WO2017129654A1

WO2017129654A1 - A system and a method for detecting an authorized secondary unit in a system for inductive power transfer

Info

Publication number: WO2017129654A1
Application number: PCT/EP2017/051606
Authority: WO
Inventors: Rolf Müller; Dirk MÜHLENHOFF
Original assignee: Bombardier Primove Gmbh
Priority date: 2016-01-29
Filing date: 2017-01-26
Publication date: 2017-08-03
Also published as: GB2546788A; GB201601648D0

Abstract

The invention relates to a system and a method for detecting an authorized secondary unit (4) in a system (2) for inductive power transfer, wherein the system comprises at least one means (11) for providing a short circuit of the secondary winding structure (10), wherein the system comprises at least one primary-sided system for detecting the short circuit of a secondary winding structure (10), wherein an authorized secondary unit (4) is detectable if a short circuit of the secondary winding structure (10) is detected.

Description

A system and a method for detecting an authorized secondary unit in a system for inductive power transfer

The invention relates to a system and a method for detecting an authorized secondary unit of a system for inductive power transfer.

Electric vehicles, in particular a track-bound vehicle, and/or a road automobile, can be operated by electric energy which is transferred by means of an inductive power transfer. Such a vehicle may comprise a secondary unit which can be also referred to as receiving device. The secondary unit is adapted to receive an alternating electromagnetic field and to produce an alternating electric current by electromagnetic induction. Such a secondary unit can comprise or provide a so-called secondary winding structure. Furthermore, such a vehicle can comprise a rectifier adapted to convert an alternating current (AC) to a direct current (DC). The DC can be used to charge a traction battery or to operate an electric machine. The rectifier converts the AC provided by the receiving device into the DC.

The inductive power transfer is usually performed using a primary unit which generates the alternating electromagnetic field by a primary winding structure and said secondary unit which comprises device secondary winding structure for receiving said

electromagnetic field. The primary unit and the secondary unit can e.g. each comprise a set of three-phase windings providing the aforementioned primary and secondary winding structure. A set of windings of the primary unit can be installed on the ground (primary windings) and can be fed by a wayside power converter (WPC). A set of windings of the secondary unit is installed on the vehicle. For example, the second set of windings can be attached underneath the vehicle, in the case of trams under some of its wagons. The first and the secondary side can be part of a high frequency transformer to transfer electric energy to the vehicle. This transfer can be done in a static state (when there is no movement of the vehicle) and in a dynamic state (when the vehicle moves). US 7,454,170 B2 discloses an inductive transmission system for inductive transmission of power and full duplex data signals between first and second devices. The transmission system includes a bi-directional inductive channel between the two devices, a transmitter for transmitting a power signal at a first frequency from the first device to the second device over the inductive channel, a first modulating device for modulating a first data signal at a first modulation frequency, and a second modulating device for modulating a second data signal at a second modulation frequency. Further, the transmitters transmit the modulated first data signals from the first device to the second device over the inductive channel and transmit the modulated second data signals from the second device to the first device over the inductive channel. The first modulation frequency and the second modulation frequency are at least a factor two apart.

Inductive power transfer usually requires a correct positioning of a vehicle-sided secondary winding structure relative to a primary winding structure in order to maximize the amount of transfer power but also in order to meet safety requirements and ensure an electromagnetic compatibility.

WO 201 1/127455 A2 describes a wireless charging and wireless power alignment of wireless power antennas associated with a vehicle.

WO 2014/023595 A2 discloses a vehicle and an induction charging unit, wherein the induction charging unit comprises a primary coil and the vehicle comprises a secondary coil. Further, in the charging position, the secondary coil is located in a preferred spatial position range with respect to the primary coil with the result that, in order to set the charging position, the system determines, by means of an electromagnetic distance and angle measurement using triangulation, a location which describes a time-dependent spatial position of the secondary coil with respect to the primary coil. The system detects, by means of the location and the charging position, at least one partial driving direction along which the location of a charging position can be approached.

The documents disclose communication antennas of an inductive power transfer (IPT) unit, namely the primary unit or the secondary unit.

GB 2522852 A discloses a system and a method for detecting a correct relative position between a primary winding structure and a secondary winding structure of a system for inductive power transfer. Within the proposed method, a first and a second signal are transmitted from the vehicle to a primary side, wherein the correct position and/or orientation is detected depending on the transmitted signals.

It is desired to authorize a secondary unit before enabling the inductive power transfer in order to ensure that a vehicle equipped with a matching secondary unit is arranged above the primary winding structure. It is further desired to align the secondary winding structure relative to a primary winding structure in order to transfer power inductively with a high efficiency. A strong magnetic coupling between the primary and the secondary winding structure is only provided if the secondary winding structure is positioned relative to the primary winding structure within a predetermined interval of positions and/or orientations. It is, for instance, possible that an aligned state is only provided if the secondary winding structure is at least partially or fully arranged in an active volume assigned to the primary winding structure. The active volume can be a volume through which at least a part, e.g. 80 %, 90 % or 95 %, or all magnetic field lines of an electromagnetic field generated by the primary winding structure extend.

