Charging stations for electric vehicles

Abstract

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

Description

Technical Field

[0001] The invention relates to a charging station for charging an electric vehicle and the invention also relates to a method for charging an electric vehicle. Background Art

[0002] Electric vehicles are becoming more and more popular, which in turn requires more and larger charging stations, which charge electric vehicles. Large charging stations, which can also be referred to as electric filling stations, can charge a number of electric vehicles simultaneously with electric current. Such charging stations usually receive the power required for this from the power supply network, to which they can be connected via a grid connection point. In the case of large charging stations in particular, their power requirements can have a significant impact on the power supply network. In this case, grid sections or grid connection points can sometimes reach their power limits.

[0003] In order to solve this problem, the power supply network and / or the grid connection point are designed with regard to the power capacity or the ability to transmit power.

[0004] However, it is not only the power level that is problematic, but also the quality of the current, which can be affected by the charging station. Charging stations for charging electric vehicles convert the three-phase alternating current obtained from the power supply network into direct current. Different charging technologies are used in different types of electric vehicles. In addition to the DC fast charging option, almost all vehicles, at least a large number of vehicles, also use so-called in-vehicle chargers. The in-vehicle charger itself converts the alternating current into direct current, i.e. has an AC input and can therefore also be synonymously referred to as an AC charger. Such an in-vehicle charger is connected to the AC terminal in a single-phase, two-phase or three-phase manner. In this case, the electric vehicle is therefore supplied with a one-phase, two-phase or three-phase alternating current and is then converted to a direct current, i.e. to a DC charging current, in the electric vehicle.

[0005] In particular, which phases of the three-phase supply line that is directly or indirectly connected to the power supply network at the grid connection point are loaded is usually random. As a result, a strong asymmetry of the AC current system can occur when there are multiple vehicles to be charged. If, for example, three electric vehicles are charged via their internal vehicle chargers, which each work only in a single phase, using a greatly simplified example, the load on the three-phase system in the charging station is uniform when each internal vehicle charger draws its current from another of the three phases. But if, for example, all three vehicles draw their current from the same phase, for example the first phase, with their internal vehicle chargers at random, then the first phase is heavily loaded while the second and third phases are not loaded or are less loaded. Correspondingly, an asymmetrical load is obtained, which can affect the power supply network from the charging station.

[0006] In order to solve the problem, it can be attempted that at each AC charging point, i.e. at the AC charging point at which the electric vehicle is to be connected to the internal charger of the vehicle, one of the three phases is preset as a priority phase, wherein the priority phase changes from one AC charging point to the next. However, this does not take into account that the internal charger of the vehicle requires different amounts of current depending on the vehicle and the charging state. Therefore, if, for example, two AC charging points are provided for the first phase, two AC charging points are provided for the second phase, and two AC charging points are provided for the third phase, then an asymmetry will still occur if, for example, two vehicles only require a small charging current at the two AC charging points for the first phase, while, on the other hand, two vehicles requiring a high charging current are connected to the other two AC charging points for the second phase. The same applies if, for example, electric vehicles are connected and charged at the six AC charging points proposed by way of example only at the two AC charging points for the first phase.

[0007] In addition, in addition to single-phase in-vehicle chargers, there are also two-phase and three-phase in-vehicle chargers.

[0008] It can also happen, for example in so-called fleet use, in which a transport or logistics company has a number of electric vehicles and operates its own charging station, that a number of AC charging points are combined with a small number of fast charging points. The reason for this is that in this case the vehicles of the fleet are usually charged in a continuous overnight charging, for which a large number of AC charging points are required. In addition to this, however, a small number of fast charging points can be provided if one vehicle of the fleet temporarily has to be charged and this charging cannot wait until the night. Such fast charging points are fast charging points that have a DC chopper in order to provide a DC charging current in order to generate a high direct current for fast charging. Such a DC chopper as part of the fast charging point is then part of the charging station and can be connected in three-phase to a corresponding three-phase supply line in the charging station. It is therefore additionally conceivable that some charging stations have such a combination of DC chargers and AC charging points.

[0009] This design can additionally influence the symmetry of the three-phase supply system in the charging station and thus of the power supply grid to which the charging station is connected.

[0010] The German Patent and Trademark Office has searched the following prior arts in the priority application of the present application: DE 10 2013204 256 A1, DE 10 2017 116 886 A1, EP 3 184 352 A1, EP 3 549 814 A1, WO 2012 / 128626 A2. Summary of the invention

[0011] The invention is therefore based on the object of solving at least one of the problems posed. In particular, a solution should be proposed by which a charging station achieves a loading of the three-phase supply port that is as symmetrical as possible. At least an alternative solution to the solutions known to date should be proposed.

[0012] The present invention is therefore based on a charging station with a plurality of AC charging terminals for charging electric vehicles. Each AC charging terminal is respectively provided for charging an electric vehicle by means of an alternating current. Furthermore, each AC charging terminal is respectively connected to a three-phase current supply device via a phase conversion device in order to be supplied with a three-phase current. The current supply device therefore has three supply lines for providing three voltage phases. Each of the three supply lines therefore has one voltage phase in operation. For this purpose, for example, a three-core cable or a corresponding busbar system with at least three busbars can be provided.

[0013] Each AC charging terminal, which can also be synonymously referred to as an alternating voltage charging terminal, has three connecting lines for connecting to three supply lines of the power supply device in order to apply the three voltage phases of the three supply lines to the three connecting lines. Thus, each supply line is electrically connected to a connecting line. Thus, each AC charging terminal is connected to the power supply device in the manner described.

[0014] Each phase change device is designed to change the connection assignments between three supply lines and three connecting lines. For example, at the AC charging terminal, the first connecting line can be connected to the first supply line, and the second connecting line can be connected to the second supply line, and finally the third connecting line can be connected to the third supply line. The phase change device is capable of changing the assignments, for example, for the example mentioned to the following assignments, wherein after the change, the first connecting line is electrically connected to the second supply line, the second connecting line is electrically connected to the third supply line, and the third connecting line is electrically connected to the first supply line. However, another change can be made, after which, in order to remain in the last-mentioned example, the first connecting line is electrically connected to the third supply line, the second connecting line is electrically connected to the first supply line, and the third connecting line is electrically connected to the second supply line.

[0015] The two exemplary changes in the line assignments and thus the phase assignments can also be understood as rotations of the assignments, and to this extent the phase change devices can also each be designed as phase rotation devices. In theory, however, other changes in the assignments between connecting lines and supply lines are also conceivable, for example, to refer back to the above example, the first connecting line is then connected to the first supply line, the second connecting line is however connected to the third supply line, and the third connecting line is connected to the second supply line.

[0016] The change is used to change the load of the three phases. The last-mentioned change is in principle superfluous if each AC terminal only accesses one phase or accesses two or three phases in the same way, i.e. draws the same amount of current, and only the last two phases are exchanged. This is achieved if the phase change device can only move the port for all three lines forward or backward by one step or move it forward or backward by two steps for all three lines.

