AU2021215197B2

AU2021215197B2 - Fuel supply system

Info

Publication number: AU2021215197B2
Application number: AU2021215197A
Authority: AU
Inventors: Jonathan Florent Douce; Steven Vose
Original assignee: Allied Pumps Pty Ltd
Current assignee: Allied Pumps Pty Ltd
Priority date: 2021-08-11
Filing date: 2021-08-11
Publication date: 2024-02-22
Anticipated expiration: 2041-08-11
Also published as: AU2025271519A1; AU2021215197A1; AU2024203422B2; AU2021107610B4; AU2021107610A4; AU2024203422A1

Abstract

A fuel supply system for a generator engine comprises first and second tanks and an actuable valve assembly fluidly connected to the engine and first tank. The valve assembly operated by a system controller is releasably fluidly connectable to the second tank and is switchable between first and second operating modes wherein fuel is supplied to the engine from, respectively, the first and second tank by a pump. A sensor outputs sensor information corresponding to a fuel level in the second tank. When the second tank is disconnected, the valve assembly operates in the first operating mode only. When the second tank is connected, in response to the sensor information the valve assembly operates in the second operating mode when a fuel level in the second tank is at or above a predetermined level and operates in the first operating mode when the fuel level is below the predetermined level.

Description

FUEL SUPPLY SYSTEM

Field

[0001] The present invention relates to fuel supply systems and, more particularly, to a fuel supply system for an engine-generator that uses multiple fuel tanks.

Background

[0002] A variety of electrical equipment and systems are used in remote locations in industry. For example, electric submersible pumps (ESPs) are commonly used to pump oil and water from wellbores and to control groundwater in mining and construction projects. When a grid-based supply of electricity is not available to power a pump, electricity must be created and supplied locally using an electric generator. A generator typically comprises an engine, such as a reciprocating diesel or petrol engine, that is mechanically coupled to an alternator to produce AC power. Electric generators of this configuration are commonly referred to as engine-generators.

[0003] An engine-generator includes a fuel tank that is normally integrated into the housing or trailer structure that the engine-generator is mounted to. For many applications, it is necessary for the generator to produce an uninterrupted and continuous supply of power over a long period of time. If the fuel in the tank is used up during this period, then the generator stops operating. Some engine-generators are, therefore, provided with a second fuel tank that is detachably connectable to the generator's engine. The second fuel tank provides an additional source of fuel that can be disconnected, replenished and reconnected to the generator during use as required. When the second fuel tank has been depleted of fuel or is disconnected from the generator, the generator's engine can then use fuel from the first (onboard) fuel tank until fuel subsequently becomes available from the second fuel tank. To allow this to happen, the generator typically includes a manually-operated mechanical switchover valve that a human operator uses to cause the engine to extract fuel from the first fuel tank instead of the second fuel tank. Requiring an operator to perform this task is inefficient and consumes human resources that could be used for other, more-useful purposes. If the operator is not available to perform the switchover, or fails to notice that the second tank is near to being depleted, then the generator can become starved of fuel and cease to operate.

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

Summary

[0005] According to the present invention, there is provided a system for supplying fuel to an engine of an electrical generator, the system comprising: an internal fuel tank and one or more external fuel tanks; an actuable valve assembly that is fluidly connected to the engine and to the internal fuel tank, wherein the actuable valve assembly is also detachably fluidly connectable to the one or more external fuel tanks and is operatively switchable between at least a first and a second operating mode, wherein in the first operating mode the actuable valve assembly is configured to supply the fuel from the internal fuel tank to the engine, and wherein in the second operating mode the actuable valve assembly is configured to supply the fuel from at least one of the external fuel tanks to the engine; a fuel pump for pumping the fuel from the internal fuel tank and/or the one or more external fuel tanks to the engine via the actuable valve assembly; at least one sensor configured to output sensor information corresponding to a level of fuel in the at least one of the external fuel tanks, wherein the sensor is detachably connectable to the system controller; and a system controller operatively connected to the actuable valve assembly and to the fuel pump, wherein the system controller is configured to operate the fuel pump and the actuable valve assembly such that: when the sensor is disconnected from the system controller, the system controller causes the actuable valve assembly to operate in the first operating mode only; and when the sensor is connected to the system controller, in response to the sensor information the system controller causes the actuable valve assembly to operate in the second operating mode when the level of fuel is at or above a predetermined level stored in the system controller, and to operate in the first operating mode when the level of fuel is below the predetermined level.

[0006] The system may comprise: a first hydraulic fuel circuit for circulating the fuel between the internal fuel tank and the engine; a second hydraulic fuel circuit for circulating the fuel between the at least one of the external fuel tanks and the engine; and one or more fuel injectors for injecting the fuel into the engine from the first and the second hydraulic fuel circuit, and wherein the actuable valve assembly and fuel pump are configured such that in the first and the second operating mode the fuel is circulated under pressure around, respectively, the first and the second hydraulic fuel circuit.

[0007] The actuable valve assembly may comprise an input fuel line and an output fuel line arranged to supply the fuel to and from the fuel injectors respectively, and wherein the first hydraulic fuel circuit is provided by: the input and the output fuel line; a first fuel supply line arranged to supply the fuel from the internal fuel tank to the actuable valve assembly; and a first fuel return line arranged to return the fuel from the actuable valve assembly to the internal fuel tank.

