DE102019005476A1 - Charging device and method for charging an electrical energy storage device of a vehicle - Google Patents

Abstract

The invention relates to a charging device (1) for charging an electrical energy store (2) of a vehicle, comprising:
a first DC voltage converter (3) for converting an AC voltage (U _AC ) into a first DC voltage (U _DC1 ),
- An input AC voltage connection (4) for providing the AC voltage (U _AC ), and
an output-side DC voltage connection (5), with which the electrical energy store (2) can be supplied with the first DC voltage (U _DC1 ),
a second DC voltage converter (6), with which the AC voltage (U _AC ) can be converted into a second DC voltage (U _DC2 ),
- A first capacitor (C1) of the first DC converter (3), which can be charged by the first DC converter (3) with the first DC voltage (U _DC1 ), and
- A second capacitor (C2) of the second DC converter (6), which can be charged by the second DC converter (6) with the second DC voltage (U _DC2 ), wherein
- With the first capacitor (C1) and / or the second capacitor (C2), the electrical energy store (2) of the vehicle via the output-side DC voltage connection (5) with the first DC voltage (U _DC1 ) and / or the second DC voltage (U _DC2 ) is available.

Description

The invention relates to a charging device for charging an electrical energy store of a vehicle. Furthermore, the invention relates to a method for charging an electrical energy store of a vehicle, wherein an electrical voltage is provided and the AC voltage is converted into a first DC voltage, the electrical energy store of the vehicle being supplied with the first DC voltage.

AC on-board chargers are often either galvanically isolating or galvanically coupled. With isolating on-board loaders, many components are involved in the power conversion, such as a transformer. Therefore, their power density, weight and price are relatively high. It is advantageous to be able to use the transformer to prevent leakage currents via the Y capacities of the high-voltage electrical system. Up to now, galvanically coupled on-board chargers have only been used in a few vehicles, since they generate balancing currents via the Y capacities that trigger the RCD in the building services or complex countermeasures for leakage current monitoring and / or leakage current compensation are necessary in order to prevent them To be able to charge AC charging station. These additional measures are associated with relatively high costs. In the event of an insulation fault after rectification of the AC input voltage, a superimposed DC current is added to the AC charging current on the connection side of the building services, which drives the type A Fl circuit breaker into saturation in the building services and thus makes it ineffective. This can only be counteracted by increased insulation in the area of the on-board charger between the AC rectification and the secondary side of the transformer. After rectifying the AC grid voltage, the negative voltage potential is related to the neutral conductor and PE a negative sine half wave.

A charger would transfer this negative potential curve to the entire high-voltage system of the vehicle.

From the published application DE 10 2017 009 355 A1 A method for operating a first on-board electrical system with a first electrical direct voltage and a second on-board electrical system with a second electrical voltage is known. The first and the second on-board electrical system are electrically coupled by means of an energy coupler having a first clocked energy converter, the first and the second direct electrical voltage being electrically insulating from an electrical reference potential by means of an electrical insulation device. The electrical insulation device is used for monitoring, the first and the second electrical system being galvanically coupled by means of the energy coupler, wherein in the event of a fault in the insulation device in a region of one of the two electrical systems, the energy coupler controls electrical potentials of the other of the two electrical systems in such a way that respective potential differences of these electrical potentials to the reference potential are smaller than a predetermined comparison value.

The disclosure DE 10 2017 010 390 A1 discloses an energy converter for electrically coupling a first electrical system to which a first electrical direct voltage is applied and a second electrical electrical system to which a second electrical direct voltage is applied. The energy converter has a first series circuit comprising three switching elements connected in series, the first series circuit being designed for connection to the first or the second of the on-board networks. The series connection has two connection points of two respective ones of the switching elements, at which the respective switching elements are electrically coupled to one another, a respective one of the connection points being connected to the other of the two on-board networks by means of a respective electrical inductance.

The disadvantage of conventionally insulating on-board loaders is the large space required and the expensive and heavy components. Single-stage galvanically coupled on-board loaders usually have asymmetrical high-voltage potentials.

The object of the present invention is to provide a charging device and a method with which HV potentials are stable over time PE can be achieved and a simultaneous potential symmetry can be set.

This object is achieved by a loading device and a method according to the independent patent claims. Useful further training results from the subclaims.

