DE102022201034A1 - Combined capacitor for a DC converter, DC converter, electric axle drive and vehicle - Google Patents

Abstract

The present invention relates to a capacitor arrangement (10) for a polyphase DC-DC converter (100) for converting a DC input voltage into a DC output voltage for charging a vehicle battery in an electric vehicle or hybrid vehicle, the capacitor arrangement (10) having a capacitor (12) on the input side first capacitor windings (121) and an output-side capacitor (14) with second capacitor windings (141), which are accommodated in a housing (22) and between which power electronics (20) are connected, with a first of the two capacitors (12, 14 ) has a positive-pole power contact (142) and a negative-pole power contact (144), with each of which a first power line (143, 145) located in the housing (22) is electrically connected, with a second of the two capacitors (12, 14) having a positive-pole or negative-pole power contact (122) to which a second power line (123) located in the housing (22) is electrically connected, the power contacts (122, 142, 144) extending out of the housing (22), the second Power line (123) opposite polarity first power line (143, 145) is electrically connected to both the first capacitor windings (121) and the second capacitor windings (141).

Description

The invention relates to a capacitor arrangement for a DC-DC converter and the DC-DC converter.

Purely electric vehicles and hybrid vehicles are known in the prior art, which are driven exclusively or in support of one or more electric machines as drive units. In order to supply the electrical machines of such vehicles with electrical energy, the vehicles include electrical energy stores, in particular rechargeable electrical batteries. Batteries are required for high drive power, which provide a correspondingly high DC voltage of, for example, 400V or 800V. Such power batteries are referred to as high-voltage batteries (HV batteries).

The recharging of the HV batteries is currently a challenge, as this requires a charging voltage of several hundred volts, for example 800V, in order to charge the HV batteries effectively without impairing their functionality. However, the charging voltage that conventional charging stations provide for electric vehicles is regularly significantly lower than the desired charging voltage, around 800V. In order to provide such charging voltages, direct voltage converters (DC/DC converters) are used, which are connected between a DC voltage source with an output voltage (e.g. 400V) that is lower than the desired charging voltage (e.g. 800V) and the HV battery to be charged is switched.

The DC-DC converters known from the prior art have the disadvantage that the various components located in the converter are arranged in an unfavorable manner in relation to one another, so that they require a comparatively large amount of space. This increases the manufacturing effort and also the manufacturing costs.

It is an object of the invention to provide a capacitor arrangement in which the disadvantages mentioned above are at least partially overcome.

According to the invention, this object is achieved by the capacitor arrangement, the DC voltage converter, the electric axle drive and the vehicle according to the independent patent claims. Advantageous refinements and developments of the invention emerge from the dependent patent claims.

The capacitor arrangement according to the invention is designed to be used in a polyphase DC-DC converter for converting a DC input voltage into a DC output voltage for charging a vehicle battery or a vehicle battery arrangement in an electric vehicle or hybrid vehicle. The multi-phase DC-DC converter typically includes a DC voltage input for feeding the DC input voltage and a DC voltage output for delivering the DC output voltage. A storage choke and power semiconductors are located between the DC voltage input and the DC voltage output. The storage choke is used to temporarily store energy in the form of magnetic fluxes. For this purpose, the storage choke can have a plurality of windings, each of which is electrically connected to a half-bridge of the power electronics, in particular to a point between a high side and a low side of the half-bridge.

The polyphase DC-DC converter also includes the capacitor arrangement according to the invention. The capacitor arrangement has an input-side capacitor and an output-side capacitor. The input-side capacitor is coupled to a DC input voltage source providing the DC input voltage (e.g. a 400V voltage source such as a battery or fuel cell or power grid), while the output-side capacitor is coupled to a DC output voltage source (e.g. an 800V battery) accepting the DC output voltage ) connected is. The input-side capacitor and the output-side capacitor each comprise a plurality of capacitor windings, which are also known as film capacitors. In addition, the input-side capacitor and/or the output-side capacitor can include at least one interference suppression capacitor, which is also known as a Y capacitor or electrolytic capacitor. The input-side capacitor and the output-side capacitor are accommodated in a housing of the capacitor arrangement. Power semiconductors are arranged between the input-side capacitor and the output-side capacitor.

