BE1020037A3 - MAINS CONNECTION FOR GROUPED CHARGING OF ELECTRIC VEHICLES. - Google Patents

Abstract

A system (1) and a method for controlling an electrical power (PT) from an electricity grid (2) to a plurality of charging stations (5) and / or vice versa, wherein the electricity grid (2) has a varying power consumption, and wherein each charging station (5) has a plurality of charging points (7) for connecting electric vehicles (8), each charging station (5) being coupled to the electricity network (2) by means of a power limiter (4) with an adjustable power limit ( Pmax1) for limiting the power supplied from the electricity grid (2) to the charging station (5) depending on the varying power consumption of the electricity grid (2).

Description

MAINS CONNECTION FOR GROUPED CHARGING OF ELECTRIC

VEHICLES

DOMAIN OF THE INVENTION

The invention relates to a system and method for managing an electrical power from an electricity grid to a plurality of charging stations and / or vice versa, wherein the network has a varying power consumption, and wherein each charging station has a plurality of charging points for connecting of electric vehicles.

STATE OF THE ART

Systems for generating and distributing electrical energy are known. To guarantee the stability of the electricity networks, it is important that the total power generated and the total power used are in balance at all times. Until a few decades ago, energy generation (the so-called "energy injection" into the network) was mainly supplied by operators of large power plants (eg gas plants, coal plants, nuclear plants) with a capacity of eg 250 MWatt per plant or more. A large number of consumers are connected to the electricity grid, both large consumers such as industrial users (factories), as well as smaller consumers such as offices and household consumers. Control systems must ensure that the amount of energy generated is always equal to the amount of energy used by ensuring that the total energy generated by the power stations at all times corresponds to the total energy used by the end users. In practice it means that power plants must produce more energy at times of high consumption (eg during the so-called "peak hours"), and produce less at times of low consumption (eg at night). The total energy production capacity must be sufficiently large to be able to supply the peak power, otherwise the mains voltage becomes unstable, possibly resulting in a power failure. To prevent power outages as much as possible, energy producers therefore provide a production capacity that is considerably higher than the average power consumption in order to be able to absorb the peak power. In practice, this proves to be an expensive affair, since peak power is only required for, for example, a hundred hours per year, while the capital investment for the necessary infrastructure for this is considerable.

Another problem is that energy consumption can change very quickly over time, and to maintain grid stability, the total power generated must be able to follow these rapid fluctuations. Since the production capacity of large power plants cannot be changed quickly, smaller installations are also needed that are only started when demand is high and that often achieve a lower return than the larger power plants, but which are necessary to cope with the rapid changes in meet the demand for electricity. Conversely, the production capacity of large power plants (eg if they are running "at full speed") cannot be reduced rapidly, which results in an energy surplus on the grid when the demand for electricity suddenly decreases.

In the past, attempts have been made to limit peak consumption, among other things. introduction of a multiple tariff (eg cheap night tariff) whereby users shift part of the consumption (eg for washing machines) to night instead of during the day, and they managed to preserve the balance between supply and demand (usually) by driving up production on the basis of good predictions, by importing electricity from abroad, by using hydro-electric power stations (eg the hydro-electric power station of Coo / Trois-Points in Belgium) that can supply power at one time supply by allowing water to flow from a higher area through pipes and by driving turbines, and can use energy at another time (eg at night) to pump that same water up again, etc.

With the advent of distributed energy production with a very irregular production capacity such as, for example, wind turbines, CHPs (combined heat and power plants), solar panels on the one hand, and the explosive growth in the demand for electricity from electric vehicles to be charged on the other, it is The problem of maintaining the stability of the mains voltage has not become easier. On the contrary, the energy producers must not only take into account a constantly increasing demand (peak consumption), but must also keep the grid in balance despite the highly variable power consumption and variable power injection.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a system comprising: an electricity network with varying power consumption and with a network management system for managing the power consumption on the electricity network: - a plurality of charging stations connected to the electricity network, each charging station having a plurality of charging points for connecting electric vehicles; which can increase the stability of the electricity grid.

This object is achieved by a system which has the technical characteristics of the first independent claim. To this end, each charging station is coupled to the electricity grid by means of a power limiter with a first adjustable power limit, wherein the power limiter is provided for limiting the power supplied by the electricity grid to the charging station, and wherein the power limiter comprises communication means for communicating with the network management system ; and the network management system is provided with control means for setting the first adjustable power limit in the power limiters depending on varying power consumption of the electricity network.

