AU2023200575A1

AU2023200575A1 - Dewatering system

Info

Publication number: AU2023200575A1
Application number: AU2023200575A
Authority: AU
Inventors: Lachlan Sharpe
Original assignee: Berkshire Renewable Energy Pty Ltd
Current assignee: Berkshire Renewable Energy Pty Ltd
Priority date: 2022-02-04
Filing date: 2023-02-03
Publication date: 2023-08-24

Abstract

A dewatering system comprises a portable electric generator for generating an alternating current and a submersible pump that is deployable in a borehole. The submersible pump comprises a housing, wherein the housing contains a pump and an electric motor for operatively driving the pump to pump fluid from the borehole. A system controller sends control instructions to the submersible pump. A speed controller receives the alternating current from the generator and receives the control instructions from the system controller. The speed controller varies a voltage and frequency of the alternating current before supplying the alternating current to the electric motor so as to control an operating speed of the pump in accordance with the control instructions. The speed controller is attached to, or is disposed within, the housing such that the speed controller is cooled by the fluid that is pumped from the borehole by the pump. 1/4 CD o C 000 cco c co

Description

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DEWATERING SYSTEM

Field

[0001] The present invention relates to a dewatering system for use in the mining and construction industries.

Background

[0002] Electric submersible pumps (ESPs) are commonly deployed in boreholes to pump subterranean fluids to the surface. For example, EPSs are used to pump oil and water from wellbores and to control groundwater levels in mining and construction projects. The process of removing groundwater is commonly known as dewatering. When a grid-based supply of electricity is not available to power an ESP, electricity must be created and supplied locally using a portable electric generator. An example portable generator comprises a prime mover, such as an internal combustion engine or gas turbine, mechanically coupled to an alternator to produce AC power. The prime mover normally runs at a fixed speed such that the alternator outputs AC power at a fixed voltage and frequency. When dewatering is being performed, an ESP often needs to be operated at a variable speed. A speed control system is, therefore, connected between the generator and the ESP. A common type of speed control system is a variable frequency drive (VFD). The generator and VFD are deployed on the ground next to the wellhead.

[0003] The VFD modifies the frequency and voltage of the alternating current produced by the fixed-speed generator, as required, before supplying the current to the ESP via a power cable extending from the VFD down into the borehole. The electrical components used by the VFD to modify the frequency and voltage generate considerable heat. To remove this heat, a VFD normally comprises an air cooling system that is powered by the electrical current produced by the generator. The cooling system consumes significant power during use, particularly when the VFD is used in hot conditions, which reduces the power efficiency of the generator and VFD.

[0004] The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the present application.

Summary

[0005] According to the present invention there is provided a dewatering system, wherein the dewatering system comprises: a portable electric generator for generating an alternating current; a submersible pump that is deployable in a borehole and comprises a housing, the housing containing a pump and an electric motor for operatively driving the pump to pump fluid from the borehole; a system controller for sending control instructions to the submersible pump; and a speed controller that receives the alternating current from the generator and receives the control instructions from the system controller, wherein the speed controller is configured to vary a voltage and frequency of the alternating current before supplying the alternating current to the electric motor to control an operating speed of the pump in accordance with the control instructions, and wherein the speed controller is attached to or disposed within the housing such that the speed controller is cooled by the fluid pumped by the pump.

[0006] The speed controller may be disposed within a fluid-tight cavity in the housing.

[0007] The fluid-tight cavity may be positioned adjacent to a conduit that is adapted to transfer the fluid pumped by the pump to a fluid outlet of the submersible pump.

[0008] The speed controller may be disposed within a fluid-tight container attached to the housing.

[0009] The dewatering system may comprise at least one sensor configured to measure a measurable condition or state of the submersible pump, or of the fluid pumped by the pump, and the system controller may receive information from the sensor relating to the measurable condition or state and send the control instructions to the speed controller so as to control the operating speed of the pump in response to the information.

[0010] The system controller may store at least one set point relating to the measurable condition or state and may control the operating speed of the pump such that the set point is maintained.

[0011] The set point may be one of a set of values comprising a desired fluid pressure, a desired fluid flow rate and a desired fluid level.

[0012] The speed controller may comprise: a rectifier that transforms the alternating current received from the generator into a direct current; and an inverter that transforms the direct current into an output alternating current that is supplied to the electric motor, wherein the output alternating current comprises a voltage and frequency as required by the control instructions.

