AU2020201449B2

AU2020201449B2 - Control system

Info

Publication number: AU2020201449B2
Application number: AU2020201449A
Authority: AU
Inventors: Lachlan Sharpe
Original assignee: Pacific Blue Vic Pty Ltd
Current assignee: Pacific Blue Vic Pty Ltd
Priority date: 2019-06-06
Filing date: 2020-02-27
Publication date: 2022-01-13
Anticipated expiration: 2039-09-24
Also published as: AU2021107655C4; AU2019101451A4; AU2019101451B4; AU2021107655B4; AU2021107655A4; AU2020201449A1; AU2019236622B1; AU2022202421A1

Abstract

A control system for an electric pump, comprising an input and an output electrically connectable to, respectively, a power source and the electric pump and a controller configured to cause variable electrical power to be supplied to an AC motor of the electric pump via the output and thereby control a rotational speed of the AC motor. The controller is connectable to a user control device and is selectively switchable between first and second motor operating modes using the user control device, wherein for the first of the motor operating modes the AC motor is a synchronous AC motor and for the second of the motor operating modes the AC motor is an asynchronous AC motor. The control system also comprises a storage device coupled to the controller that stores at least one set point relating to an operating environment of the electric pump. The controller is further configured such that in response to receiving signals from one or more pump operating sensors, the controller automatically varies the rotational speed of the AC motor to thereby maintain the set point. 1/6 0 )00 I pI * C N * 0 (NI I CD U )-- -- -- - -- - - 0D,1

Description

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CONTROL SYSTEM

Field

[0001] The present invention relates to electrical engineering and, more particularly, a control system for electric pumps.

Background

[0002] Electric pumps of various configurations are used in industry to move and control the flow of liquids. For example, electric submersible pumps (ESPs) are designed to be fully submerged in liquid and can be used for pumping drainage, sewage and slurry. In the oil and gas industry, ESPs are deployed down well bores and used to bring pumping production fluids to the ground surface. At mining and construction sites, ESPs may be used to remove and control excess ground or surface water, a process known as dewatering.

[0003] An ESP typically comprises an alternating current (AC) electric motor hermetically sealed within the pump body that operatively drives a mechanical pump assembly. The pump assembly may comprise a centrifugal or positive displacement pump and the AC motor is commonly an induction motor or similar asynchronous AC motor. Electrical power is supplied to the ESP via cable from a power and control system installed above ground. In remote locations, the power and control system may comprise a prime mover, such as an internal combustion engine or gas turbine, mechanically coupled to an electrical generator.

[0004] Induction motors are used for many ESPs because they are advantageously simple in construction, mechanically robust and economical to manufacture. Induction motors do, however, suffer from various shortfalls. For example, under low load conditions an induction motor only produces modest power. The rotational speed of an induction motor is also difficult to control. This is, in part, due to the slip that inherently occurs between the rotational speed of the stator's magnetic field and mechanical rotation of the rotor.

[0005] Some electric pumps are, therefore, operatively driven by synchronous AC motors, such as brushless permanent magnet motors, reluctance motors or hysteresis motors. For ESPs, permanent magnet AC motors may be used because they provide improved power efficiencies and incur less heat losses than induction motors in many pump operating conditions.

[0006] In major engineering and resources projects, ESPs often need to be deployed for long periods of time and their electric motors may need to be maintained or replaced on several occasions. The motor may wear out or it may need to be replaced with a different model that can deliver the necessary power to deal with increasingly demanding conditions at the well bore, such as increased water pressure or flow. For example, if the ESP is equipped with an asynchronous AC motor, in certain cases it may be beneficial to remove and replace it with a more efficient and responsive synchronous AC motor. Similarly, if the ESP is equipped with a synchronous AC motor that has worn out, due to budgetary constraints an induction or similar asynchronous AC motor may need to be installed in its place.

[0007] In order to swap between a synchronous and an asynchronous motor, the power and control system that supplies power to the ESP must also be swapped out and replaced with one that can provide the necessary power and control signals to drive the new motor correctly. If the required system is not readily available, this can lead to project delays. If the system needs to be procured, this can add a significant expense to the project.

[0008] It is against this background that the present invention has been developed.

