Bidirectional DC wallbox for electric vehicles

Abstract

Bidirectional DC wallbox (10) with galvanic isolation, comprising a) a separating element (11) which is designed to reversibly connect and disconnect the DC wallbox (10) to an AC voltage network (30); b) a rectifier (12) with a power factor correction filter, which is arranged to rectify a three-phase alternating voltage; c) a DC-DC converter (21) with galvanic isolation, comprising i. an inverter (13); ii. an AC bus system (14) having a primary side and a galvanically isolated secondary side; iii. at least one active rectifier (15, 17, 19) configured to convert an alternating voltage into a direct voltage of a predetermined voltage level; iv. at least one charging output (16, 18, 20) for connection to a charging socket of an electric vehicle (40, 41, 42); wherein the output of the inverter (13) is connected to the primary side of the AC bus system (14) and the input of the at least one active rectifier (15, 17, 19) is connected to the secondary side of the AC bus system (14), and the at least one charging output (16, 18, 20) is connected to the output of the at least one active rectifier (15, 17, 19); and wherein the DC wallbox (10) comprises a base module having an isolating element (11); an AC / DC converter with PFC (12);and a DC / DC converter with galvanic isolation, which contains a DC / AC converter (13), an AC bus (14) and an AC / DC converter (15), and wherein at least one extension module (22, 23) is connected to the secondary side of the AC bus (14) of the base module, which extension module comprises an active rectifier (17, 19) and a charging output (18, 20) for connection to a charging socket of an electric vehicle (40, 41, 42), each extension module (22, 23) containing a control unit for regulating voltage and current.;

Description

[0001] The present invention relates to a bidirectional direct current charging station for wall mounting (DC wallbox) for private use, to which several electric vehicles can be connected in parallel, and to a method for operating the DC wallbox.

[0002] Today's electric vehicles feature a combo charging socket, which enables direct current (DC) charging at 480V / 150kW and alternating current (AC) charging at 230V or 400V and a maximum of 22kW. Currently, 98% of customers charge their electric vehicles at home using the AC infrastructure. The electric vehicle's onboard charger converts the AC voltage into DC voltage to charge the traction battery. The maximum charging power for three-phase AC and 32A current is 22kW. Private DC charging systems are currently very rare due to their complexity and cost.

[0003] However, the situation will change significantly when bidirectional charging systems become available in the private sector. These bidirectional charging systems are being built as DC systems due to their more flexible conversion options and cost advantages. Customers will thus charge and discharge their cars at a DC wallbox even in private settings.

[0004] If a customer owns several electric vehicles and wants to connect them simultaneously to their charging infrastructure or home energy management system, for example to charge them with photovoltaic power, they are forced to purchase another DC wallbox and have it installed in the garage.

[0005] DE 10 2016 123 924 A1 relates to power electronics for charging at least one electrically powered vehicle. The power electronics comprises at least two modules, each with at least one terminal pair with a DC output, at least one rectifier, at least one AC input, at least one DC voltage intermediate circuit, and a number of switching elements. The switching elements are arranged at and / or between the DC outputs of the at least two modules in such a way that at least one serial and one parallel circuit configuration can be dynamically set between the at least two modules by appropriate switching states of the switching elements.

[0006] DE 10 2011 079 430 A1 discloses a direct current charging station for charging multiple energy storage devices. The charging station features a station-side rail system (DC bus) for modularly expanding the charging station with any number of direct current charging interfaces. The infrastructure-side voltage is rectified and then further processed by downstream parallel-connected DC / DC converters. However, parallel charging of multiple vehicles at the charging station is not permitted according to DIN EN 61851-23 (VDE 0122-2-3).

