Method for coordinating charging processes of several electrically powered motor vehicles and control device for carrying out the method

Abstract

Method for coordinating charging processes (18) of several electrically powered motor vehicles (13) at different electric charging stations (12) supplied via a common electrical network (14), wherein, prior to the charging processes (18), planning data (16) concerning the respective charging process (18) of the motor vehicle (13) is received from each of the motor vehicles (13) by a central control device (11), and on the basis of the planning data (16) of the motor vehicles (13), an individual charging plan (17) is generated for each motor vehicle (13), characterized in that the charging plans (17) are coordinated with each other in such a way that, according to the charging plans (17), at any given time (t), the total maximum load change (25) in the network (14) is less than a predetermined threshold value.where, according to the charging schedules (17), in the case of predominantly simultaneous charging processes (18), a time offset (19) in the range of 1 s to 2 min is provided for switching times to start and / or end the charging processes (18).

Description

[0001] The invention relates to a method for coordinating the charging processes of several electrically powered motor vehicles, which may be connected to different electric charging stations, wherein these charging stations are supplied via a common electrical network. The invention also includes a control device by means of which the method according to the invention can be carried out.

[0002] Currently, two main charging methods are used for electric vehicles (EVs). Either the vehicle is charged immediately at full power after being plugged into the charging station, or the charging process begins at a predetermined time. This latter method is also known as timer charging. Both methods are considered problematic, however, as they can have a negative impact on the electrical grid. Activating a charging process causes a change in the grid load, which can lead to voltage fluctuations, such as dips or spikes. Since the number of electric vehicles is expected to increase in the coming years, these effects are likely to become more pronounced.

[0003] Especially when many charging processes start or end simultaneously on a shared electrical grid, as can occur with timer charging, unpredictable voltage dips or load peaks can arise. The extent or magnitude of such voltage fluctuations depends on the charging power of the vehicles. Currently, charging power is often only 3.7 kW. However, the trend is moving towards charging powers greater than 11 kW, as higher charging powers allow vehicles to be charged in a correspondingly smaller fraction of the otherwise required charging time. A combination of numerous simultaneously starting / ending charging processes with such high charging power leads to serious repercussions on the electrical grid. These include voltage dips, frequency shifts, overloading of grid transformers, and the potential tripping of fuses.

[0004] DE 10 2010 002 237 A1 discloses the coordination of charging processes for multiple motor vehicles. The vehicles are charged via connections to a local electrical network, with the switch-on and switch-off times determined according to a predefined energy distribution plan, ensuring that a maximum available power is not exceeded.

[0005] Protection of a grid against overload caused by the charging processes of multiple vehicles is also known from JP H 08 116626 A. According to this patent, the charging processes of several electrically powered vehicles are coordinated in such a way that the total charging power does not exceed the electrical power that the grid can provide.

[0006] The reserving of charging power at a charging station is known from DE 11 2012 005 488 T5.

[0007] While current technology makes it possible to coordinate the start and end times of charging processes for electric vehicles, the switching on and off of each charging process is still "hard," meaning that the charging power can be completely switched on or off. If this occurs in rapid succession or even simultaneously, it can also lead to an overload of the grid. For example, an electrical grid can be supplied by a transformer whose transmission capacity is switchable. If the electrical power drawn from the grid changes faster than the transformer can adjust (for example, by switching on or off electrical windings), this can also lead to an overload, even though the transformer could theoretically provide the required power after switching if it had enough time to do so.

[0008] US patent 2011 / 0285345 A1 discloses an electric vehicle charging station with multiple charging terminals, each capable of connecting a motor vehicle to charge its battery. A large number of voltage converters are provided, with enough operating at all times to ensure all vehicles receive the required charging power. Towards the end of each charging cycle, the charging power is gradually reduced to transition from constant current to constant voltage charging.

[0009] German patent application DE 10 2014 221 555 A1 discloses a local electrical island grid that can be coupled to a public electrical grid. The local island grid includes a renewable energy generation plant and a battery storage system. The charging and discharging of the battery storage system is controlled such that the electrical power fed from the local island grid into the public grid changes only with a predetermined maximum power gradient. The aim is to operate the battery storage system efficiently by keeping it as close as possible to a target state of charge. To adjust the power gradient, the power exchange between the energy storage system and the local island grid is controlled.

[0010] The invention is based on the objective of adapting electrical charging processes to the performance of an electrical network.