Summary

[0009] According to the present invention, there is provided a control system for an electric pump, the control system comprising: an input and an output electrically connectable to, respectively, a power source and the electric pump; a controller configured to cause variable electrical power to be supplied to an AC motor of the electric pump via the output and thereby control a rotational speed of the AC motor, wherein the controller is connectable to a user control device and is selectively switchable between first and second motor operating modes using the user control device, wherein for the first of the motor operating modes the AC motor is a synchronous AC motor and for the second of the motor operating modes the AC motor is an asynchronous AC motor; and a storage device coupled to the controller that stores at least one set point relating to an operating environment of the electric pump, wherein the controller is further configured such that in response to receiving signals from one or more pump operating sensors, the controller automatically varies the rotational speed of the AC motor to thereby maintain the set point.

[0010] The controller may be configured such that the set point maintained by the controller is either: a constant fluid flow rate and the controller increases or decreases the rotational speed of the AC motor when the signals indicate that a fluid flow rate in the operating environment is, respectively, less than or more than the constant fluid flow rate; a constant fluid pressure and the controller increases or decreases the rotational speed of the AC motor when the signals indicate that a fluid pressure in the operating environment is, respectively, less than or more than the constant fluid pressure; or a constant fluid level and the controller increases or decreases the rotational speed of the AC motor when the signals indicate that a fluid level in the operating environment is, respectively, more than or less than the constant fluid level.

[0011] In the first of the motor operating modes, the synchronous AC motor may be a brushless permanent magnet AC motor.

[0012] The controller may be configured to control a frequency of alternating current supplied to the brushless permanent magnet AC motor via the output and thereby control a synchronous rotational speed of a rotor of the brushless permanent magnet AC motor in response to feedback received by the controller from one or more rotor sensors tracking a position of the rotor.

[0013] The controller may be further configured to cause the rotor to accelerate to synchronous rotational speed during a start up phase of the brushless permanent magnet AC motor.

[0014] In the second of the motor operating modes, the asynchronous AC motor may be an induction motor.

[0015] The controller may be configured to allow for slip of the induction motor when controlling a rotational speed of a rotor of the induction motor.

[0016] The control system may be configured such that poly-phase electrical power is supplied to the induction motor via the output.

[0017] The control system may be configured such that three phase electrical power is supplied to the induction motor via the output.

[0018] The output may be electrically connectable to the induction motor using a star or delta configuration for supplying the three phase electrical power.

[0019] The controller may be remotely connectable to the user control device via a computer network.

[0020] The controller may be further configured to vary the rotational speed of the AC motor in response to feedback received from one or more sensors measuring operating conditions of one or more components comprised in or connected to the electric pump.

[0021] The sensors may comprise a temperature sensor for measuring an operating temperature of the electric pump.

[0022] The control system may further comprise a variable speed drive connected to the input, wherein the control system causes the variable speed drive to vary AC electrical power received via the input and supplied to the AC motor via the output.

[0023] The variable speed drive may be a variable frequency drive and the control system may further comprise a harmonic filter electrically connected to the variable frequency drive for reducing harmonics in the AC electrical power supplied to the AC motor via the output.

[0024] The present invention also provides a power and control system for an electric pump, comprising: a variable speed genset; an output electrically connectable to the electric pump; a controller configured to cause variable electrical power to be supplied from the variable speed genset to an AC motor of the electric pump via the output and thereby control a rotational speed of the AC motor, wherein the controller is connectable to a user control device and is selectively switchable between first and second motor operating modes using the user control device, wherein for the first of the motor operating modes the AC motor is a synchronous AC motor and for the second of the motor operating modes the AC motor is an asynchronous AC motor; and a storage device coupled to the controller that stores at least one set point relating to an operating environment of the electric pump, wherein the controller is further configured such that in response to receiving signals from one or more pump operating sensors, the controller automatically varies the rotational speed of the AC motor to thereby maintain the set point.

