JP7021009B2 - Contactless power transfer system - Google Patents

Description

The present disclosure relates to a non-contact power transmission system, and more particularly to a non-contact power transmission system for transmitting power from a power transmitting device to a power receiving device in a non-contact manner.

Non-contact power transmission systems that transmit power from a power transmitting device to a power receiving device in a non-contact manner are known (see, for example, Patent Documents 1 to 5). In such a non-contact power transmission system, Japanese Patent Application Laid-Open No. 2013-243882 (Patent Document 6) provides a capacity switching mechanism in at least one of the power transmission unit of the power transmission device and the power reception unit of the power reception device, and receives power from the power transmission unit. It is disclosed that the capacity switching mechanism is operated so that the power transmission efficiency to the unit becomes higher (see Patent Document 6).

Japanese Unexamined Patent Publication No. 2013-154815 Japanese Unexamined Patent Publication No. 2013-146154 Japanese Unexamined Patent Publication No. 2013-146148 Japanese Unexamined Patent Publication No. 2013-110822 Japanese Unexamined Patent Publication No. 2013-126327 Japanese Unexamined Patent Publication No. 2013-243882

The larger the distance between the coil of the power transmission unit and the coil of the power reception unit, the smaller the coupling coefficient between the coils. In the non-contact power transmission system described in Patent Document 6, in order to improve the power transmission efficiency from the power transmission unit to the power reception unit when the coupling coefficient is small, a capacitance switching mechanism is provided to adjust the impedance and improve the power transmission efficiency. ing.

However, when a non-contact power transmission system is used to supply a large amount of power to a vehicle, a high voltage of several kV level can be applied to the power transmission unit and the power reception unit, so that the capacity switching mechanism has a high withstand voltage. Sex is required. Therefore, the physique of the power transmission unit and / or the power reception unit provided with the capacity switching mechanism as described above increases, and the cost also increases.

In addition, in order to improve the efficiency of the system as a whole, it is necessary to improve the power factor of power transmission as well as the power transmission efficiency from the power transmission unit to the power reception unit.

The present disclosure has been made to solve such a problem, and the purpose of the present disclosure is non-contact that can secure high power transmission efficiency and high power factor without providing the capacity switching mechanism as described above. It is to provide a power transmission system.

The non-contact power transmission system in the present disclosure is a non-contact power transmission system that non-contactly transmits power from a power transmission device to a power receiving device, and the power transmission device includes a first resonance circuit (transmission unit), an inverter, and the like. It is equipped with a filter circuit. The first resonant circuit is configured to include a first coil for non-contact power transmission to the power receiving device. The inverter is configured to generate alternating current transmission power and supply it to the first resonant circuit. The filter circuit is provided between the inverter and the first resonant circuit. The inverter can adjust the frequency of the transmitted power within a predetermined frequency adjustment range. The power receiving device includes a second resonance circuit (power receiving unit) configured to include a second coil for receiving power from the first resonance circuit in a non-contact manner. Then, in the second region where the distance between the coils is larger than that in the first region where the distance between the first coil and the second coil is small, the resonance frequency of the first resonance circuit and the second resonance circuit are used. The resonance frequency of is included in the above frequency adjustment range, and is closer to the upper limit than the lower limit of the frequency adjustment range.

By bringing the frequency of the transmitted power adjustable by the inverter closer to the resonant frequency of the second resonant circuit, even if the distance between the first coil and the second coil is large and therefore the coupling coefficient between the coils is small. , The power transmission efficiency from the first resonant circuit to the second resonant circuit can be increased.

In addition, in order to improve the efficiency of the entire system, it is necessary to improve the power factor. When a filter circuit is provided between the inverter and the first resonant circuit (transmission unit), the power factor can be increased by increasing the resonant frequency of the first resonant circuit (details are as follows). Later).

