Solar drive control system for oil pump jacks

Abstract

A system for supplementing the electric power needed by a pump jack electric motor, thereby reducing the electric power purchased from the local utility or power supplier. The system comprises a solar photovoltaic system, or other forms of renewable energy, and regenerated power from the electric motor or drive. The system can be both “on-grid” and “off-grid.” Battery banks and capacitor banks may be used to store energy.

Claims

1. An apparatus for use with an electric power grid and an electric motor, the apparatus comprising: a variable frequency drive configured to electrically connect to the electric power grid and configured to drive the electric motor, the variable frequency drive comprising a DC buss; a DC capacitor bank configured to store electric power; and interconnection circuitry electrically connected to the DC capacitor bank, wherein the DC buss of the variable frequency drive is configured to be electrically connected to the DC capacitor bank via the interconnection circuitry such that the electric power from the DC capacitor bank is applied through the interconnection circuitry to the DC buss, is converted to AC power, and is provided to the electric motor.

2. The apparatus of claim 1, wherein energy to run the electric motor is pulled from both the DC capacitor bank and from the electric power grid.

3. The apparatus of claim 2, wherein excess electric power is directed to the electric power grid.

4. The apparatus of claim 1, wherein all energy needed to run the electric motor is pulled from the DC capacitor bank.

5. The apparatus of claim 1, wherein the variable frequency drive is a regenerative variable frequency drive configured to generate energy from the electric motor during operation of the electric motor.

6. The apparatus of claim 1, wherein the DC capacitor bank comprises nickel oxide hydroxide high amperage capacitors.

7. The apparatus of claim 1, wherein the variable frequency drive comprises a regenerative unit connected to the electric power grid and to the DC buss, the regenerative unit being configured to generate energy from the electric motor during operation of the electric motor.

8. The apparatus of claim 1, wherein the variable frequency drive comprises the DC buss at a first DC voltage; and wherein the DC capacitor bank is configured to store the electric power at a second DC voltage different from the first DC voltage.

9. The apparatus of claim 8, wherein the interconnection circuitry is configured to convert the second DC voltage associated with the DC capacitor bank to the first DC voltage associated with the DC buss.

10. The apparatus of claim 1, wherein the interconnection circuitry comprises an inverter configured to convert single-phase AC power at a first voltage to DC power at a second voltage for the DC buss, the second voltage being higher than the first voltage.

11. The apparatus of claim 1, further a DC battery bank electrically connected to the interconnection circuitry.

12. The apparatus of claim 11, wherein the interconnection circuitry is configured to allow level flow to the DC capacitor bank and is configured to stop reverse flow to the DC battery bank.

13. The apparatus of claim 11, further comprising a DC charger electrically connected to the DC battery bank.

14. The apparatus of claim 13, further comprising at least one renewable energy source electrically connected to the DC charger.

15. The apparatus of claim 14, wherein the at least one renewable energy source comprises a wind turbine and/or a solar photovoltaic system.

16. A pump jack used with an electric power grid, the pump jack comprising: an electric motor; and an apparatus according to claim 1.

17. An apparatus used with an electric power grid and an electric motor, the apparatus comprising: a variable frequency drive comprising a regenerative unit, a DC buss, a rectifier stage, a DC buss filter, and an inverter stage, the variable frequency drive being configured to electrically connect between the electric power grid and the electric motor and being configured to drive the electric motor with three-phase AC power, the regenerative unit being configured to generate energy from the electric motor during operation of the electric motor; and a DC capacitor bank being electrically connected to the DC buss of the variable frequency drive, the DC capacitor bank being configured to store DC power from the DC buss as stored DC power and being configured to supply the stored DC power to the DC buss for conversion to the three-phase AC power to drive the electric motor.

18. The apparatus of claim 17, comprising interconnection circuitry electrically connected between the DC buss and the DC capacitor bank.

19. The apparatus of claim 18, comprising: a DC battery bank electrically connected to the interconnection circuitry; and a DC charger electrically connected to the DC battery bank, the DC charger configured to electrically connect to at least one renewable energy source, wherein the interconnection circuitry is configured to allow level flow to the DC capacitor bank and is configured to stop reverse flow to the DC battery bank.

20. A pump jack used with an electric power grid, the pump jack comprising: an electric motor; and an apparatus according to claim 17.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a view of a system in accordance with an embodiment of the present invention.

(2) FIG. 2 shows a view of a system with direct connection between the solar array and the regenerative unit of the variable speed drive.

