JP6959168B2 - Power transmission device - Google Patents

Description

The present invention relates to a power transmission device.

In recent years, a power transmission device capable of supplying power without using a cable has attracted attention.

For example, in the method using magnetic field resonance (magnetic field resonance coupling method), power can be supplied from a distance as long as the distance is about several meters. The magnetic field resonance coupling type power transmission device can be applied to, for example, charging of an electric vehicle.

In the magnetic field resonance coupling method, the resonance of the circuit is used. Therefore, the mutual inductance between these coils changes depending on the positional relationship between the power transmitting side coil and the power receiving side coil. The larger the value of the mutual inductance, the larger the coupling coefficient indicating the degree of coupling between the power transmitting side coil and the power receiving side coil. In the magnetic field resonance coupling method, it is necessary to increase the coupling coefficient for efficient power transmission.

For example, in Patent Document 1, the position where the coupling coefficient becomes the maximum and the current (induced current) flowing through the power receiving side coil becomes the maximum is detected by using a magnetic sensor, an optical sensor, a CCD camera, or the like.

Japanese Unexamined Patent Publication No. 8-33112

However, in a state where the power transmitting side coil and the power receiving side coil are not coupled (that is, a state in which the positional relationship between the two coils is displaced to the extent that power transmission cannot be performed), no current flows through the power receiving side coil. Therefore, the technique described in Patent Document 1 for detecting the position of the power receiving side coil that maximizes the current flowing through the power receiving side coil cannot be used in a state where the power transmitting side coil and the power receiving side coil are not coupled. Further, if a voltage having a resonance frequency is applied to the power transmission side coil in a state where the power transmission side coil and the power reception side coil are not coupled, a large resonance current may flow through the power transmission side coil.

An object of the present invention made in view of such circumstances is to provide a power transmission device capable of power transmission according to a coupling state of a power transmitting side coil and a power receiving side coil without requiring information from the power receiving side. be.

In order to solve the above problems, the power transmission device according to the embodiment of the present invention is parallel to the output of the DC voltage conversion unit and the DC voltage conversion unit that converts the output of the DC power supply to output the first DC power. It has a first capacitor connected to, an inverter unit that converts the first DC power into AC power, a second capacitor, and a first coil, and the AC power is supplied from the inverter unit. A second resonance circuit having a first resonance circuit, a third capacitor, and a second coil, which are magnetically coupled to the first resonance circuit to receive the AC power from the first resonance circuit. The resonance circuit, the rectifying unit that converts the AC power supplied from the second resonance circuit into the second DC power and supplies it to the load, and the current detection that detects the current flowing through the first resonance circuit. A device and a control unit that outputs a voltage command to the DC voltage conversion unit based on the current detected by the current detector are provided, and the control unit obtains an effective value of the current detected by the current detector. The effective value calculation unit to be calculated, and the correspondence relationship between the effective value and the voltage of the first DC power that changes according to the mutual inductance of the first coil and the second coil are stored, and the first The mutual inductance characteristic table that defines the current command, which is the effective value with respect to the reference value of the voltage in the correspondence relationship of the mutual inductance indicating the limit of coupling between the resonance circuit 1 and the second resonance circuit, and the effective value calculation. The voltage command calculation unit that calculates the original voltage command so that the effective value from the unit matches the current command, and the voltage limit value are set to the reference value or the maximum voltage that can be output by the DC voltage conversion unit. A voltage limit switching unit and a voltage command limit unit that limits the original voltage command with the voltage limit value and outputs the voltage command are provided, and whether or not the voltage command reaches the voltage limit value. Based on this, the coupling state of the first resonance circuit and the second resonance circuit is determined.

Further, in order to solve the above problems, in the power transmission device according to the embodiment of the present invention, the DC voltage conversion is performed so that the control unit suppresses the current when the coupling state is determined to be uncoupled. A voltage command to the unit may be output.