One aspect of the invention relates to a charging device for charging an electrical energy store of a vehicle. The charging device has a first DC voltage converter for converting an AC voltage into a first DC voltage and an AC voltage connection on the input side for providing the AC voltage. The electrical energy store can be supplied with the first direct voltage with an output-side direct voltage connection. With a second DC voltage converter of the charging device, the AC voltage can be converted into a second DC voltage, and a first capacitor of the first DC converter can be charged with the first DC voltage of the first DC converter. The charging device is provided with a second capacitor of the second DC voltage converter and the capacitor can be charged with the second DC voltage with the second DC voltage converter. With the first capacitor and / or the second capacitor, the electrical energy store of the vehicle can be supplied with the first and / or the second direct voltage via the output-side direct voltage connection.

By converting the AC voltage using the first DC voltage converter and the second DC voltage converter into the first DC voltage and / or the second DC voltage, the currents on the two DC voltage converters are also divided. The components of the charging device can thus be dimensioned small, as a result of which the circuit can be designed to be small, light and, in particular, inexpensive. The number of components through which current flows is reduced by the charging device according to the invention, as a result of which a higher efficiency can be achieved during a charging process of the electrical energy store. In particular, the proposed charging device stabilizes the high-voltage potentials with respect to the potential of the neutral conductor to a constant value over time, as a result of which a leakage current via the Y capacitors of the high-voltage system can be avoided. For example, measures for leakage current monitoring and leakage current compensation can be dispensed with. By converting the AC voltage into the first DC voltage and / or the second DC voltage and by providing these DC voltages to the capacitors, the high-voltage potentials can be balanced with respect to the potential of the neutral conductor, as a result of which the energy content of the Y-capacities of the HV system can be minimized.

By using the first DC voltage converter and the second DC voltage converter, a transfer of negative sine waves to the high-voltage system can be avoided. It is also possible to dispense with a double insulation requirement for the connected high-voltage system for the charging device. Likewise, the charging device can detect an insulation fault both from the negative high-voltage voltage to the potential of the neutral conductor and from the positive high-voltage voltage to the potential of the neutral conductor in the high-voltage system by measuring the differential current at the AC source or by measuring the current at the potential of the neutral conductor will.

In particular, the charging device and the first and second DC voltage converters can provide stable HV potentials with respect to time PE can be achieved with simultaneous potential symmetry. The first DC-DC converter is designed as a boost converter or step-up converter. The first DC / DC converter charges the first capacitor and stabilizes the HV plus potential in relation to the neutral conductor to a positive value that is constant over time. A conventional boost converter is shown for the positive voltage half-wave of the voltage curve of the AC voltage and an inverting boost converter is shown for the negative voltage half-wave of the voltage curve of the AC voltage. The second DC / DC converter in particular charges the second capacitor and stabilizes the HV minus potential with respect to the neutral conductor to a constant negative value. An inverting boost converter is shown for the positive voltage half-wave using the second DC voltage converter and a conventional boost converter is shown for the negative voltage half-wave using the first DC voltage converter.

The first and second DC-DC converters can be, for example, a step-up converter, an inverting step-up converter, a voltage converter, an energy converter or a step-up converter. The charging device is in particular an on-board charger or an on-board charger with which the applied AC voltage on the input side can be converted into a DC voltage on the output side. The voltage level of the DC voltage on the output side is always higher than the voltage level of the AC voltage on the input side. The AC voltage connection on the input side can be, for example, an AC charging station or a house connection. The DC voltage connection on the output side is, for example, a battery connection of the electrical energy store or a connected load.

A further aspect of the invention relates to a method for charging an electrical energy store of a vehicle, an AC voltage being provided and the AC voltage being converted into a first DC voltage. The vehicle's electrical energy store is supplied with the DC voltage. The alternating voltage is converted into a second direct voltage and a first capacitor of a first direct voltage converter is charged with the first direct voltage and a second capacitor of a second direct voltage converter is charged with the second direct voltage. With the first capacitor and / or the second capacitor, the electrical energy store of the vehicle is supplied with the first or the second DC voltage. In particular, the method is carried out with the loading device described above.

Further advantages, features and details of the invention emerge from the following description of preferred exemplary embodiments and from the drawings. The features and combinations of features mentioned above in the description and the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the combination indicated in each case, but also in other combinations or on their own, without the scope of Leaving invention.

• 1 eine schematische Darstellung einer Ladevorrichtung;
• 2 die Ladevorrichtung nach 1 beim Betrieb in der negativen Spannungshalbwelle der Wechselspannung; und
• 3 die Ladevorrichtung nach 1 beim Betrieb in der positiven Spannungshalbwelle der Wechselspannung.

