WO2013001501A1

WO2013001501A1 - Net connection for charging rechargeable power units in group

Info

Publication number: WO2013001501A1
Application number: PCT/IB2012/053311
Authority: WO
Inventors: Eric Vandewinckel
Original assignee: EANDIS
Current assignee: EANDIS
Priority date: 2011-06-28
Filing date: 2012-06-28
Publication date: 2013-01-03
Anticipated expiration: 2013-12-28
Also published as: BE1020037A3

Abstract

A system (1) and a method for controlling electrical power (PT) 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 wherein each charging station (5) has a plurality of charging points (7) for connecting the rechargeable power units (8), wherein each charging station (5) is coupled to the electricity network (2) by means of a power delimiter (4) with an adjustable power limit ( Pmaxl) for delimiting the power supplied from the electricity network (2) to the charging station (5) depending on the varying power consumption from the electricity network (2).

Description

NET CONNECTION FOR CHARGING RECHARGEABLE POWER UNITS IN

GROUP

FIELD OF THE INVENTION

The invention relates to a system and a method for managing electrical power supplied from an electricity network 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 rechargeable electric power units, for example those of electric vehicles. PRIOR ART

Systems for generation and distribution of electrical energy are known. To ensure the stability of the electricity networks, it is important to ensure that the total power generated and the total power consumed are balanced at any time. Until a few decades ago, the energy generation (the so-called "energy injection" into the network) was mainly supplied by operators of large power plants (e.g. gas plants, coal plants, nuclear power plants) with a capacity of e.g. 250 MWatt per plant or more. A large number of consumers are connected to the network, both large consumers such as industrial users (factories), as well as less large consumers such as offices, and residential consumers. Control systems should ensure that the generated amount of energy is always equal to the amount of energy consumed, by ensuring at any time that the total amount of energy generated by the power plants corresponds to the total amount of energy consumed by the end-users. In practice, this means that power plants should produce more energy at times of high demand (e.g. during the so-called "peak hours"), and should produce less at times of low demand (e.g. at night). The total energy production capacity should be sufficiently large to deliver the peak power, otherwise the network voltage becomes unstable, possibly leading to a power outage. To minimize the occurrence of power outages, the energy producers therefore provide a production capacity which is considerably higher than the average power consumption, to deal with the peak power. In practice, this is a costly business, since the peak power is only required during, e.g. a hundred hours per year, while the power investment for the necessary infrastructure will be significant.

Another problem is that the energy consumption may change very quickly over time, and to maintain the stability of the network, the total power generated should be able to follow these rapid changes. Since the production capacity of large power plants cannot be changed rapidly, also smaller power plants are necessary which are only switched on when the demand is high, and which often have a lower expected efficiency than the larger power plants, but which are necessary to meet the rapid changes of the electricity demand. Alternatively, the production capacity of large power plants (e.g. if they run on "full speed") cannot be phased out quickly, leaving a surplus energy on the network when the electricity demand is suddenly reduced.

In the past, attempts have been made to reduce the peak power consumption by, e.g. the introduction of a multiple rate (e.g. cheap night rate) such that users may shift a part of their consumption (e.g. for washing machines) to the night-time instead of the daytime, and the balance between supply and demand was (mostly) maintained by increasing the production on the basis of good predictions, by importing energy from abroad, by the use of hydro-electrical power plants (e.g. the hydro-electrical power plant of Coo / Trois-Pbints in Belgium) which are able to deliver electricity at one moment by having water flowing from higher grounds through pipes and by driving turbines, and at another time (e.g. at night) to consume energy to pump the same water back up, etc.

With the advent of distributed energy production with on the one hand a very irregular production capacity, such as wind turbines, CHP (combined heat and power plants), solar panels, and on the other hand the explosive growth of the demand for electricity by, for example, electric vehicles, whose power units must be charged, the problem to maintain the stability of the network voltage has not become easier. On the contrary, the energy producers not only need to take into account an ever increasing demand (peak consumption), but also need to balance the network despite the highly variable power consumption and variable power injection.

From EP-A-0015666 a system is known for controlling electrical power consumption. The system comprises a first control unit which controls a number of circuit breakers, and which can be remotely programmed by the energy distributor. Using this first control unit, the energy distributor is able to limit the power of the connected consumer. The system further comprises a second control unit which also controls a number of circuit breakers, and which is programmed by the consumer himself to maintain the power consumption below a preset limit, and if necessary, to switch off sub circuits with a low priority.