[0025] The controller of the power and control system may be configured such that the set point maintained by the controller is either: a constant fluid flow rate and the controller increases or decreases the rotational speed of the AC motor when the signals indicate that a fluid flow rate in the operating environment is, respectively, less than or more than the constant fluid flow rate; a constant fluid pressure and the controller increases or decreases the rotational speed of the AC motor when the signals indicate that a fluid pressure in the operating environment is, respectively, less than or more than the constant fluid pressure; or a constant fluid level and the controller increases or decreases the rotational speed of the AC motor when the signals indicate that a fluid level in the operating environment is, respectively, more than or less than the constant fluid level.

[0026] The genset may comprise an alternator mechanically coupled to an engine, the engine comprising a throttle assembly, and wherein the controller is configured to operate the throttle assembly to control a speed of the engine and electrical power generated by the alternator.

[0027] The alternator may comprise a voltage regulator operated by the controller to control an output voltage of the alternator.

[0028] The present invention also provides a master control system for a plurality of electric pumps, wherein each of the electric pumps is powered and controlled by the control system as described above, wherein the controller of the control system is: in communication with the master controller system; and configured to transmit data relating to the operation of the control system and/or the electric pump to the master control system.

Brief Description of Drawings

[0029] 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 representation of a control system for an electric pump according to an example embodiment of the invention; Figures 2(a) and 2(b) are cross sectional schematic representations of, respectively, a brushless permanent magnet AC motor and an AC induction motor; Figure 3 is a schematic representation of the control system with a variable speed drive; Figure 4 is a schematic representation of the control system with a variable speed genset; Figures 5(a) and 5(b) are schematic representations of control systems connected to electric pumps according to example embodiments of the invention; and Figure 6 is a schematic representation of a master control system for a plurality of electric pumps according to a further example embodiment of the invention.

Description of Embodiments

[0030] Referring to Figure 1, an example embodiment of the present invention provides a control system 10 for an electric pump 12. The control system 10 comprises an input 14 and an output 16 electrically connectable to, respectively, a power source 18 and the electric pump 12. The control system 10 also comprises a controller 20 configured to cause variable electrical power to be supplied to an AC motor 22 of the electric pump 12 via the output 16 and thereby control a rotational speed of the AC motor 22. The controller 20 is selectively switchable between first and second motor operating modes, wherein in the first of the motor operating modes the AC motor 22 is a synchronous AC motor and in the second of the motor operating modes the AC motor 22 is an asynchronous AC motor.

[0031] The control system 10 also comprises a storage device 24 coupled to the controller 20 that stores at least one set point relating to an operating environment of the electric pump 12, wherein the set point is either a constant fluid flow rate, a constant fluid pressure or a constant fluid level relating to the environment in which the electric pump 12 is operating that is to be maintained by the control system 10 during use. The control system 10 also comprises a communications interface 26 for connecting the controller 20 to a user control device 28. The controller 20 is further configured such that (a) in response to receiving a signal from the user control device 28, the controller toggles between the first and second motor operating modes and (b) in response to receiving signals from one or more pump operating sensors (not shown), the controller automatically varies the rotational speed of the AC motor 22 to thereby maintain the relevant set point stored on the storage device 24 in accordance with a pump control mode selected via the user control device 28.

[0032] More particularly, when operating in the first motor operating mode the control system 10 may be configured to supply power to and control a brushless permanent magnet AC motor of the electric pump 12 in accordance with control signals issued by the controller 20. An example brushless permanent magnet AC motor 30 is depicted schematically in Figure 2(a). The motor 30 may comprise a rotor 32 embedded with permanent magnets 34 that turns synchronously with a rotational magnetic field created by electromagnet field windings 36 in the stator 38. To control the speed of the electric pump 12, the controller 20 may vary the frequency of alternating current that is supplied to the motor 30 via the output 16. Varying the alternating current, in turn, varies the rotational speed of the current-induced magnetic field of the stator 38 and, consequently, the rotational speed of the rotor 32.

[0033] To ensure that the rotor 32 always turns synchronously with the magnetic field, the controller 20 may receive signal information from one or more sensors (not shown) attached to the motor 30 that track the rotational position of the rotor 32 during use. The signal information may comprise a continuous analogue signal or discrete digital signals generated by the sensors at fixed time intervals that corresponds to the rotor's 32 current position. The controller 20 uses the received signal information to ensure that the magnetic field of the stator 38 always rotates at a speed that causes the rotor 32 to turn synchronously with the field.