[0007] WO 2005 008 808 A2 discloses a charging system for simultaneously charging the batteries of multiple battery-powered vehicles. The charging system comprises one or more DC-DC power converters with one or more charging ports configured for plugging into the batteries. The DC-DC power converters are each configured to be selectively connected to more than one charging port to selectively provide higher connected power levels. The DC-DC power converters are connected to an AC rectifier via a DC bus. The AC rectifier is connected to an AC source with a limited power rating. The AC charging system also includes a controller that controls the operation of the DC-DC power converters so that the total power consumption of the AC rectifier does not exceed the power rating.The system is further configured to allow the DC-DC power converters to discharge selected batteries to obtain energy to charge other batteries, thus enabling battery swapping.

[0008] The article by Manthey, Nora: "A brave new world of DC home charging." October 17, 2018. URL: https: / / www.electrive.com / 2018 / 10 / 17 / a-brave-new-worldof-dc-home-charqinq / concerns commercially available bidirectional DC wallboxes.

[0009] US 2016 / 0 176 305 A1 discloses a power management device configured to connect multiple DC elements to multiple AC elements. The device comprises a DC interface module connected to the DC elements, a bidirectional AC-to-DC converter connected to the DC interface module, and an AC interface module connected to the bidirectional AC-to-DC converter and the AC elements.

[0010] US 2015 / 0 375 628 A1 concerns a charger with a bidirectional AC / DC converter that enables the power supply of two sockets with different voltages. The charger is particularly suitable for use as an on-board device in an electric vehicle. The device enables both the power supply of a traction battery with a relatively high voltage and the supply of loads from the low-voltage grid.

[0011] EP 3 406 479 A1 relates to a device for a power system comprising a plurality of electrical power sources and a housing operatively connected to the power sources at a plurality of input terminals. A plurality of loads are operatively connected to the housing via a plurality of cables at a plurality of output terminals. The housing comprises the input and output terminals and a control unit. A plurality of selection units are operatively connected to the control unit, and a plurality of power converters are connected to a plurality of connection paths. The selection units are connected to at least one of the plurality of switches connected in the connection paths. A plurality of sensor units are operatively connected to the control unit, which is configured to detect a plurality of parameters in the connection paths.In response to the parameters sensed by the sensor units, the selection units select the connection paths between the electrical power sources and the loads.

[0012] US 2017 / 0 005 584 A1 discloses a multi-output power conversion circuit using a phase shift controller that receives a DC voltage at the input and delivers a plurality of modulatable DC voltages at the output, the circuit comprising a transformer having an input and a plurality of outputs, the input being connected to an inverter comprising at least two switches and configured to convert a DC voltage into an AC voltage, and each output being connected to a controlled rectifier configured to convert an AC voltage into a DC voltage, each controlled rectifier comprising a magnetic storage inductor connected to an AC-DC converter comprising at least two switches, the power conversion circuit further comprising a control module configured tothat it generates phase-shifted control signals suitable for controlling the switching of the switches of the inverter and the controlled rectifiers.,

[0013] From Schwaiger, Verena: “BIDIRECTIONAL DC WALLBOX WITH DC-BUS INTERFACE AND INTEGRATED BIDIRECTIONAL ENERGY METER”, Technical Disclosure Commons, (January 24, 2019), URL: https: / / www.tdcommons.org / cgi / viewcontent.cgi?article=2979&context=dpub s series is a bidirectional DC wallbox with a DC bus interface and an integrated energy meter.

[0014] Against this background, the invention has set itself the task of providing a bidirectional direct current charging station for wall mounting (DC wallbox) for electric vehicles, which is easy to expand and enables the standard-compliant simultaneous charging of several electric vehicles.

[0015] The object is achieved according to the invention by a device having the features of claim 1 and a method having the features of claim 7. Embodiments and developments of the invention emerge from the dependent claims and the description.