[0017] The phase change device can be designed mechanically in principle, wherein even a rotating or sliding switch always changes the current interconnection for the three phases, that is, for each of the three lines mentioned. However, it is also conceivable to implement this with power semiconductor switches, for example with IGBTs or thyristors. The use of semiconductor power switches has the advantage that the electronic control of the phase change device can be implemented better and no wear occurs on the switch contacts.

[0018] The use of a phase changer device makes it possible to connect the connecting lines to the supply lines in such a way that all three phases are loaded as equally as possible, because all AC charging terminals, at least all observed AC charging terminals having such a phase changer device, can achieve a loading of the three phases as evenly as possible for the entirety of the AC charging terminals.

[0019] A preferred embodiment, which can also be well combined with the remaining embodiments, is that a static phase-symmetric approach is already proposed. It is proposed for this purpose that all phase change devices of the AC charging terminals that are not used at the moment are switched uniformly between 0°, 120° and 240°. This applies in particular to the case where the phase change devices are designed as phase rotation devices, but the same results can be achieved with other phase change devices. Thus, the AC charging terminals that are not used at the moment are set or switched so that the first phase of the current supply device, which is here referred to as 0°, is connected to the first connecting line, and correspondingly the second phase is connected to the second connecting line and the third phase is connected to the third connecting line.

[0020] In another unused AC charging terminal, the first connecting line is connected to the second phase of the current conveying device, i.e. the second supply line, and correspondingly the second connecting line is connected to the third phase and the third connecting line is connected to the first phase. In a further unused AC charging terminal at this moment, the first connecting line is connected to the third phase, i.e. 240°, the second connecting line is correspondingly connected to the first phase and the third connecting line is connected to the second phase.

[0021] The following considerations are based here on the fact that in particular a single-phase in-vehicle charger is configured via its connection plug in such a way that it always uses the same connection pin as the active connection pin in the connection plug and thus always obtains its current from the same connection line, i.e., for example, always from the first connection line. By means of the proposed static phase symmetry, it is now achieved that the first connection line is, however, always connected to different supply lines. The one-sided load caused by the described structure of the connection line is therefore distributed as evenly as possible to the three supply lines by the phase conversion device and thus already makes it possible to take the first major step towards symmetrical loading. It is also considered that the static phase symmetry of the phase conversion device for presetting unused AC charging points is carried out in the no-current state and thus causes a small load or a small wear on the components involved, in particular the phase conversion device.

[0022] Preferably, a symmetric control device is provided for controlling the phase change device, wherein the symmetric control device is configured to control the phase change device in order to reduce, in particular minimize, the phase asymmetry of the supply line. Ideally, a phase symmetry of the supply line, i.e. the three phases, is achieved. Whether the phase symmetry is actually achieved depends in particular on how many AC charging terminals the charging station has and on how precise this phase symmetry is actually based.

[0023] In particular, the symmetry control device is designed such that it also quantitatively detects the asymmetry of the three phases of the power supply device and can individually control the phase change devices in order to find and implement suitable settings for each phase change device.

[0024] Additionally or alternatively, the symmetry control device can also quantitatively detect the individual phase loads of each AC charging terminal and, in this context, find a suitable connection assignment for each AC charging terminal individually which results in a load that is as symmetrical as possible for all AC charging terminals of the charging station as a whole.

[0025] Preferably, the symmetry control device has both of these pieces of information, namely not only information about the individual loads of the individual AC charging terminals, but also about the total load or phase distribution of the power supply device. This is based in particular on the idea that an asymmetry of the three phases of the power supply device is not only attributable to the AC charging terminals, but can also be related to further connected loads. In this case, the information about the load of each AC charging terminal therefore does not allow conclusions to be drawn about the total load situation of the three phases of the power supply device. For example, at least one active three-phase rectifier can be connected to the charging station, which can also cause an asymmetrical load on the three phases of the power supply device.

[0026] According to one embodiment, it is proposed that the symmetry control device is configured to sort the AC charging terminals according to their instantaneous current drop and control the phase change device in dependence thereon to minimize the phase asymmetry of the supply line. In this way, it is possible to avoid complex optimization programs, which can also or alternatively be performed in the symmetry control device, as is also proposed according to one embodiment.

[0027] In particular, the AC charging terminal with the largest instantaneous current drop is therefore considered first and set in order to minimize the asymmetrical load. The AC charging terminal with the largest current load therefore also has the greatest influence on the asymmetrical load. Other AC charging terminals with smaller current drops can then be set, for example, subsequently. Even if this does not allow for an optimal setting of all phase change devices of the AC charging terminals, this still allows for a relatively good result to be achieved with significantly less optimization effort.

[0028] In addition or alternatively, it is proposed that the AC charging terminals are sorted according to whether they are operated in single-phase, two-phase or three-phase mode. This is based on the idea that a change in the phase assignment has correspondingly other effects depending on whether they are operated in single-phase, two-phase or three-phase mode. This is measured in a first step by this sorting.

[0029] The symmetry control device may not be able to directly detect whether a so-called in-vehicle charger is connected in each case with one phase, two phase or three phase. However, the symmetry control device can in any case detect the current in each of the three connecting lines of the relevant AC charging terminal according to one embodiment and recognize which of the three connecting lines conducts current and which does not. This measurement then shows whether the corresponding AC charging terminal is operated with one phase, two phase or three phase.

[0030] If it is now recognized that the AC terminals are operated in three phases, this can be sorted out or sorted back in a meaningful way for consideration of the symmetrical control device. In addition, the sorting can provide that the AC charging terminals operated in single phase are sorted forward and the AC charging terminals operated in two phases are considered after this, that is, secondarily, in the sorting. It is at least meaningful to sort the AC charging terminals operated in single phase and the AC charging terminals operated in two phases into different groups. Therefore, it is also based on the idea that when all three phases are turned in the case of single phase, the phases are actually completely changed, that is, for example, from a full load of the first phase to a full load of the second phase.

[0031] When all three phases of the two-phase AC charging terminal are switched, however, only one of the two load phases is actually switched. For example, in this case, a switch is made from a uniform load of the first and second phases to a uniform load of the second and third phases. The load of the second phase is thereby not actually changed.

[0032] Particularly preferably, these two sortings are combined and first sorted according to the standard whether the AC charging terminal is operated in single-phase, two-phase or three-phase mode, and then sorted into the three existing groups or, after sorting out the three-phase group, into the remaining two groups, sorted according to the instantaneous current drop. For example, the single-phase charging terminal with the highest current can then be changed for a first equalization of the load, and then the AC charging terminal with the highest current, which is operated in two-phase mode, can be used for further equalization.

[0033] However, it is also conceivable to dispense with the sorting according to whether the AC charging terminal is operated with single phase, two phase or three phase if it turns out that a single-phase in-vehicle charger is provided and therefore only a single-phase in-vehicle charger and therefore only a single-phase AC charging terminal is actually considered. The inaccuracies caused by the presence of a two-phase in-vehicle charger can be tolerated if the control effort can be reduced as described.