Further, in order to solve the above problems, in the power transmission device according to the embodiment of the present invention, when the control unit determines that the coupling state is coupling, the AC power output by the inverter unit is maximized. May output a voltage command to the DC voltage converter.

Further, in order to solve the above problems, in the power transmission device according to the embodiment of the present invention, when the control unit determines that the coupled state is uncoupled, a new determination regarding the coupled state is made for a predetermined time. You may do it.

According to the embodiment of the present invention, it is possible to provide a power transmission device capable of power transmission according to the coupling state of the resonance circuits of the power transmission side and the power reception side without requiring information from the power reception side.

It is a block diagram which illustrates the electric power transmission apparatus which concerns on one Embodiment of this invention. It is a block diagram which illustrates the control part of the power transmission apparatus which concerns on one Embodiment of this invention. It is a figure which illustrates the characteristic of mutual inductance. It is a flowchart which illustrates the control method of the control part concerning the determination of the coupling state. It is another flowchart which illustrates the control method of the control part concerning the determination of the coupling state. It is still another flowchart which illustrates the control method of the control part concerning the determination of the coupling state. FIG. 5 is a flowchart illustrating a control method of a control unit in which FIGS. 4, 5 and 6 are combined. It is a figure which illustrates the time change such as mutual inductance.

(Configuration of power transmission device)
FIG. 1 is a block diagram of the power transmission device 1 according to the present embodiment.

The power transmission device 1 includes a DC power supply 11, a DC voltage conversion unit 12, a first capacitor 13, an inverter unit 14, a first resonance circuit 15 (transmission side resonance circuit), and a second resonance circuit 16. (Power receiving side resonance circuit), a rectifying unit 17, a load 19, a current detector 21, and a control unit 31 are provided. Further, as shown in FIG. 1, the power transmission device 1 may further include a voltage detector 131. The power transmission device 1 supplies the DC power from the rectifying unit 17 to the load 19. The load 19 is, for example, a secondary battery, but is not particularly limited. Further, as shown in FIG. 1, a smoothing capacitor 18 that smoothes the voltage from the rectifying unit 17 and outputs a DC voltage is connected to the power transmission device 1.

The DC power supply 11 supplies DC power. The DC power supply 11 is, for example, a secondary battery. The DC power supply 11 may be, for example, a lead storage battery. Further, the DC power supply 11 may be an alkaline secondary battery such as a nickel cadmium battery. Further, the DC power supply 11 may be a lithium secondary battery such as a lithium ion battery. Further, as an alternative example, the DC power supply 11 may be a primary battery.

The DC voltage conversion unit 12 receives the output of the DC power supply 11 (DC power from the DC power supply 11). Then, the DC voltage conversion unit 12 converts the output of the DC power supply 11 and outputs the first DC power. The DC voltage conversion unit 12 converts the voltage Vdc1 of the first DC power so that it becomes equal ^{to the voltage command Vdc1 * from the control unit 31.} The DC voltage conversion unit 12 may be composed of, for example, a step-down chopper circuit, a step-up chopper circuit, or a step-up / down chopper circuit.

The first capacitor 13 is connected in parallel to the output of the DC voltage converter 12. The voltage between the terminals of the first capacitor 13 is the voltage Vdc1.

The voltage detector 131 detects the voltage between terminals (voltage Vdc1) of the first capacitor 13 and outputs it to the control unit 31. The voltage detector 131 is, for example, a voltage sensor. As described above, the DC voltage conversion unit 12 converts the voltage Vdc1 so as to be equal to the ^{voltage command Vdc1 *.} In the following, it is assumed that the voltage Vdc1 and the voltage command Vdc1 ^{* are interchangeable.} For example, in the characteristics of mutual inductance between the first coil 152 and the second coil 162 (see FIG. 3), the voltage Vdc1 used as a parameter can be replaced with the ^{voltage command Vdc1 *.}

The inverter unit 14 converts the first DC power output by the DC voltage conversion unit 12 into AC power. In the present embodiment, the AC power converted by the inverter unit 14 has a square wave voltage shape. The AC power from the inverter unit 14 is supplied to the first resonance circuit 15. Here, the inverter unit 14 may be composed of, for example, a bridge circuit composed of a plurality of switching elements. The switching element is, for example, an insulated gate bipolar transistor (IGBT), but is not particularly limited.

