WO2019013626A1

WO2019013626A1 - Electrically driven vehicle, an inductive vehicle charging system and a method for wireless inductive charging

Info

Publication number: WO2019013626A1
Application number: PCT/NL2018/050465
Authority: WO
Inventors: Venugopal PRASANTH; Soumya BANDYOPADHYAY; Pavol Bauer
Original assignee: Technische Universiteit Delft
Priority date: 2017-07-12
Filing date: 2018-07-11
Publication date: 2019-01-17

Abstract

The invention relates to an electrically driven vehicle provided with a wireless inductive charging system. The system comprises at least a first and a second wireless transmitter. The vehicle is provided with a wireless receiver. The receiver is provided with a secondary coil for receiving a wireless charging signal from the primary coils of transmitters, and with a resonant circuitry connected to the secondary coil, wherein the resonant circuitry is a multi resonant network. During operation of the wireless inductive charging system, a first wireless transmitter is tuned to a first resonance frequency of the multi resonant network, while a second wireless transmitter is tuned to a second resonance frequency of the multi resonant network.

Description

Electrically driven vehicle, an inductive vehicle charging system and a method for wireless inductive charging

The invention relates to a vehicle provided with a wireless inductive charging system.

KR 10-2006-0076796 discloses such a vehicle provided with a wireless inductive charging system, wherein a first resonant circuit is provided on the primary side of a transformer, and a second resonance circuit is provided on the secondary side of the transformer. The entire electrical circuit is embodied in the vehicle, and the document is silent on how to transfer external energy into the vehicle inductive charging system.

It is an object of the invention to provide a vehicle with a wireless inductive charging system which can receive energy from outside of the vehicle to use for charging the vehicle charging system.

It is a further object of the invention to provide a vehicle that is capable to receive wireless inductive power transfer wherein the problem of interference of mutually coupled coils is counteracted.

Therefore, according to the invention, an electrically driven vehicle is proposed that is provided with a wireless receiver for an inductive charging system, comprising:

- a secondary coil for receiving a wireless charging signal from a primary coil of a transmitter, and

- a resonant circuitry connected to the secondary coil, and which is characterized in that the resonant circuitry connected to the secondary coil is a multi-resonant network.

By providing the vehicle with a wireless receiver with a resonant circuitry that is a multi resonant network, the receiver is enabled for being charged by a first wireless charging signal at a first resonance frequency as well as by a second wireless charging signal at a second resonance frequency. When transferring inductive power via multiple frequencies the advantage of transferring power over the same medium, an air gap, is obtained via two different frequencies in an independent way, such that one frequency system does not interact with the other. Then, a transmitter or receiver with multiple coils can be decoupled by virtue of the fact that they are carrying currents of a different frequency.

Typically the vehicle inductive charging system may include multiple transmitters tuned to different frequencies, while a single receiver, also called pickup, may be arranged in the vehicle to receive all of them exploiting the multi resonant network.

The multiple transmitters can advantageously be positioned along a linear line or another geometry for the purpose of charging electrically driven vehicles in a charging lane.

The invention also relates to a method.

By way of example only, embodiments of the present invention will now be described with reference to the accompanying figures in which

Fig. 1 shows a circuitry of a wireless inductive charging system;

Fig. 2 shows a vehicle's circuitry of a wireless receiver according to the invention;

Fig. 3 shows a schematic perspective view of an inductive vehicle charging system according to the invention;

Fig. 4 shows a diagram of a single series resonance structure;

Fig. 5 shows a diagram of a dual capacitor resonance structure; Fig. 6 shows an impedance characteristic simulation of the resonance circuit of Fig. 4 and Fig. 5;

Fig. 7 shows an impedance characteristic simulation of the resonance circuit in the wireless receiver circuitry of Fig. 2;

Fig. 8 shows a flow chart of an embodiment of a method according to the invention.

It is noted that the figures merely show preferred embodiments according to the invention. In the figures, the same reference numbers refer to equal or corresponding parts. Figure 1 shows a circuitry of a wireless inductive charging system 1 including a single wireless transmitter 2 and a single wireless receiver 3. The system 1 comprises a DC power source 10, e.g. a 750 V PV panel, and a DC/AC inverter 12 being fed by the DC power source 10 and generating an AC charging signal.

The system 1 includes a resonant inductive power transfer system that can e.g. be implemented as a serial-serial SS, serial-parallel SP, parallel-serial PS, parallel-parallel PP or LCL circuitry.

