EP3934931A1

EP3934931A1 - Charging station for charging electric vehicles

Info

Publication number: EP3934931A1
Application number: EP20709540.7A
Authority: EP
Inventors: Johannes BROMBACH; Christian STRAFIEL; Alfred Beekmann
Original assignee: Wobben Properties GmbH
Current assignee: Wobben Properties GmbH
Priority date: 2019-03-06
Filing date: 2020-03-04
Publication date: 2022-01-12
Also published as: US20220185141A1; CN113544006A; DE102019105661A1; WO2020178341A1

Abstract

The invention relates to a charging station (1) for charging electric vehicles (24), comprising a plurality of AC charging terminals (6), each for charging an electric vehicle (24) by means of alternating current, wherein each of the AC charging terminals (6) is connected to a three-phase current supply (12) via a phase-change device (18) in order to be supplied thereby with three-phase electrical current, wherein the current supply (12) has three supply lines (21, 22, 23) for providing three voltage phases, and each AC charging terminal (6) has three connection lines (31, 32, 33) for connecting to the three supply lines (21, 22, 23) for applying the three voltage phases to the connection lines (31, 32, 33), wherein each phase-change device (18) is configured to change a connection allocation between the three supply lines (21, 22, 23) and the three connection lines (31, 32, 33).

Description

Charging station for charging electric vehicles

The present invention relates to a charging station for charging electric vehicles and it also relates to a method for charging electric vehicles.

Electric vehicles are enjoying increasing popularity and so more and more and larger charging stations are required to charge electric vehicles. Large charging stations, which can also be referred to as charging stations, can charge many electric vehicles with electricity at the same time. Such a charging station usually receives the power required for this from an electrical supply network to which it can be connected via a network connection point. Particularly in the case of large charging stations, their power requirements can have a noticeable impact on the electrical supply network. Network sections or the network connection point can sometimes reach a performance limit.

To counter this, the electrical supply network and / or the network connection point can be expanded with regard to the performance or the ability to transmit power. However, it is not only the level of performance that can be problematic, but also the power quality, which can be influenced by the charging station. A charging station for charging electric vehicles converts the electrical, three-phase alternating current, which is drawn from the electrical supply network, into direct current. Different charging technologies can be used in the various types of electric vehicle be installed. In addition to DC fast charging options, almost all vehicles, at least many vehicles, also have so-called in-vehicle chargers installed. These convert an alternating current into a direct current themselves, so they have an AC input and can therefore also be referred to synonymously as AC chargers. Such in-vehicle chargers are either single-phase, two-phase or three-phase connected to an AC connection. In this case, the electric vehicle is supplied with one-, two- or three-phase alternating current and the conversion into direct current, i.e. into a DC charging current, only takes place in the electric vehicle.

Which phases of a three-phase supply line, which is connected directly or indirectly to the electrical supply network, especially at the network connection point, is mostly random. This can lead to a strong asymmetry of the AC system when several vehicles are to be charged. If, for example, to use a simplistic example, three electric vehicles are charged via their in-vehicle charger, which only works in one phase, the load on the three-phase system in the charging station can be even if each in-vehicle charger is from a different one of the three phases Electricity. But if, for example, all three vehicles with their in-vehicle charger happen to draw their power from the same phase, for example from the first phase, this first phase is heavily loaded and the second and third phases are not or less. Accordingly, there is an asymmetrical load that can affect the electrical supply network from the charging station.

To counter this problem, an attempt can be made to specify one of the three phases as the preferred phase at each AC charging point, i.e. at which an electric vehicle with an in-vehicle charger is to be connected, with this preferred phase changing from one AC charging point to the next. However, this does not take into account that the in-vehicle chargers require different amounts of electricity depending on the vehicle and charge level. If, for example, there are six AC charging points, two each are provided for the first, two for the second and two for the third phase, an asymmetry can still occur if, for example, two vehicles require only little charging current at both AC charging points in the first phase , whereas two vehicles are connected to two additional AC charging points for the second phase, which require a high charging current. The same applies if electric vehicles are connected and charged at the six AC charging points mentioned as an example, for example only at the two AC charging points for the first phase. In addition, there are two-phase and three-phase chargers in addition to single-phase in-vehicle chargers.

It can also happen that, for example, in so-called fleet operations, where a transport or logistics company has many electric vehicles and operates its own charging station, many AC charging points are combined with few quick charging points. The reason for this is that, in such a case, the vehicles in the fleet are often charged in a continuous night charge, for which many AC charging points are required. In addition to this, however, a few quick charging points can be provided if a vehicle in the fleet has to be charged in the meantime and such charging cannot wait until night charging. Such fast charging points are those which have DC choppers for providing a DC charging current in order to generate high direct currents for fast charging. Such DC choppers as part of the fast charging points are then part of the charging station and can be connected in three phases to a corresponding three-phase supply line in the charging station. It should also be noted that some charging stations have such a combination of DC chargers and AC charging points.

Such a structure can also influence the symmetry of the three-phase supply system in the charging station and thus the symmetry in the electrical supply network to which the charging station is connected. The German Patent and Trademark Office researched the following prior art in the priority application for the present application: DE 10 2013 204 256 A1, DE 10 2017 116 886 A1, EP 3 184 352 A1, EP 3 549 814 A1, WO 2012/128 626 A2.

The present invention is therefore based on the object of addressing at least one of the problems mentioned. In particular, a solution is to be proposed by means of which a charging station achieves the most symmetrical possible loading of a three-phase supply connection. At least an alternative solution to previously known solutions should be proposed.

The invention is thus based on a charging station for charging electric vehicles with several AC charging terminals. Each AC charging terminal is designed to charge an electric vehicle with alternating current. In addition, each AC charging terminal is connected to a three-phase power supply via a phase change device, in order to be supplied with electrical three-phase power. The Power supply thus has three supply lines for providing three voltage phases. Each of the three supply lines thus has a voltage phase during operation. For this purpose, for example, a three-wire cable or a corresponding rail system with at least three rails can be provided. Each AC charging terminal, which can also be referred to synonymously as an alternating voltage charging terminal, has three connection lines for connection to the three supply lines of the power supply, in order to apply the three voltage phases of the three supply lines to the three connection lines. A supply line is therefore electrically connected to a connection line. In this way, every AC charging terminal is connected to the power supply.

