Charging station for an electric vehicle

Abstract

Charging station for transferring energy from the charging station to an electrically powered vehicle wirelessly coupled to the charging station, comprising a connection for an electrical energy source, an inverter, and an electronic coil connected to the inverter for providing the energy for the wireless energy coupling by means of an alternating magnetic field, for the purpose of which the inverter is configured to supply the electronic coil with an alternating electrical voltage in resonant operation, wherein the charging station has a detection unit and a control unit, wherein the detection unit is configured to detect a vehicle-side load shedding or the removal of the electrically powered vehicle during the wireless energy coupling of the electrically powered vehicle and to provide a fault signal.for what purpose the detection comprises a comparison of the time derivative of a parameter relating to energy transfer with a reference value, wherein the parameter is formed by a phase shift between a coil current of the electronic coil and the alternating voltage supplied by the inverter to the electronic coil, and the control unit is configured to terminate the supply of energy by means of the alternating magnetic field on account of the disturbance signal.

Description

The present invention relates to a charging station for transmitting energy from the charging station to an electrically drivable vehicle which is wirelessly energy-coupled to the charging station, having a connection for an electrical energy source, an inverter and an electronic coil which is connected to the inverter for providing the energy for the wireless electrical coupling by means of an alternating magnetic field, for which purpose the inverter is configured to apply an electrical alternating voltage to the electronic coil in a resonant mode. In addition, the invention relates to a method for transferring energy from a charging station to an electrically drivable vehicle which is wirelessly energy-coupled to the charging station, wherein the energy is transferred from the charging station to the electrically drivable vehicle by means of an alternating magnetic field provided by an electronic coil, for which purpose the electronic coil is supplied with an alternating electrical voltage by means of an inverter in a resonant mode and the charging station draws electrical energy from an electrical energy source. Finally, the invention also relates to a computer program product comprising a program for a computer unit of a charging station.Charging stations of the generic type and methods for their operation for wirelessly transmitting energy by means of an alternating magnetic field are basically known, so that a separate publication proof is not required for this. Charging stations of the generic type serve to supply an electrically drivable vehicle with energy during a charging operation, so that the electrically drivable vehicle can perform its intended function. The electrically drivable vehicle requires the energy for the driving operation.The energy is provided by means of the alternating magnetic field of the charging station, which is in turn connected to an electrical energy source, for example to a public energy supply network, to an electrical generator, to a battery and / or the like. The charging station generates the alternating magnetic field while absorbing electrical energy from the electrical energy source. The electrically drivable vehicle detects the alternating magnetic field by means of a suitable coil arrangement, draws energy therefrom and provides electrical energy on the vehicle side, in particular in order to supply an electrical energy store of the vehicle and / or an electrical machine of a drive device of the vehicle with electrical energy.One possibility for supplying the energy from the charging station to a charging device of the vehicle is that an electrical connection is established as an energy-related coupling by means of a cable between the vehicle and the charging station. In this sense, DE 10 2009 034 887 A1 discloses a device and a method for providing an amount of energy in a charging station for an electric vehicle, and DE 20 2011 004 515 U1 discloses a device for safe operation of a charging station with feedback. Furthermore, it is known to produce a wireless energy coupling according to a further possibility, which avoids a complicated mechanical connection by means of cables. For this purpose, a coil circuit with at least one electronic coil is generally provided on the charging station side and on the vehicle side, which coil circuits are arranged substantially opposite one another during a charging process and enable energy-related coupling using an alternating magnetic field. Such an arrangement is known, for example, from KR 10 2012 0 016 521 A. Furthermore, DE 10 2010 042 395 A1 discloses methods and systems for inductively charging a battery of a vehicle. Furthermore, US 2011 / 0 074 346 A1 discloses a vehicle charge safety system and a method. Finally, US 2013 / 0 249 480 A1 discloses a system and a method for inductively transmitting AC voltage power and self-alignment between a vehicle and a charging station. In systems in which energy is transmitted by means of an alternating magnetic field, also called inductive energy transmission, changes in the energy loss can occur on the vehicle side during the charging process, which are not caused by the charging station and are therefore not known on the charging station side. If, for example, the electrically drivable vehicle is an electric vehicle or else a hybrid vehicle, a disconnection of an electrical energy store, in particular of an accumulator of the electrically drivable vehicle, can occur during the charging process. For example, the rechargeable battery can be separated from an electrical installation of the electrically drivable vehicle by a contactor, which separation can be effected for a wide variety of reasons. In such a case, also called load shedding, energy is still transmitted to the electrically drivable vehicle on the charging station side, which can result, inter alia, in a rapid increase in an electrical voltage on the vehicle side. As a result, vehicle-side power electronics which