Charging of electrical mining machines

Abstract

A method of controlling an electrical charging station (20) in a mining environment is provided. The electrical charging station (20) is connected to an electrical network (10) and is connectable to an electrical storage (30), preferably of a mining machine (2), to provide a charging current (Icharge) to the electrical storage (30). The method comprises the following steps: determining a remote voltage (Vremote) in the electrical network at a reference position remote from the charging station, determining a local voltage (Vlocal) at the charging station (20), determining a voltage difference (Vdiff) between the remote voltage (Vremote) and the local voltage (Vlocal), and controlling the charging current (Icharge) based on the voltage difference (Vdiff). Thereby, the quality of the electrical network can be maintained. An electrical charging station (20) operating according to the method is also provided.

Description

CHARGING OF ELECTRICAL MINING MACHINESTechnical field

[0001] The present invention relates generally to charging of electrical mining machines and more particularly to a method of controlling an electrical charging station in a mining environment as well as an electrical charging station operating according to the method.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] Mining is power consuming and electricity grids in mines are often of limited capacity and varying power quality. The mining environment causes both technical and economical limitations that need to be considered when an electricity grid is constructed to a mine. Furthermore, the load in an electricity grid in a mineis typically variable because different tools and machines are recharged and used in irregular intervals.

[0006] A further characteristic with mines is that they may be in a remote location, causing problems with the quality of the electrical power at the mining site.

[0007] There is therefore a need for a solution mitigating or eliminating the problems of varying power quality at a mining site.Summary of invention

[0008] An object of the present invention is to provide a charging solution which can help to improve the quality and stability of an electrical network providing charging power.

[0009] According to a first aspect of the invention, a method of controlling an electrical charging station in a mining environment is provided, the electrical charging station being connected to an electrical network and connectable to an electrical storage, preferably of a mining machine, to provide a charging current to the electrical storage, the method comprising the following steps: determining a remote voltage in the electrical network at a reference position remote from the charging station, determining a local voltage at the charging station, determining a voltage difference between the remote voltage and the local voltage, and controlling the charging current (Icharge) based on the voltage difference.

[0010] In a preferred embodiment, the remote voltage is determined by measuring the voltage at the reference position. Alternatively, the remote voltage is determined by calculating a virtual voltage at the reference position.

[0011] In a preferred embodiment, the step of determining a local voltage comprises determining a local voltage at at least two different charging stations connected to different areas of the electrical network.

[0012] In a preferred embodiment, the local voltage of a second charging station is used as remote voltage for a first charging station.

[0013] In a preferred embodiment, based on the voltage difference of two different reference positions in a first and a second electrical network, respectively, the charging station is disconnected from the first network and connected to the second network.

[0014] In a preferred embodiment, the method comprises a step of providing an auxiliary energy storage connected to or comprised in the charging station.

[0015] In a preferred embodiment, controlling the charging current is additionally based on the charge level of the auxiliary energy storage.

[0016] In a preferred embodiment, the method comprises a step of controlling energy storage current to / from the auxiliary energy storage based on the voltage difference and the required charging current.

[0017] In a preferred embodiment, the method comprises a step of deactivating controlling the charging current based on the voltage difference if the charge level of the energy storage is below a predetermined threshold value.

[0018] In a preferred embodiment, a plurality of charging stations is provided, the method comprising the step of assigning a priority to each charging station of the plurality of charging stations based on the voltage difference, and to limit the charging current for charging stations with lower priority.

[0019] In a preferred embodiment, the priority of a first station is changed to a second station based on the voltage difference for each charging station.

[0020] In a preferred embodiment, the charging station is provided with a plurality of charging terminals, each charging terminal being connectable to an electrical storage of a mining machine to provide a charging current for the electrical storage, wherein each of the charging currents is controlled based on the voltage difference.

[0021] In a preferred embodiment, the method comprises a step of changing the reference position from a first reference position with a first remote voltage to asecond reference position different from the first reference position with a second remote voltage.

