DE102021208353A1 - 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 having 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 multiphase alternating current by switching the semiconductor switching elements to convert, the intermediate circuit capacitor (10) being connected in parallel between the DC voltage source and the semiconductor switching elements and comprising a plurality of film capacitors (102) and/or a plurality of interference suppression capacitors (104), the intermediate circuit capacitor (10) having a plurality of input contacts (110, 112) for connection to the DC voltage source, the input contacts (110, 112) being lined up alternately between positive input contacts (110) and negative input contacts (112).

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 jumps.

The intermediate circuit capacitors known from the prior art have the disadvantage that the current distribution in the intermediate circuit capacitor is uneven. This means that EMC interference from the DC voltage is not adequately counteracted. This also leads to inhomogeneities in the electricity-based heat generation in the intermediate circuit capacitor (temperature hotspots). This impairs the functionality of the intermediate circuit capacitor and, as a result, also of the inverter.

It is an object of the invention to provide an intermediate circuit capacitor for an electric drive of 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 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 comprises several foil capacitors (so-called "windings") and/or several interference suppression capacitors (so-called "Y-capacitors"). In addition, the intermediate circuit capacitor has a number of input contacts for connecting to the DC voltage source. The input contacts are lined up along a longitudinal direction of the intermediate circuit capacitor and form a row of contacts on the input side. The input contacts alternate between positive input contacts and negative input contacts. This means that every positive input contact, except for the last positive input contact of the input-side contact row, between two adjacent negative input contacts is arranged. Conversely, each negative input contact, except for the last negative input contact of the row of contacts on the input side, is also arranged between two adjacent positive input contacts.

In this way, the input contacts are particularly evenly distributed over the length of the intermediate circuit capacitor. In this way, the current can also be evenly distributed throughout the intermediate circuit capacitor. This favors a reduction of the EMC interference of the DC voltage and an even heat generation and distribution over the entire intermediate circuit capacitor. This improves the functionality of the intermediate circuit capacitor.

According to one embodiment, the positive input contacts extend out of a first elongate contact sheet, the negative input contacts extend out of a second elongate contact sheet, the film capacitors and/or interference suppression capacitors being arranged between the first elongate contact sheet and the second elongate contact sheet. The second elongate contact sheet is preferably arranged at least partially parallel to the first elongate contact sheet. This enables a particularly compact design of the intermediate circuit capacitor and lower parasitic leakage inductances.

According to a further embodiment, the positive input contacts are arranged on a first longitudinal edge of the first elongate contact sheet, a positive output contact for connection to the semiconductor switching elements being formed on a second longitudinal edge of the first elongate contact sheet opposite the first longitudinal edge. According to a further embodiment, the negative input contacts are arranged on a first longitudinal edge of the second elongate contact sheet, a negative output contact for connecting to the semiconductor switching elements being formed on a second longitudinal edge of the second elongate contact sheet opposite the first longitudinal edge. This arrangement of the positive and negative input contacts enables the intermediate circuit capacitor to be easily connected to the DC voltage source and to the semiconductor switching elements. To connect to the semiconductor switching elements, an additional intermediate busbar can preferably be welded to the output of the intermediate circuit capacitor.

In accordance with a further embodiment, the negative output contact has a plurality of contact segments which are each assigned to a phase current of the polyphase alternating current. A current path is defined between each positive and/or negative input contact on the one hand and each contact segment of the negative output contact. At least two current paths, more preferably all current paths, are preferably of the same length. This further increases the uniformity of the current distribution within the intermediate circuit capacitor and reduces the EMC interference of the DC voltage and the maximum temperatures that occur. Alternatively, the negative output contact can be welded to a housing of the intermediate circuit capacitor.

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 connections (in particular positive and negative DC power connections) are attached to the intermediate circuit capacitor for feeding in the DC power which is generated on the input side by means of a battery. 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 electrically connected to power contacts integrated in the semiconductor switching elements, for example source electrodes and drain electrodes, or to a ground, so that electrical power can be transmitted from one power connection through a semiconductor switching element to another power connection. The electrical supply of the electric motor for driving the electric vehicle or the hybrid vehicle is ensured via the power connections.

The semiconductor switching elements, the power connections and the signal connections of the respective half-bridge are preferably arranged on a first surface of the substrate. The power connections and the signal connections can be contacted there in a simple manner by external components, in particular busbars (such as busbars). The first surface is preferably one of the two opposite, comparatively largest surfaces of the layered substrate. The first surface defines a main plane of the substrate.

The substrate is preferably cast with a casting compound in an injection molding process. The power connections and/or the signal connections preferably have external sections which consist of a surface towards the first extend orthogonal second surface of the potting compound out to the outside. In this case, the second area is a “side area” of the cast, layered substrate, which is generally significantly smaller than the first area. Preferably, the external portions each have an end extending perpendicular to the first surface. This enables simple electrical contacting of the power connections or the signal connections from outside the half-bridge, in particular from above the power module.

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

• 1 eine schematische Darstellung eines Zwischenkreiskondensators in einer Perspektivansicht;
• 2 eine schematische Darstellung des Zwischenkreiskondensators aus 1 in einer Draufsicht, wobei ein Gehäuse und eine Vergussmasse gezeigt sind.

Show it:

• 1 a schematic representation of an intermediate circuit capacitor in a perspective view;
• 2 a schematic representation of the intermediate circuit capacitor 1 in a plan view showing a housing and a potting compound.

