Charging system for electric vehicles

Abstract

Charging system (10) for electric vehicles, comprising at least one charging station (12) for connecting a traction battery of an electric vehicle to the respective charging station (12) via a charging cable (13), comprising power electronics (16), wherein the respective charging station (12) is connected to an electrical power and voltage supply network (14) which provides a defined electrical network power via the interposition of the power electronics (16), characterized by at least one electrical storage device (18) which is connected between the electrical power and voltage supply network (14) and the respective charging station (12) in such a way that it charges depending on the electrical network power of the electrical power and voltage supply network (14) and discharges depending on a charging rate of the power electronics (16) and the respective charging station (12), a cooling device (19), wherein the respective charging station (12),The power electronics (16) and the electrical storage device (18) are connected to the cooling device (19), which provides a defined thermal cooling capacity. At least one thermal storage device (20) is connected to the cooling device (19), the respective charging station (12), the power electronics (16), and the electrical storage device (18) in such a way that the thermal storage device or a cooling medium thereof heats up depending on the power loss of the power electronics (16), the respective charging station (12), and the respective electrical storage device (18), and cools down depending on the thermal cooling capacity of the cooling device (19).

Description

The present invention relates to a charging system for electric vehicles.For charging an electric vehicle, namely for charging a traction battery of an electric vehicle, the so-called AC charging mode and the so-called DC charging mode are known.In the AC charging mode, the electric vehicle is connected via its on-board charger to an electric power and voltage supply network which provides alternating voltage or alternating current, wherein the on-board charger carries out the conversion into direct current. In the so-called AC charging mode, the charging speed for the traction battery is limited. Charging times in the AC charging mode are several hours per 100 kilometers of range.A more rapid charging of the traction battery of an electric vehicle can take place via a DC charging mode, wherein, in the DC charging mode, the traction battery is not charged via the on-board charger of the electric vehicle, but rather in that the traction battery is connected directly to a vehicle-external charging station, which provides direct current for charging the traction battery, bypassing the on-board charger. Higher charging speeds can be realized with the DC charging mode compared to the AC charging mode, but it has not yet been possible to provide charging speeds for the traction battery of an electric vehicle in the DC charging mode that are on the order of magnitude of a refueling process in conventional, combustion-engine-driven vehicles.Charging systems for electric vehicles known to date, which serve for DC charging of the traction battery of electric vehicles, cannot ensure correspondingly high charging speeds up to now, since, on the one hand, the electrical grid power provided by the available electrical power and voltage supply grid may not be sufficient to provide a desired charging speed, and, on the other hand, taking into account the fact that high losses also occur at high charging speeds, which lead to a high generation of heat, but which cannot be dissipated to an adequate extent up to now.EP 2 572 431 B1 discloses a charging system for electric vehicles having a plurality of charging stations. The traction battery of an electric vehicle can be charged in the region of each charging station, wherein the traction battery of the respective electric vehicle can be coupled to the respective charging station via a charging cable in the region of each charging station. The charging system of EP 2 572 431 B1 furthermore has power electronics with a plurality of power converters in order to convert the grid power provided by an electrical power and voltage supply grid for charging the traction battery of the electric vehicles.EP 2 986 468 B1 discloses a further charging system for electric vehicles. A charging station is disclosed here, to which a traction battery of an electric vehicle can be coupled via a charging cable of the charging station. The traction battery of the electric vehicle can be cooled via a cooling body provided by the charging station, namely in that the cooling body of the charging station makes thermal contact with a contact surface of the traction battery.US 2013 / 0 069 592 A1 discloses a charging system for electric vehicles having a plurality of charging stations. The charging stations are connected to a remote location that has power converters, a connection box and free spaces for further assemblies. The remote location includes an air conditioner. The air conditioner may cool a room of the remote location. Heat from the power converters may be dissipated to heat a building or water, for example. Thus, the heat can be transferred to a storage device, such as a hot water tank or a heat storage device installed underground.US 2017 / 0 028 862 A1 discloses a charging cable of a charging station, wherein an electric vehicle can be connected to the charging station for charging via a plug of the charging cable. The charging cable has a fluid channel. This serves for cooling the charging cable.DE 10 2010 041 919 A1 and US 2013 / 0 221 918 A1 disclose further prior art.There is therefore a need