Power transmission / reception system

Abstract

A power transmission / reception system according to the present disclosure comprises a plurality of power transmission coils, resonance capacitors, a first rectifier circuit, and a second rectifier circuit, and is capable of charging / discharging a battery. The power transmission / reception system controls the switching ratio between the first rectifier circuit and the second rectifier circuit according to the DC current of the battery and a current detected in each of the power transmission coils.

Description

Power transmission and reception system Cross-references to related applications

[0001] This application is based on patent application no. 2024-167522, filed on 26 September 2024, and claims the benefit of priority thereunder, the entirety of which is incorporated herein by reference.

[0002] This disclosure relates to power transmission and reception systems.

[0003] Patent Document 1 discloses a power transmission and reception system comprising a coil and inverter (sometimes referred to as a roadside coil and roadside inverter) located on the roadside, a coil (sometimes referred to as a vehicle-side coil) located on the vehicle side, a rectifier circuit, and a resonant circuit. The rectifier circuit has an active semiconductor element and a voltage sensor, and transmits and receives power from the roadside coil and roadside inverter in a contactless manner. In this power transmission and reception system, the coil is connected to two-phase legs, and the timing for turning on each switch is determined by a voltage detection circuit in each leg. The power transmission and reception system achieves synchronous rectification operation by generating a gate signal based on the determination result. In addition, the power transmission and reception system prevents unnecessary switching by prohibiting switching in each leg when the output current is sufficiently low, depending on the detected value of the output power.

[0004] Japanese Patent Publication No. 2024-22249

[0005] A power transmission and reception system with multiple vehicle-side coils is controlled by applying synchronous rectification control. In this configuration, current flows only to the vehicle-side coils that have strong magnetic coupling with the roadside coils. In other words, only some of the vehicle-side coils are used. As a result, the received current is concentrated in some coils, which degrades the power transmission and reception efficiency, or a large current flows in some coils, increasing the leakage magnetic field. Therefore, there is a need in this field for technologies that improve these issues. This disclosure provides a technology that prevents the voltage conversion ratio from becoming extremely large, thereby achieving miniaturization and high efficiency.

[0006] A first aspect of the present disclosure is a power transmission and reception system capable of charging and discharging a battery, comprising a plurality of coil windings, a plurality of resonant circuits, and a plurality of rectifier circuits connected to the coil windings and the resonant circuits. Each of the rectifier circuits is composed of a plurality of legs equipped with switching elements capable of controlling switching. The power transmission and reception system is configured to control the switching ratio of each of the rectifier circuits according to the DC current of the battery and the detected current in each of the coil windings.

[0007] Here, it is preferable that the power transmission and reception system is configured to control the switching ratio of the rectifier circuit so as to satisfy conditions related to both efficiency and leakage magnetic field.

[0008] Furthermore, the power transmission and reception system calculates a first difference between the DC current and a target value of the DC current, calculates a second difference between each detected current and the average value of the detected currents, and calculates a third difference between the calculated second difference and a target value of the second difference. The power transmission and reception system is preferably configured to control the switching ratio according to the calculated first difference and third difference.

[0009] Furthermore, each rectifier circuit is configured to include a plurality of legs in which the switching elements are connected in series. Preferably, the plurality of coil windings are configured to include coil windings connected between the legs included in each rectifier circuit.

[0010] Furthermore, it is preferable that the plurality of coil windings be configured to include coil windings connected between the legs included in different rectifier circuits.

[0011] According to this disclosure, it is possible to prevent the voltage conversion ratio from becoming extremely large and to provide a power transmission and reception system that is miniaturized and highly efficient.

[0012] This figure shows an example configuration of a power transmission and reception system according to the first embodiment. This figure shows the control block of the power transmission and reception system according to the first embodiment. This figure shows an example configuration of a power transmission and reception system according to the second embodiment. This figure shows an example configuration of a power transmission coil in the power transmission and reception system according to the second embodiment. This figure shows the first control block of the power transmission and reception system according to the second embodiment. This figure shows the results of an operation simulation of the power transmission and reception system according to the second embodiment. This figure shows the second control block of the power transmission and reception system according to the second embodiment.

[0013] Embodiments of the present disclosure will be described below. The same reference numerals are used for identical components shown in multiple drawings to simplify their description. Unless otherwise specified, terms indicating directions such as up, down, left, and right in this specification refer to the directions in the drawings. These terms are for convenience to clarify the description and do not limit the orientation of each component when it is positioned.

[0014] As shown in Figure 1, the power transmission and receiving system 100 in the first embodiment is configured to include a power transmission device 102, a power conversion device 104, and a control unit 106.

[0015] The power transmission device 102 is used, for example, as a roadside device placed on the road surface where a vehicle travels. The power converter 104 is used, for example, as a vehicle-side device mounted on a vehicle. The power transmission and reception system 100 is used for power transmission, supplying power from the power transmission device 102 to the power converter 104 wirelessly. The power transmission and reception system 100 is also used for power transmission while the vehicle is in motion. The power converter 104 is mounted on a vehicle such as an electric vehicle and can send and receive current between the device and the power transmission device 102.

[0016] The power transmission device 102 is comprised of a DC voltage source 10, an input capacitor 12, a switching bridge 14, a resonant capacitor 16, and a transmission coil 18.