[0034] According to one design solution, the symmetrical control device is configured to sort the AC charging terminals according to their instantaneous current drop, in particular using single-phase or two-phase current consumption, and it is performed so that for each of the AC charging terminals, the connecting line with the maximum current consumption is respectively identified as the line with the maximum load, and its current consumption is respectively considered as the maximum phase current of the AC charging terminal. On this basis, the AC charging terminals are then sorted in current order according to their maximum phase current. In addition, the symmetrical control device is configured to set or change the connection assignment for this phase conversion device respectively, so that the line with the maximum load is connected to the first, second and third supply lines of the three supply lines in a current order. Therefore, in the AC charging terminal with single-phase current consumption, the only line is also the line with the maximum load at the same time. The line is then connected to the first, second and third supply lines or electrically connected to them in a changing manner from one AC charging terminal to the next AC charging terminal.

[0035] In an AC terminal with a two-phase current consumption, there are therefore two current-carrying lines, and the lines can theoretically also be loaded with the same intensity. Then, one of the two lines can be selected arbitrarily, for example, the first of the two lines in each case. However, in practical implementation, it would be the case that two identical currents are never measured and thus one of the two lines would be identified as the most loaded line, the excess relative to the other line also still being small.

[0036] If the line with the highest load of each AC charging terminal with two-phase current consumption is now assigned to the first, second or third supply line, i.e. connected thereto or electrically connected thereto, it is proposed that the remaining second current-carrying lines are connected to the subsequent supply lines. For this purpose, based on the previously selected count of the first, second and third supply lines and correspondingly the second supply line follows the first supply line, the third supply line follows the second supply line, and the first supply line follows the third supply line. Accordingly, the second current-carrying lines are therefore connected to the second, third or first supply line or electrically connected thereto.

[0037] This allows a clear presetting and processing structure, according to which the line with the highest load and then the second line which subsequently carries the current, if any, are connected to the corresponding supply line. No complex optimization algorithms are required for this.

[0038] If an AC charging terminal (6) with a three-phase current consumption is also considered, it is particularly proposed that one of the remaining lines is connected to the subsequent supply line, namely the second, third or first supply line (22, 23, 21). For the remaining third line, only the still free supply line remains redundant.

[0039] An improvement or refinement can be achieved by first sorting the AC charging terminals into a first group and a second group, i.e. sorting the AC charging terminals with a single-phase current consumption into the first group, and the AC charging terminals with a two-phase current consumption into the second group, and optionally sorting the AC charging terminals (6) with a three-phase current consumption into the third group. The proposed order according to the above-mentioned distribution of the maximum phase currents and the connection to the relevant supply lines is then carried out group by group. This also means that in the first group, in principle, the line with the highest load in each case is the only line that carries the current.

[0040] According to a particular option, a subsequent connection sequence of the lines for the heaviest load is provided. This can be performed globally for all AC charging terminals with single-phase or two-phase or three-phase current consumption, or group by group, respectively for the first and second and possibly third group.

[0041] It is therefore proposed that the line with the first maximum load, i.e. the line with the maximum load of the first AC terminal according to the sorting, is connected to the first supply line, the line with the second maximum load is connected to the second supply line and the line with the third maximum load is connected to the third supply line. Here, the line with the first maximum load is the line with the maximum load of the first AC terminal according to the sorting, the line with the second maximum load is the line with the maximum load of the second AC terminal, and so on.

[0042] For the fourth to sixth, however, the reverse sequence is then proposed, so that the fourth most loaded line is also connected to the third supply line, the fifth most loaded line is connected to the second supply line, and the sixth most loaded line is connected to the first supply line. The first and sixth most loaded lines are then therefore connected to the first supply line.

[0043] By reversing the order of the fourth to sixth supply lines, it is avoided that the first supply line is loaded more heavily than the other two supply lines. The danger then arises when the first supply line is connected to the most heavily loaded line and the fourth most heavily loaded line. It is further provided that the principle also applies to the other lines, i.e. in particular the seventh to ninth most heavily loaded lines are connected to the first to third supply lines, and the tenth to twelfth most heavily loaded lines are connected in the reverse order to the third to first supply lines, and so on.

[0044] According to one embodiment, it is proposed that the sorting is generally carried out in the reverse progression, i.e. starting with the last most heavily loaded line and then continuing the progression with the second-to-last most heavily loaded line, or finally to the first most heavily loaded line. This makes it possible not to make excessive current changes in the first re-sorting step. If starting with the line carrying the greatest current, this would result in a temporary strong increase in the asymmetry in the most unfavorable case. However, if starting with the lowest current, the line with the greatest current is replaced by the first line when symmetry has already been partially achieved.

[0045] In particular, a sorting with a reverse order is proposed, so that it starts with the line with the last maximum load and is connected to the first supply line, the line with the second-to-last maximum load is connected to the second supply line, and the line with the third-to-last maximum load is connected to the third supply line. The order is then reversed again, so that the line with the fourth-to-last maximum load is also connected to the third supply line, the line with the fifth-to-last maximum load is connected to the second supply line, and the line with the sixth-to-last maximum load is connected to the first supply line. The symmetrical control device is particularly configured to perform all of the functions described so that it has a corresponding control program, which can be executed, for example, on a processing computer, which can form part of the symmetrical control device. In addition, a data channel, in particular a data line, is provided to connect the symmetrical control device to the AC charging terminal, in particular to be able to control a corresponding phase change device. For this purpose, sensor data of the current measuring device can also be transmitted to the symmetrical control device.

[0046] For such sensor data, corresponding current sensors can be arranged at the AC charging terminals, and this can also mean that such current sensors are arranged on the phase change device or the connecting line. It is also conceivable that each AC charging terminal has its own current sensor and the corresponding data are transmitted to the symmetry control device via a corresponding data channel, such as, for example, a data line. The symmetry control device can also be connected to the active rectifier via a data and / or control channel in order to at least partially implement the symmetry via it.

[0047] According to a design proposal,

[0048] - the symmetrical control device is configured to sort all the connecting lines into a line sequence according to their current consumption, independently of the corresponding AC charging terminal,

[0049] - The phase change device sets or changes the connection assignments respectively so that all connecting lines are connected alternately to the first, second and third supply lines of the three supply lines according to their line sequence, and then in particular the next three connecting lines are connected to the third, second and first supply lines, wherein - as a critical condition check, at any AC charging terminal, no two or three connecting lines are connected to the same supply line.