[0008] The second hydraulic fuel circuit may be provided by: the input and the output fuel line; a second fuel supply line arranged to supply the fuel from the at least one of the external fuel tanks to the actuable valve assembly; and a second fuel return line arranged to return the fuel from the actuable valve assembly to the at least one of the external fuel tanks.

[0009] The actuable valve assembly may be configured such that: in the first operating mode, the actuable valve assembly fluidly connects the first fuel supply line to the input fuel line, and the first fuel return line to the output fuel line; and in the second operating mode, the actuable valve assembly fluidly connects the second fuel supply line to the input fuel line, and the second fuel return line to the output fuel line.

[0010] The sensor may be detachably connectable to the system controller by a control line that is provided with a plug and socket arrangement.

[0011] The sensor may be deployed inside and attached to the at least one of the external fuel tanks.

[0012] The system may comprise a second sensor connected to the system controller that is configured to output sensor information corresponding to an amount of fuel available in the internal fuel tank, wherein the system controller is configured to stop the fuel pump from operating when the system controller determines, based on the sensor information output by the second sensor, that a level of fuel in the internal fuel tank is at or below a predetermined level stored in the system controller.

[0013] The system may comprise a communication means for remotely connecting the system controller to one or more remote user devices, wherein the system controller is configured to issue an alert or notification to the one or more remote user devices by the communication means when the system controller determines that the level of fuel in the external fuel tank is below a predetermined level stored in the system controller.

[0014] The system may comprise: a second of the external fuel tanks; and an additional sensor detachably connectable to the system controller, wherein the additional sensor is configured to output sensor information corresponding to a level of fuel in the second of the external fuel tanks, wherein the system controller causes the actuable valve assembly to supply the fuel to the engine from the second of the external fuel tanks if the sensor information output by the additional sensor indicates that the level of fuel in the second of the external fuel tanks is at or above a predetermined level stored in the system controller.

[0015] The present invention also provides a generator system, the generator system comprising: an engine; the system as described above for supplying fuel to the engine; an alternator driven by the engine to produce an alternating current, the alternator comprising a voltage regulator for controlling a voltage of the alternating current; a throttle controller for controlling a rotational speed of the engine and, therefore, frequency of the alternating current; and a generator controller configured to control the throttle controller and the voltage regulator to control the frequency and voltage of the alternating current respectively.

[0016] The generator system may be connected to an electric motor, the electric motor being powered by the alternating current produced by the alternator.

[0017] The generator system may comprise a further sensor, wherein the further sensor is configured to output information about an operating environment or condition of the electric motor, wherein the generator controller is connected to the further sensor and is configured to control a speed of the electric motor by controlling the throttle controller and the voltage regulator in response to the information output by the further sensor.

[0018] The generator controller may be configured to: store at least one set point relating to an operating environment or condition of the electric motor; and in response to the information output by the further sensor, control the speed of the electric motor such that the set point is maintained.

[0019] The electric motor may operatively drive a submersible pump and the set point may relate to an operating environment or condition of the submersible pump.

[0020] The set point may be one of a set of values corresponding to a desired fluid pressure, a desired fluid flow rate and a desired fluid level.

[0021] The generator controller may comprise a first controller connected to a second controller, wherein the first controller is connected to the further sensor and is configured to generate and send control signals to the second controller based on the information output by the further sensor, and wherein the second controller is connected to the throttle controller and to the voltage regulator and is configured to control the speed of the electric motor by controlling the throttle controller and the voltage regulator in response to the control signals.

[0022] The control signals that are sent to the second controller may comprise a target speed of the electric motor, and the second controller may cause the electric motor to operate at the target speed.

[0023] The generator controller may be integral with the system controller.

Brief Description of Drawings

[0024] Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is schematic diagram of a fuel supply system for an engine of an electrical generator according to an example embodiment of the invention; Figure 2 is a schematic diagram of an electrical generator system that includes the fuel supply system according to a further example embodiment of the invention; and Figure 3 is a schematic diagram of an electrical generator system that includes the fuel supply system according to a further example embodiment of the invention.

Description of Embodiments

[0025] Referring to Figure 1, an example embodiment of the present invention provides a system 10 for supplying fuel to an engine 12 of an electrical generator. The system 10 comprises a first fuel tank 14 and a second fuel tank 16. An actuable valve assembly 18 is fluidly connected to the engine 12 and to the first fuel tank 14. The actuable valve assembly 18 is also detachably fluidly connectable to the second fuel tank 16 and is operatively switchable between at least a first and a second operating mode. In the first operating mode, the actuable valve assembly 18 is configured to supply the fuel from the first fuel tank 14 to the engine 12. In the second operating mode, the actuable valve assembly 18 is configured to supply the fuel from the second fuel tank 16 to the engine 12. The system 10 also comprises a fuel pump 20 for pumping the fuel from the first fuel tank 14 and/or second fuel tank 16 to the engine 12 via the actuable valve assembly 18, and a sensor 22 configured to output sensor information corresponding to a level of fuel in the second fuel tank 16.