A drawback of the system known from EP-A-0015666 is that, when the distributor in the first control unit sets another program, there may be a risk that some sub circuits of the consumer with a high priority may be switched off.

From EP-A-2219278 a system is known with which a consumer may manage its own power consumption in order to keep it within certain limits. With such a system, no control by the distributor is possible.

From EP-A-0717487 a system is known, a consumer may manage its power consumption therewith to keep it as close as possible to a predetermined limit. With this system, no control by the distributor is possible.

From WO-A-2011134861 a distributed system is known for the supply of electricity to a plurality of geographically distributed rechargeable power units, e.g., those of electric vehicles. A central control unit is provided to control, i.e. to optimize in time, the supply of electrical power to the rechargeable power units, on the basis of calculated charge priorities, thereby taking into account contractual obligations.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a system and method, by means of which the risk may be limited that the sub- circuits or the charging points may be switched off in an undesirable manner.

This object is achieved according to the invention as defined in the independent claims.

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

In this patent document, the terms "demand" and "electricity consumption" and "power consumption" have the same meaning, unless explicitly stated otherwise.

In this patent document, the terms "offer" and "electric- ity production" and "power injection" have the same meaning, unless explicitly stated otherwise.

As the charging station is coupled to the electricity network by means of a power delimiter, the power that is consumed by the charging station for charging the rechargeable power units, such as batteries of electric vehicles, can be delimited to a certain value which the electricity network can deliver without compromising the stability of the network. Without the power delimiter, the charging station would be able to choose for itself how much power it draws from the network, even at times when the network is already heavily loaded, or even critically loaded.

Because the power delimiter has an adjustable power limit, which is adjustable by the network management system, the power limit may be dynamically adjusted according to the needs and capabilities of the electricity network, which may change at any moment of the day. For example, the network management system may decide to decrease the total power offered to the charging station at times when the network is already heavily loaded and when it has, or is likely to get insufficient capacity. In an extreme case (e.g. with congestion problems), the charging station may even be temporarily completely disconnected from the network. Because the recharging of rechargeable power units is not a time-critical application, the charging may be temporarily delayed at times when the network cannot or can hardly meet the demand. On the other hand, it may be appropriate at other times to increase the power limit in order to take advantage of available energy from renewable energy generation. By controlling the power delimiter from the network management system and not from the charging station, the varying power consumption may be more quickly anticipated, which further increases the network stability.

By providing each charging station having a plurality of charging points with a power delimiter, a (relatively) large power consumption may be reduced in a (relatively) simple way, such that the stability of the network can significantly improve.

By delimiting the power by means of a power delimiter with an adjustable power limit instead of a switch with a fixed predetermined maximum value, a reliable system is obtained which can act dynamically depending on varying conditions, but in a way that is much less drastic than merely completely disconnecting consumers. In this way, the needs and desires of both the network 2 and the charging stations 5 may optimally be combined. ¹

Moreover, each charging station is provided with a recharging station management system for managing power flows from and 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 adjustable power limit before setting the first adjustable power limit.

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 may remain limited, and the charging station may largely retain its flexibility towards the individual power units.

By communicating changes of the allowed maximum power to the charging station before effectively setting the (new) power limit, the charging station may optimally adapt to the new situation and decide for itself which sub circuits or recharging stations to switch off, or more generally in which way to limit the power before the (new) power limit is imposed. In this way, the unwanted switching off of sub circuits or recharging points can be avoided. Preferably, the network management system is further provided for transmitting price information in function of the power limit, to the charging station management system.

This allows the station administrator to adjust the price for recharging the rechargeable power units to the price which he himself must pay to the network operator. In the case of directly charged electric vehicles, the owners thereof, for example based on this price (or e.g. predetermined maximum charging rates) may decide to postpone the charging. By dynamically increasing the price of electricity at times of heavy network load, the network administrator may decrease the demand for electricity, such that less power will be consumed, which is beneficial for the stability of the network.

Preferably, the charging station further comprises 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 network management system obtains information about the instantaneous power of each charging station, which may be (considerably) lower than the set power limit. Hence, the network management system obtains a better understanding of large consumers, and it may also better respond to the actual need.