The first resonant circuit 15 transmits AC power from the inverter unit 14. In the present embodiment, the first resonance circuit 15 performs wireless transmission by utilizing a resonance phenomenon using a magnetic field. The first resonance circuit 15 is a resonance circuit on the power transmission side, and has a second capacitor 151 and a first coil 152 (a coil on the power transmission side). The second capacitor 151 and the first coil 152 are connected in series. The terminal of the second capacitor 151, which is not connected to the first coil 152, is connected to the inverter unit 14. Further, the terminal of the first coil 152, which is not connected to the second capacitor 151, is connected to the inverter unit 14.

The second resonant circuit 16 receives the AC power wirelessly transmitted from the first resonant circuit 15. The second resonance circuit 16 is a resonance circuit on the power receiving side, and has a third capacitor 161 and a second coil 162 (power receiving side coil). The third capacitor 161 and the second coil 162 are connected in series. The terminal of the third capacitor 161 that is not connected to the second coil 162 is connected to the rectifying unit 17. Further, the terminal of the second coil 162, which is not connected to the third capacitor 161, is connected to the rectifying unit 17. The second coil 162 is magnetically coupled to the first coil 152, and wireless power transmission is performed from the first coil 152 to the second coil 162. Here, the first resonance circuit 15 and the second resonance circuit 16 are coupled (the coupling state is "coupling"), that is, the first coil 152 and the second coil 162 are coupled. It means that power transmission is possible. Further, the fact that the first resonance circuit 15 and the second resonance circuit 16 are not coupled (the coupled state is "uncoupled") means that power transmission is not possible.

The rectifying unit 17 rectifies the AC power supplied from the second resonant circuit 16 and converts it into the second DC power. The rectifying unit 17 supplies the second DC power to the load 19. The rectifying unit 17 may be composed of, for example, a diode rectifier, but is not particularly limited.

The current detector 21 detects the current Ip flowing through the first resonance circuit 15 and outputs it to the control unit 31. The current detector 21 is, for example, a current sensor.

The control unit 31 outputs a ^{voltage command Vdc1 *} to the DC voltage conversion unit 12 based on the current Ip detected by the current detector 21. Specifically, the control unit 31 calculates the ^{voltage command Vdc1 *} based on the current Ip, the mutual inductance M1 described later, and the voltage value K1 described later.

FIG. 2 is a block diagram of the control unit 31 of the power transmission device 1 according to the present embodiment.

The control unit 31 includes an effective value calculation unit 311, a mutual inductance characteristic table 312, a voltage command calculation unit 313, a voltage limit switching unit 314, and a voltage command limit unit 315.

The effective value calculation unit 311 calculates and outputs the current effective value Iprms, which is the effective value of the current Ip.

The mutual inductance characteristic table 312 stores data (mutual inductance characteristics) with the mutual inductance M, the voltage Vdc1, and the current Ip as parameters. Then, the mutual inductance characteristic table 312 calculates and outputs the ^{current command Ip *} based on the mutual inductance M1 and the voltage value K1.

The voltage command calculation unit 313 calculates the original voltage command Vdc1 ^** based on the current effective value Iprms and the current command Ip ^* . Here, the voltage command calculation unit 313 may calculate the original voltage command Vdc1 ^{** so that the current effective value Iprms matches the current command Ip *} , for example, using PI control.

The voltage limit switching unit 314 sets the voltage limit value Vlim. In the present embodiment, the voltage limit switching unit 314 switches between, for example, the voltage value K1 and Kmax, which is the maximum voltage that the DC voltage conversion unit 12 can output, and outputs the voltage limit value Vlim.

