A system and a Computer-Implemented Method for Charging Electric Vehicles

Abstract

During a measurement period (Tm), an input electric power (PIN) received via a power input interface is registered as a function of time (t), which input electric power (PIN) is forwarded in respective portions to electric vehicles that are connected to respective charging stations via an electric distribution system. The respective portions, in turn, are based on a respective load demand from each of the electric vehicles and said respective portions are controlled via control signals from a controller. Based on the measurement of the input electric power (PIN), the controller determines a control level (Pctrl) for the input electric power (PIN) below which control level (Pctrl) the controller is estimated to be able to control the respective portions of the input electric power (PIN) to the respective electric vehicles during a future time period subsequent to the measurement period (Tm). Further, based on the control level (Pctrl), a limit level for the input electric power (PIN) is derived, which limit level the input electric power (PIN) will not exceed during the future time period. Thereby, a ceiling level for the input electric power (PIN) may be guaranteed.

Description

The present invention relates generally to the allocation of energy resources to electric vehicles. Especially, the invention relates to a system according to the preamble of claim 1 and a corresponding computer-implemented method. The invention also relates to a computer program and a non-volatile data carrier storing such a computer program.BACKGROUNDThe use of electrically powered vehicles has increased tremendously during the last decades. This places a pressure on the infrastructure that electric energy may be distributed to these vehides in such a manner that the overall resources are employed efficiently. Many times, the capacity of the electric infrastructure, for instance in terms of fuse levels and the cross-sectional area of the electrical cables, need to be adapted to the peak loads of the system. Since, typically, the peak loads occur during relatively short time periods, the electric infrastructure is severely oversized during the lion’s share of the time. This, in turn, leads to unnecessary costs for hardware, subscriptions and rates. The prior art contains various solutions aiming at mitigating these problems.US11171509 shows adaptive charging networks that enable the optimization of electric design of charging networks for electric vehicles. One embodiment includes an electrical supply; a plurality of adaptive charging stations; wherein at least one adaptive charging station distributes power to at least one other adaptive charging station; wherein at least one adaptive charging station is configured to communicate capacity information to a controller; and wherein the controller is configured to control the distribution of power to the plurality of adaptive charging stations based upon the capacity information received from at least one adaptive charging station.US20180358839 discloses an electrical power distribution network that is able to provide power to a plurality of loads, such as electric vehicle charging stations, on demand. The network includes a DC bus and a plurality of power sources that may be a number of renewable energy power sources, such as an array of photovoltaic (PV) cells and wind turbines, and a number of energy storage devices, such as batteries, that are electrically coupled to the DC bus. The network also includes a DC-to-AC power conversion system (PCS) that is electrically coupled to the DC bus and an AC utility feed line that is part of an electrical grid. The network further includes a system controller that controls which of the power sources and the utility grid provides power to the loads in response to a power demand from the loads and the available power from the power sources and the grid.US20140062401 describes electric vehicle (EV) charging apparatus and methods, which allow the sharing of charge current between multiple vehicles connected to a single source of charging energy. In addition, this charge sharing can be performed in a grid-friendly manner by lowering current supplied to EVs when necessary in order to satisfy the needs of the grid, or building operator. The apparatus and methods can be integrated into charging stations or can be implemented with a middle-man approach in which a multiple EV charging box, which includes an EV emulator and multiple pilot signal generation circuits, is coupled to a single EV charge station.US20250050776 reveals a power regulator device, a power distribution device and related methods and systems for managing power consumption in electric vehicle supply equipment (EVSE) stations. The power regulator device includes an interconnector attached to an EVSE cable, a storage module for receiving a modulation configuration, and a filtering module for intercepting and altering the signal transmitted from the EVSE station to the electric vehicle. The power distribution device is configured to receive a load configuration and a list of EVSE controllers, measure the total load, and communicate modulation configurations to the EVSE controllers to manage power consumption. The system, designed to operate on a mesh network, includes multiple EVSE stations, power distribution devices, and a centralized monitoring agent for managing and controlling power consumption across the EVSE stations.Thus, various solutions are known that utilize the electrical infrastructure in a comparatively efficient manner when charging electric vehicles. However, there is still room for improving the overall efficiency of the electric infrastructure of such systems.SUMMARYThe object of the present invention is to offer a further