WO2022207812A1

WO2022207812A1 - Charging station and method for operating a charging station

Info

Publication number: WO2022207812A1
Application number: PCT/EP2022/058615
Authority: WO
Inventors: Johannes Visosky
Original assignee: KEBA Energy Automation GmbH
Priority date: 2021-03-31
Filing date: 2022-03-31
Publication date: 2022-10-06
Also published as: EP4315580A1; DE102021108250A1

Abstract

Proposed is a charging station for charging and/or discharging an energy store of an electric vehicle with/of electric energy by means of a polyphase supply system that can be coupled to the charging station, the charging station comprising: an AC-to-DC converter which can be coupled to a number of phases of the supply system; a DC link which is connected downstream of the AC-to-DC converter; and a bidirectional DC-to-DC converter, which is connected downstream of the DC link, for converting a DC link input voltage into an output voltage, and vice versa, said DC-to-DC converter comprising a series circuit consisting of two half bridges with four semiconductor switches, each half bridge being connected between a DC link voltage bus having a DC link voltage on the input side and a medium-voltage bus having a symmetrical, in particular ground-symmetrical intermediate voltage, each center tap of the half bridge cooperating with a storage choke and a storage capacitor such that two bidirectional synchronous converters are connected in series, at least one snubber capacitor being connected to the center tap of each half bridge.

Description

CHARGING STATION AND METHOD OF OPERATING A

CHARGING STATION

TECHNICAL AREA

The invention relates to a charging station for charging and/or discharging an energy store of an electric vehicle with electrical energy using a multiphase network that can be coupled to the charging station, which has a bidirectional DC/DC converter for converting an input-side intermediate circuit voltage into an output voltage and vice versa. Furthermore, the invention relates to a method for operating such a charging station.

STATE OF THE ART

The present technical field relates to the charging of an energy store in an electric vehicle. For example, the applicant's European patent EP 2 882 607 B1 describes a charging station for electric vehicles, with at least one input interface for feeding electrical energy from a stationary power supply network into the charging station, with a connection socket for connecting a charging plug of an electric vehicle for the controlled delivery of electrical energy to the electric vehicle, with a plurality of electrotechnical components comprising an electronic control device for switching, measuring or monitoring the recorded and / or emitted electrical energy, and with a housing enclosing the electrotechnical African components.

Different charging methods are known for electric vehicles, for example there are fast charging methods in which the charging station provides the electric vehicle with direct voltage/current (DC), or alternatively alternating current charging - methods in which the electric vehicle has single-phase or multi-phase, in particular two-phase or three-phase, alternating current (AC) is made available, which the charging vehicle converts to using a built-in AC/DC converter Converts direct current for the energy storage device to be loaded. With the AC charging process, a charging logic in the vehicle or in the energy store controls the charging process.

Consequently, both an AC/DC converter and a DC/DO converter are used in a charging station suitable for DO charging.

A DC/DO converter, also referred to as a DC voltage converter, enables a DC voltage on the input side or a DC voltage fed into the intermediate circuit to be converted into an output voltage with a higher or lower or an inverted voltage level at the output U _out . The implementation takes place with the help of semiconductor switches and one or more energy stores such as inductances or capacitances or capacitors. DC voltage converters of this type are also referred to as DC choppers.

The DC/DC converter considered here works bidirectionally, ie energy can flow in both directions from input to output and/or from output to input. In particular, by selecting the duty cycle of the semiconductor switches, the flow of current can be routed both from the source to the load and from the load to the source. The level of the output voltage can be higher or lower than the respective input voltage depending on the selection of the input and the output. The DC/DC converter considered here is based on the principle of the synchronous converter, which is also referred to as a DC voltage transformer. By cyclically switching semiconductor switches, energy is stored in a magnetic field of a storage choke, which can be cyclically charged or discharged. In particular, MOSFETs, IGBTs or other high-voltage semiconductor switches are used as semiconductor switches. In principle, the DC/DC converter under consideration can be viewed as a combination of a step-up and a step-down converter. The level of the output voltage is determined by the switch-on and switch-off time of the semiconductor switch, and thus by the duty cycle. For example, DE 10 2018 206 388 A1 shows a DC/DC converter that includes an oscillating circuit and a transformer, with the transformer being supplied with alternating current by a half bridge, and a downstream rectifier providing a DO voltage on the output side. However, such a topology cannot be operated ^{bidirectionally} .

In addition, EP 3 255 772 A1 shows a DC/DO converter which also supplies current to a transformer by means of an inverter bridge, with the AO voltage on the secondary ^side being able to be converted back to DO via a half or full bridge, including a multi-stage bridge. Although such DC/DO converters can work bidirectionally, since they use controllable half or full bridges on both sides of the transformer, the energy flow takes place via an AC-operated transformer with corresponding energy losses and component _costs

Furthermore, WO ^2012/116953 A1 shows a DC/DC converter which is also based on a transformer-type coupling between the input and output sides, and uses an inverter bridge on the one hand and a three-point half bridge on the other to convert energy to be transmitted bidirectionally.

It is also known to use the principle of so-called zero voltage switching (ZVS) in a DC/DO conversion to determine the switching point of the ^{semiconductor} switches used, in order to achieve high efficiency by using resonant switching topologies. As a result, the drain-source voltage goes to zero before the MOSFET turns on, so that it can turn on when there is no voltage. So-called ^ZVS switching is also referred to as soft switching. With this Zero Voltage Switching concept, switching losses can be almost completely eliminated, especially when switching on. In addition, with a A reversing capacitor at the switching output of a semiconductor bridge, also known as a snubber capacitor, which significantly reduces turn-off losses.

The DC/DO converters known from the prior art either have poor efficiency because a ZVS concept cannot be implemented, or they have high material costs because an expensive and lossy transformer has to be used.