[0017] The DC voltage source 10 may include an AC / DC converter that converts AC power supplied from a commercial power system (power grid) into DC power. Alternatively, the DC voltage source 10 may be a battery. The switching bridge 14 has a configuration in which switching elements 14-1 and 14-2 connected in series and switching elements 14-3 and 14-4 connected in series are connected in parallel. The switching elements 14-1 to 14-4 may be semiconductor elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The configuration in which two MOSFETs are connected in series is one in which the source of the second MOSFET is connected to the drain of the first MOSFET. The configuration in which two IGBTs are connected in series is one in which the collector of the second IGBT is connected to the emitter of the first IGBT. The diagram shows that each of the switching elements 14-1 to 14-4 has the function of a recirculating diode.

[0018] The input capacitor 12 and the switching bridge 14 are connected in parallel to the DC voltage source 10. The first terminal of the resonant capacitor 16 is connected to the connection point between switching elements 14-3 and 14-4. The first terminal of the transmission coil 18 is connected to the second terminal of the resonant capacitor 16. The second terminal of the transmission coil 18 is connected to the connection point between switching elements 14-1 and 14-2.

[0019] Although Figure 1 shows a configuration of the power transmission device 102 equipped with only one set of resonant capacitor 16 and transmission coil 18, the configuration is not limited to this. The power transmission device 102 may be configured in which multiple sets of resonant capacitor 16 and transmission coil 18 are connected in parallel. Alternatively, the power transmission device 102 may be configured in which multiple sets of resonant capacitor 16 and transmission coil 18 are connected in series. Furthermore, the power transmission device 102 may be equipped with multiple sets of resonant capacitor 16 and transmission coil 18, with a first set connected in parallel and a second set connected in series to the first set connected in parallel. By arranging multiple sets of resonant capacitor 16 and transmission coil 18 along the road, the power transmission system 100 can charge and discharge the battery even when a vehicle equipped with the power converter 104 is traveling on the road.

[0020] The power conversion device 104 is comprised of a power transmission coil 20 (20a, 20b), resonant capacitors 24 (24a, 24b), a first rectifier circuit 26a and a second rectifier circuit 26b, smoothing capacitors 28 (28a, 28b), and a battery 30.

[0021] Of the two ends of the power transmission coil 20 (20a, 20b), the terminal indicated by the black dot in the figure is the reference end. The reference end is defined as the terminal at which an induced electromotive force of the same polarity appears when the magnetic flux linking two adjacent power transmission coils in the same direction increases or decreases. In the following explanation, of the two ends of the power transmission coil 20 (20a, 20b), the terminal opposite to the reference end is called the dependent end (the terminal located opposite the black dot). However, the terms reference end and dependent end are merely convenient terms used to distinguish the polarity of the windings. The terms reference end and dependent end do not limit the structure of the windings, such as the winding method.

[0022] The power transmission coil 20a is connected in series with the resonant capacitor 24a. The power transmission coil 20b is connected in series with the resonant capacitor 24b. The power transmission coil 20a and the resonant capacitor 24a are connected to the first rectifier circuit 26a. The power transmission coil 20b and the resonant capacitor 24b are connected to the second rectifier circuit 26b.

[0023] In this embodiment, it is preferable that the power transmission coil 20a and the power transmission coil 20b be coils of different types, forms, shapes, and sizes. For example, the power transmission coil 20a is a DD coil composed of eight-shaped coils. The power transmission coil 20b is a Q coil made up of multiple coils. In this embodiment, different types, forms, shapes, and sizes of coils are applied to the power transmission coil 20a and the power transmission coil 20b. This increases the possibility that the power transmission and reception system 100 can transmit and receive power using the second coil (for example, the power transmission coil 20b) even when the first coil (for example, the power transmission coil 20a) is unable to transmit or receive power.

[0024] The first rectifier circuit 26a has a configuration in which switching elements 26a-1 and 26a-2 connected in series and switching elements 26a-3 and 26a-4 connected in series are connected in parallel. The switching elements 26a-1 to 26a-4 may be semiconductor elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The configuration in which two MOSFETs are connected in series is one in which the source of the second MOSFET is connected to the drain of the first MOSFET. The configuration in which two IGBTs are connected in series is one in which the collector of the second IGBT is connected to the emitter of the first IGBT. Note that in the figure, each of the switching elements 26a-1 to 26a-4 is shown to have the function of a recirculating diode. In other words, the first rectifier circuit 26a includes a first leg in which switching elements 26a-1 and 26a-2 are connected in series, and a second leg in which switching elements 26a-3 and 26a-4 are connected in series.

[0025] The reference terminal of the power transmission coil 20a is connected to the first terminal of the resonant capacitor 24a. The second terminal of the resonant capacitor 24a is connected to the connection point of switching elements 26a-1 and 26a-2 of the first rectifier circuit 26a. The dependent terminal of the power transmission coil 20a is connected to the connection point of switching elements 26a-3 and 26a-4 of the first rectifier circuit 26a. In other words, the power transmission coil 20a is connected between the legs included in the first rectifier circuit 26a.

