Impedance adjustment circuit and power transmission / reception system using the same

Abstract

To reduce the number of components and installation cost by reducing the number of inverters provided in a power transmission / reception system.SOLUTION: An impedance adjustment circuit includes: a parallel circuit that includes a series circuit in which a capacitor Cp and switches S1, S2 are connected in series and in which an inductor L is connected in parallel with the series circuit; and a capacitor Cs connected in series with the parallel circuit. By opening / closing the switches S1, S2, impedance of the whole circuit can be controlled.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an impedance adjustment circuit and a power transmission and reception system using the same. [Background technology]

[0002] Contactless power transmission and reception systems using inductors have been disclosed (Non-Patent Documents 1 and 2). Fig. 18 shows a configuration example of a conventional power transmission and reception system 100. The power transmission and reception system 100 is placed under a road, and supplies power contactlessly to a vehicle 102 traveling on the road.

[0003] The power transmission and reception system 100 includes a DC power source 10, inverters 12 (12a to 12d), resonance coils 14 (14a to 14d), and primary coils 16 (16a to 16d). A secondary coil 18 is provided under the vehicle body facing the road in the vehicle 102. The inverters 12, resonance coils 14, and primary coils 16 are combined and connected to a DC power source 10. When supplying power, the inverter 12 connected to the primary coil 16 to be supplied is controlled to generate a magnetic field from the primary coil 16. When the vehicle 102 travels over the primary coil 16 generating a magnetic field, the magnetic field is magnetically coupled to the secondary coil 18, and power is supplied to the vehicle 102. The inverters 12 connected to the primary coils 16 to which power is not supplied are turned off to prevent the primary coils 16 from generating a magnetic field. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Kim, DH and Ahn, D., 2018. Self-tuning LCC inverter using PWM-controlled switched capacitor for inductive wireless power transfer. IEEE Transactions on Industrial Electronics, 66(5), pp.3983-3992. [Non-Patent Document 2] Matsumoto, R., Ji, B., Fujimoto, H. and Hori, Y., 2020, November. Resonance frequency adjustment using pwm-controlled variable capacitor for in-motion wpt with circuit parameter deviations. In 2020 IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer (WoW) (pp. 158-163). IEEE. Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the conventional power transmitting and receiving system 100, it is necessary to provide an inverter 12 for each primary coil 16. The inverter 12 accounts for approximately 33% of the installation cost of the conventional power transmitting and receiving system 100, which is an obstacle to installing the power transmitting and receiving system 100 at low cost.

[0006] In addition, as shown in FIG. 19, when a single inverter 12 is provided for multiple primary coils 16, power is supplied to primary coils 16b to 16c other than the primary coil 16a under the vehicle 102, which causes a leakage magnetic field that is not effectively used, resulting in large losses.

[0007] Furthermore, as shown in FIG. 20, if the self-inductance of the secondary coil 18 provided in the vehicle 102 changes depending on road conditions, there is a problem in that the efficiency of the power supply decreases. [Means for solving the problem]

[0008] One aspect of the present invention is an impedance adjustment circuit that includes a series circuit in which a capacitor Cp and a switch are connected in series, a parallel circuit in which an inductor L is connected in parallel to the series circuit, and a capacitor Cs connected in series to the parallel circuit, and that is capable of controlling the impedance of the entire circuit by opening and closing the switch.

[0009] Here, the capacitor Cp, the inductor L and the capacitor Cs are connected at a driving frequency f=1 / (2π(LCp) 1 / 2 )=1 / (2π(LCs) 1 / 2 ) is preferably set to a value that resonates.

[0010] Another aspect of the present invention is an impedance adjustment circuit that includes a series circuit in which an inductor Lp and a switch are connected in series, a parallel circuit in which a capacitor C is connected in parallel to the series circuit, and an inductor Ls connected in series with the parallel circuit, and that is capable of controlling the impedance of the entire circuit by opening and closing the switch.

[0011] Here, the inductor Lp, the capacitor C, and the inductor Ls are driven at a driving frequency f=1 / (2π(LpC) 1 / 2 )=1 / (2π(LsC) 1 / 2 ) is preferably set to a value that resonates.