In this non-contact power transmission system, the resonance frequency of the first resonance circuit and the resonance frequency of the second resonance circuit are included in the frequency adjustment range and the frequency is adjusted in the second region where the distance between the coils is large. It is closer to the upper limit than the lower limit of the range. That is, the first and second resonant circuits are designed so that the resonant frequencies of the first and second resonant circuits are relatively high within the frequency adjustment range when the coupling coefficient between the coils is small. Resonance. As a result, even if the distance between the coils is large (even if the coupling coefficient is small), the power factor can be improved while ensuring high power transmission efficiency.

Further, as the distance between the coils becomes smaller (the coupling coefficient becomes larger), the resonance frequency of the first resonance circuit increases and the resonance frequency of the second resonance circuit decreases (details will be described later). In this non-contact power transmission system, in the second region where the distance between the coils is large, the resonance frequency of the second resonant circuit is closer to the upper limit than the lower limit of the frequency adjustment range. There is a large margin until the reduced resonance frequency of the second resonant circuit reaches the lower limit of the frequency adjustment range. This means that the frequency of the transmitted power can be adjusted to the resonance frequency of the second resonant circuit by the inverter even if the distance between the coils becomes small. Therefore, according to this non-contact power transfer system, the frequency of the transmitted power can be adjusted by the inverter to the resonant frequency of the second resonant circuit over a wide range of coil distances (ie, in a wide coupling coefficient). The efficiency between the coils can be ensured.

According to the non-contact power transmission system in the present disclosure, high power transmission efficiency and high power factor can be ensured.

It is an overall block diagram of the non-contact power transmission system according to embodiment of this disclosure. It is a figure which shows that the inductance of a coil changes according to the coupling coefficient between a coil. It is a figure which shows that the resonance frequency changes according to the coupling coefficient between coils. It is a figure which shows the relationship between the resonance frequency f1 and the efficiency between coils. It is a figure which shows the relationship between a resonance frequency f1 and a power factor. It is a figure which shows the relationship between the resonance frequency f1 and the frequency f of the power transmission power adjusted by an inverter when a desired power receiving power is secured in a power receiving device. As a reference example, it is a figure which shows the resonance frequency corresponding to the coupling coefficient when the resonance frequencies f1 and f2 are matched within the frequency adjustment range when the coupling coefficient between coils is large. It is a figure which shows the relationship between the coupling coefficient between coils, and the efficiency between coils. It is an overall block diagram of the non-contact power transmission system according to another embodiment.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

<Overall configuration of non-contact power transmission system>
FIG. 1 is an overall configuration diagram of a non-contact power transmission system according to an embodiment of the present disclosure. With reference to FIG. 1, this non-contact power transmission system includes a power receiving device 100 and a power transmitting device 200. The power receiving device 100 is mounted on a vehicle that can travel using the electric power stored in the power storage device 300, and the electric power received by the power receiving device 100 is stored in the power storage device 300.

For example, the power receiving device 100 is arranged on the lower surface of the vehicle body, and the power transmitting device 200 is arranged on the ground. Then, in a state where the vehicle is aligned with respect to the power transmission device 200 so that the power reception device 100 faces the power transmission device 200, electric power is transmitted from the power transmission device 200 to the power reception device 100 in a non-contact manner through a magnetic field.

The power transmission device 200 includes an AC / DC converter 210, an inverter 220, a filter circuit 230, a power transmission unit 240, a power transmission ECU (Electronic Control Unit) 250, and a communication unit 260.

The AC / DC converter 210 converts AC power received from an AC power source 400 such as a commercial system power supply into DC power and supplies it to the inverter 220. The AC / DC converter 210 is, for example, a power factor correction (PFC) circuit, but a rectifier having no power factor improvement function may be adopted.

The inverter 220 converts the DC power received from the AC / DC converter 210 into transmission power having a predetermined frequency. The inverter 220 can change the frequency of the transmitted power by changing the switching frequency according to the control signal from the power transmission ECU 250. In this example, the inverter 220 can change the frequency of the transmitted power in the range of 79 kHz to 90 kHz. The transmitted power generated by the inverter 220 is supplied to the transmission unit 240 through the filter circuit 230. The inverter 220 is configured to include, for example, a single-phase full bridge circuit.

