JP6512600B2 - Contactless power transmission circuit and contactless power supply system - Google Patents

Description

  The present invention relates to a contactless power transfer circuit and a contactless power feeding system, and is particularly useful when applied to a case where the distance between opposing coils is large to transfer power.

  As a next-generation charging system for electric vehicles, non-contact charging technology has attracted attention from the viewpoint of convenience and the like. As this kind of non-contact charge technology, there are known a non-contact charge system utilizing electromagnetic induction and a non-contact charge system utilizing magnetic resonance. The non-contact charging method using magnetic resonance can transmit larger power even if the coupling coefficient between multiple coils is smaller than the electromagnetic induction method, and the distance between adjacent coils can be increased accordingly it can.

  As a prior art regarding the electric power transmission using a magnetic resonance system, the non-contact electric power feeding system disclosed by patent document 1 which concerns on invention of this inventor etc. exists. The non-contact power feeding system disclosed in Patent Document 1 utilizes a magnetic resonance system from a coil at one end to a coil at the other end by sequentially arranging a plurality of coils adjacent to each other via a predetermined distance. And a contactless power transfer circuit for transferring power. And the inverter which converts direct-current power supplied from direct-current power supply into alternating current power of a predetermined voltage and frequency is connected to the coil by the side of one end of the non-contact electric power transmission circuit concerned. Further, to the coil on the other end side of the non-contact power transmission circuit, a converter that converts AC power supplied via the coil into predetermined DC power and supplies the DC power to the DC load is connected.

JP, 2014-217117, A

  In the noncontact power feeding system disclosed in Patent Document 1, since the plurality of resonant circuits in the noncontact power transmission circuit are formed using a plurality of coils, the winding resistance and loss of each coil increase. The increase in the winding resistance and the loss can be reduced by decreasing the DC resistance value by increasing the cross sectional area of each coil. However, when the cross-sectional area of the coil is increased, the weight of the entire coil increases, causing a new problem of increasing the size. As the number of coils increases, the new problems described above become more pronounced. That is, if a coil having a large wire diameter and a large cross-sectional area is manufactured by bundling a large number of strands, it is possible to reduce Joule heat which causes the largest loss in the noncontact power transmission circuit. However, as the cross-sectional area increases, the cost also increases due to the increase in coil weight and the like.

  In view of the above-mentioned prior art, the present invention realizes reduction of power consumption as much as possible while reducing power consumption as much as possible when adopting magnetic resonance method as non-contact transmission method. It is an object of the present invention to provide a contactless power transfer circuit and a contactless power supply system having the same, which is optimized to be able to

  The configuration of the present invention for achieving the above object is based on the findings based on the following experiments.

  The experiment was conducted using the non-contact power feeding system shown in FIG. In the noncontact power feeding system shown in FIG. 1, the power conversion devices 2 and 3 are respectively connected to one end side (transmission side) and the other end side (reception side) of the noncontact power transmission circuit 1. The non-contact power transmission circuit 1 transmits AC power supplied from one end to the other end. Therefore, it has four coils consisting of two coils 1B and 1C juxtaposed between the coil 1A on the transmission side, the coil 1D on the reception side, the coil 1A and the coil 1D, and adjacent ones Constitute a resonant circuit. Further, the power conversion device 2 functions as an inverter that converts DC power supplied from the DC power supply 4 into AC power. The power conversion device 3 functions as a converter that converts AC power into DC power and supplies the DC load 5.

  It was found that the power loss for each device configuration in the non-contact power feeding system is the largest loss in the non-contact power transmission circuit 1 composed of four coils 1A to 1D.

  Therefore, in order to improve the transmission efficiency, it is effective to reduce the Joule loss of the coils 1A to 1D in the non-contact power transmission circuit 1 portion. In order to reduce the Joule loss, the cross-sectional area of the coils 1A to 1D may be increased. However, simply increasing the size of the coils 1A to 1D increases the weight and size of the coils 1A to 1D, which causes a new problem.

  Therefore, the efficiency of the power transmission coil formed by the coils 1A to 1D was examined by variously changing the structures and combinations of the coils 1A to 1D. Here, the pre-rectification output is transmission power in the non-contact power feeding system and input power to the converter.