[0012] Moreover, it is preferable that the switch includes two semiconductor switches S1 and S2, and the semiconductor switches S1 and S2 are connected in anti-series.

[0013] It is also preferable that the semiconductor switches S1 and S2 repeatedly open and close mutually exclusively with a constant phase difference θ with respect to the current.

[0014] Another aspect of the present invention is a power transmission and reception system characterized in that the impedance adjustment circuit is connected between an external inductor and an inverter, and the impedance adjustment circuit controls the exchange of power between the external inductor and the inverter. Effect of the Invention

[0015] According to the present invention, it is possible to reduce the number of inverters provided in the power transmission and reception system, thereby reducing the number of parts and installation costs. In addition, it is possible to suppress a decrease in power supply efficiency when the self-inductance of the primary coil on the power transmission side and the secondary coil on the power reception side changes due to an external factor. [Brief description of the drawings]

[0016] [Figure 1] 1 is a diagram showing a configuration of a power transmitting and receiving system according to an embodiment of the present invention. [Diagram 2] 1 is a diagram showing a configuration of an impedance adjustment circuit according to an embodiment of the present invention; [Diagram 3] 5A and 5B are diagrams illustrating control for placing the impedance adjustment circuit in a parallel resonance state in the embodiment of the present invention. [Figure 4] 5A and 5B are diagrams illustrating control for placing the impedance adjustment circuit in a parallel resonance state in the embodiment of the present invention. [Diagram 5] 5A and 5B are diagrams illustrating control for putting an impedance adjustment circuit into a series resonance state in the embodiment of the present invention. [Figure 6] 5A and 5B are diagrams illustrating control for putting an impedance adjustment circuit into a series resonance state in the embodiment of the present invention. [Figure 7] 4A to 4C are diagrams illustrating control during use of the power transmitting and receiving system according to the embodiment of the present invention. [Figure 8] 4A to 4C are diagrams illustrating control during use of the power transmitting and receiving system according to the embodiment of the present invention. [Figure 9] 11 is a diagram showing another example of the configuration of the impedance adjustment circuit according to the embodiment of the present invention. [Figure 10] 1 is a diagram showing a configuration in which an impedance adjustment circuit is applied to a power receiving side in an embodiment of the present invention. [Figure 11] 5A and 5B are diagrams illustrating control of impedance adjustment performed by an impedance adjustment circuit according to an embodiment of the present invention. [Figure 12] 5A and 5B are diagrams illustrating simulation results of impedance adjustment by the impedance adjustment circuit according to the embodiment of the present invention. [Figure 13] 5A and 5B are diagrams illustrating simulation results of impedance adjustment by the impedance adjustment circuit according to the embodiment of the present invention. [Figure 14] FIG. 2 is a diagram showing a configuration for performing a simulation of impedance adjustment by an impedance adjustment circuit according to an embodiment of the present invention. [Figure 15] FIG. 4 is a diagram showing the effect of impedance adjustment on conversion efficiency in the embodiment of the present invention. [Figure 16] 1 is a diagram showing a comparison list between an impedance adjustment circuit according to an embodiment of the present invention and a conventional compensation circuit; [Figure 17] 1 is a diagram showing an overall view of a power transmitting and receiving system according to an embodiment of the present invention. [Figure 18] FIG. 1 is a diagram illustrating a configuration of a conventional power transmitting and receiving system. [Figure 19] FIG. 1 is a diagram illustrating control during use of a conventional power transmitting and receiving system. [Figure 20] FIG. 1 is a diagram showing the influence on the conversion efficiency of a conventional power transmission and reception system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] As shown in FIG. 1, a power transmission and reception system 200 according to an embodiment of the present invention includes a DC power supply 20, an inverter 22 (22a to 22d), a resonant coil 24 (24a to 24d), a primary coil 26 (26a to 26d), and an impedance adjustment circuit 30 (30a to 30d).

[0018] The power transmission and reception system 200 is disposed under a road and is used to supply electric power in a contactless manner to a vehicle 202 traveling on the road.