A first capacitor from the input-side capacitor and the output-side capacitor, preferably the output-side capacitor, has a positive-pole current contact and a negative-pole current contact. A first power line located in the housing is electrically connected to the positive-pole power contact and the negative-pole power contact. Thus, two first power lines, namely a positive-pole first power line and a negative-pole first power line, are associated with the first capacitor, preferably the output-side capacitor. A second capacitor from the input side capacitor and the output side Capacitor, preferably the input-side capacitor, has a positive-pole or negative-pole current contact with which a second current line, which is also located in the housing, is electrically connected. This means that the second power line is either positive or negative when the second capacitor has a positive or negative power contact, respectively. Thus, one of the two first power lines has the same polarity as the second power line and the other of the two first power lines has opposite polarity to the second power line. The first power line, which has opposite polarity to the second power line, is electrically connected both to the first capacitor windings and to the second capacitor windings. The power contacts extend out of the housing and can be contacted from the outside.

The first power line, which has the opposite polarity to the second power line, is therefore assigned both to the first capacitor and to the second capacitor. In this way, either a positive-pole or a negative-pole current contact is required for the second capacitor, preferably the input-side capacitor, so that one of the two signs can be dispensed with. For example, the negative-pole power contact can be dispensed with if the negative-pole first power line is assigned to both the first input-side capacitor and the output-side capacitor, in particular is electrically connected to both the first capacitor windings and the second capacitor windings. In this case, no negative-pole power contact is required for external contacting of the second capacitor. This favors a more compact design of the polyphase DC voltage converter. An otherwise required power contact n, take up additional space and increase the assembly effort. In addition, thanks to the omission of one of the two current contact signs, the remaining current contact can be formed over a larger area. This reduces the current density in the affected capacitor and, as a result, also the heat generated due to the current flow.

According to one embodiment, one of the two first power lines is arranged in a first edge area of the housing, with the other of the two first power lines, preferably the first power line with opposite polarity to the second power line, extending from the first edge area to a second edge area opposite the first edge area. This spatial separation of the first two power lines reinforces the potential separation between them and increases the safety of the multi-phase DC-DC converter.

According to a further embodiment, at least one interference suppression capacitor is electrically connected to the first power lines and/or the second power line. In this way, the power lines can also be used for the interference suppression capacitors at the same time, so that space is saved.

According to a further embodiment, the first of the two capacitors has a plurality of positive-pole and/or a plurality of negative-pole current contacts. The power contacts are preferably lined up alternately between the positive pole and the negative pole. This measure favors a more even current distribution in the area of the intermediate circuit capacitor, which improves the EMC properties of the multi-phase DC/DC converter, for example.

The invention also relates to a DC voltage converter for charging a DC voltage source, in particular a HV battery, in an electric vehicle or a hybrid vehicle. In addition, the invention relates to an electric axle drive with such a DC voltage converter. In addition, the invention relates to a vehicle, in particular an electric vehicle or a hybrid vehicle with such an electric axle drive. This results in the advantages already described in connection with the capacitor arrangement according to the invention, also for the DC voltage converter according to the invention, the electric axle drive according to the invention and the vehicle according to the invention.

According to one embodiment, the polyphase DC-DC converter includes a storage choke that has a number of windings and/or power electronics that are formed by a number of half-bridges of an inverter installed in an electric axle drive. In this way, the electric axle drive can be used as a DC converter at the same time. In this case, the inverter acts as a so-called boost converter, in that it is supplied with current in the opposite direction to normal inverter operation. This is particularly advantageous if the vehicle battery is to be charged using an additional battery or a fuel cell installed in the vehicle. Fuel cells typically provide a DC voltage of 400V. Using the multi-phase DC-DC converter, the 400V voltage can be converted into a 800V voltage to charge a HV battery.

