WO2020070115A1

WO2020070115A1 - Device for non-contact inductive energy transfer, in particular for inductive charging processes in motor vehicles

Info

Publication number: WO2020070115A1
Application number: PCT/EP2019/076570
Authority: WO
Inventors: David Maier; Felix Klein; Nejila Parspour
Original assignee: Universität Stuttgart
Priority date: 2018-10-02
Filing date: 2019-10-01
Publication date: 2020-04-09
Also published as: DE102018216916A1

Abstract

The present invention relates to a device for non-contact inductive energy transfer, in particular for inductive charging processes in motor vehicles, which device comprises a primary coil arrangement and power electronics connected to the primary coil arrangement and configured for energy transfer via the primary coil arrangement. In this case, the primary coil arrangement comprises a plurality of individual coils (A, B, C) and capacitances, which are interconnectable to form different primary circuits via one or more switching devices (S₁, S₂) of the primary coil arrangement. The primary circuits are tuned to the same resonant frequency and each comprise one of the individual coils (A, B, C) or a series connection of a plurality of the individual coils (A, B, C). The proposed device makes it possible to supply different types of vehicles having different ground clearances with energy inductively in a non-contact manner, wherein charging power and also current and voltage levels remain the same here at the operating point.

Description

Device for contactless inductive

Energy transmission, especially for inductive

Charging processes in motor vehicles

Technical application area

The present invention relates to a

Device for contactless inductive energy

Transmission, in particular for inductive charging processes in motor vehicles, which has a primary coil arrangement and one connected to the primary coil arrangement

Power electronics, which for the

Energy transmission is formed via the primary coil arrangement. The invention also relates to a

Process for contactless inductive energy

transfer with the proposed facility.

Inductive energy transmission is a contactless transmission technology that is used, for example, to charge the battery of an electric vehicle

can be used. Here are the

Primary coil in the floor of a parking space and the

Secondary coil on the underbody of the vehicle. One problem with this contactless energy transmission, especially in the motor vehicle sector, is the different distances between the coils due to different vehicle classes. This leads primarily to different ones

Coupling factors and accordingly different operating behavior. The SAE standard J2954 specifies three different z-classes at a distance of 100mm to 250mm. State of the art

Previous systems for contactless inductive energy transmission are designed for a specific coupling factor of the coil. Because the coupling factor changes with the distance between

Primary coil and secondary coil reduced or

enlarged, this leads to deviations in the operating point. Deviations mean that the charging power fluctuates and the voltage level or current change. The deviations from the intended

If the operating point is too large, the operational safety can be impaired, so that the charging device must be switched off. To avoid this problem in the area of

Motor vehicles are known to suitably regulate the primary and secondary circuits. So at

changed coupling factor, for example, the input voltage can be adjusted or the output voltage.

The disadvantage here is that with these methods either the charging power, the efficiency or the voltage do not remain constant and that additional control in the system is also required. Another known technique for avoiding the above problem is to compensate for the different distance by means of a mechanically movable primary side. The primary coil is raised or lowered accordingly using an actuator. So the same charging power is the same

Current strength and equal voltage levels possible. A disadvantage here, however, is the mechanics required for this, which must be maintained regularly. The object of the present invention is to provide a device for contactless inductive energy transmission which, without mechanically moving parts, has a constant charging power and constant voltage level, even at predetermined ones

different distances between primary and

Secondary coil enables.

Presentation of the invention

The task is carried out with the facility

contactless inductive energy transmission according to

Claim 1 solved. Advantageous embodiments of the device are the subject of the dependent

Claims or can be found in the following description and the embodiment. Claim 8 specifies a method for contactless inductive energy transmission with the proposed device.

The proposed facility has one

Primary coil arrangement and a power electronics connected to the primary coil arrangement, which is designed for energy transmission via the primary coil arrangement, which thus supplies it with a suitable AC voltage. The power electronics can have a DC voltage source and an inverter in a known manner. The proposed facility is characterized in that the

Primary coil arrangement one or more switching devices and several individual coils and capacities has, via the one or more switching devices to different primary circuits

are interconnectable. These primary circuits each comprise only one or a series connection of several of the

Individual coils and are each tuned to the same resonance frequency.

