DE102021205102A1 - Method for inductive energy transfer between a vehicle and a supply network, vehicle, inductive charging device and system - Google Patents

Abstract

The invention relates to a method for inductive energy transmission between a vehicle (50) and a supply network (60), with a vehicle-side coil (3) being arranged on a network-side coil (22) arranged outside the vehicle (50), with a resonant frequency (ƒr ) a resonant converter (10) formed by the coils (3, 22) arranged next to one another, a vehicle-side converter (2) connected to the vehicle-side coil (3) and a line-side converter (21) connected to the line-side coil (22), and wherein the converters (2, 21) are controlled on the vehicle side and/or on the network side in such a way that the resonant converter (10) is operated at the specific resonant frequency (ƒr) during the inductive energy transmission. The invention also relates to a vehicle (50), inductive charging device (20) and a system (1).

Description

The invention relates to a method for inductive energy transmission between a vehicle and a supply network, a vehicle, an induction charging device and a system.

Inductive energy transmission systems offer a number of advantages when setting up a charging infrastructure for electrified vehicles: They can be easily integrated into the ground in many places, so that they hardly change the cityscape. For a customer who uses such a charging infrastructure, an inductive charging device is usually not visible and the charging process itself is hardly perceptible. In contrast to conductive charging, no cables are required, which can become a tripping hazard. Cable connections in public spaces can also be a target for vandalism, sabotage and theft. With an inductive energy transmission system, on the other hand, there are hardly any possibilities for manipulation. Since this transmission system hardly changes the cityscape, the system can also be installed much more frequently and therefore more widely than conductive charging systems. This makes it possible for the vehicle to be connected to an inductive energy transmission system much more frequently than to a conductive charging system over the course of a year. This statistically more frequent connection of the vehicle to the inductive system also offers advantages if a vehicle battery is used for the purposes of grid stabilization and active and reactive power control. For this, however, it would be necessary for the energy transmission system to be able to work bidirectionally.

An inductive power transmission system for vehicles has a coil on the vehicle side and a coil on the mains side, which are separated from one another by an air gap. For example, the vehicle-side coil can be arranged on an underside of the vehicle, the mains-side coil can, for example, be arranged in a subsurface, for example embedded in a roadway, so that the vehicle-side coil can be arranged above the mains-side coil by suitably selecting the parking position of the vehicle. The greatest challenge with regard to energy transmission is overcoming the clearance between the coil on the vehicle side and the coil on the mains side. In particular, depending on the parking or stopping position of the vehicle, there is a different spatial offset of the coils relative to one another. For power electronics of converters that are used to operate the coils on both sides, there are always different magnetic circuits in different charging situations.

From B. Weber, T. Brandt and A. Mertens, Compensation of switching dead-time effects in voltage-fed PWM inverters using FPGA-based current oversampling, 2016 IEEE Applied Power Electronics Conference and Exposition (APEC), Long Beach, CA, USA, 2016, pp. 3172-3179, doi: 10.1109/APEC.2016.7468318, a method for dead time compensation is known.

The invention is based on the object of creating a method for inductive energy transmission between a vehicle and a supply network and a vehicle, an inductive charging device and a system in which inductive energy transmission is improved.

The object is achieved according to the invention by a method having the features of patent claim 1, a vehicle having the features of patent claim 8, an inductive charging device having the features of patent claim 9 and a system having the features of patent claim 10. Advantageous configurations of the invention result from the dependent claims.

In particular, a method for inductive energy transmission between a vehicle and a supply network is provided in a first aspect, with a vehicle-side coil being arranged on a network-side coil arranged outside of the vehicle, with a resonant frequency of one through the coils arranged next to one another, one with the vehicle-side Coil-connected vehicle-side converter and a network-side converter connected to the network-side coil connected resonant converter is determined, and
wherein the converters are controlled on the vehicle side and/or on the network side in such a way that the resonant converter is operated at the specific resonant frequency during the inductive energy transmission.

Furthermore, in a second aspect, a vehicle is created, comprising an on-board converter set up to convert at least one AC voltage into a DC voltage, a vehicle-side coil which is electrically connected to the on-board converter and which is set up and arranged in such a way that the on-board coil can be arranged to form a resonant converter on a mains-side coil arranged outside the vehicle, and a control device, wherein the control device is set up to determine or to obtain a resonant frequency of a resonant converter designed in this way and the To control the converter in such a way that the resonant converter is operated at the specific resonant frequency during the inductive energy transfer.

Furthermore, in a third aspect, an induction charging device for a supply network is created, comprising a network-side converter, set up for converting at least one DC voltage into an AC voltage, a network-side coil which is electrically connected to the network-side converter and which is set up and arranged in such a way that the mains-side coil can be arranged on a vehicle-side coil arranged in or on a vehicle to form a resonance converter, and a control device, wherein the control device is set up to determine or to obtain a resonance frequency of a resonance converter designed in this way and to control the mains-side converter in such a way, that the resonant converter is operated at the specific resonant frequency during the inductive energy transfer.

In a fourth aspect, a system for inductive energy transmission between a vehicle and a supply network is created, comprising a vehicle according to the second aspect and an inductive charging device according to the third aspect.

The method, the vehicle, the inductive charging device and the system make it possible to improve inductive energy transmission. In particular, efficiency can be improved since reactive power can be reduced by operating the resonance converter at its resonance frequency. Ideally, a total impedance of a resonant circuit of the resonant converter when operating at the resonant frequency effectively only has an ohmic component, since an inductive component of a leakage inductance with a capacitive component, which is formed in particular by vehicle-side and network-side tuning capacitors, compensate each other at the resonant frequency.

