Power flow optimization for mining machines

Abstract

A method of electrical power distribution of an electrically powered mining machine (2) is provided, wherein the mining machine comprises a first power converter (102), the input of which being connectable to an external power source (10), a control unit (106) adapted to control the operation of the first power converter (102), an internal power source (130), an electric drive unit (110, 120), and a bus (104) interconnecting an output of the first power converter (102), the internal power source (130), and an input of the electric drive unit (110, 120). The method comprises the following steps: determining a control parameter different from a parameter obtained from a direct measurement of a load demand of the electric drive unit (110; 120), and controlling the first power converter (102) in dependence of the control parameter. A scalable, robust, and simple power distribution in a mining machine without dependencies on load demand measurements is thereby achieved. An electrically powered mining machine with a control unit (106) adapted to perform the method is also provided.

Description

POWER FLOW OPTIMIZATION FOR MINING MACHINESTechnical field

[0001] The present invention relates generally to the field of electrical power distribution at electrically powered mining and construction machines, and more specifically to a method of electrical power distribution in an electronic control system at an electrically powered mining or construction machine and such an electronic control system.Background art

[0002] Mining and construction machines, such as rock drilling rigs, are used for several purposes, such as exploration drilling, which aims to identify the location and quality of a mineral, and production mining and quarrying, used in the production-cycle for mining or construction . Other application areas are road construction and structural construction.

[0003] Traditionally, mining and construction machines have been driven by combustion engines. However, in recent years, growing environmental concerns have driven the mining industry to reducing or phasing out the traditional combustion engines to reduce and eventually stop the emission of greenhouse gases from fossil fuels.

[0004] In the mining industry the solution is focused on electrification of the machine park. Electrification has some challenges, mainly in the capacity of today’s electric batteries, especially in a rock drilling rig, where the demands for power and energy are high during rock drilling. This is solved in that the rock drilling rig can be connected to an external electrical network when performing its rock drilling work cycle.

[0005] A proposed solution to such problems is the substitution of the combustion engine with an electric motor, driven partly by an energy storage, such as an electric battery and / or a connection to an external electrical network. When the rock drilling rig performs its work cycle with the rock drilling machine, the rockdrilling rig must be connected to an external electrical network for powering the rock drilling rig. This solution does eliminate direct emissions of CO2 and usage of fossil fuels but does however also provide several drawbacks. One exemplary drawback is the availability of an external electrical network with sufficient power capacity at the work site.Summary of invention

[0006] An object of the present invention is to provide a scalable, robust, and simple power distribution in a mining machine without dependencies on load demand measurements.

[0007] According to a first aspect of the invention, there is provided method of electrical power distribution of an electrically powered mining machine, the mining machine comprising a first power converter, the input of which being connectable to an external power source, a control unit adapted to control the operation of the first power converter, an internal power source, an electric drive unit, and a bus interconnecting an output of the first power converter, the internal power source, and an input of the electric drive unit, the method comprising the following steps: determining a control parameter different from a parameter obtained from a direct measurement of a load demand of the electric drive unit, and controlling the first power converter in dependence of the control parameter. A scalable, robust, and simple power distribution in a mining machine is thereby provided without dependencies on load demand measurements.

[0008] In a preferred embodiment, the control parameter is an operating mode, a voltage on the bus, a voltage of the external power source, a state of charge of the internal power source, a failure detection signal for the external power source, a failure detection signal for the internal power source, a failure detection signal for the electric drive unit, a power threshold for the input of the first power converter, or a charge threshold for the internal power source.

[0009] In a preferred embodiment, the operating mode is drilling, idling, rod handling, or tramming.

[0010] In a preferred embodiment, the method comprises the additional step of providing a prediction of a load demand for the electric drive unit, preferably depending on an operating mode, and controlling the first power converter in dependence of the prediction.

[0011] In a preferred embodiment, the bus preferably is a DC bus, and the first power converter supplies a rated current from the external power source to the electric drive unit when the voltage of the bus is lower than a maximum predetermined limit.