Each phase change device is set up to change a connection assignment between the three supply lines and the three connection lines. For example, at an AC charging terminal, the first connection line can be connected to the first supply line and the second connection line to the second supply line and finally the third connection line to the third supply line. The phase change device can change this assignment, for example for the example mentioned to an assignment in which, after a change, the first connection line is electrically connected to the second supply line, the second connection line is electrically connected to the third supply line and the third connection line is electrically connected to the first supply line. Yet another change can be made, after which, to stay with the last-mentioned example, the first connection line is electrically connected to the third supply line, the second connection line is electrically connected to the first supply line and the third connection line is electrically connected to the second supply line. These two changes in the strand assignment, described by way of example, and thus a change in the phase assignment can also be understood as a rotation of this assignment and to this extent the phase change devices can each also be designed as phase rotation devices. Theoretically, however, further changes in the assignment between connection lines and supply lines come into consideration, for example, to take up the above example again, so that the first connection line is connected to the first supply line, but the second connection line is connected to the third supply line and the third connection line with the second supply line. This change serves to change the load on the three phases. As long as each AC terminal only accesses one phase or, when accessing two or three phases, accesses these in the same way, i.e. draws the same amount of current, the last-mentioned change, in which only the last two phases were swapped, is basically superfluous. It would then suffice if the phase change device can only advance or turn back the connection for all three strands by one step, or for all three strands by two steps.

The phase change device can in principle be designed mechanically, in which even a rotary switch or slide switch always changes the electrical connection for three phases, that is to say for each of the three strands mentioned. However, it is also possible to implement this with power semiconductor switches, for example with IGBTs or thyristors. The use of power semiconductor switches has the advantage that electronic control of these phase change devices can be better achieved and that no signs of wear and tear can occur on switch contacts.

This use of the phase change devices ensures that the connection lines can each be connected to the supply lines in such a way that, if possible, all three phases are loaded equally. Since all AC charging terminals, at least all AC charging terminals under consideration, have such phase change devices, a load on the three phases that is as uniform as possible can be achieved for all of these AC charging terminals.

A preferred embodiment, which can also be combined well with the other embodiments, is to provide a type of static phase symmetry. For this purpose, it is proposed that all phase change devices of the AC charging terminals not used at the moment be switched evenly between a position of 0 °, 120 ° and 240 °. This applies particularly to the case when the phase change devices are designed as phase rotation devices, but the same result can also be achieved with other phase change devices. Of the AC charging terminals that are not in use at the moment, one is accordingly set or switched so that the first phase of the power supply, which is referred to here as 0 °, is switched to the first connection string and the second phase to the second and the third phase to the third connection line. In another unused AC charging terminal, the first connection line is switched to the second phase of the power supply, i.e. the second supply line, and correspondingly the second connection line to the third phase and the third connection line to the first phase. In the case of another AC charging terminal that is not in use at the moment, the first connection line is switched to the third phase, i.e. 240 °, the second connection line to the first phase and the third connection line to the second phase.

This is based on the idea that single-phase in-vehicle chargers in particular are prepared by their connector so that they always use the same connector pin as the active connector pin and thus always get their power from the same connector line, for example always from the first one. This proposed static phase balancing now ensures that the first connection line is always connected to different supply lines. A one-sided loading of a connection line due to structural engineering as described is thus distributed as evenly as possible to the three supply lines by the phase change devices, and as a result a major first step towards symmetrical loading can be made. It should also be noted that this static phase balancing, in which the phase change devices of the unused AC charging points are preset, is carried out in the de-energized state and thus leads to a low load or low wear of the components involved, especially the phase change device.

A balancing control for controlling the phase change device is preferably provided, the balancing control being prepared to control the phase change devices in order to reduce, in particular to minimize, a phase asymmetry of the supply lines. Ideally, a phase symmetry of the supply lines, i.e. the three phases, is achieved. Whether a phase symmetry actually succeeds depends in particular on how many AC charging terminals the charging station has and, of course, what accuracy is used as a basis for such a phase symmetry.

In particular, the balancing control is designed such that it also quantitatively detects an asymmetry of the three phases of the power supply and can control the phase change devices individually in order to find and make a suitable setting for each phase change device. In addition or as an alternative, the balancing control can also quantitatively record the individual phase loads of each AC charging terminal and, depending on this, find a suitable connection assignment for each AC charging terminal, which leads to the most symmetrical load possible for all AC charging terminals of the charging station.

The balancing control preferably has both of the aforementioned pieces of information, that is, both the information on the individual loads on the individual AC charging terminals and the overall load or phase distribution of the power supply. The underlying idea here is that an asymmetry in the three phases of the power supply is not only due to the AC charging terminals, but can also depend on other connected loads. In this case, the information about the load on each AC charging terminal would not allow conclusions to be drawn about the overall load situation of the three phases of the power supply. For example, at least one active three-phase rectifier can be connected in the charging station, which can also lead to an asymmetrical load on the three phases of the power supply.

According to one embodiment, it is proposed that the balancing control be prepared to sort the AC charging terminals according to their current consumption and to control the phase change devices as a function of this in order to minimize the phase asymmetry of the supply lines. In this way, a complex optimization program that could also or alternatively be implemented in the balancing control, which is also proposed according to one embodiment, can be avoided.

This means that the AC charging terminals with the greatest current consumption can be viewed first and set to minimize asymmetrical loading. The AC charging terminals with the greatest current load therefore also have the greatest influence on the asymmetrical load. Additional AC charging terminals with lower power consumption can then be set downstream, for example. Even if the optimal setting of all phase change devices of the AC charging terminals is possibly not achieved as a result, a comparatively good result can still be achieved with significantly less optimization effort. In addition or as an alternative, it is proposed to sort the AC charging terminals according to whether they work single-phase, two-phase or three-phase. The underlying idea here is that, depending on whether you are working single-phase, two-phase or three-phase, changing the phase assignment will have different effects. This can be taken into account in a first step through such a sorting.

The balancing control may not be able to determine directly whether a single-phase, two-phase or three-phase so-called in-vehicle charger is connected. However, in any case according to one embodiment, it can each detect the current of the three connection lines of the relevant AC charging terminal and use this to identify which of the three connection lines carries a current and which does not. Such a measurement therefore shows whether the corresponding AC charging terminal is working single-phase, two-phase or three-phase.