[0016] The invention relates to a bidirectional DC wallbox with galvanic isolation, comprising (a) a disconnecting element designed to reversibly connect and disconnect the DC wallbox from an AC voltage network; (b) a rectifier (AC / DC converter) with a power factor correction (PFC) filter designed to rectify a three-phase alternating voltage; c) a DC / DC converter with galvanic isolation, comprising i. an inverter (DC / AC converter); ii. an alternating current bus system (AC bus) with a primary side and a galvanically isolated secondary side; iii. at least one active rectifier (AC / DC converter) designed to convert an alternating voltage into a direct voltage of a predetermined voltage level; iv. at least one charging output for connection to a charging socket of an electric vehicle, wherein the output of the inverter i. is connected to the primary side of the AC bus system ii. and the input of the at least one active rectifier iii. is connected to the secondary side of the AC bus system ii. and the at least one charging output iv. to the output of the at least one active rectifier iii.is connected; and wherein the DC wallbox comprises a base module comprising an isolating element; an AC / DC converter with PFC; and a DC / DC converter with galvanic isolation comprising a DC / AC converter, an AC bus and an AC / DC converter, and wherein at least one extension module comprising an active rectifier and a charging output for connection to a charging socket of an electric vehicle is connected to the secondary side of the AC bus of the base module, each extension module comprising a control unit for regulating voltage and current.

[0017] The bidirectional DC wallbox with galvanic isolation according to the invention comprises a separating element configured to reversibly connect and disconnect the DC wallbox from an AC voltage grid. In one embodiment, the AC grid is a public low-voltage grid that provides three-phase alternating current. The AC voltage is typically 380 V or 400 V. In one embodiment, the separating element is designed with electromechanical contactors. In another embodiment, the separating element is designed with semiconductor switches.

[0018] The bidirectional DC wallbox according to the invention also comprises a rectifier (AC / DC converter) with a power factor correction filter (PFC), which is designed to rectify a three-phase AC voltage. The AC / DC converter is bidirectional, meaning it can also convert direct current into three-phase alternating current. In one embodiment, the AC / DC converter comprises power semiconductors, for example, IGBTs and MOS-FETs. In one embodiment, the inputs of the AC / DC converter are connected to the isolating element via inductors. In another embodiment, a capacitor is connected between the outputs of the AC / DC converter.

[0019] The bidirectional DC wallbox according to the invention comprises a bidirectional active DC / DC converter (DC / DC converter) with galvanic isolation. This converts the output voltage of the AC / DC converter into at least one DC voltage of a predetermined voltage level. The voltage level is adjustable, so that different output voltages of the DC / DC converter can be selected, e.g., 400 V or 800 V. In one embodiment, the DC / DC converter has multiple outputs whose output voltages can be individually selected, so that each output can provide a different output voltage if required. In one embodiment, the charging power of the DC wallbox can be divided as desired between the outputs of the DC / DC converter.

[0020] The bidirectional active DC / DC converter comprises i) an inverter (DC / AC converter); ii) an AC bus system (AC bus) with a primary side and a galvanically isolated secondary side; iii) at least one active rectifier (AC / DC converter) designed to convert an AC voltage into a DC voltage of a predetermined voltage level; and iv) at least one charging output for connection to a charging socket of an electric vehicle. The output of the inverter i) is connected to the primary side of the AC bus system ii), and the input of the at least one active rectifier iii) is connected to the secondary side of the AC bus system ii). The at least one charging output iv) is connected to the output of the at least one active rectifier iii).

[0021] The inverter i) is also bidirectional and converts the DC voltage applied to its inputs into a single-phase AC voltage. In one embodiment, the DC / AC converter comprises power semiconductors, such as IGBTs and MOSFETs.

[0022] The alternating current bus system (AC bus) ii) comprises a primary side and a galvanically isolated secondary side. In one embodiment, the AC bus ii) comprises a transformer. In this embodiment, the primary winding of the transformer forms the primary side of the AC bus ii), the secondary winding is part of the secondary side of the AC bus ii). The primary side of the AC bus system ii) is connected to the output of the inverter i). In one embodiment, several connections for active AC / DC converters iii), e.g. additional secondary windings, are provided on the secondary side of the AC bus ii). The standardized interface on the secondary side allows modular expansion of the DC wallbox and the creation of additional charging options. To do this, expansion modules with active AC / DC converters iii) only need to be connected to the additional secondary windings in order to use the DC wallbox for connecting several vehicles orThis will provide users with additional, cost-effective charging options that are galvanically isolated from each other and from the grid infrastructure.