In this patent, "the network" and "the electricity network" are used as synonyms, unless explicitly stated otherwise.

In this patent specification, the terms "demand" and "electricity consumption" and "power consumption" mean the same unless explicitly stated otherwise.

In this patent specification, the terms "supply" and "electricity production" and "power injection" mean the same unless explicitly stated otherwise.

Because the charging station is coupled to the electricity grid by means of a power limiter, the power consumed by the charging station for charging the electric vehicles can be limited to a certain value that the electricity grid can deliver without compromising the stability of the grid. bring. Without the power limiter, the charging station could itself choose how much power it draws from the grid, even at times when the grid is already heavily loaded, or even critically loaded.

Because the power limiter has an adjustable power limit that is adjustable by the grid management system, the power limit can be adjusted dynamically according to the needs and possibilities of the electricity grid, which change at any time of the day. For example, the network management system can decide to reduce the total power that is offered to the charging station at times when the network is already heavily loaded and has insufficient capacity or threatens to get it. In an extreme case (eg with congestion problems) the charging station can even be completely disconnected from the mains temporarily. Because charging electric vehicles is not a time-critical application, charging can be temporarily postponed at times when the grid cannot or hardly meet demand. On the other hand, it may be appropriate at other times to increase the power limit in order to be able to use available energy from sustainable generation.

By controlling the power limiter from the grid management system and not from the charging station, it is possible to respond more quickly to the varying power consumption, which further increases the grid stability.

By providing each charging station that comprises a plurality of charging points with a power limiter, a (relatively) large power consumption can be reduced in a (relatively) simple way, whereby the stability of the network can be considerably improved.

Limiting the power by means of a power limiter with an adjustable power limit instead of a switch with a fixed predetermined maximum value, a reliable system is obtained that can act dynamically depending on changing circumstances, but in a way that is much less drastic than merely completely switching off consumers. In this way the needs and wishes of both the network 2 and the charging stations 5 can be optimally combined.

Preferably, each charging station is provided with a charging station management system for managing power flows from and / or to the individual charging points, and the network management system is communicatively coupled to the charging station management system to communicate changes in the first controllable power limit before the first controllable power limit configure.

Because the network management system communicates with the charging station management system and not with the individual charging points, the complexity of the network management system can remain limited, and the charging station can largely retain its flexibility towards the individual vehicles.

By making changes to the permitted maximum power known to the charging station before effectively setting the (new) power limit, the charging station can optimally adapt to the new situation.

The network management system is preferably further provided for transmitting price information as a function of the power limit to the charging station management system.

This allows the station manager to adjust the price for charging the electric vehicles to the price that he himself has to pay to the network manager. The owners of the electric vehicles can, for example, decide on the basis of this price (or eg pre-agreed maximum charging rates) to postpone charging. By dynamically increasing the price of the electricity at times of heavy network load, the network manager can reduce the demand for electricity, which means that less power will be used, which benefits the stability of the network.

The charging station is preferably further provided with a meter for measuring the instantaneous power of the charging station, and for transmitting the measured power to the network management system.

In this way, the grid management system receives information about the instantaneous power of each charging station, which can be (considerably) lower than the set power limit. As a result, the network management system has a better insight into the large users, and it can also respond better to the actual needs.

Preferably, the system is further provided for supplying power from the electric vehicles through the charging station to the electricity grid, and the power limiter is provided with a second controllable power limit to limit the power to the electricity grid.

Allowing charging stations to transfer energy from the electric vehicles and preferably also from renewable sources (such as wind turbines, solar panels, etc.), or other energy storage sites (such as electric batteries, compressed air energy systems, etc.) to the grid , the charging stations can also act as energy suppliers. In order to avoid and limit an excess supply of energy in the network, the power limiters in this case are preferably provided to limit the flow in the direction from the charging stations to the network according to a second adjustable power limit, adjustable by the network management system, which the stability of the network again benefits, this time by limiting over-supply of power.

In one embodiment, the power limiter comprises a Remote Terminal Unit (abbreviated as RTU), also called Remote Telemetry Unit.

The RTU is a control and communication module that can receive information via a communication port (eg an Ethernet connection or a serial port or other) from a management system and converts it into a control signal via an output port (eg a potential-free contact). An RTU can receive measurement signals via an input port and send these measurement signals to a management system via a communication protocol.