(3) FIG. 3 shows a view of an “off-grid” system.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(4) In various exemplary embodiments, the present invention comprises a system for supplementing the electric power needed by a pump jack electric motor, thereby reducing the electric power purchased from the local utility or power supplier. In one embodiment, the system comprises a solar photovoltaic system and regenerated power from the electric motor or drive. The system can be both “on-grid” and “off-grid.”

(5) In an “on-grid” embodiment, as seen in FIG. 1, the system allows for a balanced connection between the utility power grid 100 and a solar photovoltaic system 10 through the DC buss of a regenerative variable frequency drive (VFD), also referred to by several other terms, including, but not limited to, variable speed drive, variable speed controller, or similar terms 200. In general, the power required to operate the pump jack motor or drive is provided by the solar photovoltaic system 10 and by the energy from the regenerative action from the operation of the pump jack on the electric motor. Any additional power required to operate the pump jack motor may come from the utility power grid 100. Any excess power may be sold back to the local utility via a “net meter” agreement or similar arrangement.

(6) As seen in FIG. 1, in one embodiment the solar photovoltaic system comprises an array of solar panels 12 (with kW output sized by load), connected through individual solar inverters 14 (which, in the embodiment shown, converts 24V DC to 240V AC) to a transformer 16, which in turn is connected to the power distribution box 18. In this embodiment, the transformer converts 240V AC to 480V AC single phase. The power distribution box is connected to the power grid 100 through a meter 102. The VFD with front-end regenerative unit controls the speed of the motor, and is grid tied to the invertor for the solar array system converting 480V AC single phase to 480V three phase. The regenerative unit may be integrated with the VFD, or may be a separate unit connected thereto.

(7) As seen in FIG. 2, the solar photovoltaic system 10 may be connected directly to the common DC buss on the regenerative VFD 200, which allows the regenerative drive to convert energy produced by the solar photovoltaic system (which is DC energy) to synchronized 3-phase waveforms. This is the utility-required format for energy passed from the system to the utility grid. In the embodiment shown, a second transformer 22 is added (in this embodiment, converting 240V AC to 480 V AC), and is connected to inverter 202, which inverts 480V AC single phase to 650V DC, thereby tying the energy from the solar panel array directly to the VFD 200.

(8) In several embodiments, the regenerative capabilities of the drive must meet or exceed all utility requirements for power filtering and harmonic issues that are required for direct connection of the drive to the utility with respect to the driver supplying power back to the utility. The regenerative drive must meet or exceed all utility requirements concerning direct interconnection guidelines for small generator interconnect agreements. For both of the above examples, the parameters for the VFD may be adjusted to increase the amount of regenerated energy and optimize the power usage of the pump jack.

(9) While the above discussion was in the context of solar power, other forms of renewable energy sources may be used, including, but not limited to, wind and hydro-electric. These may be used separately, or in combination.

(10) In an “off-grid” embodiment with combined renewable energy sources, as seen in FIG. 3, the system captures and/or reuses the power generated from a solar photovoltaic array 10, an optional wind turbine or wind turbine array 20, as well as the regenerated power from the pump jack drive. Regenerative power from the pump jack drive may be stored in a DC capacitor bank (in this example, 48V) 40, and fed back into the DC buss of the variable frequency drive 200. The solar and wind energy are directed through a DC battery charger 32 (with size determined by the amount of energy generated by the solar array and wind turbine; in this example, 48V DC), and may be stored in a DC battery bank (in this example, 48V DC) 30. In one embodiment, the batteries may be lithium ion or lead acid batteries, and sized based on expected loads.

(11) The capacitor bank is the storage bank for regenerated power from the motor, and allows the regenerated power to be stored and reused. In one embodiment, the bank comprises nickel oxide hydroxide high amperage capacitors.

(12) Energy needed to run the pump jack motor is pulled from the capacitor bank 40, with additional energy as needed pulled from the battery bank 30, through a DC interconnection box 44. The interconnection box allows for level flow of DC power back to the capacitor bank, but stopping any reverse flow to the battery bank. The interconnection box is connected to inverter 202, which inverts 480V AC single phase to 650V DC (as described above for the direct connection embodiment).

(13) In another embodiment where the system is connected to the power grid as well, the power grid also may be a source of energy to make up any difference. The battery bank and capacitor bank are sized by the load needed to operate the respective pump jack drive or motor. The VFD 200 controls the speed of the motor, and acts as inverter for on-grid and off-grid configurations.

(14) Thus, it should be understood that the embodiments and examples described herein have been chosen and described in order to best illustrate the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to best utilize the invention in various embodiments and with various modifications as are suited for particular uses contemplated. Even though specific embodiments of this invention have been described, they are not to be taken as exhaustive. There are several variations that will be apparent to those skilled in the art.