The following figures show:

• 1 a schematic representation of a loading device;
• 2nd the loading device after 1 when operating in the negative voltage half-wave of the AC voltage; and
• 3rd the loading device after 1 when operating in the positive voltage half-wave of the AC voltage.

In the figures, functionally identical elements are provided with the same reference symbols.

The 1 shows a loading device 1 for charging an electrical energy store 2nd of a vehicle. The charger 1 has a first DC converter 3rd to convert an AC voltage U _AC into a first DC voltage U _DC1 on. The AC voltage U _AC comes with an AC voltage connection on the input side 4th provided. With a DC connection on the output side 5 can the electrical energy storage 2nd with the first DC voltage U _DC1 are supplied or charged. The charger 1 has a second DC-DC converter 6 with which the AC voltage U _AC into a second DC voltage U _DC2 can be converted. The first DC converter 3rd has a first capacitor C1 on which of the first DC-DC converters 3rd with the first DC voltage U _DC1 can be charged. The second DC converter 6 has a second capacitor C2 on which of the second DC-DC converters 6 with the second DC voltage U _DC2 can be charged. With the first capacitor C1 and / or the second capacitor C2 can the electrical energy storage 2nd of the vehicle via the DC connection on the output side 5 with the first and / or the second DC voltage U _DC1 , U _DC2 be supplied.

The AC voltage U _AC can on an AC voltage source 7 generated or provided. At the AC voltage source 7 it can be, for example, a charging station or a house connection. The electrical energy storage 2nd can in particular be a vehicle battery or a traction battery and has an internal resistance R . For example, using a measuring unit 8th the AC voltage on the input side can be measured. In particular, it is a voltage measurement.

The first capacitor C1 and the second capacitor C2 are connected in series to each other and have a center tap between them. The first capacitor C1 and the second capacitor C2 form, for example, an output capacitor for charging the electrical energy store 2nd . The first DC converter 3rd and the second DC-DC converter 6 are in particular galvanically coupled to one another. The first DC converter 3rd is designed to establish a first potential of the first and / or second DC voltage in relation to a reference potential N to stabilize and the second DC converter 6 can have a second potential of the first and / or second DC voltage U _DC1 , U _DC2 in relation to the reference potential N stabilize.

The 1 shows, for example, a single-phase charging of the electrical energy store 2nd . Likewise, the loading device 1 can be used for multi-phase or three-phase charging.

With three-phase charging, tapping is carried out via a star voltage, which means that the components only rely on the voltage of the electrical energy store 2nd must be interpreted. The loading device 1 constructed as a multi-phase converter or multi-phase on-board charger with a common DC link capacitor. A reduction in the total of the intermediate circuit capacitor can thereby be achieved. In particular, there is a reduction to a third compared to a board loader with three different branches. With multi-phase charging, EML optimization can be performed on the input-side AC voltage connection in interleaving mode 4th and on the output-side DC voltage connection 5 be implemented. The possibility of regulating the HV potentials to an identical level makes it possible to couple all three phases in parallel directly after the boost stage. This has the advantage that a common buffer capacitor for all three phases of the charging device 1 can be used. It must capacity for the single-phase charging requirement is not applied to each phase. The capacity can thus be reduced to a third of the total value compared to a three-phase galvanically isolated converter. In three-phase charging, three charging devices are connected in parallel to one another, these being connected to the common neutral conductor and each being supplied with the AC voltage by one phase. In three-phase charging, each charging device does not need the first and second capacitor, but the three charging devices all feed a common buffer capacitor and the buffer capacitor then charges the electrical energy store or the high-voltage battery of the vehicle. This allows three charging devices connected in parallel 1 a simple three-phase on-board loader can be created or provided. When using three charging devices for three-phase charging, it is also achieved that the currents of each individual current phase are in phase with the voltage. The performance of all three phases is also identical. The high-voltage potentials also remain at a stable level if the buffer capacitor is not chosen too small. However, the buffer capacitor must also be able to transfer the current ripple to the electrical energy store 2nd of the vehicle, which requires a value in the high microfarad range to millifarad range. The high-voltage potentials are also symmetrical to the neutral conductor N . In three-phase charging, the buffer capacitor consists of a first capacitor and a second capacitor. The first capacitor and the second capacitor are connected in series.

The 2nd shows the loading device 1 , the first DC-DC converter 3rd works as an inverting boost converter and the second DC-DC converter 6 works as a boost converter. In particular, in the 2nd the functioning of the loading device 1 shown in which the negative voltage half-wave of the voltage curve of the AC voltage U _AC is taken into account.

