DE102021208789A1 - Intermediate circuit capacitor for an electric drive of an electric vehicle or a hybrid vehicle, inverter with such an intermediate circuit capacitor - Google Patents

Abstract

Intermediate circuit capacitor (10) for an inverter for operating an electric drive in an electric vehicle or a hybrid vehicle, the inverter comprising a plurality of semiconductor switching elements mounted on a substrate, which are designed to convert a direct current provided by a DC voltage source into a multi-phase direct current by switching the semiconductor switching elements to convert alternating current, the semiconductor switching elements comprising a plurality of half-bridges, each of which is associated with a phase current of the polyphase alternating current, the intermediate circuit capacitor (10) being connected between the DC voltage source and the semiconductor switching elements in parallel with the latter and comprising a plurality of interference suppression capacitors (104), the interference suppression capacitors (104) comprise a plurality of groups each associated with one of the half-bridges.

Description

The invention relates to an intermediate circuit capacitor for an inverter of an electric drive of an electric vehicle or a hybrid vehicle and a corresponding inverter.

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 electric machines of such electric vehicles or hybrid vehicles with electric energy, the electric vehicles and hybrid vehicles include electric energy stores, in particular rechargeable electric batteries. These batteries are designed as DC voltage sources, but the electrical machines usually require an AC voltage. Therefore, power electronics with a so-called inverter are usually connected between a battery and an electric machine of an electric vehicle or a hybrid vehicle.

Such inverters typically include semiconductor switching elements typically formed of transistors. It is known to provide the semiconductor switching elements in different degrees of integration, namely either as discrete individual switches with a low degree of integration but high scalability, as power modules with a high degree of integration but low scalability, and as half-bridges, which in terms of degree of integration and scalability between individual switches and half-bridges rank Each half-bridge includes a high-side switch position (hereinafter: "highside") with a higher electrical potential and a low-side switch position (hereinafter: "lowside") with a lower electrical potential. The high side and the low side can each include one or more individual switches/semiconductor switching elements that are connected in parallel.

An intermediate circuit capacitor connected in parallel in the inverter is provided for the semiconductor switching elements or the half-bridges. The intermediate circuit capacitor is used to smooth the DC-side input voltage in order to reduce voltage overshoots.

The intermediate circuit capacitors known from the prior art have the disadvantage that EMC interference occurs in the DC voltage. In particular, there were two modes of EMC interference, namely a so-called differential mode (DM) and a so-called common mode (CM). These two modes of interfering signals can even be coupled to one another by mode conversion of the DM interfering signal into the CM interfering signal or vice versa.

It is an object of the invention to provide an intermediate circuit capacitor for an inverter for energizing an electric drive in an electric or hybrid vehicle, in which the disadvantages mentioned above are at least partially overcome.

According to the invention, this object is achieved by the intermediate circuit capacitor and the inverter according to the independent patent claims. Advantageous refinements and developments of the invention emerge from the dependent patent claims.

The invention relates to an intermediate circuit capacitor for an inverter for energizing an electric drive in an electric vehicle or a hybrid vehicle. The inverter includes a plurality of semiconductor switching elements which are designed to convert an input-side DC current into an output-side multi-phase AC current with a plurality of phase currents by switching the semiconductor switching elements. Provision is preferably made for the semiconductor switching elements to be in the form of bipolar transistors with an insulated gate electrode (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs). A so-called wide bandgap semiconductor, such as gallium nitride (GaN) or silicon carbide (SiC), can be used as the semiconductor material on which the semiconductor switching elements are based. These types of semiconductor switching elements are comparatively well suited for low-loss and fast switching.

The intermediate circuit capacitor according to the invention is connected in parallel to the inverter for energizing an electric drive in an electric vehicle and/or a hybrid vehicle between the DC voltage source (such as a battery) and the semiconductor switching elements. In addition, an EMC filter can be connected between the DC voltage source and the intermediate circuit capacitor to eliminate interference signals in the DC voltage provided by the DC voltage source.

The intermediate circuit capacitor includes several interference suppression capacitors (so-called “Y capacitors”). The intermediate circuit capacitor preferably also includes a number of film capacitors (so-called “windings”). According to the invention, the interference suppression capacitors comprise a number of groups, each of which contains one or more interference suppression capacitors, each of which has a positive pole and a negative pole. The positive pole is at a positive potential of the DC voltage Source (z. B. battery) acted upon, the negative pole with a negative potential of the DC voltage source can be acted upon. The various groups of interference suppression capacitors are each assigned to one of the half-bridges. This means that the various groups of interference suppression capacitors are each assigned a fixed assignment to a half-bridge and, as a result, also to a phase current. This allows EMC interference to be eliminated or compensated for more effectively. A more symmetrical arrangement of the interference suppression capacitors also enables decoupling between the DM interference signals and the CM interference signals.