[0013] The rectifier may comprise a diode bridge circuit.

[0014] The inverter may include transistors configured to generate the output alternating current by pulse width modulation.

[0015] The speed controller may comprise a filter configured to smooth the direct current before the direct current is supplied to the inverter.

[0016] The filter may comprise a capacitor bank.

[0017] The electric motor may comprise a permanent magnet motor.

[0018] The generator may comprise a prime mover and an alternator, wherein the alternator is operatively driven by the prime mover to generate the alternating current received by the speed controller.

[0019] The generator may comprise a renewable generator system connected to an inverter, wherein the inverter transforms a direct current produced by the renewable generator system into the alternating current received by the speed controller.

[0020] The renewable generator system may comprise one or more solar cells.

Brief Description of Drawings

[0021] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a schematic side elevation view of a dewatering system according to an example embodiment of the invention; Figure 2 is a schematic side elevation view of a portable electric generator of the dewatering system;

Figure 3 is a sectional side elevation view of a submersible pump of the dewatering system deployed in a borehole; and Figure 4 is a diagram of an electrical circuit included in a speed controller of the dewatering system.

Description of Embodiments

[0022] Referring to the Figures, an example embodiment of the present invention provides a dewatering system 10. The system 10 comprises a portable electric generator 12 for generating an alternating current and a submersible pump 18 that is deployable in a borehole. The submersible pump 18 comprises a housing , wherein the housing 20 contains a pump 22 and an electric motor 24 for operatively driving the pump 22 to pump fluid from the borehole. The system 10 includes a system controller 26 for sending control instructions to the submersible pump 18. The system 10 also includes a speed controller 28 that receives the alternating current from the generator 12 and receives the control instructions from the system controller 26. The speed controller 28 varies a voltage and frequency of the alternating current before supplying the alternating current to the electric motor 24 so as to control an operating speed of the pump 22 in accordance with the control instructions. The speed controller 28 is attached to, or is disposed within, the housing 20 such that the speed controller 28 is cooled by the fluid that is pumped from the borehole by the pump 18.

[0023] The speed controller 28 is advantageously located such that its internal electrical components are cooled by the borehole fluid. More particularly, in the example depicted the speed controller 28 is contained in a fluid-tight cavity inside a casing 30 that is located inside of the pump housing 20. The casing 30 is positioned adjacent to a conduit 32 that transfers fluid pumped by the pump 22 toward a fluid outlet 34 of the submersible pump 18. In use, heat energy generated by the controller 28 is conducted through respective adjacent walls of the casing 30 and conduit 32 and absorbed by the fluid flowing through the conduit 32. The speed controller 28 may be positioned in other locations within the pump housing 20. For example, the speed controller 28 may be contained inside a tubular protector 35 that houses a drive shaft that rotationally couples the motor 24 to the fluid pump 22. In other examples, the speed controller 28 may be disposed within a fluid-tight container (not shown) that is attached to an outer surface or part of the pump housing 20. When the controller 28 is attached to the pump 18 outside of the housing 20, the speed controller 28 is cooled by the fluid in the borehole that surrounds the pump 18. It will be understood that this fluid is pumped by the pump 18 when the fluid is sucked into the inlet of the pump 18.

[0024] Referring to Figure 4, the speed controller 28 may comprise a rectifier 36, such as a diode bridge circuit, that transforms the alternating current received from the generator 12 into a direct current. An inverter 38 may transform the direct current into a second (output) alternating current that is supplied to the electric motor 24. The inverter 38 may generate the output current in accordance with the control instructions such that the output current's voltage and frequency is as required by the system controller 26. In one example, the inverter 38 may include a set of transistors configured to generate the output current at the desired voltage and frequency by pulse width modulation. The speed controller may also comprise a filter 40, such as a capacitor bank, for smoothing the direct current produced by the rectifier 36 before the direct current is supplied to the inverter 38.

[0025] The electric motor 24 may comprise any type of AC motor. In one example, the motor 24 may comprise an asynchronous AC motor, such as an AC induction motor (ACIM). In other examples, the motor 24 may comprise a synchronous AC motor, such as a permanent magnet synchronous motor (PMSM). A PMSM may be used to take advantage of the improved full load efficiencies provided by such motors. As ACIMs typically cost less to manufacture than PMSMs, an ACIM may be used if production cost is an important consideration.

