DE102014220224A1 - Method and system for the contactless charging of a battery-operated object - Google Patents

Abstract

The invention relates to a method for the non-contact charging of a battery-operated object (4) via a magnetically coupled coil pair, which comprises a primary coil arrangement (12) of a charging station (6) and a secondary coil arrangement (22) of the battery-operated object (4), wherein an inverter via a is powered by a first rectifier generated DC link voltage and the primary coil assembly (12) excites and wherein at the secondary coil assembly (22) an AC voltage between two connection points is provided. It is further provided that the connection points are connected to each other during each half cycle of the AC voltage for a predetermined time interval and the DC link voltage is controlled so that switching points of the inverter in the range of a zero crossing of a current of the primary coil assembly (12), so that the inverter is driven soft switching , Further aspects of the invention relate to a computer program, a system (100), a charging station (6) and a battery-operated object (4), which are set up to carry out the method.

Description

State of the art

The invention relates to a method for contactless charging of a battery-operated object via a magnetically coupled coil pair. Further aspects of the invention relate to a computer program, a system, a charging station and a battery-operated object, which are set up to carry out the method.

When a battery-powered object is charged without contact, electrical power is transmitted via an air gap. For this purpose, a coil pair is used, which is inductively coupled to each other via a magnetic alternating field. One of the coils is integrated into the battery-operated object, the other coil is assigned to a charging station. The battery-operated object is, for example, an electric vehicle or a plug-in hybrid vehicle whose drive is entirely or at least partially by means of an electric motor. Other applications may include, for example, the non-contact charging of electrical tools or consumer devices.

Various methods and devices for contactless charging of vehicles are known from the prior art, in which energy is taken from the alternating magnetic field of a primary coil and is converted into electrical energy in a secondary coil associated with the vehicle. The electrical energy is then supplied to an energy storage of the vehicle. However, it is necessary that the vehicle is arranged as precisely as possible above the charging station. Depending on the distance and orientation of the primary coil in the charging station and the secondary coil in the vehicle, different influences on the non-contact charging system arise. The coupling factor of the coil system can vary greatly.

In this case, there is a risk that the non-contact charging system is not operated at an optimum operating point, which generally leads to a poorer efficiency and / or a higher alternating magnetic field in the air gap between the primary coil and secondary coil.

Out DE 10 2010 055 696 A1 a system for the contactless transmission of energy is known, wherein the frequency of the transmission system is adapted to the primary side in dependence on state variables of the secondary side. In addition to a mere adaptation of the system parameters on the primary side, there is also the possibility of adjusting the operating point of the inductive charging system by means of a secondary-side or two-sided power control. Such a system is described for example in the document US 2011/0231029 A1 described, with an additional voltage transformer on the secondary side is needed.

A disadvantage of the prior art is that either a one-sided power control takes place, which leads to an increased power loss in unfavorable operating points, or additional voltage transformers are required in the system, whereby the overall efficiency is reduced and the cost is increased.

Disclosure of the invention

A method for non-contact charging of a battery operated object via a magnetically coupled coil pair is proposed. The coil pair comprises a primary coil arrangement of a charging station and a secondary coil arrangement of the battery-powered object, wherein an inverter is fed via an intermediate circuit voltage generated by a first rectifier and excites the primary coil arrangement. Furthermore, an alternating voltage is provided between two connection points on the secondary coil arrangement, it being provided that the connection points are connected to each other during each half cycle of the alternating voltage for a predetermined time interval and the DC link voltage at the input is controlled so that the switching points of the inverter in the range of a zero crossing a current of the primary coil arrangement, so that the inverter is driven soft switching.

In the method, the battery-operated object with its secondary coil arrangement is located in the region of an alternating magnetic field generated by the primary coil arrangement of the charging station. The efficiency of energy transfer depends on various parameters. In particular, these parameters include the size of the air gap between the primary coil assembly and the secondary coil assembly as well as current and voltage on the secondary side. Since the secondary side is usually connected to an electrical energy storage such as a battery, the operating point of one Voltage of this energy storage and thus the state of charge of the electrical energy storage dependent. In the case of a battery as an electrical energy storage increases with increasing charge a voltage U _bat the battery, while the charging current of the battery decreases. If the battery is connected via a second rectifier, for example via a bridge rectifier, to the secondary coil arrangement, this also determines the output voltage of the vehicle-side coil arrangement.