[0023] The bidirectional active DC / DC converter comprises at least one active rectifier (AC / DC converter) iii) configured to convert an AC voltage into a DC voltage of a predetermined voltage level or, conversely, to convert a DC voltage of a predetermined voltage level into a single-phase AC voltage. In one embodiment, the AC / DC converter comprises power semiconductors, for example, IGBTs and MOSFETs.

[0024] The at least one active AC / DC converter has a charging output iv) for connection to a charging socket of an electric vehicle, e.g. a charging cable with a charging plug that fits into the charging socket. In a further embodiment, the bidirectional active DC / DC converter comprises a plurality of AC / DC converters iii), each with a charging output iv). In one embodiment, the bidirectional active DC / DC converter comprises two AC / DC converters iii), in another embodiment three AC / DC converters iii), in a further embodiment four AC / DC converters iii), in yet another embodiment five AC / DC converters iii). This means that several vehicles or consumers can be connected to the DC wallbox at the same time. The active AC / DC converters iii) each provide a flexible charging voltage.

[0025] A base module of the bidirectional DC wallbox according to the invention comprises an isolating element; an AC / DC converter with PFC; and a DC / DC converter with galvanic isolation, which includes a DC / AC converter, an AC bus, and an AC / DC converter. In one embodiment, the base module is designed for a connected load of 22 kW. The base module is required only once for the DC wallbox.

[0026] One or more additional active AC / DC converters iii) are connected to the AC bus of the base module as extension modules. The extension modules are fed directly from the AC voltage on the secondary side of the AC bus and each provide a flexible charging voltage. The control unit for regulating voltage and current is contained in each extension module. The distribution of the charging power between the vehicles is freely selectable. For example, in a DC wallbox with three charging ports, the total charging power of 22 kW can be distributed so that 11 kW of charging power is allocated to a first connected vehicle, 7 kW to a second connected vehicle, and 4 kW to a third connected vehicle.

[0027] With the DC wallbox according to the invention, it is possible to charge the energy storage units of several electric vehicles of different voltage classes simultaneously, e.g. one vehicle with 400 V and another vehicle with 800 V. Due to the galvanic isolation of the individual AC / DC converters and the bidirectionality, it is also possible to charge the energy storage unit of a connected electric vehicle directly from the energy storage unit of another connected electric vehicle, thus realizing direct charging from vehicle to vehicle.

[0028] This allows the operator of the DC wallbox to implement a second, third or fourth bidirectional charging option without having to purchase and install additional complete DC wallboxes.

[0029] In one embodiment, the DC wallbox according to the invention comprises a disconnection device. The disconnection device is configured to disconnect the DC wallbox from the AC voltage grid and the connected vehicles or consumers and to de-energize it.

[0030] In a further embodiment, the DC wallbox according to the invention comprises a communication unit. The communication unit is configured for communication between the DC wallbox and a user's mobile device, e.g., a smartphone, PDA, laptop, or tablet. Communication can take place, for example, via mobile communications or Wi-Fi, or via NFC or Bluetooth. A user can use the communication unit to transmit control commands to the DC wallbox and, for example, adjust the distribution of the total charging power to the individual charging outputs. A corresponding software application ("app") can be used on the mobile device for this purpose.

[0031] The invention also relates to a method for operating the DC wallbox according to the invention. The method comprises a) connecting at least one energy storage device to a charging output of the DC wallbox; b) connecting the DC wallbox to an AC network by closing the isolating element; and c) the transmission of electrical energy from the AC network into the at least one connected energy storage device or from the at least one connected energy storage device into the AC network.

[0032] In one embodiment of the method, the AC grid is a public low-voltage grid that provides three-phase alternating current. The AC voltage is typically 380 V or 400 V.