The voltage command limiting unit 315 limits the original voltage command Vdc1 ^** by the voltage limit value Vlim, and calculates the ^{voltage command Vdc1 *.} The voltage command limiting unit 315 outputs the calculated voltage command Vdc1 ^* to the DC voltage conversion unit 12.

FIG. 3 is a diagram showing the characteristics of mutual inductance. The characteristic curve shown in FIG. 3 shows the relationship between the voltage Vdc1 of the first DC power shown on the horizontal axis and the current effective value Iprms shown on the vertical axis according to the value of mutual inductance. The characteristic curve shown in FIG. 3 is determined by the combination of the first coil 152 and the second coil 162. The larger the mutual inductance, the greater the degree of coupling between the first coil 152 and the second coil 162. The “characteristic at the minimum mutual inductance” in FIG. 3 is a characteristic curve when the first coil 152 and the second coil 162 are completely separated from each other. Further, the “characteristic at maximum mutual inductance” in FIG. 3 is a characteristic curve when the first coil 152 and the second coil 162 are most strongly magnetically coupled. Further, the “characteristics at the time of mutual inductance M1” in FIG. 3 is a characteristic curve when the first coil 152 and the second coil 162 have a limit coupling degree (threshold coupling degree) capable of power transmission. Is. Further, the “characteristics at the time of mutual inductance M2” in FIG. 3 is an example of a characteristic curve when the first coil 152 and the second coil 162 are in an uncoupled state in which power transmission is not possible. Here, the fact that power transmission is possible means that wireless power transmission can be performed with practical transmission efficiency. The state in which power transmission is not possible means that wireless power transmission is not possible, or that wireless power transmission is possible but not practical transmission efficiency.

In the example of FIG. 3, when the mutual inductance is maximum from M1, the first coil 152 of the first resonant circuit 15 and the second coil 162 of the second resonant circuit 16 are "coupled". That is, power can be transmitted between the first resonant circuit 15 and the second resonant circuit 16. Further, in the example of FIG. 3, when the mutual inductance is from the minimum to less than M1, the first coil 152 of the first resonance circuit 15 and the second coil 162 of the second resonance circuit 16 are “uncoupled”. Is. That is, power cannot be transmitted between the first resonance circuit 15 and the second resonance circuit 16.

As shown in FIG. 3, as the mutual inductance decreases, the voltage Vdc1 corresponding to the same current effective value Iprms decreases. For example, when the mutual inductance decreases from M1 to M2, the voltage Vdc1 corresponding to Y1, which is one value of the current effective value Iprms, decreases from K1 to K2. That is, it is possible to grasp the change in the coupling state between the first resonance circuit 15 and the second resonance circuit 16 by the change in the voltage Vdc1 (or the change in the voltage command Vdc1 ^{*) with respect to one value of the current effective value Iprms.} .. Here, in the characteristic curve (indicating the limit of "coupling") that is the boundary between "coupled" or "uncoupled" between the first resonant circuit 15 and the second resonant circuit 16, the reference value of the voltage Vdc1 and the reference value. If the corresponding current effective value Imprms value is determined, the change in the coupling state can be grasped more easily.

In the example of FIG. 3, the characteristic curve showing the limit of coupling is "characteristic at mutual inductance M1". The reference value of the voltage Vdc1 is "K1". Further, the value of the current effective value Iprms corresponding to the reference value is “Y1”. For example, when the coupling state of the first resonant circuit 15 and the second resonant circuit 16 changes and the mutual inductance changes from M1 to M2, the value of the voltage Vdc1 corresponding to Y1 of the current effective value Iprms changes from K1 to K2. Changes to. Since the voltage Vdc1 of the control unit 31 is smaller than the reference value "K1", the mutual inductance is reduced and the coupling state between the first resonance circuit 15 and the second resonance circuit 16 is "uncoupled". It can be easily grasped that it became. Further, the current effective value Iprms and the voltage Vdc1 (or the voltage command Vdc1 ^* ) are information obtained only on the power transmission side. That is, in the above coupling determination, information from the power receiving side is not required.