In principle, the method and the system can be used for inductive energy transmission in both directions, so that both inductive charging of a vehicle and network stabilization or support of the supply network using electrical energy stored in a vehicle battery is possible. In the case of inductive charging of the vehicle, the system for inductive energy transmission includes, in particular on the network side, a DC voltage converter fed by a low-voltage network (e.g. three-phase, 230 V effective, 400 V conductor-conductor), which on the output side feeds a network-side intermediate circuit capacitance with a DC voltage. This voltage is coupled via a (series) resonant converter to a DC voltage of an intermediate circuit capacitance on the vehicle side. A DC-DC converter connected downstream of this vehicle-side intermediate circuit capacitance undertakes a voltage adjustment and supplies a traction battery of the vehicle. The resonant converter is formed in particular by a line-side converter in the form of an inverter, a line-side tuning capacitor, a line-side coil, a vehicle-side coil, a vehicle-side tuning capacitor and a vehicle-side converter in the form of a rectifier. An air gap is formed between the line-side coil, which is arranged, for example, in a subsurface under the vehicle, and the vehicle-side coil. Since the coils can be offset from one another due to varying parking positions of the vehicle, they are magnetically incompletely coupled to varying degrees depending on the offset. The transformer formed from the coils therefore has leakage inductances which represent leakage fluxes. In order to optimize energy transmission via the air gap, the resonant converter has a tuning capacitor, in particular on both sides of the air gap, with which a series compensation of the transformer leakage inductances can be brought about. If the resulting resonant circuit in the resonant converter is operated or controlled at its resonant frequency, the reactive components of the tuning capacitor and stray inductance located in series compensate each other and the resulting resonant converter exhibits an ohmic transmission behavior.

It can be provided that the resonant frequency is only determined on one of the sides and is then transmitted to the opposite side, for example via a radio link. However, it can also be provided that the resonant frequency is determined separately on both sides.

If the converters are designed as bidirectional converters, the resonant converter can also be operated bidirectionally. This enables energy to be transmitted in both directions, so that the vehicle can be charged and electrical energy stored in a vehicle battery can be used to stabilize or feed the supply network.

The control devices can each be designed individually or combined as a combination of hardware and software, for example as program code that is executed on a microcontroller or microprocessor. It However, it can also be provided that parts are designed individually or combined as an application-specific integrated circuit (ASIC) or field-programmable gate array (FPGA).

The vehicle is in particular a motor vehicle, in particular an electric vehicle or hybrid vehicle. In principle, however, the vehicle can also be another land, water, air or space vehicle, for example an air taxi or a drone.

In one embodiment it is provided that, in order to determine the resonant frequency, at least one vehicle-side intermediate circuit voltage, one vehicle-side converter current, one mains-side intermediate circuit voltage and one mains-side converter current are oversampled, with the variables recorded being transmitted via a wireless communication link at least in one direction between the vehicle and the supply network or . In addition, an intermediate circuit current of a vehicle-side intermediate circuit, a voltage at half-bridges of the vehicle-side converter, a voltage at the vehicle-side coil, an intermediate circuit current of a mains-side intermediate circuit, a voltage at half-bridges of the mains-side converter and/or a voltage at the mains-side coil can be oversampled and detected be evaluated. Alternatively, these values can also be estimated based on an activation of the converter. In particular, the wireless communication link enables the recorded variables to be exchanged in real time. The wireless communication link can be, for example, a wireless communication link formed directly between the vehicle and the inductive charging device, for example via communication interfaces of the vehicle and the inductive charging device that are set up accordingly for this purpose. In principle, however, the wireless communication connection can also be indirect, for example via a fast mobile network (e.g. 5G), which enables real-time transmission with short latency times. The detected variables are provided in particular by means of time stamps on a time base that is synchronized between the vehicle and the inductive charging device.

In this case, it is provided in particular that the oversampled variables are evaluated by means of a field-programmable gate array. A field-programmable gate array enables high-frequency signal acquisition and signal processing. In this case, high-frequency is intended to mean in particular that an associated frequency range is above a modulation frequency of a pulse duration modulation of the converter. In particular, high frequency refers to a frequency that is higher by a factor of 5, preferably by a factor of 10, particularly preferably by a factor of 50, compared to the modulation frequency. If a modulation frequency is 20 kHz, for example, then a frequency of the signal detection and signal processing of the field-programmable gate array is 1 MHz, for example. Due to the parallel signal processing of a field-programmable gate array, this can advantageously process high-frequency (~MHz) sampled quantities. Due to the high-frequency sampling, sampling or aliasing effects can be reduced as disturbances in the signal. Any noise components of the sensors can be digitally filtered in the field-programmable gate array, so that a very high signal-to-noise ratio can be provided for further digital processing. In comparison, a microcontroller (e.g. DSP) is significantly less suitable for processing high-frequency signals, since the recorded values of the DSP have to be transported and processed by the internal analog-to-digital converter (ADC) to the processor core, which leads to propagation delay-related and preprocessing-related delays in evaluation. Instead, with a field-programmable gate array, the sensed values of the ADC are available to the logic units immediately, that is, in real time. Inexpensive ADCs that can generate a high-frequency digital data stream (bit stream), e.g. delta-sigma converters, can also be evaluated with field-programmable gate arrays without further measures. In particular, the field-programmable gate array is part of a system-on-chip (SoC).