[0026] A system controller 24 is connected to the actuable valve assembly 18 and to the sensor 16. The system controller 24 is configured such that (i) when the second fuel tank 16 is fluidly disconnected from the actuable valve assembly 18, the system controller 24 causes the actuable valve assembly 18 to operate in the first operating mode only, and (ii) when the second fuel tank 16 is fluidly connected to the actuable valve assembly 18, in response to the sensor information the system controller 24 causes the actuable valve assembly 18 to (a) operate in the second operating mode when a level of fuel in the second fuel tank 16 is at or above a predetermined level stored in the system controller 24, and to (b) operate in the first operating mode when the level of fuel is below the predetermined level.

[0027] More particularly, in the example depicted the system 10 is configured to supply the fuel under pressure to one or more fuel injectors deployed in the engine 12. The actuable valve assembly 18, therefore, comprises an input fuel line 30 for supplying the fuel to the injectors, and an output fuel line 32 for returning unused fuel that is not sprayed by the injectors into the engine 12 cylinders back to the actuable valve assembly 18. The system 10 also comprises a first fuel supply line 34 that is arranged to supply fuel from the first fuel tank 14 to the actuable valve assembly 18, and a first fuel return line 36 that is arranged to return unused fuel from the actuable valve assembly 18 back to the first fuel tank 14. In this configuration, fuel lines 30, 32, 34, 36 together form a first hydraulic fuel circuit that is used to circulate fuel from the first fuel tank 14 to and from the injectors of the engine 12. The system 10 also comprises a second fuel supply line 38 that is arranged to supply fuel from the second fuel tank 16 to the actuable valve assembly 18, and a second fuel return line 40 that is arranged to return unused fuel from the actuable valve assembly 18 back to the second fuel tank 16. In this configuration, fuel lines 30, 32, 38, 40 together form a second hydraulic fuel circuit that is used to circulate fuel from the second fuel tank 16 to and from the injectors of the engine 12.

[0028] In the above configuration, when the system controller 24 causes the actuable valve assembly 18 to switch into its first operating mode, the actuable valve assembly 18 fluidly connects the first fuel supply line 34 to the input fuel line 30, and fluidly connects the first fuel return line 36 to the output fuel line 32, thus completing the first hydraulic fuel circuit. The pump 20 then causes fuel from the first fuel tank 14 to be circulated under pressure, via the valve assembly 18, about the first hydraulic fuel circuit. Similarly, when the system controller 24 causes the actuable valve assembly 18 to switch into its second operating mode, the actuable valve assembly 18 fluidly connects the second fuel supply line 38 to the input fuel line 30, and fluidly connects the second fuel return line 40 to the output fuel line 32, thus completing the second hydraulic fuel circuit. The pump 20 then causes fuel from the second fuel tank 16 to be circulated under pressure, via the valve assembly 18, about the second hydraulic fuel circuit. The actuable valve assembly 18 may comprise a pair of electrically actuatable directional control valves 43, such as solenoid actuated valves, that operate in response to control signals issued by the system controller 24 to switch selectively between the first and second hydraulic fuel circuits.

[0029] The sensor 22 may be detachably connected to the system controller 24. In such examples, the system controller 24 may be configured to enable and disable the second operating mode automatically when the sensor 22 is, respectively, connected and disconnected to/from the system controller 24. For example, the sensor 22 may be detachably connected to the system controller 24 by a control line 42 that is provided with a plug and socket arrangement 44. The sensor 22 may comprise any device that is capable of generating a signal that corresponds to the amount of fuel remaining in the second fuel tank 16. For example, the sensor 22 may comprise a float-based, ultrasonic, capacitive, resistive film or discrete resistor-based level sensor. The sensor 22 may output an electrical signal that directly corresponds to the current fuel level that the system controller 24 is capable of receiving and processing. For example, the sensor 22 may output an analogue electrical signal falling within a 4-20 mA range, wherein the value of the signal current corresponds to the level of fuel. When the sensor 22 is connected to the system controller 24 using the plug and socket 44, this may complete an electrical circuit in the control line 42 which the system controller 24 detects and, therefore, determines automatically that the sensor 22 is available. The system controller 24 may be configured such that it only enables the second operating mode when the information received from the sensor 22 shows that the level of fuel in the second fuel tank 16 is at or above the predetermined level stored in the system controller 24.

[0030] The sensor 22 may be deployed and attached to an inside part of the second fuel tank 16. In such examples, when the second fuel tank 16 is delivered to the electrical generator for connection to the valve assembly 18 and system controller 24 during use, the sensor 22 is conveniently already deployed inside the second fuel tank 16 and may, therefore, be rapidly and easily connected to the controller 24 using the plug and socket 44.

[0031] In use, when the second fuel tank 16 is not connected to the system 10, the system controller 24 causes the valve assembly 18 to operate in the first operation mode and fuel is, therefore, consumed by the engine 12 from the first fuel tank 14 only. When the second fuel tank 16 and sensor 22 are connected to the system 10 and fuel is available in tank 16, the system controller 24 causes the valve assembly 18 to operate in the second operation mode such that the fuel in tank 16 is always used by the engine 12 before any fuel is used from the first tank 14. The system controller 24 only causes the valve assembly 18 to switch into the first operation mode when the fuel in the second fuel tank 16 falls below the predetermined fuel level stored in the system controller 24. The predetermined fuel level may be a value that corresponds to the tank 16 being partially empty (e.g., 50% empty), substantially empty (e.g, 90% or 95% empty) or completely empty.