[0012] In a preferred embodiment, the bus preferably is a DC bus, and the mining machine comprises a second power converter interconnecting the internal power source and the bus, and a second control unit adapted to control the operation of the second power converter, wherein the method comprises the step of controlling the voltage of the bus to a predetermined voltage set point by means of the second power converter.

[0013] In a preferred embodiment, the method comprises the additional step of communicating, between the first and second control units, information to adapt any new status, planned changes, coordination, or change of common network parameter reference.

[0014] In a preferred embodiment, the first power converter is controlled based on grid forecast and / or task schedule of the electrically powered mining machine.

[0015] In a preferred embodiment, the method comprises the additional step of controlling the first power converter by means of operator command.

[0016] According to a second aspect of the invention, an electrically powered mining machine is provided comprising a first power converter, the input of which is connectable to an external power source, a control unit adapted to control the operation of the first power converter, an internal power source, an electric drive unit, and a bus interconnecting an output of the first power converter, the internal power source, and an input of the electric drive unit, wherein the control unit is adapted to perform the method as described above.In a preferred embodiment, a rating of the first power converter is lower than a maximum power level of charging the internal energy source.

[0017] In a preferred embodiment, a second power converter is provided between the internal power source and the bus, wherein a rating of the second power converter preferably is at least a maximum power level for powering the electric drive unit. In one embodiment, an output of the first power converter is connected to a point between the internal power source and the second power converter.

[0018] In a preferred embodiment, the electric drive unit comprises an electric motor drive, an electric motor connected to an output of the electric motor drive, and a load device, preferably a compressor or a hydraulic pump, adapted to be driven by the electric motor.

[0019] In a preferred embodiment, the internal energy source is an electric battery, a super capacitor, or a fuel cell, or a combination thereof.

[0020] According to a third aspect of the invention, a non-transitory computer- readable storage medium is provided, that stores a program configured to execute the method as described above in an electrically powered mining machine.

[0021] According to a fourth aspect of the invention, a computer program product is provided comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method as described above in an electrically powered mining machine.Brief description of drawings

[0022] The invention is now described, by way of example, with reference to the accompanying drawings, in which:Fig. 1 shows a schematic view of a mining and construction machine in the form of a surface drilling rig that is electrified and has the possibility of connecting to an electrical grid;Fig. 2 shows a simplified block diagram of an exemplary electric drive system in a mining machine as shown in Fig. 1 ;Fig. 3 shows a simplified block diagram of an alternative exemplary electric drive system in a mining machine as shown in Fig. 1 ;Fig. 4 shows a simplified block diagram of another alternative exemplary electric drive system in a mining machine as shown in Fig. 1 ;Figs. 5a and 5b show schematic diagrams of the interaction between energy supply modes and electric operating states.Description of embodiments

[0023] In the following, a detailed description of a method of electrical power distribution of an electrically powered mining or construction machine and a mining machine with a control system arranged to perform the method according to the present invention is presented.

[0024] The term “mining machine” should in the context of this application be construed broadly and include drilling rigs, particularly rock drilling rigs, but also production, exploration, excavation, and construction rigs / machines for surface and underground applications.

[0025] When reference is made to a “power source”, it should be understood that reference is made to a source of electrical power, unless explicitly stated otherwise.

[0026] In the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. It will be appreciated that these figures are for illustration only and do not in any way restrict the scope of the present disclosure.

[0027] Fig. 1 shows a schematic representation of a mining machine in the form of a rock drilling rig, generally designated 2. The rock drilling rig 2 comprises a carriage 4 and a rock drill machine 6 attached to the front of the carriage 4. Therock drilling machine 6 is arranged on and connected to the carriage 4 by means of a boom 8, so that the rock drilling machine 6 can be arranged in different positions in relation to the carriage 4 and to the rock to be drilled. Together, the carriage 4, the rock drilling machine 6 and the boom 8 form the main part of the rock drilling rig 2. The carriage 4 is further provided with propulsion means 9, such as wheels or continuous track and propulsion equipment.