for a charging system for electric vehicles which, on the one hand from an electrical point of view and, on the other hand, from a thermal point of view, allows the electric vehicles to be charged at a high charging speed or at a charging power, in particular of more than 300 kW per vehicle.This object is achieved by a charging system for electric vehicles according to claim 1.The charging system comprises at least one electrical storage device which is connected between the electrical power and voltage supply network and the respective charging station in such a way that it charges as a function of the electrical power of the electrical power and voltage supply network and discharges as a function of a charging speed of the power electronics and the respective charging station.The charging system further comprises at least one recooling device, wherein the respective charging station, the power electronics and the or each electrical storage are connected to the recooling device which provides a defined thermal recooling power.The charging system further comprises at least one thermal storage unit, which is connected to the cooling device, the respective charging station, the power electronics unit and the or each electrical storage unit in such a way that the same or a cooling medium thereof heats up as a function of the loss line of the power electronics unit, the respective charging station and the respective electrical storage unit and cools down as a function of the thermal cooling power of the cooling device.The charging system according to the invention comprises at least one electrical storage unit and at least one thermal storage unit.The or each electrical storage device can be connected to an electrical power and voltage supply network and charged by the same, namely at a charging speed which is dependent on the electrical power of the electrical power and voltage supply network. For charging a traction battery of a motor vehicle, the electrical energy stored in the electrical storage can be called up in order to charge the traction battery starting from the electrical energy storage device, preferably supported by the electrical current and voltage supply network, at a higher speed than the charging of the electrical energy storage device starting from the electrical current and voltage supply network is possible.In particular, an electrical energy store makes it possible to provide a charging power of more than 300 kW per vehicle. High charging speeds can thus be realized.The waste heat arising at such high charging powers for electric vehicles can be dissipated via the or each thermal storage unit in order to prevent unacceptably high heating of, for example, the power electronics unit or the respective charging station or the respective electrical storage unit.The heat absorbed by the thermal store is then dissipated via the cooling device which provides a cooling back power in order to cool the thermal store or the cooling medium used by the thermal store.According to an advantageous development, the or each electrical storage device and the or each thermal storage device are matched to one another with regard to their respective dynamics. The dynamic tuning of electrical storage and thermal storage is particularly preferred for providing an efficient charging system for electric vehicles. It is possible to charge a plurality of electric vehicles at a sufficient charging speed.The thermal cooling back power of the or each thermal storage device is preferably adapted to the electrical grid power of the power and voltage supply grid in such a way that, on the one hand, the charging of the electrical storage device and the cooling back of the thermal storage device take place within a defined period of time after a charging process of a traction battery of an electric vehicle. An efficient charging system for electric vehicles can thus be provided in a particularly advantageous manner. It is possible to charge a plurality of electric vehicles at a sufficient charging speed.Preferably, the or each electrical storage device and the or each thermal storage device are matched to one another with regard to their respective capacitance.For this purpose, an electrical capacity of the or each electrical storage device and a thermal capacity of the or each thermal storage device are preferably matched to one another in such a way that, for a defined number of charging processes of traction batteries, the electrical storage device provides the required charging energy and the thermal storage device provides the required cooling energy.The matching of the capacities of electrical storage and thermal storage is of particular advantage for providing an efficient charging system. It is possible to charge a plurality of electric vehicles at a sufficient charging speed.The electrical capacity of the or each electrical storage device is preferably furthermore designed to maximize a service life of the electrical storage device and / or to take into account a grid stability of the electrical power and voltage supply grid. Taking these boundary conditions into account, the efficiency of the charging system can be further increased.Preferably, the thermal capacity of the or each thermal storage of the charging system is further configured depending on ambient temperature influences of the charging system. Taking this boundary condition into account as well, a further increase in efficiency of the charging system is possible, since it is possible to minimize the cooling back performance of the cooling back device to be reserved.The electrical capacity of the or each electrical storage device of the charging system and the thermal capacity of the or each thermal storage