[0034] In examples where the permanent magnet motor 30 is not self starting, the controller 20 may cause the control system 10 to accelerate the rotor 32 to synchronous speed during a start up phase of the motor 30. For example, the motor 30 may comprise its own starting circuit, as commonly provided in so-called "line start" permanent magnet motors. The controller 20 may cause the starting circuit to accelerate the rotor 32 to synchronous speed during the start up phase. Once synchronous speed has been achieved, the controller 20 may disengage from the starting circuit and enter into an operation mode wherein the rotor 32 speed is then controlled solely by varying the alternating current supplied to the stator 38.

[0035] Instead of the permanent magnet motor 30, the control system 10 may be configured to operate an alternative type of synchronous AC motor when operating in the first operating mode. For example, the control system 10 may be configured to power and control a hysteresis motor or a reluctance motor of the electric pump 12.

[0036] When operating in the second motor operating mode, the control system 10 may be configured to power and control an AC induction motor of the electric pump 12 in accordance with control signals issued by the controller 20. An example induction motor is depicted schematically in Figure 2(b) which comprises a squirrel cage rotor 42 surrounded by a stator 44. A rotational magnetic field that is created by electromagnets in the stator 44 induces an opposing magnetic field in the rotor 42 causing a torque that rotates the rotor 42 asynchronously with the magnetic field. To control the speed of the electric pump 12, the controller 20 may vary the frequency of the alternating current that is supplied to the motor 40 via the output 16. Varying the alternating current, in turn, varies the rotational speed of the stator's 44 magnetic field and, consequently, the rotational speed of the rotor 42 in an asynchronous manner. When the controller 20 is accelerating the speed of the rotor 42 to a target speed, the controller 20 may take into account the slip between the respective rotational speeds of the stator 44 magnetic field and the rotor 42 as is inherent in induction motors. The slip may also be taken into account by the controller 20 when maintaining the target speed.

[0037] The induction motor 40 may be a poly-phase motor. For example, the induction motor 40 may comprise a three phase induction motor provided with a three-phase electrical input connector assembly that has a star or delta configuration. The output 16 of the control system 10 may be configured to interface with this connector assembly for supplying the required three phase power.

[0038] The user control device 28 may be used by an operator of the control system 10 to switch the control system 10 between its two motor operating modes. The user control device 28 may also be used by the operator to set and store a set point on the storage device 24 and cause the controller 20 to operate in accordance with a pump control mode corresponding to the set point. For example, the operator may use the control device 28 to enter a constant water flow rate and cause the controller 20 to enter into a pump control mode wherein the speed of the electric pump 12 is regulated by the controller 20 to maintain the constant flow rate recorded on the storage device 24 during use.

[0039] The communications interface 26 may enable the controller 20 to be connected remotely to the user control device 28. For example, the communications interface 26 may comprise a radio transceiver or a network interface that enables the user control device 28 to be connected via a LAN, WAN, WLAN, the Internet, cellular or mobile network or other computer or digital network 46. The user control device 28 may comprise a touch-screen display or similar electronic user interface that enables a human operator to set, activate and monitor the operation of the control system 10 in addition to toggling between the two motor operating modes. In other examples, the user control device 28 may comprise a remote control centre that enables human operators to control the control system 10 in addition to other items of equipment located at the relevant site where the electric pump 12 is deployed. In another example, the communications interface 26 may enable the controller 20 to be connected by wire to the user control device 28. In one further example, the control system 10 may comprise a mechanical switch assembly (not shown) coupled to the controller 20 for switching the control system 10 between its two motor operating modes.

[0040] The controller 20 may comprise a processor, a programmable logic controller (PLC), a programmable logic array (PLA) or similar electronic controller device. In examples where the controller 20 comprises a processer, the processer comprises a device capable of executing instructions encoding arithmetic, logical and/or 1/O operations and includes both a physical and a virtual processor. 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 processor may be implemented as a single integrated circuit, two or more integrated circuits, or may be a component of a multi-chip module.