[0022] In a preferred embodiment, the charging current is controlled inversely linear to the voltage difference. Alternatively, the charging current is controlled inversely stepwise to the voltage difference.

[0023] In a preferred embodiment, the method comprises a step of determining an acceptable bandwidth of the local voltage based on the voltage difference, and, if the local voltage is outside the acceptable bandwidth, controlling the charging current so that the local voltage is inside the acceptable bandwidth.

[0024] In a preferred embodiment, the acceptable bandwidth of the local voltage is adjusted based on the voltage difference.

[0025] In a preferred embodiment, the electrical network is a DC network.

[0026] In a preferred embodiment, the reference position is any of the following: the other end of the feeder, a substation, and / or a position in an electrical network different from the electrical network to which the charging station is connected.

[0027] According to a second aspect of the invention, an electrical charging station for use in a mining environment is provided, the electrical charging station being connectable to an electrical network and connectable to an electrical storage of a mining machine to provide a charging current to the electrical storage, wherein the electrical charging station comprises control means for controlling the electrical charging station according to the above described method.

[0028] 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 above described method in an electrical charging station according to the second aspect of the invention.

[0029] According to a fourth aspect of the invention, a computer program product is provided comprising instructions which, when the program is executedby a computer, cause the computer to carry out the method as described above in an electrical charging station according to the second aspect of the invention.Brief description of drawings

[0030] 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 network;Fig. 2 is a schematic diagram of a charging station connected to an electrical network and to a mining machine;Figs. 3 and 4 are schematic diagrams of charging stations in two different locations connected to different areas of an electrical network;Fig. 5 is a schematic diagram of a charging station connected to two different electrical networks;Fig. 6 is a schematic diagram of a charging station connected to an electrical network and also to a local energy storage;Fig. 7 is a schematic diagram of two charging stations with different priorities;Fig. 8 is a schematic diagram of a charging station connected to an electrical network and comprising a plurality of charging terminals;Fig. 9 is a schematic diagram of an electrical network in which several reference positions are provided;Figs. 10a and 10b are diagrams showing examples of how a charging current is controlled based on a voltage difference;Figs. 11a and 11 b are diagrams showing how an acceptable bandwidth is determined;Fig. 12 is a diagram showing more in detail charging stations connected to an electrical network and mining machines to be charged with an onboard charger;Fig. 13 is a diagram showing more in detail charging stations connected to an electrical network and mining machines to be charged with an off-board charger; andFig. 14 is a flow chart of the method according to the invention.Description of embodiments

[0031] In the following, a detailed description of a method of controlling an electrical charging station in a mining environment and such an electrical charging station will be given.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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. The rock 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 therock drilling rig 2. The carriage 4 is further provided with propulsion means 9, such as wheels or continuous track and propulsion equipment.

[0036] 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, The rock drilling rig 2 also comprises an internal energy source 30, such as an electric battery, a super capacitor, or a fuel cell, or a combination thereof. 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, the 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.

[0037] The cable interface 12 is also used when the internal energy source is charged. During charging, the internal energy source 30 is thus connected to an external electrical network via a charging station, as will be described below.

[0038] Referring now to Fig. 2, a basic configuration of an electrical charging station 20 is shown. The electrical charging station 20 is connected to an electrical network 10 and to an electrical storage 30 of a mining machine, see Fig. 1 , to provide a charging current Icharge to the electrical storage 30. The electrical charging station 20 comprises control means for controlling the electrical charging station 20 as will be described below.

[0039] The electrical network 10 is normally a network provided at a mining site for the provision of electricity to mining machines and other functions in a mine, but the inventive idea is applicable to any kind of electrical network. In Fig. 2, only part of an electrical network is shown, comprising a power cable interconnecting a local access position to a position in the network remote from the local access position. In this context, the term “remote” should be interpreted as a position atleast 100 meters, and preferably at least 1000 meters, from the local access position. The electrical network 10 can be either an AC network or a DC network.