improved solution for charging for charging electric vehicles efficiently, for example in terms of hardware, subscription costs and rates.According to one aspect of the invention, the object is achieved by a system for charging electric vehicles which system includes: a power input interface, a number of charging stations, an electric distribution system and a controller. The power input interface receives input electric power from a power source, such as an electrical grid. However, additionally or alternatively, the power source may also be constituted by a fossil-fuel based power station and / or a renewable-energy based power station. Each of the charging stations is configured to forward a respective portion of the input electric power to any respective electric vehicle that is connected to an outlet of said each charging station. Of course, one charging station may have multiple outlets. The electric power forwarded to each outlet is nevertheless individually controllable. The electric distribution system is connected to the power input interface. The electric distribution system is arranged to distribute the respective portion of the input electric power to each of the charging stations. The controller is configured to generate control signals to the charging stations, which control signals determine the respective portion of the input electric power that is forwarded to each of said any respective electric vehicle at any point in time while being connected to the outlet in question. Moreover, the controller is configured to measure, during a measurement period, say one month, the input electric power that is received via the power input interface as a function of time. During the measurement period, the respective portions are forwarded to the electric vehicles based on a respective load demand from each of the electric vehicles. Thus, substantial load peaks may occur. The controller is further configured to determine, based on said measurement of the input electric power during the measurement period, a control level for the input electric power below which control level the controller is estimated to be able to control the respective portions of the input electric power to the respective electric vehicles during a future time period subsequent to the measurement period, for example by partially redistributing their respective loads in time. For example, the control level may be determined to be equal to an average value of the input electric power during the measurement period. The controller is also configured to derive, based on said control level, a limit level for the input electric power, which limit level the input electrie power will not exceed during the future time period. Preferably, inter alia to allow for a degree of unforeseen demand fluctuations, the limit level has same margin to the control level.The above system is advantageous because it has proven to enable a substantial reduction of a maximum input electric power that the system needs to be designed for. As a result, the maximum current of a main fuse to the system may be lowered, perhaps to half of its original level. This, of course, may lead to considerable cost savings for the electricity subscription to the system.According to one embodiment of this aspect of the invention, the controller is configured to derive the limit level based on the control level and taking into account a respective control parameter for each of said electric vehicles, which respective control parameter aims at causing respective batteries in the electric vehicles to reach a respective predefined state-of-charge at a respective particular point in time for each of the electric vehicles. Thus, the limit level is derived with a margin to the control level, so that for example there is extra room for the controller to meet customers’ requests that their battery is charged to a particular level, say 90 %, before they plan to leave the charging station.Alternatively, the controller is simply configured to derive the limit level by multiplying the control level by a factor equal to or larger than one, say around 1.2.According to another embodiment of this aspect of the invention, during a future time period, the controller is configured to control the respective portions of the input electric power to the respective electric vehicles by generating the control signals such that at least one expected load peak is delayed to a respective at least one expected load valley subsequent to the at least one expected load peak. This is key to enable a levelling out of the overall load on the system. Typically, only minor delays are needed for the charging of a relatively small number of electric vehicles in order to lower the highest load peaks significantly.According to yet another embodiment of this aspect of the invention, the controller is configured to calculate a respective average value of the input electric power over each of a series of equal averaging periods during the measurement period. Here, each of the equal averaging periods has an extension in time in a range from 1 second to 120 minutes, preferably in a range from 5 minutes to 60 minutes. This namely facilitates determining the control level.According to still another embodiment of this aspect of the invention, the measurement period has an extension in time that is equivalent to an estimated time required to complete a set number of expected charging cycles in the charging stations of the system. The set number may be in a range from 1 to 120, preferably in a range from 5 to 30 for each of the charging stations. Typically, this means that the measurement period has an extension of approximately one month. Preferably, to collect a sufficient amount of data, the measurement period should have an extension in time in a range from