The invention is explained below by way of example using the embodiments shown in the figures.

• 1 ein schematisches Schaltbild eines mehrphasigen Gleichspannungswandlers;
• 2 eine schematische Darstellung einer Kondensatoranordnung gemäß einer Ausführungsform für den Gleichspannungswandler aus 1 in einer seitlichen Schnittansicht, wobei eine minuspolige Stromleitung eines ausgangsseitigen Kondensators sowohl mit mehreren Folienkondensatoren des eingangsseitigen Kondensators als auch mit mehreren Folienkondensatoren des ausgangsseitigen Kondensators elektrisch verbunden ist;
• 3 eine schematische Darstellung der Kondensatoranordnung aus 2 in einer Draufsicht;
• 4 eine schematische Darstellung der Kondensatoranordnung aus 2 in einer weiteren Schnittansicht auf der Ausgangsseite;
• 5 eine schematische Darstellung der Kondensatoranordnung aus 2 in einer weiteren Schnittansicht auf der Eingangsseite.

Show it:

• 1 a schematic circuit diagram of a polyphase DC-DC converter;
• 2 shows a schematic representation of a capacitor arrangement according to an embodiment for the DC-DC converter 1 in a side sectional view, wherein a negative-pole power line of an output-side capacitor is electrically connected both to a plurality of film capacitors of the input-side capacitor and to a plurality of film capacitors of the output-side capacitor;
• 3 a schematic representation of the capacitor arrangement 2 in a plan view;
• 4 a schematic representation of the capacitor arrangement 2 in a further sectional view on the output side;
• 5 a schematic representation of the capacitor arrangement 2 in another sectional view on the entrance side.

Identical objects, functional units and comparable components are denoted by the same reference symbols across the figures. These objects, functional units and comparable components are designed to be identical in terms of their technical features, unless the description explicitly or implicitly states otherwise.

1 shows a schematic circuit diagram of a multi-phase DC-DC converter 100 for converting a DC input voltage, which is provided by a DC voltage source 107, into a DC output voltage, to a rechargeable battery 109, in particular a high-voltage (HV) battery with a standard voltage of 800V , charge in an electric vehicle or hybrid vehicle. The DC voltage source 107 is integrated, for example, in a charging station (such as a charging column) and can provide a voltage of 400V, which forms the DC input voltage. Alternatively, the voltage source 107 can be a mobile voltage source such as a battery or a fuel cell, which provides 400V, for example.

A capacitor arrangement 10 consisting of an input-side capacitor 12 and an output-side capacitor 14 is integrated in the polyphase DC-DC converter 100 . The capacitor arrangement 10 is discussed in more detail below. A storage choke 21 and power electronics 20 are arranged between the two capacitors 12, 14. The storage choke 21 is designed to temporarily store energy in the form of magnetic fluxes. For this purpose, the storage inductor 21 has a plurality of coils 101 AC, three in this case by way of example. By applying a voltage to the windings of the coils 101 A-C, a current flow and, associated therewith, a magnetic flux can be generated in the coils 101 A-C. The power electronics 20 includes a plurality of half-bridges, three in this case by way of example, the number of half-bridges corresponding to the number of coils 101A-C. Each half-bridge includes a high-side switching device 102A-C and a low-side switching device 104A-C. The coils 101A-C are each connected on a side facing away from the input-side capacitor 12 between the respective high-side switching device 102A-C and the low-side switching device 104A-C. The output-side capacitor 14 is arranged on the opposite side of the input-side capacitor 12 of the power electronics 20 . A first filter 103 for eliminating interference signals in the supplied DC input voltage is connected between the DC voltage source 107 and the polyphase DC voltage converter 100 . In addition, a second filter 105 for eliminating interference signals in the generated DC output voltage is connected between the HV battery 109 on the output side and the polyphase DC voltage converter 100 .