If it has now been recognized that an AC terminal is working in three phases, this can sensibly be sorted out for the consideration of the balancing control or sorted backwards. The sorting can also provide that AC charging terminals that work in one phase are sorted to the front and those that work in two phases are considered in the sorting behind, that is, of secondary importance. At least it makes sense to sort single-phase AC charging terminals and two-phase AC charging terminals into different groups. This is based on the idea that when turning all three phases in the single-phase case, one phase is actually completely changed, for example, a change is made from a full load of the first phase to a full load of the second phase.

When changing all three phases of a two-phase AC charging terminal, in fact, only one of the two loaded phases is changed. For example, a change is made from uniform loading of the first and second phases to uniform loading of the second and third phases. In fact, this did not change the burden of the second phase.

It is particularly preferred to combine these two sortings and initially sort them according to the criterion of whether an AC charging terminal works single-phase, two-phase or three-phase and then sorted into the three resulting groups or, after sorting out the three-phase group, into the remaining two groups according to the current consumption . Then, for example, the most powerful can single-phase Charging terminals are changed for a first equalization of the load and then the most powerful AC charging terminals, which work in two phases, are used for a further equalization.

However, it is also possible that a sorting according to whether the AC charging terminals work single-phase, two-phase or three-phase is dispensed with if it should emerge that single-phase in-vehicle chargers are establishing themselves and therefore only single-phase in-vehicle chargers are to be expected anyway and that means that only AC charging terminals that work in single-phase can be expected anyway. Occasional inaccuracies due to the fact that a two-phase in-vehicle charger does occur can be accepted if, as described, the control effort can be reduced as a result.

According to one embodiment, it is proposed that the balancing control is prepared to sort the AC charging terminals, in particular with single-phase or two-phase power consumption, according to their current consumption, and to do this in such a way that for each of these AC charging terminals, the connection line with the greatest power consumption as The maximum loaded string is identified and its current consumption is taken into account as the maximum phase current of the AC charging terminal. Building on this, the AC charging terminals are then sorted according to their maximum phase current in a current sequence. Furthermore, the balancing control is prepared so that the phase change device sets or changes the connection assignment so that the maximum loaded strings are alternately connected to a first, second and third supply strand of the three supply strings according to the current sequence. In the case of the AC charging terminals with single-phase power consumption, the only string is also the string with the maximum load. This is then alternately connected from one to the next AC charging terminal to the first, second and third supply line or electrically connected to it.

In the case of the AC terminals with two-phase power consumption, there are two current-carrying strings, and theoretically they can also be loaded equally. One of these two strands can then be selected as desired, for example the first of the two strands. In the actual implementation, however, it will be the case that two identical currents are never measured and therefore one of the two strings will be identified as the string with the maximum load, no matter how small the lead over the other string. If this maximum loaded line of each AC charging terminal with two-phase power consumption is assigned to the first, second or third supply line, i.e. connected to it or electrically connected to it, it is proposed to connect the remaining second current-carrying line to the following supply line. For this purpose, the previously selected counting of the first, second and third supply line is used and accordingly the second supply line follows the first, the third supply line follows the second and the first supply line follows the third. Accordingly, the second current-carrying branch is connected to the second, third or first supply branch or is electrically connected to it.

This creates a clear specification and structure of action, according to which the maximum loaded strings and then the second current-carrying strings, if any, are connected to the respective supply strings. A complex optimization algorithm is not required for this. If AC charging terminals (6) with three-phase power consumption are also included, it is proposed in particular that one of the remaining strings be connected to the following supply line, namely the second, third or first supply line (22, 23, 21). Only one free supply line then remains for the remaining third line. An improvement or refinement can be achieved by initially sorting the AC charging terminals into a first and second group, namely the AC charging terminals with single-phase power consumption in a first group and the AC charging terminals with two-phase power consumption in a second group and optionally the AC charging terminals (6) with three-phase power consumption in a third group. The above-described division according to the maximum phase current and also the proposed sequence of connection to the relevant supply lines are then carried out in groups. This also means that in the first group, the line with the maximum load is the only line that carries current.

According to a special option, the following connection sequence is proposed for the maximum loaded strings. This can be done overall for all AC charging terminals with single-phase or two-phase or even three-phase power consumption or in groups for the first and second and possibly third groups. Accordingly, it is proposed that the first maximum loaded line, i.e. the maximum loaded line of the first AC terminal according to the sorting, be connected to the first supply line, the second maximum loaded line to the second supply line and the third maximum loaded line to the third supply line - strand. The first string with the maximum load, i.e. the string with the maximum load of the first AC terminal according to the sorting, the second string with the maximum load is the string with the maximum load for the second AC terminal, and so on.

For the fourth to sixth, however, a reverse order is proposed, so that the fourth maximally loaded line is also connected to the third supply line, the fifth maximum loaded line to the second supply line and the sixth maximum loaded line to the first supply line. The first and sixth maximum loaded line are then connected to the first supply line.

This reversal of the sequence for the fourth through the sixth prevents the first supply line from being loaded more heavily than the other two supply lines. This risk would exist if the first supply line were connected to the maximum loaded line and the fourth maximum loaded line. In addition, it is proposed that this principle also be proposed for the other lines, i.e. especially to connect the seventh to ninth maximum loaded line to the first to third and to reconnect the tenth to twelfth maximum loaded line to the third to first supply line in reverse order, and so on.

According to one embodiment, it is proposed that the sorting is generally carried out with the reverse sequence, i.e. starting with the last maximally loaded line and then continuing the sequence with the penultimate, maximally loaded line, etc. until finally the first maximally loaded line. In this way it can be achieved that in the first re-sorting steps, no changes in the current that are too great are made. Starting with the strand that carries the greatest current could, in the worst case, lead to a temporary strong increase in the asymmetry. But if you start with the smallest currents, the strands with the largest currents are first swapped when a symmetry has already been partially achieved. In particular, sorting with the reverse sequence is proposed so that the last line with the maximum load is started and this is connected to the first supply line, the penultimate line with the maximum load is connected to the second supply line, and the third from the last line with the maximum load is connected to the third Supply line. Then the sequence is reversed again so that the fourth from last line with maximum load is also connected to the third, supply line, the fifth last to the second and the sixth from last to the first. The balancing control is especially prepared to carry out all the described functionalities in that it has a corresponding control program that can be implemented, for example, on a process computer that can form part of the balancing control. Furthermore, data channels, especially data lines, are provided in order to connect the balancing control to the AC charging terminals, especially in order to be able to control the respective phase change device. This can also be used to transfer sensor data from current measurements for balancing control.