[0033] In one embodiment of the method, an output voltage can be individually adjusted at each charging output of the DC wallbox. In another embodiment of the method, the total connected load of the DC wallbox can be freely distributed among the individual charging outputs. In one embodiment, the connected load of the DC wallbox is 22 kW.

[0034] The DC wallbox according to the invention offers a number of advantages. Thanks to its modular design, expanding the system to include additional charging stations means that no additional complete DC wallbox is required; instead, only an expansion module is required. This reduces costs. The distribution of charging power between the connected vehicles can be freely selected. Galvanic isolation makes it possible to charge vehicles with different traction voltages simultaneously. Due to the bidirectionality, all connected vehicles can feed power back into the grid. It is also possible to transfer electrical energy from the energy storage device of one connected vehicle directly to the energy storage device of another connected vehicle. The DC wallbox also offers the option of connecting a home energy storage device. Further advantages and embodiments of the invention can be found in the description and the accompanying drawings.

[0035] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0036] The invention is illustrated schematically in the drawings using embodiments and will be further described with reference to the drawings. It shows: Fig. 1 an embodiment of the DC wallbox according to the invention with a DC voltage output; Fig. 2 an embodiment of the DC wallbox according to the invention with three DC voltage outputs; Fig. 3 a circuit diagram of a DC wallbox according to the invention with three DC voltage outputs.

[0037] Fig. 1 schematically shows an embodiment of the DC wallbox 10 according to the invention with a DC output 16 and a connected electric vehicle 40. The DC wallbox 10 is connected to the public low-voltage grid 30 via a separating element 11. An energy meter 31, designed as a bidirectional meter, measures the energy flow between the wallbox 10 and the public grid 30. A rectifier 12 with a power factor correction filter converts the mains alternating current into direct current. The direct current is converted into single-phase alternating current in a downstream inverter 13. A transformer 14 provides galvanic isolation. An active rectifier 15 is connected to the secondary side of the transformer 14 and generates a desired charging voltage for the energy storage device of the connected electric vehicle 30.The inverter 13, the transformer 14 and the active rectifier 15 together form a bidirectional DC / DC converter 21 with galvanic isolation.

[0038] Fig. 2 schematically shows an embodiment of the DC wallbox 10 according to the invention with three DC outputs 16, 18, 20 and three connected electric vehicles 40, 41, 42. As in the Fig. In the embodiment shown in Figure 1, a rectifier 12 with PFC converts the mains alternating current into direct current. The direct current is converted into single-phase alternating current in a downstream inverter 13. A transformer 14 provides galvanic isolation and is designed as an AC bus. In addition to the active rectifier 15 of the base module, two expansion modules 22, 23, each with an active rectifier 17, 19, are connected to the secondary side of the transformer. Each of the rectifiers 15, 17, 19 generates a desired charging voltage for the energy storage device of the electric vehicle 40, 41, 42 connected to it. The inverter 13, the AC bus 14, and the active rectifiers 15, 17, 19 together form a bidirectional DC / DC converter 21 with three outputs 16, 18, 20, which can provide different charging voltages. The outputs 16, 18, 20 are galvanically isolated from each other and from the input voltage.

[0039] This also enables charging processes in which the energy storage of one connected electric vehicle directly charges the energy storage of another connected vehicle, i.e. vehicle-to-vehicle charging processes. In Fig. 2 shows a DC charging connection 24 between the expansion modules 22 and 23. This makes it possible, for example, to charge the energy storage unit of the vehicle 41 directly with direct current from the energy storage unit of the vehicle 42.