[0026] Furthermore, the first rectifier circuit 26a is connected in parallel to the smoothing capacitor 28a and the battery 30. That is, the first terminal of the smoothing capacitor 28a and the positive terminal of the battery 30 are connected to the connection point of the first rectifier circuit 26a that connects switching elements 26a-1 and 26a-3. The second terminal of the smoothing capacitor 28a and the negative terminal of the battery 30 are connected to the connection point of the first rectifier circuit 26a that connects switching elements 26a-2 and 26a-4.

[0027] The second rectifier circuit 26b has a configuration in which switching elements 26b-1 and 26b-2 connected in series and switching elements 26b-3 and 26b-4 connected in series are connected in parallel. Switching elements 26b-1 to 26b-4 may be semiconductor elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The configuration in which two MOSFETs are connected in series is one in which the source of the second MOSFET is connected to the drain of the first MOSFET. The configuration in which two IGBTs are connected in series is one in which the collector of the second IGBT is connected to the emitter of the first IGBT. Note that in the figure, each of the switching elements 26b-1 to 26b-4 is shown to have the function of a recirculating diode. In other words, the second rectifier circuit 26b includes a third leg in which switching elements 26b-1 and 26b-2 are connected in series, and a fourth leg in which switching elements 26b-3 and 26b-4 are connected in series.

[0028] The reference terminal of the power transmission coil 20b is connected to the first terminal of the resonant capacitor 24b. The second terminal of the resonant capacitor 24b is connected to the connection point of switching elements 26b-1 and 26b-2 of the second rectifier circuit 26b. The dependent terminal of the power transmission coil 20b is connected to the connection point of switching elements 26b-3 and 26b-4 of the second rectifier circuit 26b. In other words, the power transmission coil 20b is connected between the legs included in the second rectifier circuit 26b.

[0029] Furthermore, the second rectifier circuit 26b is connected in parallel to the smoothing capacitor 28b and the battery 30. Specifically, the first terminal of the smoothing capacitor 28b and the positive terminal of the battery 30 are connected to the connection point of the second rectifier circuit 26b that connects switching elements 26b-1 and 26b-3. The second terminal of the smoothing capacitor 28b and the negative terminal of the battery 30 are connected to the connection point of the second rectifier circuit 26b that connects switching elements 26b-2 and 26b-4.

[0030] The battery 30 may be connected in parallel to the load device. The load device includes, for example, a circuit that drives a motor to propel a vehicle such as an electric car. Alternatively, the load device may be connected instead of the battery 30.

[0031] The switching elements 14-1 to 14-4 of the power transmission device 102 are switched to control the conversion of the DC voltage source 10 into AC power of a desired frequency. Switching elements 14-1 and 14-2 are switched to switch on and off alternately. That is, when switching element 14-1 switches from off to on, switching element 14-2 switches from on to off. Similarly, switching elements 14-3 and 14-4 are switched to switch on and off alternately. That is, when switching element 14-3 switches from off to on, switching element 14-4 switches from on to off. The switching phase of switching elements 14-3 and 14-4 lags behind the switching phase of switching elements 14-1 and 14-2 by 180°-δ, where δ is a phase angle smaller than 180°.

[0032] During the phase angle between 0° and 180°-δ (first period), switching elements 14-1 and 14-4 are on, and switching elements 14-2 and 14-3 are off. During this first period, a voltage Vdc is applied to the resonant capacitor 16 and the transmission coil 18. During the phase angle between 180°-δ and 180° (second period), switching elements 14-1 and 14-3 are on, and switching elements 14-2 and 14-4 are off. During this second period, the voltage applied to the resonant capacitor 16 and the transmission coil 18 is 0. During the phase angle between 180° and 360°-δ (third period), switching elements 14-1 and 14-4 are off, and switching elements 14-2 and 14-3 are on. During this third period, a voltage -Vdc is applied to the resonant capacitor 16 and the transmission coil 18. During the phase angle between 360°-δ and 360° (the fourth period), switching elements 14-1 and 14-3 are off, and switching elements 14-2 and 14-4 are on. During this fourth period, the voltage applied to the resonant capacitor 16 and the transmission coil 18 is 0. In this way, the voltage Vin applied to the resonant capacitor 16 and the transmission coil 18 repeats over time as Vdc, 0, -Vdc, 0, Vdc, 0, -Vdc, ... due to the switching of switching elements 14-1 to 14-4.

[0033] The control unit 106 controls the switching of the first rectifier circuit 26a and the second rectifier circuit 26b of the power converter 104. Specifically, the control unit 106 controls the DC current I flowing through the battery 30. ＤＣ , detection current I ＡＣ１ , and detected current I ＡＣ２ Accordingly, the switching ratio (duty cycle) Duty1 of the first rectifier circuit 26a and the switching ratio (duty cycle) Duty2 of the second rectifier circuit 26b are controlled. ＡＣ１ This is the detection current of the coil winding of the power transmission coil 20a. Detection current I ＡＣ２ This is the detected current of the coil winding of the power transmission coil 20b.

[0034] Note that the detected current I ＡＣ１ and detected current I ＡＣ２is the alternating current i flowing through each of the coil windings of the power transmission coil 20a and the power transmission coil 20b ＡＣ１ and the alternating current i ＡＣ２ shows the absolute value of the amplitude.

[0035] FIG. 2 shows a control block (configuration example of a control circuit) of the control unit 106. The control unit 106 includes an AC control block unit and a DC control block unit.