The filter circuit 230 is provided between the inverter 220 and the power transmission unit 240, and suppresses harmonic noise generated from the inverter 220. In this example, the filter circuit 230 is composed of a secondary LC filter including an inductor 232 and a capacitor 234, but the configuration of the filter circuit 230 is not limited to this.

The power transmission unit 240 includes a coil 242 and a capacitor 244. The capacitor 244 is connected in series with the coil 242 to form a resonant circuit with the coil 242. The power transmission unit 240 receives the power transmission power (AC power) generated by the inverter 220 from the inverter 220 through the filter circuit 230, and passes through the magnetic field generated around the power transmission unit 240 to the power reception unit 110 of the power receiving device 100 in a non-contact manner. To transmit electricity. The Q value indicating the resonance strength of the formed resonance circuit is preferably 100 or more.

The power transmission ECU 250 includes a CPU (Central Processing Unit), a memory, an input / output buffer, and the like (none of them are shown), and controls various devices in the power transmission device 200. For example, the power transmission ECU 250 performs switching control of the inverter 220 so that the inverter 220 generates the power transmission power having a predetermined frequency when the power transmission from the power transmission device 200 to the power reception device 100 is executed. Various controls are not limited to software processing, but can also be processed by dedicated hardware (electronic circuits).

The communication unit 260 is configured to wirelessly communicate with the communication unit 170 of the power receiving device 100. The communication unit 260 exchanges information regarding the start / stop of power transmission with the power receiving device 100, and receives the power receiving status (received voltage, received current, received power, etc.) of the power receiving device 100 from the power receiving device 100.

The power receiving device 100 includes a power receiving unit 110, a filter circuit 120, a rectifying unit 130, a capacitor 140, a relay circuit 150, a charging ECU 160, and a communication unit 170.

The power receiving unit 110 includes a coil 112 and a capacitor 114. The capacitor 114 is connected in series with the coil 112 to form a resonant circuit with the coil 112. The power receiving unit 110 receives electric power (alternating current) output from the power transmitting unit 240 of the power transmitting device 200 in a non-contact manner through a magnetic field. The Q value of the resonance circuit formed by including the coil 112 and the capacitor 114 is also preferably 100 or more.

The filter circuit 120 is provided between the power receiving unit 110 and the rectifying unit 130, and suppresses harmonic noise generated when power is received by the power receiving unit 110. In this example, the filter circuit 120 is composed of a tertiary LC filter including capacitors 122 and 126 and an inductor 124, but the configuration of the filter circuit 120 is not limited to this.

The rectifying unit 130 rectifies the AC power received by the power receiving unit 110 and outputs it to the power storage device 300. The rectifying unit 130 includes, for example, a diode bridge circuit including four diodes. The capacitor 140 is provided on the output side of the rectifying unit 130 and smoothes the output voltage of the rectifying unit 130. The relay circuit 150 is provided between the capacitor 140 and the power storage device 300, and is turned on (conducting state) when the power storage device 300 is charged by the power received by the power receiving unit 110.

The charging ECU 160 includes a CPU, a memory, an input / output buffer, and the like (none of them are shown), and controls various devices in the power receiving device 100. Various controls are not limited to software processing, but can also be processed by dedicated hardware (electronic circuits).

The communication unit 170 is configured to wirelessly communicate with the communication unit 260 of the power transmission device 200. The communication unit 170 exchanges information regarding the start / stop of power transmission with the power transmission device 200, and transmits the power reception status (power reception voltage, power reception current, power reception power, etc.) of the power reception device 100 to the power transmission device 200.

The power storage device 300 is a power storage element configured to be chargeable and dischargeable. The power storage device 300 includes, for example, a secondary battery such as a lithium ion battery or a nickel hydrogen battery, and a power storage element such as an electric double layer capacitor. The lithium ion secondary battery is a secondary battery using lithium as a charge carrier, and may include a so-called all-solid-state battery using a solid electrolyte as well as a general lithium ion secondary battery having a liquid electrolyte.