In order to set the electrical operating point and thus the non-contact charging independent of the electrical energy storage, in particular independent of state of charge and charging power of the battery, it is provided that for a predetermined time interval during each half cycle of the AC voltage, the connection points of the secondary coil assembly are interconnected. While the connection points are connected to each other, a current can flow through the secondary coil arrangement, without the electrical energy storage being involved. The diodes of the bridge rectifier prevent this, that the electrical energy storage is shorted.

By connecting the connection points of the secondary coil arrangement during each half-wave of the alternating voltage for a predetermined time interval, the current through the secondary coil and thus the operating point can be adjusted in particular independently of the state of charge of the energy store. This degree of freedom can thus be used to increase the efficiency of the inductive energy transfer.

Furthermore, it is provided in the proposed method that the inverter which is used to excite the primary coil arrangement is supplied by the intermediate circuit. The DC link in turn is supplied via the first rectifier with electrical energy, which is connected to the mains. The power grid is, for example, a single-phase or three-phase alternating current network, the first rectifier decoupling the inverter from the alternating current network in such a way that it acts as a power factor correction device (PFC).

The inverter comprises electronic switches, which are preferably designed as semiconductor switching elements. Via the electronic switches, the inverter generates the AC voltage with which the primary coil arrangement is excited from the intermediate circuit voltage. The AC voltage is adjusted so that the desired power is transmitted. In the event that the electrical switches are operated at a point in which either the switch itself or its opposite freewheeling diode is currently flowing through a current, switching losses occur in the switches. In order to switch the electrically actuated switch preferably at the points at which the current flow has a zero crossing, it is provided to influence the control circuit and the DC link voltage. Thus, a total of three parameters are available for control, namely the intermediate circuit voltage, a primary pulse width and a secondary pulse width. The pulse widths can be adjusted by controlling the electrically actuated switch. If the inverter is operated so that the switching of the electrically actuated switch takes place exclusively at a zero crossing of the current, the inverter is operated "soft switching". On the other hand, if the switching is operated in such a way that the current does not have a zero crossing during switching, then the inverter is operated "hard-switching".

In one embodiment of the method, it is provided that the time interval in which the two connection points of the secondary coil arrangement are connected to one another is determined based at least on a measured electrical variable in the primary coil arrangement and / or the secondary coil arrangement. These measured electrical variables may in particular comprise a voltage and a current of an electrical energy store, in particular a battery voltage and a charging current of a battery.

Additionally or alternatively, in one embodiment of the method, the time interval in which the connection points are connected to each other, determined based on a state of charge of a battery.

Additionally or alternatively, it is preferable if the time interval in which the connection points are connected to one another is determined as a function of a measured coupling factor of the magnetically coupled coil pair. This coupling factor describes the quality of the magnetic coupling of the coil pair and is dependent inter alia on the orientation of the coil to each other and the size of an air gap between the two coils. The coupling factor can be measured, for example, by means of a current and / or voltage measurement when subjected to a reference signal.

In the method, it is preferably provided that, in the event that the intermediate circuit voltage assumes the smallest value that the first rectifier can set, the time interval in which the connection points are connected to one another is selected so that the inverter is activated in a soft-switching manner. Alternatively, it is conceivable that in the event that the intermediate circuit voltage assumes the smallest value that the first rectifier can set, the inverter hard switching to control and the time interval in which the connection points are interconnected, depending on the coupling factor, the state of charge of the battery or other electrical parameters.

According to the invention, a computer program is also proposed according to which one of the methods described here is carried out, wherein the computer program is executed on a programmable computer device. The computer program may be, for example, a software module, a software routine or a software subroutine for implementing a charging system with a battery-operated object and a charging station. The computer program can be stored on the battery-operated object as well as on the charging station or distributed on it, in particular on permanent or rewritable machine-readable storage media or in association with a computer device, for example on a portable storage such as a CD-ROM, DVD, Blu-ray Disc, a USB stick or a memory card. Additionally or alternatively, the computer program may be provided for download on a computing device such as a server or a cloud server, for example via a data network such as the Internet or via a communication link such as a telephone line or a wireless connection. In the case of an electric vehicle, the computer program may be stored on a control device in the vehicle.