[0036] The AC control block unit processes the detected current I ＡＣ１ and the detected current I ＡＣ２ input thereto. First, the AC control block unit calculates the average value I ＡＣ１ and the detected current I ＡＣ２ of the detected current I ａｖｅ . Next, the AC control block unit calculates the first difference value (I ＡＣ１ -I ａｖｅ ) between the detected current I ＡＣ１ and the average value I ａｖｅ and the second difference value (I ＡＣ２ -I ａｖｅ ) between the detected current I ＡＣ２ and the average value I ａｖｅ . Further, the AC control block unit calculates the third difference value between the first difference value (I ＡＣ１ -I ａｖｅ ) and the target value of the first difference value (I ＡＣ１ -I ａｖｅ ) ＊ . The AC control block unit calculates the fourth difference value between the second difference value (I ＡＣ２ -I ａｖｅ ) and the target value of the second difference value (I ＡＣ２ -I ａｖｅ ) ＊ . The AC control block unit applies PI control to these values (the third and fourth difference values) and outputs them.

[0037] The DC control block unit processes the direct current I ＤＣ flowing through the battery 30 as an input. First, the DC control block unit calculates the fifth difference value (I ＤＣ between the direct current I ＤＣ and the target value I ＤＣ ＊ of the direct current IＤＣ -I ＤＣ ＊ The DC control block calculates this value (the fifth difference value). The DC control block then applies PI control to this value and outputs it.

[0038] The control unit 106 adds the output of the AC control block and the output of the DC control block to generate the switching ratio Duty 1 of the first rectifier circuit 26a and the switching ratio Duty 2 of the second rectifier circuit 26b, and outputs them to the power converter 104. Specifically, the control unit 106 calculates the first difference value (I ＡＣ１ -I ａｖｅ ) and the target value of the first difference (I ＡＣ１ -I ａｖｅ ) ＊ The PI control value of the third difference value and the fifth difference value (I ＤＣ -I ＤＣ ＊ The PI control value of (I) is added to the second difference value (I ＡＣ２ -I ａｖｅ ) and the target value of the second difference (I ＡＣ２ -I ａｖｅ ) ＊ The PI control value of the fourth difference value and the fifth difference value (I ＤＣ -I ＤＣ ＊ The PI control value of ) is added to the value of ). Then, the control unit 106 generates the switching ratio Duty2 of the second rectifier circuit 26b according to the added value and outputs it to the power converter 104.

[0039] The control unit 106 controls the switching of the switching elements 26a-1 to 26a-4 of the first rectifier circuit 26a of the power converter 104 according to the switching ratio Duty 1 of the first rectifier circuit 26a. Furthermore, the control unit 106 controls the switching of the switching elements 26b-1 to 26b-4 of the second rectifier circuit 26b of the power converter 104 according to the switching ratio Duty 2 of the second rectifier circuit 26b. Thus, the control unit 106 has the above-mentioned DC control block and AC control block. As a result, the power transmission and reception system 100 controls the DC current I of the battery 30.ＤＣ and the detected current I in each of the coil windings of the power transmission coils 20a and 20b ＡＣ１ , I ＡＣ２ Accordingly, the switching ratios Duty 1 and Duty 2 of the first rectifier circuit 26a and the second rectifier circuit 26b are determined. The power transmission and reception system 100 can control the balance of the current (coil current) flowing through the power transmission coils 20a and 20b by controlling the switching of each rectifier circuit based on the determined switching ratios (duty cycles), thereby preventing current from concentrating in a particular coil. As a result, the power transmission and reception system 100 can reduce deterioration of power transmission and reception efficiency and increase in leakage magnetic field.

[0040] As shown in Figure 3, the power transmission and receiving system 110 in the second embodiment is configured to include a power transmission device 112, a power conversion device 114, and a control unit 116.

[0041] The power transmission device 112 is used, for example, as a roadside device placed on the road surface where a vehicle travels. The power converter 114 is used, for example, as a vehicle-side device mounted on a vehicle. The power transmission and reception system 110 is used for power transmission, supplying power from the power transmission device 112 to the power converter 114 wirelessly. The power transmission and reception system 110 is also used for power transmission while the vehicle is in motion. The power converter 114 is mounted on a vehicle such as an electric vehicle and can send and receive current between the device and the power transmission device 112.

[0042] The power transmission device 112 has the same configuration as the power transmission device 102 in the power transmission and reception system 100 of the first embodiment. Therefore, a description of the power transmission device 112 will be omitted.

[0043] The power conversion device 114 is comprised of power transmission coils 20 (20a, 20b, 20c, 20d), resonant capacitors 24 (24a, 24b, 24c, 24d), a first rectifier circuit 26a and a second rectifier circuit 26b, smoothing capacitors 28 (28a, 28b), and a battery 30.

[0044] The first rectifier circuit 26a has a configuration in which switching elements 26a-1 and 26a-2 connected in series and switching elements 26a-3 and 26a-4 connected in series are connected in parallel. The switching elements 26a-1 to 26a-4 may be semiconductor elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The configuration in which two MOSFETs are connected in series is one in which the source of the second MOSFET is connected to the drain of the first MOSFET. The configuration in which two IGBTs are connected in series is one in which the collector of the second IGBT is connected to the emitter of the first IGBT. Note that in the figure, each of the switching elements 26a-1 to 26a-4 is shown to have the function of a recirculating diode.