are required for the intended operation of the electrically drivable vehicle can be damaged. Other vehicle-side system components may also be damaged.In the prior art, it is known to provide a protective circuit on the vehicle side in such a case in the form of an overvoltage protection which limits the voltage level on the vehicle side. Such protective circuits, however, are generally operable only for a limited time. An electrical disconnection of the vehicle-side power electronics from further components of the electrically drivable vehicle must then take place, for example by means of fuses or the like.It is also known to determine the load shedding on the vehicle side and to report it to the charging station via a communication channel. For this purpose, either a measurement of the load shedding or an evaluation of a corresponding signal causing the load shedding can be used on the vehicle side. On the load station side, the provision of energy can then be ended or limited. In this scenario, it has proven to be disadvantageous that a comparatively long time elapses until the message to the charging station is received. During this period of time, the charging station continues to provide energy by means of the alternating magnetic field, i.e. continues to record power on the vehicle side. For this reason, a correspondingly suitable fast communication channel between the charging station and the electrically drivable vehicle is required. Moreover, high demands must be made on this communication channel and it is critical to safety.The previously known procedures thus initially include overvoltage protection, which must be coupled to a still very fast and reliable communication channel. This is not only expensive, but can also be susceptible to faults, in particular if one charging station or even a plurality of charging stations supply a plurality of electrically drivable vehicles with energy in parallel in the spatial vicinity.It is therefore the object of the invention to improve a charging operation.As a solution, the invention proposes a charging station according to independent claim 1. Moreover, the invention proposes a method for operating a charging station according to the further independent claim 2. Finally, the invention proposes a computer program product according to the further independent claim 5. Further advantageous embodiments of the invention result from features and characteristics of the dependent claims.On the device side, the invention proposes in particular that the charging station has a detection unit and a control unit, wherein the detection unit is configured to detect a fault with respect to the transmission of the energy during the wireless energy coupling of the electrically drivable vehicle and to provide a fault signal, and the control unit is configured to end the provision of the energy by means of the alternating magnetic field on the basis of the fault signal. Accordingly, it is proposed in particular on the method side that a fault with respect to the transmission of the energy is detected during the wireless energy coupling of the electrically drivable vehicle and the provision of the energy is ended by means of the alternating magnetic field.The invention thus uses charging station-side parameters in order to be able to detect a load shedding on the vehicle, for example. A separate communication channel and detection means in the electrically drivable vehicle can thus be dispensed with. Furthermore, the fact that a communication channel is no longer required also results in a higher reliability and interference resistance, because an information transmission via the communication channel can be completely omitted. Consequently, all the disadvantages associated therewith are also dispensed with. In addition, costs and effort can of course also be saved as a result. Nevertheless, the communication channel can of course also be used, if appropriate, together with vehicle-side detection means, in order to be able to realize, for example, redundancy or the like.Compared to the prior art, the invention uses properties of the physical coupling of a system formed from the charging station and the electrically drivable vehicle during charging. Load shedding represents a significant system change in such a system. The invention uses the fact that such a system change can be detected on the basis of greatly changing charging station-side parameters or system variables.For this purpose, the detection unit can have a corresponding sensor, with which the corresponding charging station-side parameter can be measured. In addition, the detection unit can of course also be formed integrally with the control unit. Both components can be integrated either individually or jointly into a controller for the inverter. Both the detection unit and the control unit can be formed by an electronic circuit which can have, for example, a hardware circuit, but also a computer unit, combinations thereof and / or the like.According to the invention, the disruption with respect to the transmission of the energy consists in the load shedding on the vehicle side or the removal of the electrically drivable vehicle, whereupon the wireless energy coupling of the electrically drivable vehicle can be ended. In particular, the alternating voltage provided by the inverter can be switched off for this purpose, whereupon the provision of the alternating magnetic field by the electronic coil is ended.If the detection unit detects a corresponding fault, it preferably generates a fault signal, which it makes available for further use of the charging station, in particular the control unit. The control signal can be an electrical signal, which can be, for example, an analog signal, but also a digital signal. The fault signal preferably engages in a controller for the inverter and inhibits or ends the intended operation of the inverter.The invention takes into account that, on the charging station side, the inverter with the electronic coil is operated in particular in resonant operation. This means that the optimum operating frequency or the frequency of the electrical alternating voltage provided by the inverter is significantly influenced by properties of the alternating magnetic field generated by the electronic coil. The resonant