[0040] As shown in the figure, the local access position has a voltage designated Vlocal and the remote position has a voltage designated Vremote. It will be realized that as in all electrical networks, there is a voltage drop in the cables due to the impedance of the cables. This voltage drop results in an unpredictable local voltage Vlocal affecting the operation of devices connected to the local access position, such as a charger for the battery of a mining machine.

[0041] According to the invention, the electrical charging station 20 provided in a mining environment is therefore controlled as follows, see Fig. 14. In a first step 102, the electrical charging station 20 is first connected to the electrical network 10, as is conventional, by means of a plug and socket or the like. The electrical charging station 20 is also connected to an internal electrical storage 30 of a mining machine in a second step 104. This electrical storage 20 can be an internal electrical storage of a mining machine 2, as described above with reference to Fig.1 , but it can also be an electrical storage which is temporarily removed from a mining machine for charging or another electrical storage, such as a battery providing electrical power to a lighting system. When the electrical charging station is connected to the electrical storage 30, it provides a charging current Icharge to the electrical storage 30.

[0042] During charging, the remote voltage Vremote in the electrical network at the reference position remote from the charging station is determined in a third step 106. This voltage can be determined in different ways. In one embodiment, the remote voltage Vremote is determined by measuring the voltage at the reference position by means of a measuring instrument or the like. The measurement uses a common reference voltage in the network as a base for determining the voltage.

[0043] As an alternative to measuring the voltage, a virtual voltage can be calculated. The virtual voltage can for example be the rated voltage of the network. In other words, 1 per unit or can be set to a value close to rated voltage e.g. 0.95 perunit. In ideal situation the virtual voltage is 1 per unit but in a highly loaded network that can be lowered within regulation limits. The operator can select the value based on network operation, loading at charger and slope at which charging power is reduced based on voltage difference.

[0044] The voltage Vremote at the remote position can be communicated to the electrical charger 20 in different ways, such as by means of wireless communication or via a mobile communication network, such as a 5G network. Alternatively, it is communicated by wire, either by means of a dedicated wire or for example as signals superimposed on the voltage of the electrical power network 10.

[0045] The local voltage Vlocal is also determined in a fourth step 108. This voltage can be determined in different ways, but it is preferably determined by measuring the voltage at the local reference position by means of a measuring instrument or the like. This measuring instrument can also be integrated into the charging station 20. Like at the remote position, the measurement at the local position uses the neutral in the network as a base for determining the voltage. In this way, a voltage difference Vdiff between the remote voltage Vremote and the local voltage Vlocal can be determined in a fifth step 110. This voltage difference Vdiff is used as a basis for controlling the charging current Icharge in a sixth step 112.

[0046] In an alternative embodiment, see Fig. 3, a plurality of charging stations, in the figure two charging stations 20a, 20b, is provided, each connected to an electrical storage 30a, 30b, respectively. The charging stations 20a, 20b are connected to different areas of the electrical network 10. In this embodiment, the local voltages Vlocall and Vlocal2, respectively, are determined at each charging station 20a, 20b. As in the embodiment described above with reference to Fig. 2, the voltage Vremote at the remote position is also determined and is used for calculating the voltage difference Vdiff for each of the charging stations 20a, 20b. In other words, the voltage difference between Vlocall and Vremote is used as a basis for controlling the first charging station 20a and the voltage differencebetween Vlocal2 and Vremote is used as a basis for controlling the second charging station 20b.

[0047] Elaborating on the configuration described above with reference to Fig. 3, instead of determining the voltage as a position in the electrical network 10 remote from the charging stations 20a, 20b, the voltage at one of the charging stations can be used as remote voltage Vremote, see Fig. 4. In the figure, the local voltage Vlocal of the second charging station 20b is used as remote voltage Vremote for the first charging station 20a.

