CN114516276A

CN114516276A - Method and apparatus for charging electric vehicles directly on a DC power supply

Info

Publication number: CN114516276A
Application number: CN202111361717.5A
Authority: CN
Inventors: D·斯贝塞; T·菲森迈尔; F·迈尔
Original assignee: Dr Ing HCF Porsche AG
Current assignee: Dr Ing HCF Porsche AG
Priority date: 2020-11-20
Filing date: 2021-11-17
Publication date: 2022-05-20
Also published as: GB202116723D0; GB2602198B; GB2602198A; DE102020130754A1; KR20220069832A

Abstract

A method for charging an electric vehicle (9) directly on a DC power supply (1) is provided, having the steps of: providing a direct current on an energy connection (4) by means of the DC power supply (1); charging the electric vehicle (9) at the energy connection (4); wherein during a charging process an inverter (3) arranged between the DC power source (1) and the energy connection (4) is bypassed such that a direct current provided by the DC power source (1) is provided at the energy connection (4). In addition, a corresponding charging device is also provided.

Description

Method and apparatus for charging electric vehicles directly on a DC power supply

Technical Field

The invention relates to a method and a device for charging an electric vehicle directly on a DC power supply, in particular on a DC power supply.

Background

In buildings equipped with photovoltaic installations, as a rule, the direct voltage applied to the output of the solar modules (photovoltaic modules) is first regulated to a specific direct voltage value by means of a DC/DC converter and is subsequently fed to a DC/AC converter, which converts the regulated direct voltage into an alternating voltage. The alternating current thus generated can either be used directly in the building, for example for charging an electric vehicle, or can be fed to the power grid for compensation. When charging an electric vehicle provided at a charging point in a building, an AC/DC conversion of the supplied alternating voltage is first effected on the vehicle side and then converted by means of a DC/DC converter into a suitable direct voltage, with which the traction battery is charged. In the same way, in addition to or instead of a DC photovoltaic installation, a thermoelectric generator may be used, for example.

Although this method is particularly attractive to private homes and is capable of charging electric vehicles using the premises' own photovoltaic facility, a problem here arises in that there is a loss of each current or voltage conversion and thus a reduction in efficiency when charging electric vehicles as outlined above using the electricity generated by the photovoltaic facility.

DE 102015219665 a1 discloses a method for charging a battery of a motor vehicle, in which charging energy is fed from a photovoltaic or thermoelectric device via a charging device to the battery of the motor vehicle. In order to store charging energy temporarily in the charging device, an energy store is used, wherein the battery is charged with at least a partial amount of charging energy when a charge state variable is detected, which describes the amount of charging energy temporarily stored in the energy store, exceeding a threshold value.

Disclosure of Invention

The object of the invention may be to more efficiently design the charging process of an electric vehicle using solar energy.

This object is achieved by means of a method according to the invention for charging an electric vehicle directly on a DC power supply and a corresponding device. Other embodiments are defined in additional examples below.

In accordance with the present invention, a method for charging an electric vehicle directly on a DC power source is provided. The method comprises the following steps: the direct current is provided at the energy connection by means of a DC power supply. In this case, the fundamental possibility of supplying a direct current via a DC power supply is primarily referred to, the direct current being supplied at the energy terminals. The energy connection may be, for example, a charging point installed in or on the building, for example a charger provided specifically for charging electric vehicles, which charger is coupled to the building grid, to which the DC power supply is also coupled.

DC power sources are devices that can natively provide direct current or direct voltage based on energy conversion (e.g., photovoltaic, electrochemical, or thermoelectric energy conversion). Thus, the DC power source or DC voltage source is for example a photovoltaic installation or a photovoltaic grid (in which a plurality of photovoltaic installations are connected together), or a thermoelectric generator. A direct voltage converter may be connected downstream of the DC power supply or integrated therein as a module, which direct voltage converter may be used for stabilizing the voltage and for adapting the voltage level.

The method according to the invention further comprises: the electric vehicle is charged at the energy connection. For this purpose, the vehicle is connected to the energy connection by means of a suitable charging cable in a manner known from the prior art and is charged with the current supplied at the energy connection. A charging cable provided on a charger, for example on a wall box charging station, can be used for the charging process.