[0040] Fig.Figure 3 shows a circuit diagram of a DC wallbox 10 according to the invention with three DC voltage outputs 16, 18, 20. The alternating current provided by the public low-voltage grid 30 is converted into direct current in the rectifier 12, converted into alternating current in the inverter 13, transferred to the secondary side of the AC bus via the transformer 14 in a galvanically isolated manner, and converted into charging voltages via the active DC-DC converters 15, 17, 19, which are provided at the charging outputs 16, 18, 20 to charge the connected energy storage devices 40, 41, 42. Likewise, the DC wallbox 10 can be used to extract energy from the connected energy storage devices 40, 41, 42, convert it into three-phase AC voltage, and feed it into the public low-voltage grid 30. List of reference symbols 10 DC wallbox 11 Separating element 12 Rectifier / PFC 13 inverters 14 Transformer / AC bus 15 active inverters 16 Charging port 17 active inverters 18 Charging port 19 active inverters 20 Charging port 21 active DC / DC converter 22 Expansion module 23 Expansion module 24 DC charging connection 30 Public low-voltage network 31 bidirectional energy meters 40 electric vehicles 41 electric vehicle 42 electric vehicles

Claims

[1] Bidirectional DC wallbox (10) with galvanic isolation, comprising a) a separating element (11) which is designed to reversibly connect and disconnect the DC wallbox (10) to an AC voltage network (30); b) a rectifier (12) with a power factor correction filter, which is arranged to rectify a three-phase alternating voltage; c) a DC-DC converter (21) with galvanic isolation, comprising i. an inverter (13); ii. an AC bus system (14) having a primary side and a galvanically isolated secondary side; iii. at least one active rectifier (15, 17, 19) configured to convert an alternating voltage into a direct voltage of a predetermined voltage level; iv. at least one charging output (16, 18, 20) for connection to a charging socket of an electric vehicle (40, 41, 42); wherein the output of the inverter (13) is connected to the primary side of the AC bus system (14) and the input of the at least one active rectifier (15, 17, 19) is connected to the secondary side of the AC bus system (14), and the at least one charging output (16, 18, 20) is connected to the output of the at least one active rectifier (15, 17, 19); and wherein the DC wallbox (10) comprises a base module having an isolating element (11); an AC / DC converter with PFC (12);and a DC / DC converter with galvanic isolation, which contains a DC / AC converter (13), an AC bus (14) and an AC / DC converter (15), and wherein at least one extension module (22, 23) is connected to the secondary side of the AC bus (14) of the base module, which extension module comprises an active rectifier (17, 19) and a charging output (18, 20) for connection to a charging socket of an electric vehicle (40, 41, 42), each extension module (22, 23) containing a control unit for regulating voltage and current.; [2] Bidirectional DC wallbox (10) according to claim 1, wherein the AC bus system (14) comprises a transformer. [3] Bidirectional DC wallbox (10) according to claim 1 or 2, wherein the DC-DC converter (21) with galvanic isolation comprises a plurality of active rectifiers (15, 17, 19), each having a charging output (16, 18, 20). [4] Bidirectional DC wallbox (10) according to claim 1, wherein the base module is designed for a connected load of 22 kW. [5] Bidirectional DC wallbox (10) according to one of the preceding claims, which comprises a communication unit configured for communication between the DC wallbox (10) and a mobile device of a user. [6] Bidirectional DC wallbox (10) according to claim 5, wherein the communication between the DC wallbox (10) and the mobile device takes place via cellular network or WLAN or via NFC or Bluetooth. [7] Method for operating a DC wallbox (10) according to one of the preceding claims, comprising a) connecting at least one energy storage device to a charging output (16, 18, 20) of the DC wallbox (10); b) connecting the DC wallbox (10) to an AC voltage network (30) by closing the separating element (11); and c) the transmission of electrical energy from the alternating voltage network (30) into the at least one connected energy storage device or from the at least one connected energy storage device into the alternating voltage network (30). [8] Method according to claim 7, wherein an output voltage at each charging output (16, 18, 20) of the DC wallbox (10) is individually adjustable. [9] Method according to claim 7 or 8, wherein the total connected load of the DC wallbox can be freely distributed to the individual charging outputs (16, 18, 20) of the DC wallbox (10). [10] Method according to one of claims 7 to 9, wherein control commands are transmitted from a user to the DC wallbox (10) via a communication unit of the DC wallbox (10) configured for communication between the DC wallbox (10) and a mobile device of the user.

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