AU2022271456A1

AU2022271456A1 - Control of submersible pumps powered via renewable energy sources

Info

Publication number: AU2022271456A1
Application number: AU2022271456A
Authority: AU
Inventors: Mark Vincent Keogh; Jennifer Reid; James Harold Waterreus
Original assignee: UON Pty Ltd
Current assignee: UON Pty Ltd
Priority date: 2021-11-17
Filing date: 2022-11-17
Publication date: 2023-06-01
Also published as: AU2022271455B1

Abstract

A power and control system for a submersible pump is disclosed. The system includes a generator, a photo voltaic array, a battery, and a Variable Speed Drive (VSD). The photo voltaic array, the battery and the VSD are all connected by a DC bus, such that the VSD receives DC power as an input and outputs AC power to the submersible pump. 4/4 START No Yes No Yes Is Genset No C>10 Yes ON? No Yes SoC > 15% Start Generator BS ospl Operate Changeover Switch No Yes Generate Generator to supply (N e No oC<10 Yes Fig. 5

Description

4/4

START

No Yes

No Yes Is Genset No C>10 Yes ON?

No Yes SoC > 15% Start Generator BS ospl

Operate Changeover Switch No Yes Generate

Generator to supply (N e

No oC<10 Yes

Fig. 5

AUSTRALIA

Patents Act 1990

COMPLETE SPECIFICATION

Invention title:

"CONTROL OF SUBMERSIBLE PUMPS POWERED VIA RENEWABLE ENERGY SOURCES"

Applicant:

UON PTY LTD

Associated provisional applications: Application number 2021903705

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

"CONTROL OF SUBMERSIBLE PUMPS POWERED VIA RENEWABLE ENERGY SOURCES"

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 with at least some power coming from renewable energy sources. The invention has been developed for use in applications where mains power supply is not available. In addition to mining, the invention is anticipated to have application in other industries such as the use of ground water in agriculture.

Background to the Invention

[0002] Mining operations frequently occur below the local water table. In such operations, it is necessary to lower the local ground water level 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 bore, thus lowering the immediately surrounding water table.

[0003] Submersible pumps used in dewatering are typically centrifugal pumps driven by an electrically powered AC induction motor or a permanent magnet synchronous motor. In a typical installation the motor may be between 7.5kW and 500kW in power, running at between 30Hz and 60Hz. It will be appreciated that higher powered motors may be used in particular situations.

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

[0005] There has been limited development of power systems which incorporate photovoltaic (PV) cells into their operation. These systems can typically operate under either full generator power or full PV power, but not both simultaneously.

[0006] Such systems are frequently incapable of providing an uninterruptable power supply, which is highly desirable for operating a dewatering pump. Switching between states of operation is often associated with a temporary suspension in pumping operations.

[0007] For this reason, in situations where constant pump operation is required the use of renewable energy sources has been considered problematic.

[0008] In addition, traditional PV powered systems can only operate when there is sufficient solar radiation to power the pump. This usually requires a clear sky, and a limited time period during daylight hours.

[0009] It is common for submersible pumps used in dewatering to be controlled to maintain a desired setpoint, generally chosen from the set of: bore water level; output flow rate; and output pressure. This has traditionally been achieved by the use of a Variable Speed Drive (VSD). The VSD receives as its input a constant voltage, constant frequency alternating current (either from a fixed-speed generator or from an inverter connected to a PV system), and outputs an alternating current at a voltage and frequency required for the submersible pump to maintain its setpoint. An example of such as system is disclosed in Australian patent number 2021106106, the contents of which are incorporated herein by reference.

[0010] Australian patent number 2021107164, the contents of which are incorporated herein by reference, describes the use of a variable speed generator which can be controlled to power a submersible pump in such a way as to avoid the use of a VSD.

[0011] The present invention seeks provide a system which can incorporate a variable speed generator alongside a renewable energy source.