Corresponding current sensors can be provided on the AC charging terminals for such sensor data, and that can also mean that such current sensors are provided on the phase change devices or the connection lines. It is also possible that each AC charging terminal has its own current sensors and transmits the corresponding data to the balancing control via corresponding data channels, such as data lines. The balancing control can also be connected to an active rectifier via data and / or control channels in order to at least partially carry out balancing via this. According to one embodiment, it is proposed that the balancing control is prepared to sort all connection lines into a string sequence according to their power consumption, regardless of the respective AC charging terminal, the phase change devices each set or change the connection assignment so that all connection lines are alternately connected to the first, second and third supply lines of the three supply lines are connected, and then in particular the next three connection lines to the third, second and first supply line, wherein As a boundary condition it is checked that no two or three connection lines are connected to the same supply line for any AC charging terminal.

In this embodiment, no distinction is made between one, two and three-phase AC terminals. All connection lines are sorted into a line sequence according to their power consumption. E.g. In the string sequence, a first connection branch of a first single-phase AC charging terminal could be at position 1, the third connection branch of a second three-phase AC charging terminal at position 2 and its second connection branch at position 5. At positions 3 and 4, for example, the first and a second connection line of a third two-phase AC charging terminal. Then the first connection line of the first AC charging terminal (place 1) would be connected to the first supply line, the third connection line of the second three-phase AC charging terminal (place 2) to the second supply line and the first connection line of the third two-phase AC charging terminal (place 3) to the third supply line. The next three connection lines would then be connected to the third, second and first supply line, i.e. first the second connection line of the third two-phase AC charging terminal (place 4) to the third supply line and the second connection line of the second three-phase AC charging terminal (place 5) to the second supply line, as well as a further connection line not mentioned in the above example (place 6) to the first supply line. In this case, however, two connection lines would be connected from the second three-phase AC charging terminal to the second supply line, and two connection lines would be connected from the third two-phase AC charging terminal to the third supply line.

That should not be the case and therefore it is checked as a boundary condition. In the present case, the assignment of the second connection line of the third two-phase AC charging terminal (place 4) to the third supply line would not be permitted, and instead would be connected to the next supply line, provided that the boundary conditions permit this. The second connection line of the second three-phase AC charging terminal (place 5) could then take over the place and be connected to the first supply line if the check of the boundary conditions permits.

According to one embodiment, it is proposed that the balancing control is prepared so that, in order to minimize the phase asymmetry, a connection assignment via an optimization calculation based on the power consumption of the connection connecting lines of all AC charging terminals is determined. This is suggested at least for AC charging terminals with single-phase or two-phase power consumption, namely if it can be particularly assumed that AC charging terminals with three-phase power consumption also have power consumption that is essentially equally distributed over all three phases. If, however, it should emerge that AC charging terminals with three-phase power consumption in relation to the three phases work unevenly, particularly unevenly, then AC charging terminals with three-phase power consumption can also be included in the optimization calculation.

An optimization calculation can be carried out, for example, in such a way that a vector with three elements is provided for each AC charging terminal, in which the current values of the three phases are. The optimization calculation can then, for example, successively swap the values of each vector, possibly except for the first, and each time form a sum of all vectors and check in which case the three elements of the resulting sum vector have the smallest deviations from one another. Another possibility is to calculate an ideal current value for all three phases of the power supply and to swap the elements in each of the individual vectors mentioned in order to achieve this ideal value. This ideal value can easily be calculated by adding up all current values of the three phases of all AC charging terminals and dividing them by three. Another possibility is to split the three connection strings of each AC charging terminal into positive and negative sequence components and then only consider the negative sequence components for optimization, especially so that the phase positions of the negative sequence currents are switched so that the sum of all Negative system components in the optimization calculation results in zero or at least becomes minimal.

For the optimization calculation, it is optionally proposed that the number of necessary switching processes of the phase change device be taken into account. It can be the case, for example, that an asymmetry of 40%, for example, can be reduced to 3% with a few switching processes, but a very high number of switchings is required to achieve a further reduction to 2%. In particular, a secondary condition that can be taken into account is to minimize the number of switchover processes. Using as few switching processes as possible can therefore be included as a secondary condition. According to one embodiment, it is proposed that at least one DC charging terminal with an upstream active rectifier is provided, the active rectifier is connected to the power supply and the active rectifier is prepared to load the three supply lines differently in order to avoid asymmetry of the currents in the power supply to reduce. The DC charging terminal is thus prepared to provide at least one direct current for charging an electric vehicle. For this purpose, the DC charging terminal, which can also be referred to as a direct current charging terminal, can have several DC sub-terminals, which can also be referred to as a DC charger or direct current charger. An electric vehicle can be connected here for charging without the electric vehicle itself having to have its own charging current control.

The active rectifier is therefore provided to generate a first direct current, which may be further processed in the sub-terminals, and this can not only adjust the direct current to the desired level, but it can also be controlled on the AC side and control its three-phase input current. also with regard to each individual phase. Such an active rectifier can also be constructed like an inverter, whereas it is operated in the opposite direction, namely from alternating current to direct current. In fact, it is also possible here for such a rectifier / inverter to be operated bidirectionally. In that case, the DC charging terminal could also feed electrical power into the power supply, which is proposed as a preferred embodiment.

This active rectifier can thus control the load on the three supply lines and the active rectifier is preferably controlled in such a way that it generates a negative sequence current with any phase and amplitude, if possible, and thus connects to the three-phase power supply, thereby creating an asymmetry of the currents in the power supply to reduce.

The generation of such a negative sequence current refers to the method of symmetrical components, according to which a three-phase current is computationally broken down into a positive sequence or a positive sequence component and a negative sequence or negative sequence component, which can also be referred to as negative sequence current, by means of a transformation. In principle, a zero system or zero system current must also be taken into account, which can be neglected here. A zero-system current can indeed occur here, but it is assumed that there is essentially a de facto ohmic load from all of the electric vehicles to be charged thus a reduction in the asymmetry and thus a reduction in a negative sequence current component almost automatically leads to a reduction in the zero sequence current. It is therefore sufficient to consider the asymmetry. Nevertheless, it can preferably be provided that a zero sequence component is also taken into account and compensated for.