[0032] The system 10 may also comprise a second sensor 50 connected to the system controller 24 that is configured to output sensor information corresponding to an amount of fuel available in the first fuel tank 14. The system controller 24 may be configured to stop the fuel pump 20 from operating when the system controller 24 determines, based on the information from the second sensor 50, that the level of fuel in the first fuel tank 14 is at or below a predetermined level stored in the system controller 24.

[0033] In other examples, the system 10 may also comprise a third fuel tank (not shown) that is detachably fluidly connectable to the actuable valve assembly 18, and a third sensor (not shown) configured to output sensor information corresponding to an amount of fuel available in the additional fuel tank. As for the second fuel tank 16, the system controller 24 may cause the actuable valve assembly 18 to supply fuel to the engine 12 from the third fuel tank when the sensor information output by the third sensor indicates that a level of fuel in the third fuel tank is at or above a predetermined level stored in the system controller 24. In such examples, the system controller 24 may cause the fuel stored in the three tanks to be consumed by the engine 12 in reverse order. That is to say, the fuel in the second 16 and first tanks 14 is not used until the level of fuel in the third tank has fallen below the relevant predetermined value and then, subsequently, the fuel in the first tank 14 is not used until the level of fuel in the second tank 16 has fallen below the relevant predetermined value. In other examples, additional detachable fuel tanks (e.g., fourth, fifth tanks, etc.) may be attached to the system 10 and provisioned in a like manner during use.

[0034] The fuel supply system 10 is suitable for supplying fuel to a variety of engine-generators, including fixed speed and variable-speed generators. For example, referring to FIG. 2 there is depicted a variable speed AC generator system 60 that comprises the engine 12 and an alternator 62 driven by the engine 12 to produce an alternating current. The engine 12 comprises a throttle controller 64 for controlling a rotational speed of the engine 12 and, therefore, frequency of the alternating current. The alternator 62 comprises a voltage regulator 66 for controlling a voltage of the alternating current. The system controller 24 operates as a generator controller in addition to controlling the fuel supply system 10 that is integrated into the generator 60. The system controller 24 is, therefore, configured to control the throttle controller 64 and the voltage regulator 66 to, therefore, control the frequency and voltage of the alternating current produced by the alternator 62 respectively. The generator system 60 comprises the first and second fuel tanks 14, 16 that are fluidly connected to the engine 12 by the fuel supply system 10. In the example depicted, the first fuel tank 14 is an onboard tank that is incorporated into the housing or trailer structure that the engine-generator is mounted to, and the second fuel tank 16 is an external tank that may be connected to the engine-generator as required. However, in other examples, it will be appreciated that both tanks 14, 16 may be external fuel tanks that are separate to the housing or trailer structure and connected to the engine-generator.

[0035] FIG. 3 shows a further variable speed AC generator system 70 that the fuel supply system 10 may be integrated into. The generator system 70 is used to drive an electrical motor load. The generator system 70 comprises the engine 12 and the first and second fuel tanks 14, 16 that are fluidly connected to the engine 12 by the fuel supply system 10. The generator system 70 comprises an alternator 72 for supplying an alternating current to an electric motor 73, wherein the alternator 72 comprises a voltage regulator 74 for controlling a voltage of the alternating current. The engine 12 comprises a throttle controller 76 for controlling a rotational speed of the engine 12 and, therefore, frequency of the alternating current. At least one sensor 78 provides information about an operating environment or condition of the electric motor 73. The generator system 70 comprises a first controller 80 that is operatively connected to a second controller 82. The first controller 80 is connected to the sensor 78 and is configured to generate and send control signals to the second controller 82 based on the information received from the sensor 78. The second controller 82 is connected to the throttle controller 76 and to the voltage regulator 74 and is configured to control a speed of the electric motor 73 by controlling the throttle controller 76 and the voltage regulator 74 in response to the control signals. The fuel supply system 10 that is integrated into the generator 70 may be controlled by either the first controller 80 or the second controller 82.

[0036] More particularly, the electric motor 73 may operatively drive any device or mechanism that needs to be operated on a variable speed basis. For example, the electric motor 73 may drive a pump, such as a centrifugal or positive displacement pump, a fan or a conveyor system. In the example depicted, the generator system 70 is shown connected to an electric motor 73 that operatively drives a submersible pump 90. The submersible pump 90 may comprise a centrifugal pump as commonly used in submersible pumps used in the oil and gas industry to pump oil and oil/water mixtures from wellbores (commonly known as "artificial lift" applications) and in mining and construction to extract and control groundwater at worksites (commonly known as "dewatering" applications). The electric motor 73 may be powered by an alternating current (AC) and may comprise an AC induction or synchronous motor.