Summary of the Invention

[0012] According to one aspect of the present invention there is provided a power and control system arranged for powering a submersible pump or pumps, the system including: a first source of electricity; a renewable energy collector; a battery; a variable speed drive (VSD) arranged to receive direct current from the renewable energy collector and/or the battery, the VSD arranged to output alternating current; at least one sensor arranged to provide information regarding pump operation and/or surrounding conditions including information about at least one measured parameter of pump operation and/or surrounding conditions; and a system controller, the system controller being arranged to receive information from the sensor, the system controller being arranged to receive information regarding a desired setpoint for the parameter measured by the sensor; the system controller being arranged to direct electrical power to the submersible pump(s), the system controller arranged to determine available electrical power from the renewable energy collector and from the battery, the system controller arranged to selectively engage or disengage the first source of electricity in response to predetermined levels of available power, wherein the system controller controls the voltage and frequency output by the VSD based on a comparison between the received information from the sensor and the desired setpoint so as to maintain the parameter at the desired setpoint.

[0013] Advantageously, the power and control system is able to use direct current generated by the renewable energy collector without requiring inverter(s) directly connected to the renewably energy collector.

[0014] The submersible pump or pumps are preferably used for dewatering purposes.

[0015] The first source of electricity may be in a generator. In an alternative embodiment, the first source of electricity may be mains power.

[0016] It is preferred that the generator is a variable speed generator having a voltage and frequency output which is controllable by the system controller. In this embodiment the controller may control the VSD to output no current when the generator is engaged.

[0017] Alternatively, the generator may be arranged to selectively supply power to the VSD.

[0018] Preferably the renewable energy collector is an array of photovoltaic (PV) cells. Alternatively, the renewable energy collector may include wind turbines or means of collecting some other renewable energy source.

[0019] In a preferred embodiment the system includes a DC bus between the battery and the VSD. A DC/DC converter is located between the renewable energy collector and the DC bus. The DC/DC converter acts to convert the voltage generated by the renewable energy collector to match the voltage of the battery.

[0020] It will be appreciated that the voltage of the battery may be variable depending on the state of battery charge. The DC/DC converter is arranged to convert the variable input (based on voltage of the PV array) to match the varying output (the DC bus voltage set by the battery). The DC/DC converter may include a Maximum Power Point Tracker (MPPT) which acts to set the input voltage in order to optimise the PV array. The DC/DC converter may also include two inputs arranged to receive different voltages (for instance, from PC arrays oriented in different directions) and be arranged to combine these into a single output.

[0021] Preferably the generator is diesel powered.

[0022] It is preferred that the system has at least three operating states: a 'Generator-only' operating state where all electrical power directed to the pump(s) is drawn from the generator; a 'PV-only' operating state where all electrical power directed to the pump(s) is drawn from the renewable energy collector; and a 'battery drawdown' operating state where at least some electrical power directed to the pump(s) is drawn from the battery.

[0023] The PV-only operating state is preferably arranged such that excess power generated by the renewable energy collector beyond that required by the pump(s) is directed into the battery, and acts to charge the battery. The DC/DC converter may be arranged to cease the supply of power into the battery in the event that the battery is fully charged.

[0024] The system controller may be arranged to place the system into a Generator-only operating state if the state of charge of the battery decreases below a primary battery threshold. The system controller may use a primary battery threshold being a state of charge between 5% and 20%. In a preferred embodiment, the system controller uses a primary battery threshold being a state of charge of about 10%.

[0025] The system controller may be arranged to place the system into a PV-only operating state if two conditions are met simultaneously: the power generated by the renewal energy collector exceeds the power required by the pump(s); and the state of charge of the battery is above a secondary threshold. The system controller may use a second battery threshold being a state of charge between 10% and 40%. In a preferred embodiment, the system controller uses a secondary battery threshold being a state of charge of about 15%.

Brief Description of the Drawings

[0026] 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:

[0027] Figure 1 is a schematic diagram of an energy providing system in accordance with a first embodiment of the present invention, shown when the system is operating in PV-only operating state;

[0028] Figure 2 is a schematic diagram of an energy providing system in accordance with a second embodiment of the present invention, shown when the system is operating in PV-only operating state

[0029] Figure 3 is a schematic diagram of a PV/battery powered pump operating system as previously used by the applicant;

[0030] Figure 4 is a schematic diagram of a PV/battery powered pump operating system in accordance with the present invention; and

[0031] Figure 5 is a flow-chart showing the mode-switching decision pathway used within the energy providing system of Figure 1.