one week to three months.According to another embodiment of this aspect of the invention, the power input interface has a main fuse, and the controller is configured to set a tripping level for the main fuse based on the limit level, for example such that the tripping level equals the limit level.According to another aspect of the invention, the object is achieved by a computer-implemented method executed in a processing unit of a controller in a system that also includes: a power input interface receiving input electric power from a power source; a number of charging stations, which each is configured to forward a respective portion of the input electric power to any respective electric vehicle that is connected to an outlet of said each charging station; and an electric distribution system that is connected to the power input interface, which electric distribution system is arranged to distribute the respective portion of the input electric power to each of said charging stations. The method involves: generating control signals to the charging stations, which control signals determine the respective portion of the input electric power that is forwarded to each of said any respective electric vehicle at any point in time while being connected to said outlet; measuring, during a measurement period, the input electric power that is received via the power input interface as a function of time, wherein, during the measurement period, the respective portions are forwarded to the electric vehicles based on a respective load demand from each of said electric vehicles; determining, based on said measurement of the input electric power, a control level for the input electric power below which control level the controller is estimated to be able to control the respective portions of the input electric power to the respective electric vehicles during a future time period subsequent to the measurement period; and deriving, based on said control level, a limit level for the input electric power, which limit level the input electric power will not exceed during the future time period. The advantages of this method, as well as the preferred embodiments thereof, are apparent from the discussion above with reference to the proposed control unit.Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.BRIEF DESCRIPTION OF THE DRAWINGSThe invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.Figure 1 schematically illustrates a system according to one embodiment of the invention;Figure 2 shows a diagram that illustrates an example of how the input electric power to the system may vary over time during a measurement period according to one embodiment of the invention;Figure 3 shows a diagram that illustrates an example of how the input electric power to the system shown in Figure 2 may be redistributed in time according to one embodiment of the invention to reduce the peak loads on the system; andFigure 4 shows a diagram that exemplifies how the input electric power to the system may vary over time in a future time period, wherein respective portions of the input electric power are forwarded to electric vehicles that are connected to the system according to one embodiment of the invention; andFigure 5 illustrates, by means of a flow diagram, a general method according to the invention for controlling a system for charging electric vehicles.DETAILED DESCRIPTIONIn Figure 1, we see a schematic illustration of a system 100 according to one embodiment of the invention, which system 100 is adapted for charging electric vehicles, here exemplified by 131, 132 and 13n respectively. Figure 2 shows a diagram that illustrates an example of how input electric power PN to the system 100 may vary over time t during a measurement period Tm according to one embodiment of the invention.The system 100 includes a power input interface 105, a number of charging stations 111, 112 and 11n respectively, an electric distribution system 110 and a controller 140.The power input interface 105 receives the input electric powerPIN from a power source, which, for instance may be represented by an electrical grid. Alternatively, or in addition thereto, a fossilfuel based power station and / or a renewable-energy based power station may constitute the power source, of a portion thereof.Each of the charging stations 111, 112 and 11n is configured to forward a respective portion P1, P2 and Pn respectively of the input electric power PIN to the each of electric vehicles 131, 132 and 13n that is connected to an outlet 121, 122 and 12n respectively of the charging stations 111, 112 and 1 1 n. It should be noted that, one or more of the charging stations 111, 112 and 11n may, in turn, include two or more outlets. Further, no portion of the input electric power PIN is forwarded to any charging station where no electric vehicle is connected. According to embodiments of the invention, the system 100 may include any number of charging stations, say from 2 to 2000.The electric distribution system 110 is connected to the power input interface 105. The electric distribution system 110, which for example may be represented by a local electric grid in a building or a parking space, is arranged to distribute the respective portion P1, P2 and Pn respectively of the input electric power PIN to each of the charging stations 111, 112 and 1 1n.The controller 140 is configured to generate control signals c1, c2 and cn to the charging stations 111, 112 and 11n respectively, which control signals c1, c2 and cn determine the respective portion Pi, P2 and Pn of the input electric power PIN that is forwarded to each of the electric vehicles 131, 132 and 13n respectively at any point in time t while the electric vehicle 131, 132 and / or 13n in question is connected to the outlet 121, 122 and 12n respectively.Referring now