[0028] The rock drilling rig 2 further comprises an electric drive system 100. The rock drilling rig 2 is provided with operative power from either an external energy source, not shown in Fig. 1 , via a cable interface 12, preferably comprising a circuit breaker, or an internal energy source, such as an electric battery, a super capacitor, or a fuel cell, or a combination thereof, comprised in the electric drive system 100. Operative power is power that either powers the propulsion means 9 and / or the rock drilling machine 6. When the rock drilling rig 2 is operated, a control unit of the electric drive system 100 is configured to selectively control operating power from the external energy source or the internal energy source, as will be described below. A work cycle normally comprises a plurality of work tasks. The control unit is further configured to selectively charge the internal energy source with energy from the external electrical source, as will be described below.

[0029] An overall diagram of the electric drive system 100 of the mining machine of Fig. 1 is shown in Fig. 2. The electric drive system comprises a power converter 102, the input of which is connectable to an external power source 10, such as a main grid supply, via the cable interface 12. The output of the power converter 102 is connected to a bus 104 adapted to provide electric power to one or more electric motor units 110, 120 of the mining machine. This bus 104 can be either a DC bus or an AC bus. In the present example, a first electric drive unit 110 comprises a first electric motor 114 adapted to drive a load in the form of a compressor 116. For controlling the operation of the first electric motor 114, a first motor drive 112 is provided between the bus 104 and the first electric motor 114. Correspondingly, a second electric drive unit 120 comprises a second electric motor 124 adapted to drive a load in the form of one or more hydraulic pumps 126.For controlling the operation of the second electric motor 124, a second motor drive 122 is provided between the bus 104 and the second electric motor 124.

[0030] An internal power source 130 is provided for powering the motor drives 112, 122. The internal power source 130 is connected to the bus 104 and via this bus to the electric drive units 110, 120. The internal power source can be any kind of electric power storage, such as a battery, a capacitor, a super capacitor etc.

[0031] In a preferred embodiment, a rating of the power converter 102 is lower than a maximum power level of charging the internal energy source 130. In this way, the risk of overloading the internal energy source 130 is minimized.

[0032] This general description of the electric drive system 100 is applicable both for AC application and DC application, and the different parts thereof are designed accordingly. For example, if the external power source is an AC network and the bus 104 is a DC bus, the power converter 102 is designed as an AC / DC converter.

[0033] Finally, a control unit 106 is connected to the power converter 102 for controlling the operation thereof. A non-transitory computer-readable storage medium is provided that stores a program configured to execute a method of electrical power distribution as described below. Thus, a computer program product comprising instructions which, when the program is executed by a computer, such as the control unit 106, cause the computer to carry out the above- mentioned method of electrical power distribution in a mining machine.

[0034] A method of electrical power distribution of an electrically powered mining machine will now be described in detail. In this method, the supply of the power demand of the electric drive units 110, 120 is autonomously distributed between the external power source 10 and the internal power source 130 without measuring the power demands of the electric drive units 110, 120. In other words, the control unit 106 is not directly connected to the loads 116, 126 for measuring the current load thereon. This is achieved with decentralized control of the power converter 102.

[0035] The method of electrical power distribution initially involves determining a control parameter different from a parameter obtained from a direct measurement of a load demand of the electric drive units 110, 120. The power converter 102 is then controlled in dependence of the control parameter.

[0036] This decentralized control of the power converter 102 can be implemented in different ways. One control parameter is the selected operating mode, such as drilling, idling, rod handling, or tramming.

[0037] In one embodiment, the output of the power converter 102 is controlled with reference to a common network parameter, such as the voltage of the bus 104 or a voltage at the AC network, i.e., the external power source 10.

[0038] In one embodiment, the power distribution between the external power source 102 and the internal power source 130 is further controlled by limiting the power supplied by the external power source 10. Alternatively or additionally, the control parameter is associated with a rating storage of the internal power source 130. This can be a charge threshold for the internal power source 130.

[0039] In one embodiment, the power distribution between the external power source 102 and the internal power source 130 is further influenced with threshold for activations and deactivation of power supply by at least one of the external power source 10 and the internal power source 130.