In one embodiment it is provided that dead time effects occurring in the converters due to switching delay times are compensated for by dead time compensation. This is done in particular by means of the respective control device, in particular by means of at least one field-programmable gate field of the respective control device. Dead time compensation attempts to compensate for a dead time effect. The dead time effect occurs because there is a mapping error between an estimated current voltage and a real voltage due to the switching times of power semiconductors in a converter. To compensate for the dead time effect, switching edges of power semiconductors are adjusted, that is, they are shifted with regard to a switching time. The dead-time compensation is performed, for example, using the method described in B. Weber, T. Brandt and A. Mertens, Compensation of switching dead-time effects in voltage-fed PWM inverters using FPGA-based current oversampling, 2016 IEEE Applied Power Electronics Conference and Exposition (APEC) , Long Beach, CA, USA, 2016, pp. 3172-3179, doi: 10.1109/APEC.2016.7468318.

One embodiment provides that a leakage inductance of the resonant converter is estimated on the basis of the oversampled variables, with the resonance frequency being determined on the basis of the estimated leakage inductance. Using the estimated value for the leakage inductance, the resonant frequency can be calculated when the resulting capacitance is known, since the resonant frequency occurs both in the inductive part of the overall impedance of the resonant converter and in the capacitive part. In order to achieve an ohmic transmission behavior, the inductive part and the capacitive part must be exactly the same size so that they compensate each other to zero. Knowing the leakage inductance, the resonant frequency can be easily calculated since the capacitive component can be calculated from the known values of the tuning capacitors.

A further embodiment provides that a vehicle-side temperature and a network-side temperature of the resonant converter are detected using temperature sensors, with a series resistance of the resonant converter being estimated based on the detected temperatures and taken into account when estimating the leakage inductance. This makes it possible to better take into account a temperature behavior of the resulting series resistance of the resonant converter. The basis for estimating the series resistance can be, for example, an empirically determined characteristic curve or an empirically determined model which links a temperature to a series resistance. Alternatively, an observer can be used to estimate the resulting series resistance. An observer is in particular a control engineering observer (state observer) who estimates a state of the resonance converter based on a model of the resonance converter. The estimated state of the resonance converter is compared with an actual state of the resonance converter, and if there are discrepancies, at least one parameter of the model is adjusted until the estimated state and the actual state match again.

In one embodiment it is provided that the vehicle is moved automatically in order to change the arrangement of the coils in relation to one another in such a way that the leakage inductance is minimized or is minimized. As a result, a magnetic coupling between the coil on the vehicle side and the coil on the mains side can be optimized until the leakage inductance is minimized. By improving the magnetic coupling, an inductive energy transmission, in particular with regard to efficiency, can be further improved. In particular, it can be provided that a control and/or regulation of the vehicle for automated driving receives the estimated leakage inductance as an input parameter and, for example, evaluates a location-dependent change in the estimated leakage inductance in order to specifically minimize the leakage inductance by changing the vehicle position.

In one embodiment it is provided that the resonant converter is excited by at least one test pulse before starting the inductive energy transmission, the resonant frequency being determined on the basis of an oscillation caused by the at least one test pulse. In particular, at least one electrical variable, for example a vehicle-side converter current, a network-side converter current, a voltage at the vehicle-side coil and/or a voltage at the network-side coil, is oversampled and recorded in a time-resolved manner. After the end of the excitation, the resonant frequency can then be determined from an oscillation decaying over time, for example by determining the time of zero crossings and determining a frequency of the oscillation from this. The frequency is then an estimate of the resonant frequency of the resonant converter and is used, at least initially, to operate the resonant converter. Alternatively or additionally, the resonant frequency can also be determined from the excited vibration by means of a Fourier transformation (e.g. FFT) and a frequency analysis.

Additional features relating to the configuration of the vehicle, the inductive charging device and the system result from the description of configurations of the method. The advantages of the vehicle, the inductive charging device and the system are the same as in the case of the configurations of the method.

• 1 eine schematische Darstellung einer Ausführungsform des Systems zur induktiven Energieübertragung zwischen einem Fahrzeug und einem Versorgungsnetz;
• 2 eine schematische Darstellung eines elektrischen Schaltbildes zur Verdeutlichung der Erfindung;
• 3 ein schematisches Ersatzschaltbild des Resonanzwandlers;
• 4 ein schematisches Ersatzschaltbild des Resonanzwandlers mit zusammengefassten Größen;
• 5 eine schematische Darstellung einer Ausgangsspannung des Resonanzwandlers im Verhältnis zur Eingangsspannung des Resonanzwandlers für drei verschiedene Lastwiderstände über der (Betriebs-)Frequenz;
• 6 eine weitere Ausführungsform des Systems zur induktiven Energieübertragung zwischen einem Fahrzeug und einem Versorgungsnetz;
• 7 eine schematische Darstellung zur Verdeutlichung der Überabtastung;
• 8 ein schematisches Ablaufdiagramm einer Ausführungsform des Verfahrens zur induktiven Energieübertragung zwischen einem Fahrzeug und einem Versorgungsnetz.

The invention is explained in more detail below on the basis of preferred exemplary embodiments with reference to the figures. Here show:

• 1 a schematic representation of an embodiment of the system for inductive energy transmission between a vehicle and a supply network;
• 2 a schematic representation of an electrical circuit diagram to illustrate the invention;
• 3 a schematic equivalent circuit diagram of the resonant converter;
• 4 a schematic equivalent circuit diagram of the resonant converter with summarized variables;
• 5 a schematic representation of an output voltage of the resonant converter in relation to the input voltage of the resonant converter for three different load resistances over the (operating) frequency;
• 6 a further embodiment of the system for inductive energy transmission between a vehicle and a supply network;
• 7 a schematic representation to clarify the oversampling;
• 8th a schematic flowchart of an embodiment of the method for inductive energy transmission between a vehicle and a supply network.