In the shown embodiment, the DC/AC inverter is implemented as a DC/AC phase shift inverter e.g. a PWM inverter having a multiple number of boost Mosfets 12a-d that are arranged in parallel with reversely oriented diodes 12e-h and connected in a full bridge structure for generating a high frequency AC charging signal. In principle, the frequency of the AC charging signal can be any arbitrary value. As an example, the AC charging signal frequency can be in a range from circa 70 kHz or lower to circa 100 kHz or higher. In practice, the AC charging signal frequency can be circa 85 kHz so that the signal can be touted for wireless electric vehicle charging. The Mosfets 12 a-d may include SiC Mosfets or other suitable Mosfet switches. The diodes 12e-h can e.g. be implemented as SiC Schottky diodes or other suitable diodes. The inverter can also be operated as a single Active Bridge for voltage cancellation.

For the purpose of providing DC power to the DC/AC inverter 12, the system 1 is further provided with a transient absorber circuitry 14, in the shown embodiment including a St. St. Mosfet 14a and a transient absorber resistor 14b arranged in parallel. However, also other transient absorber circuitry would be applicable. Further, the system 1 includes a DC/DC Boost converter 16 having a Boost inductor 16a, Boost Mosfet 16b, diode 16c and Boost Capacitor 16d. The transient absorber circuitry 14 and the DC/DC Boost converter 16 are located between the DC power source 10 and the DC/AC inverter 12. In principle, the system 1 can be provided without transient absorber circuitry 14 and/or without DC/DC Boost converter 16. Further, the system 1 can be fed from an AC-grid rectified by a DC/DC converter PFC.

Further, the system 1 includes a primary coil L_p that is fed by the AC charging signal. During operation of the system 1, the primary coil L_p transmits a wireless charging signal to a secondary coil L_s of a device 20 to be charged. Both the primary coil L_p and the secondary coil L_s can be arranged in series with a primary and secondary capacitor C_p, C_s, forming a resonant SS transmitting and receiving circuitry, respectively. However, also other transmitting circuitries and/or or receiving circuitries can be applied. In operation, the transmitting circuitry and the receiving circuitry may form a so-called equivalent resonant transformer SS topology, also known as air core resonant transformer SS topology, including the primary coil Lp, the secondary coil L_s, a mutual inductance coil L_m, the primary capacitor C_p, and the secondary capacitor C_s. Here, a so-called environment series resonance is formed by L_p-L_m and C_p in series, while a so-called pickup series resonance is formed by L_s-L_m and C_s in series. The mutual inductance coil L_m represents an air core mutual inductance. In the circuitry shown in Fig. 1, the device to be charged 20 is provided with an AC/DC full bridge rectifier 22 including four diodes 22a-d connected in a bridge structure, and a rechargeable electrical energy storage system implemented as a capacitor 22e arranged in parallel. Further, the device to be charged 20 is electrically represented by a load resistor 24.

Generally, a transformer topology applied for stepping down the voltage of the AC charging signal can be applied so that a relatively high voltage and, therefore, a relatively low current can be applied in the DC/AC inverter 12. However, in principle, the system can also be applied with a step -up transformer or without stepping down/up functionality.

Figure 2 shows a circuitry of a wireless receiver 3 of a vehicle according to the invention. The receiver 3 includes a secondary coil L for receiving a wireless charging signal from a primary coil of a transmitter, in the circuitry represented by a voltage source Vi_n delivering a current I. The receiver 3 also includes a resonant circuitry 4 connected in series with the secondary coil L. The resonant circuitry 4 has a so-called multi-resonant tank including a parallel combination of a series resonant circuit and a multi-resonant switch topology that is described in further detail below. Further, the receiver 3 includes a load resistivity RL. Here, the resonant circuitry 4 is a multi resonant network having two different resonance frequencies.

Generally, at a resonance frequency, the impedance characteristic of a resonance circuitry has a local or global minimum so that losses are minimized. It is noted that, in principle, the multi resonant network may have more than two different resonance frequencies, e.g. three, four or five different resonance frequencies.

By providing at least two different resonance frequencies, the multi resonant network is enabled to be charged by charging signals at different frequencies. As an example, the multi resonant network can be charged by a first charging signal transmitted by a first transmitter coil having a first resonance frequency, as well as by a second charging signal transmitted by a second transmitter coil having a second resonance frequency, different from the first resonance frequency.

Then, a single wireless receiver can be charged by multiple transmitter coils operating at different resonance frequencies, either simultaneously or consecutively.

The wireless receiver 3 also includes a rectifier 22 for rectifying received AC signals and a rechargeable electrical energy storage system for storing the received electrical energy, as shown in Fig. 1.