In addition, the known concepts do not allow an output potential to be made available that can be set symmetrically to ground, it being desirable to limit or minimize the voltage potential of the output potential tap DC+, DO to ground, in particular to provide an output voltage symmetrical to ground.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to create an improved charging station for charging and/or discharging an energy storage device of an electric vehicle, in particular to create a charging station with a DC/DC converter which has a high level of efficiency, carries out a DC voltage conversion bidirectionally and without a transformer and provides a symmetrical DC output voltage with respect to ground.

The task is solved by a charging station having the features of claim 1 and by a method having the features of claim 18 .

According to a first aspect, a charging station is proposed for charging and/or discharging an energy store of an electric vehicle with electrical energy using a multi-phase network that can be coupled to the charging station, the charging station having a number of phases (also denoted by LI, L2, L3 ) of the multiphase network that can be coupled AC/DC converter, an intermediate circuit downstream of the AC/DC converter and an intermediate circuit Circuit downstream bidirectional DC / DO converter for converting an input-side intermediate circuit voltage Uzk in an output voltage and vice versa. The DC/DC converter comprises a series connection of two half-bridges Hl, H2, each with two semiconductor switches TI, T2 and T3, T4, with each half-bridge Hl, H2 between an input-side intermediate voltage potential rail ZK+, ZK- with intermediate circuit voltage U _zk and a middle potential rail ZM is connected with symmetrical, particularly symmetrical to ground, voltage U _zk+, U _zk . Each center tap Ml, M2 of the half-bridge Hl, H2 is connected to its own storage choke LS+, LS- and a storage capacitor Cs, which is in particular common, so that two bidirectional synchronous converters are connected in series.

It is proposed that at least one reversing capacitor C _Z vs is connected to the center tap M1, M2 of each half-bridge H1, H2.

In other words, a DC/DC converter is proposed which, in principle, can be viewed as a series connection of two synchronous converters. To implement a ZVS concept, a reversing capacitor C _Z vs, C _Z vs+, C _Z v _S , C _Z vs++, Czvs+-, Czvs-+, Czvs- is connected to the center tap of each half-bridge, each of which defines a synchronous converter.

The input-side intermediate circuit voltage U _zk is provided in particular by the AC/DC converter, in particular provided symmetrically to ground. The AC/DC converter is preferably a bidirectional converter. The AC/DC converter is set up in particular for converting an AC voltage into a DC voltage and/or for converting a DC voltage into an AC voltage.

With the help of the series-connected half-bridges H1, H2, a ground-symmetrical output voltage can be provided with the two partial voltages DC+ and DC-. This has advantages in terms of electrical safety during operation and reduces the stress on the charging station's insulation. The reversing _capacitors ^CZvS connected to the center taps M1, M2 of the half-bridges H1, H2 can reduce a voltage ^rise speed du/dt and thus significantly improve the EMC behavior since _rapid voltage jumps are avoided. ^Overvoltages at the semiconductors can be significantly reduced since soft switching or ZVS switching is made possible. The permissible intermediate circuit voltage U _z k can be designed to be almost twice the blocking voltage of a semiconductor, so that for a high intermediate circuit voltage U _z k of 900-1000 V or higher, semiconductor switches with blocking voltages of 900 V or less, in particular less than or equal to 750 V or less can be used. This can be achieved in ^¬ example by SiC Mosfets. A blocking ^voltage down to 650 V is also possible. This makes it possible to cover large output voltage ranges U ₀ ut from ^below 200 V up to 920 V DC with correspondingly high input voltages U _z k . Since the permissible blocking voltage of Si MOSFETs is highly temperature-dependent, an output voltage U ₀ ut of 920 V can be reliably provided with SiC MOSFETs even at low temperatures.

By implementing the ZVS switching principle, reverse recovery effects can be avoided since no blocking voltage is switched on to a ^conductive diode. Due to a practically voltage-free switch-on, no reverse recovery losses occur and EMC problems resulting from a diode current tearing off can be prevented. As a result, there are practically no more turn-on losses, and turn-off losses can also be reduced. Ultimately, the proposed switching topology significantly increases the degree of effectiveness and ^improves the EMC behavior. ^Voltages that occur with respect to ground can be minimized and switching overvoltages can be limited. In particular, outputs of up to 22 kW can be provided. Compared to conventional DC/DC converters, a reduced effort with regard to the EMC output filter and a high saving in material can be achieved by doing without a converter transformer. the we- The degree of efficiency is improved in such a way that high energy savings can be achieved in the application over the service life.

The storage chokes can be designed separately and used magnetically uncoupled. In an advantageous embodiment, the two storage chokes LS+, LS- can be designed as a storage transformer T _s that are magnetically coupled. The two storage inductors LS+, LS- of each synchronous converter are arranged on a common magnetic core and magnetically coupled in the manner of a storage transformer Ts. As a result, cost savings can be achieved, and space can also be saved on the circuit board.

The charging station is in particular a transformerless charging station and has, for example, a housing, in particular a waterproof housing, with an interior space in which a plurality of electrical and/or electronic components and a connection socket connected to at least one of the components for connecting a charging plug for the Energy storage of the electric vehicle are arranged.

The charging station can also be referred to as a charging connection device. The charging station is designed in particular as a wall box. The charging station is suitable for charging or regenerating the energy store of an electric vehicle by electrically connecting the charging station to the energy store or the charging electronics of the electric vehicle via its connection socket and the charging plug of the electric vehicle. The charging station acts as a source of electrical energy for the electric vehicle, and the electrical energy can be transferred to an energy store in the electric vehicle by means of a connection socket and charging plug. The charging station can also be referred to as an intelligent charging station for electric vehicles.

