DE102018216916A1 - Device for contactless inductive energy transmission, in particular for inductive charging processes in motor vehicles - Google Patents

Abstract

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 power electronics connected to the primary coil arrangement and which is designed for energy transmission via the primary coil arrangement. The primary coil arrangement has a plurality of individual coils and capacitances which can be connected to different primary circuits via one or more switching devices of the primary coil arrangement. The primary circuits are tuned to the same resonance frequency and each include one of the individual coils or a series connection of several of the individual coils. The proposed device enables different types of vehicles with different ground clearances to be supplied inductively with energy, the charging power and current and voltage levels remaining the same at the operating point.

Description

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 power electronics connected to the primary coil arrangement and which is designed for energy transmission via the primary coil arrangement. The invention also relates to a method for contactless inductive energy transmission with the proposed device.

Inductive energy transmission is a contactless transmission technology that can be used, for example, to charge the battery of an electric vehicle. The primary coil is in the floor of a parking space and the secondary coil is 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 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. Since the coupling factor decreases or increases with a change in the distance between the primary coil and the secondary coil, this leads to deviations in the operating point. Deviations mean that the charging power fluctuates and the voltage level or current change. If the deviations from the intended operating point become too large, the operational safety can be impaired, so that the charging device must be switched off.

To avoid this problem in the field of motor vehicles, it is known to suitably regulate the primary and secondary circuits. If the coupling factor is changed, for example, the input voltage or the output voltage can be adjusted. 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. This means that the same charging power is possible with the same amperage and voltage levels. 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 enables a constant charging power and constant voltage level without mechanically moving parts, even with predetermined different distances between the primary and secondary coils.

Presentation of the invention

The object is achieved with the device for contactless inductive energy transmission according to claim 1. Advantageous embodiments of the device are the subject of the dependent claims or can be found in the following description and the exemplary embodiment. Claim 8 specifies a method for contactless inductive energy transmission with the proposed device.

The proposed device has a primary coil arrangement and power electronics connected to the primary coil arrangement, which is designed for the energy transmission via the primary coil arrangement, which therefore 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 device is characterized in that the primary coil arrangement has one or more switching devices and several individual coils and capacitances which can be connected to different primary circuits via the one or more switching devices. 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.

In the primary coil arrangement of the proposed device, different combinations of individual coils can thus be connected to primary circuits, so that the different primary circuits have different inductances. Appropriate dimensioning of the individual coils and capacitors makes it possible to supply various types of vehicles with different ground clearances (z-classes) contactlessly and inductively with only one power electronics and the primary coil arrangement by switching to the appropriate combination of individual coils. Charging power as well as current and voltage levels remain the same at the operating point. This only presupposes that the inductances of the secondary coils in the respective vehicle classes and the inductances of the different primary circuits are matched to the different distances or coupling factors, 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 circuits comprises only the first individual coil, the second primary circuit comprises a series connection of first and second individual coils, and the third primary circuit comprises a series connection of first, second and third individual coils. 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 the corresponding primary-side coil combination or the corresponding primary circuit is then switched depending on the vehicle or vehicle class.

$$R_{\mathrm{2,}c}\approx k{\omega }_d{L}_2$$

$$M_U=\frac{U_2}{U_1}=\sqrt{\frac{L_2}{L_1}}$$

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 R _{2, c} and voltage transfer function M _U With serial compensation of the primary and secondary circuit, the following result: $$P=\frac{U_{\mathrm{2nd}}{}^{\mathrm{2nd}}}{R_{\mathrm{2nd}}}=\frac{{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="DE102018216916A1\_0004.png"\; state="\{\{state\}\}">U</figure-callout>}}_1{}^{\mathrm{2nd}}}{k{\mathrm{<figure-callout\; id="1"\; label="\omega \; d\; L"\; filenames="DE102018216916A1\_0004.png"\; state="\{\{state\}\}">\omega \; </figure-callout>}}_d{L}_{}{}_1}$$