[0011] The problem is solved by the subject matter of the independent patent claims. Advantageous further developments of the invention result from the dependent patent claims, the following description, and the figures.

[0012] The invention is based on the method described above for coordinating the charging processes of several electrically powered vehicles at different charging stations, which are, however, supplied via a common electrical network. The charging stations can be geographically distributed, or at least some of them can be arranged in a common housing. The method according to the invention can be implemented by a central control device, which can, for example, be designed as an internet server. Before the charging processes begin, the central control device receives planning data from each of the vehicles concerning the respective charging process.Through its planning data, each vehicle can specify how much electrical energy it requires, the maximum charging power it wishes to draw, and / or the latest time by which the energy should be transferred. Based on this planning data, the control unit generates an individual charging plan for each vehicle. This charging plan describes the power profile of the charging power to be transferred over time. In other words, it is a schedule that specifies, for each point in time, how much electrical power the vehicle should draw from or receive from its charging station.

[0013] According to the invention, these charging schedules are coordinated in such a way that, at any given time, the maximum overall change in the load, i.e., the load change, in the electrical network is less than a predetermined threshold. In other words, superimposing or summing the charging schedules results in an overall charging schedule whose temporal gradient, mathematical derivative with respect to time, or maximum change within a predetermined time interval always exhibits a value less than the threshold. In other words, the charging processes of the motor vehicles only result in switching operations and / or changes in charging power that are also limited with respect to the temporal gradient or maximum change over time.A change in the electrical load in the network over a predetermined unit of time, for example per second or per ten seconds, is therefore always smaller than the maximum value determined by the threshold.

[0014] The invention offers the advantage that the charging power switched within the electrical network can be limited with respect to its change over time. This ensures that the overall charging behavior of the vehicles takes into account the temporal adjustment with which electrical power can be supplied or built up in the electrical network, for example, by a transformer. Additionally or alternatively, the inductance of the electrical network, such as line inductances and / or the inductance of a transformer, can also be considered. This allows, for example, voltage spikes during switching operations to be kept below a maximum value.

[0015] In conventional charging schedules, as known from the prior art, charging processes are switched at 15-minute intervals, and several simultaneous switching processes may also be provided. To avoid this relatively coarse scheduling, the invention provides that, according to the charging schedules, in the case of predominantly simultaneous charging processes, a time offset of 1 second to 2 minutes is provided between the switching times for the start and / or end of the respective charging process. "Predominantly simultaneous" means that the charging processes overlap by at least 70 percent, and in particular 80 percent. Such charging processes can also be started and / or ended almost simultaneously. The time offset is then at most one second to two minutes.Nevertheless, this prevents voltage fluctuations in the electrical network, as the load change resulting from switching on and / or off a charging process is always limited to the threshold value by gradually increasing or decreasing the charging power, for example.

[0016] The invention also includes further developments that result in additional advantages.

[0017] To allow the threshold for temporal changes to be individually adapted to the grid, a further development provides for the control device to receive characteristic data from at least one grid component. Specifically, this at least one grid component includes the aforementioned transformer and / or a respective grid connection point of the charging stations and / or an electrical line of the grid. The characteristic data can then specify switchable power levels of the transformer and / or a charging station and / or a power limit of the transformer and / or a grid connection point and / or an inductance value. Power levels refer to the described switchable stages, for example, of a transformer, such as those that can result from switching electrical windings on or off.A switch between power levels, for example by means of a transformer, can also be provided at a grid connection point.

[0018] In particular, the invention provides that, according to the charging schedules, the charging processes of several vehicles are started or stopped within a 15-minute interval. Specifically, more than two, and especially more than three, charging processes are started or stopped. Thus, a high degree of time synchronization of the switching operations (activating and / or deactivating the charging processes) is possible. It is not necessary for a vehicle to wait 15 minutes for its charging process to complete.

[0019] To construct charging schedules that do not exceed the aforementioned threshold for load change, a further development approach stipulates that one, some, or all of the charging schedules must include an increase function for the start and / or a decrease function for the end of the charging process. The increase function and / or the decrease function each comprise, in particular, a ramp or a multi-stage step function. "Multi-stage" specifically refers to two or more stages. The increase function and / or decrease function thus results in at least an intermediate value between the full charging power of the respective vehicle and / or charging station on the one hand and 0 kW on the other. In other words, there is no abrupt switch between 0 kW and full charging power. There is a transition range through which the charging power is gradually increased or decreased.The transition range can be implemented by power electronics in the charging control unit of the respective motor vehicle and / or the charging station.