In 1 a schematic representation of an embodiment of the system 1 for inductive energy transmission between a vehicle 50 and a supply network 60 is shown. The system 1 includes a vehicle 50 and an inductive charging device 20. The method for inductive energy transmission between the vehicle 50 and the supply network 60 is explained below with reference to the system 1.

The vehicle 50 includes a vehicle-side converter 2, a vehicle-side coil 3 and a control device 4. The vehicle-side converter 2 is designed as a rectifier and is used to convert an AC voltage into a DC voltage. The DC voltage is used to feed a DC voltage converter 5 which charges a traction battery 51 of the vehicle 50 . The vehicle-side coil 3 is electrically connected to the vehicle-side converter 2 . The vehicle-side converter 2 and the DC-DC converter 5 are together part of power electronics 52 of the vehicle 50.

The induction charging device 20 includes a line-side converter 21, a line-side coil 22 and a control device 23. The line-side converter 21 is designed as an inverter and is used to convert a DC voltage into an AC voltage. The line-side coil 22 is electrically connected to the line-side converter 21 . A rectifier 24 is connected between a three-phase supply voltage and the line-side converter 21 and rectifies the three-phase line voltage. The line-side converter 21 and the rectifier 24 are part of power electronics 25 of the induction charging device 20.

The vehicle-side coil 3 is arranged on an underside of the vehicle 50, for example. The mains-side coil 22 is arranged, for example, in a subsurface below the vehicle 50, for example below a parking area of a parking lot. In a parking position, the vehicle 50 is parked on the parking area in such a way that the vehicle-side coil 3 and the grid-side coil 22 are arranged next to one another. However, this can lead to an offset 70, which means that a magnetic coupling between the coils 3, 22 is only incomplete.

The coils 3, 22 together form a transformer 11. In this arrangement, the line-side converter 21, the line-side coil 22, the vehicle-side coil 3 and the vehicle-side converter 2 together form a resonant converter.

The control device 4 of the vehicle 50 and/or the control device 23 of the inductive charging device 20 are set up to determine or obtain a resonant frequency of the resonant converter configured in this way and to control the line-side converter 21 and/or the vehicle-side converter 2 in such a way that the resonant converter during the inductive energy transfer is operated with the specific resonant frequency.

In the 2 a schematic representation of an electrical circuit diagram is shown to illustrate the invention. The same reference symbols denote the same terms and features as in FIG 1 . The line-side converter 21 , the line-side coil 22 , the vehicle-side coil 3 and the vehicle-side converter 2 together form a resonant converter 10 . Located between the rectifier 24 and the line-side converter 21 is an intermediate circuit capacitance C _{ZK1 across} which a voltage u _ZK1 drops. Between the vehicle-side converter 2 and the DC-DC converter 5 there is an intermediate circuit capacitance C _{ZK2 across} which a voltage u _ZK2 drops. The resonant converter 10 includes a tuning capacitor C _r1 on the grid side and a tuning capacitor C _r2 on the vehicle side. In particular, the values of these tuning capacitors C _r1 , C _r2 are fixed and known. In particular, the respective values are selected in such a way that tuning of the resonance converter 10 or resonance operation at the frequencies used to operate the system 1 is possible.

In 3 a schematic equivalent circuit diagram of the resonant converter 10 is shown, the control devices not being shown. The same reference numerals denote the same terms and features as in the preceding 1 and 2 . In the following explanations, it is assumed that energy is to be transmitted from the supply network to the vehicle. But basically there is also one Energy transfer possible in the opposite direction.

The line-side converter 21 and the vehicle-side converter 2 each have two half-bridges, each with two semiconductor switches T _x with diodes D _x connected in antiparallel. The full bridge formed as a result on the network side is controlled in push-pull mode and is used for the alternating direction. The full bridge formed on the vehicle side is also controlled in push-pull and is used for rectification.

Streuflüsse bzw. Streuinduktivitäten werden durch L_1σ und $L_{2\sigma }^{\text{'}}$

modelliert. Der ideale Übertrager 12 realisiert eine Impedanztransformation, sodass die Größen $R_2^{\text{'}},L_{2\sigma }^{\text{'}}$

der Primärseite zugeordnet werden können, aber mit dem Quadrat des Windungszahlenverhältnisses $$\ddot{\text{u}}=\frac{n_1}{n_2}$$

transformiert sind. Eine Hauptinduktivität L_1h ist deutlich größer als die Streuinduktivitäten L_1σ und $L_{2\sigma }^{\text{'}}$

und spielt bei der Energieübertragung praktisch keine Rolle, da sich der Transformator 11 stets über den ausgangsseitigen Gleichrichter, der durch den fahrzeugseitigen Wandler 2 gebildet ist, entlastet und somit der primärseitige Stromfluss vom Stromfluss in der fahrzeugseitigen (Sekundär-)Spule 3 kompensiert wird. Wird das Ersatzschaltbild 11e für den Transformator 11 eingefügt und werden die Größen zu resultierenden Größen zusammengefasst, ergibt sich das Schaltbild gemäß 4. Die resultierenden Ersatzschaltbildelemente sind C_res, L_σ,res und R_res mit den jeweils daran abfallenden Spannungen u_Cres, u_Lσ,res und u_Rres.The transformer 11 formed by the coils 3, 22 over an air gap between the vehicle and the induction charging device with the magnetic coupling M and the inductances L ₁ and L ₂ can be modeled as a T equivalent circuit 11e. An ideal transformer 12 represents the turns ratio of the coil 22 on the primary side (n1) to the secondary side (n2). The ohmic transformer components are R ₁ and $R_2^{\text{'}}.$