$${\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="DE102018216916A1\_0006.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{2,}c}\approx k{\omega }_d{L}_{\mathrm{2nd}}$$

$$M_U=\frac{U_{\mathrm{<figure-callout\; id="1"\; label="2nd\; U"\; filenames="DE102018216916A1\_0004.png"\; state="\{\{state\}\}">2nd\; </figure-callout>}}}{U_{}}=\sqrt{\frac{L_{\mathrm{<figure-callout\; id="1"\; label="2nd\; L"\; filenames="DE102018216916A1\_0004.png"\; state="\{\{state\}\}">2nd\; </figure-callout>}}}{L_{}}}$$

It can be seen from the equations that L ₁ and k as well L ₂ and k are in the same ratio. k corresponds to the coupling factor, L ₁ and L ₂ the inductance of the coils or coil combination in the primary circuit and in the secondary circuit. In the proposed method, primary circles and secondary circles are dimensioned such that the three terms remain constant for all predetermined coupling factors or distances between the primary and secondary coils. Thus, when the coupling factor k is increased in the case of serial compensation of the primary circuit and the secondary circuit, the inductance L ₁ and the inductance L ₂ should be chosen correspondingly lower than with a smaller coupling factor (k _↑ => L _{1 ↓} L _{2 ↓} - k _↓ => L _{1 ↑} L _{2 ↑} ). 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 equation for P that required for the respective coupling factor L ₁ and from the equation for R _{2, c} or M _U the required L ₂ be determined. The inductances of the individual coils of the primary coil arrangement are then chosen so that the different ones L1 (for the different coupling factors) can be obtained by a suitable combination of the individual coils (including the use of only one of the individual coils) with the aid of the switching device (s).

In this way it is achieved that, for example, for three different distances or vehicle classes and therefore 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 strength and voltage levels for all three vehicle classes with the proposed device, which does not require any mechanically moving parts or corresponding regulations of the primary and secondary electronics.

The different primary circuits 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 parallel compensation on both sides, the equations for then give rise to P , R _{2, c} and M _U that if the coupling factor is increased, the inductivities of the primary circuit and the secondary circuit must also be increased and if the coupling factor is reduced (k _↑ => L _{1 ↑} L _{2 ↑} - k _↓ => L _{1 ↓} L _{2 ↓} ).

Serial compensation of the primary circuits also has the advantage that each of the A suitable capacitance can be connected in series to individual coils, so that when a number of the individual coils are connected in series, at least one capacitance lies between the individual coils. Such a division of the capacities over the primary coil arrangement is advantageous in order to distribute high reactive voltages over the entire coil arrangement, especially with small coupling factors, that is to say a large distance and large inductance. The connection ends of the coil arrangement connected in series therefore do not have the total reactive voltage, which can be several kV.

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 flows squarely into the coil inductance with a high internal coupling. This enables higher inductances to be achieved with coils with a smaller number of turns and thus with a lower material consumption.

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 for the energy transfer to other objects in which there are similar problems of different distances or coupling factors.

Figure list

• 1 ein Beispiel für die Verhältnisse bei der Energieübertragung für drei unterschiedliche Koppelfaktoren gemäß dem Stand der Technik;
• 2 ein Schaltbild einer Einrichtung zur kontaktlosen induktiven Energieübertragung gemäß der vorliegenden Erfindung;
• 3 eine schematische Darstellung der Primärspulenanordnung und der Sekundärspule bei einer Einrichtung gemäß der vorliegenden Erfindung;
• 4 eine Draufsicht auf die Primärspulenanordnung der 3 sowie eine Darstellung der Einzelspulen dieser Primärspulenanordnung; und
• 5 ein Schaltbild einer weiteren Einrichtung zur kontaktlosen induktiven Energieübertragung gemäß der vorliegenden Erfindung.