[0048] Turning now to Fig. 5, a configuration is shown wherein a single charging station 20 is provided. In this embodiment, a remote voltage is determined at plurality of different remote positions, in the shown example two different remote positions, resulting in two different remote voltages Vremotel and Vremote2, respectively. The two remote positions can be disconnected from the local access position at the charging station by means of a respective circuit breaker 12a, 12b. In this example, the first reference position is in a first electrical network 10a, and the second reference position is in a second electrical network 10b. However, the two reference positions could also be located in one single electrical network.

[0049] Based on the voltage difference of the two different reference positions in the first and second electrical networks 10a, 10b, the charging station 20 is disconnected from one of the networks, for example the first network 10a, and is connected to another network, for example the second network 10b.Correspondingly, the voltage reference is changed from the first to the second network. In this way, the load on different electrical networks can be balanced, reducing voltage drops and instability in the electrical networks.

[0050] In an alternative embodiment, an auxiliary energy storage 22 is connected to or comprised in the charging station 20, see Fig. 6. In other words, the auxiliary energy storage 22 is a different energy storage from the electrical storage 30 described above. The auxiliary energy storage 22 may be used as a backup or as a compliment to the electrical network 10, as will be described below.As with the energy storage 30, the auxiliary energy storage 22 may be a battery, a super capacitor etc.

[0051] When controlling the charging current Icharge to the energy storage 30, the charge level of the auxiliary energy storage 22 may be used as a parameter in the control of the charging current. Alternatively or additionally, the energy storage current to / from the auxiliary energy storage 22 can be controlled based on the voltage difference Vdiff determined for the charging station 20 to which the auxiliary energy storage 22 is connected.

[0052] As described above, the charging current Icharge is controlled based on the voltage difference Vdiff. However, this control can be deactivated if the charge level of the auxiliary energy storage 22 is below a predetermined threshold value. In this way, the internal energy storage will be charged with full power in case of low state of charge. Alternatively or additionally, the deactivation can be time dependent, such as be deactivated for some time and if oscillation grows it is activated again.

[0053] In the case a plurality of charging stations is provided, such as in the embodiment described above with reference to Fig. 3, each charging station of the plurality of charging stations can be assigned a priority. In this way, the mining machine needed most can be charged before other mining machines. This is schematically shown in Fig. 7, where the dashed arrow indicates that the second charging station 20b is given priority over the first charging station 20a. The charging current Icharge for charging stations with lower priority is then preferably limited. In a preferred embodiment, the priority of the first station 20a is changed to the second station 20b based on the voltage difference for each charging station. It is preferred to limit the charging power for charging stations with lower priorities, if necessary to maintain a healthy electrical network. In this way, a better balanced electrical network 10 can be achieved.

[0054] In one embodiment, see Fig. 8, the charging station 20 is provided with a plurality of charging terminals, each charging terminal being connectable to an electrical storage 30a, 30b of a mining machine or other electrical storage. In thisway, a charging current Ichargel , Icharge2 can be provided for a plurality of electrical storages, wherein each of the charging currents preferably is controlled based on the above described voltage difference Vdiff. In this way, a large number of energy storages can be charged simultaneously without having to provide a large number of charging stations 20.

[0055] It has been described above how remote voltage Vremote is determined as a step of determining a voltage difference Vdiff. In one embodiment, the reference position is changed from a first reference position with a first remote voltage Vremotel to a second reference position different from the first reference position with a second remote voltage Vremote2, see Fig. 9. This change can be due to changes in operation conditions of the electrical network 10 or for other reasons, such as changes in network configurations.

[0056] How the determined voltage difference Vdiff can be used when controlling the charging current Icharge will now be explained, initially with reference to Figs. 10a and 10b. It is there shown how there is inverse correlation between the charging current Icharge and the voltage difference Vdiff. This means that with a low voltage difference Vdiff, the charging current can be high.Correspondingly, if the voltage difference Vdiff is high, then there charging current Icharge will be low. In other words, if the electrical network 10 is heavily loaded, i.e. , the voltage difference Vdiff is high, then you should limit the charging current Icharge to maintain stability in the electrical network 10. In Fig. 10a there is shown how this correlation is inversely linear. However, other correlations are also possible, as shown in Fig. 10b, where the correlation is inversely stepwise. It can be also nonlinear function, i.e., a curve, or a combination of multiple linear functions, i.e., multiple nonlinear curves.