[0045] In other words, the first rectifier circuit 26a includes a first leg in which switching elements 26a-1 and 26a-2 are connected in series, and a second leg in which switching elements 26a-3 and 26a-4 are connected in series.

[0046] Furthermore, the first rectifier circuit 26a is connected in parallel to the smoothing capacitor 28a and the battery 30. That is, the first terminal of the smoothing capacitor 28a and the positive terminal of the battery 30 are connected to the connection point of the first rectifier circuit 26a that connects switching elements 26a-1 and 26a-3. The second terminal of the smoothing capacitor 28a and the negative terminal of the battery 30 are connected to the connection point of the first rectifier circuit 26a that connects switching elements 26a-2 and 26a-4.

[0047] The second rectifier circuit 26b has a configuration in which switching elements 26b-1 and 26b-2 connected in series and switching elements 26b-3 and 26b-4 connected in series are connected in parallel. Switching elements 26b-1 to 26b-4 may be semiconductor elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The configuration in which two MOSFETs are connected in series is one in which the source of the second MOSFET is connected to the drain of the first MOSFET. The configuration in which two IGBTs are connected in series is one in which the collector of the second IGBT is connected to the emitter of the first IGBT. Note that in the figure, each of the switching elements 26b-1 to 26b-4 is shown to have the function of a recirculating diode.

[0048] In other words, the second rectifier circuit 26b includes a third leg in which switching elements 26b-1 and 26b-2 are connected in series, and a fourth leg in which switching elements 26b-3 and 26b-4 are connected in series.

[0049] Furthermore, the second rectifier circuit 26b is connected in parallel to the smoothing capacitor 28b and the battery 30. Specifically, the first terminal of the smoothing capacitor 28b and the positive terminal of the battery 30 are connected to the connection point of the second rectifier circuit 26b that connects switching elements 26b-1 and 26b-3. The second terminal of the smoothing capacitor 28b and the negative terminal of the battery 30 are connected to the connection point of the second rectifier circuit 26b that connects switching elements 26b-2 and 26b-4.

[0050] The battery 30 may be connected in parallel to the load device. The load device includes, for example, a circuit that drives a motor to propel a vehicle such as an electric car. Alternatively, the load device may be connected instead of the battery 30.

[0051] Of the ends of the power transmission coil 20 (20a, 20b, 20c, 20d), the terminals indicated by black dots in the figure are the reference ends. The reference ends are defined as terminals where an induced electromotive force of the same polarity appears when the magnetic flux linking two adjacent power transmission coils in the same direction increases or decreases. In the following explanation, of the ends of the power transmission coil 20 (20a, 20b, 20c, 20d), the terminals opposite to the reference ends are referred to as the dependent ends. However, the terms reference end and dependent end are merely convenient terms used to distinguish the polarity of the windings. The terms reference end and dependent end do not limit the structure of the windings, such as the winding method.

[0052] In this embodiment, the power transmission coils 20 (20a, 20b, 20c, 20d) are preferably flat, stackless coils formed in a rectangular loop shape. Figure 4 shows an example of the configuration of the power transmission coils 20 (20a, 20b, 20c, 20d) as a circuit diagram. Each power transmission coil 20a to 20d is formed in a rectangular loop shape and is flat using conductors. The power transmission coils 20a to 20d are arranged in a predetermined direction so that the areas around which the conductors circulate do not overlap. The number of turns of the power transmission coils 20a to 20d is the same. That is, each power transmission coil 20a to 20d is composed of conductors that circulate in a rectangular shape with the same number of turns in a counterclockwise direction from the reference end to the dependent end. In two adjacent power transmission windings, the conductors corresponding to the sides extending in the vertical direction are arranged in close proximity. When the magnetic flux linking two adjacent power transmission windings in the same direction increases or decreases, induced electromotive forces of the same polarity appear at the reference ends of the two adjacent power transmission windings, with respect to their respective dependent ends.

[0053] However, the power transmission coils 20 (20a, 20b, 20c, 20d) are not limited to these. For example, it is preferable that the power transmission coils 20 (20a, 20b, 20c, 20d) be coils of different types, forms, shapes, and sizes. In this embodiment, coils of different types, forms, shapes, and sizes are applied to the power transmission coils 20 (20a, 20b, 20c, 20d). This increases the possibility that the power transmission and reception system 110 can transmit and receive power using the second coil even when the first coil cannot transmit or receive power.

[0054] The reference terminal of the power transmission coil 20a (the terminal shown as a black dot in Figure 3) is connected to the first terminal of the resonant capacitor 24a. The second terminal of the resonant capacitor 24a is connected to connection point Ta, which connects switching elements 26a-1 and 26a-2 of the first rectifier circuit 26a. The dependent terminal of the power transmission coil 20b (the terminal located on the opposite side of the black dot) is connected to the first terminal of the resonant capacitor 24b. The second terminal of the resonant capacitor 24b is connected to connection point Tb, which connects switching elements 26a-3 and 26a-4 of the first rectifier circuit 26a.