Detailed Description of Preferred Embodiments

[0032] Referring to the Figures, Figure 1 shows a schematic arrangement of a system 10 for providing power to a submersible pump 12. It will be understood that although the diagram shows a single pump 12, it is possible for the system to be concurrently powering a plurality of pumps 12. The pump(s) 12 is located within a water bore.

[0033] The pump 12 is arranged to be controlled to maintain a setpoint, typically taken from the set of bore level, water flow rate, or output water pressure.

[0034] Power is supplied to the pump 12 by either a variable speed generator 14 as described in Australian Patent Number 2021107164, or else by means of a Variable Speed Drive (VSD) 16. A first switch 18 is arranged to selectively connect or disconnect the generator 14 from the pump 12. A second switch 20 is arranged to selectively connect or disconnect the VSD 16 from the pump 12. The first switch 18 and the second switch 20 are mechanically and electrically interlocked such that only one of the first and second switches can be closed at any one time. In the position shown in Figure 1 the first switch 18 is open and the second switch 20 is closed.

[0035] The system 10 includes a renewable energy collector. In the embodiment shown the renewable energy collector consists of a photovoltaic cell (PV) array 22. The PV array 22 is arranged to provide solar energy as a direct current to a DC/DC converter 24.

[0036] The system 10 further includes a battery management system (BMS) 26 associated with a set of batteries 28. The BMS 26 is arranged to connect to a DC bus 30.

[0037] The DC bus 30 is connected additionally to an output of the DC/DC converter 24, in addition to the VSD 16.

[0038] The system includes a system controller being a Programmable Logic Controller (PLC) 32. The PLC 32 is programmed to receive information regarding the output of the PV array 22 and the storage level of the BMS 26, in addition to information from sensors arranged to measure system outputs such as bore level, water flow rate, and output water pressure. The PLC 32 is programmed to supply control signals to the VSD 16 and the generator 14. The flow of signals to and from the PLC 32 is shown in Figure 1 in phantom lines.

[0039] The system 10 is arranged to operate in a number of different operating states.

PV-only operating state

[0040] Figure 1 shows the system 10 operating in a first operating state known as PV-only operating state. In PV-only operating state the amount of power being supplied via the PV array 22 equals or exceeds that demanded by the VSD 16 to drive the pump(s) 12. In this operating state the first switch 18 is open and the generator 14 is stopped.

[0041] The PLC 32 sends a signal to the VSD 16 indicating a required frequency and voltage required to maintain the desired setpoint for pump 12 control. The VSD 16 converts a direct current obtained via the DC bus 30 into the required alternating current (frequency and voltage) needed to operate the pump at the speed required to maintain the desired setpoint.

[0042] Additional electrical power being produced by the PV array 22 is supplied via the DC bus 30 to the BMS 26, and acts to charge the batteries 28. It will be appreciated that the voltage of the DC bus 30 is determined by the BMS 26 and, in practice, varies according to the state of charge of the batteries 28. In a prototype of the invention created for testing, the voltage at the BMS 26 varies between 660V when the batteries 28 are empty and 792V when the batteries 28 are fully charged.

[0043] The DC/DC converter 24 is arranged to convert the variable direct current received from the PV array 22 to a direct current at the voltage of the DC bus 30. It does this by use of a maximum power point tracker (MPPT) which finds the optimal voltage point of the PV array 22 as known in the art.

[0044] It will be appreciated that multiple PV arrays 22 may be used, for instance an East-facing array and a West-facing array. The DC/DC converter 24 may be arranged to receive direct currents having different voltages and to combine them into a single output direct current at the DC bus 30 voltage.

[0045] If the batteries 28 are fully charged, the DC/DC converter 24 is controlled by the PLC 32 to limit the flow of energy into the DC bus 30.