[0050] In this design, therefore, no distinction is initially made between single-phase, two-phase and three-phase AC terminals. All connecting lines are sorted into a line sequence according to their current consumption. For example, in the line sequence, the first connecting line of the first single-phase AC charging terminal can be in position 1, the third connecting line of the second three-phase AC charging terminal can be in position 2, and its second connecting line is in position 5. Then, in positions 3 and 4, for example, there can be the first and second connecting lines of the third two-phase AC charging terminal. The first connecting line of the first AC charging terminal (position 1) is then connected to the first supply line, the third connecting line of the second three-phase AC charging terminal (position 2) is connected to the second supply line, and the first connecting line of the third two-phase AC charging terminal (position 3) is connected to the third supply line.

[0051] The next three connecting lines are then connected to the third, second and first supply lines, i.e. firstly the second connecting line (position 4) of the third two-phase AC charging terminal is connected to the third supply line and the second connecting line (position 5) of the second three-phase AC charging terminal is connected to the second supply line, and a further connecting line (position 6) not mentioned in the above example is connected to the first supply line. In this case, however, from the second three-phase AC charging terminal, two connecting lines are connected to the second supply line, and from the third two-phase AC charging terminal, two connecting lines are connected to the third supply line.

[0052] This should not be the case and this is therefore checked as a boundary condition. In the present case, it would not be possible to assign the second connecting line (position 4) of the third two-phase AC charging terminal to the third supply line and instead connect it to the next supply line, if the boundary conditions permit this. The second connecting line (position 5) of the second three-phase AC charging terminal can then take up this position and be connected to the first supply line if the check of the boundary conditions permits this.

[0053] According to one embodiment, it is proposed that the symmetry control device is configured to determine the connection assignment based on the current consumption of the connecting lines of all AC charging terminals via an optimization calculation in order to minimize the phase asymmetry. This is proposed at least for AC charging terminals with a single-phase or two-phase current consumption in the following case, that in particular, it is possible to assume that AC charging terminals with a three-phase current consumption also have a current consumption that is essentially distributed equally to all three phases. However, if it is shown that the AC charging terminals with a three-phase current consumption operate unevenly, in particular strongly unevenly, with respect to the three phases, it can be proposed that the AC charging terminals with a three-phase current consumption are also taken into account in the optimization calculation.

[0054] The optimization calculation can be carried out, for example, so that a vector with three elements is predefined for each AC charging terminal, in which the current values ​​of the three phases are present. The optimization calculation can then, for example, gradually replace the values ​​of each vector, possibly up to the first vector, and each time form the sum of all vectors and check in which case the three elements of the sum vector formed have the smallest deviation from one another.

[0055] Another possibility is to calculate ideal current values ​​for all three phases of the current supply device and to replace the elements in each of the various vectors mentioned in order to reach the ideal value. The ideal value can be easily calculated by adding up all current values ​​of the three phases of all AC charging terminals and dividing by three.

[0056] Another possibility is to decompose the three connecting lines of each AC charging terminal into positive phase-sequence system components and negative phase-sequence system components and then only consider the negative phase-sequence system components for optimization, in particular by shifting the phase of the negative phase-sequence system current so that the sum of all negative phase-sequence system components is zero or at least minimized in the optimization calculation.

[0057] Optionally, it is proposed for the optimization calculation to take into account the number of switching processes required for the phase change device. For example, it is possible that an asymmetry of, for example, 40% can be reduced to 3% with a small number of switching processes, but a very high number of switching is required in order to further reduce it to 2%. In particular, it is possible as an additional condition to minimize the number of switching processes. Therefore, it is considered as an additional condition that as few switching processes as possible should be used.

[0058] According to one embodiment, at least one DC charging terminal is provided with an active rectifier connected upstream, the active rectifier is connected to the current supply device, and the active rectifier is configured to load the three supply lines differently in order to reduce the asymmetry of the current in the current supply device. The DC charging terminal is thus configured to provide a direct current for charging the electric vehicle. For this purpose, the DC charging terminal, which can also be referred to as a DC charging terminal, can have a plurality of DC sub-terminals, which can also be referred to as a DC charger or a DC charger. Here, the electric motors are connected for charging respectively, and the electric vehicle itself does not have to have its own charging current control device.

[0059] In order to generate a first direct current which may also be further pre-processed in the sub-terminals, an active rectifier is therefore provided and can not only track the direct current of the desired level, but can also be controlled on the AC side and in this respect control its input current of the three phases, more precisely also with respect to each individual phase. Such an active rectifier can also be designed like an inverter for this purpose, but it is operated in the opposite direction, that is, from alternating current to direct current. In fact, it is also possible here for such a rectifier / inverter to be operated bidirectionally. In this case, the DC charging terminal can also feed electrical power to the power supply device, which is proposed as a preferred embodiment.

[0060] The loads of the three supply lines can thus be controlled by the active rectifier and the active rectifier is preferably controlled in such a way that it generates a negative phase-sequence system current with as much phase and amplitude as possible for connection to the three-phase power supply device in order to thereby reduce the asymmetry of the current in the power supply device.

[0061] The generation of such a negative phase-sequence system current involves a symmetrical component method, in which the three-phase current is decomposed into a positive phase-sequence system or a positive phase-sequence system component and a negative phase-sequence system or a negative phase-sequence system component in a calculation manner by transformation, which can also be referred to as a negative phase-sequence system current. In principle, a zero system or a zero system current can also be considered, which can be ignored here. Although a zero system current may occur here, it is assumed that there is essentially an actual ohmic load through the electric vehicle to be charged, so that the reduction in asymmetry and the reduction in the negative phase-sequence system current component almost automatically cause a reduction in the zero system current. It is therefore sufficient to observe the asymmetry. Nevertheless, it can preferably be proposed that the zero system component is considered together and compensated together.

[0062] In any case, it is provided that a negative phase-sequence system current is provided in order to reduce the asymmetry and that the positive phase-sequence system current required for charging the electric vehicle connected to the DC charging terminal is taken from the power supply device.

[0063] From the calculated negative phase-sequence system current and the required positive phase-sequence system current, the three actual 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 device. The active rectifier thus connects the negative phase-sequence system current to the three-phase current supply device.

[0064] It is preferably proposed that the symmetry control device is configured to control the active rectifier to reduce the asymmetry of the current. This can particularly mean that, on the one hand, the symmetry control device obtains sensor data about the three-phase current supply device, possibly together with information about the current of the neutral line of the current supply device. It is also proposed that the symmetry control device has a data connection device, in particular a data line, by means of which the active rectifier can be controlled. Preferably, at least one expected value for a negative phase-sequence system current connected from the active rectifier to the three-phase current supply device is also transmitted, and the symmetry control device has calculated the negative phase-sequence system current in advance. It is particularly advantageous here that the symmetry control device can control the active rectifier and the phase conversion device. In addition, of course, multiple DC charging terminals and multiple active rectifiers can also be provided.