In accordance with one embodiment, the intermediate circuit capacitor has a plurality of output contacts for connection to the half-bridges, with the output contacts each being assigned to one of the half-bridges. The half bridges can thus be connected separately to the intermediate circuit capacitor.

According to a further embodiment, the output contacts extend laterally from a first longitudinal edge of a first contact sheet and/or a negative contact sheet to the half-bridges, with the groups of interference suppression capacitors each being arranged vertically above an associated output contact. Thus, the groups of interference suppression capacitors are in the immediate vicinity of the associated output contacts and thus also the associated half-bridges. This improves the interference suppression property with regard to EMC interference.

According to a further embodiment, the first contact plate can be charged with a positive potential of the DC voltage source via a positive input contact, wherein the second contact plate can be charged with a negative potential of the DC voltage source via a negative input contact, with the positive input contact and the negative input contact extend laterally away from the half-bridges from a second longitudinal edge of the first contact sheet or the negative contact sheet. The first contact plate and the second contact plate can form two mutually opposite sides, preferably an upper side or an underside of the intermediate circuit capacitor, it being possible for the film capacitors to be arranged between the first contact plate and the second contact plate.

According to a further embodiment, the positive input contact and/or the negative input contact have an extension for connecting the DC voltage source or an EMC filter connected between the latter and the intermediate circuit capacitor, the extension having a first section parallel to the second longitudinal edge and a first section to the first section includes curved second portion. In this way, the DC voltage source (or the battery) can be connected to a transverse edge of the intermediate circuit capacitor running perpendicularly to the longitudinal edges, which makes it easier to connect to a correspondingly placed battery.

According to a further embodiment, a corresponding interference suppression capacitor is arranged vertically above each of the output contacts. In this way, the total capacitance of the interference suppression capacitors can be distributed more evenly to the half-bridges or phases. This improves the elimination of the EMC interference. According to a further embodiment, at least one of the groups includes two interference suppression capacitors. This improves the anti-interference properties of the intermediate circuit capacitor.

According to a further embodiment, the two interference suppression capacitors are grounded via a grounding part arranged between them. In the context of this invention, “grounding” means a chassis contact and/or a heat sink contact. Such a grounding part thus connects the interference suppression capacitors to a chassis and/or heat sink housing. This enables the interference suppression capacitors to be contacted in a simple manner.

According to a further embodiment, at least one of the interference suppression capacitors is assigned to two of the half-bridges at the same time. The number of interference suppression capacitors required can thus be reduced. The cost of manufacturing the intermediate circuit capacitor and, as a result, also the inverter can be reduced.

The invention also relates to an inverter for an electric drive of an electric vehicle or a hybrid vehicle with such an intermediate circuit capacitor. This results in the advantages already described in connection with the intermediate circuit capacitor according to the invention for the inverter according to the invention as well.

A plurality of DC power terminals (particularly a positive and a negative DC power terminal) are attached to the inverter for feeding the DC power generated by a battery on the input side. At the same time, a number of AC power connections are provided for delivering the AC power generated by means of the semiconductor switching elements. The power connections are in turn equipped with power contacts integrated in the semiconductor switching elements, e.g. source electrodes and drain Electrodes electrically connected so that electrical power can be transmitted from one power terminal through a semiconductor switching element to another power terminal. The electrical supply of the electric motor for driving the electric vehicle or the hybrid vehicle is ensured via the power connections.

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

• 1 eine schematische Darstellung eines Zwischenkreiskondensators gemäß einer allgemeinen Ausführungsform in einer Draufsicht;
• 2 eine schematische Darstellung eines Zwischenkreiskondensators gemäß einer weiteren Ausführungsform in einer Perspektivansicht;
• 3 eine schematische Darstellung eines Zwischenkreiskondensators gemäß einer weiteren Ausführungsform in einer Perspektivansicht;
• 4 eine schematische Darstellung des Zwischenkreiskondensators aus 2 und 3 in einer weiteren Perspektivansicht.

Show it:

• 1 a schematic representation of an intermediate circuit capacitor according to a general embodiment in a plan view;
• 2 a schematic representation of an intermediate circuit capacitor according to a further embodiment in a perspective view;
• 3 a schematic representation of an intermediate circuit capacitor according to a further embodiment in a perspective view;
• 4 a schematic representation of the intermediate circuit capacitor 2 and 3 in another perspective view.

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 FIG. 1 shows an intermediate circuit capacitor 10 according to a general embodiment, which is connected in an inverter between a DC voltage source (such as a battery) and a plurality of semiconductor switching elements arranged in the inverter. The inverter is used to power an electric drive in an electric vehicle or a hybrid vehicle. The semiconductor switching elements form a plurality of half-bridges, each associated with a phase current of an alternating current (AC current) generated by the inverter from direct current (DC) voltage provided by the DC voltage source.

