AU2020103197B4

AU2020103197B4 - Power and control of a submersible pump

Info

Publication number: AU2020103197B4
Application number: AU2020103197A
Authority: AU
Inventors: Mark Vincent Keogh; Anthony Carl Reid
Original assignee: LAA Industries Pty Ltd
Current assignee: LAA Industries Pty Ltd
Priority date: 2016-08-16
Filing date: 2020-11-03
Publication date: 2021-07-15
Anticipated expiration: 2025-08-05
Also published as: AU2023214334A1; AU2017210650C1; AU2021203584A1; AU2020103197A4; AU2019203740A1; AU2017210650A1; AU2021107164B4; AU2021107164A4; AU2017210650B2

Abstract

A power and control system for a dewatering submersible pump includes a generator assembly, an automatic voltage regulator (AVR), an engine control unit, a system controller, a circuit breaker, human machine interface (HMI), and a network interface. The generator assembly comprises an engine coupled to an alternator. The power and control system is electrically connected to at least one motor, which powers a submersible pump for dewatering. The motor or motors can be started and controlled by the generator assembly of the power and control system.

Description

AUSTRALIA

Patents Act 1990

COMPLETE SPECIFICATION

Invention title:

"POWER AND CONTROL OF A SUBMERSIBLE PUMP"

Applicant:

LAA INDUSTRIES PTY LTD

Associated provisional applications:

The following statement is a full description of the invention, including the best method of performing it known to me:

"POWER AND CONTROL OF A SUBMERSIBLE PUMP"

Field of the Invention

[0001] The present invention relates to submersible pumps used in dewatering applications, such as within the Australian mining industry. In particular, it relates to the powering of such pumps when mains power supply is not available.

Background to the Invention

[0002] Mining operations frequently occur below the local water table. In such operations, it is necessary to remove local ground water by an operation known as dewatering. Dewatering is achieved by drilling a bore; locating a submersible pump within the bore; and operating the pump to remove water from the vicinity of the pump.

[0003] Submersible pumps used in dewatering are typically driven by an electrically powered motor. In a typical installation the motor may be in the between 7.5kW and 500kW in power, running at between 30Hz and 50Hz.

[0004] Where mains power is not available, the electrical power for the motor must be generated on the surface. This is typically achieved by use of a generator having an internal combustion engine which drives an alternator.

[0005] In a typical installation, electrical power and voltage produced by the generator is supplied to an electrical control unit which includes a combination of transformers, variable speed drives, soft starters such as star-delta starters, direct-on-line starters, and wound-rotor motors. The electrical control unit, in turn, provides electrical power to the pump motor. Such an electrical control unit may weight up to four tonne, and cost up to $300,000.

[0006] In order to maintain the motor condition the pump must be operated within a range of interdependent parameters. For a given pump speed, such as 40Hz, the pump curve for that pump will show the flow rate of the pump for a given pressure head. In a downhole operation both the pressure head and a desired flow rate are subject to change. Such changes can be accommodated by a change in the pump speed, within safe pump operating limits. This is typically achieved by the use of a variable speed drive within the electrical control unit.

[0007] The present invention seeks to avoid the use of a variable speed drive by instead providing direct control of the generator. In a preferred embodiment, this may eliminate the need for a separate electrical control unit.

[0008] For the avoidance of doubt, the term 'dewatering' as used herein is defined as the removal of groundwater from a borehole in order to lower the level of the local water table.

Summary of the Invention

[0009] According to one aspect of the present invention there is provided a power and control system for a dewatering submersible pump, the system including: a generator comprising an engine and an alternator, the engine having an Engine Control Unit (ECU), the alternator having a voltage regulator, the generator supplying electrical power to the pump; at least one sensor arranged to provide information regarding pump operation and/or surrounding conditions; and a system controller, the system controller being arranged to receive information from the sensor and to control the voltage regulator and the ECU, wherein the voltage regulator is an automatic voltage regulator.

[0010] The voltage regulator preferably provides an excitation voltage to the alternator in order to regulate output voltage of the alternator. The excitation voltage is arranged to vary in response to a comparison of measured output voltage of the alternator and a desired output voltage indicated by the system controller.