Different arrangements can thus be made in the primary coil arrangement of the proposed device

Combinations of single coils to primary circuits

interconnect so that the different primary circuits have different inductances. By appropriate dimensioning of the individual coils and

Capacitors is thus made possible with only one primary power electronics and the

Primary coil arrangement to supply different types of vehicles with different ground clearances (z-classes) contactless inductively with energy by switching to the appropriate combination of individual coils. Charging power as well as electricity and

Voltage levels remain the same at the operating point. This only assumes that the inductances of the secondary coils in the respective vehicle classes and the inductances of the different primary circuits match the different distances or

Coupling factors are coordinated, as will be explained in more detail below.

In an advantageous embodiment of the

proposed device, the primary coil arrangement has at least a first, a second and a third individual coil with different inductances. A first of the different primary circles includes only the first single coil, the second primary circuit a series circuit of the first and second single coil and the third primary circuit a series circuit of the first, second and third single coil. This is achieved by suitable interconnection with the help of the switching devices. In this way it is possible to switch between three primary circuits, each of which has a different inductance. By connecting several individual coils in series, high inductivities can be generated without having to use large individual coils.

When operating the proposed device for inductive energy transmission to secondary circuits in motor vehicles, different secondary coils must be installed in vehicles of different vehicle classes. Each of the primary circuits of the proposed device is dimensioned such that it covers a certain coupling factor, so that depending on the vehicle or vehicle class, the corresponding primary-side coil combination or the corresponding one

Primary circuit is switched.

The functioning of the proposed device or the associated method can be shown using the following equation. The equations for

Output power P, characteristic resistance R2 _, c and voltage transfer function M ₀ result from serial compensation of the primary and secondary circuit:

It can be seen from the equations that Li and k as well

and k are in the same ratio, k corresponds to the coupling factor, Li and L ₂ the

Inductance of the coils or coil combination in

Primary circuit and in the secondary circuit. In the proposed method, primary circles and secondary circles are dimensioned such that the three terms for all

predetermined coupling factors or distances between the primary and secondary coils remain constant. Thus, if the coupling factor k is increased in the case of serial compensation of the primary circuit and the secondary circuit, the inductance Li and the inductance L _{2 must} be chosen correspondingly lower than with a smaller coupling factor (k † => Lij. L _{2 |} - k => Li † L ₂ f). Vehicles with a smaller distance to the ground (and thus a correspondingly higher coupling factor) therefore receive a secondary coil with a lower inductance and the primary circuit to be switched accordingly is operated with only a single coil or a combination of fewer individual coils with a low inductance. In principle, the Li required for the respective coupling factor can be determined, for example, from the equation for P and the required L ₂ from the equation for R ₂ , c or M ₀ . The inductivities of the individual coils of the primary coil arrangement are then selected such that the different LI (for the different coupling factors) can be combined appropriately

Single coils (including the use of only one of the Single coils) can be obtained with the help of the switching device (s).

In this way it is achieved that, for example, for three different distances or vehicle classes and thus three different coupling factors, the output power, the characteristic resistance and the voltage transfer function remain constant by appropriately switching the primary coil arrangement. This enables the same

Charging power at the same current and voltage levels for all three vehicle classes with the proposed device, which works without mechanically moving parts or corresponding regulations of the primary and secondary electronics.

The different primary circles and the

respective secondary circuit can be compensated either in series or in parallel. If the primary circuits are serially compensated, the secondary circuit must also be serially compensated. If the primary circuits are compensated in parallel, the secondary circuit must also be compensated in parallel. In the case of a bilateral

Parallel compensation arises from the then given equations for P, R2 _, c and M ₀ , that if the coupling factor is increased, the inductances of the primary circuit and the secondary circuit also increase and if the coupling factor is reduced

Coupling factor must be reduced (k _† => Li † L2 † - kj => LL _{2 |)} .