The wireless receiver 3 forms a wireless power application for an electrically driven vehicle and is located in the vehicle. Figure 3 shows a schematic perspective view of an inductive charging system 1 according to the invention. The system 1 includes a wireless receiver 3 as described referring to Fig. 2 above, located in an electrically driven vehicle 5, such as in the base or chassis of the vehicle. Further, the system 1 includes a first transmitter 2a and a second wireless transmitter 2b, each provided with a primary coil, also called pad 6a, 6b, connected to a respective compensation capacitor bank. The first

transmitter 2a is tuned to a first resonance frequency of the multi resonant network of the wireless receiver 2, while the second resonance transmitter 2b is tuned to a second resonance frequency, different from the first resonance frequency.

In the shown embodiment, the inductive charging system 1 includes a further first transmitter 2a' that is also tuned to the first resonance frequency of the multi resonant network. The second transmitter 2b is arranged between the first transmitter 2a and the further first transmitter 2a', forming a line segment LS. Generally, the inductive charging system 1 may include a multiple number of similar first and second transmitters located in an array such that first and second wireless transmitters are arranged in an alternating order, i.e. such that neighboring wireless transmitters are operative on differing frequencies. Then, mutual interference of transmitters resonating at the same or similar resonance frequency can be minimized. As an example, the array is one-dimensional forming a linear structure with alternating first and second transmitters, e.g. along a straight or curved line path. As a further example, the array is two-dimensional with alternating first and second transmitters, e.g. like a checkerboard pattern.

In the embodiment shown in Fig. 3, the inductive charging system 1 is located below a ground level 6 of a charging lane for wirelessly charging electrically driven vehicles 5. Then, a series of transmitter coils or pads 2a, 2a'_f 2b are arranged along the linear line segment LS in a roadway lane. In principle, subsequent transmitters 2 can be tuned to two different resonance frequencies, in alternating order as indicated above. Alternatively, the transmitters can be tuned to more than two resonance frequencies. As an example, each transmitter has its own resonance frequency different from the resonance frequency of other transmitters, e.g. a first transmitter is tuned to 80 kHz, a second transmitter is tuned to 90 kHz, a third

transmitter is tuned to 80 kHz and a fourth transmitter is tuned to 90 kHz. Then, preferably, the wireless receiver, also called multi-frequency single pickup, has a resonant circuitry that resonates at all tuned resonance frequencies of the transmitters of the system. Further, at least two transmitters may have a same or similar resonance frequency, preferably transmitters that are located at relatively great distance from each other, to counteract mutual interaction and circulating power among each other.

Generally, a network attains series resonance when its overall impedance is the lowest for a certain operating frequency. That is, in a series resonant network, the current flowing through the circuit is maximum at resonant frequency.

Figure 4 shows a diagram of a single series resonance structure. The left-hand side of Fig. 4 shows a circuit 30 of the single series resonance structure or network S fed by a voltage source Vs, while the right-hand side of Fig. 4 shows the spectral impedance 31 of said circuit 30 as well as an electrical current 32 flowing through said circuit 30. A typical single frequency series resonance circuit 30 or network has a resistor R, a capacitor C and an inductor L connected in series with each other as shown at the left-hand side of Fig. 4. By applying Thevenin's rule, one can derive the impedance equation for the network as follows:

At resonance, the network must have zero reactive power. That is, it has a purely resistive impedance. Such a condition is attained when the inductive and capacitive reactances have equal magnitudes with a phase shift of 180° from each other. It is noted that the series resonant tank behaves as a capacitance for sub-resonant (below resonance) frequencies and behaves inductively for super-resonant frequencies.

Figure 5 shows a diagram of a dual capacitor resonance structure, or dual-resonant switched network. Again, the left-hand side of Fig. 5 shows a circuit 40 or network D4 of the dual capacitor resonance structure, while the right-hand side of Fig. 5 shows the spectral impedance ZD4, 41 of said circuit 40. Here, the series resonance frequency is less than their parallel resonance frequency.

The network 40 has a series combination of inductor Ls and capacitor Cs that is in parallel with a capacitor Cp. The impedance equation of the network 40 is given by:

or

The values of Ls and Cs are picked such that, the network attains a series resonance when the operating frequency is equal to cos. Thus, one can derive the equation for «s by equating eqn 1.4 to zero. or

At ωρ > cas, the series combination of Ls and. Cs has an inductive reactance. Thus, the value of Cp can be chosen such that the network attains parallel resonance when the operating frequency is equal to ωρ . Therefore,

This is rewritten as:

