DE102018005456A1 - DC electrical system for a vehicle - Google Patents

Abstract

The invention relates to DC electrical systems (1), in particular high-voltage DC electrical systems, for a vehicle, comprising a plurality of components (K0 to Kn) which are connected to one another by means of an electrically conductive line set for electrical energy transmission.
According to the invention, cables (3) of the line set are designed between at least two components (K0 to Kn) in such a way that they have an enhanced skin effect.

Description

The invention relates to a DC electrical system for a vehicle according to the features of the preamble of claim 1.

Direct current electrical systems for vehicles are generally known from the prior art. Such DC electrical systems comprise a plurality of components which are connected to one another by means of an electrically conductive wiring harness for the electrical energy transmission. Such direct current electrical systems are designed, for example, as high-voltage direct current electrical systems for electric vehicles, hybrid vehicles and / or fuel cell vehicles and comprise at least one electrical machine for driving the vehicle, also referred to as a traction motor, and at least one battery, i. H. an electrochemical energy store, also referred to as a traction battery, for the electrical energy supply of the at least one electrical machine for driving the vehicle.

In the WO 2005/045853 A1 describes a system for the transmission of electrical energy. In the case of a high-voltage transmission cable for the transmission of alternating current or direct current between two points, at least one of these points being connected to one or more electrical networks, the conductor of the cable has a semiconducting outer layer which contains distributed magnetic particles.

From the DE 199 63 301 A1 a motor cable with ferromagnetic sheathing is known. In IGBT inverters with high switching speed, leakage currents in the power supply cable of the motor and in the motor are reduced by a motor cable in which the electrically conductive wires of the cable are covered with ferromagnetic material.

The invention is based on the object of specifying a DC electrical system for a vehicle which is improved compared to the prior art.

The object is achieved according to the invention by a DC electrical system for a vehicle with the features of claim 1.

Advantageous embodiments of the invention are the subject of the dependent claims.

A DC electrical system, in particular a high-voltage DC electrical system, for a vehicle, in particular for an electric vehicle, hybrid vehicle and / or fuel cell vehicle, comprises a plurality of components which are connected to one another by means of an electrically conductive line set for electrical energy transmission. For example, the DC electrical system comprises as electrical components at least one electrical machine for driving the vehicle, also referred to as a traction motor, and at least one battery, i. H. an electrochemical energy store, also referred to as a traction battery, for the electrical energy supply of the at least one electrical machine for driving the vehicle. As an alternative or in addition to the battery, the electrical energy supply can take place, for example, via another energy source, in particular via another electrochemical energy source, for example via at least one fuel cell.

According to the invention, cables of the line set are designed between at least two components in such a way that they are formed from a combination of a paramagnetic material and a ferromagnetic material, so that they have an enhanced skin effect.

The solution according to the invention solves the problem which arises from the fact that the components have very different performance requirements. As a result, high load scenarios of one component can stress and / or disrupt other components operated in the electrical network. In particular, the performance spectrum of the drive component, i. H. especially the electric traction motor of the vehicle, other components are affected by high AC components. High AC loads generally result in high voltage fluctuations, so-called voltage ripples.

In general, attempts are made to keep the losses in the DC on-board network small by using a low-resistance DC on-board network. However, all the components involved, in particular the battery, of the electrical connection, ie. H. of the DC electrical system, endure AC components and carry AC components that, for example, only by a single powerful main component, in particular by the drive component, d. H. caused by the traction motor. The high AC components burden electrical connection lines, i. H. the cables of the wiring harness, in addition and can also load inputs, for example contacts and / or fuses, and / or input filters, for example chokes and / or capacitors, of other components. This can lead to additional aging, for example.

An interpretation of the electrical DC electrical system is therefore very complex and difficult to achieve in previously known solutions dimension because the properties of all components involved are not known in a design phase. It is also difficult to see that faults in a single component must be borne by other components. Furthermore, components are usually dimensioned for different applications and projects, so that a coordination among the components involved is not possible for all applications or would lead to considerable oversizing of individual, usually simpler, components.

The solution according to the invention solves this problem that ripple currents and ripple voltages occur and stress and / or disrupt individual components in such a low-impedance on-board electrical system, which comprises a plurality of electrical components, in particular a battery and a traction motor, because the inventive one The use of cables with an enhanced skin effect in this DC on-board network means that the wiring harness of the DC on-board network, at least between some of the components of the DC on-board network, is designed such that it can mainly conduct DC currents. The line set or at least these cables is / are designed as a filter, in particular as a frequency-effective filter, for AC components. This means that the electrical resistance of these cables increases with increasing frequency of the ripple current or the ripple voltage.