In this non-contact power transmission system, in the power transmission device 200, AC power having a predetermined frequency is supplied from the inverter 220 to the power transmission unit 240 through the filter circuit 230. When AC power is supplied to the power transmission unit 240, energy (electric power) is transferred from the coil 242 to the coil 112 through a magnetic field formed between the coil 242 of the power transmission unit 240 and the coil 112 of the power reception unit 110. The energy (electric power) transferred to the power receiving unit 110 is supplied to the power storage device 300 through the filter circuit 120 and the rectifying unit 130.

The circuit configuration in which the capacitor 244 is connected in series with the coil 242 in the power transmission unit 240 and the capacitor 114 is connected in series with the coil 112 in the power receiving unit 110 is an SS system (primary series secondary series system). Also called.

Although not particularly shown, the structure of the coils 242 and 112 is not particularly limited. For example, when the power transmission unit 240 and the power reception unit 110 face each other, a spiral or spiral coil wound around an axis along the direction in which the power transmission unit 240 and the power reception unit 110 are aligned is provided in each of the coils 242 and 112. Can be adopted. Alternatively, when the power transmission unit 240 and the power reception unit 110 face each other, each of the coils 242 and 112 is formed by winding an electric wire around a ferrite plate whose normal direction is the direction in which the power transmission unit 240 and the power reception unit 110 are arranged. May be adopted for.

<Resonance frequency setting>
When the vehicle height of the vehicle on which the power receiving device 100 is mounted changes depending on the load or the like, the distance between the coil 112 of the power receiving unit 110 and the coil 242 of the power transmitting unit 240 (hereinafter referred to as “coil-to-coil distance”) changes. Then, the coupling coefficient between the coils 112 and 242 changes. Specifically, the larger the distance between the coils (the higher the vehicle height), the smaller the coupling coefficient.

In order to increase the power transmission efficiency from the coil 242 to the coil 112 (hereinafter referred to as "coil-to-coil efficiency") when the coupling coefficient is small, the impedance can be adjusted by providing a capacity switching mechanism in the power transmission unit 240 and the power reception unit 110. It is also conceivable to increase the efficiency between coils. However, such a capacity switching mechanism causes an increase in the physique of the power transmission unit 240 and the power reception unit 110, and also increases the cost.

Further, in order to improve the efficiency of the system as a whole, it is necessary to improve the power factor of power transmission as well as the efficiency between coils.

Therefore, in the present embodiment, a method for ensuring high power transmission efficiency and high power factor without providing a capacity switching mechanism in the power transmission unit 240 and the power reception unit 110 is shown. Specifically, as described below, when the distance between the coils is large (the vehicle height is high) and the coupling coefficient is small, the resonance frequency f1 of the resonance circuit of the power transmission device 200 and the resonance of the resonance circuit of the power receiving device 100 Each resonance circuit is designed so that the frequency f2 is included in the frequency adjustment range (79 kHz to 90 kHz) of the power transmitted by the inverter 220 and is closer to the upper limit than the lower limit of the frequency adjustment range. This makes it possible to secure high intercoil efficiency and high power factor. Hereinafter, it will be described in detail.

As described above, when the distance between the coils changes with the change in vehicle height, the coupling coefficient between the coils 112 and 242 changes. Then, when the coupling coefficient changes, the inductance of the coils 112 and 242 changes, and the resonance frequency of the resonance circuit changes due to the change in the inductance.

FIG. 2 is a diagram showing that the inductance of the coils 112 and 242 changes according to the coupling coefficient between the coils 112 and 242. In FIG. 2, the horizontal axis shows the coupling coefficient between the coils 112 and 242. The vertical axis shows the rate of change of the inductance according to the coupling coefficient with respect to the coils 112 and 242 whose inductances are equal to each other when the coupling coefficient is small, with reference to the inductance when the coupling coefficient is small. The inductance is measured using an impedance analyzer or an LCR meter by a method based on the measurement method specified in JIS C5321.

With reference to FIG. 2, L1 indicates the inductance of the coil 242 of the power transmission unit 240, and L2 indicates the inductance of the coil 112 of the power reception unit 110. As the coupling coefficient increases, the inductance L1 decreases and the inductance L2 increases.