[0037] As depicted in FIG. 3, the engine 12 included in the system 70 may comprise a reciprocating internal combustion engine 12, such as a diesel or petrol engine, that operatively drives the alternator 72 to produce AC electrical power. The throttle controller 76 may comprise an actuated governor or, as depicted in FIG. 3, an engine control unit (ECU) 22 that controls electrically the fuel supplied to the engine 12 to control the speed of the engine 12. The second controller 82 may send control signals to the ECU 22 to vary the speed of the engine12 and, consequently, the frequency of the alternating current generated by the alternator 72.

[0038] The alternator 72 may comprise an excitation system provided with field coils. An excitation current, typically a direct current, flowing through the field coils determines the voltage of the alternating current that is generated by the alternator 72. The voltage regulator 74 may be an automatic voltage regulator (AVR) that receives a target output voltage from the second controller 82 and operatively controls the excitation current on an automatic basis such that the alternating current output from the alternator 72 matches the required target voltage. The AVR 74 may either intermittently receive a sequence of target output voltages from the second controller 82 over time, or the AVR 74 may receive a continuous signal from the second controller 82 representing the target voltage to be achieved. The AVR 74 and alternator 72 may be configured such that an output voltage falling within a wide range may be produced by the generator system 70. For example, the generator system 12 may be configured to produce an output voltage of between 400V and 4,800V to allow the system 70 to power and control submersible pumps 30 used in a wide range of applications. This includes, for example: (i) for groundwater control applications in mining and construction, where output voltages of between 400V - 1100V are often required to power submersible pumps deployed in wellbores up to 500m deep; and (ii) for artificial lift applications in the petroleum industry, where higher output voltages up to 4,800V may be required to power submersible pumps deployed in wellbores up to or in excess of 3,000m deep. The system 70 may be provided with a step-up or a step-down transformer (not shown) connected between the generator system 70 and the motor 73 if the range of voltages that can be supplied to the motor73needstobe changed.

[0039] The second controller 82 may comprise discrete control logic that, when executing, causes the second controller 82 to vary the motor's 73 speed in accordance with the control signals issued by the first controller 80 by, as described above - i.e., by using the ECU 76 and AVR 74 to control the frequency and voltage of the alternating current supplied to the motor 73. This control logic may be protected such that the control logic can be selectively enabled and disabled. For example, the second controller 82 may be configured such that the control logic is enabled and executed by the second controller 82 only once a unique digital key 92 has been input into the second controller 82. When the control logic is enabled, the second controller 82 provides for variable speed control of the motor 73 in the manner described above. When the control logic is disabled, the second controller 82 may execute a second mode of operation wherein the electric motor 73 is caused to operate at a fixed speed only.

[0040] The key 92 may be entered into the second controller 82 using an electronic user interface (UI) device that is connectable to the second controller 82 using a wired or wireless connection means. In one example, the key 92 may be entered into the second controller 82 via the first controller 80 and the first controller 80 may be integrated within a control panel that is attached to an external surface of a housing of the system 70. The control panel may include its own UI device, such as an interactive touchscreen display, that allows the key 92 to be entered. The second controller 82 may be deployed inside a housing of the generator system 70 such that it is not accessible by operators and maintenance personnel.

[0041] In further examples, the second controller 82 may include functionality that allows the protected control logic to be disabled even when the correct key 92 has been entered into the second controller 82. In one example, the second controller 82 may disable the control logic and run the fixed-speed operation mode when it receives an explicit instruction to do so from a remote control center or device connected to the system 70. In another example, the second controller 82 may disable the control logic automatically when the second controller 82 detects that the first controller 80 has either stopped functioning correctly during use or has been disconnected from the second controller 82.

[0042] The motor control signals that are issued by the first controller 80 to the second controller 82 may comprise a target speed of the pump's motor 73 that is to be achieved by the second controller 82 using the control logic described above. The system 70 may be configured such that the second controller 82 either receives a sequence of target speeds at intervals from the first controller 80 over time, or receives a continuous signal representing the target motor speed.

[0043] The first controller 80 may also comprise a storage device which stores at least one set point relating to the operating environment or condition of the electric motor 73 or pump 90. The first controller 80 may be configured such that in response to the information received from the sensor 78, the first controller 80 determines the target speed that is sent to the second controller 82 that causes the set point to be maintained. For example, in applications where the motor 73 drives a submersible pump 90, the set point may relate to an operating environment of the pump 90 such as either (i) a desired fluid pressure, (ii) a desired fluid flow rate and/or (iii) a desired fluid level that is to be maintained by the pump 90. The fluid pressure may be a pressure at an inlet or at an outlet of the pump 90 or at a particular position within a column of fluid in a wellbore that the pump 90 is deployed in. The fluid flow rate may be a flow rate in a fluid outlet of the pump 90 or in a tube connected to such fluid outlet. Instead of a fixed value to be maintained by the pump 90, the set point may be a maximum or minimum value that a particular pump operating or environmental parameter must not exceed or fall below respectively, such as maximum fluid pressure, flow rate or level. In other examples, the set point may relate to an operating condition of the motor 73, such as a fixed or maximum operating temperature of the motor 73 or a maximum mechanical vibration level. The first controller 80 may store and maintain any one of the foregoing set points. In other examples, the first controller 80 may store a set consisting of two or more of the foregoing set points (in any combination) and operate to maintain one of the set points included in the set selectively at any one point in time. The relevant set point in the set that is maintained may be selected by an operator of the system 70 using a user input device connected to the system 70. In other examples, the first controller 80 may comprise logic that determines the relevant set point that needs to be maintained automatically based on information received from the sensor 78, or from a set of sensors connected to the first controller 80.