  FIG. 2 is a characteristic diagram showing the efficiency of the coils 1A to 1D forming the power transfer coil with respect to the output before rectification. In the figure, the solid line I represents the coil arrangement (to be described later) 2-2-2-2. The long dotted line II represents the coil arrangement 2-1-1-2, the short dotted line III represents the coil arrangement 1 In the case of -1-1-1, the alternate long and short dash line IV indicates the case where the coil arrangement is 1-2-2-1. Here, when the coil arrangement is “1”, when the coils 1A to 1D are used as a conventional single-turn coil, the coil arrangement “2” is a conventional single-turn coil double-wound and both are used. This is a case where the cross-sectional area is doubled by connecting in parallel. Therefore, the coil arrangement of solid line I, 2-2-2-2 are all double-wound coils 1A-1D, the coil arrangement of long dotted line II, 2-1-1-2 are one end side and the other end The side coils 1A and 1D are double-wound coils, and the intermediate coils 1B and 1C are single-wound coils. Hereinafter, the short dotted dotted line III coil arrangement, 1-1-1-1 are all single-wound coils 1A-1D, and are the same as conventional coils. Further, a coil arrangement of a dashed dotted line IV, 1-2-2-1 indicates that the coils 1A and 1D are single-wound coils, and that the coils 1B and 1C are double-wound coils.

  Referring to FIG. 2, when the coil arrangement is 2-1-1-2 (long dotted line II), the efficiency similar to that of the coil arrangement 2-2-2-2 (solid line I) is obtained. There is. This improves the efficiency from 71% to 80% when the coil arrangement is 1-1-1-1 (short dotted line III), which is the conventional structure, when the coil arrangement is 2-1-1-2. It means that you can. In addition, the output of the said non-contact electric power feeding system in this case is 1.8 kW.

  The above-mentioned results regarding the efficiency are simultaneously obtained by increasing the coil weight of the power transmission coil and increasing the coil arrangement by changing the coil arrangement to 2-2-2-2. This means that the efficiency can be greatly increased compared to the conventional case. That is, by forming two coils 1A and 1D at both ends of the four coils as double-wound coils, the coil weight and the enlargement can be suppressed as much as possible to improve the power transmission efficiency. We have found that we can The same effect is considered to be similarly established even if the number of coils between the coils 1A and 1D is one or three or more, if at least the two coils 1A and 1D at both end sides are formed by double wound coils. .

  In addition, each coil 1A-1D which obtains the result shown in FIG. 2 is comprised with the strand wire which bundled the enameled copper wire (strand) of an outer diameter of 0.3 mm. Therefore, at a high frequency (for example, 20 kHz used in the circuit shown in FIG. 1), the current is unevenly distributed due to the skin effect or the proximity effect, and the effective cross-sectional area decreases to increase the AC resistance component and increase the Joule heat loss. That is, in each case shown in FIGS. 3A to 3C, accurate Joule heat evaluation can not be performed only by considering only the DC resistance. Here, FIG. 3 (a) is a cross section of a single-wound coil formed by a stranded wire A obtained by bundling enameled copper wires having an outer diameter of 0.3 mm, and FIG. 3 (b) is a single-wound coil formed by a stranded wire A. A cross section of a double-wound coil formed by connecting two coils in parallel, FIG. 3 (c) is a stranded wire B obtained by bundling enameled copper wires with an outer diameter of 0.3 mm, and the horizontal width is a stranded wire A It is the cross section of the single-winding coil which comprised the same as the formed single-winding coil, and doubled the cross-sectional area.

  In the case of the single-turn coil shown in FIG. 3A, the winding resistance value was 0.08Ω. This is twice the theoretical DC resistance value of 0.04 Ω based on the wire diameter, length, resistivity and the like. This means that the current is unevenly distributed in the cross-sectional area portion corresponding to half of the 50 pieces of wire due to the skin effect and the proximity effect (the unevenly distributed region is shown in gray in FIG. 3A). ing. On the other hand, the winding resistance of the parallel double wound coil is 0.05 Ω. The theoretical DC resistance value for this decreases to 0.02 Ω, but the current is unevenly distributed in the cross-sectional area equivalent to 40 of the 100 wires due to the proximity effect and the increase of the skin effect (the uneven distribution area 3 (b) is shown in gray). That is, in the case of a single-wound coil, the effective cross-sectional area capable of flowing current is 25 (50) / 50 (pieces), whereas in the case of a parallel double-wound coil, the effective cross-sectional area capable of flowing current is 40 (40 Book) / 100 (book) Therefore, although the effective cross-sectional area is increased in the case of the parallel double-wound coil, the influence of the uneven current distribution is further increased. This is because the stranded wire A in the case of the parallel double-wound coil is not only in the horizontal direction but also adjacent in the vertical direction as well, so the proximity effect acts largely.