According to another aspect of the invention, there is provided a system including a charging station, a battery operated object, and a controller, wherein the controller is configured to perform one of the methods described herein. Accordingly, features described in the context of the method correspondingly apply to the system and, conversely, the features described within the framework of the system correspondingly apply to the method.

The control unit can be assigned to the charging station or the battery-powered object. Alternatively, it can be provided that both the battery-operated object and the charging station are equipped with control units which jointly carry out the method according to the invention.

In accordance with further aspects of the invention, a charging station and a battery operated object for use with such systems are provided.

The terms "battery" and "battery-powered" are used in the present description as common in common usage also for accumulator or Akkumumulatorbetrieben. In the battery, a plurality of battery cells can preferably be spatially combined and interconnected in terms of circuitry, for example connected in series or in parallel to modules in order to be able to provide the required performance data. In principle, however, any other electrical energy storage is conceivable, for example supercapacitors.

In one embodiment of the charging station, it is provided that the first rectifier is set up to perform a power factor correction.

Advantages of the invention

With the method according to the invention or correspondingly with the system provided by the invention, additional control-engineering degrees of freedom are created which can be used to optimize the respective operating point, and thus can increase the efficiency of the inductive energy transfer. In this case, provision is made in particular for connection points on the secondary coil arrangement to be connected to one another in order to be able to set the fundamental output voltage of the secondary coil arrangement independently of a connected electrical energy store such as a battery.

Furthermore, a rectifier, which is in any case generally necessary for realizing a power factor correction, is used in order to reduce switching losses in the inverter. For this purpose, the intermediate circuit voltage provided by the rectifier is controlled such that the switches arranged in the inverter can be operated in a soft-switching manner and thus with low losses.

It is particularly advantageous if the regulation of the intermediate circuit voltage is combined with the temporary connection of the connection points on the secondary side. Typically, the rectifiers can adjust the DC link voltage provided by them only over a limited voltage range, so that a soft-switching operation of the inverter would not be possible for each provided current. By connecting the connection points on the secondary side, the current flowing in the secondary coil arrangement and thus also the current flowing in the primary coil arrangement can likewise be influenced, so that a soft switching operation of the switches in the inverter can be ensured. As a result, the occurrence of electrical power losses is minimized and the overall efficiency of the contactless charging of a battery-operated object is significantly improved.

Even if a hard-switching operation of the inverter is necessary in some operating points, the switching losses in the inverter can at least be reduced in these operating points by reducing the intermediate circuit voltage through the upstream rectifier stage.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description.

Show it:

1 a schematic representation of a charging device and a battery-powered object,

2 a schematic structure of a system for contactless charging a battery-powered object,

3 a schematic representation of a circuit diagram of a system for non-contact charging,

4 a schematic representation of the current and voltage waveforms in the primary and secondary coil assembly at full load according to an embodiment,

5 a schematic representation of the current and voltage waveforms in the primary and secondary coil assembly at partial load according to an embodiment,

6 a schematic representation of the current and voltage waveforms in the primary and secondary coil assembly at partial load according to another embodiment and

7 a schematic representation of the current and voltage waveforms in the primary and secondary coil assembly according to another embodiment.

In the following description of the embodiments of the invention, the same or similar components are denoted by the same or similar reference numerals, and in individual cases dispensed with a repeated description of this component. The figures illustrate the subject matter of the invention only schematically.

1 shows a schematic representation of a system 100 for the contactless charging of a battery operated object 4 , The battery powered object 4 is designed here as an electric vehicle and includes a secondary coil assembly 22 , The battery powered object 4 was positioned so that its secondary coil arrangement 22 directly above the primary coil assembly 12 a charging station 6 lies. The charging station 6 is with an AC mains 8th connected, about which the charging station 6 refers to electrical energy. For contactless charging of the battery operated object 4 generates the charging station 6 via its primary coil arrangement 12 an alternating magnetic field which bridges the air gap with the height h and in the secondary coil arrangement 22 is converted back into an electric current. This electrical current can then be used to charge the battery 34 of the battery operated object 4 charge.