Preferably, the system is further provided for supplying power from the power units by the charging station to the electricity network, and the power delimiter is provided with a second adjustable power limit to delimit the power supplied to the electricity network.

By allowing the charging stations to direct energy from the power units and preferably also from renewable sources (e.g. wind turbines, solar panels, etc.) or other energy storages (such as electric batteries, compressed air energy systems, etc.) into the network, the charging stations may also act as energy suppliers. In order to avoid and to delimit an over-supply of energy into the network, in this case, preferably the power delimiters are provided to delimit the flow in the direction of the charging stations to the network according to a second adjustable power limit, which can be set by the network management system, which is beneficial for the stability of the system once again, this time by delimiting the over-supply of power to a minimum.

In an embodiment, the power delimiter comprises a Remote Terminal Unit (abbreviated as RTU), also called Remote Telemetry Unit. i .

The RTU is a control and communication module capable of receiving information via a communication port (e.g. an Ethernet connection or a serial port or the like) from a management system and converting it into a control signal via an output port (e.g. a potential free contact). Via an input port, an RTU may receive measurement signals and send these measurement signals via a communications protocol to a management system.

In an embodiment, the charging station comprises at least one automatic device for connecting a group of charging points to the electricity network, wherein the Remote Terminal Unit is provided to operate the automatic devices.

Preferably,¹ the network management system will switch the totality of the charging stations off or on, and not the individual charging stations themselves. The latter is a responsibility of the charging station management system.

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

When the charging station comprises a meter with communication means, such as a modem, data can be sent to the network management system, receiving accurate information on the instantaneous consumed or generated power from the charging station, such that it gains more insight in the consumers (or suppliers) in order to better set the power limits to better ensure the stability of the system and to optimally take into account the capabilities of the charging stations.

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

More generally, the principle of the invention can also be applied to a system and method for delimiting power to any type of consumer, i.e., not only charging stations for power units of electric vehicles. When applying the principle in such a system or process, in the text of this description, the terminology is adapted as follows:

- "Charging station" is replaced by "consumer";

- "Charging point for connecting a rechargeable power unit" is replaced by "sub circuit for connecting electricity-consuming and/or supplying appliances";

- "Charging station management system" is replaced by "consumer management system."

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further elucidated on the basis of the following description and the accompanying figures. Note that the figures are not necessarily drawn to scale, and that the proportions of the components do not necessarily correspond with reality. The figures serve to describe the principles of the invention. Similar elements are numbered the same on the different 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 delimiter having a first adjustable 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 which is communicatively connected to the network management system.

Fig 4 shows an embodiment of a system according to the invention, wherein the power delimiter has a second adjustable power limit for delimiting the power supplied by the charging station to the network. Fig 5 shows an embodiment of the charging station of

Figure 3 in more detail.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

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

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 circumstances and the embodiments of the invention may be used in other sequences than the ones described or illustrated herein.

The term "comprising", used in the claims, should not be interpreted as being restricted to the means mentioned thereafter and does not exclude other elements or steps. The term should be interpreted as specifying the presence of the above-mentioned features, elements, steps or components which are referred to, but does not excludes the presence or 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 consisting only of components A and B. It means that with respect 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 delimiter

5 charging station

6 charging station management system

7 charging points

8 electric vehicle

9 meter

10 modem

11 automatic device

12 motor

13 control means

14 group of charging points

15 RTU

16 communication connection

17 relay

PT total capacity of the charging station

Pmaxl first adjustable power limit

Pmax2 second adjustable power limit

P1 power of the first charging point

Hereafter, the invention is explained in more detail with reference to its application to a charging station with a plurality of charging points for connecting rechargeable power units for e.g. electric vehicles. As mentioned above, the principles described below can also be applied to consumers with a plurality of sub-circuits for connecting electricity-consuming and/or electricity-supplying devices.

Fig 1 shows a system 1 with an electricity network 2 (e.g., a low-voltage network of 220 V) with a network management system 3, and a charging station 5 with a plurality of charging points 7 (e.g., "charging poles"), e.g., at least two, preferably at least five, more preferably at least ten, for charging power units of electric vehicles (not shown). Usually, each charging point 7 can charge one unit. A charging point 7 may, for example, be physically implemented as a socket on a charging pole, wherein the charging pole may contain one or more sockets. Hence, the battery of the vehicle acts as an energy consumer. In practice, a large number of other consumers (electric appliances, lighting, motors, etc from factories, offices, houses) are also connected to the network 2, but these are not shown to simplify the figures.