[0041] The storage device 24 coupled to the controller 20 may store first and second datasets corresponding to, respectively, the first and second motor operating modes. The two datasets record the various operational parameters and settings that may be accessed and used by the controller 20 when supplying power to, and controlling, the relevant synchronous or asynchronous motor, as the case may be, connected to the control system 10 in accordance with the selected motor operating mode. For example, each dataset may comprise electrical voltage, current and timing parameters, starting and operation phase motor control parameters, acceleration profile and motor response times, speed-torque and performance curve metrics and operating limitations and tolerances for each type of electric motor 22.

[0042] The storage device 24 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 24 may be integral with the controller 20 or it may be an external storage device in communication with the controller 20 via a wired or wireless communication means such as, for example, a USB cable, optical fibre, ethernet or WiFi.

[0043] The controller 20 may also control the rotational speed of the motor 22 in response to feedback received from one or more sensors that measure operating conditions of the electric pump 12, the control system 10 or devices connected to the electric pump 12 or control system 10. The sensors may, for example, comprise a temperature sensor that measures an operating temperature of the electric pump 12, a vibration sensor that measures mechanical vibrations of the electric pump 12 or a temperature sensor that measures an operating temperature of the control system 10 or a control device connected to the controller 20.

[0044] The controller 20 may cause the control system 10 to control the rotational speed of the motor 22 to maintain the relevant set point stored on the storage device 24 during use in response to feedback received from pump sensors measuring the corresponding operating conditions. The pump sensors may, for example, comprise a fluid level, fluid flow or fluid pressure sensor.

[0045] The input 14 of the control system 10 may be connected to a variety of different electrical power sources 18. For example, as depicted in Figure 3, the control system 10 may also comprise a variable speed drive 50 that is electrically connectable to an AC power source 18. The AC power source 18 may comprise a genset comprising an alternator 52 mechanically coupled to an engine 54, or a similar prime mover, that drives the alternator 52.

[0046] The variable speed drive 50 may comprise a variable frequency drive. Control signals issued by the controller 20 may cause the variable frequency drive 50 to vary the frequency of the alternating current received from the alternator 52 and supplied to the motor 22 via the output 16. The control system 10 may also comprise a harmonic filter 56 electrically connected between the variable frequency drive 50 and the motor 22 for reducing harmonics in the alternating current supplied to the motor 22. As depicted in Figure 3, the alternating current may be supplied from the variable frequency drive 50 and filter 56 directly to the motor 22 via the output 16, with the controller 20 issuing control signals to the variable frequency drive 50 and filter 56. In other examples, the alternating current that is output from the variable frequency drive 50 and filter 56 may be supplied to the controller 20 and the controller 20 may, in turn, supply the alternating current to the motor 22 via the output 16.

[0047] The various components comprised in the control system 10 (including any variable speed drive 50 incorporated into the control system 10) may each be sized and rated such that the control system 10 is capable of supplying the necessary power required to operate the electric motor 22 effectively based on its speed and torque requirements. For example, where the electric motor 22 is used to drive an ESP deployed in a borehole for groundwater control, the control system 10 may be capable of supplying a total of between 22 and 150 kilowatts (kW) of power to the electric motor 22.

[0048] Referring to Figure 4, in another example the control system 10 may be connected to a variable speed genset 60 comprising an alternator 62 mechanically driven by an engine 64. The engine 64 may comprise a throttle assembly 66 that may comprise a digital engine controller. The controller 20 may send control signals to the throttle assembly 66 to thereby control a speed of the engine 64 and, consequently, the frequency of the alternating current generated by the alternator 62.

[0049] The alternator 62 may comprise an AC voltage regulator or excitation controller 68 that is also operated by the controller 20 to control the voltage of the alternating current generated by the alternator 62. In this configuration, the control system 10 may supply variable AC power to the electric pump 12 without the need for a variable speed drive 50. The controller 20 may use the throttle 66 and the voltage regulator 68, together, to control the final frequency and voltage of the alternating current that is received by the electric pump 12 and to ensure that the current conforms to the electrical characteristics and operating parameters of the relevant AC motor 22.

[0050] The voltage regulator 68 may also comprise components and circuitry that enable the frequency of the alternating current that is generated by the alternator 62 to be controlled with additional precision. For example, the voltage regulator 68 may comprise a pulse width modulation (PWM) circuit (not shown) comprising an AC to DC rectifier connected to a filter. The filter is, in turn, connected to a DC to AC inverter. In this configuration, in addition to using the throttle 66 to control the output frequency, the controller 20 may send control signals to the PWM circuit that cause it to make further/finer adjustments to the frequency.