In one embodiment, the charging station comprises at least one automatic device for connecting a group of charging points to the electricity grid, the Remote Terminal Unit being provided for operating the automatic devices.

Preferably, the network management system will switch the whole of the charging stations on or off, not the individual charging stations themselves. The latter is a responsibility of the charging station management system.

Preferably, the meter comprises a modem for transmitting the measured instantaneous power to the network management system and for receiving control messages, and the meter and the power limiter are communicatively connected for communicating the first and / or the second controllable power limit.

When the charging station contains a meter with communication means, such as a modem, measurement data can be sent to the network management system, which thus receives accurate information about the instantaneous consumed or generated capacity of the charging station, giving it more insight into the consumers (or suppliers), allowing it to better adjust the power limits to better guarantee the stability of the network, while optimally taking into account the power of the charging stations.

The invention further relates to a method for managing an electrical power from an electricity network to a plurality of charging stations and / or vice versa, which can be performed on such a system.

BRIEF DESCRIPTION OF THE FIGURES

The invention is further elucidated on the basis of the description below and the accompanying figures. Note that the figures are not necessarily drawn to scale, and that the proportions of the parts do not necessarily correspond to reality. The figures serve to describe the principles of the invention. The same elements are numbered equally across the various drawings.

Fig. 1 shows a system with an electricity network and a charging station known in the prior art.

Fig. 2 shows an embodiment of a system according to the present invention, with an electricity network and a charging station and a variable power limiter with a first controllable power limit for limiting the power supplied by the network to the charging station.

Fig. 3 shows a variant of the system of Fig. 2, wherein the charging station has a management system that is communicatively connected to the network management system.

Fig. 4 shows an embodiment of a system according to the invention, wherein the power limiter has a second controllable power limit for limiting the power supplied by the charging station to the network.

Fig. 5 shows an embodiment of the charging station of Fig. 3 in more detail.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The present invention will be described with reference to certain embodiments and with reference to certain drawings, but the invention is not limited thereto and is only determined by the claims. The described drawings are only schematic and non-limiting. In the drawings, the size of certain elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual practical embodiments of the invention.

In addition, the terms first, second, third and the like in the description and in the claims are used to distinguish between similar elements and not necessarily to describe a sequential or chronological order. The terms are interchangeable under appropriate conditions and the embodiments of the invention may be used in sequences other than described or illustrated herein.

The term "comprising", used in the claims, is not to be interpreted as being limited to the means mentioned below and does not exclude other elements or steps. The term is to be interpreted as specifying the presence of the aforementioned features, elements, steps or components referred to, but does not exclude the presence or the addition of one or more other features, elements, steps or components, or groups thereof . The scope of the expression "a device comprising means A and B" should not be limited to devices that only consist of components A and B. It means that with regard to the present invention, the only relevant components of the device are A and B.

REFERENCES: 1 system 2 electricity network 3 network management system 4 power limiter 5 charging station 6 charging station management system 7 charging points 8 electric vehicle 9 meters 10 modem 11 automatic 12 motor 13 control means 14 group of charging points

15 RTU

16 communicative connection 17 relays PT total power of the charging station

Pmaxl first adjustable power limit

Pmax2 second adjustable power limit P1 power of the first charge point

Fig. 1 shows a system 1 with an electricity network 2 (e.g. a low-voltage network of 220V) with a network management system 3, and a charging station 5 with a plurality of charging points 7 (e.g. "charging stations"), e.g. at least two, preferably at least five, more preferably at least ten, for charging electric vehicles 8 (not shown). Usually, each charging point 7 can charge one vehicle 8. A charging point 7 can be physically designed, for example, in the form of an outlet on a charging station, wherein the charging station can contain one or more electrical outlets. The vehicle's battery acts as an energy consumer. In practice, a large number of other consumers (electrical appliances, lighting, motors, etc., of factories, offices, houses) also depend on the network 2, but these are not shown to simplify the figures.