[0065] According to one embodiment, the charging station is configured to repeatedly change the connection assignment after exceeding an asymmetry threshold value, which is a measure of the asymmetry of the current supply device, or to repeat in repeated cycles, wherein in particular the repeated cycles are repeatedly passed continuously after a repetition time, wherein the repetition time is shorter than the average charging process of the electric vehicle. Therefore, it is then proposed that the connection assignment is also checked during the charging process and changed if necessary. In this regard, it has been recognized in particular that the load of the three-phase current supply device can also change during the charging process. In particular, it has been recognized that when charging an electric vehicle, a high charging current usually occurs at the beginning, which then gradually decreases. In addition, the load situation of the current supply device can also be continuously changed in the following way, that is, the vehicle leaves the charging station and / or the vehicle is reconnected to the charging station.

[0066] The repetition time is selected in particular in the range of 1 minute to 5 minutes. This is significantly shorter than the duration of an average charging process of an electric vehicle, which can be in the range of 15 minutes to several hours. It is therefore proposed to check the connection assignment significantly more frequently and change it if necessary.

[0067] Preferably, the current supply device, in particular the current of the three supply lines, is permanently monitored, and the asymmetry is also monitored. If the asymmetry is too great, the symmetrization is repeated. This can be done by presetting an asymmetry threshold value.

[0068] Preferably, the power supply device is connected to a grid connection point of the power supply network, in particular via a transformer. It can thus be achieved that the symmetry of the three phases of the power supply device also has a corresponding positive effect on the power supply network. The current quality in the grid can thus be improved by means of the charging station, in any case compared to the situation when no reduction in the asymmetry of the three-phase power supply device is observed in the charging station.

[0069] According to the present invention, a method for charging an electric vehicle with the aid of a charging station is also proposed. The method is based on a charging station having a plurality of AC charging terminals, each of which is configured to charge an electric vehicle with an alternating current. According to the method, each AC charging terminal is supplied with a three-phase current via a phase conversion device, which is connected to a three-phase current supply device of the charging station. This can also mean that the corresponding three phases are applied to the input of the AC charging terminal, but are only partially called up. Of course, current only flows when an electric vehicle is also connected.

[0070] By means of a current conveying device having three supply lines, three voltage phases are then provided. Each of the three supply lines therefore has one of the three voltage phases.

[0071] Furthermore, each AC charging terminal has three connecting lines, which are respectively connected to three supply lines and via which three voltage phases are applied to the connecting lines. Each phase changer therefore changes the connection assignments between the supply lines and the three connecting lines in order to reduce the current asymmetry in the current conveying device. As long as the current asymmetry is minimal, in particular zero, then of course there is no need to change the connection assignments. However, if a reduction in the current asymmetry is to be carried out, the phase changer can always change the connection assignments. This is therefore performed separately in each AC charging terminal accordingly.

[0072] It is preferably provided that the method uses a charging station as explained according to one of the above embodiments. It is particularly provided that the method or a part thereof is implemented in a symmetrical control device of the charging station. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The invention is explained in more detail below by way of example based on exemplary embodiments with reference to the accompanying drawings.

[0074] Figure 1 A schematic diagram showing a charging station.

[0075] Figure 2 A flow chart showing a method for charging an electric vehicle is shown. DETAILED DESCRIPTION

[0076] exist Figure 1Schematically shown is a charging station 1 which is connected to a power supply grid 4 via a grid connection point 2 . The charging station 1 has a plurality of AC charging terminals 6 and a DC charging terminal 8 with two sub-charging terminals, ie two DC chargers 10 .

[0077] To supply the AC charging terminal 6 and the DC charging terminal 8, a power supply device 12 is provided, which has a first, second and third supply line 21, 22 and 23 and a supply neutral line 20. The power supply device 12 is connected to the grid connection point 2 and there to a transformer 14 arranged at the grid connection point 2.

[0078] The DC charging terminal 8 is connected to the three lines 21, 22 and 23 of the current supply device 12 via an active rectifier 16. A connection to the supply neutral line 20 is not provided for an active rectifier, but can be provided according to one embodiment.

[0079] Each AC charging terminal 6 is connected to the power supply device 12 via a phase change device 18. The connection is made here not only at the three supply lines 21, 22 and 23 but also at the supply neutral line.

[0080] Each AC charging terminal 6 is connected to the first, second or third supply line 21, 22 and 23 via the first, second and third connection lines 31, 32 and 33. For a better overview, reference numerals are drawn only at one AC charging terminal 6, but the same applies to the remaining AC charging terminals 6, which have Figure 1 Each AC charging terminal 6 is also connected to the supply neutral line 20 via a neutral line port 30. Each AC charging terminal 6 also has a three-phase output port 26, to which the electric vehicle 24 to be charged can be connected.

[0081] The connection assignment of the three-phase output ports 26 to the three connecting lines 31 , 32 and 33 can be changed by the phase change device 18 . Figure 1 The same settings are shown for each of the four phase change devices 18 shown. The phase change devices 18 are shown here as coupled triple switches, which can thus change the connection assignments for all three phases simultaneously and thus electrically enable a phase rotation of 120° or 240° for a three-phase system. Figure 1 1 and 2, respectively, by writing 0°, 120° or 240° for each AC charging terminal 6 in addition to the symbol above the current supply device 12. In this context, the phase change device 18 shown can also be referred to as a phase rotation device or as a phase rotation switch. However, other types of implementations for changing the connection assignment are also conceivable.

[0082] Furthermore, the connecting neutral conductor 30 is respectively looped through only the phase change device 18 and is not involved in the switching process.

[0083] exist Figure 1 , four AC charging terminals 6 are shown by way of example, but further AC charging terminals can also be provided and the current supply device 12 also indicates that it can also be continued. Of the four charging terminals 6, at two charging terminals, an electric vehicle is connected to a single-phase in-vehicle charger, wherein specifically only the first phase is loaded here, as indicated by Ph1. An electric vehicle 24 is connected to the other AC charging terminal, which also uses an in-vehicle charger, which is single-phase in design but connected to the third phase, which is indicated by Ph3. In-vehicle chargers are also referred to in the art as on-board chargers, which can therefore be used as synonymous terms. Finally, a fourth electric vehicle 24 is provided, which uses a three-phase in-vehicle charger.

[0084] For the four AC charging terminals 6 shown in Figure 1 , the situation shown by way of example in , thus results in a situation in which the first phase is loaded by two single-phase internal vehicle chargers, the second phase is not loaded, and the third phase is loaded by a single-phase internal vehicle charger. Furthermore, all three phases are ideally loaded uniformly by the three-phase internal vehicle charger. Thus, the first phase can be strongly overloaded and the second phase strongly underloaded, so that overall a very asymmetrical loading of the power supply device 12 results.

[0085] In the illustrated example, the following remedy can thus be easily achieved, in that for one of the two AC charging terminals loaded on the first phase, the phase conversion device 18 performs a phase switch or phase transfer, so that the first phase of the vehicle internal charger using a single phase is switched to the second connecting line, whereby an interconnection with the second supply line is then obtained. As a result, the vehicle internal charger with a single phase is then interconnected with the first, second or third supply line, respectively.