Examples of the electrical and/or electronic components of the charging station include contactors, all-current-sensitive circuit breakers, DC, over and fault current monitoring device, relay, connection terminal, electronic circuits and a control device, for example comprising a printed circuit board, on which a plurality of electronic components for controlling and/or measuring and/or monitoring the energy states at the charging station or in the connected electric vehicle are arranged are.

The intermediate circuit downstream of the AC/DC converter includes, in particular, a number of intermediate circuit capacitors which are connected to an intermediate circuit center point.

The multiphase network is, for example, a multiphase subscriber network. The multi-phase network can also be a multi-phase power supply network. In particular, the polyphase network has a number of phases, for example LI, L2 and L3, and a neutral conductor (also denoted by N).

It should be noted that the “charging and/or discharging of an energy store” includes both supplying electrical energy and drawing electrical energy. This means that the energy store can act as a consumer or as a producer in the subscriber network.

In particular, a control unit is provided which can control individual or all elements and units of the charging station.

In an advantageous embodiment, a storage capacitor C _s between tween the output sides of the two storage inductors Ls ₊ , Ls for sharing the two series-connected bidirectional synchronous converters are switched ge. The storage capacitor C _s , which connects the output sides in the direction of the output potential taps DC+, DC- the two outputs of the storage chokes LS+, LS-, can stabilize the output voltage U ₀ ut and suppress switching frequency components. In an advantageous embodiment, the semiconductor switches TI, T2,

T3, T4 are designed as high-voltage MOSFET switching transistors with a low blocking voltage <900 V, in particular <750 V. This makes it possible to achieve an output voltage U _out of 920 V or more. Such semiconductors with a low blocking voltage, eg semiconductors from the INFINEON CoolMOS series, can be used inexpensively and with low switching losses.

Advantageously, in particular for the aforementioned embodiment, SiOFETs can be used as semiconductor switches, which combine a SiOJFET with a Si-MOSFET in a cascode circuit, for example the model UJ4C075018K4S from UnitedSiC. The SiO cascode offers the switching behavior of a self-locking MOSFET with the positive electrical properties of a silicon carbide transistor. Such semiconductor switches can advantageously be designed for blocking voltages of up to 750 V. In an advantageous embodiment, two corresponding semiconductor switches TI & T4 or T2 & T3 of the two half-bridges H1, H2 can be switched simultaneously, in particular with an identical switch-on delay. The switch-on delay is used to allow the voltage at the resonant capacitors to reverse. A symmetrical modulation of the control signals of the semiconductor switches TI & T4 or T2 & T3 can be achieved.

In an embodiment that goes further in this regard, it is possible for the semiconductor switches TI, T2, T3, T4 to be switchable with different switch-off delays for the controllable balancing of the medium voltage UZK+, UZK- of the intermediate circuit, so that Uzk+ and Uzk- can be balanced by ZM. Building on this, the symmetrical modulation of H1 and H2 can be used to achieve a controllable balancing of the output voltage _Uout at the two output potentials DC+, DO with respect to ZM and thus to ground. This makes it possible to achieve the balancing of the output voltage U _0ut pass. In this way, asymmetries in the component parameters, such as different switching speeds, can be compensated.

In an advantageous embodiment, the semiconductor switches TI, T2,

T3, T4 can be switched to generate a storage inductor current or storage transformer current with a ripple speed greater than an average value of the DO current, so that the inductor current has a zero crossing between two switching processes. In this way, ZVS activation can always be ensured. The ripple current amplitude is higher than the mean value of the choke current, so a choke current has always experienced a zero crossing between two switching processes, which is a prerequisite for ZVS switching on. In particular, a maximum and minimum value of the inductor current can be controlled by a current controller, for example a hysteresis current controller, which controls the switching of the semiconductor switches, so that the respective semiconductor switches are switched off when the maximum or minimum value is reached. The aim is to store enough energy in the storage choke to charge the reversing capacitors, which then results in the desired control of the mean value of the choke current.

Thus, the semiconductor switch pairs TI and T4 or T2 and T3 can be switched either with identical turn-on times or with different turn-on times, with turn-on losses being negligible. In an advantageous embodiment, the semiconductor switches TI, T2, T3, T4 in conjunction with the reversing capacitor C _Z vs, C _Z vs +, C _zvs -, C _zvs ++, C _zvs + -, C _zvs - +, C _zvs ZVS be switchable (zero voltage switching), in particular without voltage, can be switched on with almost no loss, and can be switched off with limited voltage rise speed with low losses. In this case, low-loss turn-off can result from limiting the rate at which the voltage rises, with the semiconductor switches, in particular switching transistors, turning off faster than a voltage can build up. By implementing the ZVS switching principle, the efficiency is significantly increased, thermal waste heat from the DC/DO converter is minimized and the service life is greatly extended, so that both energy giekosten minimized as well as the service life of the DC / DC converter can be significantly increased ^¬ Lich.