to Figure 2, during a measurement period Tm, the controller 140 is configured to measure the input electric power PIN that is received via the power input interface 105 as a function of time t.According to one embodiment of the invention, the measurement period Tm has an extension in time t that is equivalent to an estimated time required to complete a set number of expected charging cycles in the charging stations 111, 112 and 11n respectively. Here, the set number is in a range from 1 to 120, preferably in a range from 5 to 30 for each of said charging stations 111, 112 and 1 1 n. Thereby, it is ensured that the measurement period Tm reflects a representative load of the system 100. Typically, this means that the measurement period Tm has an extension in time in a range from one week to three months, preferably around one month. For practical reasons, it may further be advantageous if the measurement period Tm equals an integer number of tariff periods for a service subscription in respect of the power source. Furthermore, is presumed that the charging cycles that are performed during the measurement period Tm are complete, i.e., that the registered measurements relate to charging cycles that were finished intentionally by the respective user, for example in response to disconnecting the charging cable or by entering a stop command via an app or other user interface.It is presumed that, during the measurement period Tm, the respective portions P1, P2 and Pn are forwarded to the electric vehicles 131, 132 and 13n respectively based on a respective load demand from each of the electric vehicles 131, 132 and 13n, i.e. essentially without applying any load equalizing strategies.Referring now also to Figure 3, based on the measurement of the input electric power PIN during the measurement period Tm, the controller 140 is configured to determine a control level Pctrl for the input electric power PIN below which control level Pctrl the controller 140 is estimated to be able to control the respective portions P1, P2 and Pn of the input electric power PI N to the electric vehicles 131, 132 and 1 3n respectively during a future time period Tf, which is subsequent to the measurement period Tm.As can be seen in Figure 3, a first load peak occurs between t1 and t2, a second load peak occurs around t3 and a third load peak occurs between t4 and t5. The first, second and third load peaks may be due to periods during a day, a week or a month when a relatively large number of electric vehicles with respective low state-of-charge batteries connect to the system 100 more or less simultaneously.According to one embodiment of the invention, the controller 140 is configured to determine the control level Pctrl based on an assumption that, during the future time period Tf, the controller 140 will be able to control the respective portions P1, P2 and Pn of the input electric power PIN to the respective electric vehicles 131, 132 and 13n respectively by generating the control signals ci, C2 and cn respectively, such that expected load peaks, exemplified as PL1, PL2, PL3 and PL4 in Figure 3, are delayed D1, D2, D3 and D4 to respective load valleys, exemplified as VL1, VL2, VL3 and VL4 respectively in Figure 3, which load valleys are expected to occur subsequent to the at least one expected load peak PL1, PL2, PL3, and PL4. AS a result, the variations the input electric power PIN can be made substantially smaller. In particular, the input electric power PIN may be kept below the control level Pctrl. For completeness, Figure 3 further illustrates an initial expected load valleyVL0 that precedes the load valley VL1, which initial expected load valley VL0 may accommodate for any load peak that might precede the load peak PL1.According to one embodiment of the invention, at least as an initial postulation, the controller 140 is configured to determine the control level Pctrl to be equal to an average of the input electric power PIN during the during the measurement period Tm.According to another embodiment of the invention, to determine the control level Pctrl, the controller 140 is configured to calculate a respective average value of the input electric power PIN over each of a series of equal averaging periods during the measurement period Tm. Here, each of the equal averaging periods has an extension in time in a range from 1 second to 120 minutes, and preferably in a range from 5 minutes to 60 minutes. This namely facilitates the processing of the data and renders determining the control level Pctrl straightforward.Based on the control level Pctrl, the controller 140 is further configured to derive a limit level Pmax for the input electric power PIN. The limit level Pmax is a level that the input electric power PIN will not exceed during the future time period Tf. Thus, the limit level Pmax may be regarded as a fuse level for the power input interface 105. It is generally assumed that an operating voltage of the system 100 is fixed. Consequently, there is a unambiguous relationship between the limit level Pmax, which may be represented as electric power, e.g. expressed in joules per second or watts, and the fuse level, which may be represented as a current, e.g. expressed amperes.According to one embodiment of the invention, the controller 140 is configured to derive the limit level Pmax based on the control level Pctrl, for example as proposed above, and further take into account a respective control parameter for each of the electric vehicles 131, 132 and 13n, which respective control parameter aims at making a respective battery in these vehicles reach a predefined state-of-charge for each of the electric vehicles 131, 132 and 13n at a respective particular point in time for the respective electric vehicles 131, 132 and 13n. Consequently, the control parameters