[0086] In order to operate the charging station and in particular to control the phase change device 18 in order to reduce or minimize the asymmetrical load of the three-phase power supply device, a symmetry control device 28 is provided. The symmetry control device 28 receives information about all currents or connecting lines or connecting lines of the AC charging terminals 6. For this purpose, terminal sensors 34 are provided in each case. The terminal sensors 34 thus provide information about each current between each AC charging terminal and the power supply device 12. For this purpose, four current values ​​are transmitted to the symmetry control device 28 at each AC charging terminal 6 for each of the four currents, namely three phase currents and one neutral current.

[0087] However, it is also conceivable that the corresponding terminal sensor 34 or the evaluation unit coupled thereto has already converted the four currents according to the symmetrical component method, that is, into a positive phase-sequence system current I 1,n , negative phase sequence system current I 2,n and zero system current I 0,n The current can be transmitted to the symmetry control device 28 via the terminal sensor line 36 and this Figure 1 The subscript n of each of the sub-currents indicates that three such currents are detected for each AC charging terminal 6. The subscript n therefore represents the corresponding number of the AC charging terminal. Figure 1 In the case shown in the current illustration, the subscript N therefore runs from 1 to 4.

[0088] The symmetry control device 28 can now determine the optimization based on the current values ​​it obtains via the terminal sensor line 36 and then correspondingly control the phase change device 18 in order to achieve the connection assignment between the corresponding output port 26 and the connecting lines 31, 32 and 33 of the AC charging terminal 6 by correspondingly switching the phase change device 18. For this purpose, corresponding control signals can be transmitted from the symmetry control device 28 to the phase change device 18, and for this purpose, for example, a terminal control line 38 can be provided to each phase change device 18.

[0089] Figure 1 The additional diagram illustrates the use of an active rectifier 16 for further reducing possible asymmetries of the current in the current supply device 12. For this purpose, it is first proposed that the symmetry control device 28 receives current data from the current supply device 12. For this purpose, a current supply sensor 40 is provided, which can detect all four currents of the current supply device 12. It or an associated evaluation unit can also propose a transformation according to the symmetrical component method and correspondingly determine the positive phase sequence system current I1, the negative phase sequence system current I2 and the zero system current I0 and supply them to the symmetry control device 28 via a supply sensor line 42. From this, that is, taking into account the detected current of the AC charging terminal 6, the symmetry control device 28 can generate a preset negative phase sequence system current component I2 as a desired value and supply it to the active rectifier 46 via a rectifier control line 44.

[0090] Together with the current demand of the DC charging terminal 8 and the negative phase sequence system current I 2sollTogether with the desired values ​​of , the active rectifier 16 can be controlled so that after the inverse transformation according to the symmetrical components from this view, the corresponding three-phase current is taken from the power supply device 12. The active rectifier 16 and thus the DC charging terminal 8 are thus supplied, that is, take current from the power supply device 12, but at the same time the negative phase sequence system current is connected, which has been preset by the symmetry control device 28. In this way, a further homogenization of the current in the power supply device 12 can be achieved.

[0091] Figure 2 Shown for minimization Figure 1 Flowchart 200 of the asymmetry in the current conveying device 12. First, Figure 2 In step 0, indicated as S0 in FIG. 2 , a static phase symmetry is performed. The static symmetry block 202 indicates the content. Thus, the phase change device gradually shifts all AC charging terminals that are not used at the moment from one AC charging terminal to the next AC charging terminal by one phase in order to achieve uniformity in this regard. Figure 1 This can be shown by way of example, assuming that none of the four AC charging terminals 6 shown are used at this moment, i.e. according to Figure 1 The view of the first phase change device 18 from the left remains as it actually is, the next phase change device 18 switches one more switch position to the right, the third phase change device switches two more positions to the right and the fourth phase change device again remains as it actually is. If there is a fifth phase change device, it switches one more position again, the sixth phase change device switches two more positions, and so on.

[0092] This provides a good basis for being able to achieve an approximately uniform distribution of the phases as a starting condition in any case when connecting a single-phase in-vehicle charger. If the vehicle is already connected to the AC charging terminal for charging, the proposed static phase symmetry is only proposed for the AC charging terminal which has not been used therein until now. As soon as the vehicle is connected, a completely good symmetry is initially present as a starting condition. However, the connected vehicle or the corresponding AC charging terminal can then be taken into account in the further minimization of the asymmetry, as is carried out in a subsequent step.

[0093] Correspondingly, in order to specifically minimize the asymmetry, step 1 is first proposed, which is Figure 2 204 and includes a plurality of blocks. First, in the sorting block 204, the AC charging terminals are sorted according to the magnitude of the respective largest phase currents of the AC charging terminals. Different variants are contemplated here. One variant is that only the AC charging terminals with a single-phase or two-phase current consumption are taken into account in the sorting. This can also be done according to the Figure 1 The embodiments are respectively identified by the terminal sensors 34 .

[0094] Another variant is that the AC charging terminals are sorted group by group according to the size of the maximum phase current. Therefore, the first group may include all AC charging terminals showing a single-phase current load, and the second group includes all AC charging terminals showing a two-phase current load. Possibly, the AC charging terminals showing a three-phase current load may also be sorted into a third group.

[0095] With the aid of the sorting, the minimization of the asymmetry is now continued in groups or in another way in the change block 306. In the change block 206, the connecting lines with the maximum phase currents are then gradually connected to the first, second and third phases in the order that has already been derived from the sorting block 204. This is to be understood in particular that for the AC charging terminal with the largest maximum phase current, the connecting line is connected to the first phase, for the AC charging terminal with the second largest maximum current, the connecting line is connected to the second phase, and for the AC charging terminal with the third largest maximum phase current, the connecting line is connected to the third phase.

[0096] In the AC charging terminal with the fourth largest maximum phase current, however, the same order is not started from the beginning, but returned to. Therefore, the AC charging terminal with the fourth largest maximum phase current is also connected to the third phase, the fifth largest maximum phase current is connected to the second phase, and the sixth largest maximum phase current is connected to the first phase.

[0097] All of this, ie in particular the processes in the sorting frame 204 and in the change frame 206, is proposed for an AC charging terminal, such as the AC charging terminal 6, and is correspondingly carried out with the aid of a phase change device, such as Figure 1 The phase change device 18 is implemented.

[0098] exist Figure 2 In step 2, shown as S2 in FIG. 1 , it is proposed to further minimize the asymmetry, which ideally leads to the current conveying device, such as Figure 1 The current in the current supply device 12 is completely symmetrical, and the asymmetry is at least very strongly minimized, in particular close to zero.