[0019] The primary coil 26 is disposed on or under the road surface of the road on which the vehicle 202 travels. The primary coils 26 are preferably disposed side by side along the direction of the lane on which the vehicle 202 travels. The vehicle 102 is provided with a secondary coil 28 under the body facing the road. A power receiving circuit (not shown) is connected to the secondary coil 28. A magnetic field generated by the primary coil 26 is magnetically coupled with the secondary coil 28 to generate an induced voltage in the secondary coil 28. This allows the vehicle 202 to use or store the power received by the secondary coil 28.

[0020] The inverter 22, the impedance adjustment circuit 30, the resonant coil 24, and the primary coil 26 are combined one by one and connected to the DC power supply 20. In the present embodiment, a configuration example in which four sets of the inverter 22, the impedance adjustment circuit 30, the resonant coil 24, and the primary coil 26 are provided is shown.

[0021] The inverter 22 may have a general configuration, for example, the inverter 22 may have a circuit configuration in which two sets of switches, each set including an upper arm and a lower arm, are connected in series, are connected in parallel.

[0022] FIG. 2 shows a specific configuration of the impedance adjustment circuit 30. The impedance adjustment circuit 30 includes a capacitor Cp, a capacitor Cs, an inductor L, a switch S1, and a switch S2. A diode is connected in parallel to each of the switches S1 and S2. The switches S1 and S2 are connected in anti-series such that the diodes have opposite polarities. The capacitor Cp is connected in series to the switches S1 and S2. The inductor L is connected in parallel to the series-connected circuit of the capacitor Cp, the switches S1, and the switches S2. Furthermore, the capacitor Cs is connected in series to these circuits. The connection point between the capacitor Cp and the inductor L is connected to one end of the output of the inverter 22. The end of the capacitor Cs that is not connected to the inductor L is connected to the other end of the output of the inverter 22 via the resonant coil 24 and the primary coil 26.

[0023] The impedance adjustment circuit 30 is an active compensation circuit that can be turned on / off by phase control of the switches S1 and S2. The impedance adjustment circuit 30 can exclusively switch between a parallel resonance state and a series resonance state by opening and closing control of the switches S1 and S2. In the parallel resonance state, the equivalent impedance of the impedance adjustment circuit 30 can be regarded as infinite. At this time, the coil current Ic does not flow through the primary coil 26. On the other hand, in the series resonance state, the equivalent impedance of the impedance adjustment circuit 30 can be regarded as zero. At this time, the coil current Ic flows through the primary coil 26.

[0024] 3 to 6 show specific examples of control of the impedance adjustment circuit 30. The switches S1 and S2 are switched complementarily with respect to the output voltage of the inverter 22 with a phase difference θ.

[0025] 3 and 4, when the phase difference θ is −90°, the capacitor Cp is in a constant conduction mode, and the impedance adjustment circuit 30 is in a parallel resonance state. At this time, the impedance of the impedance adjustment circuit 30 when viewed from the primary coil 26 side is infinite, and the coil current Ic flowing through the primary coil 26 is zero.

[0026] 5 and 6, when the phase difference θ is +90°, the current flowing through the capacitor Cp becomes zero, and the impedance adjustment circuit 30 enters a series resonance state. At this time, the impedance of the impedance adjustment circuit 30 as viewed from the primary coil 26 becomes zero, and a coil current Ic flows through the primary coil 26.

[0027] 7 and 8 are diagrams for explaining a method of using the power transmitting and receiving system 200. As shown in Fig. 7, when a vehicle 202 to which power is to be supplied is traveling on a road on which the power transmitting and receiving system 200 is installed, the impedance adjustment circuits 30 (30a to 30d) are controlled so that the coil current Ic flows only in the primary coil 26 (26a) located under the vehicle 202 and the coil current Ic does not flow in the other primary coils 26 (26b to 26d). That is, the impedance adjustment circuit 30 (30a) connected to the primary coil 26 (26a) located under the vehicle 202 is controlled to be in a series resonance state, and the impedance adjustment circuits 30 (30b to 30d) connected to the primary coils 26 (26b to 26d) not located under the vehicle 202 are controlled to be in a parallel resonance state.