device of the charging system and the thermal cooling back power of the cooling back device of the charging system are preferably designed for an empirically or statistically determined number of charging processes per unit of time and for an empirically or statistically determined charging energy per charging process. This makes it possible to configure a charging system in a targeted manner for a location-specific request. This allows an efficient and economical charging system to be provided.According to an advantageous development, the or each electrical storage device of the charging system and the or each thermal storage device of the charging system are matched to one another in such a way that a thermal energy content of the thermal storage device, which corresponds to a product of a thermal capacity and a maximum permissible temperature range, is sufficient for the same number of charging processes as the electrical storage device can operate on the basis of its electrical energy content. These details are provided to provide an efficient charging system on which a plurality of electric vehicles can be charged at high charging speed.According to an advantageous development, the power electronics and the or each electrical energy store and the charging cable of the or each charging station can be cooled with the aid of the cooling device. In particular, the cooling of the charging cables of the charging stations is important in order to effectively dissipate the waste heat occurring at high charging powers or charging speeds and to exclude overheating of the charging cables.Preferred developments of the invention are evident from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being restricted thereto. The following shows: FIG. 1 shows a schematic illustration of a charging system for electric vehicles according to the invention; FIG. 2 is a diagram illustrating configuration details of the charging system of FIG. 1 ; FIG. 3 is a detail of the charging system of FIG. 1 ; and FIG. 4 is an alternative detail of the charging system of FIG. 1.The invention relates to a charging system for electric vehicles. Such a charging system is also referred to as a charging park.FIG. 1 shows a highly schematic view of the basic design of a charging system 10 according to the invention for electric vehicles 11. the charging system 10 has a plurality of charging stations 12 for electric vehicles, wherein in the region of each of these charging stations 12, which are also referred to as charging stations, in each case one electric vehicle 11 can be charged, namely by coupling the traction battery of the electric vehicle 11 to the charging station 12 via a charging cable 13 of the respective charging station 12.FIG. 1 shows two electric vehicles 11 which are connected to the respective charging station 12 via a charging cable 13.The charging system 10 can be supplied with electrical voltage or electrical current starting from an electrical power and voltage supply network 14, of which a transformer 15 is shown. The electrical current and voltage supply network 14 is characterized by a defined electrical network power, which is predefined as a boundary condition depending on the location.In charging systems known up to now, the charging speed or charging power for the electric vehicles 11 depends in a limiting manner on the electric grid power of the electric current and voltage supply network 14.The charging system 10 for electric vehicles further has power electronics 16 which, in the exemplary embodiment shown in FIG. 1, are provided by two power electronics modules 17 which provide a power converter for each charging station 12.Each charging station 12 of the charging system 10 can be connected or coupled to the electrical power and voltage supply network 14 with the interposition of the power electronics 16 or of the power converter provided by the power electronics 16.The electric vehicle charging system 10 includes at least one electric storage 18.The respective electrical storage device 18 of the charging system 10 is connected between the electrical power and voltage supply network 14 and the respective charging station 12 of the charging system 10 and thus the power electronics 16 of the charging system 10 in such a way that the respective electrical energy storage device 18 can be charged as a function of the electrical grid power of the electrical power and voltage supply network 14 and can be discharged as a function of a charging speed of the power electronics 16 or of the respective charging station 12 when the traction battery of an electric vehicle is charged.In this case, the charging speed at which the electrical energy store 18 can be charged starting from the electrical power and voltage supply network 14 is limited by the electrical power supply system and is lower than the charging speed of the respective charging station 12 for charging the traction battery of an electric vehicle, in order thus to make it possible for electric vehicles 11, namely traction batteries thereof, to be charged at a high charging speed and high charging power than would be possible exclusively via the power and voltage supply network 14, wherein the charging power per vehicle is preferably more than 300 kW.The charging system 10 further comprises a recool device 19 and at least one thermal storage 20.The cooling device 19 provides a defined thermal cooling back power for cooling the respective charging station 12 and the power electronics 16 and the electrical storage 18.In order not to limit the heat that can be dissipated in the region of the charging stations 12, the power electronics 16 and the electrical energy store 18 by the thermal cooling back power of the cooling