In the example of Fig. 1, the charging station 5 has its own management system 6 which is managed by the operator of the charging station 5, and which controls the power supply to each charging station 7. In one embodiment, the charging station 5 may comprise a payment terminal, and an electrical circuit for switching on or off the power supply P1, P2, Pn of the electricity network 2 to each charging point 7, and each charging point 7 usually comprises its own power meter coupled to the charging station management system 6. However, the details of the internal operation of a charging station 5 fall outside the scope of the present invention. The sum of the capacities P1 to Pn of the individual charging points 7 together is the total power PT that must be supplied by the electricity grid 2. This total power PT usually varies with time, so PT (t). In existing systems, this total power PT has a non-variable limit from the electricity network 2, so the electricity network 2 must supply the requested power, and this power can increase as more vehicles need to be charged. However, this situation can be fatal for the stability of the network 2 in situations when the total power consumption on the network 2 (including the other consumers) becomes too high, ie higher than the power production of eg the power plants (not shown) that inject power on the electricity grid 2. Even a situation where the power consumption is 1.5% lower than the power production is a very critical situation.

Fig. 2 shows an example of a system 1 according to the present invention. This system comprises a plurality of charging stations 5, but only one such charging station 5 is shown. The operation of the system 1 from and to the other charging stations 5 is similar. By dynamically determining the permissible maximum power of the various charging stations 5, the network management system 3 ensures that the capacity of the electricity network 2 is not exceeded and that the stability is not compromised. The main differences with the system of Fig. 1 is that in the system 1 of Fig. 2 comprises a power limiter 4 with an adjustable power limit Pmax1 for limiting the power PT (t) supplied by the electricity network 2 to the charging station 5 to a first maximum permissible value, determined and set by the grid management system 3. Preferably, the power limiter 4 is placed between the charging station 5 and the electricity grid 2. The power limit Pmax1 (t) can be controlled from the grid management system 3, depending on the varying power consumption on the network 2, by using communication means to communicate the allowed power limit Pmax1 to the power limiter 4, and by control means to effectively set this power limit Pmax1. As communication means 16, "Power-Line" communication is preferably used (a communication system in which communication signals are superimposed on the power lines), but other communication means such as, for example, ADSL, LAN (local area network), GSM, GPRS, SMS, POTS (normal telephone line) can also be used. In this way the network management system 3 can limit the power consumption PT (t) of the charging station 5 as a function of time, in accordance with the available capacity of the electricity network 2, taking into account the varying power consumption on the network 2, whereby the stability of the network 2 increases. The adjustable power limit Pmax1 can of course be different per charging station 5.

The network management system 3 is preferably provided with a charging station management system 6 for managing power flows from and / or to the individual charging points 7, and the network management system 3 is communicatively coupled to the charging station management system 6 to make changes in the first controllable power limit Pmax1 communicate before setting the first new power limit Pmaxl. Such a system 1 is represented in Fig. 3. By communicating in advance, the charging station 5 is offered the option of optimally adapting to the new situation, for example by changing its internal configuration. For example, a charging station management system 6 could decide to provide power to certain charging points 7a, 7n, and not to other charging points (eg 7b in Fig. 2). In another example, the charge management system 3 could, for example, apply time multiplexing in such a way that the sum of the powers P1, P2, etc. of the charging points 7a, 7b, etc. is lower than the maximum permitted power limit Pmax1 at any time. In that case, the vehicles 8a, 8b, etc. would be recharged alternately during certain periods. The chosen strategy to make the total consumed power PT smaller than the imposed power limit Pmax1 is preferably left to the charging station 5 itself, and has no influence on the network stability as long as the total consumed power PT is smaller than the power limit Pmax1. In this way the complexity on the side of the network 2 is reduced, while the energy consumption of a large group of consumers 8 can nevertheless be kept under control.

Preferably, the network management system 3 is further provided for transmitting price information as a function of the power limit Pmax1, to the charging station management system 6. The price information can, for example, be dynamically transmitted in the form of a list or table of rates as a function of the power. This is, as it were, a gentle way to reduce the demand for electricity from the charging stations 5 at times of high power consumption (eg peak moments), or to ask for an increased fee if the grid operator uses extra resources (eg diesel generators), which are often more expensive must commit to extra energy production. In this way, the network operator can try to shift peak consumption to less busy periods, although only a price increase is no guarantee for this. The power limiter as described above is.

The charging station 5 of Fig. 2 has a meter 9 for measuring the instantaneous power PT of the total charging station 5, which may, for example, be much lower than the set power limit Pmax1. This meter 9 preferably has communication means whereby the meter reading can be read remotely by the network management system 3.