In any case, it is proposed to reduce the asymmetry to specify a negative sequence current and to draw it from the power supply together with a positive sequence current required for charging the electric vehicles connected to the DC charging terminal. From the calculated negative sequence current and the required positive sequence current, the actual three currents of the three phases can be calculated and the active rectifier can be controlled so that it draws these three currents from the power supply. The active rectifier then switches the negative sequence current to the three-phase power supply. It is preferably provided that the balancing control is prepared to control the active rectifier to reduce the asymmetry of the currents. This can mean in particular that, on the one hand, the balancing control receives sensor data via the three-phase power supply, possibly including information about a current of a neutral conductor of the power supply. It is also proposed that the balancing control has a data connection, in particular a data line, with which the active rectifier can be controlled. At least one setpoint value for a negative sequence current to be switched from the active rectifier to the three-phase power supply, which the balancing control has previously calculated, is preferably transmitted via this. It is particularly advantageous here if the balancing control can control both this active rectifier and the phase change devices. Incidentally, several DC charging terminals and several active rectifiers can of course also be provided.

According to one embodiment, the charging station is prepared so that changing the connection assignment is repeated after an asymmetry threshold value is exceeded, which is a measure of an asymmetry in the power supply, or is repeated in a recurring cycle, in particular the recurring cycle being repeated continuously after a repetition time , the repetition time is shorter than an average charging process of an electric vehicle. According to this, beaten to check the connection assignment during a charging process and to change it if necessary. It was particularly recognized here that the load on the three-phase power supply can also change during a charging process. It was particularly recognized that when charging electric vehicles, high charging currents often occur at the beginning, which are then gradually reduced. In addition, the load situation of the power supply can also constantly change because a vehicle leaves the charging station and / or a vehicle is newly connected to the charging station.

The repetition time is selected in a range from 1 minute to 5 minutes. This is well below the duration of an average charging process for an electric vehicle, which can range from 15 minutes to several hours. It is therefore proposed that the connection assignment be checked and, if necessary, changed more often.

The power supply is preferably continuously monitored; in particular, the currents of the three supply lines are continuously monitored, while the asymmetry is also monitored. If this becomes too large, symmetrization is repeated. This can be done by specifying an asymmetry threshold.

The power supply is preferably connected to a network connection point of an electrical supply network, in particular via a transformer. It can thus be achieved that balancing the three phases of the power supply also has a correspondingly positive effect on the electrical supply network. As a result, the power quality in the network can be improved by means of the charging station, at least in comparison to the situation when no attention is paid to reducing the asymmetry of the three-phase power supply in the charging station. According to the invention, a method for charging electric vehicles by means of a charging station is also proposed. This method is based on a charging station that has several AC charging terminals, each of which is designed to charge an electric vehicle with alternating current. According to the method, each of the AC charging terminals is supplied with electrical three-phase current via a phase change device which is connected to a three-phase power supply of the charging station. This can also mean that the corresponding three phases are present at an input of the AC charging terminal, but are only partially called up. Of course, electricity only flows when an electric vehicle is connected. The power supply, which has three supply lines, then provides three voltage phases. Each of the three supply lines thus has one of the three voltage phases.

In addition, each AC charging terminal has three connection lines, each of which is connected to the three supply lines, and the three voltage phases are applied to the connection lines via the three supply lines. Each phase change device then changes a connection assignment between the three supply lines and the three connection lines in order to reduce a current asymmetry in the power supply. If a current asymmetry has become minimal, in particular zero, then of course the connection assignment does not need to be changed. But whenever a reduction in the current asymmetry is to be carried out, this phase change device can change the connection assignment. This is done individually for each AC charging terminal.

It is preferably proposed that the method use a charging station as explained in accordance with an embodiment described above. In particular, it is proposed that the method or a part thereof be implemented in the balancing control of the charging station.

The invention is explained in more detail below by way of example using embodiments with reference to the accompanying figures. Figure 1 shows a charging station in a schematic representation.

FIG. 2 shows a flow chart for a method for charging electric vehicles.

In FIG. 1, a charging station 1 is shown schematically, which is connected to an electrical supply network 4 via a network connection point 2. The charging station 1 has several AC charging terminals 6 and a DC charging terminal 8 with two sub-charging terminals, namely with two DC chargers 10.

To supply the AC charging terminals 6 and the DC charging terminal 8, a power supply 12 is provided, which has a first, second and third supply line 21, 22 and 23 and a supply neutral conductor 20. The power supply 12 is connected to the network connection point 2 and there to a transformer 14 provided at the network connection point 2. The DC charging terminal 8 is connected to the three strings 21, 22 and 23 of the power supply 12 via an active rectifier 16. A connection to the supply neutral conductor 20 is not provided for the active rectifier, but can be provided according to one embodiment. Each AC charging terminal 6 is connected to the power supply 12 via a phase change device 18. The connection is made to the three supply lines 21, 22 and 23 as well as to the supply neutral conductor.

Each AC charging terminal 6 is connected to the first, second and third supply lines 21, 22 and 23 via a first, second and third connection line 31, 32 and 33. For the sake of clarity, the reference symbols are only drawn in for one AC charging terminal 6, but apply equally to the other AC charging terminals 6, which have the identical structure and identical connection in FIG. 1. Each AC charging terminal 6 is also connected to the supply neutral 20 via a neutral conductor connection 30. Each AC charging terminal 6 also has a three-phase output connection 26 to which the respective electric vehicle 24 to be charged can be connected.

The three-phase output connection 26 can be changed in its connection assignment to the three connection branches 31, 32 and 33 by the phase change device 18. FIG. 1 shows the same setting for each of the four phase change devices 18 shown. The phase change device 18 is shown as a coupled triple switch, which can thus change the connection assignment for all three phases at the same time and, in the electrical engineering sense, a phase change by 120 for the three-phase system ° or 240 °. This is indicated in FIG. 1 by the fact that in addition to the symbols above the power supply 12 to each AC charging terminal 6, 0 °, 120 ° or 240 ° is written. In this respect, the phase change devices 18 shown can also be referred to as phase rotation devices or respectively as phase rotation switches. However, other types of implementation for changing the connection assignment are also possible.

Incidentally, the connection neutral conductor 30 is only looped through the phase change device 18 and is not affected by switching processes.