mode is achieved in that a capacitor is additionally connected to the electronic coil. The capacitor can be connected to the electronic coil, for example, in series connection, but also in parallel connection.Inductive energy transmission or wireless energy-related coupling in the sense of the invention is a coupling for the purpose of transmitting energy, which enables at least unidirectional transmission of energy from an energy source to an energy sink. The energy source can be, for example, a public energy supply network, an electrical generator, a solar cell, a fuel cell, a battery, combinations thereof and / or the like. The energy sink can be, for example, a drive device of the electrically drivable vehicle, in particular an electric machine of the drive device and / or an electrical energy store of the drive device, for example an accumulator or the like. However, a bidirectional energy transmission can also be provided, that is to say an energy transmission alternately in both directions. For this purpose, the charging station serves, among other things, which is intended to transmit energy to the electrically drivable vehicle, for which purpose it draws electrical energy from an energy source to which it is electrically connected.Wireless energy-related coupling or inductive energy transfer in the sense of the invention means that no mechanical connection for establishing an electrical coupling needs to be provided between the charging station and the electrically drivable vehicle. In particular, the establishment of an electrical connection by means of a cable can be avoided. Instead, the energy-related coupling takes place essentially solely on the basis of an energy field, preferably an alternating magnetic field.The charging station is therefore configured to generate a corresponding energy field, in particular an alternating magnetic field. On the vehicle side, it is correspondingly provided that such an energy field or alternating magnetic field can be detected and energy for the intended operation of the electrically drivable vehicle is obtained therefrom. By means of the charging device of the vehicle, the energy supplied by means of the energy field, in particular the alternating magnetic field, is converted into an electrical energy which can then preferably be stored in the energy store of the vehicle for its intended operation. For this purpose, the charging device can have a converter which converts the electrical energy drawn from the alternating magnetic field by means of the coil and supplied to the converter into an electrical energy suitable for the vehicle, for example aligns, voltage converts or the like. In addition, the energy can also be supplied directly to the electric machine of the drive device of the vehicle. The energy coupling thus essentially serves for the transmission of energy and not, at the very front, for the transmission of information. Accordingly, the means for implementing the invention are designed for a correspondingly high power throughput as opposed to a wireless communication link.An essential element for wireless energy-related coupling, in particular by means of the alternating magnetic field, is the electronic coil, which can occasionally also be formed by a plurality of electronic coils, which serves on the charging station side for generating the alternating magnetic field and is flooded on the vehicle side by the alternating magnetic field and provides an electrical energy on the vehicle side at its corresponding connections. Accordingly, the electronic coil is charged on the charging station side with an alternating voltage that brings about an alternating current, so that the electronic coil provides the alternating magnetic field, by means of which energy can be emitted. The electronic coil of the charging station is coupled to the electronic coil of the electrically drivable vehicle during the charging process via the alternating magnetic field.As a rule, the coil has a winding with a plurality of turns of an electrical conductor, wherein the winding generally comprises or encloses a ferromagnetic body, which is frequently formed by a ferrite. The magnetic flux can be guided in a desired manner by means of the ferromagnetic body, so that the effectiveness of the energy-related coupling can be enhanced on the basis of the alternating magnetic field between the coil circuits of the charging station and the electrically drivable vehicle.The electrical conductor of the electronic coil forming the windings is frequently designed as a so-called high-frequency stranded wire, that is to say it consists of a multiplicity of individual conductors or wires which are electrically insulated from one another and are correspondingly combined to form the conductor. This achieves that in frequency applications such as in the invention a current displacement effect is reduced or substantially avoided. In order to be able to improve the most uniform possible current distribution to the individual wires of the high-frequency stranded wire, a twisting of the individual wires is generally also provided. The twisting may also involve forming bundles of a certain number of individual wires twisted on themselves, and these bundles, forming the electrical conductor, are also twisted.The detection comprises a comparison of a parameter relating to the energy transmission and / or a change of the parameter with a comparison value. In particular, a differential change can be evaluated. For this purpose, the detection circuit can comprise a suitable comparison circuit which can provide the desired functions. The comparison value can be permanently predefined, but it can also be adjustably predefined. The latter makes it possible to adapt the charging station individually. The invention preferably uses the fact that the parameter, in particular its change, is carried out more quickly than a regulation of the optimum operating frequency. As a result, a clear signal for evaluation by means of the detection unit can be achieved.According to the invention, the parameter is formed by a phase shift between the coil current of the electronic coil and an AC voltage provided by the inverter for the electronic coil. This makes it possible to achieve reliable detection of the fault with respect to the