It is as follows that the inductances L1 and L2 show such a change depending on the coupling coefficient. When the coupling coefficient is large, the distance between the coils is small, so that the coil 242 of the power transmission unit 240 is affected by the metal body on the lower surface of the vehicle body, and the leakage inductance becomes large. As a result, when the coupling coefficient is large, the inductance L1 of the coil 242 is lower than when the coupling coefficient is small. On the other hand, in the coil 112 of the power receiving unit 110, the inductance L2 increases when the coupling coefficient is large due to the influence of the coil 242 as compared with the case where the coupling coefficient is small.

By changing the inductance according to the coupling coefficient in this way, the resonance frequency of each resonant circuit changes according to the coupling coefficient.

FIG. 3 is a diagram showing that the resonance frequency changes according to the coupling coefficient between the coils 112 and 242. In FIG. 3, the capacitances of the capacitors 244 and 234 of the power transmission device 200 and the capacitors 114 and 122 of the power receiving device 100 are constant (not variable capacitors). In FIG. 3, the horizontal axis shows the coupling coefficient, and the vertical axis shows the resonance frequency of the resonance circuit. The frequencies fU and fL indicate the upper limit and the lower limit of the frequency adjustment range of the transmitted power, respectively. That is, the frequency f of the transmitted power can be adjusted in the range from the lower limit fL to the upper limit fU by the inverter 220. In this example, the lower limit fL and the upper limit fU are 79 kHz and 90 kHz, respectively.

With reference to FIG. 3, f1 indicates the resonance frequency of the resonance circuit of the power transmission device 200, and f2 indicates the resonance frequency of the resonance circuit of the power receiving device 100. As the coupling coefficient increases, the resonance frequency f1 increases and the resonance frequency f2 decreases.

It can be understood from the calculation formula of the resonance frequency that the resonance frequencies f1 and f2 show such a change depending on the coupling coefficient. Assuming that the capacitances of the capacitors 244 and 234 of the power transmission device 200 are C1 and C11 and the capacitances of the capacitors 114 and 122 of the power receiving device 100 are C2 and C21, respectively, the resonance frequencies f1 and f2 are expressed by the following equations, respectively.

f1 = 1 / 2π × √ ((C1 + C11) / (L1 × C1 × C11))… (1)
f2 = 1 / 2π × √ ((C2 + C21) / (L2 × C2 × C21))… (2)
As described with reference to FIG. 2, as the coupling coefficient increases, the inductance L1 decreases and the inductance L2 increases. Therefore, from the equations (1) and (2), it can be seen that as the coupling coefficient increases, the resonance frequency f1 increases as the inductance L1 decreases, and the resonance frequency f2 decreases as the inductance L2 increases.

Here, the relationship between the resonance frequency and the frequency f of the transmitted power adjusted by the inverter 220 will also be described. By bringing the frequency f of the transmitted power closer to the resonance frequency f2, the efficiency between the coils can be improved. The coil-to-coil efficiency η is expressed by the following equation.

ω is an angular frequency and satisfies the relationship of ω = 2πf. Lm is the mutual inductance of the coils 112 and 242, and RL is the impedance after the power receiving unit 110. Further, r1 is the resistance value of the coil 242, and r2 is the resistance value of the coil 112.

From the equation (3), when ωL2 = 1 / ωC2, that is, when ω = √ (1 / (L2 × C2)), the intercoil efficiency η becomes maximum. The frequency f0 corresponding to this angular frequency ω does not exactly match the resonance frequency f2 represented by the equation (2), but the difference is small, and by bringing the frequency f of the transmitted power closer to the resonance frequency f2, the coil. The inter-efficiency η can be increased.

Then, in the non-contact power transmission system according to this embodiment, as shown in FIG. 3, the resonance frequencies f1 and f2 are included in the adjustment range of the frequency f (lower limit fL to upper limit fU) in the region where the coupling coefficient is small. Moreover, the circuit constants in the equations (1) and (2) are designed so as to be closer to the upper limit fU than the lower limit fL. This makes it possible to secure high intercoil efficiency and high power factor when the coupling coefficient is small (the reason will be described later).