Battery drawdown operating state

[0046] When the PV array 22 ceases to produce sufficient power to drive the pump 12, the PLC 32 will switch the system 10 to a second operating state known as battery drawdown operating state. In this state the VSD 16 continues to output the alternating current required to maintain operation of the pump 12. Its power input is drawn primarily from the DC/DC converter 24, with additional power being supplied by the BMS 26. As the amount of power provided by the PV array 22 diminishes (for instance, as the sun sets) an increasingly greater proportion of power will be supplied by the BMS 26, up until the point where the power required by the VSD 16 to drive the pump(s) 12 is fully supplied by the BMS 26. In this operating state the first switch 18 is open and the generator 14 is stopped.

Generator-only operating state

[0047] In a third operating state known as Generator-only operating state the first switch 18 is closed and the second switch 20 is opened. In this state the generator 14 is operational, with output frequency and voltage controlled by the PLC 32 to meet the requirements of the pump 12 as described in Australian Patent Number 2021107164.

Operating state switching

[0048] The system controller is arranged to switch between the three operating states discussed above based on various measured operating parameters. In general, the switching between operating states happens at similar times during a day, based on sunrise and sunset times. A flowchart detailing the switching is shown in Figure 5.

[0049] If the PV array 22 is not producing sufficient power to operate the pump(s) 12, the PLC 32 checks for the state of charge of the BMS 26. If this is below a primary battery threshold of 10%, the system is held in Generator only operating state.

[0050] Once the PV array 22 begins to generate sufficient power, the PLC 32 monitors the state of charge of the batteries 28 via the BMS 26. Once this reaches a secondary battery threshold (which is 15% in the embodiment of Figure 5) the PLC 32 switches the system to PV-only operating state. It does this by opening the first switch 18 and closing the second switch 20 (in practice, these switches are incorporated into a changeover switch) and then stopping the generator 14.

[0051] When the power being supplied by the PV array 22 drops below that required by the pump 12, the PLC 32 checks that the state of charge of the batteries 28 is above the primary threshold, and then switches to battery drawdown operating state. While in this state, the PLC 32 continues to monitor the state of charge of the batteries 28.

[0052] When the state of charge of the batteries 28 drops below the primary threshold, the PLC 32 switches the system to Generator-only mode. It does this by starting the generator 14, and then when the generator is up to speed and synchronised with the VSD 16 it opens the second switch 20 and closes the first switch 18.

Alternative embodiment

[0053] An alternative embodiment of the present invention is shown in Figure 2. Figure 2 shows a schematic arrangement of an alternative system for providing power to the submersible pump 12. Much of the alternative embodiment is identical to the first embodiment described, and like numerals in Figures 1 and 2 represent corresponding features. In the alternative embodiment the variable speed generator 14 of Figure 1 is replaced with a fixed speed generator 42. In this embodiment the VSD 16 is permanently connected to the pump 12, with the VSD 16 able to be switched between two inputs: a direct current input 44 supplied by the DC bus 30 and an alternating current input 46 supplied by the generator 42. It will be appreciated that the first switch 18 is connected to the alternating current input 46 and the second switch 20 is connected to the direct current input 44.

[0054] Where mains power 48 may be available, the supply of alternating current to the first switch 18 may be direct from available mains power, rather then through used of the fixed speed generator 42.

Discussion of prior art

[0055] Figures 3 and 4 show a representation of a key difference between the present invention and that previously employed by the applicant.

[0056] Figure 3 shows a traditional arrangement of a PV array 22 which is connected to a first DC/AC inverter 50. The first DC/AC inverter 50 supplies alternating current to the VSD 16. The VSD 16 uses AC-DC conversion 52 followed by DC-AC 54 conversion to provide the required alternating current frequency and voltage for the pump 12. This is a known operating system.

[0057] The applicant has previously adapted this system to incorporate battery storage using batteries 28. This previous system uses a second DC/AC inverter 56 to supply alternating current to the VSD 16.

[0058] The present invention is shown by way of contrast in Figure 4. The present invention avoids the use of inverters by instead supplying direct current to the VSD 16. The only conversion to alternating current occurs within the VSD, where direct current is converted into the required alternating current frequency and voltage for the pump 12.