[0040] In one embodiment, the power distribution between the external power source 10 and the internal power source 130 is controlled based on measurement data from the external power source 10 and / or the internal power source 130. This measurement data can for example indicate low grid voltage of the external power source 10, such as a temporary low voltage of the grid, or a state of charge (SoC) of the internal power source 130, such as a low SoC of a battery.

[0041] In one embodiment, the power distribution between the external power source 102 and the internal power source 130 is further controlled based on a detection of failure. This failure could be for example a failure for the externalpower source 10, i.e., a grid fault, or a failure for the internal power source 130, such as a faulty battery. The fault can also be in the electric drive unit(s) 110, 120.The decentralized control of power supply from the external power source 10, such as a main grid, can request for change in power output profile from internal power source 130, such as a battery. This could be useful to avoid transient overshoots by limiting the power output during maintenance, for example. This could be the case where the operator can initiate change in power sharing. For example a planned maintenance of grid or internal energy storage can be done by first moving the power supply to the second source.

[0042] The decentralized control can change the reference value of the common network parameters, such as a DC voltage reference on the bus 104, during abnormal conditions.

[0043] The decentralized control can change the power distribution ratio by operator command. Alternatively or additionally, the decentralized control for power distribution ratio can be based on grid forecast and / or task schedule of the electrically powered mining machine 2. This is illustrated in Figs. 5a and 5b. Fig. 5a illustrates a decentralized way to change power sharing from the internal power source with change of power to voltage control slopes as well as change in voltage reference. In Fig. 5b, the curve indicates predicted load demand based on schedule, wherein in time interval A the plan is for power from only the first energy source 10, i.e., from the grid, in time interval B the plan is for power both from the external power source 10 and the internal power source 130, and in time interval C the plan is for charging the internal power source 130.

[0044] An additional step of providing a prediction of a load demand for the electric drive system 110 can be implemented. This prediction preferably depends on an operating mode, and the power converter 102 is then controlled in dependence of this prediction.

[0045] One way of implementing the method is to control the power converter102 to supply a maximum rated current from the external power source 10 to theelectric drive units 110, 120 when the voltage of the bus 104, preferably a DC voltage is lower than a maximum predetermined limit.

[0046] It will be appreciated that a combination of control parameters can be used for controlling the power converter 102.

[0047] In an alternative embodiment of the electric drive system 100 of the mining machine, see Fig. 3, a second power converter 132 is provided between the internal power source 130 and the bus 104. In this way, the charging and discharging of the internal power source 130 can be separately controlled. To this end, a second control unit 136 is provided for controlling the second power converter 132. This second control unit 136 can be connected to the control unit 106 for communication between these control units. Alternatively, instead of providing a separate control unit 136 for the second power converter 132, the control unit 106 can be connected to the second power converter and thereby control the operation of both the power converter 102 and the second power converter 132. In a preferred embodiment, a rating of the second power converter 132 is at least a maximum power level for powering the electric drive unit(s) 110, 120.

[0048] In yet an alternative embodiment of the electric drive system 100 of the mining machine, see Fig. 4, the power converter 102 is not directly connected to the bus 104. As in the embodiment of Fig. 3, a second power converter 132 is provided between the internal power source 130 and the bus 104. However, the output of the power converter 102 is connected to a point between the internal power source 130 and the second power converter 132. In this embodiment, the power converter 102 is preferably rated lower than the maximum power level of recharging the internal power source 130.

[0049] During operation, the power converter 102 can be controlled to maintain the voltage between the internal power source 130 and the second power converter 136 to a set point under any condition of the drilling rig, i.e. , wherein the operating mode is drilling, idling, rod handling, tramming etc. The second power converter 136 then controls the voltage on the bus 104 to a set point. With thisconfiguration, the second power converter 132 is preferably rated to handle a maximum power demand of the mining machine.

[0050] In both the embodiment of Fig. 3 and that of Fig. 4, the control units 106, 136 preferably communicate to adapt any new status, planned changes, coordination, change of common network parameter reference etc.

[0051] Although the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and the invention is not limited to the disclosed embodiments. For example, two electric drive units have been included in in the examples of an electric drive system according to the invention. It will be appreciated that the inventive idea is applicable also to electric drive systems with a single electric drive unit or with three or more electric drive units.