There is the technical problem to provide a system and a method for detecting an authorized secondary unit of a system for inductive power transfer in order to reliably ensure that a vehicle equipped with a matching secondary unit is arranged above the primary winding structure. Further, there is the technical problem of determining a correct relative position between a secondary winding structure and a primary winding structure of a system for inductive power transfer which provide a reliable, quick and easy-to implement detection of the correct position, i.e. the aligned state.

The solution to said technical problem is provided by the subject-matter with the features of claim 1 and 12. Further advantageous embodiments of the invention are provided by the subject-matter of the sub claims.

It is a main idea of the invention to detect an authorized secondary unit by actively providing a short circuit of the secondary winding structure and detecting said short circuit on the primary side. If the short circuit is detected, an authorized secondary unit is detected. An authorized secondary unit can denote a secondary unit with a secondary winding structure by which the electromagnetic power transfer field can be received. Thus, it can be ensured that a vehicle equipped with a matching secondary unit is arranged above the primary unit and inductive power transfer can be performed safely.

Further, the system can be used for detecting a correct relative position between a secondary winding structure and a primary winding structure of a system for inductive power transfer.

The system for inductive power transfer can e.g. be a system for inductive power transfer to a vehicle. The proposed system can be part of the system for inductive power transfer.

The system for inductive power transfer can comprise a primary unit with a primary winding structure. The primary unit can e.g. comprise a totality or a subset of components by which an alternating electromagnetic field for inductive power transfer is generated. The primary unit can e.g. be provided by an inductive power transfer pad. Such a pad can be installed on the surface of a route or a parking space or it can be integrated within such a surface. In particular, the primary unit can comprise an inverter for providing an alternating operating current for one or each phase line of the primary winding structure.

Further, the system for inductive power transfer can comprise a secondary unit with a secondary winding structure. The secondary unit can be attached to a vehicle. The secondary unit can e.g. comprise a totality or a subset of components by which the alternating electromagnetic field for inductive power transfer (which is generated by the primary winding structure) is received and a corresponding output voltage is provided. In particular, the secondary unit can comprise a rectifier, wherein an alternating output voltage of the secondary winding structure during reception of the alternating

electromagnetic field can be rectified. The terminals of the secondary winding structure can be connected to an alternating current (AC) terminals of a secondary-sided rectifier.

The present invention can be applied in particular to the field of inductive energy transfer to any land vehicle, for example, track-bound vehicles such as rail vehicles (e.g. trams). In particular, the invention relates to the field of inductive power transfer to a road automobile, such as individual (private) passenger cars or public transport vehicles (e.g. busses).

The system comprises at least one means for providing a short circuit of the secondary winding structure. This means that the short circuit can be established by a controlled operation of the at least one means for providing the short circuit. The at least one means can e.g. comprise a switching element, wherein terminals of the secondary winding structure are connectable by said switching element. The short circuit of the secondary winding structure can e.g. be provided if terminals of the secondary winding structure are electrically connected, e.g. by a galvanic connection. In the case of a short circuit, the terminals of the secondary winding structure have the same electric potential.

As will be explained later in more detail, the short circuit of the secondary winding structure can be an actively controlled short circuit. This can mean that a secondary-sided control unit can control an operation of at least one means for providing the short circuit.

Further, the system comprises at least one primary-sided system for detecting the short circuit of the secondary winding structure. This can mean that all steps for detecting the short circuit are performed by primary-sided elements.

In the context of this invention, the term "secondary-sided" can mean that the respective element is arranged fixed in position relative to the secondary winding structure. In particular, the term "secondary-sided" can mean that the respective element can be part of the secondary unit. Correspondingly, the term "primary-sided" can mean that the respective element is arranged fixed in position relative to the primary winding structure. In particular, the term "primary-sided" can mean that the respective element is part of the primary unit.

An authorized secondary unit is detectable if a short circuit of the secondary winding structure is detected. In particular, the authorized secondary unit is detectable by a primary-sided control unit. If an authorized secondary unit is detected, the inductive power transfer can be enabled. If an authorized secondary unit is detected, the inductive power transfer can be enabled or continued. If no authorized secondary unit is detected, the inductive power transfer can be disabled, terminated or interrupted. The authorized secondary unit can denote a secondary unit which has paired with the primary unit in order to perform inductive power transfer with pair-specific transfer characteristics or parameters. Detecting the authorized secondary unit can mean that it is verified that a paired secondary unit is placed above the primary unit.