[0020] To implement the charging plans, the individual charging plans are sent to the respective vehicle and / or charging station where the vehicle is to be charged, according to a training course. This then configures the respective charging control unit of the vehicle and / or the charging station for the charging process. Thus, the charging plans are implemented by a charging control unit of the respective vehicle and / or a charging control unit of the charging station.

[0021] To coordinate charging processes, the invention also provides a control device for coordinating the charging processes of several electrically powered vehicles at different charging stations connected via a common electrical network. An electrically powered vehicle can be a purely electric vehicle or a hybrid vehicle. The electrical network can be a low-voltage three-phase network or a medium-voltage network. The control device can be configured as an internet server. In general, the control device includes a processor unit configured to carry out an embodiment of the method according to the invention. For this purpose, the processor unit can include at least one microcontroller and / or at least one microprocessor.The processor device can include program code configured to execute the embodiment of the method according to the invention when executed by the processor device. The program code can be stored in a data memory of the processor device.

[0022] The following are exemplary embodiments of the invention described. This is illustrated by: Fig. 1 a schematic representation of a system with a central control device and several electrically powered motor vehicles, as made possible by the invention; and Fig. 2 a schematic representation of an alternative design of the system of Fig. 1.

[0023] The exemplary embodiments described below are preferred embodiments of the invention. In these exemplary embodiments, the described components each represent individual features of the invention that can be considered independently of one another. Each of these features further develops the invention independently and can therefore be considered part of the invention individually or in a combination other than that shown. Furthermore, the described embodiments can also be supplemented by other features of the invention already described.

[0024] In the figures, functionally identical elements are each provided with the same reference symbols.

[0025] Fig. Figure 1 shows a system 10 with a control device 11 and charging stations 12, at each of which an electrically powered vehicle 13 is to be charged. "Charging" means that the electrical energy storage of the respective vehicle 13 is charged with electrical energy from an electrical network 14, which can receive the electrical energy, for example, via a transformer 15 from an electrical distribution network, such as a medium-voltage or high-voltage network. The control device 11 can receive planning data 16 from the vehicles 13 or from a server managing the vehicles 13. This planning data can describe the charging requirements of the vehicles 13. For example, the charging power of the vehicles 13 and / or time information regarding the available charging time can be signaled by the planning data 16.Depending on the planning data 16, the control device 11 can then generate an individual charging plan 17 for each motor vehicle 13 or its charging station 12 and send it to the respective charging station 12 and / or the motor vehicle 13. Fig. Figure 1 shows exemplary charging schedules 17 over time t, which describe the charging power P to be drawn or transferred at each point in time. A time offset 19 can be provided between the respective start and end times of the individual charging processes 18 in the charging schedules 17. Additionally or alternatively, a ramp function 20 and / or a ramp function 21 can be provided in each charging schedule 17. Fig. 1. The increase function 20 and the reduction function 21 are each designed as multi-stage step functions.

[0026] In Fig. Figure 1 further illustrates how the temporal superposition of the individual charging plans 17 results in an overall charging plan 22, which describes the feedback effect of the charging stations 12 on the network 14. The overall charging function 22 is in Fig. Figure 1 is shown in a smoothed form, meaning the multi-stage step functions are no longer depicted. The overall charging function 22 is limited with respect to load changes. At every point during the charging processes 18, there is always a load change, which is always smaller than a predetermined threshold.

[0027] To adapt this threshold value, or more generally the charging plans 17, to the network 14, characteristic data 23 can be received by the control device 11 from at least one network component of the network. A network component can be, for example, a network connection point of the respective charging station 12 and / or the transformer 15. The characteristic data 23 can also be retrieved from a central data source, for example, from the operator of the network 14.

[0028] The resulting total charging power 24 and the maximum load change, i.e. a maximum gradient 25 or maximum load jump (in the case of stepwise change) can thus be adapted to the network 14.

[0029] Fig. Figure 2 shows the system 10 again in a variant in which the increase function 20 and the reduction function 21 of the individual charging plans are not stepped or multi-stage, but gradual or as a ramp.

[0030] The control device, by means of the charging schedules 17, prevents an overload of the grid 14 by staggering the activation and deactivation of the charging processes 18 and by varying the ramp-up and ramp-down of the charging power P of individual vehicles 13. Overall, the charging processes 18 are thus compatible with or compensable for the grid infrastructure. The resulting total charging power 24 can be adapted to the residual power available in the grid 14 (maximum power minus the power already drawn by other electrical consumers).