[0044] The sensor 78 may comprise a fluid pressure sensor, fluid flow rate sensor, fluid level sensor, temperature sensor, mechanical vibration sensor or any other type of sensor that provides information allowing the relevant set point to be maintained. In examples where a fluid level set point needs to be maintained, such as a level of water in a borehole for dewatering applications, the sensor 78 may be a hydrostatic sensor that operates by measuring a fluid pressure indicative of the relevant fluid level. The sensor 78 may also be a guided radar device, an ultrasonic device, a magnetostrictive level transmitter or a conductivity sensor when required to measure a fluid level. In such examples, if the fluid level in the borehole rises above the set level in use, the first controller 80 may automatically increase the speed of the motor 73 such that the submersible pump 90 works harder to bring the fluid level down to the set level (and vice versa if the fluid level falls below the set level). In other examples, the motor 73 may be controlled by the first controller 80 such that a particular pump operating or environmental parameter is kept between a range of values stored in the first controller 80, such as between a maximum and a minimum wellbore water or fluid level.

[0045] The first and second controllers 80, 82 may each comprise a processor, a programmable logic controller (PLC), a programmable logic array (PLA) or similar electronic controller device. Each controller 80, 82 may comprise a single integrated electronic controller device or multiple controller devices (including multiple processors or PLAs) connected together via a network, bus or similar communications system. In examples where one (or both) of the controllers 80, 82 comprises a processor, each processor will typically comprise a device that is capable of executing instructions encoding arithmetic, logical and/or 1/O operations. The processor may, for example, comprise an arithmetic logic unit (ALU), a control unit and a plurality of registers. The processor may comprise a single core processor capable of executing one instruction at a time (or process a single pipeline of instructions) or a multi-core processor which simultaneously executes multiple instructions. The processor may be implemented as a single integrated circuit, two or more integrated circuits, or may be a component of a multi-chip module.

[0046] A storage device of the first controller 80 may comprise a volatile or non-volatile memory device, such as RAM, ROM, EEPROM or flash memory, a magnetic or optical disk, a network attached storage (NAS) device or any other device capable of storing data. The storage device may be integral with the first controller 80 or it may be an external storage device in communication with the first controller 80 via a wired or wireless communication means such as, for example, a USB cable, optical fibre, ethernet or WiFi.

[0047] The engine 12 and alternator 72 may each be sized and rated such that the system 70 is capable of supplying the necessary power required by the electric motor 73 based on its speed and torque requirements. For example, where the electric motor 73 is used to drive a submersible pump 90 that is deployed in a wellbore for groundwater control purposes, the system 70 may be configured to supply a total of between 50 and 500 kilowatts (kW) of power to the electric motor 73. In examples where the submersible pump 90 deployed in a wellbore for artificial lift purposes in the petroleum industry, the system 70 may be capable of supplying a total of between 50 and 1,500 kilowatts (kW).

[0048] In one example, the first controller 80 may be configured to implement a safety feature wherein the speed of the electric motor 73 is reduced when a temperature sensor installed in the motor 73 indicates that the temperature of the motor 73 has met or exceeded a particular maximum value set by an operator of the system 70. The temperature sensor may, for example, comprise a positive temperature coefficient resistor, or similar temperature measuring device, communicatively coupled to the first controller 80. The first controller 80 may also be configured to stop the electric motor 73 altogether when the maximum temperature value is exceeded.

[0049] The control signals that are issued by the first controller 80 to the second controller 82 may comprise digital control signals. For example, the system 70 may comprise a communications bus connecting the two controllers 80, 82 together and the control signals may comprise digital machine code instructions transmitted via the communications bus. In other examples, the two controllers 80, 82 may be connected together 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 first controller 80 may be configured to issue analogue control signals to the second controller 82. The second controller 82 may also be connected to the throttle controller 76 and to the voltage regulator 74 using any one of the foregoing communication means. The second controller 82 may also be configured to send diagnostic information relating to operation of the throttle controller 76 and/or voltage controller 74 to the first controller 80, and the diagnostic information may be used by the first controller 80 to determine the motor control signals issued to the second controller 82. The second controller 82 may send the diagnostic information to the first controller 80 using any one of the foregoing communication means.

[0050] The system 70 may also comprise a communications interface 94 for connecting the first controller 80 to a remote control center or device 96. For example, the communications interface 94 may comprise a radio transceiver or network interface that enables the remote control device 96 to be connected via a LAN, WAN, WLAN, the Internet, cellular or mobile network or other computer or digital network. The first controller 80 may be connectable to an individual remote control device 96 that comprises a touch-screen visual display, or similar electronic user interface, that enables a human operator to set, activate and monitor the operation of the first controller 80 and the system 70 more generally. In other examples, the first controller 80 may be connectable to a remote control centre that contains various UI control devices that human operators may use to control and/or monitor the first controller 80 and the system 70. In examples, the system 70 may be configured such that the information that is measured and/or determined using the sensor 78, such as a current pressure, level or flow reading, is displayed on a visual display of the remote control device or control centre during use.