In 2 is the system 100 for the contactless charging of a battery operated object 4 shown schematically. The electrical energy becomes an AC network 8th taken, for example, as a single-phase or three-phase AC mains 8th is executed. About a first rectifier 10 an intermediate _{circuit voltage} U _{dc is} provided, via which an inverter 11 supplied with electrical energy becomes. The first rectifier 10 decouples the inverter 11 such from the AC mains 8th that through the first rectifier 10 a power factor correction (PFC) is provided.

The inverter 11 generates an AC voltage across which a primary coil assembly of a coil pair 20 is stimulated. The coil pair 20 also has a secondary coil arrangement, taken over the electrical energy from the magnetic alternating field generated by the primary coil assembly and a second rectifier 21 is made available. To the second rectifier 21 is an electrical energy storage in the form of a battery 34 connected. The battery 34 in this case has a battery voltage U _bat and is with the second rectifier 21 charged electrical energy charged.

Via a control unit 30 can be used to optimize the efficiency of electrical energy transfer of the first rectifier 10 , the inverter 11 and the second rectifier 21 to be influenced. The control units are used as input variables 30 in particular the intermediate _circuit voltage U _dc , a battery current I _bat , a battery voltage U _bat and a height h of an air gap between the primary coil arrangement and the secondary coil arrangement.

3 shows a schematic representation of a circuit arrangement for the system 100 for the contactless charging of a battery operated object 4 , The circuit arrangement comprises a primary side 1 and a secondary side 2 , The primary side 1 is from the first rectifier 10 supplied with the intermediate _{circuit voltage} U _dc energy. The inverter 11 For example, it may be implemented as a full bridge with four switching elements S1 to S4. Each of these switching elements S1 to S4 represents an electrically operable switch, which can be designed in particular as a MOSFET or as an IGBT. Each of the switching elements S1 to S4, a freewheeling diode D1 to D4 can be connected in parallel. The targeted actuation of the switching elements S1 to S4, a rectangular alternating voltage U _{1 is} generated, which is a primary coil assembly 12 of the coil pair 20 is supplied. The primary coil assembly 12 comprises a resonant circuit, which is formed for example by a primary coil L ₁ and a series resonant capacitor C ₁ . Preferably, the frequency of the through the inverter 11 provided alternating current or the provided AC voltage U ₁ to a resonant frequency ω _{0 of} the primary coil assembly 12 Voted.

The secondary side 2 includes a secondary coil assembly 22 , which are also part of the coil pair 20 is. The secondary coil arrangement 22 comprises a secondary coil L ₂ and a series-connected resonance capacitor C ₂ . The secondary coil arrangement 22 is with the input of a second rectifier 21 connected. The second rectifier 21 includes the diodes D5 to D8, wherein parallel to the two lower diodes D7 and D8 of the second rectifier 21 in each case a switching element S5 or S6 is arranged. These switching elements S5 and S6 are preferably also semiconductor switching elements, which may be designed, for example, as a MOSFET or IGBT. The diodes D7 and D8 need not be discrete, but may also be intrinsic diodes of the respective semiconductor switching elements S5 or S6. The output voltage of the second rectifier 21 will be in the in 3 embodiment smoothed over a smoothing capacitor C ₃ smoothed. The output of the second rectifier 21 comes with the battery to be charged 34 (not shown), so that at the output voltage U _bat the battery 34 is applied.

How out 3 can be seen, by closing the two switching elements S5 and S6, the two outputs of the secondary coil assembly 22 electrically connected to each other. The two outputs are in 3 as connection points 32 characterized. For connecting the connection points 32 The switching elements S5 and S6 via a control device 23 selectively controlled, so that they are closed or opened for a predetermined time interval during each half cycle of the AC voltage. The control device 23 is from the controller 30 controlled so that the predetermined time interval b, are opened in the two switches, depending on various state parameters such as the intermediate _circuit voltage U _dc , the battery current I _bat , the battery voltage U _bat and the height h of the air gap between the primary coil assembly 12 and the secondary coil assembly 22 can be regulated.