Leakage fluxes or leakage inductances are determined by L _1σ and ${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">L</figure-callout>}}_{2\sigma }^{\text{'}}$

modeled. The ideal transformer 12 implements an impedance transformation so that the sizes $R_2^{\text{'}},{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">L</figure-callout>}}_{2\sigma }^{\text{'}}$

can be assigned to the primary side, but with the square of the turns ratio $$\ddot{\text{and}}=\frac{n_1}{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">n</figure-callout>}}_2}$$

are transformed. A main inductance L _1h is significantly larger than the leakage inductances L _1σ and ${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">L</figure-callout>}}_{2\sigma }^{\text{'}}$

and plays practically no role in energy transmission, since the transformer 11 is always relieved via the output-side rectifier, which is formed by the vehicle-side converter 2, and the primary-side current flow is thus compensated by the current flow in the vehicle-side (secondary) coil 3. If the equivalent circuit diagram 11e for the transformer 11 is inserted and the variables are combined to form the resulting variables, the circuit diagram according to FIG 4 . The resulting equivalent circuit picture elements are Cres , L _{σ,res and R res with} the voltages u _Cres , u _Lσ,res and u _{Rres dropping across them} .

The resulting total impedance is then: $$Z_{\mathrm{right}es}=R_{\mathrm{right}es}+j\omega L_{\sigma ,\mathrm{right}es}-\mathrm{<figure-callout\; id="1"\; label="j"\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{1}{\omega C_{\mathrm{right}es}}.$$

Depending on the relative offset 70 ( 1 ) of the vehicle to the inductive charging device or depending on the offset of the coils 3, 22 to one another, there is a different incomplete magnetic coupling of the coils 3, 22 and thus a different leakage inductance L _σ,res . The reactive components in the total impedance compensate each other for the resonant frequency and the transformer 11 shows an ohmic behavior.

In the 5 is a schematic representation of an output voltage u _out of the resonant converter in relation to the input voltage u _in of the resonant converter for three different load resistances R _l over the (operating) frequency ƒ. During transmission, there is a high level of sensitivity with regard to the selection of the control frequency f, which should be chosen as close as possible to the resonant frequency ƒ _r of the resulting series resonant circuit, as this maximizes the energy transfer to the vehicle.

the 6 shows a further embodiment of the system 1 for inductive energy transmission between a vehicle and a supply network. The same reference symbols denote the same features and terms as in the previous figures. In this embodiment it is provided that to determine the resonant frequency ƒ _r ( 5 ) at least one vehicle-side intermediate circuit voltage u _ZK1 , one vehicle-side converter current i ₁ , one mains-side intermediate circuit voltage u _ZK2 and one mains-side converter current i ₂ are oversampled, with the recorded variables being exchanged via a wireless communication link 15 at least in one direction between the vehicle and the supply network .

It can be provided that an intermediate circuit current i _ZK1 , a voltage u ₁₀ at half-bridges of the line-side converter 21, a voltage u ₁ at the line-side coil 22, an intermediate circuit current i _ZK2 of a vehicle-side intermediate circuit, a voltage u ₂₀ at half-bridges of the vehicle-side Converter 2 and/or a voltage u ₂ at the vehicle-side coil 3 are oversampled and evaluated.

Alternatively, these values can be estimated, in particular based on an activation of the converters 3, 21.

In this case, it is provided in particular that the oversampled variables are evaluated by means of a field-programmable gate array 30, 31. The field-programmable gate arrays 30, 31 enable high-frequency signal detection and signal processing on both sides. In this case, high-frequency means in particular that a sampling frequency is significantly higher (factor 5, 10, 100, etc.) than a modulation frequency of the converters 2, 21. The variables are digitized in particular by means of an analog/digital converter 32, 33 and the respective field-programmable gate array 30 , 31 fed directly.

The field-programmable gate arrays 30, 31 can in particular be part of a respective system-on-chip 34, 35 (SoC), in which the field-programmable gate arrays 30, 31 each have a digital signal processor 36, 37 (digital signal processor, DSP) on a chip are integrated, with a high data rate between the field-programmable gate arrays 30, 31 and the respective digital signal processors 36, 37 being achieved. The system-on-chips 34, 35 are in the control device 23 ( 1 ) of the inductive charging device 20 or in the control device 4 ( 1 ) of the vehicle 50 is formed. Due to their architecture, the field-programmable gate arrays 30, 31 can process large amounts of data simultaneously, ie in parallel, very efficiently and are therefore particularly suitable for signal evaluation of the variables detected at high frequency (oversampled) and converted at the analog/digital converters 32, 33. In contrast, in the system-on-chip architecture, the digital signal processor 36, 37 performs sequential tasks, for example management of state machines or external or chip-to-X communication. Furthermore, it can be provided that the digital signal processor 36, 37 can reprogram the respective field-programmable gate array 30, 31 at runtime, so that a signal evaluation in the field-programmable gate array 30, 31 can be adjusted.

The oversampling is shown schematically in 7 clarified. Modulation signals from power semiconductors of the half-bridges on the grid side are shown over time t and a resulting current ires, the voltage u _Lσ,res and the voltage u _C,res , each over time t. In the case of resonance (ie when operating at the resonance frequency), the voltage u _C,res compensates the voltage u _Lσ,res of the leakage inductance. In contrast to oversampling, standard sampling that is commonly used implements only a few measurements per activation or modulation period T _S , mostly in relation to the time centers of the modulation period, so that only the peaks and zero crossings of the resulting current ires are recorded (cf. 7 , period from 0 to T _S ). Oversampling, on the other hand, captures the course of i _res at a significantly higher frequency (cf. 7 , period from T _S to 2T _S ). In particular, it is recorded more frequently by a factor of 10 to 1000. The higher number of measured values can reduce measurement noise, so that zero crossings and a frequency can be better determined. In addition, due to the high-frequency sampling, there are no alias effects caused by harmonic components in the signal.