[0011] The sensor may be arranged to monitor the operation of a motor controlling the pump; to monitor the operation of the pump; to monitor the condition of fluid within a system connected to the pump; or to monitorexternal conditions.

[0012] In a preferred embodiment, at least one sensor is arranged to measure borehole water level.

[0013] It is also preferred that at least one sensor is arranged to measure a fluid flow rate within a pipe connected to an outlet of the pump.

[0014] It is further preferred that at least one sensor is arranged to measure fluid pressure within a pipe connected to an outlet of the pump.

[0015] According to a second aspect of the present invention there is provided a power and control system for a dewatering submersible pump, the system including: a generator comprising an engine and an alternator, the engine having an ECU, the alternator having a voltage regulator, the generator supplying electrical power to the pump; at least one sensor arranged to provide information regarding pump operation and/or surrounding conditions; and a system controller, the system controller being arranged to receive information from the sensor and to control the voltage regulator and the ECU, wherein the system controller is arranged to compare the information from the sensor to an input setpoint, and to control the voltage regulator and the ECU in response to deviation of the sensed information from the setpoint.

[0016] The setpoint may be one of the set of: desired water level in a bore; desired fluid flow rate within a pipe connected to an outlet of the pump; and desired pressure within a pipe connected to an outlet of the pump.

[0017] According to a third aspect of the present invention there is provided a method of controlling a dewatering submersible pump, the pump being powered by a generator having an engine and an alternator, the method including: monitoring at least one condition using a sensor; using a system controller to receive information from the sensor; using the system controller to control an ECU to in turn control an output frequency of the generator in response to information from the sensor; and using the system control to control an automatic voltage regulator to in turn control an output voltage of the generator in response to the sensed condition.

[0018] The condition(s) being monitored may be borehole water level and/or fluid conditions in a pipe connected to an outlet of the pump. These fluid conditions include fluid flow rate and fluid pressure.

[0019] The ECU and automatic voltage regulator are preferred operated to maintain pump speed within a recommended range. This may be between Hzand50Hzor60Hz.

Discussion of Prior Art

[0020] The applicant is not aware of similar power and control systems and methods used in dewatering. Patent searches have, however, revealed other power and control systems for submersible oil pumps.

[0021] US Patent Number 7170262 (Pettigrew) describes such a submersible oil pump. Rather than an automatic voltage regulator, Pettigrew uses an excitation controller which adjusts voltage according to the frequency of the engine-generator combination. Pettigrew does not suggest the use of sensors in order to inform the operation of the excitation controller, or to control for a desired setpoint.

[0022] International patent publication number W02015/051805 (Torrey) describes another submersible oil pump, with a control system arranged to regulate pump inlet pressure. Torrey also describes the use of pump sensors such as temperature and vibration. In one embodiment, Torrey describes the use of an exciter commanded by a system controller, however Torrey does not describe the use of an automatic voltage regulator. Torrey does not suggest the use of sensors monitoring either well level or conditions in connected piping, or the control for associated setpoints.

[0023] US Patent application publication 2014/0209289 (Boot) describes yet another submersible oil pump. As in Torrey, Boot suggests sensing operational characteristics within the pump, but not within connected piping. There is no suggestion of monitoring well level. Boot does not suggest the maintenance of setpoints.

Brief Description of the Drawings

[0024] It will be convenient to further describe the invention with reference to preferred embodiments of the present invention. Other embodiments are possible, and consequently the particularity of the following discussion is not to be understood as superseding the generality of the preceding description of the invention. In the drawings:

[0025] Figure 1 is a schematic view of a power and control system for a submersible pump in accordance with the present invention;

[0026] Figure 2 is a flow diagram for the control system of Figure 1; and

[0027] Figure 3 is an illustrative pump curve diagram as used in the control system of Figure 1.