The intermediate circuit capacitor 10 comprises a plurality of film capacitors 105, which are also known as windings and are 1 are shown as a rectangle for the sake of clarity. In the perspective view in 4 the film capacitors 105 are shown in more detail. The intermediate circuit capacitor 10 also includes a number of interference suppression capacitors 104, which are also known as Y capacitors. The intermediate circuit capacitor 10 also includes a positive DC busbar (DC busbar) and a negative DC busbar. The positive DC busbar includes a first contact sheet 114 which extends on top of the intermediate circuit capacitor 10 . The first contact plate 114 extends between two longitudinal edges 117, 121 running essentially parallel to one another. A plurality of positive output contacts 110A-C extend out of the first contact plate 114 at a first longitudinal edge 117. A positive input contact 120 extends out of the first contact plate 114 at a second longitudinal edge 121 . The negative DC busbar includes a second contact plate 116 (see FIG 4 ), which extends below the intermediate circuit capacitor 10. The second contact plate 116 also extends between two longitudinal edges 123 running essentially parallel to one another. A plurality of negative output contacts 112A-C extend out of the second contact plate 116 at a first longitudinal edge (not shown here). A negative output contact 122 extends out of the second contact plate 116 at a second longitudinal edge 123 . The positive input contact 120 and the negative input contact 122 are configured to connect a DC voltage source (not shown) such as a battery. The positive input contact 120 and thus also the first contact plate 114 and the positive output contacts 110A-C are subjected to a positive potential of the DC voltage source during operation of the inverter. The negative input contact 122 and thus also the second contact plate 116 and the negative output contacts 112A-C are subjected to a negative potential of the DC voltage source during operation of the inverter.

The output contacts 110A-C, 112A-C are designed to make contact with the semiconductor switching elements on the input side and to feed the DC current, which is generated by the DC voltage source, into the respective half-bridges. The output contacts 110A-C, 112A-C are each associated with a phase current of the polyphase alternating current. A first pair of output contacts 110A, 112A are associated with a first phase current. A second pair of output contacts 110B, 112B are associated with a second phase current. A third pair of output contacts 110C, 112C are associated with a third phase current.

The interference suppression capacitors 104 are each assigned to a phase current of the polyphase alternating current. As in 1 shown schematically and purely by way of example, four interference suppression capacitors 104 are each arranged vertically above one of the output contacts 110A-C, 112A-C. This way of arranging the interference suppression capacitors 104 enables a comparable, sometimes even the same distance between the interference suppression capacitors ren 104 and the respective associated half-bridges. This brings about a balancing of the impedances in the structure, so that the same capacitance of the interference suppression capacitors 104 is assigned to all half-bridges or phases. The anti-interference property of the intermediate circuit capacitor 10 is improved as a result.

2 and 3 each show an intermediate circuit capacitor 10A, 10B according to a specific embodiment. In both embodiments, the first contact plate 114 has a folded shape that includes four surface sections 1142, 1144, 1146, 1148 that are bent toward one another. The second contact plate 116 also has a folded shape corresponding to the first contact plate 114 . The output contacts 110A-C, 112A-C are off as shown in FIG 3 and 3 each frontmost surface portion 1148 of the first and second contact sheet 114, 116 is arranged. The input contacts 120, 122 extend from the second longitudinal edge 121, 123 of the first and second contact sheet 114, 116, initially parallel to the second longitudinal edge 121, 123 as a first section 125, 127 and then perpendicular to the second longitudinal edge 121, 123 as a second section 128, 129. The DC voltage source can thus be connected to a transverse edge that is curved or perpendicular to the longitudinal edge 117, 121, 123. An insulation layer 111 is arranged between the first contact plate 114 and the second contact plate 116 in order to ensure potential isolation between the positive DC busbar and the negative DC busbar.