delimit, to some extent, the maximum possible delays D1, D2, D3 and D4 for the load peaks PL1, ΡL2, PL3 and PL4 respectively. Although the control level Petri may thus be somewhat elevated this may be beneficial because it increases the chances that the electric vehicles 131, 132 and 13n are adequately charged when their owners plan to leave the respective charging stations 111, 112 and 11n.According to another embodiment of the invention, the controller 140 is configured to derive the limit level Pmax by simply multiplying the control level Pctrl by a factor that is equal to or larger than one, say in a range from 1.1 to 1.6.Figure 4 shows a diagram that exemplifies how the input electric power PIN to the system 100 may vary over time t in a future time period Tf, wherein the respective portions P1, P2 and Pn of the input electric power PIN are forwarded to electric vehicles 131, 132 and 13n that are connected to the system 100 via the charging stations 111, 112 and 11n and the outlets 121, 122 and 12n respectively.As can be seen, with only a few temporary exceptions, the input electric power PIN remains below the control level Pctrl throughout the future time period Tf. In any case, the input electric power PIN never exceeds the limit level Pmax.Referring now again to Figure 1, according to one embodiment of the invention, the power input interface 105 includes a main fuse 105f, and the controller 140 is further configured to set a tripping level FL for the main fuse 105f based on the limit level Pmax. For example, the tripping level FL for the main fuse 105f may be set equal to the limit level Pmax, or to a factor larger than one thereof.Hence, it is expected that a subscription rate for the system may be lowered, and as a result, costs can be saved in relation to a previously used tripping level FL for the main fuse 105f.It is generally advantageous if the controller 140 is configured to effect the above procedure in an automatic manner by executing a computer program. Therefore, the controller 140 may include at least one processing unit 143 and a memory unit 145, i.e. a nonvolatile data carrier, storing a computer program 147, which, in turn, contains software for making the at least one processing unit 163 execute the actions mentioned in this disclosure when the computer program 147 is run on the at least processing unit 143.In order to sum up, and with reference to the flow diagram in Figure 5, we will now describe a computer-implemented method according to the invention, which method is performed in the at least processing unit 143 of the controller 140.In a first step 510, the input electric power that is received via a power input interface to the system is measured as a function of time during a measurement period.Then, in a step 520, based on the measurement in step 510, a control level is determined. The control level is a level below which the controller 140 is estimated to be able to control the input electric power during a future time period that is subsequent to the measurement period of step 510.In a step 530 thereafter, based on the control level, a limit level is derived for the input electric power, which limit level the input electric power will not exceed during the future time period.In a final step 540, a number of charging stations of the system are controlled by the controller 140, such that the limit level for the input electric power is not exceeded.The process steps described above with reference to Figure 5 may be controlled by means of a programmed processor. Moreover, although the embodiments of the invention described above with reference to the drawings comprise processor and processes performed in at least one processor, the invention thus also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other form suitable for use in the implementation of the process according to the invention. The program may either be a part of an operating system, or be a separate application. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a Flash memory, a ROM (Read Only Memory), for example a DVD (Digital Video / Versatile Disk), a CD (Compact Disc) or a semiconductor ROM, an EPROM (Erasable Programmable Read-Only Memory), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or a magnetic recording medium, for example a floppy disc or hard disc. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or by other means. When the program is embodied in a signal, which may be conveyed, directly by a cable or other device or means, the carrier may be constituted by such cable or device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant processes.Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.The term “comprises / comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components. The term does not preclude the presence or addition of one or more additional elements, features, integers, steps or components or groups thereof. The indefinite article "a" or "an" does not exclude a plurality. In the claims, the word “or” is not to be interpreted as an exclusive or (sometimes referred to as “XOR”). On the contrary, expressions such as “A or B” covers all the cases “A and not B”, “B and not A” and “A and B”, unless otherwise indicated. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.It is also to be noted that any reference in this specification to a second, third, fourth etc. of an instance or a feature does not require the presence of a first or lower ordered specimen of the instance or feature in question. The ordinal numbers merely represent a convenient means of reference to distinguish the specific instances or features from one another.It should further be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims. Any subject-matter falling outside the scope of the claims is provided for information purposes, only.