transmission of the energy.In addition, alternatively or additionally, the parameter can be formed by a frequency of the alternating voltage, in particular of the operating frequency. Furthermore, the parameter can also be formed by an input current of the charging station, in particular an active power determined therefrom and / or the like. The input current of the charging station is the current provided by the energy source to which the charging station is connected.Accordingly, the invention also comprises a computer program product of the generic type, wherein the product has program code sections of a program for executing the method according to the invention when the program is executed by the computer unit of the control device. The aforementioned computer program product can be embodied as a computer-readable storage medium. In addition, the program can be directly loadable into an internal memory of the computer unit. It is thus possible, for example, to download the program from a network from a data source, for example a server, and to load it in an internal memory of the computer unit, so that the computer can execute the program.The computer program preferably comprises a computer-readable medium on which the program code sections are stored. Such a computer-readable medium can be, for example, a memory module, a compact disc, a USB stick or the like.Further advantages and features can be gathered from the following description of an exemplary embodiment with reference to the FIG. In the FIGS., like components and functions are denoted by like reference numerals.The following are shown: FIG. 1 schematically shows a representation of a change of a current phase position during a load shedding during a charging operation of an electrically drivable vehicle at a charging station according to the invention, FIG. 2 shows a schematic illustration of a phase profile in the case of load shedding as in FIG. 1 without a disconnection according to the invention, and FIG. 3 shows a schematic illustration of a time-differentiated signal profile of the phase profile illustrated in FIG. 2, which signal profile represents a signal detectable by means of a detection unit.The following exemplary embodiment is based on a charging station for transmitting energy from the charging station to an electrically drivable vehicle which is wirelessly energy-coupled to the charging station, and which are not illustrated in the FIGS. The charging station has a connection for an electrical energy source, which in the present case is a public energy supply network. Furthermore, the charging station comprises an inverter and an electronic coil connected to the inverter for providing the energy for the wireless energy coupling by means of an alternating magnetic field. For this purpose, the inverter is configured to apply an electrical alternating voltage to the electronic coil in a resonant mode.The charging station has a detection unit and a control unit, wherein the detection unit is configured to detect a fault with respect to the transmission of the energy during the wireless energy coupling of the electrically drivable vehicle. If a corresponding fault is detected, the detection unit provides a fault signal. The fault signal is available to the control unit.The control unit is configured to end the provision of the energy by means of the alternating magnetic field on the basis of the interference signal. For this purpose, it is provided that the control unit stops the operation of the inverter, so that the latter no longer provides an alternating voltage for the electronic coil. Thereupon, an alternating magnetic field is no longer generated by means of the electronic coil. The provision of energy for the electrically drivable vehicle is thus ended.The detection of the detection unit is effected in the present case by comparing a parameter relating to the energy transmission, in particular in the present case a change of this parameter with respect to a comparison value. In the present exemplary embodiment, a phase shift between a coil current of the electronic coil and the alternating voltage provided by the inverter for the electronic coil is a parameter.Alternatively or additionally, the parameter can also be formed by a frequency of the alternating voltage or also by an input current of the charging station.FIG. 1 shows, by way of example, for this exemplary embodiment a change in the current phase shift in the event of a load jump on the vehicle side from 15 Ohm to 500 Ohm. In the diagram shown in FIG. 1, the angle of the phase shift is indicated in degrees on the ordinate. The abscissa represents the frequency of the alternating voltage provided by the inverter in kHz. A first graph 10 shows the phase shift at a vehicle-side load resistance of 500 ohms by means of a first graph 10. The phase shift is thus very high.It can also be seen from FIG. 1 that, with a load resistance of 15 ohms on the vehicle, the phase shift at 130 kHz is in the range of -65 degrees. Although the phase shift also increases as the frequency increases up to positive values, the phase shift always remains below the phase shift which is present at a load resistance of 500 ohms. This is illustrated by the graph 12.If, at a frequency of 155 kHz, for example, a load jump from 15 ohms to 500 ohms occurs, because an accumulator is switched off on the vehicle side, the phase shift jumps from approximately 20 degrees to approximately 80 degrees, which is illustrated by the arrow 14. The invention makes use of detecting this phase jump and detecting therefrom the disturbance with respect to the transmission of the energy during the wireless energy coupling of the electrically drivable vehicle.If a change in the load conditions therefore occurs on the vehicle side, this leads to a change in the phase position. If this change takes place more quickly than a dynamic of the controller on the charging station side for stabilizing the phase position, this system change can be clearly detected and can be very probably attributed to a load shedding on the vehicle side. FIG. 2 shows the corresponding principal profile of the phase position or phase shift in the case of load shedding with respect to this exemplary embodiment if no disconnection were to take place. For better