As a result, the transmission of AC components is damped. The higher the frequency, the greater the damping. This prevents faults in one component, in particular alternating currents, from having a disadvantageous effect on other components of the direct current electrical system. Each component can now be designed independently or at least more independently of the other components with regard to the AC disturbances.

To achieve this, the skin effect is used in the solution according to the invention, as already mentioned. As mentioned, cables are used for this purpose, which are formed from a combination of a paramagnetic material and a ferromagnetic material.

In particular, a core of the cable, in particular formed by one or more electrically conductive wires, consists of a paramagnetic material, for example of copper or aluminum or an alloy with copper and / or aluminum, while a surface, in particular a surface layer, is on or on the core of the individual wire, is formed from a ferromagnetic material, for example from iron or nickel or an alloy with iron and / or nickel. Alternatively or additionally, the use of ferrite components is also conceivable. As a result, a current due to the skin effect with an increasingly higher frequency is pushed more and more to the surface of the respective cable, which has a comparatively high resistance, so that the transmission of AC components is blocked more and more.

The solution according to the invention means that no separate AC filters are required for the individual electrical components of the DC electrical system, so that a cost reduction is achieved. Furthermore, the electrical components of the DC electrical system can be designed independently of each other, since when using this cable set with filter effect for AC currents, each component is responsible for the self-generated disturbances, in particular in the form of AC currents, and other components of the DC electrical system involved, unaffected, depending on the design stay. As a result, individual components of the DC electrical system can be designed independently of the remaining nature of the DC system, since only the direct currents and, depending on the design of the filter effect of the cables, low frequencies of the alternating currents are relevant for the design of the DC electrical system. This gives greater freedom of design for the DC electrical system and its components. Ring currents are also prevented.

Exemplary embodiments of the invention are explained in more detail below with reference to drawings.

• 1 eine schematische Darstellung eines aus dem Stand der Technik bekannten Gleichstrombordnetzes für ein Fahrzeug,
• 2 eine schematische Darstellung einer Ausführungsform eines Gleichstrombordnetzes für ein Fahrzeug,
• 3 eine schematische Darstellung einer weiteren Ausführungsform eines Gleichstrombordnetzes für ein Fahrzeug,
• 4 eine schematische Darstellung des Skin-Effekts, und
• 5 eine schematische Darstellung verschiedener Möglichkeiten der Ausbildung eines Kabels eines Leitungssatzes eines Gleichstrombordnetzes für ein Fahrzeug.

Show:

• 1 1 shows a schematic representation of a DC electrical system for a vehicle known from the prior art,
• 2 1 shows a schematic representation of an embodiment of a DC electrical system for a vehicle,
• 3 1 shows a schematic illustration of a further embodiment of a DC electrical system for a vehicle,
• 4 a schematic representation of the skin effect, and
• 5 is a schematic representation of various ways of forming a cable of a wiring harness of a DC electrical system for a vehicle.

Corresponding parts are provided with the same reference symbols in all figures.

1 shows a schematic representation of a DC electrical system known from the prior art 1 for a vehicle. The DC electrical system 1 comprises a plurality of components which are connected to one another by means of an electrically conductive line set for the electrical energy transmission K0 up to kn The cable set includes conventional electrically conductive cables 2 between the components K0 to Kn, as is the case with such DC power systems known from the prior art 1 be used.

Such a DC electrical system 1 is designed, for example, as a high-voltage direct current electrical system for an electric vehicle, hybrid vehicle and / or fuel cell vehicle and comprises electrical components K0 to Kn at least one electrical machine for driving the vehicle, also referred to as a traction motor, and at least one battery, ie an electrochemical energy store, also referred to as a traction battery, for supplying electrical power to the at least one electrical machine for driving the vehicle. As an alternative or in addition to the battery, the electrical energy supply can take place, for example, via another energy source, in particular via another electrochemical energy source, for example via at least one fuel cell.

The interconnected electrical components K0 to Kn form the electrical DC electrical system 1 , in which the cable set is used to distribute the electrical energy or electrical power. The transmitted electrical power P _{K, el} a component K0 to Kn results from an electrical system voltage U _BN and a DC component I _{K, DC} the component K0 to Kn: $${\text{P}}_{\text{K}.\text{el}}={\text{U}}_{\text{BN}}\cdot {\text{I}}_{\text{K}.\text{DC}}$$

An alternating current component that usually occurs in this case is not used for energy transmission. This AC component usually causes additional electrical losses and leads to components K0 to Kn such as fuses, contacts and capacitors, for undesirable heating and / or aging.