It can be provided that in the converters 2, 21 ( 6 ) Dead time effects occurring due to switching delay times can be compensated for by means of dead time compensation. The dead time compensation also takes place in particular by means of the system-on-chips 34, 35, these in particular having a modulation block 38, 39 ( 6 ) for driving the power semiconductors of the converters 2, 21, in each of which the dead time compensation is also implemented. The dead time compensation makes it possible in particular to estimate and provide the real voltages u ₁₀ , u ₂₀ at the outputs of the converters 2 , 21 in real time.

Furthermore, it can be provided that a leakage inductance of the resonant converter 10 ( 6 ) is estimated on the basis of the oversampled quantities, with the resonant frequency ƒ _r being determined on the basis of the estimated leakage inductance. This is explained below.

$$u_{20}=-R_{res2}\cdot i_2-\frac{1}{C_{r2}}{\displaystyle \int i_{2}dt+L_2\frac{d}{dt}{i}_2+\ddot{\text{u}}\cdot M\frac{d}{dt}{i}_1}$$

Due to the topology of the resonant converter 10 ( 4 and 6 ) the following equations can be used for modelling: $${\mathrm{and}}_{10}=R_{\mathrm{right}es1}\cdot {\mathrm{<figure-callout\; id="1"\; label="i"\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">i</figure-callout>}}_1+\frac{1}{C_{\mathrm{right}1}}{\displaystyle \int {\mathrm{<figure-callout\; id="1"\; label="i"\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">i</figure-callout>}}_1\mathrm{i.e}t+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">L</figure-callout>}}_1\frac{\mathrm{i.e}}{\mathrm{i.e}t}{i}_1-\ddot{\text{and}}\cdot M\frac{\mathrm{i.e}}{\mathrm{i.e}\mathrm{<figure-callout\; id="2"\; label="t\; i"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}"><figure-callout\; id="20"\; label="t\; i"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0021.png"\; state="\{\{state\}\}">t</figure-callout></figure-callout>}}{i}_{}{}_{}{}_2}$$

$${\mathrm{and}}_{20}=-R_{\mathrm{<figure-callout\; id="2"\; label="right\; e\; s"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">right</figure-callout>}es2}\cdot i_2-\frac{1}{C_{\mathrm{right}2}}{\displaystyle \int {\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">i</figure-callout>}}_2\mathrm{i.e}t+{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">L</figure-callout>}}_2\frac{\mathrm{i.e}}{\mathrm{<figure-callout\; id="2"\; label="i.e\; t\; i"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">i.e</figure-callout>}t}{i}_{}{}_2+\ddot{\text{and}}\cdot M\frac{\mathrm{i.e}}{\mathrm{i.e}\mathrm{<figure-callout\; id="1"\; label="t\; i"\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">t</figure-callout>}}{i}_{}{}_1}$$

Here u ₁₀ , u ₂₀ are the dead-time compensated voltages of the converters 2, 21 or the half-bridges of the converters 2, 21, R _res the respective resulting series resistance, L ₁ the self-inductance of the coil 22 on the primary side (in the examples shown the mains side) and L ₂ the self-inductance of the coil 3 on the secondary side (the vehicle side in the examples shown) and M the magnetic coupling. The resulting series resistance R _res1 related to the primary side of the transformer is given as R _res1 = R ₁ +ü ² R ₂ . The value R _res2 also results analogously from the impedance transformation based on the ratio of the number of turns. The magnetic coupling M between the primary and secondary side results from geometric variables with regard to the spatial magnetic field distribution.

The quantities L ₁ , L ₂ and M are unknown. R _res can be tracked or identified as a function of temperature. For this purpose, for example, temperature sensors 6, 16 ( 6 ) are used in the respective power electronics on the mains side and on the vehicle side. R _res can then be estimated based on an empirically determined characteristic or by means of an observer.

und $\frac{d}{dt}{i}_2$

bestimmt werden.Due to the oversampling, the curves of i ₁ and i ₂ can be recorded precisely. With the help of, for example, a regression analysis and a spline interpolation, the temporal derivations of the currents $\frac{\mathrm{i.e}}{\mathrm{i.e}\mathrm{<figure-callout\; id="1"\; label="t\; i"\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">t</figure-callout>}}{i}_{}{}_1$

and $\frac{\mathrm{i.e}}{\mathrm{<figure-callout\; id="2"\; label="i.e\; t\; i"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">i.e</figure-callout>}t}{i}_{}{}_2$

to be determined.

The oversampling also enables a continuous time integral formation of the sampled variables, so that ∫i ₁ dt and ∫i ₂ dt are also known or can be determined.

Since the control devices 4, 23 on both sides require values from the other side, the recorded values are provided in particular with a time stamp on a synchronized time base and are transmitted via a fast communication link 15 ( 6 ) exchanged. The respective time bases are synchronized via the communication connection 15 at the start of the method, that is to say in particular immediately after the vehicle has been arranged on the inductive charging device.