[0057] Not only a heavy load on the electrical network, resulting in a low voltage level at the charging station 20, could be a problem. Another problem is a widely varying voltage level at the charging station 20, which can result in unpredictable charging or damage to components and energy storages. It is therefore preferred to determine an acceptable bandwidth of the local voltage Vlocal based on thevoltage difference, and, if the local voltage Vlocal is outside the acceptable bandwidth, to control the charging current so that the local voltage Vlocal is inside this acceptable bandwidth. This is illustrated in Fig. 11a, where there is a rated voltage Vrated, such as 230 Volts or 380 Volts AC or 18 or 24 Volts DC. Three bandwidths are also illustrated: a first, large bandwidth Vbandwidthl of for example Vrated +- 15 %, a second, medium bandwidth Vbandwidth2 of for example Vrated +- 10 %, and a third, small bandwidth Vbandwidth3 of for example Vrated +- 5 %.

[0058] It is preferred that the acceptable bandwidth of the local voltage Vlocal is adjusted based on the voltage difference Vdiff. This is illustrated in Fig. 11 b, where a low voltage difference Vdiff allows for a broad bandwidth and vice versa.

[0059] In one embodiment, the acceptable bandwidth of the local voltage Vlocal at the charging station 20 is adjusted based on the voltage difference Vdiff which has been determined.

[0060] It has been described that the inventive idea is applicable to both electrical AC and DC networks. It is also applicable to both onboard charging, i.e. , where the charger is provided in the mining machine, the battery of which is to be charged, and off-board charging, i.e., where the charger is provided in the charging station. The general designs of the different solutions will be described below with reference to Figs. 12 and 13.

[0061] Fig. 12 illustrates a design with onboard charging from an electrical AC or DC network. In the figure, the charging station 20 is connected to an electrical network 10, as described above with reference to various embodiments. For determining the local voltage Vlocal, a voltage meter 23 is provided at or near the input of the charging station 20 where it is connected to the electrical network 10. A charging station controller 26 is provided to control the operation of the charging station 20 and to communicate with an onboard controller 32 in the mining machine 2. A contactor 28 is preferably provided between the input and the output of the charging station 20 to shut off charging if a control scheme so directs, such as based on the voltage difference Vdiff of an electrical AC network 10.

[0062] An internal voltage source 22 is optionally provided in the charging station, as described above with reference to Fig. 6. The internal voltage source 22 is connected to the mining machine 2 to be charged via suitable power electronics 24.

[0063] In the mining machine 2 to be charged, a charger 34 is connected to a DC bus 36 interconnecting the charger 34 and the internal energy source 30, such as a battery, to be charged.

[0064] Fig. 13 shows an embodiment wherein the charger is provided in the charging station, i.e. off-board charging. This embodiment is in many aspects similar to the one described above with reference to Fig. 12, with the difference that a charger 29 is provided in the charging station 20 instead of in the mining machine. 2. By means of the charger 29, the electric power supplied to internal energy source 30 of the mining machine 2 is controlled. A contactor 35 may optionally be provided in the mining machine 2 for disconnecting the charger 29 from the DC bus 36 of the mining machine 2.

[0065] 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.

Claims

CLAIMS1 . A method of controlling an electrical charging station (20) in a mining environment, the electrical charging station (20) being connected to an electrical network (10) and connectable to an electrical storage (30), preferably of a mining machine (2), to provide a charging current (Icharge) to the electrical storage (30), the method comprising the following steps:- determining a remote voltage (Vremote) in the electrical network at a reference position remote from the charging station,- determining a local voltage (Vlocal) at the charging station (20),- determining a voltage difference (Vdiff) between the remote voltage (Vremote) and the local voltage (Vlocal), and- controlling the charging current (Icharge) based on the voltage difference (Vdiff).