In the example of Figure 1 , the charging station 5 has its own management system 6 that is managed by the operator of the charging station 5 and that controls the power supply to each charging pole 7. In an embodiment, the charging unit 5 may comprise a payment terminal and an electric circuit to switch on or off the power supply P1 , P2, Pn of the electricity network 2 to each charging point 7, and each charging point 7 typically comprises its own power meter coupled to the charging station management system 6. The details of the internal operation of a charging station 5 are outside the scope of the present invention. The total sum of the power P1 to Pn of the individual charging points 7 is equal to the total power PT that should be supplied by the electricity network 2. This total power PT usually varies as a function of time, hence PT(t). In existing systems, this total power PT has a non-variable delimiter from the electricity network 2, hence the network 2 should supply the required power, and this power may increase as more units are to be charged. This situation may 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, i.e. higher than the power production of e.g. the power stations (not shown) that inject power into the electricity network 2. Even a situation where in the power consumption is 1 ,5 % lower than the power production is a very critical situation.

Figure 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 of 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 maximum allowed power of the different charging stations 5, the network management system 3 ensures that the capacity of the network 2 is not exceeded, and that the stability is not compromised. The main differences with the system of Figure 1 is that the system 1 of Fig 2 comprises a power delimiter 4 with an adjustable power limit Pmaxl for delimiting the power P(t) supplied by the electricity network 2 to the charging station 5 up to a first maximum allowed value, which is determined and set by the network management system 3. Preferably, the power delimiter 4 is situated between the charging station 5 and the electricity network 2. The power limit Pmaxl (t) can be transmitted from the network management system 3 as a function of the varying power consumption on the network 2 by using communication means to communicate the allowed power limit Pmaxl to the power delimiter 4, and by means for effectively setting this power limit Pmaxl . As a communication tool 16, "Power Line" communication is preferably used (a communication system wherein communication signals are superimposed upon the power lines), but other communication means such as ADSL, LAN (local area network), GSM, GPRS, SMS, POTS (normal telephone line) may also be used. In this way, the network management system 3 may delimit the power consumption PT(t) of the charging station 5 as a function of time, in accor- dance with the available capacity of the electricity network 2, taking into account the varying power consumption on the network 2, such that the stability of the network 2 increases. Obviously, the adjustable power limit Pmaxl may be different for each charging station 5.

Preferably, the network management system 3 is provided with a charging station management system 6 for the management of power flows from and/or to the individual charging stations 7, and the network management system 3 is communicatively coupled to the charging station management system 6 to communicate changes in the first adjustable power limit Pmaxl before setting the first new power limit Pmaxl . Such a system 1 is shown in Fig 3. By communicating in advance, the charging station 5 is offered the opportunity to optimally adapt to the new situation, e.g. by changing its internal configuration. For instance, a charging station management system 6 could e.g. decide to provide power to certain charging

I

points 7a, 7n, and not to other charging points (e.g. 7b in Fig 2). In another example, the charging management system 3 could apply e.g. time- multiplexing in such a way that the sum of the powers P1 , P2, etc. of the charging points 7a, 7b, etc, at any time is less than the maximum allowable power limit Pmaxl . In that case, the units 8a, 8b, etc. could alternately be charged during certain periods. The chosen strategy to make the total consumed power P smaller than the imposed power limit Pmaxl , is preferably left to the charging station 5 itself, and has no effect on network stability as long as the total consumed power P is smaller than the power limit Pmaxl . In this way, the complexity on the side of the network 2 is decreased, yet the energy consumption of a large group of consumers, 8 can be kept under control.

Preferably, the network management system 3 is further provided for the transmission of price information as a function of the power limit Pmaxl to the charging station management system 6. The price information can e.g. dynamically be transmitted in the form of a schedule of rates as a function of power. This is like a gentle way to decrease the demand for electricity by the charging stations 5 at times of high power consumption (e.g. peak moments), or to request an increased fee when the network operator has to deploy additional resources (e.g. diesel generators), which are often more expensive, for the extra energy production. This allows the operator to attempt to shift the peak power consumption to less congested periods, although only a price increase is no guarantee thereto. The power delimiter as described above is, though.