[0051] The first controller 80 may also be configured to transmit data relating to operating conditions or parameters of the system 70 to the remote control center or device 96. This enables the operation and performance of the system 70 to be monitored and assessed during use. The first controller 80 may also be configured to operate in accordance with control instructions received from the remote control center or device 96 via the communications interface 94. For example, the user control center or device 96 may be used by an operator to set and store a particular set point on the first controller 80 and cause the first controller 80 to operate in accordance with a control mode corresponding to the set point. For example, if the motor 73 is used to drive a submersible pump 90, the operator may input a constant water flow rate in the first controller 80 and cause the first controller 80 to enter into a pump control mode wherein the speed of the pump 90 is regulated by the system 70 to maintain the constant flow rate during use.

[0052] The first controller 80 may also be configured to transmit warnings or alerts relating to operating conditions of the system 70 to the remote control center or device 96 via the communications interface 94. For example, the first controller 80 may transmit an alert when the temperature of the electric motor 73 exceeds a particular operating range stored on the first controller 80. The first controller 80 may also be configured to transmit warnings or alerts when it predicts when particular operating conditions of the system 70 may occur or arise in the future. The first controller 80 may make such predictions based on the historical mode of operation and/or duration of operation of the system 70 that is tracked and recorded by the first controller 80. In other examples, an alert or notification may be sent to the remote device 96 when the controller 80 determines that the level of fuel in the second fuel tank 16 is below a predetermined level stored in the controller 82.

[0053] A circuit breaker (not shown) may be interconnected between the generator system 70 and the electric motor 73 that prevents the electric motor 73 from drawing too much current from the generator system 70 during use. The first controller 80 may be communicatively connected to the circuit breaker and be configured to monitor and reset the circuit breaker in accordance with programmed logic executed by the first controller 80 and/or operator instructions manually issued using the remote control centre or device 96.

[0054] As described in the foregoing paragraphs, the motor control methodology that is implemented by the system 70 is split into two functional control processes executed by two separate, cooperating system controllers 80, 82 respectively. That is, the first controller 80 serves as a master controller that implements a control loop to (i) receive information from the sensor 78, (ii) determine whether the motor 73 needs to run faster or slower based on the information and (iii) send a control signal to the second controller 82 representing a desired motor speed. The second controller 82, in turn, serves as a slave controller that controls the ECU 76 and the AVR 74 based on the control signal such that the motor 73 is caused to run at the desired speed. Implementing this cascade control methodology using two separate system controllers 80, 82 provides several practical advantages, including:

(i) If the first controller 80 ceases to operate correctly during use, then the second controller 82 may continue to operate the electric motor 73 while the first controller 80 is being repaired or replaced. For example, the second controller 82 may continue to operate the motor 73 but on a fixed speed basis, rather than a variable speed basis, during the relevant maintenance period;

(ii) If firmware embodying the control logic executed by the first controller 80 needs to be updated during use, the firmware can be updated live while the second controller 82 continues to operate the electric motor 73. Again, the second controller 82 may operate the motor 73 on a fixed speed basis during the relevant update period;

(iii) The control logic implemented by the second controller 82 may be protected using a digital key 92 independently of the control logic implemented by the first controller 80. This may allow, for example, a supplier or manufacturer of the system 70 to lock the system 70 in a fixed speed mode and only allow an end user who has the digital key 92 to unlock and use the more-sophisticated variable speed motor functionality.

[0055] In other examples, the second controller 82 may be configured to issue control instructions to the ECU 76 but not to the AVR 74. The AVR 74 may automatically control the voltage of the output current of the alternator 72 based on the frequency of the output alternating current, or based on the rotational frequency of the drive axle of the engine 12 driving the alternator 72. In such examples, the AVR 74 may control the output current such that the V/f ratio required by the motor 73 is maintained.

[0056] For the purpose of this specification, the word "comprising" means "including but not limited to", and the word "comprises" has a corresponding meaning.

[0057] 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 system for supplying fuel to an engine of an electrical generator, the system comprising: an internal fuel tank and one or more external fuel tanks; an actuable valve assembly that is fluidly connected to the engine and to the internal fuel tank, wherein the actuable valve assembly is also detachably fluidly connectable to the one or more external fuel tanks and is operatively switchable between at least a first and a second operating mode, wherein in the first operating mode the actuable valve assembly is configured to supply the fuel from the internal fuel tank to the engine, and wherein in the second operating mode the actuable valve assembly is configured to supply the fuel from at least one of the external fuel tanks to the engine; a fuel pump for pumping the fuel from the internal fuel tank and/or the one or more external fuel tanks to the engine via the actuable valve assembly; at least one sensor configured to output sensor information corresponding to a level of fuel in the at least one of the external fuel tanks, wherein the sensor is detachably connectable to the system controller; and a system controller operatively connected to the actuable valve assembly and to the fuel pump, wherein the system controller is configured to operate the fuel pump and the actuable valve assembly such that: when the sensor is disconnected from the system controller, the system controller causes the actuable valve assembly to operate in the first operating mode only; and when the sensor is connected to the system controller, in response to the sensor information the system controller causes the actuable valve assembly to operate in the second operating mode when the level of fuel is at or above a predetermined level stored in the system controller, and to operate in the first operating mode when the level of fuel is below the predetermined level.