Here, the control unit 31 has data showing the characteristic curve of FIG. 3 in the mutual inductance characteristic table 312. That is, the mutual inductance characteristic table 312 determines the correspondence between the voltage Vdc1 of the first DC power that changes according to the mutual inductance and the current effective value Iprms. As described above, the mutual inductance characteristic table 312 receives the mutual inductance M1 (a value for designating the characteristic curve indicating the coupling limit) and the voltage value K1. The mutual inductance characteristic table 312 outputs the value of the current effective value Iprms (Y1 in the example of FIG. 3) when the voltage Vdc1 of the characteristic curve having the mutual inductance is M1 is K1 as the current command Ip ^* .

(First control method)
FIG. 4 is a flowchart showing a control method (first control method) of the control unit 31 regarding determination of a coupling state between the first resonance circuit 15 and the second resonance circuit 16. The first control method is a control method executed when the first resonance circuit 15 and the second resonance circuit 16 change from the uncoupled state to the coupled state.

The control unit 31 sets the mutual inductance M1 (step S11). As described above, the mutual inductance M1 indicates the limit mutual inductance when the first resonance circuit 15 and the second resonance circuit 16 are coupled. The mutual inductance M1 is determined according to, for example, the material, wire diameter, winding method, structure, distance, positional relationship, etc. of the first coil 152 and the second coil 162. The control unit 31 calculates the mutual inductance M1 based on data such as the material, wire diameter, winding method, structure, distance, and positional relationship of the first coil 152 and the second coil 162, for example. Further, as another example, the control unit 31 may receive the mutual inductance M1 from the control device of the entire system including the power transmission device 1.

The control unit 31 sets the current command Ip ^* (step S12). Further, the control unit 31 sets the voltage limit value Vlim (step S13). The control unit 31 sets the current effective value Iprms and the corresponding voltage Vdc1 in the characteristic curve indicating the coupling limit as the current command Ip ^* and the voltage limit value Vlim, respectively. For example, in the example of FIG. 3, the characteristic curve showing the limit of coupling is "characteristic at mutual inductance M1". The value of the current effective value Iprms set as the current command Ip ^{* is “Y1”.} The voltage limit value Vlim is "K1".

Here, as shown in FIG. 2, the voltage limit value Vlim is selected from K1 or Kmax by the voltage limit switching unit 314. In the first control method, the voltage limit value Vlim is set to K1 by the voltage limit switching unit 314. Here, K1 has a voltage lower than Kmax, and is 100 [V] as an example. Further, Kmax is 600 [V] as an example.

The control unit 31 controls so that the current effective value Iprms ^{becomes equal to the current command Ip *} (step S14). That is, the control unit 31 raises the voltage command Vdc1 ^* (for example, changes from zero to K1 which is the voltage limit value Vlim) until ^{the current effective value Iprms becomes equal to the current command Ip *.}

When the voltage Vdc1 (or the voltage command Vdc1 ^* ) reaches the voltage limit value Vlim (Yes in step S15), the control unit 31 changes the coupling state between the first resonance circuit 15 and the second resonance circuit 16 to "Yes". It is determined that it is "combined" (step S16). The voltage Vdc1 has reached the voltage limit value Vlim without the current effective value Iprms being ^{equal to the current command Ip *.} Therefore, in the characteristic curve of the mutual inductance in the current coupling state, ^{the value of the voltage Vdc1 corresponding to the current command Ip *} (for example, Y1) is equal to or more than the voltage limit value Vlim (for example, K1). Therefore, it is determined that the coupling state between the first resonance circuit 15 and the second resonance circuit 16 is "coupling".