The short circuit can in particular be detected if the short circuit is provided and an alternating electromagnetic field is generated simultaneously by the primary winding structure. The alternating electromagnetic field can be generated with a nominal power or with a reduced power (in comparison with the nominal power). The nominal power can be a power of the alternating electromagnetic field during inductive power transfer. It can be assumed that the short circuit of the secondary winding structure is only detectable if a selected vehicle is located in the vicinity of the primary unit, in particular in the active volume of the primary unit. The selected vehicle can denote a vehicle which has requested inductive power transfer at the primary unit and which has provided

corresponding charging information.

In order to transfer electric energy to the vehicle, the secondary unit has to be arranged in an active volume of the primary unit. If the vehicle approaches the primary unit, an authorization operation can be started. It is for instance possible that the secondary unit broadcasts a pairing signal periodically if approaching one or multiple primary units. Upon reception of the pairing signal, a primary unit can transmit a pairing acknowledge signal. Before enabling or starting inductive power transfer, it is important to verify that inductive power transfer will be performed between the paired units. The verification can be performed by detecting the secondary winding structure with a short circuit and can also be referred to as detecting an authorized secondary unit.

It is for instance possible that the secondary unit transmits an authorization request signal to the specific primary unit which transmitted the pairing acknowledge signal. Upon reception of the authorization request signal, the primary unit can transmit an

authorization acknowledge signal and activate the short circuit detection. Upon reception of the authorization acknowledge signal, the secondary unit can activate a short circuit of the secondary winding structure. If the short circuit is detected, the aforementioned verification has been successfully performed.

In case that the short circuit of the secondary winding structure is not detectable on the primary side, e.g. by a primary-sided control unit, it can be assumed that the secondary unit of the paired units is not within the active volume and inductive power transfer will not be performed between the paired units. In this case, an no authorized secondary unit can be detected.

The detection of the authorized secondary unit can e.g. be performed before the actual inductive power transfer is initiated. The proposed detection, however, can be performed while an alternating electromagnetic field is generated by the primary winding structure.

In other words, providing a short circuit of the secondary winding structure can be used to reliably and quickly signalize that power can be transferred inductively to a selected secondary unit. Advantageously, no complicated other signal transmissions and evaluations have to be performed in order perform the authorization.

In another embodiment, the system comprises at least one secondary-sided signal transmitter unit for transmitting an authentication request signal. The secondary-sided signal transmitter can be part of a secondary-sided transceiver unit for transmitting and receiving signals of or within a communication link between the secondary unit and the primary unit.

Further, the system comprises at least one primary-sided signal receiver unit for receiving the authentication request signal. The primary-sided signal receiver unit can be part of a primary-sided transceiver unit for transmitting and receiving signals of or within the aforementioned communication link.

The at least one primary-sided system for detecting the short circuit of the secondary winding structure is activatable if the authentication request signal is received.

If a vehicle with the secondary unit approaches the primary unit, a so-called pairing process can be performed. This can mean that a communication link is established between the secondary unit and the primary unit. Using said established communication link, the authentication request signal can be transmitted from the secondary unit to the primary unit. The authentication request signal can e.g. be transmitted if the short circuit of the secondary winding structure is provided. In particular, the authentication request signal can be transmitted after the short circuit has been provided or simultaneously to the provision of the short circuit or before the short circuit is provided.

In particular, the short circuit detection based authorization can be performed before the inductive power transfer is performed.

In another embodiment, the system comprises at least one primary-sided control unit and at least one primary-sided load sensing means for sensing a load provided by a secondary unit. The primary-sided control unit and the primary-sided load sensing means can provide the at least one primary-sided means for detecting the short circuit of the secondary winding structure. Further, the short circuit of the secondary winding structure is detectable by the primary-sided control unit depending on the sensed load, e.g. the sensed load value. The secondary unit, in particular the secondary winding structure and elements connected to the secondary winding structure, can be modelled as a load for the primary unit, wherein the primary unit can be considered a power source. The load provided by the secondary unit can depend on an operational state of the secondary unit. In particular, a short circuit of the secondary winding structure will provide an increase of the load, in particular a sudden increase Thus, sensing the load advantageously allows identifying the said short circuit in a reliable and fast way.

In particular, at least one characteristic of the sensed load, e.g. a value and/or a gradient, can be compared to (a) reference value(s) stored in a data base, e.g. in the form of a look up table. The data base can further comprise operational states assigned to each of these reference values or to each set of multiple reference values. In particular, the data base can comprise one or more reference values to which an operational state with a short circuit of the secondary winding structure is assigned. The data base can e.g. be provided by a calibration procedure. Thus, the short circuit of the secondary winding structure can be detected by comparing a sensed or determined value to reference values in the data base.

In a preferred embodiment, the load sensing means comprises at least one current sensing means for sensing at least one operating current of the primary winding structure. The operating current can be an AC current. The primary winding structure can comprise one or more, in particular three, phase line(s). In the case of more than one phase line, the load sensing means can comprise a current sensing means for sensing the operating current of each phase line. A current sensing means can e.g. be provided by a current sensor. In this case, the load or load value provided by the secondary unit is provided or proportional to an effective value or route-mean-square value of the operating current(s).