From eqn 1.6, we have,

The resonant circuitry 4 shown in Fig. 2, also referred to as Topology III, is designed using networks S and D4 as basic building blocks . Networks S and D4 behave as capacitors at the frequencies ωι and &>2 respectively. The series combination of D4 and Ci is connected in parallel to series combination of S and C2. The inductance value of inductor L is equal to Li and L2. That is, the only capacitance value in the circuit is varied according to attain series resonance at ωι and Q2- That is, by defining equivalent capacitances of the network in series to L and naming them as Csi and Csz, the frequencies are

and

Network D4 is designed such that it attains series resonance (short circuit) at ωι and behaves as a capacitor at t02- Whereas, network S is designed such that it behaves as a capacitor at ωι and attains series resonance at C02. Therefore the values of Cxi and Cx2 are chosen such that the equivalent capacitances in the network are Csi and Cs2 at the respective operating frequencies. That is,

and

The following conditions may be kept in mind while designing this topology:

The value of

is calculated from the equation 1.12,

Figure 6 shows an impedance characteristic simulations of described resonance circuits. At the top of Fig. 6 a simulation of an impedance characteristic curve 50 of the single series resonance structure or network S shown in Fig. 4 is shown. Similarly, at the bottom of Fig. 6 a simulation of an impedance characteristic curve 51 of the dual-resonant switched network or network D4 shown in Fig. 5 is shown.

The network S attains series at 100 kHz and has a capacitive impedance at 85 kHz. On the other hand, network D4 attains series resonance at 85 kHz and parallel resonance at 92.7 kHz. Therefore, topology III attains series resonance at 85 kHz and 100 kHz.

Figure 7 shows an impedance characteristic simulation curve 52 of the resonance circuit in the wireless receiver circuitry of Fig. 2, also referred to as Topology III.

Figure 8 shows a flow chart of an embodiment of the method for charging a vehicle according to the invention. The method 100 is used for wireless inductive charging. The method 100 comprises the steps of providing 110 a charging lane for the vehicle with at least a first and a second wireless transmitter generating wireless charging signals, and a step of providing 120 into a vehicle a wireless receiver provided with a secondary coil receiving the first and second wireless charging signals, wherein the wireless receiver is provided with a resonant circuitry connected to the secondary coil, the resonant circuitry being a multi resonant network, and wherein the first and second wireless transmitter are tuned to respective resonance frequencies of the multi resonant network.

The invention is not restricted to the embodiments described above. It will be understood that many variants are possible.

In the exemplary embodiment shown in Fig. 2, the multi resonant network has two different resonance frequencies. However, in principle, the multi resonant network may have more than two different resonance frequencies, e.g. three, four or five different resonance frequencies. Further, in principle, any combination of parallel and/or series resonance sub- circuits, such as network S or network D4, can be applied in the multi resonant network of the wireless receiver, to obtain more than two resonance frequencies.

As an example, the DC power source may be implemented as a 750 V PV panel or as another PV panel. Further, the DC power source may be implemented by providing a rectified DC input from AC mains such as an AC grid with so-called power factor corrector PFC topology or by another DC power source.

These and other embodiments will be apparent for the person skilled in the art and are considered to fall within the scope of the invention as defined in the following claims. For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments. However, it will be appreciated that the scope of the invention may include embodiments having combinations of all or some of the features described.

Claims

1. Electrically driven vehicle provided with a wireless receiver for an inductive charging system, comprising:

- a resonant circuitry connected to the secondary coil,

characterized in that the resonant circuitry connected to the secondary coil is a multi-resonant network.

2. Electrically driven vehicle according to claim 1, wherein the resonant circuitry has at least two different resonance frequencies.

3. Electrically driven vehicle according to claim 1 or 2, further comprising a rectifier and a rechargeable electrical energy storage system.

4. An inductive vehicle charging system, comprising a vehicle provided with a wireless receiver according to any of the preceding claims, characterized in that the system comprises at least a first and a second wireless transmitter, wherein the first wireless transmitter is tuned to a first resonance frequency of the multi resonant network connected to the secondary coil in the vehicle and wherein the second wireless transmitter is tuned to a second resonance frequency of the multi resonant network connected to the secondary coil in the vehicle.

5. An inductive charging system according to claim 4, comprising a multiple number of wireless transmitters located in an array such that neighboring wireless transmitters are operative on differing frequencies. 7. A method for wireless inductive charging, characterized by the steps of:

- providing a charging lane with at least a first and a second wireless transmitter generating wireless charging signals at mutually different frequencies, - providing into a vehicle a wireless receiver provided with a secondary coil receiving the first and second wireless charging signals with different frequencies,

wherein the wireless receiver is provided with a resonant circuitry being embodied as a multi resonant network, and

wherein the first and second wireless transmitter are tuned to respective resonance frequencies of the multi resonant network.