back device 19, the charging system 10 furthermore comprises at least one thermal store 20.The thermal storage unit 20 is coupled to the recooling device 19, the respective charging station 12, the power electronics 16 and the respective electrical energy storage unit 18, so that the thermal storage unit 20 or a cooling medium thereof can be heated as a function of the power loss of the power electronics unit 16, the power loss of the charging stations 12 and the power loss of the electrical energy storage unit 18 and cooled as a function of the thermal recooling power of the recooling device 19.In the exemplary embodiment shown, a common electrical storage device 18 and a common thermal storage device 20 are provided for all charging stations 12. It is also possible to provide a plurality of electrical storage devices 18 and a plurality of thermal storage devices 20, for example a common electrical storage device and a common thermal storage device 20 in each case for a group of charging stations 12.The or each electrical storage device 18 accordingly makes it possible to compensate for possibly temporarily too low a network power of the electrical power and voltage supply network 14. In this case, a relatively slow charging of the electrical storage device 18 takes place starting from the electrical power and voltage network 14 and a rapid discharge thereof as soon as an electric vehicle, namely the traction battery of an electric vehicle, is charged at a charging station 12. The electrical power and voltage grid 14 preferably supports the electrical storage 18 when discharging a traction battery of an electric vehicle.With the aid of the thermal store 20, it is possible to reduce a cooling back performance to be reserved by the cooling back system 19, in order thus to dimension the cooling back system 19 smaller and to reduce costs in this respect.According to an advantageous development, the or each electrical storage device 18 and the or each thermal storage device 20 are matched to one another with regard to their respective dynamics and / or with regard to their respective capacitance. Preferably, both the dynamics and the capacitances and thus the storage capacity of the or each electrical storage device 18 and of the or each thermal storage device 20 are matched to one another. This makes it possible in particular to adapt the thermal cooling power to be kept ready to the electric charging power kept ready. The or each electrical storage device 18 provides electrical energy for charging processes of traction batteries of electric vehicles 11 if appropriate supported by the electrical power and voltage network. The or each thermal storage device 20 serves, supported by the cooling back system 19, to absorb and remove waste heat which arises during charging processes.It is preferably provided that the thermal cooling back power provided to the cooling back device 19 for the or each thermal storage unit 20 is adapted to the electrical grid power of the electrical power and voltage supply grid which serves for charging the or each electrical storage unit 18 in such a way that, on the one hand, the charging of the electrical energy storage unit 18 and, on the other hand, the cooling back of the thermal storage unit 20 takes place within a defined time period after a charging process of a traction battery of an electric vehicle 11. This is preferred for adjusting the charging dynamics and cooling dynamics of the charging system.In this case, it is provided in particular that, on the one hand, the charging of the electrical store 18 and, on the other hand, the cooling back of the thermal store 20 takes place at the same speed after the charging process of a traction battery of an electric vehicle 11. This is particularly preferred for adjusting the charging dynamics and cooling dynamics of the charging system.Furthermore, the capacities of the accumulators 18, 19 are matched to one another, namely the electrical capacity of the or each electrical accumulator 18 and the thermal capacity of the or each thermal accumulator 20.Preferably, the electrical capacity of the or each electrical storage device 18 and the thermal capacity of the or each thermal storage device 20 are matched to one another such that, for a defined number of charging processes of traction batteries of electric vehicles 11, the or each electrical storage device 18 provides the required charging energy and the or each thermal storage device 20 provides the required cooling energy.It is particularly preferably provided that the electrical capacity of the or each electrical storage device 18 and the thermal capacity of the or each thermal storage device 20 and the thermal cooling back power of the cooling back device 19 are designed for an empirically or statistically determined number of charging processes per unit time and for an empirically or statistically determined charging energy per charging process in order to optimally design the degrees of freedom of the charging system, specifically the size or capacity of the or each electrical storage device 18, the size or capacity of the or each thermal storage device 20 and the cooling back power of the cooling back device 19, in a manner matched to the location of the charging system and location-specific boundary conditions.The electrical grid power of the electrical power and voltage supply grid 14 is predefined and should be taken into account as a boundary condition. Furthermore, as boundary conditions to be taken into account in the design, as explained above, the statistically or empirically determined number of charging processes per unit time, i.e. an empirically or statistically determined charging frequency, a statistically or empirically