During operation of the polyphase DC-DC converter 100, the switching devices 102A-C, 104A-C installed in the power electronics 20 are switched in such a way that a voltage with the same voltage curve is applied to the coils 101A-C, but with a time offset between the coils 101A-C. The coils 101A-C can be provided by the coils installed in an electric machine of an electric axle drive, not shown here. Alternatively or additionally, the power electronics 20 can be provided by an inverter integrated in the electric axle drive. This is particularly advantageous if the DC voltage source 107 is an additional battery or fuel cell located in the vehicle, since in this case the inverter can be used as a boost converter by the inverter returning to its normal operation, in which it is used to convert a DC input voltage is used in an AC output voltage is energized in the opposite direction.

2-3 each show the capacitor arrangement 10 in a schematic representation. 2 shows the capacitor arrangement 10 in a lateral sectional view on a side facing the battery 109 . The input-side capacitor 12 is shown off 2 arranged on the left and the output-side capacitor 14 on the right. The input-side capacitor 12 has several (in this case two by way of example) film capacitors 121 (or “coils”) and an electrolytic capacitor 24 (or “Y capacitor” or “interference suppression capacitor”). on. The film capacitors 121 are arranged side by side in a horizontal longitudinal direction and between a plus-pole power line 123 and a minus-pole power line 145 in a vertical direction. The film capacitors 121 are electrically connected to the two power lines 123, 145. The power lines 123, 145 are accommodated in a housing 22 of the capacitor arrangement 10. FIG. The positive-pole power line 123 is arranged on an upper edge of the housing 22 and the negative-pole power line 145 is arranged on a lower edge of the housing 22 . A positive power contact 122 extends from the positive power line 123 at the top edge of the housing 22 to the outside of the housing 22, as shown in FIG 2 and in a further end-side sectional view in 4 (right) shown schematically. The electrolytic capacitor 24, which is also accommodated in the housing 22, is electrically connected to the positive-pole power line 123 on the one hand and to a grounding line 28 on the other hand.

The output-side capacitor 14 also has a number of (here by way of example four) film capacitors 141 and a number (here by way of example two) electrolytic capacitors 26 . Here, too, the film capacitors 141 are arranged side by side in the horizontal longitudinal direction and between a positive-pole power line 143 and a negative-pole power line, namely the power line 145 mentioned above, in the vertical direction. The film capacitors 141 are electrically connected to the two power lines 143, 145. In this way, the two capacitors 12,14 share the same negative power line 145 while having separate positive power lines 123,143. The positive-pole power line 143 of the output-side capacitor 14 is arranged at the upper edge of the housing 22 and thus at least in sections opposite the negative-pole power line 145 . this is in 2 and also in an end sectional view 4 (left) shown schematically. The electrolytic capacitors 26 are electrically connected to the positive power line 143, the negative power line 145 and another ground line 30 at the same time.

A plurality of positive power contacts 142 extend out of the housing 22 from the positive power line 143 at the top edge of the housing 22 . Simultaneously, a plurality of negative power contacts 144 extend out of the housing 22 at the top edge of the housing 22 from the negative power line 145, as shown in FIG 2 and 4 shown.

3 shows the capacitor arrangement 10 in a schematic plan view. The positive-pole current contact 126 for connecting to the storage inductor 21 and a further positive-pole current contact 122 for connecting to the DC voltage source 107 are attached to two opposite edges with respect to a horizontal transverse direction. As in 3 no negative-pole current contact is arranged on the input-side capacitor 12 as can be seen. In contrast to this, both positive-pole current contacts 142, 146 and negative-pole current contacts 144, 148 are formed on the capacitor 14 on the output side. The power contacts 142, 144 already described above are designed for connection to the battery 109 to be charged, with these power contacts 142, 144 being lined up alternately between the positive pole and the negative pole. The other two current contacts 146, 148 are designed for connection to the power electronics 20 and preferably extend continuously across the width of the half-bridges of the power electronics 20.