The occurrence of alternating currents is generally accompanied by corresponding alternating voltages. Even with the approach described below, small voltage fluctuations, so-called ripples, cannot be prevented, but they can be greatly minimized. Increased voltage ripples in the power supply pose a challenge to other components K0 to Kn, which in turn have to take into account the level of the input voltage for regulation.

Typical standards are, for example, ± 8V or ± 15V. Experience shows that this voltage ripple greatly depends on the frequency under consideration f are dependent (often a frequency-dependent specification is missing) and these limit values are often exceeded. The design of components is particularly difficult K0 to Kn, which are to be used in very different projects or systems. Future application scenarios are often unknown and therefore cannot be taken into account.

To such malfunctions of components K0 to Kn to avoid or at least reduce by ripple currents or ripple voltages is therefore advantageously provided, connecting lines, ie cables 3 of the wiring harness, between at least two components K0 to Kn, in the simplest case between the energy source, for example the battery, and a sink, for example the electric traction motor, to be designed as a frequency-effective filter, ie the conventional cables known from the prior art 2 through these cables designed as frequency-effective filters 3 to replace. The electrical resistance increases with increasing frequency f noticeably. As a result, the transmission of AC currents is greatly damped, the higher the frequency f , the higher the damping. Ideally, only current changes are transferred for a defined operation (DC resistance R _DC ), for higher frequencies f , for example for frequencies f greater than 500 Hz, blocks the connecting line, ie the cable 3 , the current flow due to the high resistance (AC resistance R _AC ).

2 shows such a DC electrical system 1 , where the cables 3 of the entire line set are designed as such frequency-effective filters. As a result, an AC decoupling of the components is achieved by means of the line set, which has a damping effect on the transmission of AC currents K0 reached until Kn.

With this solution, only the AC components required for the electrical supply have to be transferred from the wiring harness, so that no additional filter in the respective components K0 until Kn is necessary. A fault due to AC ripple among the components K0 to Kn can be avoided, at least to a large extent, that is to say a disturbance, in particular in the form of current ripples, of one component Kn does not produce any disturbing voltage ripples in the other components K0 . K1 . K2 An increased voltage ripple will only result in the component Kn with the disturbance caused by the current ripple. In this respect, only the disruptive component Kn has to tolerate its self-generated disturbances (causer principle).

For the optimal design of each component K0 to Kn regarding a claim for maximum voltage ripple in the DC electrical system 1 the vehicle electrical system impedance must be known and well specified (vehicle electrical system simulation). The one component K0 On-board electrical system impedance visible up to Kn depends on all other components K0 up to Kn including the cable set and falls for each component K0 up to Kn individually. Using a wiring harness whose impedance is related to frequency f increases sharply, this dependency can be reduced accordingly, in the best case even neglected. With regard to such ripples, in particular voltage ripples, the components can K0 to Kn can be interpreted almost independently of one another by the solution described here.

In addition, ring currents in parallel active conductor loops (e.g. shielding of single wires) are avoided. In cable sets whose individual cores (outgoing and return conductors) have a non-negligible distance, induction causes considerable ring currents due to the AC components that occur, for example in the braided shield of the single cores, which is why these ring currents are also called shield currents or shield currents. Since these AC components are suppressed by the solution described here, the ring currents are also avoided.

These advantages of the solution described here outweigh disadvantages, for example due to the resulting additional requirements for the wiring harness, which require a corresponding development, and losses in the form of heating, which are caused by the alternating currents generated by current ripples or voltage ripples depending on the frequency behavior of the wiring harness , by far.

3 shows a further embodiment of such a DC electrical system 1 , here, in contrast to the embodiment according to 2 , not the complete cable set 3 exists, which are designed as frequency-effective filters, but the cables 3 In the example shown, which are designed as frequency-effective filters are only between the components K0 , for example the battery, and the component K1 as well as between the component K0 and the component K2 used while between component K0 As already mentioned, for example the battery, and the component Kn, for example the output, in particular the electric traction motor, the conventional cables 2 be used. This enables the component K0 in the case of compensation of alternating currents caused by component Kn, or vice versa.

In such cases, exemplified in 3 in which a component K0 another component Kn to assist in damping higher-frequency AC components can thus be between these components K0 , Kn continue the conventional cables 2 of the normal line set known from the prior art can be used without a filter effect. Alternatively, the filter effect of the line set can be dimensioned such that alternating currents from the component are present in a desired frequency range K0 be worn. This results in advantages for the design of the component Kn, which causes the alternating currents.

This filter effect of the cables 3 can, for example, be realized with the help of the skin effect, ie the cables 3 the wiring harness between at least two components K0 to Kn are advantageously designed in such a way that they support the skin effect. The skin effect causes the current to flow to the edge of the cable 3 , ie of the electrical conductor, so that a noticeable increase in resistance results due to a greatly restricted cross-sectional area available for the current flow.