For inductive energy transfer from the primary side 1 , in particular a charging station 6 can be assigned to the secondary side 2 especially the battery operated object 4 can be assigned, by applying the AC voltage U ₁ to the primary coil assembly 12 from the primary coil L ₁ generates an alternating magnetic field. In this case, in the primary coil L _1, a corresponding alternating current I _{1 flows} . The alternating magnetic field couples into the coil L _{2 of} the secondary coil arrangement 22 and induces there an electrical alternating voltage, so that there flows a corresponding current I ₂ . The alternating current at the output of the secondary coil arrangement 22 is through the second rectifier 21 rectified, smoothed by the smoothing capacitor C ₃ and is then ready as an output voltage. With the output voltage or the output current can then be the battery 34 getting charged.

4 shows the course of the current I ₁ and the voltage U ₁ in the primary coil assembly 12 (upper diagram) and the current I ₂ and the voltage U ₂ in the secondary coil arrangement 22 (lower diagram) in full load operation. By selective control of the switching elements S1 to S4, the intermediate _circuit voltage U _dc with changing sign in each case for a period of time a on the primary coil assembly 12 given. The time duration a is referred to as the pulse width of the voltage U ₁ or as the primary pulse width. The amplitude of the fundamental wave of the voltage U ₁ can then be adjusted via the pulse width a. The voltage U _{1 in} this case has a periodic waveform which is rectangular. Based on the period of the waveform, the pulse width a can also be expressed as a phase angle, wherein a phase angle of 180 ° would correspond to a pure square-wave voltage.

In the following, for the sake of simplicity, only the sinusoidal fundamental wave of the rectangular voltage will be considered. This simplification is justified because higher frequencies are strongly attenuated. The amplitude of the fundamental wave of the voltage U _{1 is} calculated at the resonance frequency ω = ω ₀ : U ₁ = 4 / πU _dc sin a / 2

In a first operating mode, the two switching elements S5 and S6 remain on the secondary side 2 permanently open. The secondary-side power electronics behave like a purely passive rectifier. In this operating mode, the amplitudes of the fundamental waves of the currents and of the voltages at resonant frequency ω ₀ in are calculated 4 in amount to:

The primary current I _{1 is} only from the output of the secondary side 2 applied voltage U _bat and a mutual inductance M of the coil pair 20 dependent. This primary current I ₁ can be controlled by regulating the pulse width a of the inverter 11 not affected.

5 shows a schematic representation of the time course of the primary voltage U ₁ and the primary current I ₁ in the upper diagram and in the lower diagram is a schematic representation of the secondary voltage U ₂ and the secondary current I ₂ in partial load operation. Here are in the in 5 illustrated embodiment, the switching elements S5 and S6 permanently open. This operating mode corresponds to the current or voltage curves, as in a conventional inductive power transmission with purely primary-side control and passive second rectifier 21 on the secondary side 2 occur. Again, the current I ₁ on the primary side by controlling the pulse width a in the inverter 11 not affected. As a result, the high primary current I ₁ causes about 20 A high losses from here.

In 6 is in turn plotted in the upper diagram, the course of the primary voltage U ₁ and the primary current I ₁ and in the lower diagram, the course of the secondary voltage U ₂ and the secondary current I ₂ . Similar to the in 5 the situation presented is the system 100 operated in a partial load operation, wherein the in 6 illustrated operating mode, the switching elements S5 and S6 on the secondary side 2 now be closed periodically targeted. If the switching elements S5 and S6 are closed, then the secondary coil arrangement is located 22 in a coasting state in which the secondary current I ₂ continues to flow through the secondary-side coil L ₂ and its series resonant capacitor C ₂ , but does not flow into the smoothing capacitor C ₃ . After the switching elements S5 and S6 are opened again, the secondary current I _{2 flows} via the smoothing capacitor C ₃ into one at the output of the secondary side 2 connected load, such as the battery 34 ,

In the 6 is the period of time for which the switching elements S5 and S6 are opened, shown as the pulse width b. The pulse width b is also called the secondary pulse width. If you want to specify instead the time duration for which the switching elements S5 and S6 are closed, so the connection points 32 the secondary coil assembly 22 connected to each other, this period can be obtained by subtracting the pulse width b from the period of the oscillation of the alternating current or the voltage.