The charging method according to the invention is characterized in that during the charging process an inverter arranged between the DC power source and the energy connection is bypassed, so that a direct current provided by the DC power source is provided at the energy connection. It is to be emphasized here that the direct current provided by the DC power source is provided at the energy connection without prior current conversion by the inverter. An inverter is a building-side DC/AC converter which has already been mentioned in the opening paragraph and which converts a direct current provided by a DC power supply into an alternating current so that the alternating current can be fed into the building grid. In order to bypass the inverter on the building side for the charging process, a switch, for example a relay, can be used, by means of which the inverter can be bypassed, i.e. for example a conductive path between the output of the DC power supply and an energy connection (for example an interface of a corresponding charger) can be activated by means of the switch. The term "bypassing the inverter" can also refer to a pass-through of the inverter, in which the switches arranged therein are continuously switched on and are not operated in a clocked manner, so that the input current of the inverter is provided as the output current without conversion.

The direct charging according to the invention is therefore a charging process with an optimized charging topology which enables charging of the traction battery of an electric vehicle while bypassing at least one current or voltage converter (AC/DC, DC/AC or DC/DC) which is usually arranged on the building side in the current path between the DC power supply and the energy terminals. The bypassed current converter can be in particular the inverter mentioned immediately above, which converts a direct current provided by a DC power source into an alternating current, so that the alternating current is fed into a power grid, for example a building grid, to which the DC power source (for example a photovoltaic installation) is connected and operates. Preferably, during the direct charging process, a plurality of current or voltage converters (on the vehicle side as well as on the building side) can be bypassed, wherein the building side represents the part of the charging infrastructure that is outside the vehicle. In particular, during the charging method according to the invention, it is additionally possible to bypass a direct-current voltage converter which is arranged on the building side and is connected downstream of the DC power supply.

According to a further embodiment of the charging method according to the invention, a rectifier in the charging line on the vehicle side can be bypassed during the charging process of the electric vehicle. The rectifier is generally an on-vehicle rectifier provided in a charging line on the vehicle side, and converts an alternating current into a direct current at the time of alternating current charging, and charges the traction battery with the direct current. Furthermore, a dc voltage Converter (e.g., Buck/Boost Converter) is usually connected between the rectifier and the traction battery. By bypassing the vehicle-side rectifier, the direct current provided at the energy connection is converted only by the vehicle-side direct-current voltage converter, so that the direct current from the DC power supply can directly enter the vehicle's direct-current intermediate circuit. The dc voltage provided at the energy connection can thus be converted by means of the dc voltage converter of the electric vehicle with overall lower losses into a dc voltage suitable for charging the traction battery.

According to a further embodiment of the charging method according to the invention, a direct voltage converter coupled to the DC power source and connected upstream of the inverter can be bypassed during the charging process. The DC voltage converter can be a DC/DC converter belonging to a DC power supply, which converts an unregulated DC voltage generated by an energy conversion module (e.g. a photovoltaic module) of the DC power supply into a regulated DC voltage with a voltage level that changes when necessary. In this regard, the direct voltage converter may be integrated in the DC power supply. In the embodiment of the charging method according to the invention described here, the unregulated direct voltage (which is applied to the output of the DC power supply) is therefore applied directly to the direct current intermediate circuit of the electric vehicle. As a result, the conversion losses can be minimized to the greatest possible extent, since in this case the vehicle-side direct-current voltage converter is the only power conversion unit which is connected in the current path between the DC power source and the traction battery and takes part in the charging process.

According to a further embodiment of the charging method according to the invention, in order to bypass the inverter and, if necessary, the dc voltage converter, a current path bypassing both can be activated by means of a switch.

According to a further embodiment of the charging method according to the invention, the output of the DC power supply can be connected to the energy connection or to the current input thereof for carrying out a charging process of the electric vehicle. The coupling can take place separately or directly, i.e. for example by means of a current path which is provided specifically for the charging process and which is activated by means of the aforementioned switch. On the other hand, however, the coupling can also take place indirectly, so that the already existing distribution infrastructure (for example a distribution network installed in a building) is mainly used. In any case, the modified coupling of the output of the DC power source to the energy tap results in the bypassing of at least one current converting device (i.e. AC/DC, DC/AC, DC/DC converter) normally connected between them. In other words, within the scope of the charging method according to the invention, the direct voltage provided by the DC power supply, preferably the unregulated direct voltage provided by its energy conversion module(s), can be provided on a charging plug of the electric vehicle for charging the traction battery.