In an advantageous embodiment, at least one reversing capacitor Czvs+, ^Czvs per half-bridge Hl, H2 can be assigned, preferably one reversing capacitor Czvs++, Czvs+, C _zvs -+, C _zvs -- per semiconductor switch TI, T2, T3, T4 can be connected in parallel . Each semiconductor switch is therefore assigned a ^resonant capacitor, so that a switching ^overvoltage when switching off is minimized. The reversing capacitor is particularly relevant for switching off. Low-loss switching off can be achieved by additional reversing ^capacitors on the half- ^bridge outputs or in parallel with the semiconductor switches T1, T2, T3, T4. A balancing of the mean voltage U _z k+ , U _z k can nevertheless be achieved by means of a slightly different turn-off ^delay . Alternatively, a soft ^switching can already be achieved by a single capacitor C _zvs between the two half-bridge outputs M1, M2. Even if there is no reversing capacitor, the switching losses in ^ZVS switching can be smaller than in the case of hard switching, since the drain/source capacitance of the semiconductors can be used as a reversing ^capacitor . In an advantageous embodiment, a current controller Com can be included for detecting at least one inductor current ILS of at least one storage inductor Ls ₊ , Ls, in particular for detecting all inductor currents ILS+, ILS of the two storage inductors Ls ₊ , Ls. The current controller Com can be set up on the basis of the detected inductor current ILS switching signals ^ST1 , ST2, ST3, ST4 of the semiconductor switches TI, T2, T3, T4, in particular for controlling a maximum and a minimum value of the inductor current ILS ZU, testify ^¬ . Ripple current control is achieved by controlling the maximum value and the minimum value of the inductor current or currents, as a result of which the mean value of the ^inductor current can also be adjusted. As a rule, the switching signals ST1 & ST4 as well as ST2 & ST3 are synchronous with one another, which means that a common-mode voltage at the output can be avoided, taking into account the ZVS requirements for the switching processes. The switch-on delay ^¬ serves to reduce the voltage across the reversing capacitors, ie to let the ZVS capacitors swing around. The current controller thus works as a hysteresis controller to determine the switch-on delay. A slight variation of a switch-off delay of the individual switching signals can also be used to achieve active balancing of the mean voltage U _{zk+ ,} U _zk . The switching signals can be generated on the basis of the inductor current ILS at least one, preferably both storage inductors Ls ₊ , Ls, so that the output voltage U _out can be made available in a regulated manner. If an inductor current exceeds a maximum value or falls below a minimum value, the current controller, which is preferably designed as a hysteresis controller, can cause corresponding semiconductor switches to be switched on or off. Its switching hysteresis is thus defined by a maximum and minimum value of the inductor current, which should ensure at least one zero crossing of the inductor current per switching period.

The current regulator Com can advantageously detect all inductor currents ILS+, ILS of the storage inductors Ls _+, Ls separately, as a result of which the switching pulses ST1, ST2, ST3, ST4 can be set as a function of the inductor currents ILS+, ILS. In addition, a differential current error, in particular a power supply error, e.g. a leakage current, can be advantageously detected by forming the current difference between the inductor currents ILS+ILS, at least when a predeterminable current difference amount is exceeded, after which the current regulator Com or a higher-level control unit, for example, suppress switching pulses and thus the DC voltage converter 20 can switch off. Alternatively or additionally, other switch-off devices, in particular contactors, can be used for switching off if a differential current error, in particular a leakage current, is detected by forming a current difference between the inductor currents ILS+ILS, at least when a predeterminable current difference amount is exceeded.

As a rule, the storage inductors Ls ₊ , L s can be designed separately and structurally separate, and not magnetically coupled. The storage inductors Ls ₊ , L s− are preferably designed with the same inductance. By virtue of a further development of the invention, the storage transformer Ts can have two include symmetrical windings of the two storage inductors Ls ₊ , L s with the same number of turns on a common magnetic core. In high-power applications, the storage transformer Ts can preferably have a total inductance of 20 mH or less and/or a total number of turns of nine turns or less. In an application with a low power requirement, for example a charging station with a low power of less than 10 kW, higher total inductances >20 mH and larger numbers of turns can also be used.

With a large ripple current, which produces at least zero crossings in the inductor current, the storage transformer Ts can have a low inductance and few turns. This results in low copper losses and negligible parasitic winding capacitances. In turn, low winding capacitances are favorable with regard to the EMC behavior; in particular, undesired capacitive leakage currents in the outputs can be avoided and a common-mode filter on the output side can be omitted or simply configured. With a conventional design of the storage transformer Ts for an effective ripple current value of ten percent of the DC current, on the other hand, the total inductance would be practically nine times that of up to 180 mH, i.e. up to 90 mH per storage choke Ls ₊ , Ls , and three times the number of turns, up to 27 turns or more.

Assuming the same winding window cross sections with the same fill factor, the copper resistance would be nine times higher. This shows that when designed for a high ripple current with zero crossings, the copper losses in the choke can be massively reduced despite the approx. 30% higher rms choke current value, although these savings are not quite as dramatic in reality, since the influence of a skin effect at high Switching frequencies is not taken into account, which is not negligible with a high ripple current. In any case, the core losses are significantly lower than the copper losses and these can be significantly reduced with simple storage choke configurations. In particular, when stacked ferrite cores, the required internal cross-sections are determined by the copper cross-section required for the winding.

Compared to the hard-switching operation of the DC/DO converters known from the prior art, a higher ripple current for the intermediate ^circuit capacitors CZK or output capacitors, in particular ^Cs , presents no problems, since low-loss film ^capacitors can be used. Low-loss ceramic capacitors in SMD design can preferably be used for the resonant capacitors C _Z vs. The ripple current load of the intermediate circuit is only slightly higher than in hard ^- switching operation.

Both the maximum and minimum value of the inductor current, and thus the inductor current ^mean value and the ripple current amplitude can be controlled by the current ^controller Coni, in particular in such a way that the semiconductor switches are switched in such a way that zero crossings occur in the inductor current. The mean value of the inductor current ILS determines the active energy transfer and the energy flow direction. The ripple current amplitude determines the reactive energy circulating in the DC/DC converter for the ZVS switching, so much energy remaining stored in the inductor that the reversing capacitors ^can be recharged.

In an advantageous development of the invention, a filter stage FIS can be connected downstream between the storage capacitor C _s and the output potential tap DC+, ^DC- on the output side. In particular, this filter stage FIS can have at least one current-compensated choke Lis and a capacitor bridge HC with two series-connected medium-voltage filter capacitors Cis ₊ ,

Cis include that can filter out high-frequency voltage components of the output voltage U ₀ ut. A grounding filter capacitor CISG can preferably be connected to a ground potential at the center tap of the capacitor bridge HC, in order in turn to achieve high-frequency grounding of the DC output. Nevertheless, a filter capacitor can be placed between DC+ or DC- and earth be connected, and another filter capacitor between DC+ and DO be connected. However, a different filter capacitor network can also be used.