[0055] The reference terminal of the power transmission coil 20c is connected to the first terminal of the resonant capacitor 24c. The second terminal of the resonant capacitor 24c is connected to the connection point Tc that connects switching elements 26b-1 and 26b-2 of the second rectifier circuit 26b. The dependent terminal of the power transmission coil 20d is connected to the first terminal of the resonant capacitor 24d. The second terminal of the resonant capacitor 24d is connected to the connection point Td that connects switching elements 26b-3 and 26b-4 of the second rectifier circuit 26b.

[0056] The dependent end of power transmission coil 20a, the reference end of power transmission coil 20b, the dependent end of power transmission coil 20c, and the reference end of power transmission coil 20d are connected in common.

[0057] Specifically, power transmission coils 20a and 20b are connected between the first and second legs of the first rectifier circuit 26a. Power transmission coils 20c and 20d are connected between the third and fourth legs of the second rectifier circuit 26b. Power transmission coils 20b and 20c are connected between the second leg of the first rectifier circuit 26a and the third leg of the second rectifier circuit 26b.

[0058] The control unit 116 controls the switching of the first rectifier circuit 26a and the second rectifier circuit 26b of the power converter 114. Specifically, the control unit 116 controls the DC current I flowing through the battery 30. ＤＣ and detected current I ＡＣ１ ~I ＡＣ４Accordingly, the control unit 116 controls the switching duty cycles (Duty 1 to Duty 4) of each leg. More specifically, the control unit 116 controls the switching duty cycle (Duty 1) of the first leg, which consists of switching elements 26a-1 and 26a-2 of the first rectifier circuit 26a. The control unit 116 controls the switching duty cycle (Duty 2) of the second leg, which consists of switching elements 26a-3 and 26a-4 of the first rectifier circuit 26a. The control unit 116 controls the switching duty cycle (Duty 3) of the third leg, which consists of switching elements 26b-1 and 26b-2 of the second rectifier circuit 26b. The control unit 116 controls the switching duty cycle (Duty 4) of the fourth leg, which consists of switching elements 26b-3 and 26b-4 of the second rectifier circuit 26b. Note that the detected current I ＡＣ１ ~I ＡＣ４ This represents the detected current in each of the coil windings of the power transmission coils 20a to 20d.

[0059] Figure 5 shows the first control block of the control unit 116 (an example of the control circuit configuration). The control unit 116 includes an AC control block section and a DC control block section.

[0060] The AC control block detects the current I in each of the coil windings of the power transmission coils 20a to 20d. ＡＣ１ ~I ＡＣ４ The AC control block processes the detected current I. ＡＣ１ ~I ＡＣ４ The average value I ａｖｅ Next, the AC control block calculates the detected current I ＡＣ１ and the average value I ａｖｅ The first difference value (I ＡＣ１ -I ａｖｅ ), detected current I ＡＣ２ and the average value I ａｖｅ The second difference value (I ＡＣ２ -I ａｖｅ ), detected current I ＡＣ３ and the average value I ａｖｅ The third difference value (I ＡＣ３ -I ａｖｅ ), and detected current I ＡＣ４and the average value I ａｖｅ and the fourth difference value (I ＡＣ４ −I ａｖｅ ). Further, the AC control block section calculates the fifth difference value between the first difference value (I ＡＣ１ −I ａｖｅ ) and the target value of the first difference value (I ＡＣ１ −I ａｖｅ ), the sixth difference value between the second difference value (I ＊ −I ＡＣ２ ) and the target value of the second difference value (I ａｖｅ −I ＡＣ２ ) ａｖｅ ), the seventh difference value between the third difference value (I ＊ −I ＡＣ３ ) and the target value of the third difference value (I ａｖｅ −I ＡＣ３ ) ａｖｅ ), and the eighth difference value between the fourth difference value (I ＊ −I ＡＣ４ ) and the target value of the fourth difference value (I ａｖｅ −I ＡＣ４ ). The AC control block section applies PI control to these values (the fifth to eighth difference values) and outputs them.

[0061] The DC control block section performs processing with the DC current I ａｖｅ flowing through the battery 30 as an input. First, the DC control block section calculates the ninth difference value (I ＊ −I ＤＣ ) between the DC current I ＤＣ and the target value I ＤＣ of the DC current I ＤＣ ＊ . The DC control block section applies PI control to this value (the ninth difference value) and outputs it.

[0062] The control section 116 adds the output of the AC control block section and the output of the DC control block section, generates the switching time ratios Duty1 to Duty4, and outputs them to the power conversion device 114. Specifically, the control section 116 calculates the first difference value (I ＤＣ −I ＤＣ ) and the target value of the first difference value (I ＊ −I ＡＣ１ )[[ID=​​​​​The PI control value of the fifth difference value and the ninth difference value (I ＤＣ -I ＤＣ ＊ The PI control value of (I) is added to the second difference value (I). Then, the control unit 116 generates the switching ratio Duty1 of the first leg according to the added value and outputs it to the power converter 114. The control unit 116 also generates the second difference value (I) ＡＣ２ -I ａｖｅ ) and the target value of the second difference (I ＡＣ２ -I ａｖｅ ) ＊ The PI control value of the sixth difference value and the ninth difference value (I ＤＣ -I ＤＣ ＊ The PI control value of (I) is added to the value of (I). Then, the control unit 116 generates the switching ratio Duty2 of the second leg according to the added value and outputs it to the power converter 114. The control unit 116 also generates the third difference value (I) ＡＣ３ -I ａｖｅ ) and the target value of the third difference (I ＡＣ３ -I ａｖｅ ) ＊ The PI control value of the 7th difference value and the 9th difference value (I ＤＣ -I ＤＣ ＊ The PI control value of (I) is added to the value of (I). Then, the control unit 116 generates the switching ratio Duty 3 of the third leg according to the added value and outputs it to the power converter 114. The control unit 116 also generates the fourth difference value (I ＡＣ４ -I ａｖｅ ) and the target value of the fourth difference (I ＡＣ４ -I ａｖｅ ) ＊ The PI control value of the 8th difference value and the 9th difference value (I ＤＣ -I ＤＣ ＊ The PI control value of ) is added to and . Then, the control unit 116 generates the switching ratio Duty 4 of the fourth leg according to the added value and outputs it to the power converter 114.