The first DC converter 1 works as an inverting boost converter with the component of a semiconductor switch S1 _n , an inductance L1 , a semiconductor switch S1 _p and a diode D1 _n . Here, the second semiconductor switch S1 _p used only because of its body diode. In particular, the first DC-DC converter charges 3rd the capacitor C1 on. In the phase of the choke current build-up (here in the 2nd shown with the current flow path DS1 ) and in the freewheeling phase (in the 2nd shown with the current flow path FP1 ) of the choke current, the current only flows through the diode D1 _n and the semiconductor switch S1 _p. The semiconductor switch can be used to improve efficiency S1 _p be turned on while its body diode is energized.

The second DC converter 6 works in the 2nd as a conventional boost converter with the following components of a semiconductor switch S2 _n , an inductance L2 , another semiconductor switch S2 _p and a diode D2 _n . Here, the second DC-DC converter charges 6 the capacitor C2 on. In the phase of the choke current build-up (in the 2nd shown by the current flow path DS2 ) the current flows over and in the freewheeling phase (in the 2nd shown with the current flow path FP2 ) of the choke current, the current only overflows D2 _n and S2 _p . In particular, only the body diode of the semiconductor switch is used S2 _p used. The semiconductor switch can be used to improve efficiency S2 _p be turned on while its body diode is energized.

The two capacitors loaded here C1 and C2 can then use the electrical energy storage 2nd charge. The 3rd shows the loading device 1 , here the mode of operation during the positive voltage half-wave of the voltage profile of the AC voltage U _AC is explained in more detail.

The first DC-DC converter functions here 3rd as a boost converter and the second DC voltage converter 6 as an inverting boost converter. The first DC-DC converter is used to build up the inductor current 3rd operated as a conventional boost converter. The semiconductor switch S1 _n , the inductance L1 , the semiconductor switch S1 _p and the diode D1 _p needed. In particular, the first capacitor C1 loaded. In the phase of the choke current build-up (in the 3rd through the current flow path DS1 shown) and in the free-running phase of the inductor current (in the 3rd through the current flow path FP1 shown), the current flows through the AC voltage source 7 . The semiconductor switch can be used to improve efficiency S1 be turned on while its body diode is energized. In the free-running phase of the choke current, the capacitor C1 loaded.

The second DC converter 6 works here as an inverting boost converter and charges the second capacitor C2 . In particular, the semiconductor switch S2 _p , the inductance L2 , the semiconductor switch S2N and the diode D2 _n used or switched. In the phase of the choke current build-up (in the 3rd through the current flow path DS2 shown), the current flows through the AC voltage source 7 and in the free-running phase of the choke current (in the 3rd through the current flow path FP2 shown) the current only flows through the diode D2 _p and the semiconductor switch S2 _n . To improve efficiency, the Semiconductor switch S2 _n be turned on while its body diode is energized. In particular, the capacitor becomes here in the free-running phase of the inductor current C2 loaded.

Because especially in the positive and in the negative voltage half-wave of the voltage curve of the AC voltage UAC always one of the two DC / DC converters 3rd , 6 is in conventional operation and the other is in inverting operation, the current profiles can look identical in both voltage half-waves. This also applies to the charging current of the electrical energy store 2nd . Only with the current profiles of the two inductors L1 , L2 small differences are possible. In total, the currents from the inductors L1 , L2 from the AC voltage source 7 taken. This results in particular in the potential symmetry of the HV plus pole and the HV minus pole to the neutral conductor N . The energy content stored in the Y capacities thus takes on its minimum value in total. For example, a PFC function can also be represented by the current being in phase with the voltage. There can be predetermined load currents in the electrical energy store 2nd are shown and there is no leakage current across the Y capacitors, since there is a stable voltage. As a result, the potential is balanced between HV-Plus and HV-Minus to the neutral N .

The diodes D1 _n and D2 _n are in particular freewheeling diodes for the freewheeling path of the inductor current in the negative voltage half-wave. The diodes D1 _p and D2 _p are freewheeling diodes for the freewheeling path of the inductor current in the positive voltage half-wave. The semiconductor switch S1 _n and S2 _n are used in the positive voltage half-wave to use the body diode as freewheeling and in the negative voltage half-wave they are used as clocking semiconductor switches to represent the voltage-inverting boost converter.

The semiconductor switch S1 _p and S2 _p are used in the positive voltage half-wave as a clocking semiconductor switch to represent the non-voltage-emitting boost converter.