If the variables between the inductive charging device on the grid side and the vehicle are exchanged, the required parameters L ₁ , L ₂ , M and R _res can be identified using observer-based approaches such as Luenberger observers, Kalman filters and gray box models with gradient descent methods. However, a least mean square estimator can also be used offline, for example.

$$L_{\sigma 2}=L_2-\frac{M}{\ddot{\text{u}}}$$

$$L_{\sigma ,res}=L_{\sigma 1}+{\ddot{\text{u}}}^2{L}_{\sigma 2}$$

The leakage inductances can be determined from the variables identified: $${\mathrm{<figure-callout\; id="1"\; label="L\; \sigma "\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">L</figure-callout>}}_{\sigma }={\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">L</figure-callout>}}_1-\ddot{\text{and}}M$$

$${\mathrm{<figure-callout\; id="2"\; label="L\; \sigma "\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">L</figure-callout>}}_{\sigma }={\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">L</figure-callout>}}_2-\frac{M}{\ddot{\text{and}}}$$

$$L_{\sigma ,\mathrm{right}es}={\mathrm{<figure-callout\; id="1"\; label="L\; \sigma "\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">L</figure-callout>}}_{\sigma }+{\ddot{\text{and}}}^2{\mathrm{<figure-callout\; id="2"\; label="L\; \sigma "\; filenames="DE102021205102A1\_0018.png,DE102021205102A1\_0019.png"\; state="\{\{state\}\}">L</figure-callout>}}_{\sigma }$$

und der resultierenden Kapazität C_res= C₁+ ü²C₂ kann die Resonanzfrequenz ${ƒ}_r=\frac{{\omega }_r}{2\pi }$

bestimmt werden, indem die Kreisfrequenz ω so gewählt wird, dass die letzten beiden Summanden einander kompensieren, dies ergibt: $${ƒ}_r=\frac{1}{2\pi \sqrt{L_{\sigma ,res}\cdot C_{res}}}$$

With the help of: $$Z_{\mathrm{right}es}=R_{\mathrm{right}es}+j\omega L_{\sigma ,\mathrm{right}es}-\mathrm{<figure-callout\; id="1"\; label="j"\; filenames="DE102021205102A1\_0018.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{1}{\omega C_{\mathrm{right}es}}$$

and the resulting capacitance C _res = C ₁ + ü ² C ₂ can be the resonant frequency ${ƒ}_{\mathrm{right}}=\frac{{\omega }_{\mathrm{right}}}{2\pi }$

can be determined by choosing the angular frequency ω in such a way that the last two summands compensate each other, this results in: $${ƒ}_{\mathrm{right}}=\frac{1}{2\pi \sqrt{L_{\sigma ,\mathrm{right}es}\cdot C_{\mathrm{right}es}}}$$

The converters 2, 21 are then operated on the vehicle side and/or on the network side with the specific resonant frequency ƒ _r in that the control devices 4, 23 activate the respective power semiconductors T _x accordingly.

The resonant frequency ƒ _r is in particular continuously determined and tracked, so that the resonance converter 10 is always operated at the resonant frequency ƒ _r .

Provision can be made for the resonance converter 10 to be excited by at least one test pulse before starting the inductive energy transmission, with the resonance frequency ƒ _r being determined on the basis of an oscillation caused by the at least one test pulse. For example, the resonant frequency ƒ _r can be determined by determining the zero crossings of the vibration caused. Provision can also be made for a Fourier transformation and a frequency analysis to be carried out to determine the resonant frequency fr.

In 8th a schematic flowchart of an embodiment of the method for inductive energy transmission between a vehicle and a supply network is shown. The method is carried out using a system made up of a vehicle and an inductive charging device.

In a measure 100, a coil on the vehicle side is arranged on a coil on the mains side arranged outside the vehicle, for example by driving the vehicle manually or automatically into a charging position in a charging parking space.

In a measure 101, a resonant frequency of a resonant converter formed by the coils arranged one on top of the other, a vehicle-side converter connected to the vehicle-side coil and a line-side converter connected to the line-side coil is determined.

In a measure 102, the converters on the vehicle side and/or on the network side are controlled in such a way that the resonant converter is operated at the specific resonant frequency during the inductive energy transmission.

As part of measure 101, a measure 101a can provide for the resonant converter to be excited by at least one test pulse before starting the inductive energy transmission, with the resonant frequency being determined on the basis of an oscillation caused by the at least one test pulse.

As part of measure 101, a measure 101b can be provided as an alternative or in addition In order to determine the resonant frequency, at least one vehicle-side intermediate circuit voltage, one vehicle-side converter current, one line-side intermediate circuit voltage and one line-side converter current are recorded in an oversampled manner to determine the resonant frequency, with the variables recorded being exchanged via a wireless communication link at least in one direction between the vehicle and the supply network.

Provision can also be made for dead time effects occurring in the converters due to switching delay times to be compensated for by dead time compensation.

Measure 101b provides for a leakage inductance of the resonant converter to be estimated on the basis of the oversampled variables, with the resonance frequency being determined on the basis of the estimated leakage inductance.

For this purpose, measure 101b can also provide for a vehicle-side temperature and a mains-side temperature of the resonant converter to be detected using temperature sensors, with a series resistance of the resonant converter being estimated from the detected temperatures and taken into account when estimating the leakage inductance.