Alternatively, the current sensor is a current sensor for sensing an input current of an inverter which provides the at least one operating current. The input current can be a DC current provided to the inverter, e.g. by a rectifier or by a power grid. In this case, the load or load value provided by the secondary unit is provided by or proportional to the magnitude of the input current.

In particular, the primary unit generates the alternating electromagnetic field which induces a voltage in the secondary winding structure. The induced voltage drives a current in the secondary winding structure depending on a load connected to the secondary winding structure or secondary unit. The higher the current, the higher the load for the primary unit provided by the secondary unit. A short circuit of the secondary winding structure will provide a quick increase of the current and thus an increase of the load, in particular a sudden increase, as the internal resistance of the secondary unit tends to zero. In this case, the current flowing in the primary winding structure will also increase. This increase will also lead to an increase of the DC input current provided to an inverter which, in turn, provides the operating current. Thus, the increase of the effective value of the operating current or of the DC input current can be used for detecting a change of the load and thus the short circuit of the secondary winding structure.

It is, of course, also possible to measure an input power and/or an output power of a primary-sided inverter to which the primary winding structure is connected. In this case, the load or load value provided by the secondary unit can be proportional to the measured power. As will be explained in the following, it is also possible to determine a gradient of the operating current or the DC input current of an inverter in order to detect a short circuit of the secondary winding structure.

Providing the load sensing means by a current sensing means advantageously allows using existing components of a primary unit, while a reliable and accurate sensing of the load provided by the secondary unit is provided.

Alternatively or in addition, the load sensing means can comprise at least one voltage sensing means for sensing the input voltage of the inverter providing the operating current(s). In this case, the load or load value provided by the secondary unit can be proportional to a product of an effective value or route-mean-square value of the operating current(s) and an effective value or route-mean-square value of the input voltage.

In another embodiment, the short circuit of the secondary winding structure is detectable by comparing a set value of the load with an actual value of the load. In particular, the short circuit can be detected if the actual sensed value of the load is higher, e.g. by more than a predetermined amount, than the set value of the load. The set value can e.g. be an average value or a maximal value of a range of load values which are experienced or provided during inductive power transfer in normal operational modes of the secondary unit. Also, the set value can be determined arithmetically, e.g. using a model. In another embodiment, the short circuit of the secondary winding structure is detectable by evaluating a change of the load value over time. The change of the load value over time can e.g. be determined by determining a gradient of the load value. The short circuit can e.g. be detected if the change of the load value in a predetermined time interval is positive and higher than a predetermined threshold value. This means that the short circuit can be detected if the gradient is positive and higher than a predetermined gradient threshold value. Evaluating the change of the load value over time advantageously allows a reliable and fast detection of the short circuit of the secondary winding structure.

The proposed detection of the short circuit can be performed alternatively or in addition to the detection based on a comparison of a set value to an actual value of the load.

In another embodiment, the system comprises at least one secondary-sided control unit for controlling the at least one means for providing the short circuit of the secondary winding structure. The secondary-sided control unit can thus provide the short circuit by controlling the at least one means for providing the short circuit. Of course, the secondary- sided control unit can also remove the short circuit by an adequate control of the at least one means for providing the short circuit. The secondary-sided control unit can e.g.

control an operation of the at least one means for providing the short circuit depending on a secondary-sided failure or a termination signal. This advantageously allows providing the short circuit in a fast and reliable way in order to signalize the presence of the secondary winding structure.

In another embodiment, the at least one means for providing the short circuit of the secondary winding structure comprises at least one switching element, wherein terminals of the secondary winding structure are connectable by the at least one switching element. In particular, the terminals can be connected if the at least one switching element is in a closed state, wherein the terminals can be disconnected if the at least one switching element is in an open state. The at least one switching element can e.g. be provided by a MOSFET or an IGBT.

Thus, an electric path between the terminals of the secondary winding structure can be provided, wherein the path comprises the at least one switching element.

This advantageously provides a very easy-to-implement way for providing a means for establishing the short circuit of the secondary winding structure. In another embodiment, the at least one switching means is integrated into a secondary- sided rectifier. The rectifier can e.g. have AC input terminals which are connected to the terminals of the secondary winding structure. Further, the rectifier can have DC output terminals, which can be connected to a DC network. The secondary-sided rectifier can be passive rectifier comprising only passive electric elements, e.g. diodes. Alternatively, the rectifier can be an active rectifier wherein the active rectifier comprises at least one active electric element, e.g. at least one switching element. It is possible that the at least one switching element is added to the rectifier, in particular in the case of a passive rectifier, or provided by an active element of the rectifier, in particular in the case of an active rectifier.

This advantageously reduces an installation effort and/or building space requirements for providing the means for providing the short circuit.