Detailed Description of Preferred Embodiments

[0028] Referring to the Figures, there is shown a water bore 10 in which a submersible pump 12 has been lowered. The submersible pump 12 is powered by an electrical motor 14. A primary electrical cable 16 provides electrical power to the motor 14. An outlet pipe 18 carries water from the pump 12 to the surface.

[0029] A power and control unit 20 is located on the surface. The power and control unit 20 includes outer casing 22 which houses a generator 24 comprising an internal combustion engine 26 and an alternator 28. The generator 24 supplies electrical power to the primary electrical cable 16.

[0030] The power and control unit 20 includes a controller 30.

[0031] The controller 30 is arranged to manage an electronic Engine Control Unit (ECU) 32 and an Automatic Voltage Regulator (AVR) 34.

[0032] The AVR 34 regulates the voltage supplied via the primary electrical cable 16 to the motor 14. It achieves this by applying an excitation voltage to the alternator 28, and varying the excitation voltage in response to measured output of the alternator 28. The arrangement is such that the controller 30 provides an indication of desired output voltage to the AVR 34, and the AVR 34 constantly manages the excitation voltage in order to achieve the desired output voltage by means of a feedback loop.

[0033] The ECU 32 controls the speed and power of the engine 26, primarily through control of electronic fuel injectors. The controller 30 provides the ECU with a desired speed (i.e. frequency) and load for operation of the alternator 28 under the relevant conditions. The ECU 32 acts to maintain efficiency of the engine 26 through changing conditions. The ECU 32 actively controls the volume of fuel delivered per engine stroke by the fuel injectors to provide the required engine speed and torque.

[0034] A circuit breaker 36 is located electrically between the generator 24 and the primary electrical cable 16.

[0035] The controller 30 is connected to a plurality of sensors. A first sensor is located within the bore 10, and extends down to the pump 12. The first sensor 40 is arranged to detect and monitor the level of ground water within the bore 10.

[0036] The outlet pipe 18 is fluidly connected to a transport pipe 42. A second sensor 44 is mounted on the transport pipe 42. The second sensor is a flow meter, arranged to detect the flow rate of water passing through the transport pipe 42.

[0037] Two third sensors 46 are mounted at spaced locations along the transport pipe 42. The third sensors 46 are pressure sensors, arranged to detect pressure within the transport pipe 42.

[0038] A temperature sensor (not shown) is attached to the motor 14.

[0039] Operation of the controller 30 may be done directly via a human machine interface (HMI) 48, or may be done remotely via a network interface , arranged to communicate with an electronic network 52 and to be operated from a remote control centre 54.

[0040] Figure 3 shows atypical pump curve diagram for a submersible pump 12. The pump 12 has a maximum operating speed of 50Hz, and a minimum operating speed of 30Hz. At a given speed the pump curve 60 shows the relationship between head pressure generated and flow rate.

[0041] The present invention operates on the understanding that pump speed, flow rate, and pressure head together provide an interrelated three dimensional operation range for the pump 12.

[0042] Operation of the power and control system will now be described.

Start-up procedure

[0043] The circuit breaker 36 is closed prior to start-up.

[0044] The controller 30 sends a 'start-up' signal to the ECU 32 and to the engine 26. A starter motor (not shown) acts to start the engine 26, and bring it to idle. At this time the drive shaft of the engine 26 will turn a rotor of the alternator 28, however the AVR 34 will not supply an excitation voltage to the alternator 28.

[0045] When the engine 26 is idling correctly (typically about 10 seconds after starting) the controller 30 sends "soft-start" signal to the AVR The AVR 34 provides an excitation voltage to the alternator 28, causing the voltage supplied by the alternator 28 to the motor 14 to 'ramp' linearly from zero to

270V over a period of about 2 seconds. During this time the motor 14 accelerates from rest to a speed of about 33Hz. The controller 30 then sends signal to the AVR 34 indicating a desired output voltage (typically 415V). The AVR 34 adjusts its excitation voltage accordingly, as the motor accelerates up to its final required pump speed (typically about 50Hz). The ECU 32 acts concurrently to bring the engine 26 to a speed of about 1500RPM. It will be appreciated that the generator 24 now is producing 415V at about 50Hz.