Four AC charging terminals 6 are shown by way of example in FIG. 1, but additional ones can be provided and the power supply 12 also indicates that they are still can be continued. Two of the four AC charging terminals 6 each have an electric vehicle connected with a single-phase in-vehicle charger, with the first phase being specifically only loaded, which is indicated by Ph1. An electric vehicle 24 is connected to another AC charging terminal, which also uses an in-vehicle charger which is single-phase, but is connected to a third phase, which is indicated by Ph3. An in-vehicle charger is also referred to in specialist circles as an onboard charger, which can therefore be used as a synonymous term. Finally, a fourth electric vehicle 24 is provided which uses a three-phase in-vehicle charger. For the situation of the four AC charging terminals 6 shown as an example in FIG. 1, the situation is that the first phase is loaded by two single-phase in-vehicle chargers, the second phase by none and the third phase by a single-phase in-vehicle charger. In addition, all three phases are ideally evenly loaded by the three-phase in-vehicle charger. Accordingly, the first phase is likely to be heavily overloaded and the second phase is likely to be heavily underloaded, so that overall there is a very asymmetrical load on the power supply 12.

In this illustrated example, this could easily be remedied in that for one of the two AC charging terminals that are loaded on the first phase, the phase changing device 18 carries out a phase changeover or phase advancement so that the first phase that the single-phase in-vehicle charger uses the second connection line is switched, which then results in an interconnection with the second supply line. As a result, a single-phase vehicle-internal charger would then be connected to the first, second and third supply line.

A balancing control 28 is provided for operating the charging station and in particular for controlling the phase change devices 18 in order to reduce or, if possible, minimize an asymmetrical load on the three-phase power supply. This balancing control 28 receives information about all currents or connecting lines or connecting lines of the AC charging terminals 6. A terminal sensor 34 is provided for each. The terminal sensor 34 thus supplies information about each current between each AC charging terminal and the power supply 12. For this purpose, each AC charging terminal 6 can be connected to each of the four currents, that is to say the three phase currents and the neutral conductor current, four current values are transmitted to the balancing control 28.

However, it is also possible that the respective terminal sensor 34 or an evaluation unit coupled to it already converts these four currents using the symmetrical component method, namely into a positive sequence current li, n, a negative sequence current h, n and a zero sequence current lo, n. These currents can be transmitted to the balancing control 28 via a terminal sensor line 36 and this is indicated in FIG. 1 on the terminal sensor line 36. The index n for each of these partial currents indicates that such three currents are recorded for each of the AC charging terminals 6. The index n therefore stands for the respective number of the AC charging terminal. In the present illustrative case of FIG. 1, the index n would thus range from 1 to 4.

The balancing control 28 can now determine an optimization based on these current values that it has received via the terminal sensor line 36 and then control the phase change devices 18 accordingly in order to make the connection assignments between the respective output connection 26 and the connection strings 31, 32 and 33 of the AC charging terminal 6 to be implemented by switching the phase change devices 18 accordingly. For this purpose, corresponding control signals can be transmitted from the balancing control 28 to the phase change devices 18 and for this purpose, for example, a terminal control line 38 can be provided to each phase change device 18.

FIG. 1 additionally illustrates the use of the active rectifier 16 to further reduce any asymmetry of the currents in the power supply 12. To this end, it is first proposed that the balancing control 28 receive corresponding current data from the power supply 12. A power supply sensor 40 is provided for this, which can detect all four currents of the power supply 12. He or an assigned evaluation unit can also provide a transformation using the symmetrical component method and accordingly determine a positive sequence current li, a negative sequence current I2 and a zero sequence current Io and feed it to the symmetry control 28 via a feed sensor line 42. From this, naturally taking into account the recorded currents of the AC charging terminals 6, the balancing controller 28 can generate a predefined negative sequence current component I2 soii as a setpoint value and feed it to the active rectifier 16 via a rectifier control line 44. Together with the power requirement of the DC charging terminal 8 and the setpoint value for the negative sequence current I2 soii, the active rectifier 16 can then be controlled in such a way that, after reverse transformation from the representation according to the symmetrical components, a corresponding three-phase current is drawn from the power supply 12. The active rectifier 16 and thus the DC charging terminal 8 are then supplied from the power supply 12, that is to say draws current, but at the same time switches on the negative sequence current that has been specified by the balancing control 28. A further equalization of the currents in the power supply 12 can thus be achieved. FIG. 2 shows a flow diagram 200 for minimizing the asymmetry in a power supply line 12 of FIG. 1. First, in a step 0, which is indicated in FIG. 2 as SO, a static phase symmetrization is carried out. This is indicated by the static balancing block 202. Accordingly, the phase change device for all AC charging terminals that are not used at the moment is successively shifted from one to the next AC charging terminal by one phase in order to achieve a leveling out. For the example in FIG. 1, assuming that none of the four AC charging terminals 6 shown is being used at the moment, that according to the illustration in FIG. 1, coming from the left, the first phase change device 18 remains as it is The next phase change device 18 is switched one switch position further to the right, the third is switched two positions further to the right and the fourth remains as it is. If there were a fifth, it would be indexed one position, the sixth by two, and so on.

This creates a good basis so that an approximately even distribution of the phases can be achieved as a starting condition, at least when connecting single-phase in-vehicle chargers. If vehicles are already connected to AC charging terminals for charging, the proposed static phase balancing is only proposed for the AC charging terminals that have not been used until then. As soon as vehicles are connected, there is initially a very good symmetry as a start condition. These connected vehicles or the corresponding AC charging terminals can then be included in a further minimization of the asymmetry, as is carried out in the following steps.

Correspondingly, in order to specifically minimize the asymmetry, the next step proposed is step 1, which is identified as S1 in FIG. 2 and comprises several blocks. Initially, a sorting of the AC- Charging terminals made according to the size of the maximum phase current of this AC charging terminal. Different variants can be considered. One variant is that only those AC charging terminals are taken into account in this sorting that have a single-phase or two-phase power consumption at the moment. According to the embodiment according to FIG. 1, this can also be recognized by the terminal sensor 34.

Another variant is that the AC charging terminals are sorted in groups according to the size of the maximum phase currents. Accordingly, a first group can include all AC charging terminals that show a single-phase current load, and a second group can include all AC charging terminals that show a two-phase current load. If necessary, the AC charging terminals that show a three-phase current load can also be sorted into a third group.