In a different embodiment of the charging method according to the invention, preferably in the case of a DC voltage converter which additionally bypasses the DC power supply, the output of the DC power supply can be coupled to phases (e.g. L2 and L3) on the energy connection which are otherwise used for ac charging of the electric vehicle with three-phase currents (L1, L2, L3, N).

Furthermore, an apparatus for charging an electric vehicle directly on a DC power supply is provided according to the invention. The charging device has a DC power supply of the type already mentioned, in particular a photovoltaic installation, which may have at least one photovoltaic module. Furthermore, the device according to the invention has an energy connection which is coupled to a DC power supply. The energy connection can be arranged in or on a housing to which the DC power supply is also associated, i.e. for example, connected to the building grid. Furthermore, the device according to the invention has a switch which is coupled between the DC power source and the energy connection and which is configured to bypass, when it is activated, an inverter arranged between the current-and voltage-providing output of the DC power source and the energy connection.

According to a further embodiment of the charging device, the switch may be further configured to bypass a rectifier provided between the DC power source and the inverter. As already described, the DC voltage converter can therefore also be bypassed in addition to the building-side inverter, which can usually be connected upstream of the inverter and is assigned, for example, to a DC power supply.

In general, the charging device according to the invention can be designed such that the aforementioned charging method according to the invention can thus be implemented.

In a further embodiment of the charging device according to the invention, the switch may be configured to connect two current-and voltage-providing outputs of the DC power supply with two phases (e.g. L2 and L3) on the energy connection, which phases are otherwise or generally used for charging the electric vehicle with alternating current. In particular, the inverter on the building side and preferably also the DC voltage converter connected upstream of the inverter are bypassed, so that the unregulated DC voltage of the DC power source can be supplied directly to the electric vehicle without prior current or voltage conversion. In summary, the only current or voltage conversion process takes place only via the DC/DC converter, which is connected upstream of the traction battery of the electric vehicle. The DC/DC converter converts the unregulated voltage generated by the one or more current generating modules of the DC power source into a direct current voltage suitable for charging the traction battery with little loss.

It is to be understood that the features mentioned above and those yet to be explained below can be used not only in the respectively given combination, but also in other combinations or alone, without departing from the scope of the present invention.

Further advantages and embodiments of the invention emerge from the description and the drawing as a whole.

Drawings

Fig. 1 shows a schematic diagram of a conventional charging process of an electric vehicle, which is carried out according to the prior art.

Fig. 2 shows a schematic diagram of an exemplary charging process of an electric vehicle according to the invention.

Detailed Description

Fig. 1 shows an exemplary charging infrastructure on which an electric vehicle is to be charged. The charging process is carried out using electricity generated by a DC power source 1, which may be, for example, a photovoltaic installation installed on a building 5. The DC power source 1 is coupled to a DC voltage converter 2, which is in turn coupled to an inverter 3. An unregulated voltage of the DC power source 1 is present at the input side of the DC voltage converter 2. The dc voltage converter 2 regulates/stabilizes this input voltage and, if necessary, adapts the voltage level of this input voltage, which is then converted into an ac voltage or an ac current by the inverter 3. The alternating current can be fed into the building grid (not shown in detail in fig. 1) and used in the building 5 itself or into the supply grid.

In the example shown in fig. 1, the ac voltage provided at the energy connection 4 is used to charge the electric vehicle 9. The vehicle charging infrastructure may correspond to a conventional charging infrastructure and is only shown here approximately by a rectifier 6, which is coupled to a dc voltage converter 7, which is itself coupled to a traction battery 8.

As shown, in a conventional charging process known from the prior art, the current path between the DC power source 1 and the traction battery 8 extends over a total of 4 current or voltage converters. The efficiency of a charging chain constructed in this way is greatly reduced, since the current/voltage conversion performed by each current or voltage converter has losses.

In contrast, fig. 2 shows a charging infrastructure arrangement according to the invention, on which the charging method according to the invention is based. Based on the same basic configuration, the same elements are known with the same reference numerals and are not described again in detail.