[0028] When the vehicle 202 moves forward over the primary coil 26 (26b), as shown in Fig. 8, the impedance adjustment circuits 30 (30a to 30d) are controlled so that the coil current Ic flows only through the primary coil 26 (26b) located under the vehicle 202 and the coil current Ic does not flow through the other primary coils 26 (26a, 26c, 26d). That is, the impedance adjustment circuit 30 (30b) connected to the primary coil 26 (26b) located under the vehicle 202 is controlled to be in a series resonance state, and the impedance adjustment circuits 30 (30a, 30c, 30d) connected to the primary coil 26 (20a, 26c, 26d) not located under the vehicle 202 are controlled to be in a parallel resonance state.

[0029] In this way, by controlling the state of the impedance adjustment circuit 30 in accordance with the position of the vehicle 202 to which the power is to be supplied, it is possible to select the primary coil 26 to be used for supplying power to the vehicle 202. Therefore, the inverter 22 can be shared by a plurality of primary coils 26 without increasing the leakage magnetic field and coil loss.

[0030] FIG. 9 shows an example of an impedance adjustment circuit 32 having another circuit configuration. The impedance adjustment circuit 32 includes an inductor Lp, an inductor Ls, a capacitor C, a switch S1, and a switch S2. A diode is connected in parallel to each of the switches S1 and S2. The switches S1 and S2 are connected in anti-series such that the diodes have opposite polarities. The inductor Lp is connected in series to the switches S1 and S2. The capacitor C is connected in parallel to the series-connected circuit of the inductor Lp, the switches S1, and the switches S2. Furthermore, the inductor Ls is connected in series to these circuits. The connection point between the inductor Lp and the capacitor C is connected to one end of the output of the inverter 22. The end of the inductor Ls that is not connected to the capacitor C is connected to the other end of the output of the inverter 22 via the resonant coil 24 and the primary coil 26.

[0031] The impedance adjustment circuit 32 can be used in place of the impedance adjustment circuit 30. Like the impedance adjustment circuit 30, the impedance adjustment circuit 32 is an active compensation circuit that can be turned on / off by phase control of the switches S1 and S2. The impedance adjustment circuit 32 can exclusively switch between a parallel resonance state and a series resonance state by opening and closing control of the switches S1 and S2. In the parallel resonance state, the equivalent impedance of the impedance adjustment circuit 30 can be regarded as infinite. At this time, the coil current Ic does not flow through the primary coil 26. On the other hand, in the series resonance state, the equivalent impedance of the impedance adjustment circuit 30 can be regarded as zero. At this time, the coil current Ic flows through the primary coil 26.

[0032] The impedance adjustment circuit 30 (or the impedance adjustment circuit 32) can also be used as an impedance adjustment circuit on the power receiving side. Fig. 10 shows an example of a circuit configuration in which the impedance adjustment circuit 30 is used as an impedance adjustment circuit in a power receiving side circuit of a vehicle 202.

[0033] The end of the capacitor Cs in the impedance adjustment circuit 30 that is not connected to the inductor L is connected to one end of the output of the inverter 22. The connection point between the capacitor Cp and the inductor L in the impedance adjustment circuit 30 is connected to the other end of the output of the inverter 36 via the resonance coil 34 and the secondary coil 28.

[0034] The inverter 36 may have a general configuration. For example, the inverter 36 may have a circuit configuration in which two sets of switches, each of which is a switch constituting an upper arm and a switch constituting a lower arm, are connected in series, and the two sets are connected in parallel.

[0035] 11 shows an example of impedance adjustment using the impedance adjustment circuit 30. The receiving current I RBy switching the switches S1 and S2 complementarily with a phase difference θ with respect to the impedance adjustment circuit 30, the current flowing into the capacitor Cp can be adjusted, thereby making the impedance adjustment circuit 30 function as a variable capacitor.

[0036] 12 and 13 show the inductance compensation characteristics (imaginary part characteristics) and valve characteristics (real part characteristics) when the impedance adjustment circuit 30 is used. These characteristics are simulated when an AC current is supplied to the impedance adjustment circuit 30 in the circuit configuration shown in Fig. 14. Here, the equivalent impedance was evaluated by measuring the voltage generated in the impedance adjustment circuit 30 with respect to the phase difference θ with respect to the AC current supplied from the AC current source.