[0046] It will be appreciated that references to pump speed assume a two pole motor 14, and are discounting any slip. Actual pump revolutions in this situation are likely to be in the order of 2900rpm.

[0047] Once the motor 14 is operating at its correct speed and the pump 12 has begun pumping water via the outlet pipe 18 to the transport pipe 42, an appropriate mode of operation can be selected.

Water-level maintenance mode

[0048] In this mode the key sensor is the first sensor 40, measuring the level of water in the bore 10. The level of ground water surrounding a bore 10 can be calculated using the baseline aquifer level, the porosity of the surrounding medium, the distance from the bore, and the level within the bore. As such, maintaining an appropriate level within the bore 10 provides certainty that the water level in the surrounding area will be below the required level. This appropriate level is input into the controller 30 as a setpoint.

[0049] In water-level maintenance mode, the pump 12 is operated at its full speed (e.g. 50Hz) to achieve maximum possible flow rate until the water level in the bore reaches the setpoint. Once the setpoint has been reached, the controller 30 operates a feedback loop between the engine speed governed by the ECU 32 (operated in conjunction with excitation voltage of the AVR 34) and the measured water level of the first sensor 40 until a steady state is reached. It will be appreciated that the steady state must be within the system capacity (including within safe pump speeds and system pressures) otherwise an alarm will activate and the pump 12 will be shut down. In a preferred embodiment, the feedback loop employs Proportional Integral Derivative (PID) control.

[0050] The controller 30 will continue to operate the feedback loop in the event that there is a change in surrounding conditions.

Constant flow rate mode

[0051] In this mode the key sensor is the second sensor 44, measuring the flow rate through the transport pipe 42. Water being extracted from the bore can be used in many applications, some of which (for instance, use as process water within ore processing operations) require a constant flow rate of water. This flow rate is input into the controller 30 as a set point.

[0052] Inconstant flow rate mode, the controller 30 operates a feedback loop between the engine speed governed by the ECU 32 (operated in conjunction with excitation voltage of the AVR 34) and the measured water flow past the second sensor 44 until a steady state is reached. In a preferred embodiment, the feedback loop employs PID control. It will be appreciated that the steady state must be within the system capacity (including within safe pump speeds and systems pressures temps) otherwise an alarm will activate and the pump 12 will be shut down.

[0053] The controller 30 will continue to operate the feedback loop in the event that there is a change in surrounding conditions.

[0054] Figure 3 shows usage of the pump curve diagram in constant flow rate mode. As head pressure changes from 230m to 90m (for instance, different valves are opened or closed downstream, or in response to changes in bore water level), the pump speed is changed from 50Hz to 35Hz while maintaining a flow rate of 301/s.

Constant pressure mode

[0055] In this mode the key sensors are the third sensors 46, measuring the pressure in the transport pipe 42. Water being extracted from the bore 10 can be used in many applications, some of which (for instance, dust suppression and tank filling via a pressure valve) may require a constant water pressure. This pressure is input into the controller 30 as a set point.

[0056] In constant pressure mode, the controller 30 operates a feedback loop between the engine speed governed by the ECU 32 (operated in conjunction with excitation voltage of the AVR 34) and the measured water pressure at the third sensors 46 until a steady state is reached. In a preferred embodiment, the feedback loop employs PID control. It will be appreciated that the steady state must be within the system capacity (including within safe pump speeds) otherwise an alarm will activate and the pump 12 will be shut down.

[0057] The controller 30 will continue to operate the feedback loop in the event that there is a change in surrounding conditions.

System operating safeguards

[0058] The controller 30 includes a plurality of thresholds within which the system must operate, including current draw, pump speed, system pressure, bore water level, motor temperature, and minimum flow rate. The controller is arranged to activate an alarm and, if necessary, shut down the system should any of the thresholds be breached.

[0059] Typical thresholds include a motor speed of 30Hz to 50Hz or 60Hz, a bore water level sufficiently above the pump 12, and a motor temperature below 65°C or 70°C. Thresholds such as minimum flow rate are specific to particular pump/motor combinations.