Further, since the range of the coupling coefficient until the resonance frequency f2, which decreases as the coupling coefficient increases, reaches the lower limit fL of the frequency adjustment range can be increased (range B in FIG. 3), even when the coupling coefficient is large. (Up to KB), the frequency f of the transmitted power can be adjusted to the resonance frequency f2 by the inverter 220, and the efficiency between the coils can be improved. Hereinafter, it will be described in more detail with reference to FIGS. 4 to 8.

FIG. 4 is a diagram showing the relationship between the resonance frequency f1 and the intercoil efficiency. In FIG. 4, the received power is constant, and the inter-coil efficiency when the resonance frequency f1 is variable while the resonance frequencies f1 and f2 are equivalent to each other in the adjustment range of the frequency f of the transmitted power is shown. ..

With reference to FIG. 4, k1 shows the coupling coefficient in the region where the coupling coefficient is small, and the line indicated by k1 shows the transition when the coupling coefficient is k1. On the other hand, k2 indicates the coupling coefficient in the region where the coupling coefficient is large, and the line indicated by k2 indicates the transition when the coupling coefficient is k2.

When the coupling coefficient is small (k1), the higher the resonance frequency f1, the higher the intercoil efficiency. When the coupling coefficient is large (k2), the efficiency between the coils is high and the change is small with respect to the resonance frequency f1 in the entire adjustment range of the frequency f of the transmitted power.

The reason why the inter-coil efficiency is lower when the coupling coefficient is smaller (k1) than when the coupling coefficient is larger (k2) is that the inter-coil efficiency η decreases when the mutual inductance Lm becomes smaller in the equation (3). You can also see from. Further, the higher the resonance frequency f1, the higher the inter-coil efficiency. The reason why the inter-coil efficiency is improved by adjusting the transmission power frequency f to the resonance frequencies f1 and f2 by the inverter 220, the resonance in the equation (3). It can also be seen from the fact that the inter-coil efficiency η increases as the angular frequency ω (proportional to the frequency f) increases according to the frequencies f1 and f2.

As described above, in the region where the coupling coefficient is small, the higher the resonance frequency f1, the higher the intercoil efficiency.

FIG. 5 is a diagram showing the relationship between the resonance frequency f1 and the power factor. Also in FIG. 5, the received power is constant, and the power factor when the resonance frequency f1 is variable while the resonance frequencies f1 and f2 are equivalent to each other in the adjustment range of the frequency f of the transmitted power is shown.

With reference to FIG. 5, when the coupling coefficient is small (k1), the higher the resonance frequency f1, the higher the power factor as well as the intercoil efficiency. When the coupling coefficient is large (k2), the power factor tends to decrease as the resonance frequency f1 increases, but the power factor is higher than when the coupling coefficient is small (k1).

When the coupling coefficient is small (k1), the higher the resonance frequency f1, the higher the power factor is for the following reasons. When the transmission device 200 includes the filter circuit 230, when the resonance frequency f1 is high, the frequency f is also increased in order to match the frequency f of the transmission power with the resonance frequency f1 by the inverter 220, so that the impedance of the filter circuit 230 is large. Become. Therefore, the duty of the inverter output voltage is increased in order to secure the desired power, and as a result, the power factor is improved.

As described above, in the region where the coupling coefficient is small, the higher the resonance frequency f1, the higher the power factor.
FIG. 6 is a diagram showing the relationship between the resonance frequency f1 and the frequency f of the transmitted power adjusted by the inverter 220 when the desired received power is secured in the power receiving device 100. Also in FIG. 6, the received power is constant, and the frequency f when the resonance frequencies f1 are variable while the resonance frequencies f1 and f2 are equivalent to each other in the adjustment range of the frequency f is shown.