The charging station 5 of Figure 2 has a meter 9 for measuring the instantaneous power P of the total charging station 5, which e.g. may be much lower than the preset power limit Pmaxl . Preferably, this meter 9 has means of communication such that the meter can be remotely read out by the network management system 3.

Fig 4 shows a variant of the system 1 of Fig 3, wherein the charging unit 5 supplies power to the electricity network 2, hence in the opposite direction. In this case, the batteries serve as an energy source for electric vehicles 8. Batteries for electric vehicles 8 have a power capacity in the order of 10 to 23 KWatt. Preferably, the power delimiter 4 is in this case provided to delimit the power supplied to the network 2 to a second maximum value Pmax2. By allowing the charging stations 5 to direct energy from the batteries to the network 2, the charging stations 5 may temporarily act as energy suppliers. This could be interesting for the network operator to absorb sudden increases in power consumption on the network, because the energy from batteries 8 is very quickly available, unlike other energy sources that sometimes require several minutes before they are able to deliver enough power. The principle of using power units for electric vehicles for temporary energy storage during times of low usage on the network (e.g. at night), and of using it as an energy source during times of high consumption in the network (e.g. during peak moments) may also provide other benefits, such as reducing the infrastructure costs of the network operator. However, the feasibility and financial aspects of such applications are outside the scope of the present patent application.

The system 1 of Fig 4 functions very similar to that of Figure 2, except that the power PT is limited in the other direction, in particular, the power that is supplied to the network is limited to a maximum value Pmax2. The second power limit Pmax2 is set by the network management system 3 depending on the heeds and requirements of the network 2 to guarantee the stability of the network, and is, among others, dependent on the varying power consumption. Preferably, pricing information is also here communicated in advance to the charging management system 6, this time the price the network operator is willing to pay to the charging station 5 for receiving power, while the station manager in turn can decide which batteries for the proposed price are eligible to supply power, and which are not. As described above, the details of the interactions within the charging station 5 are of no importance for the network management system 3, as long as the power delivered to the network does not exceed the second adjustable Pmax2 power limit. Note that the value of the second adjustable power limit Pmax2 may vary for each charging station 5.

Fig 5 shows an embodiment of the charging unit 5 of Fig 3 in more detail. The charging points 7 of the charging station 5 of Figure 5 are grouped into one or more groups 14, each comprising one or more charging points 7. In the example of Figure 5, a group 14 is shown with three charging points 7, but also more or less charging points 7 per group 14 may be grouped together. The power of the electricity network 2 to each group 14 (or vice versa) flows through an automatic device (also called maximum switch, circuit breaker or automatic fuse), which can be switched on or off mechanically by means of a motor 12, so as to optionally connect the group 14 of charging points 7 to the network 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, also another device could have been used that converts communication signals into control signals, and that converts measured data into communications signals. The power meter 9 would also contain these functionalities. The logic to compare the measured (instantaneous) power with the limit value Pmaxl or Pmax2, and as a result of an overrun , to execute a command, can either be present locally in the RTU, or in the network management system 3, or both. If the automatic device 11 is switched off, the power PG1 of the group 14 is equal to zero, and thus the power units of the vehicles 8a, 8b of the group 14 may not consume (or supply) power to the network 2. The more groups 14 with automatic devices 11 a charging station 5 has, the more accurately the total power P 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 one single vehicle. In that case, the Remote Terminal Unit 15 should operate the automatic devices 11 for each charging point 7 individually.

However, systems 1 other than that of Fig 4 are also possible, and the power delimiter 4 may take on' other forms. E.g. in case the charging station 14 applies time-multiplexing and internally ensures that PT < Pmaxl (or Pmax2), wherein the variable power limit Pmaxl , Pmax2 is imposed by the network management system 3, the power delimiter 4 may be e.g. one single switch operated from the network management system 3, and which can switch off the entire charging station 5 if it does not comply with the maximum power limit Pmaxl (or Pmax2).