2. The system according to claim 1, wherein the system comprises: a first hydraulic fuel circuit for circulating the fuel between the internal fuel tank and the engine; a second hydraulic fuel circuit for circulating the fuel between the at least one of the external fuel tanks and the engine; and one or more fuel injectors for injecting the fuel into the engine from the first and the second hydraulic fuel circuit, and wherein the actuable valve assembly and fuel pump are configured such that in the first and the second operating mode the fuel is circulated under pressure around, respectively, the first and the second hydraulic fuel circuit.

3. The system according to claim 2, wherein the actuable valve assembly comprises an input fuel line and an output fuel line arranged to supply the fuel to and from the fuel injectors respectively, and wherein the first hydraulic fuel circuit is provided by: the input and the output fuel line; a first fuel supply line arranged to supply the fuel from the internal fuel tank to the actuable valve assembly; and a first fuel return line arranged to return the fuel from the actuable valve assembly to the internal fuel tank.

4. The system according to claim 3, wherein the second hydraulic fuel circuit is provided by: the input and the output fuel line; a second fuel supply line arranged to supply the fuel from the at least one of the external fuel tanks to the actuable valve assembly; and a second fuel return line arranged to return the fuel from the actuable valve assembly to the at least one of the external fuel tanks.

5. The system according to claim 4, wherein the actuable valve assembly is configured such that: in the first operating mode, the actuable valve assembly fluidly connects the first fuel supply line to the input fuel line, and the first fuel return line to the output fuel line; and in the second operating mode, the actuable valve assembly fluidly connects the second fuel supply line to the input fuel line, and the second fuel return line to the output fuel line.

6. The system according to any one of the preceding claims, wherein the sensor is detachably connectable to the system controller by a control line that is provided with a plug and socket arrangement.

7. The system according to any one of the preceding claims, wherein the sensor is deployed inside and attached to the at least one of the external fuel tanks.

8. The system according to any one of the preceding claims, wherein the system comprises a second sensor connected to the system controller that is configured to output sensor information corresponding to an amount of fuel available in the internal fuel tank, and wherein the system controller is configured to stop the fuel pump from operating when the system controller determines, based on the sensor information output by the second sensor, that a level of fuel in the internal fuel tank is at or below a predetermined level stored in the system controller.

9. The system according to any one of the preceding claims, wherein the system comprises a communication means for remotely connecting the system controller to one or more remote user devices, and wherein the system controller is configured to issue an alert or notification to the one or more remote user devices by the communication means when the system controller determines that the level of fuel in the external fuel tank is below a predetermined level stored in the system controller.

10. The system according to any one of the preceding claims, wherein the system comprises: a second of the external fuel tanks; and an additional sensor detachably connectable to the system controller, wherein the additional sensor is configured to output sensor information corresponding to a level of fuel in the second of the external fuel tanks, wherein the system controller causes the actuable valve assembly to supply the fuel to the engine from the second of the external fuel tanks if the sensor information output by the additional sensor indicates that the level of fuel in the second of the external fuel tanks is at or above a predetermined level stored in the system controller.

11. A generator system, comprising: an engine; the system according to any one of the preceding claims for supplying fuel to the engine; an alternator driven by the engine to produce an alternating current, the alternator comprising a voltage regulator for controlling a voltage of the alternating current; a throttle controller for controlling a rotational speed of the engine and, therefore, frequency of the alternating current; and a generator controller configured to control the throttle controller and the voltage regulator to control the frequency and voltage of the alternating current respectively.

12. The generator system according to claim 11, wherein the generator system is connected to an electric motor, the electric motor being powered by the alternating current produced by the alternator.

13. The generator system according to claim 12, wherein the generator system comprises a further sensor, wherein the further sensor is configured to output information about an operating environment or condition of the electric motor, and wherein the generator controller is connected to the further sensor and is configured to control a speed of the electric motor by controlling the throttle controller and the voltage regulator in response to the information output by the further sensor.

14. The generator system according to claim 13, wherein the generator controller: stores at least one set point relating to an operating environment or condition of the electric motor; and in response to the information output by the further sensor, controls the speed of the electric motor such that the set point is maintained.

15. The generator system according to claim 14, wherein the electric motor operatively drives a submersible pump and the set point relates to an operating environment or condition of the submersible pump.

16. The generator system according to claim 15, wherein the set point is one of a set of values corresponding to a desired fluid pressure, a desired fluid flow rate and a desired fluid level.

17. The generator system according to any one of claims 13 to 16, wherein the generator controller comprises a first controller connected to a second controller, wherein the first controller is connected to the further sensor and is configured to generate and send control signals to the second controller based on the information output by the further sensor, and wherein the second controller is connected to the throttle controller and to the voltage regulator and is configured to control the speed of the electric motor by controlling the throttle controller and the voltage regulator in response to the control signals.

18. The generator system according to claim 17, wherein the control signals sent to the second controller comprise a target speed of the electric motor, and wherein the second controller causes the electric motor to operate at the target speed.

19. The generator system according to any one of claims 11 to 18, wherein the generator controller is integral with the system controller.