In an advantageous embodiment, the intermediate circuit voltage UZK can be 950 V or higher in order to set a range of the output voltage U _out of at least between 200 V and 920 V.

In an advantageous embodiment of the invention, each semiconductor switch TI, T2, T3, T4 include a parallel connection of two or more switching transistors. With this parallel connection, the degree of efficiency of the semiconductors can be increased within certain limits and higher output powers can be made available. Due to the Z VS switching behavior, the semiconductor switches TI, T2, T3, T4 only have conduction losses and no turn-on losses and low turn-off losses, with the conduction losses being further minimized by connecting semiconductors in parallel and efficiency being increased.

According to a second aspect, a method for operating a charging station for charging and/or discharging an energy store of an electric vehicle with electrical energy using a multi-phase network that can be coupled to the charging station is proposed, with the charging station having a number of phases of the multi-phase network that can be coupled AC/DC converter and an intermediate circuit downstream of the AC/DC converter. The procedure includes^

To convert an input-side intermediate circuit voltage Uzk into an output voltage Uout or vice versa by means of a bidirectional DC/DC converter connected downstream of the intermediate circuit, comprising a series connection of two half-bridges Hl, H2 with four semiconductor switches, with each half-bridge Hl, H2 between an input-side intermediate circuit potential rail ZK+, ZK- with intermediate circuit voltage Uzk and a medium-potential busbar ZM with symmetrical, in particular ground-symmetrical, medium voltage UZK+, UZK- is connected, and each center tap Ml, M2 of the half-bridge Hl, H2 interacts with a storage inductor Ls+, Ls- and a storage capacitor CS, so that two bidirectional synchronous converters are connected in series, with the center tap Ml, M2 of each half-bridge Hl , H2 at least one resonant capacitor CZVS, CZVS+, CZVS-, CZVS++, CZVS+-, CZVS-+, czvs- is connected.

This method has the same advantages as explained for the charging station according to the first aspect. The embodiments described for the proposed charging station apply accordingly to the proposed method. Furthermore, the definitions and explanations for the charging station also apply accordingly to the proposed method.

As used herein, "a" is not necessarily to be construed as being limited to exactly one element. Rather, a plurality of elements, such as two, three or more, can also be provided. Any other count word used here should also not be understood to mean that there is a restriction to precisely the stated number of elements. Rather, numerical deviations upwards and downwards are possible, unless otherwise stated.

Further possible implementations of the invention also include combinations of features or embodiments described above or below with regard to the exemplary embodiments that are not explicitly mentioned. The person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

Further advantageous refinements and aspects of the invention are the subject matter of the subclaims and of the exemplary embodiments of the invention described below. The invention is explained in more detail below on the basis of preferred embodiments with reference to the enclosed figures. Fig. 1 shows schematically an arrangement with a first embodiment of a charging station and an electric vehicle;

2 shows a schematic circuit diagram of a second embodiment of a charging station for charging and/or discharging an energy store of an electric vehicle;

3 shows the basic configuration of a ZVS switching concept of a half-bridge;

4a, 4b show a first and second exemplary embodiment of a DC/DC converter;

5a, 5b further exemplary embodiments of DC/DC converters;

6 shows a further exemplary embodiment of a DC/DC converter; and

Fig. 7 shows a schematic flowchart of a method for

Operating a charging station for charging and/or discharging an energy store of an electric vehicle.

In the figures, elements that are the same or have the same function have been provided with the same reference symbols, unless otherwise stated.

Fig. 1 schematically shows an arrangement with a first embodiment of a charging station 1 and an electrical energy store 2 of an electric vehicle 3.

In the example of FIG. 1, a multi-phase subscriber network 4 is connected to a multi-phase power supply network 7 by means of a network connection point 6 . The multi-phase subscriber network 4 has in particular a number of phases, for example LI, L2 and L3, and a neutral conductor N. It is in this example, without loss of generality, are three-phase power grids. The electric vehicle 2 is coupled to the charging station 1 by means of a charging cable 5 which is connected to a connection socket (not shown) of the charging station 1 .

The charging station 1 can have a number of electrical and/or electronic components (not shown in FIG. 1, see for example FIG. 2) and is for charging and/or discharging the energy store 2 of the electric vehicle 3 with electrical energy using the the charging station 1 coupled multi-phase subscriber network 4 set up.

In addition, the charging station 1 preferably comprises a communication module (not shown). The communication module is set up to negotiate a charging plan with charging electronics of the energy store 2 coupled to the charging station 1 .

Negotiation takes place, for example, as described in ISO 15118. For example, the charging electronics of the energy storage device 2 requests a certain charging capacity via the communication module at the charging station 1 and the charging station 1 determines whether the requested charging capacity can be provided. A current state of the subscriber network 4 and/or the power supply network 7 is taken into account in particular. If the requested charging power cannot be provided, the charging station 1 can make a "counterproposal" via the communication module, which can be accepted by the charging electronics of the energy storage device 2, or the charging electronics can make its own request again. In this way, the charging station 1 and the charging electronics of the energy store 2 communicate until the charging plan has been negotiated. Negotiating the charging plan can be part of the pairing process when an energy storage device 2 is newly connected to the charging station 1 .

Fig. 2 shows a schematic circuit diagram of a second embodiment of a charging station 1 for charging and discharging an energy store 2 of an electric vehicle 3. The second embodiment of Fig. 2 includes all features of the first embodiment of Fig. 1.

The charging station 1 of Fig. 2 has three connection terminals 101, 102, 103 for the three phases LI, L2, L3 of the multi-phase network 4. In particular, the charging station 1 also has another connection terminal (not shown) for the neutral conductor N.