determined requested charging energy per charging process, the number of charging points of the charging system and the desired or predefined charging power per charging process and a predefined waiting time acceptable between charging processes, are used.In FIG. 2, the design of the degrees of freedom of the charging system that is matched to one another is visualized in a highly schematic manner over time t, namely the design of the capacities of the storage devices 18, 19 and of the cooling-back performance of the cooling-back device. Thus, the curve profile 21 of FIG. 2 visualizes an electrical state of charge of an electrical storage device 18 and the curve profile 22 visualizes a thermal capacity of the thermal storage device 20.Phases 23 of FIG. 2 visualize the profile of state of charge 21 and thermal receptivity 22 during a charging process of a traction battery. Phases 24 of FIG. 2 visualize the state of charge 21 and the thermal receptivity 22 during a recovery of the storage devices 18, 20 after completion of a charging process of a traction battery. In phase 25 of FIG. 2, the state of charge 21 of the electrical storage device 18 and the thermal capacity 22 of the thermal storage device 20 are visualized for a situation in which neither a charging process takes place nor a recovery of the storage devices 18, 20 is required, in which case the electrical storage device 18 is thus again fully charged and the full thermal capacity of the thermal storage device 20 is available.The electrical power of the charging system is matched on average over time at least to power which is called up when charging traction batteries of electric vehicles. The cooling-back performance of the cooling-back device 19 is designed such that, on average over time, the waste heat which arises during charging of traction batteries of electric vehicles is dissipated. The memories 18 and 20 allow an extension of the time duration over which averaging is performed.When designing the capacity of the electrical storage device 18, a maximizing of the service life of the electrical storage device 18 is preferably taken into account, namely by keeping a charging stroke and discharging stroke of the electrical storage device 18 within defined limits. Furthermore, when designing the electrical storage device 18, a network stability of the electrical power and voltage supply network 14 is preferably taken into account.If, due to the location, there is a high probability of failure for the electric power and voltage supply network 14, the electrical capacity of the electric storage device 18 is designed for this purpose. Furthermore, in determining the capacity of the electrical storage device 18, not only the stability of the power and voltage supply network 14 can be taken into account, but also an energy which can be provided by the power and voltage supply network 14 as a result of other boundary conditions and which can be dependent on the time of day, the time of year, the day of the week, changing energy costs and the like. Related data can be determined empirically and taken into account in the design via a Poisson or lognormal distribution.In determining the thermal capacity of the thermal storage 20, ambient conditions of the charging system may be considered, such as ambient temperatures prevailing locally in the area of the charging system.FIG. 3 shows a detail of the charging system 10 in the area of a thermal accumulator 20 that interacts with a recooling device 19. FIG. 3 shows the thermal storage unit 20 in which a coolant is kept ready, wherein the coolant is taken from the storage unit 20 via a feed line 28 via a pump 26 for cooling an assembly 27 to be cooled, in order to be guided in the direction of the assembly 27 to be cooled, and wherein the coolant, after cooling the assembly 27, is returned in the direction of the thermal storage unit 20 via a return line 29 and is guided in advance via the cooling device 19 installed in the return line 29, which cooling device comprises a heat exchanger 30 in the exemplary embodiment of FIG. 3 which interacts with a fan 31.In FIG. 3, the quantity of air is defined via the fan 31 and is conducted via the heat exchanger 30 for cooling in order to cool the heated coolant conducted via the return line 29 before it is supplied into the thermal store 20. The assembly 27 can be an assembly of the power electronics 16, the electrical storage device 18 or else a charging column 12. As already stated, all assemblies on which waste heat arises are cooled, that is to say both assemblies of the power electronics 16, assemblies of the electrical store 18 and assemblies of the charging stations 12, in particular the charging cables 13 thereof.FIG. 4 shows a development of the detail of FIG. 3, in which, in addition to the heat exchanger 30 and fan 31, an air conditioning compressor 32 is present as a further assembly of a cooling device 19. In contrast to FIG. 3, the coolant can then be cooled below the ambient temperature by means of such an air conditioning compressor 32. Under certain circumstances, it is possible to dispense with the heat exchanger 30 and fan 31 when using an air conditioning compressor 32. Then, when the recool device 19 uses both the heat exchanger 30 and the air conditioner compressor 32 and the temperature of the refrigerant in the return 29 is below the ambient temperature, the fan 31 can be turned off. If, on the other hand, the return temperature of the coolant in the return 29 is above the ambient temperature, the fan 31 can be switched on in order to cool the coolant already in the region of the heat exchanger 30 and then to ensure further cooling below the ambient temperature via the air conditioning compressor 32.