[0059] Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims

Claims 1. A power and control system arranged for powering a submersible pump or pumps, the system including: a first source of electricity; a renewable energy collector; a battery; a variable speed drive (VSD) arranged to receive direct current from the renewable energy collector and/or the battery, the VSD arranged to output alternating current; at least one sensor arranged to provide information regarding pump operation and/or surrounding conditions including information about at least one measured parameter of pump operation and/or surrounding conditions; and a system controller, the system controller being arranged to receive information from the sensor, the system controller being arranged to receive information regarding a desired setpoint for the parameter measured by the sensor; the system controller being arranged to direct electrical power to the submersible pump(s), the system controller arranged to determine available electrical power from the renewable energy collector and from the battery, the system controller arranged to selectively engage or disengage the first source of electricity in response to predetermined levels of available power, wherein the system controller controls the voltage and frequency output by the VSD based on a comparison between the received information from the sensor and the desired setpoint so as to maintain the parameter at the desired setpoint.
2. A power and control system arranged for powering a submersible pump or pumps as claimed in claim 1, whereby the submersible pump or pumps are used for dewatering purposes.
3. A power and control system as claimed in claim 1 or claim 2, wherein the first source of electricity is a generator.
4. A power and control system as claimed in claim 3, wherein the generator is a variable speed generator having a voltage and frequency output which is controllable by the system controller.
5. A power and control system as claimed in claim 4, wherein the controller controls the VSD to output no current when the generator is engaged.
6. A power and control system as claimed in claim 3, wherein the generator is arranged to selectively supply power to the VSD.
7. A power and control system as claimed in any preceding claim, wherein the renewable energy collector is an array of photovoltaic (PV) cells.
8. A power and control system as claimed in any preceding claim, wherein the system includes a DC bus between the battery and the VSD.
9. A power and control system as claimed in claim 8, wherein a DC/DC converter is located between the renewable energy collector and the DC bus.
10. A power and control system as claimed in claim 9, wherein the DC/DC converter acts to convert the voltage generated by the renewable energy collector to match the voltage of the battery.
11. A power and control system as claimed in claim 10, wherein the DC/DC converter includes a Maximum Power Point Tracker (MPPT) which acts to set the input voltage in order to optimise the PV array.
12. A power and control system as claimed in any one of claims 9 to 11, wherein the DC/DC converter includes two inputs arranged to receive different voltages and is arranged to combine these into a single output.
13. A power and control system as claimed in any preceding claim, wherein the system has at least three operating states: a 'Generator-only' operating state where all electrical power directed to the pump(s) is drawn from the first source of electricity; a 'PV-only' operating state where all electrical power directed to the pump(s) is drawn from the renewable energy collector; and a 'battery drawdown' operating state where at least some electrical power directed to the pump(s) is drawn from the battery.
14. A power and control system as claimed in claim 13, whereby the PV only operating state is arranged such that excess power generated by the renewable energy collector beyond that required by the pump(s) is directed into the battery, and acts to charge the battery.
15. A power and control system as claimed in claim 13 or claim 14, wherein the system controller is arranged to place the system into a Generator-only operating state if the state of charge of the battery decreases below a primary battery threshold.
16. A power and control system as claimed in claim 15 wherein the primary battery threshold is a state of charge between 5% and 20%.
17. A power and control system as claimed in claim 16, wherein the primary battery threshold is state of charge of about 10%.
18. A power and control system as claimed in any one of claims 13 to 17, wherein the system controller is arranged to place the system into a PV-only operating state if two conditions are met simultaneously: the power generated by the renewal energy collector exceeds the power required by the pump(s); and the state of charge of the battery is above a secondary threshold.
19. A power and control system as claimed in claim 18 wherein the secondary battery threshold is a state of charge between 5% and 20%.
20. A power and control system as claimed in claim 19, wherein the secondary battery threshold is state of charge of about 15%.

UON PTY LTD By its Patent Attorneys ARMOUR IP

P2459AU02