On the other hand, when the voltage Vdc1 (or the voltage command Vdc1 ^* ) does not reach the voltage limit value Vlim (No in step S15), the control unit 31 couples the first resonance circuit 15 and the second resonance circuit 16. It is determined that the state is "unbound" (step S17). That is, in the characteristic curve of the mutual inductance in the current coupling state, ^{the value of the voltage Vdc1 corresponding to the current command Ip *} (for example, Y1) is less than the voltage limit value Vlim (for example, K1). Therefore, it is determined that the coupling state of the first resonance circuit 15 and the second resonance circuit 16 is "uncoupled". Then, the control unit 31 returns to the process of step S14.

In this way, the control unit 31 is in a coupled state when the first resonant circuit 15 and the second resonant circuit 16 change from "uncoupled" to "coupled" by executing the first control method. Can be judged appropriately.

(Second control method)
FIG. 5 is a flowchart showing a control method (second control method) of the control unit 31 regarding determination of a coupling state between the first resonance circuit 15 and the second resonance circuit 16. The second control method is a control method executed after the first control method (after the coupling state of the first resonance circuit 15 and the second resonance circuit 16 is determined to be "coupling"). Is.

The control unit 31 changes the voltage limit value Vlim (step S21). Here, as shown in FIG. 2, the voltage limit value Vlim is selected from K1 or Kmax by the voltage limit switching unit 314. For example, the control unit 31 changes the voltage limit value Vlim from K1 (100 [V] as an example) to Kmax (600 [V] as an example).

The control unit 31 controls so that the current effective value Iprms ^{becomes equal to the current command Ip *} (step S22). That is, the control unit 31 raises the voltage command Vdc1 ^* (for example, changes from K1 to Kmax, which is the voltage limit value Vlim) until ^{the current effective value Iprms becomes equal to the current command Ip *.}

^{In this way, the control unit 31 raises the voltage command Vdc1 *} to the maximum value after it is determined that the coupling state is "coupling", so that the AC power output by the inverter unit 14 (power transmitted to the power receiving side). ) Is maximized. By executing the second control method, the control unit 31 can maximize the electric power transmitted between the first resonance circuit 15 and the second resonance circuit 16 in the coupled state. ..

(Third control method)
FIG. 6 is a flowchart showing a control method (third control method) of the control unit 31 regarding determination of a coupling state between the first resonance circuit 15 and the second resonance circuit 16. The third control method is a control method executed after the second control method. The third control method makes the change from the bound state to the unbound state detectable.

The control unit 31 sets the voltage limit lower limit value VlimL (step S31). The control unit 31 may set the voltage limit lower limit value VlimL to “K1”. Further, the control unit 31 may provide hysteresis to set the voltage limit lower limit value VlimL to a voltage value lower than “K1”.

The control unit 31 controls so that the current effective value Iprms ^{becomes equal to the current command Ip *} (step S32). That is, the control unit 31 lowers the voltage command Vdc1 ^{* until the current effective value Iprms becomes equal to the current command Ip *} (for example, changes from Kmax, which is the voltage limit value Vlim, to K1, which is the voltage limit lower limit value Vliml). ..

When the voltage Vdc1 (or the voltage command Vdc1 ^* ) reaches the voltage limit lower limit value VlimL (Yes in step S33), the control unit 31 changes the coupling state between the first resonance circuit 15 and the second resonance circuit 16. It is determined that the device is "unbound" (step S34). The current effective value Iprms is ^{not equal to the current command Ip *,} and the voltage Vdc1 has reached the voltage limit lower limit value VlimL. In the characteristic curve of the mutual inductance in the current coupling state, ^{the value of the voltage Vdc1 corresponding to the current command Ip *} (for example, Y1) is less than the voltage limit lower limit value VlimL (for example, K1). Therefore, it is determined that the coupling state of the first resonance circuit 15 and the second resonance circuit 16 is "uncoupled".