In the following, only the amplitude of the fundamental wave of the secondary-side voltage U _{2 is} considered for the sake of simplification. The amplitude of the fundamental wave of the secondary voltage U ₂ is thus calculated as: U ₂ = 4 / πU _bat sin b / 2

The amplitude of the fundamental wave of the primary-side voltage U ₁ is also given by: U ₁ = 4 / πU _dc sin a / 2

Thus, the peak values of the secondary current I ₂ and the primary current I ₁ amount to:

Due to the newly introduced freewheeling state on the secondary side 2 Therefore, both the primary current I ₁ and the secondary current I ₂ can now be set specifically. This makes it possible to operate the inductive energy transfer in each case an optimal operating point and thus the inductive energy transfer even with different air gap h or a lateral offset of the primary coil assembly 12 to the secondary coil assembly 22 as well as optimally adapted in partial load operation.

In order to determine the pulse width b, ie the time duration during which the switching elements S5 and S6 are open, different operating strategies are possible. For a first operating strategy, for example, on the primary side 1 and the secondary side 2 same pulse widths a and b are used. The pulse widths a and b are calculated for a given power P _soll to:

According to a further operating strategy, the ratio of the primary current I ₁ to the secondary current I ₂ is adjusted to a constant value. In this case, the pulse widths a and b, for example, chosen so that for charging a battery 34 with a rated voltage U _rated and the current battery voltage U _{bat the} following condition applies:

In addition to the advantages already described above, the actual battery voltage U _{bat is passed} through the secondary side 2 from the system 100 decoupled, leaving on the primary side 1 and on the secondary side 2 the same currents flow as in a nominal point for which the system 100 was optimized. There is thus an impedance matching of the load by the active control of the second rectifier 21 on the secondary side 2 without the need for an additional DC-DC converter would be required.

In a further operating strategy, it is possible to adjust the operating point adaptively. In this case, an optimum operating point is adaptively adjusted such that a required power P _desired can be transmitted for a given coupling factor and a given battery voltage U _bat and at the same time an optimization variable is maximized or minimized. Such adaptive adjustment of the operating point can be achieved due to the additional degree of freedom that allows the two-sided control according to the invention. For example, the (measured) system efficiency can serve as an optimization variable, but other optimization variables are also conceivable.

Furthermore, it is also possible to adjust the operating point so that in the air gap between the primary coil L ₁ and secondary coil L _2, the magnetic field is minimized. The alternating magnetic field in the air gap of the coil pair 20 (L ₁ , L ₂ ) leads to a heating of metallic objects by induced eddy currents, which may be located in the region between the primary coil L ₁ and secondary coil L ₂ . At high magnetic fields, this represents a high security risk. The inventive minimization of the magnetic field in the air gap between the primary coil L ₁ and the secondary coil L ₂ , this security risk be reduced. Alternatively, even if a maximum magnetic field strength is maintained, the coil pair 20 (L ₁ , L ₂ ) are dimensioned smaller. Thus, the required space and the cost of building such a system are reduced 100 for inductive energy transfer.

In another operating strategy, it is possible to work the system 100 for inductive energy transmission through the active control on the secondary side 2 to expand. The two additional switching elements S5 and S6 remain on the secondary side 2 switched off during normal operation. The secondary-side power electronics with the second rectifier 21 initially behaves like a passive rectifier. If the primary current I ₁ exceeds a defined threshold value, the activation of the additional switching elements S5 and S6 is activated. As a result, an impedance matching is possible even in unfavorable conditions, such as a bad coupling factor. Thus, the system can 100 be continued to operate inductive energy transfer even if otherwise the maximum primary current I ₁ would be exceeded, whereas in conventional systems a shutdown would have to occur.

7 shows a schematic representation of the time course of the primary voltage U ₁ and the primary current I ₁ in the upper diagram and in the lower diagram is a schematic representation of the secondary voltage U ₂ and the secondary current I ₂ . At the in 7 shown operating mode is the _{DC link} voltage U _dc , which the inverter 11 used as input voltage, also regulated. Opposite to 4 . 5 and 6 the intermediate _{circuit voltage} U _{dc has been} lowered, whereby the times at which the switching elements S1 to S4 of the inverter 11 switch, have moved. The primary voltage U ₁ is now almost rectangular, which corresponds to the pulse width a a phase angle of about 180 °. Furthermore, the changes in the sign of the primary voltage U _{1 occur} exactly at the times at which the sinusoidal profile of the primary current I _{1 has} a zero crossing. If the switching elements S1 to S4 are actuated at these points in time, only slight power losses occur, which also acts as a soft-switching operation of the switching elements S1 to S4 or of the inverter 11 referred to as.

