

29. The method of claim 23 wherein the first battery charges the capacitor for a charging period.

30. The method of claim 29 further comprising, following the charging period, electrically connecting the first pair of battery terminals to the capacitor and subsequently indefinitely keeping the first pair of battery terminals and the capacitor electrically connected.

31. The method of claim 24 further comprising applying a second pulse width modulated control signal to intermittently electrically connect the capacitor to and disconnect the capacitor from a second battery, wherein the pulse width modulated control signals are configured to alternate between:

(a) only charging the capacitor using the first battery by electrically connecting the first pair of battery terminals to the power bus and electrically disconnecting the second pair of battery terminals from the power bus; and

(b) only charging the capacitor using the second battery by electrically connecting the second pair of battery terminals to the power bus and electrically disconnecting the first pair of battery terminals from the power bus,

wherein the second pulse width modulated control signal has a duty cycle selected such that the voltage of the second battery remains above a second minimum operating voltage while the capacitor is being charged.

32. The method of claim 31 wherein the first and second minimum operating voltages are identical.

33. The method of claim 32 wherein the minimum operating voltages are a reset voltage and further comprising:

(a) monitoring the voltages of the first and second batteries; and

(b) resetting circuitry used to charge the capacitor if the voltage of the first battery drops below the reset voltage.

34. The method of claim 33 further comprising disconnecting the first pair of battery terminals from the power bus when the voltage of the first battery drops below a first voltage floor and disconnecting the second pair of battery terminals from the power bus when the voltage of the second battery drops below a second voltage floor, wherein the voltage floors are above the reset voltage.

35. The method of claim 34 wherein the first and second voltage floors are identical.

36. The method of claim 35 wherein the voltages of the first and second batteries are identical and the voltage floors are approximately 50% of the maximum voltage of the first battery.

37. The method of claim 31 wherein the pulse width modulated control signals are configured to cause the capacitor to always be charged by at least one of the batteries if the voltage of the capacitor is lower than the voltage of at least one of the batteries.

38. The method of claim 31 wherein the pulse width modulated control signals are configured to cause each of the batteries to alternately be connected to the power bus for approximately 1.5 ms for each charging cycle.

39. The method of claim 31 wherein the capacitor is charged for a charging period.

40. The method of claim 39 further comprising electrically connecting at least one of the pairs of battery terminals to the capacitor following the charging period and subsequently indefinitely keeping the at least one of the pairs of battery terminals and the capacitor electrically connected.

41. A non-transitory computer readable medium having encoded thereon statements and instructions configured to cause a controller to perform the method of claim 23.