  On the other hand, when the cross-sectional shape of the stranded wire A shown in FIG. 3B has a circular double-layer structure and the cross-sectional shape of the stranded wire B shown in FIG. In the case of the structure, a space C is formed between adjacent strands A, and in the case of a simple flat angle, the surfaces of the adjacent strands B are in contact with each other and there is no space. Therefore, in the case of the stranded wire A having a circular two-layer structure, the influence of the proximity effect and the like can be made smaller than in the case of the stranded wire B having a simple flat angle. Incidentally, in the case of a simple flat single-turn coil, its winding resistance was 0.08 Ω. This is four times the theoretical DC resistance value of 0.02 Ω based on the wire diameter, length, resistivity, etc., and the cross-sectional area for 25 of the 100 wires corresponds to 1/4. The current is unevenly distributed in the part (the unevenly distributed area is shown in gray in FIG. 3 (c).

The first aspect of the present invention based on the above findings is:
A contactless power transfer circuit for transmitting power using a magnetic resonance method from a coil on one end side to a coil on the other end side by sequentially arranging three coils side by side with a predetermined interval between adjacent coils. There,
A resonant circuit is formed by a closed circuit formed by a coil other than both ends of the at least three coils and a capacitor connected in parallel to the coils, and further, each coil of the both ends and parallel to each coil Form a resonant circuit with a closed circuit respectively formed by the other capacitors connected to
Further, in the non-contact power transmission circuit according to the present invention, the coils at both ends are formed to have a large cross-sectional area with respect to the other coils and a small direct current resistance.

  According to this aspect, the transmission efficiency of the power transmission by the magnetic resonance system can be improved by reducing the winding resistance of the coil at both ends. That is, the larger the cross-sectional area, the smaller the DC resistance and the smaller the Joule loss. However, in this case, the weight of the coil increases due to the increase in the cross-sectional area, and an increase in size can not be avoided. According to the present invention, by specifying the arrangement state of the plurality of coils, it is possible to improve the transmission efficiency while avoiding an increase in size of the entire coil as much as possible. As a result, optimization of the coil structure in the noncontact power transmission system can be realized.

The second aspect of the present invention is
In the contactless power transfer circuit described in the first aspect,
The coils at the both end portions are formed by laminating a plurality of coils formed by winding a wire having a circular cross section, and connecting the respective coils in parallel and integrating them. It is in the power transfer circuit.

  According to this aspect, since the air gaps are present between the coils which are stacked and adjacent to each other at the top, bottom, left, and right, the influence of the proximity effect can be reduced accordingly. In addition, since parameters such as inductance of each coil become the same, circuit design of the non-contact power transmission circuit becomes easy.

The third aspect of the present invention is
In the contactless power transfer circuit described in the first or second aspect,
The non-contact power transmission circuit is characterized in that the number of the coils is four, and each of the coils is arranged to be symmetrical.

  According to this aspect, bidirectional power transmission is possible.

The fourth aspect of the present invention is
The contactless power transfer circuit described in the first or second aspect,
A DC power supply is connected, and the DC output voltage of the DC power supply is converted to an AC voltage, and the coil at one end is connected so that the converted AC voltage is applied to the coil at one end of the noncontact power transmission circuit. One of the power conversion devices being driven as an inverter,
A converter connected to a coil at the other end of the non-contact power transfer circuit, converting an AC voltage applied via the coil at the other end into a DC output voltage and applying the DC output voltage to a DC load A noncontact power feeding system characterized by having the other power converter driven.

  According to this aspect, DC power supplied from the DC power source is converted into AC power by the inverter, and power transmission from one end to the other end is performed with high efficiency via the non-contact power transmission circuit, and the other end The converter can convert it into DC power and supply it to the DC load.

The fifth aspect of the present invention is
The contactless power transfer circuit described in the third aspect
One power converter connected to a coil at one end of the non-contact power transmission circuit;
While having the other power converter connected to the coil of the other end side of the non-contact power transmission circuit,
The one and the other power converters are driven as either an inverter or a converter, and a DC power supply and a DC load are respectively connected via switch means, and one or the other of the power converters is inverter-driven. The apparatus is connected to the DC power supply via the switch means, and a DC load is connected to the other or one of the power converters driven by the converter via the switch means. It is in the non-contact power supply system.

  According to this aspect, bidirectional power transmission via the inverter and the converter can be easily realized by switching the switch means.

  According to the present invention, it is possible to improve the efficiency of power transmission from one end side to the other end side of the power transmission coil by the magnetic resonance method while achieving the possible suppression of the weight and size increase of the power transmission coil.