With reference to FIG. 6, when the coupling coefficient is small (k1) and the resonance frequency f1 is low, the frequency f of the transmitted power is increased in order to secure the received power. When the frequency f of the transmitted power is increased, the power factor is improved, so that the transmitted power becomes large, and as a result, the received power is secured. However, in this case, since the frequency f of the transmitted power deviates from the resonance frequency f2 and the resonance frequency f1 is also low, the efficiency between the coils is poor (FIG. 4) and the power factor is also poor (FIG. 5).

As the resonance frequency f1 becomes higher, the efficiency between the coils and the power factor are improved (FIGS. 4 and 5), so that the deviation between the frequency f for securing the received power and the resonance frequency f1 becomes smaller. Further, since the dissociation between the frequency f and the resonance frequency f2 is also small, the efficiency between the coils is improved in this respect as well.

As described above, when the coupling coefficient is small and the resonance frequencies f1 and f2 are high, the efficiency between the coils and the power factor can be increased. Therefore, in the non-contact power transmission system according to this embodiment, the resonance frequencies f1 and f2 are closer to the upper limit fU than the lower limit fL of the frequency adjustment range in the region where the distance between the coils is large (the region where the coupling coefficient is small). , Resonance circuit is designed. As a result, even if the distance between the coils is large (even if the coupling coefficient is small), high efficiency between the coils and a high power factor can be ensured.

Then, referring to FIG. 3 again, according to the above configuration, the range of the coupling coefficient until the resonance frequency f2 reaches the lower limit fL of the frequency adjustment range can be increased (range B), so that the coupling coefficient becomes Even if it is large, the frequency f of the transmitted power can be adjusted to the resonance frequency f2 by the inverter 220 to improve the efficiency between the coils.

As a reference example, FIG. 7 is a diagram showing a resonance frequency corresponding to the coupling coefficient when the resonance frequencies f1 and f2 are matched within the frequency adjustment range when the coupling coefficient between the coils 112 and 242 is large. Also in FIG. 7, the capacitances of the capacitors 244 and 234 of the power transmission device 200 and the capacitors 114 and 122 of the power receiving device 100 are constant (not variable capacitors).

With reference to FIG. 7, in this reference example, since both the resonance frequencies f1 and f2 are out of the adjustment range of the frequency f of the transmission power by the inverter 220 in the region where the coupling coefficient is small, the frequency f is set to the resonance frequency. It is not possible to make adjustments to match f1 and f2. In particular, in a region where the coupling coefficient is small, the deviation between the frequency f and the resonance frequency f2 is large, and the efficiency between the coils may be significantly deteriorated.

FIG. 8 is a diagram showing the relationship between the coupling coefficient between the coils 112 and 242 and the efficiency between the coils. With reference to FIG. 8, in the line shown by S1, the resonance circuit is designed so that the resonance frequencies f1 and f2 are closer to the upper limit fU than the lower limit fL in the region where the coupling coefficient is small, as shown in FIG. The characteristics of the case are shown. On the other hand, the line shown by S2 shows the characteristics when the resonance circuit is designed so that the resonance frequencies f1 and f2 match within the frequency adjustment range when the coupling coefficient is large, as shown in FIG. 7 as a reference example. show.

In S2 corresponding to the reference example of FIG. 7, as described with reference to FIG. 7, the efficiency between the coils is significantly reduced when the coupling coefficient is small. On the other hand, S1 corresponding to this embodiment can secure high intercoil efficiency in a region where the coupling coefficient is small. Further, even in a region where the coupling coefficient is large, the frequency f of the transmitted power can be adjusted to the resonance frequency f2 by the inverter 220, so that the decrease in the efficiency between the coils can be suppressed.

As described above, in this embodiment, the resonance frequency f1 of the resonance circuit of the power transmission device 200 and the resonance frequency f2 of the resonance circuit of the power receiving device 100 are set in the region where the distance between the coils is large (the region where the coupling coefficient is small). It is closer to the upper limit fU than the lower limit fL of the frequency adjustment range of the transmitted power by the inverter 220. That is, in this embodiment, each resonance circuit is designed so that the resonance frequencies f1 and f2 have high values within the frequency adjustment range when the coupling coefficient is small. As a result, even if the distance between the coils is large (even if the coupling coefficient is small), the power factor can be increased while ensuring high power transmission efficiency.