Serial compensation of the primary circuits also has the advantage that each of the Individual coils have a suitable capacity in series

can be connected, so that with a

Series connection of several of the individual coils between the individual coils each has at least one capacitance. Such a division of the capacities over the primary coil arrangement is advantageous to high

Distribute reactive voltages, especially with small coupling factors, i.e. a large distance and large inductance, over the entire coil arrangement. The

Connection ends of the series connected

Coil arrangement thus do not have the whole

Reactive voltage, which can be several kV.

In a preferred embodiment, the

Primary coil arrangement designed or designed so that the (primary-side) individual coils have the highest possible coupling of k> 0.9 with one another. For this purpose, the individual coils of the primary coil arrangement are preferably arranged one above the other in order to achieve the greatest possible coupling factors between these individual coils. These are preferably coils wound flat. This arrangement takes advantage of the fact that the number of turns with a high internal coupling squares into the coil inductance

flows in. This makes it possible to use smaller coils

Number of turns and thus lower material consumption achieve higher inductances.

The proposed device and the associated method are particularly suitable for contactless energy transmission in the field of motor vehicles. However, the device and the method can also be used to transfer energy to other objects use, where a similar problem

different distances or coupling factors

is present.

Brief description of the drawings

The proposed device is explained in more detail below using an exemplary embodiment in conjunction with the drawings. Here show:

Fig. 1 shows an example of the conditions in the

Energy transfer for three different coupling factors according to the prior art;

Fig. 2 shows a circuit diagram of a device for

contactless inductive power transmission according to the present invention;

Fig. 3 shows a schematic illustration of the primary coil arrangement and the secondary coil in a device according to the present invention;

Fig. 4 is a plan view of the primary coils

arrangement of Figure 3 and a

Representation of the individual coils of these

Primary coil arrangement; and

Fig. 5 shows a circuit diagram of a further device for contactless inductive energy transmission according to the present invention.

Ways of Carrying Out the Invention

In previous systems that are only designed for a specific coupling factor of the coils, A change in the distance between the primary coil and the secondary coil results in deviations from the operating point, which lead to a change in the charging power and the voltage level or current. Figure 1 shows an example of three different ones

Coupling factors based on a diagram that the

Voltage transfer function U ₂ / Ui depending on the resistance of the secondary side R ₂ shows. Ui and U ₂ here represent the input voltage U ₂ and the output voltage U ₂ , L ₂ and L ₂ in turn the inductance in the

Primary circuit and the inductance in the secondary circuit. Ki, k ₂ and k ₂ are the three different

given coupling factors, ar the design or

Resonance frequency. Typical operating areas are marked with hatched areas in the figure. The optimal operating point (R = R _{2, C)} corresponding to the best efficiency in the coil system with reactive power compensation is marked with a circle. If the deviations from the intended operating point become too large, the operational safety can be impaired.

In the proposed device, larger deviations from the operating point with different coupling factors are avoided by switching between the individual primary circuits. Figure 2 shows an example of an embodiment of the proposed device. The figure shows the input voltage Ui _{, D} cv via an inverter into a suitable one

AC voltage U is converted. With this

AC voltage is applied to the primary coil arrangement 1 of the proposed device, which in the present example consists of three coils with the Inductors Li _a , Li _b and Li _c and the associated capacitors Ci _a , Ci _b and Ci _c connected in series is formed. Two switching devices S _b and S2, with which different primary circuits can be switched in the primary coil arrangement, are arranged between these individual components consisting of coil and capacitor. The first primary circuit here consists only of the first primary coil with the inductance Li _a and the capacitance Ci _a . The second primary circuit is connected in series with the first two coils

Inductors Li _a and L _bb and the associated

Capacities Ci _a and C _bb formed. The third primary circuit is formed by connecting all three coils and capacitors in series. The individual primary circuits are compensated for the same design frequency co _b by the corresponding capacitances. Figure 2 shows the overall system, ie also the secondary side with the secondary coil L2 _X , the capacitor in the secondary circuit C2 _X , the inverter, the load-side capacitance C _D c2 and the load-side resistor R2, _DCV, for example, by the vehicle battery to be charged

Motor vehicle can be formed. In the example shown, the primary circuit and secondary circuit are each compensated in series. For the charging of vehicles of different distance classes there is one or more of each primary circuit

Individual coils Li _x a secondary coil L2 _X , which is suitable for the respective inductance of the primary circuit.