It is a block diagram which shows the non-contact electric power feeding system for performing the experiment which obtains the knowledge which becomes the foundation of the present invention. It is a graph which shows the efficiency characteristic of the electric power transmission coil by the non-contact electric supply system shown in FIG. It is a conceptual diagram for verifying the influence of a proximity | contact effect | action and a skin effect based on the difference in coil shape. It is a block diagram which shows the coil arrangement | sequence of the non-contact electric power transmission circuit which concerns on embodiment of this invention. It is a block diagram which shows the non-contact electric power supply system which concerns on embodiment of this invention which has the non-contact electric power transmission circuit shown in FIG.

  Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 4 is a configuration diagram showing a coil arrangement of the non-contact power transmission circuit according to the embodiment of the present invention. As shown in the figure, the non-contact power transmission circuit 1 is formed by the coils 1A, 1B, 1C, 1D disposed similarly to FIG. 1 and capacitors C ₀ , C ₁ , C ₂ , C _3. The closed circuits are configured as symmetrical resonant circuits in the figure. That is, the four coils 1A to 1D in the present embodiment are sequentially juxtaposed in the axial direction between the adjacent coils (1A, 1B), (1B, 1C), and (1C, 1D) via a predetermined interval. , When the self inductances of the coils 1A to 1D are the same and the coupling coefficients between the coils 1A and 1B, between the coils 1B and 1C, and between the coils 1C and 1D are ka, kb and kc, the ratio is 2: It is configured to be 1: 2.

  Here, each of the coils 1A to 1D is formed by a stranded wire A formed by bundling a predetermined number of strands having a circular cross section in the same manner as the coils shown in FIGS. 3 (a) and 3 (b). The coils 1A and 1D at both ends of the coils 1A to 1D are double-wound coils in which two sheets of coils 1B and 1C, which are single-wound coils, are stacked and connected in parallel. As a result, the coils 1A and 1D at both ends have a larger cross-sectional area than the coils 1B and 1C which are single-wound coils, and the DC resistance is reduced.

  The coils 1A to 1D, in particular, the coils 1A and 1D at both ends do not necessarily have to be a stranded wire of a circular cross section. However, as in the present embodiment, in the case of a stranded wire having a circular cross section, as discussed in the comparison between FIG. 3 (b) and FIG. 3 (c), a space C between adjacent strands A (see FIG. 3 (b)). The presence of) can reduce the effects of proximity effects and skin effects.

  Further, although four coils 1A to 1D are used in this embodiment, three or more coils are formed so that the coils at both ends have a larger cross-sectional area and smaller DC resistance than the other coils. There is no further limitation if it is.

  In the non-contact power transmission circuit 1 according to the above-described embodiment, the coil arrangement is 2-1-1-2 according to the experimental result shown in FIG. Power transmission with high efficiency is possible compared to the case. On the other hand, although the power transfer efficiency is almost similar, the weight is halved as compared with the case of the coil arrangement 2-2-2-2, and miniaturization is also possible.

  FIG. 5 is a block diagram showing an example of a non-contact power feeding system according to an embodiment of the present invention having the non-contact power transmission circuit 1 shown in FIG. As shown in the figure, in the non-contact power feeding system, the power converter 2 on one side (left side in the figure; the same applies hereinafter) and the power converter 3 on the other side (right side in the figure; the same applies hereafter) While being separated via the contact power transfer circuit 1, they are configured symmetrically.

Power converters 2 and 3 connected to coil 1A and coil 1D function as an inverter or a converter. That is, the power conversion device 2 is connected to the DC power supply DC1 by turning on the switch SW1, and at the same time, functions as an inverter while the power conversion device 3 is connected to the load R2 by turning on the switch SW4. At this time, the power conversion device 3 functions as a converter. On the other hand, the power conversion device 3 is connected to the DC power supply DC2 by turning on the switch SW2, and at the same time, functions as an inverter while the power conversion device 2 is connected to the load R1 by turning on the switch SW3. At this time, the power conversion device 2 functions as a converter. In the figure, capacitors C ₄ and C ₅ are smoothing capacitors for suppressing the ripple voltage.

In this embodiment, buck-boost converters 7 and 8 having reactors L ₃ and L ₄ and capacitors C ₆ and C ₇ in addition to the semiconductor elements for switching are power converters 2 and 3 and DC power supplies DC1 and DC2 (load It is connected between R2 and R1).