For copper lines typically used, this effect is only at noticeably high frequencies f , ie for frequencies f much larger than 1 kHz (f >> 1kHz), as in 4 shown, and therefore too small for the proposed approach. Through the introduction of ferromagnetic materials FM , for example iron Fe or nickel Ni, this effect can be increased by orders of magnitude, as in 4 using the example of iron Fe shown.

4 shows the skin effect, ie the increase in resistance, with increasing frequencies f using the example of pure copper Cu and pure iron Fe as well as a forecast P an idealized course to be aimed for for a material combination of a paramagnetic material PM and a ferromagnetic material FM , for example made of copper Cu and iron Fe , in a frequency-resistance diagram, in which the frequency on the abscissa axis f and on the ordinate axis the quotient of AC resistance R _AC and DC resistance R _DC are worn out. Exemplary values are shown with a cross-sectional area of 50 mm ² and a permeability number for iron Fe µ _{r, FE} = 100.

The use of ferromagnetic materials FM can be done in different ways, as in 5 shown. Here are different ways of using the cable that supports the skin effect 3 the wiring harness of the DC electrical system 1 shown.

The cable 3 is advantageously from a combination of a paramagnetic material PM , for example made of copper Cu or aluminum Al or another good electrically conductive material, and a ferromagnetic material FM , for example made of iron Fe or nickel Ni, in particular made of a material with a permeability number µ _r of much greater than one (µ _r >> 1).

For example, as in 5 shown on the left, a core of the respective cable 3 from the paramagnetic material PM , for example made of copper Cu or aluminum AI, and a surface layer made of the ferromagnetic material FM , for example made of iron Fe or nickel Ni, that is, a sheathing of a conductor, for example a copper conductor or aluminum conductor, which, for example, as shown here, is formed from a plurality of strands, with the ferromagnetic material FM ,

Alternatively, as in 5 Shown above and in an enlargement, the core of each individual strand made of the paramagnetic material PM , for example made of copper Cu or aluminum AI, and a surface layer of the respective strand made of the ferromagnetic material FM , for example made of iron Fe or nickel Ni, be formed, ie a covering of the individual strands with a ferromagnetic material FM or more ferromagnetic materials FM ,

Alternatively, as in 5 Shown below in a bundle of strands made from the paramagnetic material PM , for example made of copper Cu or aluminum AI, strands made of the ferromagnetic material FM , for example made of iron Fe or nickel Ni.

Alternatively, one or more ferromagnetic materials FM and / or ferrimagnetic materials in another way in a conductor made of paramagnetic material PM , in particular in a copper conductor or aluminum conductor.

Also a combination of two or more of the variants mentioned to form the cable 3 is possible.

Aim of this training of the cable 3 it is that for all direct and low frequency currents f the highly conductive material, ie the paramagnetic material PM , for example copper Cu or aluminum AI, which carries electricity and causes the smallest possible transmission losses. All AC currents of higher frequencies f , for example frequencies f greater than 500 Hz, are pushed into the marginal area and by increasing the effective line resistance with increasing frequency f blocked. It is therefore additionally advantageous if the sheathing is formed from a material which is less electrically conductive and which increases the resistance with frequency f favored.

Alternatively or additionally, discrete, additional ferrite components can be used to increase the frequency-dependent inductance of the line.

LIST OF REFERENCE NUMBERS

1

DC vehicle electrical system

2

conventional cable

3

electric wire

Cu

copper

f

frequency

Fe

iron

FM

ferromagnetic material

K0 to Kn

component

P

forecast

PM

paramagnetic material

R _AC

AC resistance

R _DC

DC resistance

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

• WO 2005/045853 A1 [0003]
• DE 19963301 A1 [0004]

Claims (3)

DC electrical system (1), in particular high-voltage DC electrical system, for a vehicle, comprising a plurality of components (KO to Kn) connected to one another by means of an electrically conductive wiring harness for the electrical energy transmission, characterized in that cables (3) of the wiring harness between at least two components (KO to Kn) are formed from a combination of a paramagnetic material (PM) and a ferromagnetic material (FM), so that the cables (3) have an enhanced skin effect. DC electrical system (1) Claim 1 , characterized in that these cables (3) are designed as frequency-effective filters for AC components. DC electrical system (1) Claim 1 or 2 , characterized in that a core of the respective cable (3) made of the paramagnetic material (PM), in particular copper (Cu) or aluminum (AI), and a surface layer made of the ferromagnetic material (FM), in particular iron (Fe) or nickel (Ni) is formed.

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