The two embodiments 2 and 3 differ essentially by the number and arrangement of the interference suppression capacitors 104. In the embodiment 2 For example, four interference suppression capacitors 104 are arranged on two central surface sections 1144, 1146 of the first contact sheet 114. In this case, two interference suppression capacitors 104 are connected by means of a common grounding part 130 to a screw 138A-C to which the ground potential is applied. Two wires 132, which protrude from two surfaces of the two suppression capacitors 104 facing one another, are used for this purpose. The grounding part 130 is electrically isolated from the first contact plate 114 by means of an insulating film 137 fastened between it and the first contact plate 114 . Two further wires 136 are used to apply the positive potential present at the first contact sheet 114 or the negative potential present at the second contact sheet 116 to the suppression capacitors 104 . The one in the drawing by 2 The left-most interference suppression capacitor 104 is assigned to the half-bridge to which the output contacts 110A, 112A are assigned. The one in the drawing by 2 The right-most interference suppression capacitor 104 is associated with the half bridge to which the output contacts 110C, 112C are associated. The one in the drawing by 2 Left inner interference suppression capacitor 104 is partially associated with the half-bridge associated with the output contacts 110A, 112A and partially associated with the half-bridge associated with the output contacts 110B, 112B. The one in the drawing by 2 Right-inner interference suppression capacitor 104 is partially associated with the half-bridge associated with output contacts 110C, 112C and partially associated with the half-bridge associated with output contacts 110B, 112B.

In the embodiment off 3 on the other hand, six interference suppression capacitors 104 are provided, which form three groups each with two interference suppression capacitors 104 . Each group is assigned to a half bridge. The group of interference suppression capacitors 104 on the left in the drawing is assigned to the half-bridge to which the output contacts 110A, 112A are assigned. The middle group of interference suppression capacitors 104 in the drawing is assigned to the half-bridge to which the output contacts 110B, 112B are assigned. The group of interference suppression capacitors 104 on the right in the drawing is assigned to the half-bridge to which the output contacts 110C, 112C are assigned.

Reference List

10, 10A,B

intermediate circuit capacitor

104

suppression capacitor

105

film capacitor

110A-C

positive output contact

111

insulation layer

112A-C

negative output contact

114

first contact plate

1142, 1144, 1146, 1148

surface sections

116

second contact plate

117

first longitudinal edge

120

positive input contact

121, 123

second longitudinal edge

122

negative input contact

125, 127

first section

128, 129

second part

130

grounding part

132

first wire

136

second wire

137

insulation film

138A-C

screws

Claims (10)

Intermediate circuit capacitor (10) for an inverter for operating an electric drive in an electric vehicle or a hybrid vehicle, the inverter comprising a plurality of semiconductor switching elements mounted on a substrate, which are designed to convert a direct current provided by a DC voltage source into a multi-phase direct current by switching the semiconductor switching elements to convert alternating current, the semiconductor switching elements comprising a plurality of half-bridges, each of which is associated with a phase current of the polyphase alternating current, the intermediate circuit capacitor (10) being connected between the DC voltage source and the semiconductor switching elements in parallel with the latter and comprising a plurality of interference suppression capacitors (104), the interference suppression capacitors (104) comprise a plurality of groups each associated with one of the half-bridges. DC link capacitor (10) after claim 1 , wherein the intermediate circuit capacitor (10) has a plurality of output contacts (110A-C, 112A-C) for connection to the half-bridges, wherein the output contacts (110A-C, 112A-C) are each associated with one of the half-bridges. DC link capacitor (10) after claim 2 , wherein the output contacts (110A-C, 112A-C) extend laterally from a first longitudinal edge (117) of a first contact sheet (114) and/or a negative contact sheet (116) to the half bridges, wherein the groups of interference suppression capacitors (104 ) are each arranged vertically above an associated output contact (110A-C, 112A-C). DC link capacitor (10) after claim 3 , wherein the first contact plate (114) can be charged with a positive potential of the DC voltage source via a positive input contact (120), wherein the second contact plate (116) can be charged with a negative potential of the DC voltage source via a negative input contact (122). , wherein the positive input contact (120) and the negative input contact (122) extend from a second longitudinal edge (121, 123) of the first contact sheet (114) or the negative contact sheet (116) laterally away from the half-bridges. DC link capacitor (10) after claim 4 , wherein the positive input contact (120) and/or the negative input contact (122) have an extension (124, 126) for connecting the DC voltage source or an EMC filter connected between the latter and the intermediate circuit capacitor (10), the extension ( 124, 126) comprises a first portion (125, 127) parallel to the second longitudinal edge (121, 123) and a second portion (128, 129) bent to the first portion (125, 127). Intermediate circuit capacitor (10) according to one of claims 3 until 5 , wherein a corresponding interference suppression capacitor (104) is arranged vertically above each of the output contacts (110A-C, 112A-C). Intermediate circuit capacitor (10) according to one of Claims 1 until 6 , wherein at least one of the groups comprises two interference suppression capacitors (104). DC link capacitor (10) after claim 7 , wherein the two interference suppression capacitors (104) are grounded via a grounding part (130) arranged between them. Intermediate circuit capacitor (10) according to one of Claims 1 until 8th , At least one of the interference suppression capacitors (104) being assigned to two of the half-bridges at the same time. Inverter for an electric drive of an electric vehicle or a hybrid vehicle, comprising a power module according to one of Claims 1 until 9 .

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