[0051] In each of the examples depicted in Figures 3 and 4, control signals that are issued by the controller 20 to the various components comprised in and connected to the controller 20 may comprise digital control signals. For example, the control system may comprise a communications bus connecting the controller 20 to the components and the control signals may comprise digital machine code instructions transmitted via the communications bus. In other examples, the controller 20 may be connected to the components via an internal packet-switched network and the control signals may comprise data packets transmitted over the network. The internal network may be a controller area network that implements an industry standard message-based protocol such as CANbus or Modbus. In other examples, the controller 20 may be configured to issue analogue control signals, such as reference voltages, to the components.

[0052] Referring to Figure 5(a), the control system 10 may comprise a single output terminal 70 that is electrically connectable to either a synchronous or an asynchronous AC motor of an electric pump 12 via a single control line assembly 72. In both of the motor operating modes, electrical power and control signals sent from the control system to the electric pump 12 are all transmitted via the control line assembly 72. In other examples, as shown in Figure 5(b) the control system 10 may comprise a pair of separate output terminals 74,76 that are electrically connectable to, respectively, a synchronous AC motor 78 and an asynchronous AC motor 80 of an electric pump 12 via separate control line assemblies 82,84. Electrical power and control signals are transmitted from the control system 10 via one of the relevant control line assemblies 82,84 according to the type of motor that is connected and the relevant motor operating mode that is selected.

[0053] A circuit breaker (not shown) may be disposed between the control system 10 and the connected electric pump 12 that prevents the electric pump 12 from drawing too much current from the control system 10 during use. The controller 20 may be communicatively connected to the circuit breaker and configured to monitor and reset the circuit breaker in accordance with programmed logic executed by the controller 20 and/or operator instructions manually issued using the user input device 28.

[0054] In other examples, the control system 10 may comprise a second input (not shown) in addition to the input 14. The second input may be electrically connectable to an auxiliary power system which the control system 10 draws AC current from and also uses to power the electric pump via the output 16. The auxiliary power system may comprise a direct current (DC) generator system or power source connected to an inverter, including a renewable source of DC power. More particularly, the DC generator system may comprise one or more solar cells connected to the inverter. The solar cells may be arranged in solar panels that are connected to the outside of a supporting frame or housing that the components of the control system 10 are contained inside or attached to. In other embodiments, one or more of the solar cells may be integral with the supporting frame or housing. For example, the solar cells may be embedded into elongate supports of the frame. The solar generator may also comprise a regulator that is connected between the solar cells and the inverter for controlling the direct current supplied to the inverter.

[0055] In other embodiments, the DC generator system may comprise a wind turbine or a thermoelectric generator connected to the inverter. In examples where a thermoelectric generator is used, the thermoelectric generator may convert surplus heat created by the internal electric components of the control system 10 or ambient heat of air surrounding the components of the system control 10 into direct current that is supplied to the inverter.

[0056] In use, the control system 10 may be used to supply power to and control an electric pump 12, including an ESP, that comprises a mechanical pump assembly 90 operatively driven by a synchronous or an asynchronous electric motor 22. The mechanical pump assembly 90 may comprise a centrifugal pump, a positive displacement pump or other pump design. The control system 10 may be selectively switched between the first (synchronous) motor operating mode and the second (asynchronous) motor operating mode on an as-needed basis according to the type of motor that needs to be connected. For example, if the control system 10 is connected to an ESP comprising an asynchronous induction motor that needs to be replaced with a more efficient synchronous permanent magnet motor, then the controller 20 may be conveniently switched to the first motor operating mode and then immediately connected to the new motor. Similarly, if the ESP has a permanent magnet motor that has worn out and needs to be replaced with a cheaper induction motor, then the controller 20 may be switched to the second motor operating mode and connected to the induction motor.

[0057] The ability to switch between motor operating modes on the fly advantageously provides plug-and-play functionality that avoids the costs and project delays associated with procuring new control systems when pump motors needs to be swapped out. The control system 10 may be used to power and control a wide range of synchronous and asynchronous AC motors operating at a range of kilowatt power ratings and frequencies, including 50Hz, 60Hz, 100Hz and 120Hz motors.