In preferred embodiments of the invention, both a control of the pulse widths a and b are performed as well as a regulation of the intermediate _{circuit voltage} U _dc.

In a further preferred embodiment variant, the first rectifier adopts a correction of the power factor, as a so-called PFC stage. Both embodiments are provided for operation on the single-phase AC voltage network as well as on the three-phase AC voltage network.

In a further embodiment, the first rectifier is designed as a three-phase, controlled B6 bridge, which allows a cost-effective implementation, especially for high power.

The invention is not limited to the embodiments described herein and the aspects highlighted therein. Rather, within the scope given by the claims a variety of modifications are possible, which are within the scope of expert action.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely 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.

Cited patent literature

• DE 102010055696 A1 [0005]
• US 2011/0231029 A1 [0005]

Claims (13)

Method for the contactless charging of a battery-operated object ( 4 ) via a magnetically coupled coil pair ( 20 ), which has a primary coil arrangement ( 12 ) of a charging station ( 6 ) and a secondary coil arrangement ( 22 ) of the battery powered object ( 4 ), wherein an inverter ( 11 ) via one of a first rectifier ( 10 ) is fed and the primary coil arrangement ( 12 ) and wherein at the secondary coil arrangement ( 22 ) an AC voltage between two connection points ( 32 ), characterized in that the connection points ( 32 ) are connected to each other during each half cycle of the AC voltage for a predetermined time interval and the DC link voltage is controlled so that switching points of the inverter ( 11 ) in the region of a zero crossing of a current of the primary coil arrangement ( 12 ), so that the inverter ( 11 ) is activated soft switching. A method according to claim 1, characterized in that both of a first rectifier ( 10 ) generated DC link voltage, as well as one of an inverter ( 11 ) generated square-wave voltage with variable pulse width for controlling the non-contact charging is used. Method according to claim 1 or 2, characterized in that additionally the time interval in which the two connection points ( 32 ), is used to control the non-contact charging. Method according to one of claims 1 to 3, characterized in that the time interval in which the two connection points ( 32 ), at least based on a measured electrical variable of the primary coil arrangement ( 12 ) and / or the secondary coil arrangement ( 22 ) is determined. Method according to one of claims 1 to 4, characterized in that the time interval in which the connection points ( 32 ), at least based on a state of charge of a battery ( 34 ) is determined. Method according to one of claims 1 to 5, characterized in that the time interval in which the connection points ( 32 ), at least in dependence on a measured coupling factor of the magnetically coupled coil pair ( 20 ) is determined. Method according to one of claims 1 to 6, characterized in that in the case in which the intermediate circuit voltage assumes the smallest value that the first rectifier ( 10 ), the time interval in which the connection points ( 32 ) are selected so that the inverter ( 11 ) is activated soft switching. Method according to one of claims 1 to 6, characterized in that in the case in which the intermediate circuit voltage assumes the smallest value that the first rectifier ( 10 ), the inverter ( 11 ) is driven hard switching and the time interval in which the connection points ( 32 ) are interconnected according to one of claims 4 to 6 selected. A computer program for performing one of the methods of any one of claims 1 to 8, wherein the computer program is executed on a programmable computer device. System ( 100 ) with a charging station ( 6 ), a battery powered object ( 4 ) and a control unit ( 30 ), the charging station ( 6 ) a first rectifier ( 10 ), an inverter ( 11 ), and a primary coil assembly ( 12 ) and the battery operated object ( 4 ) a secondary coil arrangement ( 22 ) and a second rectifier ( 21 ), wherein the inverter ( 11 ) via one of the first rectifier ( 10 ) and is arranged, the primary coil arrangement ( 12 ) and wherein at the secondary coil arrangement ( 22 ) an AC voltage between two connection points ( 32 ), characterized in that the control unit ( 30 ) is arranged to carry out one of the methods according to one of claims 1 to 8. Charging station ( 6 ) for use in a system ( 100 ) according to claim 10. Charging station ( 6 ) according to claim 11, characterized in that the first rectifier ( 10 ) is arranged to perform a power factor correction. Battery operated object ( 4 ) for use in a system ( 100 ) according to claim 10.

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