In another embodiment, the secondary-sided rectifier is provided by two rectifying legs, wherein the rectifying legs are arranged electrically parallel to one another, wherein each rectifying leg comprises two diodes which are connected in series. Further, one switching element is connected electrically in parallel to at least one diode, in particular to exactly one diode, of the rectifying leg. The terminals of the secondary winding structure can e.g. be connected to a connection section between two diodes of one rectifying leg. A first terminal of a first diode of one rectifying leg can be connected to a high potential phase line, wherein a second terminal can be connected to the terminal of the secondary winding structure and a first terminal of a second diode of the rectifying leg. A second terminal of the second diode of the rectifying leg can be connected to a low potential phase line. The switching element can either be arranged electrically in parallel to the first diode or the second diode of one rectifying leg.

This advantageously allows a very simple implementation of the at least one means for providing the short circuit, wherein building space requirements are reduced.

In another embodiment a correct relative position between a secondary winding structure and a primary winding structure of a system for inductive power transfer is detected if the short circuit of the secondary winding structure is detected. A correct relative position or an aligned state is detectable if a short circuit of the secondary winding structure is detected. In particular, the correct relative position is detectable by a primary-sided control unit. This means that the detection of the short circuit can also be used for detecting a correct or incorrect alignment of the winding structures.

It can be assumed that the short circuit of the secondary winding structure is only detectable if the secondary winding structure and the primary winding structure are in an aligned state. This can mean that a relative position between the secondary winding structure and the primary winding structure is within a range of predetermined relative positions. This can also mean that the secondary winding structure is at least partially or fully arranged within an active volume assigned to the primary winding structure.

In case that the short circuit of the secondary winding structure is not detectable on the primary side, e.g. by a primary-sided control unit, it can be assumed that the secondary winding structure is not in a correct relative position and the primary and secondary winding structure are in a misaligned state. In this case, an incorrect relative position or a misaligned state can be detected.

The detection of the correct relative position can e.g. be performed before the actual inductive power transfer is initiated. The proposed detection, however, can be performed while an alternating electromagnetic field is generated by the primary winding structure.

In other words, providing a short circuit of the secondary winding structure can be used to reliably and quickly signalize that the secondary winding structure is correctly positioned with respect to the primary winding structure for an inductive power transfer.

Advantageously, no complicated other signal transmissions and evaluations have to be performed in order to detect the correct position and/or orientation.

Further proposed is a method for detecting an authorized secondary unit of a system for inductive power transfer. The method can be performed by the system according to one of the embodiments described in this invention.

Within the method, a short circuit of the secondary winding structure is provided. Further, an alternating electromagnetic field can be generated by the primary winding structure. Further, a short circuit of the secondary winding structure is detected by a primary-sided system for detecting the short circuit of the secondary winding structure. Further, the an authorized secondary unit is detected if the short circuit of the secondary winding structure is detected.

The proposed method advantageously allows verifying that power is or will be transferred to a selected secondary unit, e.g. a secondary unit which has already provided information on unit-specific transfer requirements.

In another embodiment, an authentication request signal is transmitted from a secondary unit to the primary unit if a short circuit of the secondary winding structure is provided. The authentication request signal can be transmitted before or after the short circuit is/has been provided. It is also possible that the authentication request signal is transmitted simultaneously to the provision of the short circuit.

The at least one primary-sided system for detecting the short circuit of the secondary winding structure is activated if the authentication request signal is received by the primary unit. Further, the primary winding structure can be energized such that an alternating electromagnetic field is generated by the primary winding structure if the authentication signal is received by the primary unit. This means that detection is initiated if the authentication request signal is received.

The authentication request signal can be transmitted via a communication link between the primary and secondary unit. The communication link can e.g. be established during pairing of the primary unit and the secondary unit, wherein the pairing can be performed if the secondary unit approaches the primary unit. In particular, the communication link can be established as soon as the secondary unit enters a predetermined volume around the primary unit.

This advantageously allows a targeted activation of the short circuit and thus a targeted authorization.

In another embodiment, a load provided by a secondary unit of a system for inductive power transfer is sensed, e.g. by a primary-sided means for sensing the load. Further, a short circuit of a secondary winding structure is detected depending on the sensed load, e.g. the sensed load value. The inductive power transfer is deactivated if a short circuit of a secondary winding structure is detected. This advantageously allows a simple and reliable detection of the short circuit. In another embodiment, the short circuit of the secondary winding structure is detected by comparing a set value of the load with an actual value of the load. This has been explained before.

In another embodiment, the short circuit of the secondary winding structure is detected by evaluating a change of the load value over time. This has been explained before.

In another embodiment, the short circuit of the secondary winding structure is provided by at least one means for providing a short circuit of the secondary winding structure. The at least one means can be actively controllable, e.g. by a secondary-sided control unit. This means that the short circuit can be provided on purpose. In this case, providing the short circuit provides a signal for deactivating the power transfer.

In another embodiment, the at least one means for providing the short circuit of the secondary winding structure is controlled by the secondary-sided control unit. The secondary-sided control unit can e.g. control the at least one means such that a short circuit is provided if it is desired to deactivate the inductive power transfer.