With this sorting, be it in groups or otherwise, the minimization of the asymmetry in the variation block 206 is continued. In the variation block 206, the connection branches with the maximum phase currents are then successively switched to the first, second and third phases in the sequence that resulted from the sorting block 204. This should be understood in such a way that for the AC charging terminal with the largest maximum phase current this is switched to the first phase, for the AC charging terminal with the second largest maximum current it is switched to the second phase and for the AC charging terminal with it the third largest maximum phase current this is switched to the third phase.

In the case of the AC charging terminal with the fourth largest maximum phase current, however, it does not start from the beginning, but rather back in the same order. The AC charging terminal with the fourth largest maximum phase current is also switched to the third phase, the fifth largest maximum phase current is switched to the second phase and the sixth largest maximum phase current to the first.

All of this, especially the process in the sorting block 204 and in the variation block 206, is proposed for AC charging terminals such as the AC charging terminals 6 and implemented accordingly with the phase change devices such as the phase change devices 18 of FIG.

In step 2, which is identified as S2 in Figure 2, a further minimization of the asymmetry is proposed, which ideally leads to the currents in the current supply Lead, as the power supply 12 of Figure 1, are completely symmetrical, the asymmetry is at least very greatly minimized, in particular close to zero.

One or more active rectifiers, such as the active rectifier 16 of the embodiment of FIG. 1, are now used for this purpose. For this purpose, the total asymmetry remaining in spite of the measures according to variation block 206 is recorded in residual asymmetry determination block 208. With particular reference to the embodiment in FIG. 1, this can be achieved by the power supply sensor 40, which transmits its detected result to the balancing control 28. A negative sequence current required for compensation can then be determined from this. This can be carried out in the opposing system determination block 210. The result would be a negative sequence current, such as the negative sequence current h soii in FIG. 1, which is given to the active rectifier 16 as a setpoint value. Correspondingly, this conversion takes place in the rectifier control block 212, which converts this specification of the negative sequence current and thus actually switches the negative sequence current to the power supply 12, that is to the three currents present there or the three-phase current system present there.

In the ideal case, a symmetrical three-phase power system can be achieved in the power supply 12.

It should be noted here that charging processes for electric vehicles usually do not take a long-term, stationary and unchanged course, but rather that the charging flow in particular drops over time. Particularly at the beginning of a charging process, the initial charging current can drop considerably, for example from 100% to 30% or even less. At least the charging process can slow down towards the end when the state of charge is 80%. With this change, the asymmetry can also change. In particular, it can increase or occur again after the minimization of the asymmetry according to the sequence of FIG. 2 has been successful. It is therefore proposed to repeat step 2, that is to say the implementation in the residual asymmetry determination block 208, the negative sequence determination block 210 and the rectifier control block 212, frequently. Activation of certain loads such as devices for cooling, heating, predictive air conditioning during or at the end of the charging process can also influence the power consumption.

This is indicated in FIG. 2 by a return in the area of step S2. This repetition can be repeated at a first repetition time Ti. This first repetition time Ti can be selected to be very small, for example in the region of 1 min or it can be chosen to be 10 seconds or less. In fact, all of these explanations in blocks 208, 210 and 212 can be implemented in a computerized manner and can therefore be quickly repeated. It is therefore even possible that the executions of blocks 208, 210 and 212 are repeated essentially continuously or quasi continuously, namely according to a computer clock rate.

However, it was also recognized that this final minimization of the asymmetry by means of the controlled rectifier can only compensate for a residual asymmetry. It is therefore proposed that the reduction of the asymmetry according to the implementation of the sorting block 204 and the variation block 206 be repeated regularly, namely according to a second repetition time T2. This second repetition time can be 1 minute or more, for example. It is also possible that it is several minutes and is, for example, 3 minutes or more. It should preferably be chosen to be less than 10 minutes.

In this way it can then be achieved that basically rough or strong unequal loads, as can be expected from many single-phase or two-phase chargers inside the vehicle, are initially reduced or evened out via the phase change devices, such as the phase change devices 18, and only a remaining one Residual asymmetry is further reduced or even eliminated by the active rectifier. Two specific examples of possible asymmetries with the various proposed solutions are given below.

It should be noted that the two examples in the "Symmetrical Components" tables are based on a representation and consideration using the symmetrical component method. Here h denotes the positive sequence current, I2 the negative sequence current and Io the zero sequence current. The asymmetry lasy is calculated using the following formula: 100

The current values of both examples are normalized to a reference value.

Example 1: Charging process with 1 pu DC (symmetrical AC load) and 0.33 pu AC on phase A (total current): Symmetrical

Phase values

Components

This results in the asymmetry:

I2 + J 0

Yes sy = 50%

k

Feeding in an additional negative sequence current through the DC charger:

Symmetrical

Phase values

Components

Total current after compensation of the negative sequence:

Symmetrical

Phase values

Components

This results in the asymmetry:

In example 1 there is thus an asymmetry of 50% due to the feeding in of a negative sequence current, e.g. has been reduced to 25% by the active rectifier 16 of the embodiment of FIG.

Example 2: charging process with 1 p.u. DC (symmetrical AC load) and 4X0.33 p.u. AC on phase A (total current):

Symmetrical

Phase values

Components

This results in the asymmetry: 114%

Phase rotation of AC charging point four by 240 ° and AC charging point 3 by 120 °:

Symmetrical

Phase values

Components

This results in the asymmetry:

Total current after compensation of the negative sequence: Symmetrical

Phase values

Components

This results in the asymmetry:

I2 + J 0

Yes sy = 14%

k

In the second example, there was initially an even greater overall asymmetry, namely of 1 14%. In a first step, which could correspond to step S1 in FIG. 2, it was reduced to 28% by changing some phase assignments. For this purpose, a phase rotation of 240 ° was carried out on a fourth AC charging terminal, which could correspond to the AC charging terminal 6 shown on the far right in FIG. The connection lines were thus switched on by two counters, in relation to FIG. 1 that is the first connection line 31 to the third supply line 23, and 32 to 21 and 33 to 22.

In addition, a phase rotation of 120 ° was carried out at a third AC charging terminal, which could correspond to the penultimate AC charging terminal 6 shown on the right in FIG. There the connection lines were therefore switched on by a counter, based on FIG. 1 that is the first connection line 31 to the second supply line 22, and 32 to 23 and 33 to 21.