In contrast to the prior art, according to the embodiment of the charging method according to the invention, the two converters between the DC power source 1 and the energy connection on the building 5 side, i.e. the DC voltage converter 2 and the inverter 3, are bypassed and are not involved in the charging process. Therefore, their losses do not reduce the efficiency of the charging chain according to the invention. In the example shown, an alternative current path is provided by means of the relay 10 as a switch, by means of which an output of the DC power supply 1 is coupled to the energy connection 4.

The alternative current path can also only bypass the rectifier 2 and lead back into the usual current path leading through the inverter 3, wherein the inverter 3 is switched through so that its switching losses do not affect the current leading and do not reduce the efficiency of the charging process.

Alternatively, it is also possible within the scope of the charging method according to the invention to bypass or pass through the inverter 3 only, so that the voltage regulated by the rectifier 2 can be applied directly to the energy connection 4.

In the method according to the invention, the vehicle-side charging circuit can also be adapted differently from the prior art, so that the vehicle-side rectifier 6 is either passed through (option shown in fig. 2) or bypassed (option not shown in fig. 2). Since the (possibly regulated) dc voltage for charging the electric vehicle 9 is advantageously already available at the energy connection 4, the charging voltage need not be rectified by the rectifier 6, so that the efficiency of the charging method according to the invention can be further increased.

The charging method according to the invention can be started automatically as soon as the electric vehicle 9 is coupled with the energy connection. The energy tap 4 may be configured to subsequently switch the current path for direct (charging) current provided directly from the DC power source 1. At the same time, information can be transmitted from the energy connection 4 to the electric vehicle 9, so that the rectifier 6 can be switched through.

Furthermore, a device can be provided in the energy connection 4, which device is configured to recall information from the DC power source 1 about the power supplied by it and to compare this power with a possible charging power of the electric vehicle 9. The device may be configured to determine whether the method according to the invention is initiated. The charging method according to the invention may be initiated, for example, when a certain threshold value with respect to the charging power provided by the DC power supply 1 is reached. The threshold value can be set by the user. The device may be configured to start the charging method according to the invention only when the DC power source 1 is capable of providing a charging power corresponding to 30% of the maximum charging power of the electric vehicle 9 or 30% of the maximum charging power that can be provided by the energy connection 4. If the charging power provided by the DC power source 1 is below a threshold value, the charging process may proceed according to fig. 1, whereby the charging power provided by the DC power source 1 is supplemented by a supply grid connected to the building 5.

Claims

1. A method for charging an electric vehicle (9) directly on a DC power supply (1), the method having the steps of:

providing a direct current on an energy connection (4) by means of the DC power supply (1);

charging the electric vehicle (9) at the energy connection (4);

wherein during a charging process an inverter (3) arranged between the DC power source (1) and the energy connection (4) is bypassed such that a direct current provided by the DC power source (1) is provided at the energy connection (4).

2. The method of claim 1, wherein the first and second light sources are selected from the group consisting of,

wherein during the charging process a rectifier (6) in the charging line on the vehicle side is bypassed.

3. The method according to claim 1 or 2,

wherein during a charging process a direct voltage converter (2) connected to the DC power source (1) and connected upstream of the inverter (3) is bypassed.

4. The method of any one of claims 1 to 3,

wherein for carrying out the charging process of the electric vehicle, the output of the DC power source (1) is connected to the energy connection (4), preferably to the energy connection (4), which phases are otherwise used for alternating current charging of the electric vehicle (9) with three-phase current.

5. A method according to claim 3, wherein for bypassing the inverter (3) and, if necessary, the dc voltage converter, a current path bypassing both is activated by means of a switch (10).

6. An apparatus for directly charging an electric vehicle (9) on a DC power supply (1), the apparatus having:

a DC power supply (1);

an energy connection (4) coupled to the DC power source (1);

a switch (10) configured to bypass, when activated, an inverter (3) arranged between the current and voltage providing output of the DC power source (1) and the energy junction (4).

7. The apparatus according to claim 6, wherein the switch (10) is further configured to bypass a direct voltage converter (2) provided between the DC power source (1) and the inverter (3).

8. The device according to claim 6 or 7, wherein the switch (10) is configured to connect two current and voltage providing outputs of the DC power source (1) with two phases on the energy connection (4), which phases are otherwise used for AC charging the electric vehicle.