Fig. 4 shows a variant of the system 1 of Fig. 3, wherein the charging station 5 supplies power to the electricity network 2, in the reverse direction. In this case, the battery of the electric vehicle 8 acts as an energy source. Electric vehicles 8 have a power capacity of the order of 10-23 KWatt. The power limiter 4 is preferably provided in this case to limit the power supplied to the network 2 to a second maximum value Pmax2. By allowing the charging stations 5 to flow energy from the electric vehicles 8 to the network 2, the charging stations 5 can temporarily function as energy suppliers. This may be of interest to the network operator for absorbing sudden increases in power consumption on the network, since the energy from electric vehicles 8 is available very quickly, unlike other energy sources that sometimes require several minutes before being able to supply sufficient power. The principle of using electric vehicles for temporary energy storage during moments of low consumption on the network (eg at night), and to use it as an energy supplier during moments of high consumption on the network (eg during peak moments) can also offer other advantages such as reducing the infrastructure costs of the network operator. However, the feasibility and financial aspects of such applications are beyond the scope of the current patent application. The system 1 of Fig. 4 works very similar to that of Fig. 2, except that the power PT is limited in the other direction, more specifically, the power supplied to the network is limited to a maximum value Pmax2. The second power limit Pmax2 is thereby set by the network management system 3 depending on the needs and requirements of the network 2 to guarantee the stability of the network, and is inter alia dependent on the varying power consumption. Here too, price information is preferably communicated in advance to the charging management system 6, this time the price that the network manager is prepared to pay to the charging station 5 for receiving power, whereby the station manager can in turn decide which vehicles 8 for the proposed price in eligible to provide assets, and which do not. As described above, the details of the interactions within the charging station 5 are of no importance to the grid management system 3, as long as the power sent to the grid does not exceed the second adjustable power limit Pmax2. Note that the value of the second adjustable power limit Pmax2 can differ per charging station 5.

Fig. 5 shows an embodiment of the charging station 5 of Fig. 3 in more detail. The charging points 7 of the charging station 5 of Fig. 5 are grouped into one or more groups 14, each comprising one or more charging points 7. In the example of Fig. 5, one group 14 is shown with three charging points 7, but more or fewer charging points 7 may also be grouped per group 14. The power from the electricity grid 2 to each group 14 (or vice versa) flows through a circuit breaker (also called an automatic circuit breaker, a maximum switch, a circuit breaker or an automatic fuse), which can be switched on or off mechanically by means of a motor 12, in order to 14 of charging points 7 to be connected or not to the electricity grid 2. The motor 12 is controlled by means of a relay 17, which in turn is controlled from a Remote Terminal Unit 15, abbreviated RTU, which is connected via a modem 10 to the network management system 3. As an alternative to an RTU, another device could have been used that can convert communication signals into control signals, and that can convert measured data into communication signals. The power meter 9 could also contain these functionalities. The logic to compare the measured (instantaneous) power with the limit value Pmax1 or Pmax2, and to execute a command as a result of an overrun, can be present both locally in the RTU and in the network management system 3. If the machine becomes 11 switched off, the power Pg1 of the group 14 is zero, and the vehicles 8a, 8b of the group 14 cannot therefore consume power from (or supply to) the electricity grid 2. The more groups 14 with automatic devices 11 the charging station 5 has the finer the total power PT of the charging station 5 can be controlled. Preferably, each group 14 comprises at least two vehicles 8, preferably at least three, more preferably at least ten, but it could also comprise a single vehicle. In that case, the Remote Terminal Unit would operate 15 vending machines 11 for each charging point 7 separately.

But other systems 1 than those of Fig. 4 are also possible, and the power limiter 4 can take other forms there. Eg if the charging station 14 applies time multiplexing, and itself internally ensures that PT <Pmax1 (or Pmax2), where the variable power limit Pmax1, Pmax2 is imposed by the network management system 3, the power limiter 4 can be, for example, a single switch operated from the network management system 3, which can switch off the entire charging station 5 if it does not adhere to the maximum power limit Pmax1 (or Pmax2).

Although the present invention has been described with reference to specific preferred embodiments, it will be appreciated that various modifications may be made to these embodiments without departing from the scope of the invention as set forth in the claims. Accordingly, the description and drawings are to be considered in an illustrative sense rather than a restrictive sense.