[0031] Even with a large number of vehicles 13, their charging requirements (described by the planning data 16) can be met without negatively impacting the power grid or network 14. The high charging power of vehicles can be managed by selectively modifying or adapting the charging processes.

[0032] The possible implementation options are shown in the figures. The control device 11 manages information about transformers, power limitations of the grid connection points, and the number and charging capacities of the vehicles to be charged. The power limitations at grid connection points and transformers are country-specific, particularly their power gradients. A crucial factor is the time offset 19 between the charging processes 18 of the different vehicles 13. This offset can be calculated in advance by a corresponding function in the control device 11 and can be specified in the individual charging schedules 17. The individually tailored charging schedule can be communicated or transmitted to all vehicles 13. This can be done using a mobile network connection, a WLAN connection (Wi-Fi - Wireless Local Area Network), or powerline communication.The charging control units of the motor vehicles and / or the charging stations 12 can then evaluate and / or adopt the charging plans 17 and thereby carry out the control of the charging processes 18 (for example, switching on and off) according to the charging plans 17.

[0033] A charging station 12 can, for example, be designed as a charging station.

[0034] To maintain the time offsets 19, time synchronization between all charging control units can be ensured using state-of-the-art technology. The individual vehicles 13 then start their charging processes at staggered intervals, causing the sum of the drawn charging power P to increase uniformly or in stages, resulting in the uniformly rising overall charging curve 22. When the charging processes 18 are completed, the vehicles 13 are also disconnected from the grid 14 one after the other to prevent impermissibly high voltage increases in the grid 14.

[0035] The described method can be combined with a conventional charging schedule, which can provide for switching on and off every 15 minutes. In addition to such a charging schedule, the control device is designed to reduce power surges that can be caused by the simultaneous activation of vehicle charging processes in network 14, in order to prevent overvoltage and / or undervoltage in network 14.

[0036] Overall, the examples show how the invention can provide temporal coordination of the start and end times of charging processes.

Claims

[1] Method for coordinating charging processes (18) of several electrically powered motor vehicles (13) at different electric charging stations (12) supplied via a common electrical network (14), wherein, prior to the charging processes (18), planning data (16) concerning the respective charging process (18) of the motor vehicle (13) is received from each of the motor vehicles (13) by a central control device (11) and, on the basis of the planning data (16) of the motor vehicles (13), an individual charging plan (17) is generated for each motor vehicle (13), characterized by, that the charging schedules (17) are coordinated in such a way that, according to the charging schedules (17), at any time (t) there is a total maximum load change (25) in the network (14) which is less than a predetermined threshold, wherein, according to the charging schedules (17), in the case of predominantly simultaneous charging processes (18), a time offset (19) in a range of 1s to 2 min is provided for switching times to start and / or end the charging processes (18). [2] Method according to claim 1, wherein the control device (11) receives characteristic data (23) from at least one network component of the network (14) and the threshold value is set depending on the characteristic data (23) of the at least one network component. [3] Method according to claim 2, wherein the at least one network component comprises a transformer (15) and / or a respective network connection point of the charging stations (12) and / or an electrical line of the network (14). [4] Method according to claim 2 or 3, wherein the characteristic data (23) specify switchable power levels and / or a power limit and / or an inductance value. [5] Method according to one of the preceding claims, wherein, according to the charging schedules (17), the charging processes (18) of several of the motor vehicles (13) are started or stopped within a 15-minute time interval. [6] Method according to one of the preceding claims, wherein one or some or all of the charging schedules (17) each provide an increase function (20) for the start and / or a reduction function (21) for the end of the charging process (18), whereby at least one intermediate value between a full charging power and 0 kW is obtained. [7] Method according to claim 6, wherein the ramp function (20) and / or the reduction function (21) each comprise a ramp or a multi-stage step function. [8] Method according to one of the preceding claims, wherein the individual charging plans (17) are sent to the respective motor vehicle (13) and / or to the respective charging station (12) at which the respective motor vehicle (13) is to be charged, and thereby a respective charging control unit of the motor vehicle (13) and / or the charging station (12) is configured for the charging process (18). [9] Control device (11) for coordinating charging processes (18) of several electrically powered motor vehicles (13) at different electric charging stations (12) connected to a common electrical network (14), characterized by that the control device (11) has a processor unit configured to perform a method according to one of the preceding claims.

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