2. The method according to claim 1 , wherein the remote voltage (Vremote) is determined by measuring the voltage at the reference position.

3. The method according to claim 1 , wherein the remote voltage (Vremote) is determined by calculating a virtual voltage at the reference position.

4. The method according to any one of claims 1-3, wherein the step of determining a local voltage comprises determining a local voltage (Vlocal) at at least two different charging stations (20a, 20b) connected to different areas of the electrical network 10.

5. The method according to any one of claims 1-4, wherein the local voltage (Vlocal) of a second charging station (20b) is used as remote voltage (Vremote) for a first charging station (20a).

6. The method according to any one of claims 1-5, wherein, based on the voltage difference of two different reference positions in a first and a second electrical network (10a, 10b), respectively, the charging station (20) is disconnected from the first network (10a) and connected to the second network (10b).

7. The method according to any one of claims 1-6, comprising the step of providing an auxiliary energy storage (22) connected to or comprised in the charging station (20).

8. The method according to claim 7, wherein controlling the charging current (Icharge) is additionally based on the charge level of the auxiliary energy storage (22).

9. The method according to claim 7 or 8, comprising the step of controlling energy storage current to / from the auxiliary energy storage (22) based on the voltage difference (Vdiff) and the required charging current (Icharge).

10. The method according to claim 8, comprising the step of deactivating controlling the charging current (Icharge) based on the voltage difference (Vdiff) if the charge level of the energy storage (22) is below a predetermined threshold value.11 . The method according to any one of claims 1 -10, wherein a plurality of charging stations (20a, 20b) is provided, the method comprising the step of assigning a priority to each charging station of the plurality of charging stations (20a, 20b) based on the voltage difference (Vdiff), and to limit the charging current (Icharge) for charging stations with lower priority.

12. The method according to 11 , wherein the priority of a first station (20a) is changed to a second station (20b) based on the voltage difference for each charging station.

13. The method according to any one of claims 1-12, wherein the charging station (20) is provided with a plurality of charging terminals, each chargingterminal being connectable to an electrical storage (30) of a mining machine (2) to provide a charging current (Ichargel , Icharge2) for the electrical storage (30), wherein each of the charging currents is controlled based on the voltage difference (Vdiff).

14. The method according to any one of claims 1-13, comprising the step of changing the reference position from a first reference position with a first remote voltage (Vremotel ) to a second reference position different from the first reference position with a second remote voltage (Vremote2).

15. The method according to any one of claims 1-14, wherein the charging current (Icharge) is controlled inversely linear to the voltage difference (Vdiff).

16. The method according to any one of claims 1-14, wherein the charging current (Icharge) is controlled inversely stepwise to the voltage difference (Vdiff).

17. The method according to any one of claims 1-16, comprising the step of determining an acceptable bandwidth of the local voltage (Vlocal) based on the voltage difference, and, if the local voltage (Vlocal) is outside the acceptable bandwidth, controlling the charging current so that the local voltage (Vlocal) is inside the acceptable bandwidth.

18. The method according to claim 17, wherein the acceptable bandwidth of the local voltage (Vlocal) is adjusted based on the voltage difference (Vdiff).

19. The method according to any one of claims 1 -18, wherein the electrical network is a DC network.

20. The method according to any one of claims 1-19, wherein the reference position is any of the following: the other end of the feeder, a substation, and / or a position in an electrical network different from the electrical network (10) to which the charging station (20) is connected.21 . An electrical charging station (20) for use in a mining environment, the electrical charging station (20) being connectable to an electrical network (10) and connectable to an electrical storage (30) of a mining machine (2) to provide acharging current (Icharge) to the electrical storage (30), wherein the electrical charging station comprises control means for controlling the electrical charging station (20) according to any of claims 1-20.

22. A non-transitory computer-readable storage medium that stores a program configured to execute the method of any one of claims 1 to 20 in an electrical charging station (20) according to claim 21.

23. 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 20 in an electrical charging station (20) according to claim 21 .

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