In a second step, which can correspond to step S2 in FIG. 2, by feeding in a negative sequence current, e.g. by the active rectifier 16 of the embodiment of FIG. 1, the asymmetry can be further reduced to 14%.

Claims

Expectations

A charging station (1) for charging electric vehicles (24), comprising:

several AC charging terminals (6), each for charging an electric vehicle (24) using alternating current, wherein

- Each of the AC charging terminals (6) each via a phase change device

(18) is connected to a three-phase power supply (12) in order to be supplied with electrical three-phase current, the power supply (12) having three supply lines (21, 22, 23) for providing three voltage phases,

- Each AC charging terminal (6) has three connection lines (31, 32,33) for

Connection to the three supply lines (21, 22, 23) for applying the three voltage phases to the connection lines (31, 32, 33), each phase change device (18) being set up to assign a connection between the three supply lines (21, 22, 23) and the three connecting lines (31, 32, 33).

2. Charging station (1) according to claim 1, comprising:

a balancing control (28) for controlling the phase change devices (18), wherein

the balancing control (28) is prepared to control the phase change devices (18) in order to reduce, in particular to minimize, a phase asymmetry of the supply lines (21, 22, 23).

3. charging station (1) according to claim 1 or 2,

characterized in that

one or the balancing control (28) is prepared for

- To sort the AC charging terminals (6) according to their current consumption and / or

to sort the AC charging terminals (6) according to whether they work single-phase, two-phase or three-phase,

and to control the phase change devices (18) as a function thereof in order to minimize the phase asymmetry of the supply lines (21, 22, 23).

4. charging station (1) according to one of the preceding claims,

characterized in that the balancing control (28) is prepared to sort the AC charging terminals (6), in particular with single-phase or two-phase power consumption, according to their current consumption, or to sort the AC charging terminals (6) with single-phase power consumption into a first group which To sort AC charging terminals (6) with two-phase power consumption into a second group and optionally the AC charging terminals (6) with three-phase power consumption into a third group and sort them in groups according to their current consumption, with each of these AC charging terminals (6) the connection string with the greatest current consumption is identified as the string with the maximum load, and its current consumption is taken into account as the maximum phase current of the AC charging terminal (6),

the AC charging terminals (6) are sorted according to their maximum phase current in a current sequence, possibly in groups,

- The phase change devices (18) each set or change the connection assignment so that the maximum loaded strings are alternately connected to the first, second and third supply strings (21, 22, 23) of the three supply strings (21, 22, 23) according to the current sequence , and in the case of the AC charging terminals (6) with two-phase power consumption, preferably the second current-carrying line to the following one

Supply line, namely the second, third or first supply line (22,23,21) is connected, and possibly at the AC charging terminals (6) with three-phase power consumption in particular one of the remaining lines to the following supply line, namely the second, third or the first supply line (22,23,21) is connected,

whereby the connection allocation is carried out in such a way that according to the current sequence, if necessary in groups,

the first line with maximum load is connected to the first supply line,

- a second maximum loaded line is connected to the second supply line,

a third, maximally loaded line is connected to the third supply line,

a fourth, maximally loaded line is connected to the third supply line,

a fifth, maximally loaded line is connected to the second supply line, and a sixth maximally loaded line is connected to the first supply line.

5. charging station (1) according to one of the preceding claims,

characterized in that

- the balancing control (28) is prepared to sort all connection lines according to their power consumption in a string sequence, regardless of the respective AC charging terminal (6),

the phase change devices (18) each set or change the connection assignment so that all connection lines alternate according to their line sequence to the first, second and third supply line

(21, 22, 23) of the three supply lines (21, 22, 23) are connected, and then in particular the next three connection lines to the third, second and first supply line, wherein

As a boundary condition it is checked that no two or three connection lines are connected to the same supply line for any AC charging terminal.

6. charging station (1) according to one of the preceding claims,

characterized in that

the balancing control (28) is prepared so that, in order to minimize the phase asymmetry, a connection assignment is determined via an optimization calculation based on the power consumption of the connection strings (31, 32, 33) of all AC charging terminals (6), at least the AC charging terminals ( 6) with single-phase or two-phase power consumption, with optional

- A number of necessary switching processes of the phase change devices (18) is taken into account, in particular that minimizing the number of switching processes is taken into account as a secondary condition.

7. charging station (1) according to one of the preceding claims,

characterized in that

at least one DC charging terminal (8) with an upstream active rectifier (16) is provided,

the active rectifier (16) is connected to the power supply (12), and the active rectifier (16) is prepared to load the three supply lines (21, 22, 23) differently, in particular to switch a negative sequence current (I2) to the three-phase power supply in order to reduce asymmetry of the currents in the power supply (12), wherein in particular the balancing control (28) is prepared to control the active rectifier (16) to reduce the asymmetry of the currents.

8. charging station (1) according to one of the preceding claims,

characterized in that

- The charging station (1) is prepared to repeat the changing of the connection assignment after an asymmetry threshold value is exceeded, which is a measure of an asymmetry of the power supply, or is repeated in a recurring cycle, in particular

the recurring cycle is continuously run through after a repetition time (T2), which is selected to be shorter than an average charging process of an electric vehicle (24), wherein

the repetition time (T2) is selected in particular in a range from one minute to five minutes.

9. charging station (1) according to one of the preceding claims,

characterized in that

the power supply is connected to a network junction (2) of an electrical supply network, in particular via a transformer (14).

10. A method for charging electric vehicles (24) by means of a charging station (1) and the charging station (1) has several AC charging terminals (6), each of which is connected to

Charging of an electric vehicle (24) are formed by alternating current, each of the AC charging terminals (6) being supplied with electrical three-phase current via a phase change device (18) which is connected to a three-phase power supply (12) of the charging station (1), - three voltage phases are provided by the power supply (12), which has three supply lines (21, 22, 23),

each AC charging terminal (6) has three connection lines (31, 32, 33) which are each connected to the three supply lines (21, 22, 23), and via which the three voltage phases are applied to the connecting lines (31, 32, 33), with

each phase change device (18) changes a connection assignment between the three supply lines (21, 22, 23) and the three connection lines (31, 32, 33) to reduce a current asymmetry in the power supply (18).

1 1. Method according to claim 10,

characterized in that

it uses a charging station (1) according to one of claims 1 to 9.