In another embodiment a correct relative position between a secondary winding structure and a primary winding structure of a system for inductive power transfer is detected if the short circuit of the secondary winding structure is detected. This has been explained before.

Further described is a primary unit of a system for inductive power transfer, wherein the primary unit comprises at least one means for detecting a short circuit of a secondary winding structure. Further, the primary unit can comprise at least one primary-sided control unit for detecting an authorized secondary unit in a system for inductive power transfer.

Further described is a secondary unit of the system for inductive power transfer, wherein the secondary unit comprises at least one means for providing a short circuit of the secondary winding structure. Further, the primary unit can comprise at least one receiving unit for receiving an authentication request signal transmitted by the secondary unit. The secondary unit can comprise one transmitter unit for transmitting the authentication request signal.

The invention will be described with reference to the attached figures. The figures show:

Fig. 1 a schematic side view of a system for inductive power transfer,

Fig. 2 a schematic circuit diagram of a secondary unit in a first embodiment,

Fig. 3 a schematic circuit diagram of a secondary unit in another embodiment, and

Fig. 4 a schematic flow diagram of the proposed method.

In the following, identical reference numerals denote elements with the same or similar technical features.

Fig. 1 shows a schematic side view of a system 1 for inductive power transfer. The system 1 comprises a primary unit 2, wherein the primary unit 2 is designed as an inductive power transfer pad and installed on the surface 3 of a route. Further, the system 1 comprises a secondary unit 4, wherein the secondary unit 4 is attached to a vehicle 5, in particular a road automobile.

The primary unit 2 comprises a primary winding structure 6. Further, the primary unit 2 comprises a current sensor 7 for sensing an alternating operating current I of the primary winding structure 6. Further, the primary unit 2 comprises an inverter 8 for providing the operating current I. The inverter 8 is connected to an external power supply (not shown). Further, the primary unit 2 comprises a receiver unit 16 for receiving signals transmitted by a secondary-sided transmitter unit 15.

It is, of course, possible that the primary winding structure 6 comprises multiple phase lines, e.g. three phase lines. In this case, the operating current of each phase line can be sensed, e.g. by one current sensor per phase line.

Further, the primary unit 2 comprises a primary-sided control unit 9, wherein the primary- sided control unit 9 is connected to the current sensor 7 by a signal connection. Further, the primary-sided control unit 9 can control an operation of the inverter 8. The primary- sided control unit 9 is connected to the receiver unit 16 by a signal connection.

The secondary unit 4 comprises a secondary winding structure 10. Further, the secondary unit 4 comprises one means 1 1 for providing a short circuit of the secondary winding structure 10 and a secondary-sided control unit 12 for controlling the means 1 1 . The secondary unit 4 comprises a transmitter unit 15 for transmitting signals to the primary unit 2. The secondary-sided control unit 12 is connected to the transmitter unit 15 by a signal connection.

If the operating current I is provided to the primary winding structure 6, an alternating electromagnetic field is generated, wherein said electromagnetic field can be received by the secondary winding structure 4. In this case, the secondary winding structure will provide an AC output voltage which can e.g. be rectified in order to provide a DC voltage to a DC network of the vehicle 5.

If it is desired to provide a short circuit of the secondary winding structure 10, the secondary-sided control unit 12 can control the means 1 1 such that a short circuit of terminals T1 , T2 (see Fig. 2) of the secondary winding structure 10 is provided.

In this case, an effective value of the operating current I of the primary winding structure 6 will increase. Also, a DC input current of the inverter 8 which provides the operating current I will increase. The primary-sided control unit can detect the secondary-sided short circuit based on a gradient of the sensed operating current I and/or based on a

comparison between a set value of the effective current value with the effective value of the sensed operating current I. Alternatively, the primary-sided control unit 9 can detect the secondary-sided short circuit based on a gradient of the sensed input current of the inverter 8 and/or based on a comparison between a set value of said input current value with the value of the sensed input current.

In particular, the short circuit can be detected if the actual current value is higher than the set value by more than a predetermined amount. Alternatively or in addition, the short circuit can be detected if the gradient of the effective current value or sensed current value is higher than a predetermined threshold value. If such a short circuit is detected by the primary-sided control unit 9, the primary-sided control unit 9 can e.g. detect that a selected secondary unit 4 is arranged within an active volume of the primary unit 2. The selected secondary unit 4 can denote a unit which has paired to said primary unit 2 in order to perform inductive power transfer. During or after pairing, power transfer information, e.g. on a desired duration, a desired power etc., can be exchanged between the paired units. The primary-sided control unit 9 can also detect an aligned state or a correct relative position and/or orientation of the primary winding structure 6 to the secondary winding structure 10.