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

• 1 an example of the relationships in energy transmission for three different coupling factors according to the prior art;
• 2nd a circuit diagram of a device for contactless inductive energy transmission according to the present invention;
• 3rd is a schematic representation of the primary coil arrangement and the secondary coil in a device according to the present invention;
• 4th a plan view of the primary coil arrangement of the 3rd and a representation of the individual coils of this primary coil arrangement; and
• 5 a circuit diagram of another device for contactless inductive energy transmission according to the present invention.

Ways of Carrying Out the Invention

In previous systems, which 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. 1 shows an example of three different coupling factors based on a diagram that the voltage transfer function U ₂ / U ₁ depending on the resistance of the secondary side R ₂ shows. U ₁ and U ₂ set the input voltage U ₁ and the output voltage U ₂ , L ₁ and L ₂ in turn represent the inductance in the primary circuit and the inductance in the secondary circuit. k ₁ , k ₂ and k ₃ are the three different given coupling factors, ω _d 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. 2nd shows an example of an embodiment of the proposed facility. The figure shows the input voltage U _{1, DC} using an inverter into a suitable AC voltage U ₁ is changed. With this AC voltage, the primary coil arrangement 1 the proposed device, which in the present example consists of three coils with the inductors L _1a , L _1b and L _1c as well as the associated capacities connected in series C _1a , C _1b and C _1c is formed. Between these individual coil and capacitor components are two switching devices S ₁ and S ₂ arranged with which different primary circuits can be switched in the primary coil arrangement. The first primary circuit only consists of the first primary coil with the inductance L _1a and capacity C _1a . The second primary circuit is connected in series by the first two coils with the inductors L _1a and L _1b as well as the associated capacities C _1a and C _1b educated. The third primary circuit is formed by connecting all three coils and capacitors in series. The individual primary circuits are each based on the corresponding capacities at the same design frequency ω _d compensated. 2nd shows the overall system, ie also the secondary side with the secondary coil L _2x , the capacitor in the secondary circuit C _2x , the inverter, the load-side capacity C _DC2 and the load-side resistance R _{2, DC} , for example by the to charging vehicle battery of a motor vehicle can be formed. In the example shown, the primary circuit and secondary circuit are each compensated in series. For charging vehicles of different distance classes, there is one or more of the individual coils for each primary circuit L _1x a secondary coil L _2x , which is suitable for the respective inductance of the primary circuit. That coil L _2x 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, a suitable primary-side coil combination is then switched as the primary circuit.

The coordination between the different vehicle classes or distance classes and the primary circuits that can be switched in the device takes place with the system of equations already mentioned above in such a way that the output power, characteristic resistance and voltage transfer function remain constant for the different vehicle classes or distance classes.

If the coupling factor is high, ie the distance between the motor vehicle and the ground is low, the primary inductance must be small. The spools L _1b and L _1c 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 using the switching devices S ₁ , S ₂ either just a series connection L _1a and L _1b or a series connection L _1a , L _1b and L _1c interconnected with their capacitors in the primary side. Because the values for the three equations above remain constant, change P , R _{2, c} and M _U Not.

The resonance frequencies of both systems, i. H. The primary side and secondary side remain constant at the 85 kHz or 140 kHz, for example, which are currently typical. 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. If the inductance is increased by a series connection, the capacitance must be reduced. With serial compensation, this also works advantageously by connecting the capacitors in series. The total resonance frequency then remains constant.

Since the number of turns flows squarely into the coil inductance when there is a high internal coupling (L = magnetic conductance x number of turns ² ), the non-connected individual coils are on the primary side ( L _1b With C _1b etc.) does not resonate and there can be no effective power transmission to the unconnected individual coils. This is a positive side effect, since the line ends of the unconnected single coil should normally be open and no power transmission should take place anyway. Without resonance, there are also no high reactive voltages in the unconnected individual coils of the primary coil arrangement.