According to FIG. 2, an EMC filter device 200 is connected downstream of the connection terminals 101, 102, 103. Furthermore, the charging station 1 of FIG. 2 comprises an LCL filter device 300 connected downstream of the EMC filter device 200, an AC/DC converter 400, an intermediate circuit 500, a bidirectional DC/DC converter 600 and an intermediate output circuit 700, to which a negative output potential ^tap 701 and a positive output potential tap 702 are connected.

Furthermore, FIG. 3 shows the basic configuration of a ZVS switching concept of a half-bridge and FIGS. 4 to 6 show various exemplary embodiments for the bidirectional DC/DC converter 600 shown in FIG.

In other words, the bidirectional DC/DC converter 600 of Fig. 2 can be replaced by the DC/DC converter 10 of Fig. 4a, by the DC/DC converter 20 of Fig. 4b, by the DC/DC converter 30 of FIG. 5a, by the DC/DC converter 40 of FIG. 5b or by the DC/DC converter 50 of FIG.

As explained above, FIG. 3 shows a configuration 14 of a zero-voltage switching concept of a half-bridge, comprising two semiconductor switches TI, T2. The ZVS switching topology 14 of FIG. 3 represents part of the first specific embodiment of the DC/DC converter 10 shown in ^FIG tial reload so that the other semiconductor switch can turn on without voltage and loss. This means that it can be switched on practically without voltage and with low switched, and switched off with a reduced voltage rise. The efficiency of a DC/ ^DO voltage converter plays a decisive role, particularly in the case of power supplies or charging stations in the field of electromobility. By ^ZVS switching the semiconductor switches, the switching losses can practically be set to zero, and ^unwanted thermal heating can be minimized.

4a shows a first exemplary embodiment 10 of a bidirectional DC/DO converter, which converts an input voltage UZK of a symmetrical intermediate circuit ZK with the two intermediate circuit medium voltages UZK+, UZK and an intermediate circuit medium potential rail ZM into an output voltage U ^0ut at the output _{potential taps} DC+ , DO converts. For this purpose, a half-bridge H1 or H2 is connected between the intermediate circuit potential rails ZK+, ^ZK- and the middle potential rail ZM. Each half-bridge comprises two semiconductor switches, the half-bridge H1 the semiconductor switches TI and T2, and the half-bridge H2 the semiconductor switches T3 and T4.

Two stabilization capacitors CZK+ or ^CZK- are connected between the intermediate circuit potential rail ZK+ or ^ZK- and the medium potential rail ZM for the purpose of stabilizing the intermediate circuit potential and for supporting the intermediate circuit voltage ^UZK . Two symmetrical storage chokes Ls ₊ and Ls are connected to the respective center taps ^M1 , M2 of the half-bridges H1 and H2, and are magnetically coupled to one another as a storage transformer Ts via a magnetic core. Alternatively, two individual inductors that are not ^magnetically coupled can also be used. At the input of the storage transformer Ts, two resonant capacitors ^Czvs ₊ and Czvs are connected with respect to the mid-potential rail ZM in order to enable ZVS switching or soft switching of the semiconductor switch of the three-point bridge with the two half-bridges H1 and H2. A storage capacitor ^Cs is connected in parallel at the output of the transformer Ts and stabilizes the output voltage U _out at the two output ^potential taps DC+ and DO. By combining the two storage inductors ^¬ Ls _+, Ls in a storage transformer Ts as a storage inductor with shared Winding and the circuit of reversing capacitors Czvs at the center ^¬ taps Ml, M2 of the two half-bridges Hl, H2 is a significant improvement ^¬ tion of the efficiency and a lower emission of interference allows, with high power over 20 kW can be transmitted.

The current through a storage choke Ls ₊ and/or Ls is recorded as the choke current ILS by a current controller Coni. The duty cycle of the semiconductor switches TI, T2, T3 and T4 is controlled on the basis of the inductor current ILS, which has a ripple current with an amplitude higher than a mean value of the inductor current for generating zero crossings. For this purpose, the current controller Coni generates four switching pulses ST1, ST2, ST3, ST4 as the gate voltage of the semiconductor switches TI, T2, T3, T4. These are set in such a way that respective ^{semiconductor} switches are switched off when a maximum or minimum value is reached, with sufficient ^energy being stored in the storage inductor in order to enable the ^resonant capacitors to be recharged.

As a rule, two semiconductor switches TI & T4 and T2 & T3 are switched simultaneously, with the semiconductor switches TI & T4 being switched in push-pull to T2 & T3 in order to avoid short circuits. Identi ^¬ cal switch-on delays are assumed. The switch-on ^delay serves to allow the voltage at the reversing capacitors to resonate. Slightly different turn-off delays can also be used to actively balance the output voltage _Uout , in particular to ensure an output Uout balanced to ground. As a rule, the current regulation is stored as a software method in the current ^regulator Coni. In order to achieve very fast controller behavior, the current controller Coni can be designed at least partially, in particular completely, in hardware. The current regulator Coni can also have an I/O interface ^RΊ /0 to a higher-level processor controller, for example charging electronics for an electrochemical ^store . A second exemplary embodiment 20 is shown in FIG. 4b, which is essentially the same as the DC/DC converter 10 of FIG. 4a. Deviating from this, the two storage chokes Ls _+, Ls are arranged with the same inductance and magnetically independently and physically separate from one another, and are not combined in a storage transformer Ts. In addition, the current controller Com records both inductor currents ILS+, ILS- of the storage inductors Ls _+, Ls separately. If a residual current not equal to zero occurs, the DC-DC converter 20 can be switched off.