Further, in this embodiment, the frequency f of the transmitted power can be adjusted to the resonance frequency f2 by the inverter 220 even in the region where the distance between the coils is small (the region where the coupling coefficient is large). That is, according to this embodiment, the frequency f of the transmitted power can be adjusted to the resonance frequency f2 by the inverter 220 in a wide range of coil-to-coil distances (that is, in a wide-range coupling coefficient), and the coil-to-coil efficiency is ensured. be able to.

In the above embodiment, the circuit configuration of the power transmission unit 240 and the power reception unit 110 is assumed to be an SS system (primary series / secondary series system), but the scope of the present disclosure is applied to the SS system. The method is not limited, and other methods may be used.

FIG. 9 is an overall configuration diagram of a non-contact power transmission system according to another embodiment. In FIG. 9, as an example, a non-contact power transmission system in which the circuit configurations of the power transmission unit and the power reception unit are SP system (primary series secondary parallel system) is shown.

With reference to FIG. 9, this non-contact power transmission system includes a power receiving device 100A instead of the power receiving device 100 in the system configuration shown in FIG. In the power receiving device 100 shown in FIG. 1, the power receiving device 100A includes a power receiving unit 110A and a filter circuit 120A, respectively, in place of the power receiving unit 110 and the filter circuit 120.

The power receiving unit 110A includes a coil 112 and a capacitor 116. The capacitor 116 is connected in parallel to the coil 112 to form a resonant circuit with the coil 112. The Q value of the resonance circuit formed by including the coil 112 and the capacitor 116 is also preferably 100 or more. The filter circuit 120A is composed of a secondary LC filter including an inductor 124 and a capacitor 126.

In the case of such an SP type circuit configuration, assuming that the capacitance of the capacitor 116 of the power receiving device 100A is C2, the resonance frequency f2 of the resonance circuit of the power receiving device 100A is expressed by the following equation.

f2 = 1 / 2π × √ (1 / (L2 × C2)-(C2 × RL) ² )… (4)
L2 is the inductance of the coil 112, and RL is the impedance after the power receiving unit 110A. The resonance frequency f1 of the resonance circuit of the power transmission device 200 is represented by the above equation (1).

Although the calculation formula of the resonance frequency f2 of the SP method is different from that of the SS method, the characteristics shown in FIGS. 2 to 8 described above also appear in the non-contact power transmission system adopting the SP method. Therefore, even in a non-contact power transmission system that employs the SP method or other method, it is possible to secure high power transmission efficiency and high power factor by designing a resonance circuit in the same manner as in the case of the SS method described above. can.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present invention is shown by the scope of claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

100 Power receiving device, 110, 110A Power receiving unit, 112, 124, 232, 242 coil, 114, 116, 122, 126, 140, 234, 244 capacitor, 120, 120A, 230 filter circuit, 130 rectifying unit, 150 relay circuit, 160 charging ECU, 170, 260 communication unit, 200 power transmission device, 210 AC / DC converter, 220 inverter, 240 power transmission unit, 250 power transmission ECU, 300 power storage device, 400 AC power supply.

Claims (1)

A non-contact power transmission system that transmits power from a power transmission device to a power receiving device in a non-contact manner.
The power transmission device
A first resonant circuit including a first coil for non-contact power transmission to the power receiving device, and a first resonant circuit.
An inverter configured to generate AC power transmission and supply it to the first resonant circuit.
A filter circuit provided between the inverter and the first resonance circuit is provided.
The inverter can adjust the frequency of the transmitted power within a predetermined frequency adjustment range.
The power receiving device includes a second resonant circuit configured to include a second coil for receiving power from the first resonant circuit in a non-contact manner.
The resonance frequency of the first resonant circuit and the second resonant circuit in the second region where the distance between the first coil and the second coil is larger than that of the first region where the distance is small. The resonance frequency of the non-contact power transmission system is included in the frequency adjustment range and is closer to the upper limit than the lower limit of the frequency adjustment range.

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