[0058] When the control system 10 has been deployed and set to one of the selected motor control modes, the controller 20 may monitor operating conditions associated with the control system 10 or electric pump 12 during use and regulate the rotational speed of the motor 22 of the electric pump 12 in response to changes in the operating conditions. For example, the controller 20 may be configured to implement a safety feature wherein the speed is reduced when a temperature sensor installed in the electric pump 12 indicates that the temperature of the motor 22 has met or exceeded a particular maximum value set by an operator of the control system 10. The temperature sensor may, for example, comprise a positive temperature coefficient resistor or similar temperature measuring device communicatively coupled to the controller 20. The controller 20 may also be configured to stop the motor of the electric pump 12 altogether and/or issue a warning or alert via the communications interface 26 to the user control device 28 when the maximum temperature value is exceeded.

[0059] The controller 20 may also be configured to transmit warnings or alerts to the user control device 28 when it predicts when particular operating conditions of the control system 10 and/or electric pump 12 may occur or arise in the future. The controller 20 may make such predictions based on the historical mode of operation and/or duration of operation of the control system 10 and/or electric pump 12 that is tracked and recorded by the controller 20.

[0060] The controller 20 may also be programmed with set points relating to the operating environment (and/or conditions) of the pump 12 and may vary the speed of the motor 22 in order to maintain the set points during use. For example, the controller 20 may be programmed with a set point that relates to a fixed fluid level of a well bore that the pump 12 is deployed in. If the fluid level rises above the set level, the controller 20 may automatically increase the speed of the motor 22 so that the pump 12 works harder and brings the fluid level down to the set level (and vice versa if the fluid level falls below the set level).

[0061] The control system 10 may be used to power and control individual electric pumps or it may be integrated into a wider control system that is used to control and/or monitor multiple pumps operating simultaneously at a given site. For example, referring to Figure 6 there is depicted a control system 100 for a plurality of electric pumps 12. The master control system 100 comprises a master controller 102. Each of the electric pumps 12 is powered and operated by the control system 10.

[0062] The controller 20 of each control system 10 may be in communication with the master controller 102 via a computer network 104. The network 104 may comprise a LAN, WAN, WLAN, the Internet, cellular or mobile network or other computer or digital network. In other examples, the controller 20 of each control system 10 may be in communication with the master controller 102 via a radio transceiver or another communications interface device 104.

[0063] Each controller 20 may be configured to transmit data relating to the operation of the relevant control system 10 and/or relevant electric pump 12 that it controls to the master controller 102. The master controller 102 may also send master control signals to each controller 20. Each controller 20 may, in turn, be configured to control a rotational speed of the relevant AC motor 22 of the electric pump 12 connected to the control system 10 in accordance with the master control signals. For example, the master control signals may cause the relevant controller 20 to toggle between the two motor operating modes and/or they may cause one or more set points stored and maintained by controller 20 to be added, modified or deleted.

[0064] For the purpose of this specification, the word "comprising" means "including but not limited to", and the word "comprises" has a corresponding meaning.

[0065] 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 control system for an electric pump, the control system comprising: an input and an output electrically connectable to, respectively, a power source and the electric pump; a controller configured to cause variable electrical power to be supplied to an AC motor of the electric pump via the output and thereby control a rotational speed of the AC motor, wherein the controller is connectable to a user control device and is selectively switchable between first and second motor operating modes using the user control device, wherein for the first of the motor operating modes the AC motor is a synchronous AC motor and for the second of the motor operating modes the AC motor is an asynchronous AC motor; a storage device coupled to the controller that stores at least one set point relating to a measurable condition or state of fluid pumped by the electric pump; and a sensor configured to measure the measurable condition or state of the fluid pumped by the electric pump, wherein the controller is further configured such that in response to receiving signals from the sensor the controller automatically increases or decreases the rotational speed of the AC motor to maintain the set point.

2. The control system according to claim 1, wherein in the first of the motor operating modes the synchronous AC motor is a brushless permanent magnet AC motor.