[0037] When the phase difference θ is between -90deg and 0deg, the impedance adjustment circuit 30 transitions so that the impedance characteristics change gradually from the parallel resonance state. In this range of the phase difference θ, the inductance compensation characteristics (imaginary part characteristics) show a characteristic of decreasing from -90deg to -45deg and increasing from -45deg to 0deg. Also, the valve characteristics (real part characteristics) show a characteristic of decreasing from -90deg to 0deg.

[0038] When the phase difference θ is between 0° and +90°, the impedance adjustment circuit 30 gradually approaches a series resonance state, and reaches the series resonance state at +90°. In this range of phase difference θ, the inductance compensation characteristic (imaginary part characteristic) gradually increases from 0° to +90° and saturates to 0 at +90°, as shown in Fig. 13. Also, the valve characteristic (real part characteristic) is zero from 0° to +90°. In other words, the reactance goes from zero to negative values ​​over the range of phase difference θ from 0° to +90°, and the real part impedance remains 0, so it was confirmed that the circuit functions as a variable capacitor.

[0039] Fig. 15 shows the results of a simulation of the efficiency improvement effect of the power receiving circuit due to the impedance compensation function of the impedance adjustment circuit 30. In Fig. 15, triangles indicate the power conversion efficiency when the impedance adjustment circuit 30 is not provided, and circles indicate the power conversion efficiency when the impedance adjustment circuit 30 is provided. It was confirmed that the power conversion efficiency of the power transmission and reception system 100 can be improved by up to 47% by an inductance compensation amount of ±0.9 µH with respect to the reference inductance of 18 µH.

[0040] FIG. 16 shows a comparison table between a compensation circuit in the prior art and a compensation circuit to which the impedance adjustment circuit 30 in the embodiment of the present invention is applied. As shown in FIG. 16, the impedance adjustment circuit 30 (or the impedance adjustment circuit 32) in the embodiment of the present invention can realize a valve function that can turn on / off the current in a parallel resonance state and a series resonance state. In contrast, the compensation circuit in the prior art cannot completely turn on / off the current. Furthermore, according to the impedance adjustment circuit 30 (or the impedance adjustment circuit 32) in the embodiment of the present invention, the imaginary part impedance can be adjusted in a wide range from a negative value (-X) to zero. In contrast, the compensation circuit in the prior art can only adjust the imaginary part impedance in a predetermined range of negative values.

[0041] 17 shows a system configuration diagram in which the impedance adjustment circuit 30 is applied to the power transmitting and receiving system 100 and the vehicle 202. In the power transmitting and receiving system 100, the impedance adjustment circuit 30 is provided for each of the primary coils 26. The impedance adjustment circuit 30 has a valve function for switching between a parallel resonance state and a series resonance state, making it possible to select whether or not to transmit the power supplied from the inverter 22 to the primary coil 26.

[0042] Therefore, the power transmitting and receiving system 100 can be realized by simply providing a common inverter 22 for the multiple primary coils 26, without providing an individual inverter 22 for each primary coil 26. In this way, the number of inverters 22 provided in the power transmitting and receiving system 100 can be reduced, and the number of parts and installation costs can be reduced.

[0043] Furthermore, an impedance adjustment circuit 30 is provided as an impedance adjustment circuit in the power receiving circuit of the vehicle 202. This makes it possible to appropriately adjust the impedance of the power receiving circuit when power is received by magnetic coupling between the primary coil 26 and the secondary coil 28. This makes it possible to suppress a decrease in power supply efficiency when the self-inductance of the primary coil 26 on the power transmitting side and the secondary coil 28 on the power receiving side changes due to an external factor.