This coil L2 _X is installed in the vehicle depending on the distance class. Each of the n individual coils on the primary side, individually or in series with one or more other of the individual coils, covers a certain coupling factor. Depending on the vehicle to be loaded, one is then suitable primary-side coil combination as

Primary circuit switched.

The coordination between the different vehicle classes or distance classes and the

Primary circuits, which can be switched in the device, are carried out with the equation system already mentioned above in such a way that output power, characteristic resistance and voltage transmittance for the different vehicle classes or distance classes

load function remain constant.

With a high coupling factor, i.e. low

The distance from the motor vehicle to the ground must be

primary inductance should be small. The coils Li _b and Li _c and their capacitors are not switched in this example. A suitable small inductor on the secondary side is then also installed in the motor vehicle. If the coupling factor increases, ie the distance between the motor vehicle and the ground is large, the inductance on the primary side must be correspondingly larger. A suitable larger inductor on the secondary side is then also installed in the motor vehicle of this distance class. Now based on the

Distance with the help of the switching devices Si, S2 either only a series connection of Li _a and Li _b or a series connection of Li _a , L _bb and Li _c in the

Primary side interconnected with their capacitors. Since the values for the three equations above remain constant, P, R2 _{, c} and M _b do not change.

The resonance frequencies of both systems, i. H.

The primary side and secondary side remain constant on the currently typical 85 kHz or 140 kHz, for example. This is achieved by compensating each individual coil with a suitable capacitance in such a way that the same resonance frequency is obtained in total. The relationship is inversely proportional with serial compensation on both sides. Therefore, if the inductance increases due to a series connection, the capacitance must be reduced. This also works advantageously with serial compensation using a

Series connection of the capacitors. The total resonance frequency then remains constant.

Since the number of turns flows squarely into the coil inductance with a high internal coupling (L = magnetic conductance x number of turns ² ), the unconnected individual coils on the primary side (Li _b with Ci _b etc.) are not in resonance and there can be no effective power transmission to them wired

Single coils take place. This is a positive one

Side effect, since the line ends are not

wired single coil (s) are preferably open, ie not short-circuited, and none anyway

Power transmission should take place. The unconnected individual coils are therefore through the

respective switch or the respective switching device preferably open so that no voltage can be induced. Without resonance, there are no high reactive voltages in the non-connected ones

Individual coils of the primary coil arrangement.

When designing the primary coil arrangement, care is preferably taken to ensure that the

primary-side individual coils as high as possible Have coupling with each other. this will

preferably achieved by arranging the individual coils one above the other, as is shown schematically in FIG. 3. This figure shows the

Primary coil arrangement with the coils A, B and C of the inductors Li _a , Li _b and Li _c arranged above one another and the coil D on the secondary side with the inductor L2 _a spaced therefrom. The individual coils of the

The primary side is arranged above the radius r of a radial flat winding. This works with

any coil topologies. With a high

Coupling factor within the primary side is the

required coil length shortened, resulting in a

Cost savings leads, the above relationship between the inductance L and the number of turns applies. A high coupling factor of preferably k> 0.9 between the individual coils of the primary coil arrangement can also be achieved by other measures, so that the individual coils do not necessarily have to be arranged one above the other for this purpose.

Figure 4 shows a plan view of a

exemplary coil arrangement according to FIG. 3, in which the three individual coils A, B and C can be seen. In the lower part of the figure, the three coils A, B, C are for

easier to recognize next to each other

shown.