[0063] The control unit 116 controls the switching of switching elements 26a-1 and 26a-2 of the first rectifier circuit 26a of the power converter 114 according to the switching ratio Duty 1 of the first leg. The control unit 116 also controls the switching of switching elements 26a-3 and 26a-4 of the first rectifier circuit 26a of the power converter 114 according to the switching ratio Duty 2 of the second leg. The control unit 116 also controls the switching of switching elements 26b-1 and 26b-2 of the second rectifier circuit 26b of the power converter 114 according to the switching ratio Duty 3 of the third leg. The control unit 116 also controls the switching of switching elements 26b-3 and 26b-4 of the second rectifier circuit 26b of the power converter 114 according to the switching ratio Duty 4 of the fourth leg. Thus, the control unit 116 has the DC control block and the AC control block. As a result, the power transmission and reception system 110 controls the DC current I of the battery 30. ＤＣ and the detected current I in the coil windings of the power transmission coils 20a to 20d ＡＣ１ ~I ＡＣ４ Accordingly, the switching ratios Duty 1 to Duty 4 of the first to fourth legs are controlled. The power transmission and reception system 110 can control the balance of the current (coil current) flowing through the power transmission coils 20a to 20d by controlling the switching of each leg based on the determined switching ratio (duty cycle), preventing current from concentrating in a particular coil. As a result, the power transmission and reception system 110 can reduce deterioration of power transmission and reception efficiency and increase in leakage magnetic field.

[0064] Figure 6 shows the results of the operation simulation of the power transmission and reception system 110 in this embodiment. In Figure 6, the results up to 8 ms show the results when the current balance control (switching control) in this embodiment is not applied, and the results from 8 ms onward show the results when the current balance control in this embodiment is applied.

[0065] In other words, when current balance control is not applied, independent switching control is performed in the following three states. The first state is when the first leg of switching elements 26a-1 and 26a-2 is used in combination with the second leg of switching elements 26a-3 and 26a-4. The second state is when the second leg of switching elements 26a-3 and 26a-4 is used in combination with the third leg of switching elements 26b-1 and 2ba-2. The third state is when the third leg of switching elements 26b-1 and 26b-2 is used in combination with the fourth leg of switching elements 26b-3 and 26b-4.

[0066] On the other hand, when current balance control is applied, the power transmission and reception system 110 controls the DC current I flowing through the battery 30, as shown in Figure 5. ＤＣ and the detected current I in each of the coil windings of the power transmission coils 20a to 20d ＡＣ１ ~I ＡＣ４ Accordingly, the system generates switching ratios Duty 1 for the first leg, Duty 2 for the second leg, Duty 3 for the third leg, and Duty 4 for the fourth leg. The power transmission and reception system 110 then sets the generated switching ratios Duty 1 to Duty 4 for each leg in the power converter 114. As a result, the power transmission and reception system 110 performs switching control to balance the current (coil current) flowing through the power transmission coils 20a to 20d.

[0067] As shown in Figure 6, when current balance control is not applied, for example, current flows only through power transmission coils 20b and 20c, and the current amplitude becomes large, up to about 100A. In contrast, when current balance control is applied, the current flows evenly through power transmission coils 20a to 20d, and the current amplitude is about 63A. In other words, by applying current balance control, the power transmission and reception system 110 can reduce the amplitude of the current flowing through power transmission coils 20a to 20d (coil current) by 37% while keeping the charging and discharging current to the battery 30 constant. In this way, the power transmission and reception system 110 can reduce the current peak by distributing the current from two coils to four coils, and can reduce copper loss in the coil windings of the vehicle-side coils by 21% (= (63^2 × 4) / (100^2 × 2)). Therefore, the deterioration of power transmission and reception efficiency is reduced in the system 110. Furthermore, in the power transmission and reception system 110, the magnetic field generated by the additional received current weakens the leakage magnetic field, thus reducing the leakage magnetic field can also be expected.

[0068] Figure 7 shows the second control block of the control unit 116 (an example of the control circuit configuration). The control unit 116 includes an AC control block section and a DC control block section.