Claims

CLAIMS1 . A method of electrical power distribution of an electrically powered mining machine (2), the mining machine comprising a first power converter (102), the input of which being connectable to an external power source (10), a control unit (106) adapted to control the operation of the first power converter (102), an internal power source (130), an electric drive unit (110, 120), and a bus (104) interconnecting an output of the first power converter (102), the internal power source (130), and an input of the electric drive unit (110, 120), the method comprising the following steps:- determining a control parameter different from a parameter obtained from a direct measurement of a load demand of the electric drive unit (110; 120), and- controlling the first power converter (102) in dependence of the control parameter.

2. The method according to claim 1 , wherein the control parameter is- an operating mode,- a voltage on the bus (104),- a voltage of the external power source (10),- a state of charge of the internal power source (130),- a failure detection signal for the external power source (10),- a failure detection signal for the internal power source (10),- a failure detection signal for the electric drive unit (110),- a power threshold for the input of the first power converter (102), or- a charge threshold for the internal power source (130).

3. The method according to claim 2, wherein the operating mode is drilling, idling, rod handling, or tramming.

4. The method according to any one of claims 1-3, comprising the additional step of providing a prediction of a load demand for the electric drive unit (110), preferably depending on an operating mode, and controlling the first power converter (102) in dependence of the prediction.

5. The method according to any one of claims 1-4, wherein the bus (104) preferably is a DC bus, and wherein the first power converter (102) supplies a rated current from the external power source (10) to the electric drive unit (110; 120) when the voltage of the bus (104) is lower than a maximum predetermined limit.

6. The method according to any one of claims 1-5, wherein the bus (104) preferably is a DC bus, and wherein the mining machine comprises a second power converter (132) interconnecting the internal power source (130) and the bus (104), wherein the method comprises the step of controlling the voltage of the bus (104) to a predetermined voltage set point by means of the second power converter (132).

7. The method according to claim 6, comprising the additional step of communicating, between the first and second control units (106, 136), information to adapt any new status, planned changes, coordination, or change of common network parameter reference.

8. The method according to any one of claims 1-7, wherein the first power converter (102) is controlled based on grid forecast and / or task schedule of the electrically powered mining machine (2).

9. The method according to any one of claims 1-8, comprising the additional step of controlling the first power converter (102) by means of operator command.

10. An electrically powered mining machine comprising a first power converter (102), the input of which is connectable to an external power source (10), a control unit (106) adapted to control the operation of the first power converter (102), an internal power source (130), an electric drive unit (110; 120), and a bus (104) interconnecting an output of the first power converter (102), the internal power source (130), and an input of the electric drive unit (110, 120), wherein the control unit (106) is adapted to perform the method of any of claims 1- 9.11 . The electrically powered mining machine according to claim 10, wherein a rating of the first power converter (102) is lower than a maximum power level of charging the internal energy source (130).

12. The electrically powered mining machine according to claim 10 or 11 , comprising a second power converter (132) provided between the internal power source (130) and the bus (104), wherein a rating of the second power converter (132) preferably is at least a maximum power level for powering the electric drive unit (110, 120).

13. The electrically powered mining machine according to claim 12, wherein an output of the first power converter (102) is connected to a point between the internal power source (130) and the second power converter (132).

14. The electrically powered mining machine according to any one of claims 10-13, wherein the electric drive unit (110, 120) comprises an electric motor drive (116, 126), an electric motor (112, 122) connected to an output of the electric motor drive (116, 126), and a load device (114, 124), preferably a compressor or a hydraulic pump, adapted to be driven by the electric motor (112, 122).

15. The electrically powered mining machine according to any one of claims 10-14, wherein the internal energy source (130) is an electric battery, a super capacitor, or a fuel cell, or a combination thereof.

16. A non-transitory computer-readable storage medium that stores a program configured to execute the method of any one of claims 1 to 9 in an electrically powered mining machine according to claim 10.

17. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of any one of claims 1 to 9 in an electrically powered mining machine according to claim 11.

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