The omission of negative-pole power contacts on the input-side capacitor 12 is made possible by the fact that both capacitors 12, 14 share the same negative-pole power line 145. The negative-pole power line 145 is therefore used for the negative-pole contacting of the film capacitors 141 of both the output-side and the input-side capacitor 12. By eliminating the negative-pole power contact on the input-side capacitor 12, the positive-pole power contacts 122, 126 located outside of the housing 22 have more installation space, so that they can be formed on a large scale. This reduces the current density at the upstream capacitor 12 so that less heat is caused by the current carried by the power contacts 122,126 and power lines 123,145. In addition, the polyphase DC-DC converter 100 can be made more compact overall and can be manufactured with reduced assembly effort.

The housing 22 is preferably encapsulated at least partially around its circumference with an injection molding material in order to protect the components installed in the housing 22 from environmental influences. The film capacitors 121, 141 and electrolytic capacitors 26, 28 of the two capacitors 12, 14 are accommodated in the housing 22. In this way, a combined capacitor arrangement 10 for the voltage input and the voltage output is realized, which achieves additional space savings.

Reference List

10

capacitor array

12

input capacitor

14

output capacitor

20

power electronics

21

storage choke

22

Housing

24, 26

electrolytic capacitor

28.30

ground wires

100

polyphase DC-DC converter

101 A-C

Wash

102A-C

high-side switching devices

103

first filter

104A-C

low-side switching devices

105

second filter

107

DC voltage source

109

battery

121, 141

film capacitors

122, 126, 142, 146

positive power contacts

144, 148

negative power contacts

123, 143

positive power lines

145

negative power line

Claims (11)

Capacitor arrangement (10) for a polyphase DC-DC converter (100) for converting a DC input voltage into a DC output voltage for charging a vehicle battery in an electric vehicle or hybrid vehicle, the capacitor arrangement (10) having an input-side capacitor (12) with first capacitor windings (121) and an output-side capacitor (14) with second capacitor windings (141), which are accommodated in a housing (22) and between which power electronics (20) are connected, with a first of the two capacitors (12, 14) having a positive-pole current contact ( 142) and a negative-pole power contact (144), with each of which a first power line (143, 145) located in the housing (22) is electrically connected, with a second of the two capacitors (12, 14) having a positive-pole or negative-pole power contact (122 ) to which a second power line (123) located in the housing (22) is electrically connected, the power contacts (122, 142, 144) extending out of the housing (22), the first Power line (145) is electrically connected to both the first capacitor windings (121) and the second capacitor windings (141). Capacitor arrangement (10) after claim 1 , wherein one of the two first power lines (143, 145) is arranged in a first edge area of the housing (22), the other of the two first power lines (143, 145) extending from the first edge area to a second edge area opposite the first edge area . Capacitor arrangement (10) after claim 2 , wherein the other of the two first power lines (143, 145) is of opposite polarity to the second power line (123). Capacitor arrangement (10) according to one of Claims 1 until 3 , wherein at least one interference suppression capacitor (24, 26) is electrically connected to the first power lines (143, 145) and/or the second power line (123). Capacitor arrangement (10) according to one of Claims 1 until 4 , wherein the first of the two capacitors (14) has a plurality of positive-pole and/or negative-pole current contacts (142, 144). Capacitor arrangement (10) after claim 5 , wherein the power contacts (142, 144) are lined up alternately between positive pole and negative pole. Multi-phase DC-DC converter (100) for converting a DC input voltage into a DC output voltage for charging a vehicle battery in an electric vehicle or hybrid vehicle, comprising a capacitor arrangement according to one of Claims 1 until 6 . Multi-phase DC-DC converter (100) according to claim 7 , comprising a storage choke having a plurality of windings. Multi-phase DC-DC converter (100) according to claim 7 or 8th , comprising power electronics, which is formed by several half-bridges of an inverter built into an electric axle drive. Electric axle drive for a vehicle, in particular an electric vehicle or hybrid vehicle, comprising a multi-phase DC voltage Voltage converter (100) according to one of Claims 7 until 9 . Vehicle, in particular electric vehicle or hybrid vehicle, comprising an electric axle drive claim 10 .

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