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 an intermediate circuit capacitor 10, 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 includes a number of film capacitors 102, which are also known as windings, and a number of interference suppression capacitors 104, which are also known as Y capacitors. The film capacitors 102 and the interference suppression capacitors 104 are arranged inside the intermediate circuit capacitor 10 between a positive DC busbar and a negative DC busbar. The positive DC bus bar includes a first elongated contact plate 114 that extends along an upper side of the intermediate circuit capacitor 10 . A plurality of positive input contacts 110 are formed on a first longitudinal edge 118 of the first elongated contact sheet 114 and extend laterally from the first elongated contact sheet 114 . The positive input contacts 110 are distributed along the longitudinal direction of the intermediate circuit capacitor 10 and spaced apart from one another. A positive output contact 120 is formed on a second longitudinal edge 122 of the first elongated contact sheet 114 opposite the first longitudinal edge 118 and extends over the entire length of the second longitudinal edge 122 .

The negative DC bus bar includes a second elongate contact plate 116 which extends along an underside of the intermediate circuit capacitor 10 . A plurality of negative input contacts 112 are formed on a first longitudinal edge 124 of the second elongate contact sheet 116 and extend laterally from the second elongate contact sheet 116 . The negative input contacts 112 are also distributed along the longitudinal direction of the intermediate circuit capacitor 10 and are spaced apart from one another in such a way that the positive input contacts 110 and negative input contacts 112 are lined up alternately. Formed on a second longitudinal edge 128 of the second elongated contact sheet 116 opposite the first longitudinal edge 124 is a negative output contact 126 having a plurality of contact segments 130A-C. Each contact segment 130A-C is associated with a phase current of the multi-phase output current.

The positive and negative input contacts 110, 112 are bent in relation to the first and second elongated contact sheets 114, 116 in such a way that they are aligned parallel to the upper side of the intermediate circuit capacitor 10. The positive and negative output contacts 120, 126 also extend essentially parallel to the upper side of the intermediate circuit capacitor 10.

As shown in the schematic top view 2 shown in more detail, the intermediate circuit capacitor 10 has a housing 136 in which the positive and negative DC busbars are accommodated except for the input contacts 110, 112 and the output contacts 120, 126. The input contacts 110, 112 and the output contacts 120, 126 protrude from a surface 138 of the housing 136 to be contacted above the housing 136. FIG. Three screw connections 134, each of which is associated with a screw hole 132 formed on the negative output contact 126, fix the intermediate circuit capacitor on an inverter housing (not shown here).

Reference List

10

intermediate circuit capacitor

102

film capacitor

104

suppression capacitor

110

positive input contacts

112

negative input contacts

114

first elongated contact sheet

116

second elongated contact sheet

118

first longitudinal edge of the first elongate contact sheet

120

positive output contact

122

second longitudinal edge of the first elongate contact sheet

124

first longitudinal edge of the second elongate contact sheet

126

negative output contact

128

second longitudinal edge of the second elongate contact sheet

130A-C

contact segments

130

screw hole

134

screw connection

136

Housing

138

surface

Claims (8)

Intermediate circuit capacitor (10) for an inverter for operating an electric drive in an electric vehicle or a hybrid vehicle, the inverter having 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 multiphase alternating current by switching the semiconductor switching elements to convert, the intermediate circuit capacitor (10) being connected in parallel between the DC voltage source and the semiconductor switching elements and comprising a plurality of film capacitors (102) and/or a plurality of interference suppression capacitors (104), the intermediate circuit capacitor (10) having a plurality of input contacts (110, 112) for connection to the DC voltage source, the input contacts (110, 112) being lined up alternately between positive input contacts (110) and negative input contacts (112). DC link capacitor (10) after claim 1 , wherein the positive input contacts (110) extend out of a first elongate contact sheet (114), wherein the negative input contacts (112) extend out of a second elongate contact sheet (116), wherein the film capacitors (102) and/or interference suppression capacitors (104) are arranged between the first elongate contact plate (114) and the second elongate contact plate (116). DC link capacitor (10) after claim 2 , wherein the second elongate contact plate (116) is arranged at least partially parallel to the first elongate contact plate (114). DC link capacitor (10) after claim 2 or 3 , wherein the positive input contacts (110) are arranged on a first longitudinal edge (118) of the first elongate contact sheet (114), wherein a positive output contact (120) for connection to the semiconductor switching elements is arranged on a second longitudinal edge (122 ) of the first elongate contact sheet (114) is formed. Intermediate circuit capacitor (10) according to one of claims 2 until 4 , wherein the negative input contacts (112) are arranged on a first longitudinal edge (124) of the second elongate contact sheet (116), wherein a negative output contact (126) for connection to the semiconductor switching elements is arranged on a second longitudinal edge (128 ) of the second elongate contact sheet (116) is formed. DC link capacitor (10) after claim 5 , wherein the negative output contact (126) has a plurality of contact segments (130A-C) each associated with a phase current of the polyphase alternating current. DC link capacitor (10) after claim 6 , wherein a current path is defined between each positive and/or negative input contact (110, 112) on the one hand and each contact segment (130A-C) of the negative output contact (126), with at least two current paths, preferably all current paths, being of equal length. Inverter for an electric drive of an electric vehicle or a hybrid vehicle, comprising a power module according to one of Claims 1 until 7 .

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