[0026] The portable electric generator 12 may comprise a prime mover 14 that operatively drives an alternator 16 to, in turn, generate the alternating current output by the generator 12. The prime mover 14 may comprise any means for generating a rotational mechanical force to turn a drive shaft of the alternator 16. For example, the prime mover 14 may comprise a reciprocating engine (such as a diesel engine), a gas turbine, a wind turbine or a hydraulic turbine.

[0027] In other examples, the generator 12 may comprise a renewable generator system, such as one or more solar cells or wind turbines, that generates a direct current. The generator 12 may comprise an inverter (not shown) that transforms the direct current produced by the renewable generator system into the alternating current that is output by the generator 12. One or more batteries may also be included to store power produced by the renewable generator system. Electrical power stored in the batteries may be used to supply DC power to the inverter if and when the system controller 26 determines that the renewable generator system is incapable of supplying the necessary electric power to operate the submersible pump 18 at a required speed. For example, if the renewable generator system comprises solar cells, then the power stored in the batteries may be consumed during periods of time when insufficient sunlight is available to power the solar cells. In other examples, the generator 12 may comprise a hybrid configuration that includes one or more engine-alternator devices combined with one or more renewable-inverter devices.

[0028] The dewatering system 10 may also comprise at least one sensor that is configured to measure a measurable condition or state of the submersible pump 18 or a measurable condition or state of the fluid pumped by the pump 18. In the example depicted in the Figures, the system 10 includes a first sensor 42 that is deployed in the borehole. The system 10 also includes a second sensor 44 and a third sensor 46 that are both deployed on a headworks assembly 48 placed on a ground surface relative to the wellhead of the borehole. The second and third sensors 44, 46 may be attached to a pipe 50 on the headworks assembly 48 that carries the fluid pumped from the borehole by the submersible pump 18.

[0029] The first sensor 42 may comprise a submersible pressure transmitter, such as hydrostatic transducer. This type of sensor measures the pressure of fluid in the borehole at the sensor's position and generates an electrical signal based on the pressure reading that corresponds to the level of the fluid in the borehole. The second sensor 44 may comprise a pressure sensor for measuring the pressure of fluid flowing through the pipe 50 and the third sensor 46 may comprise a flow rate sensor for measuring the flow rate of the fluid flowing through the pipe 50. The system controller 26 may receive the respective signals generated by the sensors and control the operating speed of the pump 22 in response to such signals.

[0001] The system controller 26 may also comprise a storage device which stores at least one set point relating to the operating environment or condition of the pump 18. The system controller 26 may be configured such that in response to signals received from one or more of the sensors 42-46, the system controller 26 determines a target pump operating speed that causes the set point to be maintained. The system controller may cause the pump 18 to operate at the target speed by sending corresponding speed control instructions to the speed controller 28. For example, the set point may be either (i) a desired fluid pressure, (ii) a desired fluid flow rate and/or (iii) a desired fluid level that is to be maintained by the pump 18. The system controller 26 may control the pump speed by executing a proportional-integral-derivative (PID) loop to avoid overshoot and undershoot of the relevant set point. The system controller 26 may store and maintain any one of the foregoing set points. In other examples, the system controller 26 may store a set consisting of two or more of the foregoing set points (in any combination) and operate to maintain one of the set points in the set selectively at any one point in time. The relevant set point in the set that is maintained may be selected by an operator of the system 10 using a user input device connected to the system controller 26. In other examples, the system controller 26 may comprise logic that determines the relevant set point that needs to be maintained automatically based on information received from the sensors 42-46.

[0002] The system controller 26 may comprise a processor, a programmable logic controller (PLC), a programmable logic array (PLA) or similar electronic controller device. The system controller 26 may comprise a single integrated electronic controller device or multiple controller devices (including multiple processors or PLAs) connected together via a network, bus or similar communications system. In examples where the system controller comprises a processor, the processor will typically comprise a device that is capable of executing instructions encoding arithmetic, logical and/or I/O operations. The processor may, for example, comprise an arithmetic logic unit (ALU), a control unit and a plurality of registers. The processor may comprise a single core processor capable of executing one instruction at a time (or process a single pipeline of instructions) or a multi-core processor which simultaneously executes multiple instructions. The storage device of the system controller 26 may comprise a volatile or non-volatile memory device, such as RAM, ROM, EEPROM or flash memory, a magnetic or optical disk, a network attached storage (NAS) device or any other device capable of storing data. The storage device may be integral with the system controller 26 or it may be an external storage device in communication with the system controller 26 via a wired or wireless communication means such as, for example, a USB cable, optical fibre, ethernet or WiFi.