  Buck-boost converter 7 is connected between DC power supply DC1 and load R1 and power conversion device 2 on one side, and buck-boost converter 8 is connected between DC power supply DC2 and load R2 and power conversion device 3 on the other side. It is connected to the. Thus, when transmitting power from one side to the other side, switch SW1 is turned on to connect DC power supply DC1 to the input side of step-up / down converter 7, and switch SW4 is turned on and load R2 is turned on. It is connected to the output side of the buck-boost converter 8. Conversely, when transmitting power from the other side to one side, switch SW2 is turned on to connect DC power supply DC2 to the input side of buck-boost converter 8, and switch SW3 is turned on to load R1. Are controlled to be connected to the output side of the buck-boost converter 7.

  The buck-boost converters 7 and 8 adjust the input voltage applied to the power conversion devices 2 and 3 to a predetermined value by the switching control, and adjust the input voltage applied to the loads R2 and R1 to a predetermined value.

  Switching at a predetermined frequency (for example, 18.63 kHz) of the power conversion devices 2 and 3 described above, switching for voltage adjustment of the buck-boost converters 7 and 8, and switching control of the switches SW1 to SW4 are performed by control means not shown. .

  According to the present embodiment as described above, when performing power transfer from one side to the other side, the DC power supply DC1 on one side is connected to the power conversion device 2 on one side functioning as an inverter via the switch SW1. When the load R2 on the other side is connected to the power conversion device 3 on the other side functioning as a converter via the switch SW4 and power is supplied from the other side to the one side, the device on the other side and the one side are connected Since the functions of the devices of (1) can be connected in reverse, bidirectional power transmission can be performed well.

  When the buck-boost converters 7 and 8 are provided as in the non-contact power feeding system described in the above embodiment, the voltage of each part can be adjusted arbitrarily, and DC power supplies DC1 and DC2 of various ratings and The inherent effect of being able to respond flexibly to the loads R1 and R2 is exhibited. These buck-boost converters 7 and 8 are not necessarily required if the voltage value on the power receiving side is not limited.

Also, the ratio of the coupling coefficients ka, kb and kc need not be 2: 1: 2. ka or k
It is sufficient if the ratio of c to kb is constant. Furthermore, the self inductances of the coils 1A to 1D do not have to be the same.

The present invention can be used in the industrial field to construct a system for bi-directionally transferring power between an electric vehicle and a fixed installation such as a house.

A, B Stranded wire 1 Non-contact power transmission circuit 1A, 1B, 1C, 1D coil 2, 3 Power converter

Claims (5)

A contactless power transfer circuit for transmitting power using a magnetic resonance method from a coil on one end side to a coil on the other end side by sequentially arranging three coils side by side with a predetermined interval between adjacent coils. There,
A resonant circuit is formed by a closed circuit formed by a coil other than both ends of the at least three coils and a capacitor connected in parallel to the coils, and further, each coil of the both ends and parallel to each coil Form a resonant circuit with a closed circuit respectively formed by the other capacitors connected to
Furthermore, the coils at both ends are formed so as to have a large cross-sectional area with respect to the other coils and a small direct current resistance. In the contactless power transfer circuit according to claim 1,
The coils at the both end portions are formed by laminating a plurality of coils formed by winding a wire having a circular cross section, and connecting the respective coils in parallel and integrating them. Power transmission circuit. In the contactless power transfer circuit according to claim 1 or 2,
The contactless power transfer circuit is characterized in that the number of the coils is four, and each of the coils is arranged to be symmetrical. The contactless power transfer circuit according to claim 1 or 2;
A DC power supply is connected, and the DC output voltage of the DC power supply is converted to an AC voltage, and the coil at one end is connected so that the converted AC voltage is applied to the coil at one end of the noncontact power transmission circuit. One of the power conversion devices being driven as an inverter,
A converter connected to a coil at the other end of the non-contact power transfer circuit, converting an AC voltage applied via the coil at the other end into a DC output voltage and applying the DC output voltage to a DC load A contactless power supply system characterized by having the other power converter driven. The contactless power transfer circuit according to claim 3;
One power converter connected to a coil at one end of the non-contact power transmission circuit;
While having the other power converter connected to the coil of the other end side of the non-contact power transmission circuit,
The one and the other power converters are driven as either an inverter or a converter, and a DC power supply and a DC load are respectively connected via switch means, and one or the other of the power converters is inverter-driven. The apparatus is connected to the DC power supply via the switch means, and a DC load is connected to the other or one of the power converters driven by the converter via the switch means. Contactless power supply system.