For example, with the loading device 1 an insulation fault from HV-Plus too N be recognized. In the event of an insulation fault, currents from one phase occur in particular L to the neutral conductor N and the difference between these two currents suddenly shows a DC component as soon as the insulation fault occurs. With the measuring unit 8th For example, an instantaneous voltage can be measured, from which a target current can be determined. The target current is, in particular, the current flowing through the AC voltage source 7 flows. It can thereby be achieved that the alternating current is in phase with the alternating voltage. Alternatively, this current can be on PE be measured. Insulation faults from HV-Plus too N can be done by measuring the PE current or by measuring the differential current between L and N be recognized. A requirement for double insulation for the entire HV system connected during AC charging is not necessary.

With an insulation fault of HV minus too PE the result is the same as the HV-Plus insulation fault PE . The only sign is the differential current between L and N or the current PE opposite. Insulation fault from HV minus too N and from HV-Plus too N can be via a PE current monitoring or a differential current measurement from L to N recognized and measured. A requirement for double insulation for the entire HV system that is connected during AC charging is not necessary.

Reference list

1

Loading device

2nd

electrical energy storage

3rd

first DC converter

4th

AC voltage connection on the input side

5

output-side DC voltage connection

6

second DC converter

7

AC voltage source

8th

Unit of measurement

C1, C2

first and second capacitor

DS1, DS2

Current flow paths during choke current build-up

D1n, D1p, D2n, D2p

Diodes

FP1, FP2

Current flow paths during free-running phase of the choke current

L

phase

L1, L2

Inductors

N

Neutral conductor

R

Internal resistance

S1n, S1p, S2n, S2p

Semiconductor switch

UAC

AC voltage

UDC1, UDC2

first and second DC voltage

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102017009355 A1 [0004]
• DE 102017010390 A1 [0005]

Claims (5)

Charging device (1) for charging an electrical energy storage device (2) of a vehicle, characterized by - a first DC voltage converter (3) for converting an AC voltage (U _AC ) into a first DC voltage (U _DC1 ), - an AC voltage connection (4) on the input side Providing the alternating voltage (U _AC ), and - an output-side direct voltage connection (5), with which the electrical energy store (2) can be supplied with the first direct voltage (U _DC1 ), - a second direct voltage converter (6), with which the alternating voltage (U _AC ) can be converted into a second DC voltage (U _DC2 ), - a first capacitor (C1) of the first DC voltage converter (3), which can be charged by the first DC voltage converter (3) with the first DC voltage (U _DC1 ), and - a second Capacitor (C2) of the second DC voltage converter (6), which can be charged by the second DC voltage converter (6) with the second DC voltage (U _DC2 ), wobbled ei - with the first capacitor (C1) and / or the second capacitor (C2) the electrical energy store (2) of the vehicle via the output-side DC voltage connection (5) with the first DC voltage (U _DC1 ) and / or the second DC voltage (U _DC2 ) is available. Loading device after Claim 1 , characterized in that the first capacitor (C1) and the second capacitor (C2) are connected in series. Loading device after Claim 1 or 2nd , characterized in that the first direct voltage converter (3) and the second direct voltage converter (6) are galvanically coupled to one another. Charging device according to one of the preceding claims, characterized in that the first DC voltage converter (3) is designed to stabilize a first potential of the first DC voltage (U _DC1 ) and / or second DC voltage (U _DC2 ) with respect to a reference potential (N) the second DC voltage converter (6) is designed to stabilize a second potential of the first DC voltage (U _DC1 ) and / or second DC voltage (U _DC2 ) in relation to the reference potential (N). Method for charging an electrical energy store (2) of a vehicle, wherein - an AC voltage (U _AC ) is provided, and - the AC voltage (U _AC ) is converted into a first DC voltage (U _DC1 ), wherein - the electrical energy store (2) of the vehicle is supplied with the first DC voltage (U _DC1 ), characterized in that - the AC voltage (U _AC ) is converted into a second DC voltage (U _DC2 ), - with the first DC voltage (U _DC1 ) a first capacitor (C1) a first DC voltage converter (3) is charged, and wherein - with the second DC voltage (U _DC2 ) a second capacitor (C2) of a second DC voltage converter (6) is charged, - with the first capacitor (C1) and / or the second capacitor (C2) the electrical energy store (2) of the vehicle is supplied with the first DC voltage (U _DC1 ) and / or the second DC voltage (U _DC2 ).

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