A measure 103 can provide for the vehicle to be moved automatically in order to change the arrangement of the coils relative to one another in such a way that the leakage inductance is minimized or is minimized. To this end, measures 101b and 103 are repeated until the leakage inductance is minimized. Provision can also be made here for the leakage inductance to be determined for a number of positions of the vehicle in order to determine a minimum in a position-dependent profile of the values. The vehicle is then driven to the minimum position.

reference list

1

system

2

on-board converter

3

vehicle coil

4

control device

5

DC converter

6

temperature sensor

10

resonant converter

11

transformer

11e

(T) equivalent circuit diagram

12

ideal transmitter

15

communication link

16

temperature sensor

20

inductive charging device

21

line-side converter

22

mains-side coil

23

control device

24

rectifier

25

Power electronics (inductive charging device)

30

field-programmable gate array

31

field-programmable gate array

32

Analog/digital converter

33

Analog/digital converter

34

System on Chip (SoC)

35

System on Chip (SoC)

36

Digital signal processor

37

Digital signal processor

38

modulation block

39

modulation block

50

vehicle

51

traction battery

52

power electronics (vehicle)

60

supply network

70

offset

100-103

Measures of the procedure

Cr1

tuning capacitor

Cr2

tuning capacitor

CZK1

intermediate circuit capacity

CZK2

intermediate circuit capacity

Cres

resulting capacity (equivalent circuit)

ƒ

frequency

ƒr

resonant frequency

i1

mains-side converter current

i2

vehicle-side converter current

ires

resulting stream

iZK1

intermediate circuit current

iZK2

intermediate circuit current

L1

inductance

L2

inductance

L1σ

Leakage inductance (primary side)

Leakage inductance (secondary side, transformed)

Lσ,res

resulting leakage inductance (equivalent circuit diagram)

L1h

main inductance

M

magnetic coupling

R1

ohmic resistance (primary side)

R2

ohmic resistance (secondary side, transformed)

Res

resulting ohmic resistance (equivalent circuit diagram)

RL

load resistance

TS

modulation period

u1

Voltage (mains coil)

u2

Voltage (vehicle coil)

u10

Voltage (half-bridge line-side converter)

u20

Voltage (half-bridge on-board converter)

UZK1

tension

uZK2

tension

uC, res

voltage (resultant capacity)

uLσ,res

Voltage (resultant leakage inductance)

uRres

voltage (resulting ohmic resistance)

uin

Input voltage of the resonant converter

out,

Output voltage of the resonant converter

u

turns ratio

Zres

total impedance

ω

angular frequency

Claims (10)

Method for inductive energy transmission between a vehicle (50) and a supply network (60), wherein a vehicle-side coil (3) is arranged on a network-side coil (22) outside the vehicle (50), with a resonant frequency (ƒ _r ) of a the coils (3, 22) arranged one on top of the other, a vehicle-side converter (2) connected to the vehicle-side coil (3) and a line-side converter (21) connected to the line-side coil (22), and wherein the Converter (2,21) are controlled on the vehicle side and/or the network side in such a way that the resonant converter (10) is operated at the specific resonant frequency (ƒ _r ) during the inductive energy transmission. procedure after claim 1 , characterized in that to determine the resonant frequency (ƒ _r ) at least one vehicle-side intermediate circuit voltage (u _ZK2 ), one vehicle-side converter current (u ₂₀ ), one mains-side intermediate circuit voltage (u _ZK1 ) and one mains-side converter current (u ₁₀ ) are oversampled, wherein the detected variables are exchanged at least in one direction between the vehicle (50) and the supply network via a wireless communication link (15). Method according to one of the preceding claims, characterized in that dead-time effects occurring in the converters (2, 21) due to switching delay times are compensated for by means of dead-time compensation. Procedure according to one of claims 2 or 3 , characterized in that a leakage inductance (L _σ,res ) of the resonance converter (10) is estimated based on the oversampled detected variables, the resonance frequency (ƒ _r ) based on the estimated leakage inductance (L _σ,res ) being determined. procedure after claim 4 , characterized in that a vehicle-side temperature and a network-side temperature of the resonant converter (10) are detected by means of temperature sensors (6,16), a series resistance (R _res ) of the resonant converter (10) being estimated on the basis of the detected temperatures and when estimating the leakage inductance (L _σ,res ) is taken into account. procedure after claim 4 or 5 , characterized in that the vehicle (50) is moved automatically in order to change an arrangement of the coils (3,22) relative to one another in such a way that the leakage inductance (L _{σ, res} ) is minimized or is minimized. Method according to one of the preceding claims, characterized in that the resonance converter (10) is excited by at least one test pulse before starting the inductive energy transmission, the resonance frequency (ƒ _r ) being determined on the basis of an oscillation caused by the at least one test pulse. Vehicle (50), comprising: an on-board converter (2) set up for converting at least one AC voltage into a DC voltage, an on-board coil (3) which is electrically connected to the on-board converter (2) and which is set up and arranged for this purpose that the coil (3) on the vehicle side can be arranged on a mains-side coil (22) arranged outside the vehicle (50) to form a resonant converter (10), and a control device (4), the control device (4) being set up for this purpose, to determine or obtain a resonant frequency (ƒ _r ) of a resonant converter (10) designed in this way and to control the converter (2) in such a way that the resonant converter (10) is operated at the determined resonant frequency (ƒ _r ) during the inductive energy transmission. Induction charging device (20) for a supply network (60), comprising: a network-side converter (21), set up for converting at least one DC voltage into an AC voltage, a network-side coil (22) which is electrically connected to the network-side converter (21) and which is set up and arranged in such a way that the mains-side coil (22) can be arranged on a vehicle-side coil (3) arranged in or on a vehicle (50) to form a resonance converter (10), and a control device (23), wherein the Control device (23) is set up to determine or obtain a resonant frequency (ƒ _r ) of a resonant converter (10) designed in this way and to control the line-side converter (21) in such a way that the resonant converter (10) has the determined resonant frequency during the inductive energy transmission (ƒ _r ) is operated. System (1) for inductive energy transmission between a vehicle (50) and a supply network (60), comprising a vehicle (50). claim 8 and an inductive charging device (20). claim 9 .

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