When designing the primary coil arrangement, care is preferably taken that the primary-side individual coils have the highest possible coupling with one another. This is achieved by arranging the individual coils one above the other, as shown schematically in 3rd is shown. This figure shows the primary coil arrangement with the coils arranged one above the other A , B and C. of inductors L _1a , L _1b and L _1c and the spaced-apart coil D of the secondary side with the inductance L _2a . The individual coils on the primary side are arranged above the radius r of a radial flat winding. This works with any coil topology. With a high coupling factor within the primary side, the required coil length is shortened, which leads to a cost saving, the above relationship between the inductance L and the number of turns.

4th shows a plan view of an exemplary coil arrangement according to 3rd in which the three individual coils A , B and C. are recognizable. In the lower part of the figure are the three coils A , B , C. Again shown side by side for better visibility.

5 shows another example of an embodiment of the proposed device, in which the primary and secondary circuits are compensated in parallel. In contrast to the design of the 2nd a choke coil is required for this L _DR1 , L _DR2 between the voltage source and the inverter on the primary side and between the inverter and the load on the secondary side. The parallel compensation also makes two additional switching devices in this example S ₃ , S ₄ in the primary coil arrangement 1 needed, for example, when operating only the first coil L1a all three capacities C1a , C1b and C1c to be able to switch in parallel, while with all three coils connected in series only the first capacitance C1c is needed.

With an exemplary dimensioning of the device according to 2nd for a performance P of 50W and input and output voltages of 28V with corresponding distances z ₁ = 4 cm, z ₂ = 6 and z ₃ = 10 cm and the resulting coupling factors k ₁ = 0.36, k ₂ = 0.2 and k ₃ = 0.1 values for the coils and capacitors of L _1a = 41.4 µH, L _1b = 5.7 µH, L _1c = 13.9 µH, C _1a = 30.1 nF, C _1b = 37.6 nF and C _1c = 16.7 nF determined, values of k _xy > 0.9 being used for the coupling between the coils to be taken into account. Measurement results obtained on the basis of the structure described last show that the output power and voltage transmission function do not change with the three different coupling factors when the proposed device is used. It is readily possible to implement such a device with higher output powers of several kW.

Claims (8)

Device for contactless inductive energy transmission, in particular for inductive charging processes in motor vehicles, which has a primary coil arrangement and power electronics connected to the primary coil arrangement and which is designed for energy transmission via the primary coil arrangement, the primary coil arrangement having a plurality of individual coils (A, B, C) and capacitors which can be connected to different primary circuits via one or more switching devices (S ₁ , S ₂ ) of the primary coil arrangement, 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. Establishment after Claim 1 , characterized in that the primary coil arrangement has at least a first, a second and a third individual coil (A, B, C) with different inductivities, with a first of the different primary circuits only the first individual coil, a second of the different primary circuits having a series connection of the first and second individual coil and a third of the different primary circuits comprises a series connection of first, second and third individual coils (A, B, C). Establishment after Claim 1 or 2nd , characterized in that the individual coils (A, B, C) are arranged one above the other in the primary coil arrangement. Establishment according to one of the Claims 1 to 3rd , characterized in that the individual coils (A, B, C) are flat coils in the primary coil arrangement. Establishment according to one of the Claims 1 to 4th , characterized in that the different primary circuits are serially compensated. Establishment after Claim 5 , characterized in that at least one of the capacitors is connected in series with each of the individual coils (A, B, C), so that in the primary circuits with a series connection of several of the individual coils (A, B, C) between the individual coils connected in series (A, B, C) at least one of the capacitors is arranged. Establishment according to one of the Claims 1 to 4th , characterized in that the different primary circuits are compensated in parallel. Method for contactless inductive energy transmission with a device according to one of the preceding claims with different predetermined coupling factors between the primary coil (s) and secondary coil, in which a different secondary coil is used for each of the different coupling factors and another of the switchable primary circuits of the primary coil arrangement is switched, the switchable Primary circuits and the secondary coils are designed so that output power, characteristic resistance and voltage transfer function remain constant for the different coupling factors.

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