[0030] The skilled addressee will appreciate that certain features depicted in the figures may be shown for simplicity and clarity and have not necessarily been shown to scale. For example, the dimensions and/or relative positioning of some of the features may be exaggerated relative to other features to facilitate an understanding of the various example embodiments exemplifying the principles described herein. Also, common but well understood features that are useful or necessary in a commercially feasible embodiment may not be depicted in order to provide a less obstructed view of these various examples.

[0031]The location and disposition of the features depicted in the figures may vary according to the particular arrangements of the embodiment(s) as well as of the particular applications of such embodiment(s). References to positional descriptions in this specification are to be taken in context of the relevant example embodiments shown in the figures and are not to be taken as limiting the scope of the principles described herein to the literal interpretation of the term, but rather as would be understood by the skilled addressee.

[0032] For the purpose of this specification, the word "comprising" means "including but not limited to", and the word "comprises" has a corresponding meaning. It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.

[0033] The above embodiments have been described by way of example only and modifications are possible within the scope of the claims that follow.

Claims

1. A dewatering system, comprising: a portable electric generator for generating an alternating current; a submersible pump that is deployable in a borehole and comprises a housing, the housing containing a pump and an electric motor for operatively driving the pump to pump fluid from the borehole; a system controller for sending control instructions to the submersible pump; and a speed controller that receives the alternating current from the generator and receives the control instructions from the system controller, wherein the speed controller is configured to vary a voltage and frequency of the alternating current before supplying the alternating current to the electric motor to control an operating speed of the pump in accordance with the control instructions, and wherein the speed controller is attached to or disposed within the housing such that the speed controller is cooled by the fluid pumped by the pump.

2. The dewatering system according to claim 1, wherein the speed controller is disposed within a fluid-tight cavity in the housing.

3. The dewatering system according to claim 2, wherein the fluid-tight cavity is positioned adjacent to a conduit transferring the fluid pumped by the pump to a fluid outlet of the submersible pump.

4. The dewatering system according to claim 1, wherein the speed controller is disposed within a fluid-tight container attached to the housing.

5. The dewatering system according to any one of the preceding claims, wherein: the dewatering system comprises at least one sensor configured to measure a measurable condition or state of the submersible pump or of the fluid pumped by the pump; and the system controller receives information from the sensor relating to the measurable condition or state, and the system controller sends the control instructions to the speed controller so as to control the operating speed of the pump in response to the information.

6. The dewatering system according to claim 5, wherein the system controller stores at least one set point relating to the measurable condition or state, and wherein the system controller controls the operating speed of the pump such that the set point is maintained.

7. The dewatering system according to claim 6, wherein the set point is one of a set of values comprising a desired fluid pressure, a desired fluid flow rate and a desired fluid level.

8. The dewatering system according to any one of the preceding claims, wherein the speed controller comprises: a rectifier that transforms the alternating current received from the generator into a direct current; and an inverter that transforms the direct current into an output alternating current that is supplied to the electric motor, wherein the output alternating current comprises a voltage and frequency as required by the control instructions.

9. The dewatering system according to claim 8, wherein the rectifier comprises a diode bridge circuit.

10. The dewatering system according to claim 8 or 9, wherein the inverter includes transistors configured to generate the output alternating current by pulse width modulation.

11. The dewatering system according to any one of claims 8 to 10, wherein the speed controller comprises a filter configured to smooth the direct current before the direct current is supplied to the inverter.

12. The dewatering system according to claim 11, wherein the filter comprises a capacitor bank.

13. The dewatering system according to any one of the preceding claims, wherein the electric motor comprises a permanent magnet motor.

14. The dewatering system according to any one of the preceding claims, wherein the generator comprises a prime mover and an alternator, wherein the alternator is operatively driven by the prime mover to generate the alternating current received by the speed controller.

15. The dewatering system according to any one of the preceding claims, wherein the generator comprises a renewable generator system connected to an inverter, wherein the inverter transforms a direct current produced by the renewable generator system into the alternating current received by the speed controller.

16. The dewatering system according to claim 15, wherein the renewable generator system comprises one or more solar cells.