On the other hand, when the voltage Vdc1 (or the voltage command Vdc1 ^* ) does not reach the voltage limit lower limit value VlimL (No in step S33), the control unit 31 connects the first resonance circuit 15 and the second resonance circuit 16. It is determined that the bonding state is "bonding" (step S35). That is, in the characteristic curve of the mutual inductance in the current coupling state, ^{the value of the voltage Vdc1 corresponding to the current command Ip *} (for example, Y1) is equal to or higher than the voltage limit lower limit value VlimL (for example, K1). Therefore, it is determined that the coupling state between the first resonance circuit 15 and the second resonance circuit 16 is "coupling". Then, the control unit 31 returns to the process of step S32.

In this way, the control unit 31 is in a coupled state when the first resonant circuit 15 and the second resonant circuit 16 change from "coupled" to "uncoupled" by executing the third control method. Can be judged appropriately.

(Fourth control method)
The control unit 31 can individually execute each of the above-mentioned first to third control methods. Here, the control unit 31 may execute a plurality of the above-mentioned first to third control methods in combination. FIG. 7 is a flowchart showing one control method (fourth control method) in which the above-mentioned first to third control methods are combined.

The control unit 31 executes the processes of steps S11 to S17. Since steps S11 to S17 have the same contents as the processing of the same reference numerals in the first control method, description thereof will be omitted.

After step S16 (that is, after determining that the coupling state of the first resonance circuit 15 and the second resonance circuit 16 is "coupling"), the control unit 31 processes the steps S21 and S31 to S35. To execute. Since step S21 has the same contents as the processing of the same reference numerals in the second control method, the description thereof will be omitted. Further, since steps S31 to S35 have the same contents as the processing of the same reference numerals in the third control method, the description thereof will be omitted.

After step S17 or S34 (that is, after determining that the coupling state of the first resonant circuit 15 and the second resonant circuit 16 is "uncoupled"), the control unit 31 sets the current command Ip ^* to zero. (Step S41). Further, the control unit 31 sets the voltage Vdc1 to zero (step S42). Therefore, when the coupling state of the first resonance circuit 15 and the second resonance circuit 16 is "uncoupled", the current Ip flowing through the first coil 152 (transmission side coil) can be minimized.

The control unit 31 waits until a predetermined time elapses (No in step S43). That is, the control unit 31 does not execute a new determination of the coupling state for a predetermined time. When the predetermined time elapses (Yes in step S43), the control unit 31 returns to the process of step S11. The predetermined time may be set to a length in which the distance, positional relationship, etc. of the first coil 152 and the second coil 162 can be adjusted, for example. The predetermined time may be, for example, 10 seconds or 1 minute.

In this way, the control unit 31 can minimize the current Ip at the time of non-coupling in addition to the effects of the first to third control methods by executing the fourth control method.

FIG. 8 is a diagram illustrating a time change of the mutual inductance M and the like of the first coil 152 and the second coil 162 when the control unit 31 executes the fourth control method. In the example of FIG. 8, the control unit 31 determines that the coupling state is “coupling” because the voltage Vdc1 reaches the voltage limit value Vlim at time t1. Further, in the example of FIG. 8, the control unit 31 determines that the coupling state is “uncoupled” because the voltage Vdc1 reaches the voltage limit lower limit value VlimL at time t2.

As described above, the power transmission device 1 according to the present embodiment ^{sets the coupling state based on whether or not the voltage Vdc1 (or the voltage command Vdc1 *} ) reaches the voltage limit value Vlim (or the voltage limit lower limit value VlimL). judge. That is, the power transmission device 1 makes an appropriate "coupled" or "uncoupled" determination without requiring information from the power receiving side. Therefore, the power transmission device 1 can transmit power according to the coupling state of the power transmission side coil and the power reception side coil. Further, in the present embodiment, the power transmission device 1 can suppress the current Ip flowing through the first coil 152 (transmission side coil) when it is determined that the coupling state is "uncoupled". That is, when the power transmission device 1 determines that the coupling state is "uncoupled", the voltage command Vdc1 ^* is limited (for example, K1), or the voltage command Vdc1 ^{* is set} to zero. , Current Ip can be suppressed.