3. The control system according to claim 2, wherein the controller is configured to control a frequency of alternating current supplied to the brushless permanent magnet AC motor via the output and thereby control a synchronous rotational speed of a rotor of the brushless permanent magnet AC motor in response to feedback received by the controller from one or more rotor sensors tracking a position of the rotor.

4. The control system according to claim 3, wherein the controller is further configured to cause the rotor to accelerate to synchronous rotational speed during a start up phase of the brushless permanent magnet AC motor.

5. The control system according to any one of the preceding claims, wherein in the second of the motor operating modes the asynchronous AC motor is an induction motor.

6. The control system according to claim 5, wherein the controller is configured to allow for slip of the induction motor when controlling a rotational speed of a rotor of the induction motor.

7. The control system according to claim 5 or 6, wherein the control system is configured such that poly-phase electrical power is supplied to the induction motor via the output.

8. The control system according to claim 7, wherein the control system is configured such that three phase electrical power is supplied to the induction motor via the output.

9. The control system according to claim 8, wherein the output is electrically connectable to the induction motor using a star or delta configuration for supplying the three phase electrical power.

10. The control system according to any one of the preceding claims, wherein the controller is remotely connectable to the user control device via a computer network.

11. The control system according to any one of the preceding claims, wherein the controller is further configured to vary the rotational speed of the AC motor in response to feedback received from one or more sensors measuring operating conditions of one or more components comprised in or connected to the electric pump.

12. The control system according to claim 11, wherein the sensors comprise a temperature sensorfor measuring an operating temperature of the electric pump.

13. The control system according to any one of the preceding claims, wherein the control system further comprises a variable speed drive connected to the input, wherein the control system causes the variable speed drive to vary AC electrical power received via the input and supplied to the AC motor via the output.

14. The control system according to claim 13, wherein the variable speed drive is a variable frequency drive and the control system further comprises a harmonic filter electrically connected to the variable frequency drive for reducing harmonics in the AC electrical power supplied to the AC motor via the output.

15. A power and control system for an electric pump, comprising: a variable speed genset; an output electrically connectable to the electric pump; a controller configured to cause variable electrical power to be supplied from the variable speed genset to an AC motor of the electric pump via the output and thereby control a rotational speed of the AC motor, wherein the controller is connectable to a user control device and is selectively switchable between first and second motor operating modes using the user control device, wherein for the first of the motor operating modes the AC motor is a synchronous AC motor and for the second of the motor operating modes the AC motor is an asynchronous AC motor; and a storage device coupled to the controller that stores at least one set point relating to a measurable condition or state of fluid pumped by the electric pump; and a sensor configured to measure the measurable condition or state of the fluid pumped by the electric pump, wherein the controller is further configured such that in response to receiving signals from the sensor the controller automatically increases or decreases the rotational speed of the AC motor to maintain the set point.

16. The power and control system according to claim 15, wherein the genset comprises an alternator mechanically coupled to an engine, the engine comprising a throttle assembly, and wherein the controller is configured to operate the throttle assemblyto control a speed of the engine and electrical power generated by the alternator.

17. The power and control system according to claim 16, wherein the alternator comprises a voltage regulator operated by the controller to control an output voltage of the alternator.

14 16

Power Controller Motor Pump 18 20 22 90

12 1/6

24

I/O 46 UI

10 26 28

Figure 1

40

38 44

34 42

32 36 2/6

Figure 2(a) Figure 2(b)

14 16

Engine Alternator VSD Filter Motor Pump 54 52 50 56 22 90 3/6

18 12

I/O Controller UI 24 46 26 20 28

10

Figure 3

Throttle VR 66 68 Engine Alternator Motor Pump 64 62 22 90 4/6

60 12

I/O Controller UI 24 26 46 20 28

10

Figure 4

Electric pump 70 12

12.1

Figure 5(a)

Sync Motor Pump 82 78 90 5/6

74

10

76

Async Motor Pump 84 80 90

Figure 5(b) 12.2

10.1 12.1

100

Controller Motor Pump 20 22 90

10.2 12.2

Master Controller Motor Pump 104 6/6

Controller 20 22 90 102

10.3 12.3

Controller Motor Pump 20 22 90

Figure 6