[0099] For this purpose, one or possibly more active rectifiers are now used, such as Figure 1 For this purpose, the total asymmetry that remains despite the measures according to the change block 206 is detected in the residual asymmetry determination block 208. This can be particularly referred to Figure 1 The embodiment is realized by the current delivery sensor 40, which provides its detection results to the symmetry control device 28. From this, the negative phase sequence system current required for compensation can then be determined. This can be performed in the negative phase sequence system determination block 210. The result is a negative phase sequence system current, such as Figure 1 Negative phase sequence system currentI2,soll , which is provided as a desired value to the active rectifier 16. Correspondingly, the implementation is carried out in the rectifier control block 212, which implements the presetting of the negative phase-sequence system current and thus actually connects the negative phase-sequence system current to the power supply device 12, that is, to the three currents or the three-phase current system present there.

[0100] Ideally, this would allow a symmetrical three-phase current system to be achieved in the power supply device 12 .

[0101] It can be taken into account that the charging process of an electric vehicle is usually not carried out permanently statically and constantly, but in particular the charging current decreases over time. In particular at the beginning of the charging process, the initial charging current can be significantly reduced, for example from 100% to 30% or even less. At least when the state of charge is 80%, the charging process can be slowed down towards the end. With the help of this change, the asymmetry can also be changed. In particular, the minimization of the asymmetry according to Figure 2 After the process is successful, the asymmetry may increase or reappear. Therefore, it is proposed to repeat step 2, i.e. the execution in the residual asymmetry determination block 208, the negative phase sequence system determination block 210 and the rectifier control block 212 frequently. The activation of certain loads, such as devices for cooling, heating, pre-air conditioning, during or at the end of the charging process, affects the power consumption.

[0102] This is Figure 2 In the scope of step S2, it is indicated by a return. The repetition can be repeated at a first repetition time T1. The first repetition time T1 can be selected to be very small, for example in the scope of 1 minute, or it can be selected to be 10s or less. In fact, all of these embodiments in blocks 208, 210 and 212 can be implemented in a computerized manner and can thus be quickly repeated. However, it is even considered that the embodiments of blocks 208, 210 and 212 are repeated substantially continuously or approximately continuously, i.e. according to a computer map.

[0103] However, it has also been recognized that the final minimization of the asymmetry by means of the controlled rectifier can only compensate for the residual asymmetry. It is therefore proposed that the reduction of the asymmetry is repeated regularly according to the execution of the sorting block 204 and the change block 206, i.e. according to a second repetition time T2. The second repetition time can be, for example, 1 minute or more. It is also conceivable that the second repetition time is selected to be several minutes and, for example, 3 minutes or more. Preferably, the second repetition time is selected to be less than 10 minutes.

[0104] This makes it possible to reduce or balance large or strongly unbalanced loads, such as are to be expected from a plurality of vehicle-internal single-phase or two-phase chargers, first via a phase conversion device, such as phase conversion device 18 , and to further reduce or even eliminate any remaining asymmetries via active rectifiers.

[0105] Two specific examples of possible asymmetries are presented below together with different proposals for resolution.

[0106] It should be taken into account here that the view and considerations according to the method of symmetrical components are based on two examples from the table "Symmetrical components". Therein I1 represents the positive phase sequence system current, I2 represents the negative phase sequence system current and I0 represents the zero system current. Asymmetry I asy Calculate from it according to the following formula:

[0107]

[0108] The current values ​​of the two examples are normalized to the reference values.

[0109] Example 1: Charging process with 1 PU DC (symmetrical AC load) and 0.33 PU AC at phase A (total current):

[0110]

[0111] This leads to the asymmetry:

[0112]

[0113] Feeding in additional negative phase-sequence system current via a DC charger:

[0114]

[0115] Total current after compensating the total system:

[0116]

[0117] This leads to the asymmetry:

[0118]

[0119] Thus, in Example 1, the 50% asymmetry is eliminated by feeding in a negative phase sequence system current, for example via Figure 1 The embodiment of the active rectifier 16 drops to 25%.

[0120] Example 2: Charging process with 1 PU DC (symmetrical AC load) and 4 x 0.33 PU AC at phase A (total current):

[0121]

[0122] This leads to the asymmetry:

[0123]

[0124] AC charging point four times with 240° and AC charging point 3 with 120° phase rotation:

[0125]

[0126] This leads to the asymmetry:

[0127]

[0128] Total current after compensation of negative phase sequence system:

[0129]

[0130] This leads to the asymmetry:

[0131]

[0132] In the second example, there is a still larger overall asymmetry at the beginning, namely 114%. The asymmetry can correspond to Figure 2 In the first step of step S1, some phases are transformed to reduce to 28%. Figure 1 The fourth AC charging terminal of the AC charging terminal 6 shown in FIG. performs a 240° phase rotation. Therefore, the connecting line is switched in two counts, about Figure 1 That is, the first connection line 31 is connected to the third supply line 23 , and 32 is connected to 21 and 33 is connected to 22 .

[0133] In addition, in can correspond to the second to last in the right Figure 1 A phase rotation of 120° is performed at the third AC charging terminal of the AC charging terminal 6 shown in FIG. There, the connecting line is thus switched by one count, with respect to Figure 1 That is, the first connection line 31 is connected to the second supply line 22 , and 32 is connected to 23 and 33 is connected to 21 .

[0134] In can correspond to Figure 2 In the second step of step S2, by feeding in the negative phase sequence system current, for example, by Figure 1 The active rectifier 16 of the embodiment can further reduce the asymmetry to 14%.

Claims

1. A charging station (1) for charging an electric vehicle (24), comprising: - a plurality of AC charging terminals (6), each used to charge an electric vehicle (24) via an alternating current, wherein - Each of the AC charging terminals (6) is connected to a three-phase current supply device (12) via a phase conversion device (18) in order to be supplied with a three-phase current, wherein - the current supply device (12) has three supply lines (21, 22, 23) for providing three voltage phases, - Each AC charging terminal (6) has three connection lines (31, 32, 33) for connecting to the three supply lines (21, 22, 23) to apply three voltage phases to the connection lines (31, 32, 33), wherein - each phase change device (18) is designed to change the connection assignment between the three supply lines (21, 22, 23) and the three connecting lines (31, 32, 33), It is characterized in that The charging station (1) - comprises symmetrical control means (28) for controlling the phase change device (18), wherein - the symmetry control device (28) is configured to control the phase change device (18) so as to minimize the phase asymmetry of the supply lines (21, 22, 23), and wherein - the symmetry control device (28) is configured to: - sorting the AC charging terminals (6) according to whether they operate in single-phase, two-phase or three-phase mode, - and in connection therewith, controlling the phase change device (18) to minimize the phase asymmetry of the supply lines (21, 22, 23).

2. The charging station (1) according to claim 1, It is characterized in that The symmetry control device (28) is configured to: - sorting the AC charging terminals (6) according to their instantaneous current consumption, and - controlling the phase change device (18) in relation thereto in order to minimize the phase asymmetry of the supply lines (21, 22, 23).