Claims

Charging system (10) for electric vehicles, having at least one charging station (12) for coupling a traction battery of an electric vehicle via a charging cable (13) of the respective charging station (12) to the same, having power electronics (16), wherein the respective charging station (12) is connected, with the power electronics (16) being interposed, to an electric power and voltage supply network (14) which provides a defined electric grid power, characterized at least one electrical storage device (18) which is connected between the electrical power and voltage supply network (14) and the respective charging station (12) in such a way that it charges on the basis of the electrical power of the electrical power and voltage supply network (14) and discharges on the basis of a charging speed of the power electronics device (16) and the respective charging station (12), a cooling device (19), the respective charging station (12), the power electronics device (16) and the or each electrical storage device (18) being connected to the cooling device (19) which provides a defined thermal cooling power, at least one thermal storage device (20) which is connected to the cooling device (19), the respective charging station (12), the power electronics device (16) and the or each electrical storage device (18) in such a way that the same or a cooling medium thereof is connected on the basis of loss conduction of the power electronics device (16), heating of the respective charging station (12) and of the respective electrical store (18) and cooling as a function of the thermal cooling back performance of the cooling back device (19).Charging system according to Claim 1, characterized in that the or each electrical storage device (18) and the or each thermal storage device (20) are matched to one another with respect to their respective dynamics.Charging system according to Claim 1 or 2, characterized in that the thermal cooling back power of the cooling back device (19) for the or each thermal storage unit (20) is adapted to the electrical grid power of the electrical power and voltage supply grid (14) in such a way that, on the one hand, the charging of the electrical storage unit (18) and the cooling back of the thermal storage unit (19) take place within a defined time period after a charging process of a traction battery of an electric vehicle.Charging system according to Claim 3, characterized in that, on the one hand, the charging of the electrical store (18) and the cooling back of the thermal store (20) take place at the same speed after a charging process of a traction battery of an electric vehicle.Charging system according to one of Claims 1 to 4, characterized in that the or each electrical storage device (18) and the or each thermal storage device (19) are matched to one another with respect to their respective capacity.Charging system according to one of Claims 1 to 5, characterized in that an electrical capacity of the or each electrical store (18) and a thermal capacity of the or each thermal store (20) are matched to one another in such a way that, for a defined number of charging processes of traction batteries, the electrical store provides the required charging energy and the thermal store provides the required cooling energy.Charging system according to claim 5 or 6, characterized in that the electrical capacity of the or each electrical storage (18) is further designed to maximize a lifetime of the electrical storage (18).Charging system according to one of Claims 5 to 7, characterized in that the electrical capacity of the or each electrical store (18) is designed, furthermore, taking into account a grid stability of the electrical power and voltage supply grid (14).Charging system according to one of Claims 5 to 8, characterized in that the thermal capacity of the or each thermal store (20) is furthermore designed as a function of ambient temperature influences of the charging system.Charging system according to one of Claims 1 to 9, characterized in that the electrical capacity of the or each electrical store (18) and the thermal capacity of the or each thermal store (20) and the thermal cooling back power of the cooling back device are designed for an empirically or statistically determined number of charging processes per unit of time and for an empirically or statistically determined charging energy per charging process.Charging system according to one of Claims 1 to 10, characterized in that the or each electrical storage device (18) and the or each thermal storage device (20) are matched to one another in such a way that a thermal energy content of the thermal storage device (20), which corresponds to a product of a thermal capacity and a maximum permissible temperature range, is sufficient for the same number of charging processes as the electrical storage device (18) can service on the basis of its electrical energy content.Charging system according to one of Claims 1 to 11, characterized in that a heat exchanger (30) cools a coolant which the or each thermal store (20) holds ready for recooling, wherein the heat exchanger (30) is integrated into a return line (29) leading to the thermal store (20), and wherein a fan (31) is assigned to the heat exchanger (30).Charging system according to one of Claims 1 to 12, characterized in that an air-conditioning compressor (32) cools a coolant which the or each thermal store (20) holds ready for recooling.Charging system according to one of Claims 1 to 13, characterized in that the cooling-back device (19) and the or each thermal store (20) cools the power electronics (16) and the or each electrical energy store (18) and the charging cable (13) of the or each charging station (12).

Images