characterization of the change that has occurred, it can additionally be provided to filter the ascertained change by a differentiating element with delay (DT1 element).FIG. 3 shows the corresponding change in the phase shift. On the basis of this measurable information, it is possible to distinguish between undisturbed operation, in which phase changes are to be compensated normally, and disturbed operation, which occurs in the case of load shedding.In FIGS. 2 and 3, the abscissas are time axes on which points in time t I, t II, t III and t IV are plotted. These times form regions I, II, III and IV.In FIG. 2, the angle of the phase shift φ is shown on the ordinate, whereas in FIG. 3, its time derivative is shown on the ordinate, namely dφ / dt. FIG. 2 shows in the region I the phase shift and its change during intended operation during charging of the electrically drivable vehicle by means of the charging station. In the region II, the load is discharged on the vehicle side. In the area III, new system parameters are reached which result in a corresponding phase shift. If there is no prompt shutdown of the energy transmission, then the area IV of a regulating process begins by means of a phase controller of the charging station. This leads to a lowering of the phase position and to an increase of the energy transmission, resulting in a corresponding voltage increase on the vehicle side.The rapid change in region II can be seen very well (FIG. 3 ). On account of this change, the power transmission can be switched off. This time t aus is reached when dφ / dt reaches a detection threshold. The time between load shedding and termination of the provision of the energy by means of the alternating magnetic field is limited only by the time for detecting the measured variables or parameters, the filtering of the phase position and the time delay for blocking control signals of the inverter and can lie in the range of a few microseconds.In another exemplary embodiment, it can be provided that the monitoring of an input current of the charging station or also of a frequency of the alternating voltage provided by the inverter can be monitored in addition.The invention achieves a targeted monitoring of the temporal behavior of certain charging station-side parameters in order to increase the operating reliability, in particular the operating reliability of the electrically drivable vehicle. A separate communication channel is not required between the charging station and the electrically drivable vehicle and a detection unit on the vehicle side.The foregoing embodiment is intended to explain the invention and not to limit it. Of course, the skilled person will provide corresponding variations if necessary without departing from the core idea of the invention.Of course, individual features can also be combined with one another in any desired manner as required. Moreover, of course, device features can also be specified by corresponding method steps and vice versa.

Claims

Charging station for transmitting energy from the charging station to an electrically drivable vehicle which is wirelessly energy-connected to the charging station, having a connection for an electrical energy source, an inverter and an electronic coil which is connected to the inverter for providing the energy for the wireless energy-connection by means of an alternating magnetic field, for which purpose the inverter is configured to apply an alternating electrical voltage to the electronic coil in a resonant mode, wherein the charging station has a detection unit and a control unit, wherein the detection unit is configured to detect a load shedding on the vehicle side or the removal of the electrically drivable vehicle during the wireless energy-connection of the electrically drivable vehicle and to provide a fault signal, for which purpose the detection comprises comparing the time derivative of a parameter relating to the energy transmission with a comparison value, wherein the parameter is formed by a phase shift between a coil current of the electronic coil and the alternating voltage provided by the inverter for the electronic coil, and the control unit is configured to end the provision of the energy by means of the alternating magnetic field on the basis of the interference signal.Method for transmitting energy from a charging station to an electrically drivable vehicle which is wirelessly energy-connected to the charging station, wherein the energy is transmitted from the charging station to the electrically drivable vehicle by means of an alternating magnetic field provided by an electronic coil, for which purpose the electronic coil is supplied with an alternating electrical voltage by means of an inverter in a resonant mode and the charging station draws electrical energy from an electrical energy source, wherein a load shedding on the vehicle side or the removal of the electrically drivable vehicle is detected during the wireless energy-connection of the electrically drivable vehicle and the provision of the energy is ended by means of the alternating magnetic field, wherein the detection comprises a comparison of the time derivative of a parameter relating to the energy transmission with a comparison value, wherein the parameter is formed by a phase shift between a coil current of the electronic coil and the alternating voltage provided by the inverter for the electronic coil.Method according to Claim 2, characterized in that the parameter is formed by a frequency of the alternating voltage.Method according to Claim 2 or 3, characterized in that the parameter is formed by an input current of the charging station.Computer program product comprising a program for a computer unit of a charging station (10), wherein the program has program code sections of a program for executing the steps of a method according to one of Claims 2 to 4 when the program is executed by the computer unit.Computer program product according to Claim 5, characterized in that the computer program product comprises a computer-readable medium on which the program code sections are stored.Computer program product according to Claim 5 or 6, characterized in that the program can be loaded directly into an internal memory of the computer unit.

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