[0069] The AC control block may have a configuration that includes a reference table (reference database). The input values ​​of the reference table are the detected current I ＡＣ１ , I ＡＣ２ , I ＡＣ３ , and I ＡＣ４ These are the switching ratios (duty cycles) Duty1, Duty2, Duty3, and Duty4. The output values ​​of the reference table are the detected current I ＡＣ１ and the average value I ａｖｅ The target value of the first difference (I ＡＣ１ -I ａｖｅ ) ＊ , detection current I ＡＣ２ and the average value I ａｖｅ The target value of the second difference (I ＡＣ２ -I ａｖｅ ) ＊ , detection current I ＡＣ３ and the average value I ａｖｅThe target value of the third difference (I ＡＣ３ -I ａｖｅ ) ＊ , and detected current I ＡＣ４ and the average value I ａｖｅ The target value of the fourth difference (I ＡＣ４ -I ａｖｅ ) ＊ The AC control block may have a reference table in which such input and output values ​​are associated. The relationship between these input and output values ​​is determined and set in advance to be within a predetermined limit range (range between upper and lower limits) that can suppress the increase in leakage magnetic field and / or circuit loss (coil loss) of the power transmission and reception system 110.

[0070] According to the above configuration, in the power transmission and reception system 110, the control unit 116 detects the current I ＡＣ１ , I ＡＣ２ , I ＡＣ３ , and I ＡＣ４ The switching ratios (duty cycles) Duty1, Duty2, Duty3, and Duty4 are input as input values. The control unit 116 retrieves the target values ​​(I) of the first to fourth difference values ​​set in association with the input values ​​from the reference table (reference database). ＡＣ１ -I ａｖｅ ) ＊ , (I ＡＣ２ -I ａｖｅ ) ＊ , (I ＡＣ３ -I ａｖｅ ) ＊ , (I ＡＣ４ -I ａｖｅ ) ＊ The control unit 116 reads out the target value (I) of the read-out first to fourth difference values. ＡＣ１ -I ａｖｅ ) ＊ , (I ＡＣ２ -I ａｖｅ ) ＊ , (I ＡＣ３ -I ａｖｅ ) ＊ , (I ＡＣ４ -I ａｖｅ ) ＊This is used to control the switching ratios Duty 1 to Duty 4 of the first to fourth legs. As a result, the power transmission and reception system 110 can be controlled within a numerical range in which the increase in the leakage magnetic field and / or circuit losses of the system can be suppressed.

[0071] [Configuration of the Disclosure] [Configuration 1] A power transmission and reception system capable of charging and discharging a battery, comprising: a plurality of coil windings; a plurality of resonant circuits; and a plurality of rectifier circuits formed by combining a plurality of legs connected to the coil windings and the resonant circuits and equipped with switching elements capable of controlling switching, wherein the power transmission and reception system is configured to control the switching ratio of each rectifier circuit according to the DC current of the battery and the detected current in each of the coil windings. [Configuration 2] The power transmission and reception system according to Configuration 1, wherein the power transmission and reception system is configured to control the switching ratio of the rectifier circuits so as to satisfy conditions relating to both efficiency and leakage magnetic field. [Configuration 3] A power transmission and reception system according to Configuration 1, wherein a first difference value is calculated between the DC current and a target value of the DC current; a second difference value is calculated between each detected current and the average value of the detected currents; a third difference value is calculated between the calculated second difference value and a target value of the second difference value; and the switching ratio is controlled according to the calculated first difference value and the third difference value. [Configuration 4] A power transmission and reception system according to any one of Configurations 1 to 3, wherein each rectifier circuit is configured to include a plurality of legs in which the switching elements are connected in series; and the plurality of coil windings are configured to include coil windings connected between the legs included in each rectifier circuit. [Configuration 5] A power transmission and reception system according to Configuration 4, wherein the plurality of coil windings are configured to include coil windings connected between the legs included in different rectifier circuits. [Configuration 6] A power transmission and reception system according to Configuration 3, wherein a database is set in which the target value of the second difference value is set as an output value corresponding to the input value which is the detected current and the switching ratio, and the system is configured to calculate the third difference value between the second difference value and the target value of the second difference value output from the database based on the input value.

Claims

1. A power transmission and reception system capable of charging and discharging a battery, comprising: a plurality of coil windings; a plurality of resonant circuits; and a plurality of rectifier circuits formed by combining a plurality of legs connected to the coil windings and the resonant circuits and equipped with switching elements capable of controlling switching, wherein the power transmission and reception system is configured to control the switching ratio of each rectifier circuit according to the DC current of the battery and the detected current in each of the coil windings.

2. A power transmission and reception system according to claim 1, wherein the switching ratio of the rectifier circuit is controlled to satisfy conditions relating to both efficiency and leakage magnetic field.

3. A power transmission and reception system according to claim 1, comprising: calculating a first difference between the DC current and a target value of the DC current; calculating a second difference between each detected current and the average value of the detected currents; calculating a third difference between the calculated second difference and a target value of the second difference; and controlling the switching ratio according to the calculated first difference and the third difference.

4. A power transmission and reception system according to any one of claims 1 to 3, wherein each rectifier circuit is configured to include a plurality of legs in which the switching elements are connected in series, and the plurality of coil windings are configured to include coil windings connected between the legs included in each rectifier circuit.

5. A power transmission and reception system according to claim 4, wherein the plurality of coil windings are configured to include coil windings connected between the legs included in different rectifier circuits.

6. A power transmission and reception system according to claim 3, comprising a database in which target values ​​of the second difference value are set as output values ​​corresponding to input values ​​which are the detected current and the switching ratio, and configured to calculate the third difference value between the second difference value and the target value of the second difference value output from the database based on the input value.

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