Claims

1. A system (100) for charging electric vehicles (131, 132, 13n), said system (100) comprising:a power input interface (105) which receives incoming electrical power (PIN) from a power source,a number of charging stations (111, 112, 1 1n), each of which is configured to forward a respective portion (P1, P2, Pn) of the incoming electrical power (PIN) to a respective electric vehicle (131, 132, 13n) which is connected to a socket (121, 122, 12n) of each of said charging stations (111, 112, 11n),an electrical distribution system (110) which is connected to the power supply interface (105), which electrical distribution system (110) is arranged to distribute the respective part (P1, P2, Pn) of the incoming electrical power (PIN) to each of said charging stations (111, 112), 1 1n), anda control unit (140) configured to generate control signals (c1, c2, cn) to the charging stations (111, 112, 1 1 n), which control signals (c1, c2, cn) determine the respective portion (P1, P2, Pn) of the incoming electrical power (PIN) which is forwarded to each of said respective electric vehicles (131, 132, 13n) at any future time (t) while connected to said outlet (121, 122, 12n), characterized in that the control unit (140) is further configured to:during a measurement period (Tm) measuring the incoming electrical power (PIN) which is received via the power input interface (105) as a function of time (t), whereby, during the measurement period (Tm), respective parts (P1, P2, Pn) are forwarded to the electric vehicles (131, 132, 13n) based on a respective load demand from each of said electric vehicles (131, 132, 13n),determining, based on said measurement of the incoming electrical power (PIN), a control level (Pctrl) for the incoming electrical power (PIN) under which control level (Pctrl) the control unit (140) is estimated to be able to control respective parts (P1, P2, Pn) of the incoming electrical power (PIN) to the respective electric vehicle (131, 132, 13n) during a future period of time (Tf) after the measurement period (Tm), andbased on said control level (Pctri) derive a limit level (Pmax) for the incoming electrical power (PIN), which limit level (Pmax) the incoming electrical power (PIN) will not exceed during the future time period (Tf).

2. The system (100) according to claim 1, wherein the control unit (140) is configured to derive the limit level (Pmax) based on the control level (Pctrl) and taking into account a respective control parameter for each of said electric vehicles (131, 132, 13n), which respective control parameter aims to cause respective batteries therein to reach a respective predefined state of charge at a respective specific time for each of said electric vehicles (131, 132, 13n).

3. The system (100) of claim 1, wherein the control unit (140) is configured to derive the limit level (Pmax) by multiplying the control level(Pctri) by a factor equal to or greater than one.