Figure 5 shows another example of a

Design of the proposed device in which the primary and secondary circuits are compensated in parallel. In contrast to the embodiment in FIG. 2, a choke coil L _DRI , L _DR 2 must be inserted between each The voltage source and inverter on the primary side and between the inverter and the load on the secondary side. The parallel compensation also makes two additional ones in this example

Switching devices S ₃ , S ₄ in the primary coil arrangement 1 are required in order, for example, to be able to switch all three capacitances Cla, Clb and Clc in parallel when only the first coil Lla is in operation, while only the first capacitance Clc is required when all three coils are connected in series.

With an exemplary dimensioning of the device according to FIG. 2 for a power P of 50W and input and output voltages of 28V, with corresponding distances zi = 4 cm, _Z2 = 6 and _Z3 = 10 cm and the resulting coupling factors ki = 0.36, k ₂ = 0.2 and k ₃ = 0.1 values for the coils and

Capacitors of Li _a = 41.4 mH, Li _b = 5.7 mH, Li _c = 13.9 mH, Ci _a = 30.1 nF, C _ib = 37.6 nF and Ci _c = 16.7 nF were determined , whereby values of k _xy > 0.9 were used for the coupling to be considered between the coils. Measurement results based on the last

described structure, show that when using the proposed facility

Do not change output power and voltage transfer function with the three different coupling factors. It is readily possible to implement such a device with higher output powers of several kW.

Claims

1. Device for contactless inductive

Energy transmission, in particular for inductive charging processes in motor vehicles,

the one primary coil arrangement and a power connected to the primary coil arrangement

has electronics which is designed for the energy transmission via the primary coil arrangement,

the primary coil arrangement having a plurality of individual coils (A, B, C) and capacitances which are connected via one or more switching devices (Si,

S _{2) of} the primary coil arrangement can be connected to different primary circuits which are tuned to the same resonance frequency and each have one of the individual coils (A, B, C) or a series connection of several of the individual coils (A, B,

C) include.

2. Device according to claim 1,

characterized,

that the primary coil arrangement has at least a first, a second and a third individual coil (A, B, C) with different inductances

have, a first of the different

Primary circuits only the first individual coil, a second of the different primary circuits a series connection of first and second individual coils and a third of the different primary circuits a series connection of first, second and third single coil (A, B, C) comprises.

3. Device according to claim 1 or 2,

characterized,

that the primary coil arrangement is designed such that the individual coils (A, B, C) have a high coupling of k> 0.9 to one another.

4. Device according to one of claims 1 to 3,

characterized,

that the individual coils (A, B, C) in the

Primary coil arrangement are arranged one above the other.

5. Device according to one of claims 1 to 4,

characterized,

that the individual coils (A, B, C) in the

Primary coil arrangement are flat coils.

6. Device according to one of claims 1 to 5,

characterized,

that the different primary circuits are serially compensated.

7. Device according to claim 6,

characterized,

that in series with each of the individual coils (A, B, C) at least one of the capacitors

is connected, so that in the primary circuits with a series connection of several of the individual coils

(A, B, C) at least one each between the individual coils (A, B, C) connected in series the capacitors is arranged.

8. Device according to one of claims 1 to 5,

characterized,

that the different primary circuits are compensated in parallel.

9. Device according to one of claims 1 to 8,

characterized,

that line ends of the individual coils (A, B, C) not connected via the one or more switching devices (Si, S ₂ ) of the primary coil arrangement to a primary circuit are open.

10. Method for contactless inductive energy

Transmission with a device according to one of the preceding claims in the case of different predetermined coupling factors between

Primary coil (s) and secondary coil,

for each of the different

Coupling factors uses a different secondary coil and another of the switchable primary circuits of the primary coil arrangement is switched, the switchable primary circuits and the secondary coils being designed in such a way that output power,

characteristic resistance and voltage transfer function for the different

Coupling factors remain constant.