[0044] [Configuration of the present invention] [Configuration 1] A parallel circuit including a series circuit in which a capacitor Cp and a switch are connected in series, and an inductor L is connected in parallel to the series circuit; A capacitor Cs connected in series with the parallel circuit; Equipped with An impedance adjustment circuit capable of controlling the impedance of the entire circuit by opening and closing the switch. [Configuration 2] 2. The impedance adjustment circuit according to claim 1, The capacitor Cp, the inductor L and the capacitor Cs are driven at a driving frequency f=1 / (2π(LCp) 1 / 2 )=1 / (2π(LCs) 1 / 2 ) is set to a value that resonates. [Configuration 3] A parallel circuit including a series circuit in which an inductor Lp and a switch are connected in series, and a capacitor C is connected in parallel to the series circuit; an inductor Ls connected in series with the parallel circuit; Equipped with An impedance adjustment circuit capable of controlling the impedance of the entire circuit by opening and closing the switch. [Configuration 4] 4. The impedance adjustment circuit according to configuration 3, The inductor Lp, the capacitor C, and the inductor Ls are driven at a driving frequency f=1 / (2π(LpC) 1 / 2 )=1 / (2π(LsC) 1 / 2 ) is set to a value that resonates. [Configuration 5] The impedance adjustment circuit according to any one of configurations 1 to 4, The switch includes two semiconductor switches S1 and S2. The impedance adjustment circuit is characterized in that the semiconductor switch S1 and the semiconductor switch S2 are connected in anti-series. [Configuration 6] 6. The impedance adjustment circuit according to configuration 5, The impedance adjustment circuit is characterized in that the semiconductor switch S1 and the semiconductor switch S2 repeatedly open and close mutually exclusively with a constant phase difference θ with respect to current. [Configuration 7] The impedance adjustment circuit according to configuration 1 or 3 is included, the impedance adjustment circuit is connected between an external inductor and an inverter; A power transmission and reception system, characterized in that the impedance adjustment circuit controls the transmission and reception of power between the external inductor and the inverter. [Explanation of symbols]

[0045] 10 DC power supply, 12 inverter, 12 (12a to 12d) inverter, 14 (14a to 14d) resonant coil, 16 (16a to 16d) primary coil, 18 secondary coil, 20 DC power supply, 22 (22a to 22d) inverter, 24 (24a to 24d) resonant coil, 26 (26a to 26d) primary coil, 28 secondary coil, 30 impedance adjustment circuit, 30 (30a to 30d) impedance adjustment circuit, 32 impedance adjustment circuit, 34 resonant coil, 36 inverter, 100 power transmission and receiving system, 102 vehicle, 200 power transmission and receiving system, 202 vehicle.

Claims

1. a parallel circuit including a series circuit in which a capacitor Cp and a switch are connected in series, and an inductor L is connected in parallel to the series circuit; A capacitor Cs connected in series with the parallel circuit; Equipped with An impedance adjustment circuit capable of controlling the impedance of the entire circuit by opening and closing the switch.

2. 2. The impedance adjustment circuit according to claim 1, The capacitor Cp, the inductor L and the capacitor Cs are connected to each other at a driving frequency f=1 / (2π(LCp) １／２ )=1 / (2π(LCs) １／２ ) is set to a value that resonates at said impedance adjustment circuit.

3. a series circuit including an inductor Lp and a switch connected in series, and a parallel circuit including a capacitor C connected in parallel to the series circuit; An inductor Ls connected in series with the parallel circuit; Equipped with An impedance adjustment circuit capable of controlling the impedance of the entire circuit by opening and closing the switch.

4. 4. The impedance adjustment circuit according to claim 3, The inductor Lp, the capacitor C, and the inductor Ls are driven at a driving frequency f=1 / (2π(LpC) １／２ )=1 / (2π(LsC) １／２ ) is set to a value that resonates at said impedance adjustment circuit.

5. The impedance adjustment circuit according to any one of claims 1 to 4, The switch includes two semiconductor switches S1 and S2. The impedance adjustment circuit is characterized in that the semiconductor switch S1 and the semiconductor switch S2 are connected in anti-series.

6. 6. The impedance adjustment circuit according to claim 5, The impedance adjustment circuit is characterized in that the semiconductor switch S1 and the semiconductor switch S2 repeatedly open and close mutually exclusively with a constant phase difference θ with respect to current.

7. The impedance adjustment circuit according to claim 1 or 3 is included, the impedance adjustment circuit is connected between an external inductor and an inverter; A power transmission and reception system, characterized in that the impedance adjustment circuit controls the transmission and reception of power between the external inductor and the inverter.

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