FIGS. 5a, 5b show two further exemplary embodiments 30, 40 of DC/DC converters according to the invention, which essentially correspond to the configuration of FIG. Deviating from FIG. 4, in FIG. 5a the DC voltage converter 30 is connected to a common reversing capacitor Czvs at the center taps M1, M2 of the two half-bridges H1, H2. Analogous to the exemplary embodiment of the DC-DC converter 20, both inductor currents ILS+, ILS are detected by the current regulator Com, so that what has been said here also applies to this. However, it can also be sufficient to record only one of the two inductor currents ILS+ or ILS for controlling the ripple current.

In FIG. 5b, each semiconductor switch T1, T2, T3, T4 of the DC voltage converter 40 has a resonant capacitor Czvs++, Czvs+−, Czvs+, Czvs connected in parallel. The inductor current is detected analogously to the embodiment of the DC-DC converter 10.

The different configurations of the reversing capacitor Czvs either minimize the number of components or the switching overvoltages.

Finally, FIG. 6 shows a further exemplary embodiment 50 of a DC/DC converter, which likewise essentially corresponds to the exemplary embodiment 10 in FIG. Analogous to the exemplary embodiment of the DC-DC converters 20 and 30, either one of the two or both inductor currents ILS+, ILS is detected by the current regulator Com, so that what was said in this regard also applies here is applicable. A filter stage FIS is interposed on the storage capacitor Cs before the output potential tap DC+, DC-. The filter stage FIS includes a current-compensated choke ^Lis . A half-bridge made of two medium-voltage filter capacitors Cis _+, Cis-, which is referred to as a capacitor bridge HC, is connected in parallel with the output potential taps DC+, DC-. At the center tap of the capacitor bridge HC, a further grounding filter capacitor ^CISG is connected to ground, in order to allow common-mode currents to be discharged. The filter stage FIS enables radio interference suppression and an improvement in the EMC robustness of the DC/DC converter 50. There are several ways of constructing this filter, a capacitor Cis and two capacitors CISG can also be provided, with one capacitor CISG from DC+ to ground and/or is connected from DC- to ground.

7 also shows a schematic flowchart of a method for operating a charging station 1 for charging and/or discharging an energy store ^¬ chers 2 of an electric vehicle 3 with electrical energy by means of a multi-phase network 4 that can be coupled to the charging station 1. The charging station 1 is at ^¬ for example formed as explained in the preceding figures.

In step S1, the charging station 1 is coupled to the multi-phase network 4 and to the energy store 2 of the electric vehicle 3.

In step S2, an input-side intermediate circuit voltage ^Uzk is converted into an output voltage ( ^Uout ) or vice versa by means of a bidirectional DC/DC converter 600, 10, 20, 30, 40, 50 connected downstream of the intermediate circuit 500.

Although the present invention has been described on the basis of embodiments, it can be modified in many ways. REFERENCE LIST

1 charging station

2 energy storage

3 electric vehicle

4 multi-phase subscriber network

5 charging cables

6 grid connection point 7 multiphase energy supply network 10 bidirectional DC/DO converter 12 bidirectional synchronous converter 14 ZVS switching topology 20 bidirectional DC/DO converter 30 bidirectional DODO converter 40 bidirectional DODO converter 50 bidirectional DODO converter 101 connection terminal 102 connection terminal 103 connection terminal 200 EMC filter device 300 LCL filter device -Converter 500 intermediate circuit 600 DODO converter

700 output intermediate circuit

701 Starting spot ential pick-up

702 Starting spot ential pick-up

UZK intermediate circuit voltage

UZK+, UZK- intermediate circuit medium voltage

Uout output voltage

ZK ₊ , ZK- intermediate circuit potential bar ZM intermediate circuit medium potential busbar

Hl, H2 half bridge

Ml, M2 center tap of the half bridge

TI, T2, T3, T4 semiconductor switches

ST1, ST2, ST3, ST4 switching signal

CZK+, CZK- intermediate circuit capacitor Czvs resonant capacitor

Czvs+, Czvs- medium voltage resonant capacitor

Czvs++, Czvs+-, Czvs-+, Czvs- Switch related reversing capacitor

Cs storage capacitor

L _s storage choke

L _s+, L _s+ Symmetrical storage choke

T _s memory transform ator

DC+, DC- Output potential tap

Con current regulator

FIS filter stage

ILS inductor current

HC capacitor bridge

Cis+, Cis- medium voltage filter capacitor

ClSG grounding filter capacitor

Lis common mode choke

P-I/O I/O interface for processor control

LI phase

L2 phase

L3 phase

N neutral conductor

Sl, S2 V experienced steps

Claims

PATENT CLAIMS

1. Charging station (l) for charging and/or discharging an energy store (2) of an electric vehicle (3) with electrical energy by means of a ^multiphase network (4) that can be coupled to the charging station (l), with: one having a number of phases (LI, L2, L3) of the multiphase network (4) that can be coupled AC/DC converter (400), an intermediate circuit (500) connected downstream of the AC/DC converter (400), and a bidirectional DC/DC converter connected downstream of the intermediate circuit (500). DC converter (600, 10, 20, 30, 40, 50) for converting an input-side intermediate circuit voltage ( ^Uzk ) into an output voltage ( ^Uout ) and vice versa, comprising a series connection of two half-bridges (Hl, H2) with four semiconductor switches (TI, T2, T3, T4), each half-bridge (Hl, H2) between an input-side intermediate circuit potential rail (ZK+, ZK-) with intermediate circuit voltage (Uzk) and a medium potential rail (ZM) with symmetrical, in particular ^¬ ground-symmetrical , medium voltage (UZK+, UZK-) is connected, and where at each center tap (Ml, M2) of the half-bridge (Hl, H2) with a storage ^¬ choke (Ls +, LS-) and a storage capacitor (CS) interacts, so that two bidirectional synchronous converters are connected in series, with the center ^¬ tap ( Ml, M2) of each half-bridge (Hl, H2) at least one Umschwingkondensa ^¬ tor (CZVS, CZVS +, CZVS, CZVS ++, CZVS +, CZVS +, CZVS-) is connected.