Claims (14)

A system (1) comprising: - an electricity network (2) with varying power consumption and with a network management system (3) for managing the power consumption on the electricity network; - a plurality of charging stations (5) coupled to the electricity network (2), wherein each charging station comprises a plurality of charging points (7) for connecting electric vehicles (8); characterized in that - each charging station (5) is coupled to the electricity grid (2) by means of a power limiter (4) with a first adjustable power limit (Pmax1), wherein the power limiter (4) is provided for limiting the power supplied by the electricity network (2) at the charging station (5), and wherein the power limiter (4) comprises communication means for communicating with the network management system (3); - and that the network management system (3) is provided with control means for setting the first adjustable power limit (Pmax1) in the power limiters (4) depending on the varying power consumption of the electricity network (2). The system (1) according to claim 1, wherein each charging station (5) is provided with a charging station management system (6) for managing power flows from and / or to the individual charging points (7), and wherein the network management system (3) ) is communicatively coupled to the charging station management system (6) to communicate changes in the first adjustable power limit (Pmax1) before setting the first adjustable power limit (Pmax1). The system (1) according to claim 2, wherein the network management system (3) is further provided for transmitting price information as a function of the power limit to the charging station management system (6). The system (1) according to any one of the preceding claims, wherein the charging station (5) is further provided with a meter (9) for measuring the instantaneous power of the charging station (5), and for transmitting the measured power to the network management system (3). The system (1) according to any one of the preceding claims, wherein the system is further provided for supplying electric power from the electric vehicles (8) through the charging station (5) to the electricity grid (2), and wherein the power limiter (4) is provided with a second adjustable power limit (Pmax2) to limit the power to the electricity grid (2). The system (1) according to any of the preceding claims, wherein the power limiter (4) comprises a Remote Terminal Unit (15). The system (1) according to claim 6, wherein the charging station (5) comprises at least one automaton (11) for connecting a group (14) of charging points (7) to the electricity network (2), and wherein the Remote Terminal Unit (15) is provided to operate the machines (11). The system (1) according to any of claims 4-7, wherein the meter (9) comprises a modem (10) for transmitting measured immediate power to the network management system (3) and for receiving control messages, and wherein the meter (9) and the power limiter (4) are communicatively connected for communicating the first and / or the second adjustable power limit (Pmax1, Pmax2). Method for checking an electrical power from an electricity network (2) to a plurality of charging stations (5) and / or vice versa, wherein the electricity network (2) has a varying power consumption and comprises a network management system (3) for managing of the power consumption on the electricity grid (2), and wherein each charging station (5) has a plurality of charging points (7) for connecting electric vehicles (8); - wherein each charging station (5) is coupled to the electricity grid (2) by means of a power limiter (4) with a first adjustable power limit (Pmax), wherein the power limiter (4) is provided for limiting the power supplied from the electricity grid (2) to the charging station (5), and wherein the power limiter (4) comprises communication means for communicating with the network management system (3); - and wherein the network management system (3) is provided with control means for setting the first adjustable power limit (Pmax1) in each of the power limiters (4) depending on the varying power consumption of the electricity network (2). which comprises the following steps: a) measuring the varying power consumption on the electricity network (2); b) determining a maximum permitted power for each charging station (5); c) setting the maximum permitted power as the first adjustable power limit in each power limiter (4). The method of claim 9, wherein each charging station is provided with a charging station management system (6) for controlling power flows from and / or to the individual charging points (7), and wherein the method further comprises step d) prior to step c) of communicating the first adjustable power limit (Pmax1) to each power limiter (4). The method of claim 10, wherein the method in step d) further comprises communicating price information. (15) The method according to any of claims 9-11, wherein the system (2) is further provided for supplying electrical power from the electric vehicles (8) through the charging station (5) to the electricity grid (2), and wherein step c) comprises setting a second adjustable power limit (Pmax2) of the allowed power that is sent to the electricity network (2). The method of any one of claims 9-12, wherein the power limiter (4) comprises a Remote Terminal Unit (15), and wherein the charging station (4) comprises at least one automaton (11) for connecting a group (14) of charging points (7) with the electricity network (2), and wherein in step c) the Remote Terminal Unit (15) operates the automatons (11) for limiting the first and / or the second adjustable power. The method of any one of claims 9-13, wherein the charging station (5) further comprises a meter (9) for measuring the power flowing from the electricity grid (2) to the charging station (5) and / or vice versa, and wherein the meter (9) comprises a modem (10) for transmitting measurement data to the network management system (3) and for receiving control messages, and wherein the method further comprises the step of communicating the first and / or the second adjustable power limit (Pmax1, Pmax2) through the meter (9) on the power limiter (4).