Although the present invention has been described based on the drawings and embodiments, it should be noted that those skilled in the art can easily make various modifications and modifications based on the present disclosure. Therefore, it should be noted that these modifications and modifications are within the scope of the present invention.

For example, in the above embodiment, the determination of the coupling state is executed by the entire control unit 31. Then, the information about the combined state is shared by each functional block constituting the control unit 31. Here, a specific functional block in the control unit 31 may execute the determination of the combined state. For example, the voltage command limiting unit 315 may determine the coupling state based on the comparison between the ^{voltage command Vdc1 * and the voltage limit value Vlim.} Then, the voltage command limiting unit 315 may generate a signal according to the coupling state, and the signal corresponding to the coupling state may be output to a functional block other than the voltage command limiting unit 315. For example, the voltage limit switching unit 314 may select the voltage limit value Vlim based on the signal according to the coupling state.

1 Power transmission device 11 DC power supply 12 DC voltage conversion unit 13 1st capacitor 14 Inverter unit 15 1st resonance circuit 16 2nd resonance circuit 17 Rectification unit 18 Smoothing capacitor 19 Load 21 Current detector 31 Control unit 131 Voltage detection Instrument 151 2nd capacitor 152 1st coil 161 3rd capacitor 162 2nd coil 311 Effective value calculation unit 312 Mutual inductance characteristic table 313 Voltage command calculation unit 314 Voltage limit switching unit 315 Voltage command limit unit

Claims (4)

A DC voltage converter that converts the output of the DC power supply and outputs the first DC power,
A first capacitor connected in parallel to the output of the DC voltage converter,
An inverter unit that converts the first DC power into AC power,
A first resonant circuit having a second capacitor and a first coil and to which the AC power is supplied from the inverter unit,
A second resonant circuit having a third capacitor and a second coil, which is magnetically coupled to the first resonant circuit and receives the AC power from the first resonant circuit.
A rectifying unit that converts the AC power supplied from the second resonant circuit into a second DC power and supplies it to the load.
A current detector that detects the current flowing through the first resonant circuit, and
A control unit that outputs a voltage command to the DC voltage conversion unit based on the current detected by the current detector is provided.
The control unit
An effective value calculation unit that calculates the effective value of the current detected by the current detector,
The correspondence between the voltage of the first DC power and the effective value, which changes according to the mutual inductance of the first coil and the second coil, is stored, and the first resonance circuit and the second resonance circuit are stored. A mutual inductance characteristic table that defines a current command that is an effective value with respect to a voltage reference value in the corresponding relationship of the mutual inductance indicating the limit of coupling with the resonance circuit of the above.
A voltage command calculation unit that calculates an original voltage command so that the effective value from the effective value calculation unit matches the current command.
A voltage limit switching unit that sets the voltage limit value to the reference value or the maximum voltage that can be output by the DC voltage converter.
A voltage command limiting unit that limits the original voltage command by the voltage limit value and outputs the voltage command is provided.
A power transmission device that determines a coupling state between the first resonance circuit and the second resonance circuit based on whether or not the voltage command reaches the voltage limit value. The control unit
The power transmission device according to claim 1, wherein a voltage command is output to the DC voltage conversion unit so as to suppress the current when the coupling state is determined to be non-coupling. The control unit
The power transmission device according to claim 1 or 2, which outputs a voltage command to the DC voltage conversion unit so that the AC power output by the inverter unit is maximized when the coupling state is determined to be coupling. .. The control unit
The power transmission device according to any one of claims 1 to 3, wherein when the combined state is determined to be uncoupled, a new determination regarding the combined state is not executed for a predetermined time.

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