2. Charging station according to claim 1, characterized in that the two storage chokes (Ls +, Ls -) are designed as a storage transformer (TS) like ^¬ magnetically coupled.

3. Charging station according to claim 1 or 2, characterized that a storage capacitor (CS) is connected between the output sides of the two storage chokes (Ls+, Ls-) for sharing the two series-connected bidirectional synchronous converters.

4. Charging station according to one of the preceding claims, characterized in that the semiconductor switches (TI, T2, T3, T4) are designed as high-voltage MOSFET switching transistors with a low reverse voltage of less than or equal to 900 V, in particular less than or equal to 750V.

5. Charging station according to one of the preceding claims, characterized in that the semiconductor switches are SiC-FETs which combine a SiC-JFET with a Si-MOSFET in a cascode circuit.

6. Charging station according to one of the preceding claims, characterized in that two corresponding semiconductor switches (TI & T4 and T2 & T3) of the two half-bridges (Hl, H2) can be switched simultaneously, in particular can be switched with an identical switch-on delay.

7. Charging station according to one of the preceding claims, characterized in that the semiconductor switches (TI, T2, T3, T4) can be switched with different switch-off delays for the controllable balancing of the intermediate circuit voltage (UZK+, UZK-) and/or the output voltage (Uout).

8. Charging station according to one of the preceding claims, characterized in that each semiconductor switch (TI, T2, T3, T4) comprises a parallel connection of two or more switching transistors.

9. Charging station according to one of the preceding claims, characterized in that the semiconductor switches (TI, T2, T3, T4) can be switched to generate a ripple current with a ripple amplitude greater than an average value of the inductor current, so that the inductor current has a zero crossing between two switching processes having.

10. Charging station according to one of the preceding claims, characterized in that the semiconductor switches (TI, T2, T3, T4) in interaction with the To ^¬ oscillating capacitor (CZVS, CZVS +, CZVS-, CZVS ++, CZVS +, CZVS +, CZVS- ) ZVS-switchable (zero voltage switching), in particular without voltage, can be switched on with almost no loss, and can be switched off with a limited voltage ^rise speed with low losses.

11. Charging station according to one of the preceding claims, characterized in that at least one reversing capacitor (CZVS+, CZVS-) is assigned per half-bridge (H1, H2), preferably one reversing capacitor (CZVS++, CZVS+-, CZVS-+, CZVS--) per Semiconductor switches (TI, T2, T3, T4) is connected in parallel ge ^¬ .

12. Charging station according to one of the preceding claims, characterized in that a current controller (Conl) for detecting at least one inductor current (ILS, ILS+, ILS-) comprises at least one storage inductor (Ls+, ^Ls- ), which is set up Based on the inductor current (ILS, ILS+, ^ILS- ) switching signals (ST1, ST2, ST3, ST4) of the semiconductor switches (TI, T2, T3, T4), in particular for controlling a maximum and a minimum value of the inductor current (ILS, ILS+ , ILS-), to generate.

13. Charging station according to one of the preceding claims, characterized in that the storage transformer (TS) comprises two symmetrical windings of the two storage chokes (Ls+, Ls-) with the same number of turns on a common magnetic core, with the storage transformer (TS) preferably having a self-inductance of 20 mH or less and/or a total number of turns of nine Has turns or less.

14. Charging station according to one of the preceding claims, characterized in that a filter stage (FIS) is connected downstream between the storage capacitor (CS) and an output potential tap (DC+, DO).

15. Charging station according to Claim 14, characterized in that the filter stage (FIS) comprises at least one current-compensated choke (LIS) and a capacitor bridge (HC) with two medium-voltage filter capacitors (CIS+, CIS-) connected in series, with the capacitor bridge (HC), a grounding filter capacitor (CISG) is connected to ground potential, or one output potential tap (DC+, DC-) on the output side is connected to ground potential via a filter capacitor, and another filter capacitor between the output potential taps on the output side (DC+ , DC-) is switched.

16. Charging station according to one of the preceding claims, characterized in that the intermediate circuit voltage (UZK) is 950 V or higher, and that a range of the output voltage (Uout) can be set at least between 200 V and 920 V.

17. Charging station according to one of the preceding claims, characterized in that the charging station (l) is a transformerless charging station.

18. A method for operating a charging station (l) for charging and/or ^discharging an energy store (2) of an electric vehicle (3) with electrical energy using a ^multiphase network (4) that can be coupled to the charging station (l), the Charging station (l) has an AC/DC converter (400) that can be coupled to a number of phases (LI, L2, L3) of the multiphase network (4) and an intermediate circuit (500) connected downstream of the AC/DC converter (400), With:

Converting an input-side intermediate circuit voltage (Uzk) into an output voltage ( ^Uout ) or vice versa by means of a bidirectional DC/DC converter (600, 10, 20, 30, 40, 50) connected downstream of the intermediate circuit (500), comprising a series connection of two half-bridges ( Hl, H2) with four semiconductor ^¬ switches (TI, T2, T3, T4), each half-bridge (Hl, H2) between a ^¬ output-side intermediate circuit potential rail (ZK +, ZK-) with intermediate circuit - voltage (Uzk) and a Medium potential rail (ZM) is connected with symmetrical, in particular ground-symmetrical, medium voltage (UZK+, UZK-), and each center tap (Ml, M2) of the half-bridge (Hl, H2) with a storage choke (Ls+, ^LS- ) and a storage capacitor (CS), so that two bidirectional synchronous converters are connected in series, with at least one reversing capacitor (CZVS, ^CZVS +, CZVS-, CZVS++, CZVS+ -, CZVS-+, CZVS-) is connected.