Fig. 2 shows a schematic circuit diagram of a part of an electric circuit of the secondary unit 4 (see Fig. 1 ). Shown is a secondary winding structure 10 with two terminals T1 , T2. Further shown is a rectifier 13, wherein the rectifier comprises a first rectifying leg 13a and a second rectifying leg 13b. The rectifying legs 13a, 13b are electrically connected in parallel. Both rectifying legs 13a, 13b comprise a first diode D1 and a second diode D2 which are connected in series. A first terminal of the first diode D1 is connected to a high potential phase line of a DC network of the vehicle 5. A second terminal of the first diode D1 is connected to a first terminal of a second diode D2 and to one of the terminals T1 , T2 of the secondary winding structure 10. A second terminal of the second diode D2 is connected to a low potential phase line of the DC network. The DC network comprises an intermediate circuit capacitor C. Further indicated is a DC current l_DC in the DC network and a DC output voltage U_DC of the rectifier 13.

Further indicated is a switching element 14, wherein the first terminal T1 and the second terminal T2 of a secondary winding structure 10 are electrically connectable by the switching element 14. If the switching element 14 is in a closed state, the terminals T1 , T2 are galvanically connected and a short circuit of the secondary winding structure 10 is provided. If the switching element 14 is in an open state, the terminals T1 , T2 of the secondary winding structure 10 are not electrically connected via the switching element 14.

The switching element 14 can be controlled by the secondary-sided control unit 12 (see Fig. 1 ).

Fig. 3 shows a schematic circuit diagram of a part of an electric circuit of the secondary unit 4 (see Fig. 1 ) in another embodiment. The circuit is mainly designed similar to the circuit shown in Fig. 2. Thus, it can be referred to the explanation concerning Fig. 2. In contrast to the embodiment shown in Fig. 2, the shown circuit comprises a first switching element 14a and a second switching element 14b. The first switching element 14a is electrically connected in parallel to the second diode D2 of the first rectifying leg 13a. The second switching element is electrically connected in parallel to the second diode D2 of the second rectifying leg 13b. In this case, the terminals T1 , T2 of the secondary winding structure are electrically connected if both switching elements 14a, 14b are in a closed state. The terminals are not electrically connected via the switching elements 14a, 14b if at least one, preferably both, switching elements 14a, 14b are in an open state.

It is clear to the skilled person that the switching elements 14a, 14b can also be arranged in parallel to the first diode D1 of each rectifying leg 13a, 13b.

Fig. 4 shows a schematic flow diagram of the proposed method.

In a first step S1 , a pairing request signal PRS is transmitted from the vehicle 5 (see Fig. 1 ) to the primary unit 2. The pairing request signal PRS can e.g. be transmitted via a secondary-sided transmitter unit 15. The pairing request signal PRS can be received by a primary-sided receiver unit 16. In a second step S2, an acknowledge pairing request signal APRS can be transmitted from the primary unit 2 to the secondary unit 4, e.g. via the primary-sided and secondary-sided transceivers 15, 16. After the second step S2, the primary unit 2 and the secondary unit 4 can denote paired units.

In a third step S3, a secondary-sided control unit 12 can generate an authentication request signal ARS and transmit said authentication request signal ARS via the secondary-sided transceiver 15 to the primary unit 2. The primary unit 2 can receive the authentication request signal ARS by the primary-sided transceiver 16. In a fourth step, an acknowledge authentication request signal AARS can be transmitted from the primary unit 2 to the secondary unit 4, e.g. via the respective transceivers 15, 16. Simultaneously, an activation signal ASCD for activating a detection of a short circuit of the secondary winding structure 10 ASCD can be generated.

If the acknowledge authentication request signal AARS is received by the secondary- sided transceiver 15, the secondary-sided control unit 12 can control the means 1 1 for providing a short circuit of the secondary winding structure 10 such that the short circuit is provided. This can be performed in a fifth step. After the activation or simultaneously to the activation, an acknowledge activation signal AAS can be transmitted from the secondary unit 4 to the primary unit 2. If the acknowledge activation signal AAS is received by the primary unit 2, e.g. via the primary-sided transceiver 16, an activation signal AIP for activating an inductive power transfer can be generated in a sixth step. The inductive power transfer can alternatively be activated if or after the detection of the short circuit has been activated, i.e. independent of the reception of the acknowledge activation signal AAS.

It is possible to generate an alternating electromagnetic field with a nominal power or with a reduced power.

In a seventh step, a detection of a short circuit of the secondary winding structure 10 can be performed. This can mean that the operational state of the secondary winding structure 10 is monitored with respect to a short circuit. If the short circuit of the secondary winding structure 10 is detected, e.g. by the primary-sided control unit 9, it is detected that the secondary unit 4 is the secondary unit 4 of the paired units. In other words, it is detected that the secondary unit 4 is authorized for inductive power transfer between the units. Further, a correct relative position of the secondary winding structure 10 and the primary winding structure 6 is detected. In this case, a vehicle authentication signal VAS can be transmitted to the secondary unit 4. Further, the inductive power transfer process can be authorized or enabled. If no short circuit of the secondary winding structure 10 is detected by the primary-sided control unit 9, inductive power transfer can be terminated or prevented. In this case, a vehicle unauthorized signal VUAS can be transmitted from the primary unit 2 to the secondary unit 4.