Although the present invention has been described with reference to specific preferred embodiments, it will be appreciated that various modifications can be made to these embodiments without departing from the scope of protection 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

1. A system (1) comprising:

- an electricity network (2) with a 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 rechargeable power units, such as for example those of electric vehicles (8);

characterized, in that

- each charging station (5) is coupled to the electricity network (2) by means of a power delimiter (4) having a first adjustable power limit (Pmaxl), wherein the power delimiter (4) is provided for delimiting the power supplied by the electricity network (2) to the charging station (5), and wherein the power delimiter (4) comprises communication means for communicating with the network management system (3);

- the network management system (3) is provided with control means for adjusting the first adjustable power limit (Pmaxl) in the power delimiters (4) depending on the varying power consumption of the electricity network (2); and

- each charging station (5) is provided with a charging station management system (6) for managing power flows from and/or to the individual charging stations (7), and wherein the network management system (3) is communicatively coupled to the charging station management system

(6) to communicate changes in the first variable power limit (Pmaxl) before setting the first adjustable power limit (Pmaxl).

2. The system (1) according to claim 1 , wherein the network management system (3) is further provided for transmitting price information in function of the power limit, to the charging station management system (6).

3. 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).

4. The system (1) according to any one of the preceding claims, wherein the system is further provided for supplying electrical power coming from the rechargeable power units (8) through the charging station (5) to the electricity network (2), and wherein the power delimiter (4 ) is provided with a second adjustable power limit (Pmax2) to delimit the power supplied to the electricity network (2).

5. The system (1) according to any one of the preceding claims, wherein the power delimiter (4) comprises a Remote Terminal Unit (15).

6. The system (1 ) according to claim 5, wherein the charging station (5) comprises at least one automatic device (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 automatic devices (11).

7. The system (1) according to any one of claims 3 - 6, wherein the meter (9) comprises a modem (10) for the transmission of measured instantaneous power to the network management system (3) and for receiving control messages, and wherein the meter (9) and the power delimiter (4) are communicatively connected for communicating the first and/or the second adjustable power limit (Pmaxl , Pmax2).

8. Method for managing electrical power supplied 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 the power consumption on the electricity network (2), and wherein each charging station (5) has a plurality of charging points (7) for connecting rechargeable power units (8);

- wherein each charging station (5) is coupled to the electricity network (2) by means of a power delimiter (4) having a first adjustable power limit (Pmax), wherein the power delimiter (4) is provided for delimiting the power supplied by the electricity network (2) to the charging station (5), and wherein the power delimiter (4) comprises communication means for communicating with the network management system (3);

- wherein the network management system (3) is provided with control means for adjusting the first adjustable power limit (Pmaxi) in each of the power delimiters (4) depending on the varying power consumption of the electricity network (2);

- and wherein each charging station is provided with a charging station management system (6) for controlling power flows from and/or to the individual charging stations (7), wherein the network management system (3) is communicatively coupled to the charging station management system (6) to communicate changes in the first variable power limit (Pmaxi);

the method comprising the following steps:

a) measuring the varying power consumption on the electricity network (2);

b) determining the first adjustable power limit (Pmaxi) for at least one of the charging stations (5);

c) communicating the first adjustable power limit (Pmaxi) to the charging station management system (6) of the at least one charging station (5), and subsequently

d) setting the first adjustable power limit (Pmaxi ) in the power delimiter (4) of the at least one charging station (5).

9. The method according to claim 8, wherein the process in step c) further comprises communicating price information.

10. The method according to any one of claims 8 - 9, wherein the system (2) is further provided for supplying electrical power from the rechargeable power units by the charging station (5) to the electricity network (2), and wherein step d) comprises setting a second adjustable power limit (Pmax2) of the allowed power that is transmitted to the electricity network (2).

11. The method according to any one of claims 8 - 10, wherein the power delimiter (4) comprises a Remote Terminal Unit (15), and wherein the charging station (4) comprises at least one automatic device (11) for connecting a group (14) of charging points (7) with the electricity network (2), and wherein in step d) the Remote Terminal Unit (15) operates the automatic devices (11) for delimiting the first and/or the second adjustable power. 2. The method, according to any one of claims 8 - 11 , wherein the charging station (5) further comprises a meter (9) for measuring the power flowing from the electricity network (2) to the charging station (5), and/or vice versa, and wherein the meter (9) comprises a modem (10) for the transmission of 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 (Pmaxl , Pmax2) by the meter (9) to the power delimiter (4).