[0060] In order to provide sufficient electrical power, in a preferred embodiment the generator 24 is sized to be able to provide power in the order of 125% to 333% of the kW rating of the motor 14.

[0061] It will be appreciated that the system controller 30 is preferably a microprocessor and/or microcontroller based system programmed with appropriate algorithms to generate the feedback loops as discussed above.

[0062] The instructions provided by the controller 30 to the ECU 32 and AVR 34 may be control signals (e.g. a reference voltage, an analogue signal, a digital signal etc.) and/or logical instructions (e.g. machine code, packetized data, etc.).

[0063] The HMI 48 is a physical interface electronically coupled to the controller 30. The HMI 48 includes output means, such as a display, speaker and/or printer; and input means, such as a keypad, keyboard, touch screen, touch pad and the like. The HMI 48 provides the ability to control the system controller 30 locally, that is, by a user physically located in the vicinity of the power and control unit 20.

[0064] The network interface 50 provides network access to and from the system controller 30. In a preferred embodiment, the network interface 50 is a cellular modem compatible with 3G/4G, LTE, EDGE, HSPA, CDMA or other mobile communications protocol. The network interface 50 may additionally or alternatively be a wi-fi, ethernet, cable, ADSL/DSL and/or BluetoothTM interface. The network interface 50 connects the controller 30 to the network 52, which may be the Internet or other LAN or WAN, and thereby to the remote control centre 54.

[0065] The remote control centre 54 is and/or includes a device (e.g. computer, laptop, smartphone, tablet, etc.) operable to generate and transmit instructions to the system controller 30.

[0066] It will be appreciated that the methods described above essentially allow the power and control unit 20 to provide the function of a variable speed drive (VSD), thereby removing the need for a dedicated VSD and hence the additional capital and operating expenditures associated with having a VSD coupled to a fixed speed generator.

[0067] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention. For instance, in some circumstances it may be preferable to include a transformer located electrically between the alternator 28 and the motor 14. It will be noted that Figure 2 indicates that the generator 24 may power a plurality of motors 14. It will also be appreciated that further sensors may be employed, for instance measuring operating temperatures, currents and voltages, and/or operating speeds.

Claims

Claims 1. A power and control system when used for a dewatering submersible pump, the system including: a generator comprising an engine and an alternator, the engine having an Engine Control Unit (ECU), the alternator having a voltage regulator, the generator supplying electrical power to the pump; at least one sensor arranged to provide information regarding pump operation and/or surrounding conditions; and a system controller, the system controller being arranged to receive information from the sensor and to control the voltage regulator and the ECU based on the received information, wherein the voltage regulator is an automatic voltage regulator, wherein the ECU is controlled to govern the speed of the engine and thus the frequency of the electrical power supplied to the pump, and the voltage regulator is controlled to govern the voltage of the electrical power supplied to the pump, and wherein the sensor is arranged to measure borehole water level.
2. A power and control system when used for a dewatering submersible pump, the system including: a generator comprising an engine and an alternator, the engine having an ECU, the alternator having a voltage regulator, the generator supplying electrical power to the pump; at least one sensor arranged to measure borehole water level; and a system controller, the system controller being arranged to receive information from the sensor and to control the voltage regulator and the ECU, wherein the system controller is arranged to compare the information from the sensor to an input setpoint, and to control the voltage regulator and the ECU in response to deviation of the sensed information from the setpoint.
3. A power and control system when used for a dewatering submersible pump as claimed in claim 3, wherein the setpoint is desired water level in a bore.
4. A method of controlling a dewatering submersible pump, the pump being powered by a generator having an engine and an alternator, the method including: monitoring borehole water level using a sensor; using a system controller to receive information from the sensor, using the system controller to control an ECU to in turn control an output frequency of the generator in response to the information from the sensor; and using the system controller to control an automatic voltage regulator to in turn control an output voltage of the generator in response to the borehole water level.

LAA INDUSTRIES PTY LTD By its Patent Attorneys ARMOUR IP

P2385AU00