3. The charging station (1) according to claim 1 or 2, It is characterized in that - the symmetry control device (28) is configured to sort the AC charging terminals (6) according to their instantaneous current consumption, or - sorting the AC charging terminals (6) with a single-phase current consumption into a first group and the AC charging terminals (6) with a two-phase current consumption into a second group, and sorting the groups one by one according to their instantaneous current consumption, wherein - for each of the AC charging terminals (6), the connecting line with the greatest current consumption is respectively identified as the most heavily loaded line and its current consumption is respectively taken into account as the maximum phase current of the AC charging terminal (6), - the AC charging terminals (6) are sorted in current order according to their maximum phase current, The phase change device (18) respectively sets or changes the connection assignment so that the line with the largest load is connected to the first, second and third supply lines (21, 22, 23) of the three supply lines (21, 22, 23) in a sequentially changed manner according to the current.

4. The charging station (1) according to claim 1 or 2, It is characterized in that - the symmetry control device (28) is configured to sort all the connecting lines into a current sequence according to their current consumption, independently of the corresponding AC charging terminal (6), - the phase change device (18) respectively sets or changes the connection assignment so that all the connection lines are connected to the first, second and third supply lines (21, 22, 23) of the three supply lines (21, 22, 23) in a changed manner according to their line sequence, wherein - As a boundary condition check, for any AC charging terminal no two or three connections are connected to the same supply line.

5. The charging station (1) according to claim 1 or 2, It is characterized in that The symmetry control device (28) is configured to determine the connection assignments based on the current consumption of the connecting lines (31, 32, 33) of all AC charging terminals (6) at least with a single-phase or two-phase current consumption, via an optimization calculation, in order to minimize phase asymmetry.

6. The charging station (1) according to claim 1 or 2, It is characterized in that - having at least one DC charging terminal (8) and an active rectifier (16) connected upstream, - the active rectifier (16) is connected to the current supply device (12), and The active rectifier (16) is configured to load the three supply lines (21, 22, 23) differently.

7. The charging station (1) according to claim 1 or 2, It is characterized in that The charging station (1) is configured to repeat the change of the connection assignment after an asymmetry threshold value is exceeded, the asymmetry threshold value being a measure of the asymmetry of the power supply device, or to repeat in recurring cycles.

8. The charging station (1) according to claim 1 or 2, It is characterized in that The power supply device is connected to a grid connection point (2) of the power supply grid.

9. The charging station (1) according to claim 3, It is characterized in that The symmetry control device (28) is configured to sort the AC charging terminals (6) with single-phase or two-phase current consumption according to their instantaneous current consumption.

10. The charging station (1) according to claim 3, It is characterized in that The AC charging terminals (6) are sorted group by group in current order according to their maximum phase currents.

11. The charging station (1) according to claim 3, It is characterized in that In an AC charging terminal (6) with two-phase current consumption, the second current-carrying line is connected to a following supply line, ie the second, third or first supply line (22, 23, 21).

12. The charging station (1) according to claim 1 or 2, It is characterized in that - the symmetry control device (28) is configured to sort the AC charging terminals (6) according to their instantaneous current consumption, or - sorting the AC charging terminals (6) with a single-phase current consumption into a first group, sorting the AC charging terminals (6) with a two-phase current consumption into a second group, and sorting the AC charging terminals (6) with a three-phase current consumption into a third group, and sorting them group by group according to their instantaneous current consumption, wherein - for each of the AC charging terminals (6), the connecting line with the greatest current consumption is respectively identified as the most heavily loaded line and its current consumption is respectively taken into account as the maximum phase current of the AC charging terminal (6), - the AC charging terminals (6) are sorted in current order according to their maximum phase current, The phase change device (18) respectively sets or changes the connection assignment so that the line with the largest load is connected to the first, second and third supply lines (21, 22, 23) of the three supply lines (21, 22, 23) in a sequentially changed manner according to the current.

13. The charging station (1) according to claim 12, It is characterized in that In an AC charging terminal (6) with a three-phase current consumption, one of the remaining lines is connected to a following supply line, ie the second, third or first supply line (22, 23, 21).

14. The charging station (1) according to claim 3, It is characterized in that The connection assignment is performed such that, according to the current sequence, - a first maximum load line is connected to the first supply line, - a second maximum load line is connected to the second supply line, - a third maximum load line is connected to the third supply line, - a fourth maximum load line connected to the third supply line, - a fifth maximum load line connected to the second supply line, and - A sixth maximum load line is connected to the first supply line.

15. The charging station (1) according to claim 3, It is characterized in that The connection assignment is performed so that the current is sequentially connected in groups. - a first maximum load line is connected to the first supply line, - a second maximum load line is connected to the second supply line, - a third maximum load line is connected to the third supply line, - a fourth maximum load line connected to the third supply line, - a fifth maximum load line connected to the second supply line, and - A sixth maximum load line is connected to the first supply line.

16. The charging station (1) according to claim 4, It is characterized in that The next three connection lines are connected to the third, second and first supply lines.

17. The charging station (1) according to claim 5, It is characterized in that A plurality of required switching processes of the phase change device (18) are taken into account.

18. The charging station (1) according to claim 17, It is characterized in that Minimizing the number of switching processes is considered as an auxiliary condition.

19. The charging station (1) according to claim 6, It is characterized in that The active rectifier (16) is configured to connect a negative-sequence system current (I2) to a three-phase power supply device in order to reduce a current asymmetry in the power supply device (12).

20. The charging station (1) according to claim 6, It is characterized in that The symmetry control device (28) is configured to control the active rectifier (16) to reduce the asymmetry of the current.

21. The charging station (1) according to claim 7, It is characterized in that The repetitive cycle is repeatedly run through continuously after a repetition time (T2), which is selected to be shorter than an average charging process of the electric vehicle (24).

22. The charging station (1) according to claim 21, It is characterized in that The repetition time (T2) is selected in the range of one minute to five minutes.

23. The charging station (1) according to claim 8, It is characterized in that The power supply device is connected to a grid connection point (2) of the power supply grid via a transformer (14).

24. A method for charging an electric vehicle (24) by means of a charging station (1), wherein the charging station (1) has a plurality of AC charging terminals (6), each of which is designed to charge the electric vehicle (24) by means of an alternating current, wherein - each of the AC charging terminals (6) is supplied with a three-phase current via a phase conversion device (18), which is connected to a three-phase current supply device (12) of the charging station (1), - providing three voltage phases via the current supply device (12) having three supply lines (21, 22, 23), - Each AC charging terminal (6) has three connecting lines (31, 32, 33), which are respectively connected to three supply lines (21, 22, 23) and via which three voltage phases are applied to the connecting lines (31, 32, 33), wherein - each phase change device (18) changes the connection assignment between three supply lines (21, 22, 23) and three connecting lines (31, 32, 33) in order to reduce the current asymmetry in the current supply device (12), wherein the charging station (1) - comprises symmetrical control means (28) for controlling the phase change device (18), wherein - the symmetry control device (28) is configured to control the phase change device (18) so as to minimize the phase asymmetry of the supply lines (21, 22, 23), and wherein The method uses a charging station (1) according to any one of claims 1 to 23.

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