In this case, the inductive power transfer process will not be authorized or enabled.

Claims

1 . A system for detecting an authorized secondary unit (4) of a system (2) for inductive power transfer, wherein the system comprises at least one means (1 1 ) for providing a short circuit of a secondary winding structure (10), wherein the system comprises at least one primary-sided system for detecting the short circuit of the secondary winding structure (10), wherein an authorized secondary unit (4) is is detectable if a short circuit of the secondary winding structure (10) is detected.

2. The system of claim 1 , characterized in that wherein the system comprises at least one secondary-sided signal transmitter unit (15) for transmitting an authentication request signal (ARS) and at least one primary-sided signal receiver unit (16) for receiving the authentication request signal (ARS), wherein the at least one primary- sided system for detecting the short circuit of the secondary winding structure (10) is activatable if the authentication request signal (ARS) is received.

3. The system of claim 1 or 2, characterized in that the system comprises at least one primary-sided control unit (9) and at least one primary-sided load sensing means for sensing a load provided by the secondary unit (4), wherein the short circuit of the secondary winding structure (10) is detectable by the primary-sided control unit (9) depending on the sensed load.

4. The system according to claim 3, characterized in that the load sensing means

comprises a current sensing means (7) for sensing at least one operating current (I) of the primary winding structure (6) or for sensing an input current of an inverter (8), wherein the inverter (8) provides the at least one operating current (I).

5. The system according to one of the claims 3 or 4, characterized in that the short circuit of the secondary winding structure (10) is detectable by comparing a set value of the load with an actual value of the load.

6. The system according to one of the claims 3 to 5, characterized in that the short circuit of the secondary winding structure (10) is detectable by evaluating a change of the load value over time.

7. The system according to one of the preceding claims, characterized in that the system comprises at least one secondary-sided control unit (12) for controlling the at least one means (1 1 ) for providing the short circuit of the secondary winding structure (10).

8. The system according to claim 7, characterized in that the at least one means (1 1 ) for providing the short circuit of the secondary winding structure (10) comprises at least one switching element (14, 14a, 14b), wherein terminals (T1 , T2) of the secondary winding structure (10) are connectable by the at least one switching element (14, 14a, 14b).

9. The system according to claim 8 characterized in that the at least one switching

means (1 1 ) is integrated into a secondary-sided rectifier (13).

10. The system according to claim 9, characterized in that the secondary-sided rectifier (13) is provided by two rectifying legs (13a, 13b), wherein the rectifying legs (13a, 13b) are arranged electrically parallel to one another, wherein each rectifying leg (13a, 13b) comprises two diodes (D1 , D2), wherein one switching element (14a, 14b) is connected electrically in parallel to at least one diode (D1 , D2) of rectifying leg (13a, 13b).

1 1 . The system according to one of the preceding claims, characterized in that a correct relative position between a secondary winding structure (10) and a primary winding structure (6) of a system (2) for inductive power transfer is detected if the short circuit of the secondary winding structure (10) is detected.

12. A method for detecting an authorized secondary unit (4) for inductive power transfer, wherein a short circuit of the secondary winding structure (10) is provided, wherein the short circuit of a secondary winding structure (10) is detected by a primary-sided system for detecting the short circuit of the secondary winding structure (10), wherein an authorized secondary unit (4) is detected if the short circuit of the secondary winding structure (10) is detected.

13. The method according to claim 12, characterized in that an authentication request signal (ARS) is transmitted from the secondary unit (4) to the primary unit (2) if a short circuit of the secondary winding structure (10) is provided, wherein the at least one primary-sided system for detecting the short circuit of the secondary winding structure (10) is activated if the authentication request signal (ARS) is received by the primary unit (2).

14. The method according to claim 12 or 13, characterized in that a load provided by a secondary unit (4) of a system for inductive power transfer is sensed, wherein a short circuit of a secondary winding structure (10) is detected depending on the sensed load.

15. The method of claim 14, characterized in that the short circuit of the secondary

winding structure (10) is detected by comparing a set value of the load with an actual value of the load.

16. The method of claim 14 or 15, characterized in that the short circuit of the secondary winding structure (10) is detected by evaluating a change of the load value over time.

17. The method of one of the claims 12 to 16, characterized in that the short circuit of the secondary winding structure (10) is provided by at least one means for providing a short circuit of the secondary winding structure (10).

18. The method of claim 17, characterized in that the at least one means for providing the short circuit of the secondary winding structure (10) is controlled by a secondary- sided control unit (12).

19. The method according to one of the claims 12 to 18, characterized in that a correct relative position between a secondary winding structure (10) and a primary winding structure (6) of a system (2) for inductive power transfer is detected if the short circuit of the secondary winding structure (10) is detected.