4. The system (100) according to any one of the preceding claims, wherein, during a future period of time (Tf), the control unit (140) is configured to control respective portions (P1, P2, Pn) of the incoming electrical power (PIN) to respective electric vehicles (131, 132, 13n) by generating the control signals (c1, c2, cn) such that at least one expected load peak (PL1, ΡL2, ΡL3, PL4) is delayed (D0, D1, D2, D3, D4) to a respective at least one expected load valley (VL0, VL1, VL2, VL3, VL4) after the at least one expected load peak (PL1, PL2, PL3, PL4).

5. The system (100) according to any one of the preceding claims, wherein the controller (140) is configured to:calculate a respective average value of the incoming electrical power (PIN) over each of a series of equal average periods during the measurement period (Tm), each of said equal average periods having a time extension in a range from 1 second to 120 minutes, preferably in a range from 5 minutes to 60 minutes.

6. The system (100) according to any one of the preceding claims, wherein the measurement period (Tm) has a time extension corresponding to an estimated time required to complete a set number of expected charging cycles in said charging stations (111, 112, 11n), which set number is in a range from 1 to 120, preferably in a range from 5 to 30 for each of said charging stations (111, 112, 11n).

7. The system (100) according to claim 6, wherein the measurement period (Tm) has a time span in an interval from one week to three months, preferably around one month.

8. The system (100) according to any one of the preceding claims, wherein the power source is at least one of an electrical grid, a fossil fuel-based power plant and a renewable energy-based power plant.

9. The system (100) according to any one of the preceding claims, wherein the power input interface (105) comprises a main fuse (105f), and the controller (140) is configured to set a trip level (FL) for the main fuse (105f) based on the threshold level (Pmax).

10. The system (100) according to any one of the preceding claims, wherein the control level (Pctrl) is equal to an average value of the incoming electrical power (PIN) during the measurement period (Tm).

11. A computer-implemented method executed in a processor unit (143) in a controller (140) in a system (100) for charging electric vehicles (131, 132, 13n), the system (100) comprising: a power input interface (105) that receives incoming electrical power (PIN) from a power source; a plurality of charging stations (111, 112, 11n), each configured to forward a respective portion (P1, P2, Pn) of the input electrical power (PIN) to a respective electric vehicle (131, 132, 13n) that is connected to an outlet (121, 122, 12n) of each charging station (111, 112, 11n); an electrical distribution system (110) connected to the power input interface (105), said electrical distribution system (110) being arranged to distribute respective portions (Pi, P2, Pn) of the incoming electrical power (PIN) to each of said charging stations (111, 112, 11n), and the method comprises:generating control signals (c1, c2, cn) to the charging stations (111, 112, 11n), which control signals (c1, c2, cn) determine the respective portion (P1, P2, Pn) of the incoming electrical power (PIN) that is forwarded to each of said respective electric vehicles (131, 132, 13n) at any time (t) while connected to said outlet (121, 122, 12n),characterized in that the method further comprises:measuring, during a measurement period (Tm), the incoming electrical power (PIN) received via the power input interface (105) as a function of time (t), whereby, during the measurement period (Tm), respective parts (P1, P2, Pn) are forwarded to the electric vehicles (131, 132, 13n) based on a respective load demand from each of said electric vehicles (131, 132, 13n),determining, based on said measurement of the incoming electrical power (PIN), a control level (Pctrl) for the incoming electrical power (PIN) under which control level (Pctrl) the control unit (140) is estimated to be able to control respective parts (P1, P2, Pn) of the incoming electrical power (PIN) to the respective electric vehicle (131, 132, 13n) during a future period of time (Tf) after the measurement period (Tm), andderiving, based on said control level (Pctrl), a limit level (Pmax) for the incoming electrical power (PIN), which limit level (Pmax) the incoming electrical power (PIN) will not exceed during the future time period (Tt).

12. A computer program (147) which is loadable to a non-volatile data carrier (145) which is communicatively connected to a processing unit (143), wherein the computer program (147) comprises software for performing the method according to claim 11 when the computer program (147) is run on the processing unit (143).

13. A non-volatile data carrier (145) containing the computer program (147) according to claim 12.