JP2017093094A - Power reception device - Google Patents

Abstract

[PROBLEMS] To achieve both efficiency control and desired power control in wireless power transmission only on a power receiving side.
A power receiving device 20 according to the present invention is connected to a coil L ₂ that receives AC power from a power transmission side by wireless power transmission using a magnetic field or an electric field, and the AC voltage received by the coil L ₂ is converted into a DC voltage. A power converter 21 that rectifies, a power converter 22 that is connected to the power converter 21 and converts the DC voltage rectified by the power converter 21 into an arbitrary DC voltage or AC voltage, the power converter 21, and power Among the converters 22, a controller 24 that controls the power transmission efficiency with the power transmission side using one and controls the received power from the power transmission side with the other.
[Selection] Figure 2

Description

  The present invention relates to a power receiving apparatus in wireless power transmission.

  Wireless power transmission, in which power is transferred between a power transmission side and a power reception side by wireless power transmission using a magnetic field or an electric field, is being studied.

  As an application example of wireless power transmission, there is an electric vehicle (EV). When wireless power transmission is used for EVs, the power transmission side device (power transmission device) is installed under the road surface, the power reception side device (power reception device) is installed in the EV, and the cruising distance is improved by supplying power while the EV is running It becomes possible to make it. When power is supplied to a moving body such as an EV using wireless power transmission, wireless power transmission is performed according to changes in the coupling state of the coils on the power transmission side and the power reception side, and changes in the load status (power consumption, etc.) on the power reception side. It is preferable to control the power transmission efficiency and the received power on the power receiving side.

  Therefore, Non-Patent Document 1 discusses a technique for achieving both transmission efficiency control (efficiency control) and received power control (desired power control) through cooperation between the power transmission side and the power reception side. .

Toshiyuki Hiramatsu, Takaaki Huang, Masaki Kato, Takehiro Imura, Yoichi Hori, “Independent Control of Maximum Efficiency on Power Transmission Side and Desired Received Power on Power Receiving Side in Wireless Power Transfer”, IEEJ Transactions D, Vol. 135 No. 8 (2015)

  In the technology disclosed in Non-Patent Document 1, the power transmission side and the power reception side cooperate to achieve both efficiency control and desired power control. However, considering the application of wireless power transmission to EVs, it is preferable that both the efficiency control and the desired power control can be achieved only on the power receiving side.

  As shown in FIG. 3 of Non-Patent Document 1, in general, in the control only on the power receiving side, when one of the transmission efficiency and the power receiving power is determined, the other is also determined uniquely, and only on the power receiving side. A method for achieving both efficiency control and desired power control has not been established.

  An object of the present invention is to solve the above-described problems and provide a power receiving apparatus that can achieve both efficiency control and desired power control in wireless power transmission only on the power receiving side.

  In order to solve the above problems, a power receiving device according to the present invention is connected to a coil that receives AC power from a power transmission side by wireless power transmission using a magnetic field or an electric field, and rectifies the AC voltage received by the coil into a DC voltage. A first power converter that is connected to the first power converter and converts the DC voltage rectified by the first power converter into an arbitrary DC voltage or AC voltage. Power transmission efficiency between the power transmission side using one of the power transmitter and the first power converter and the second power converter, and receiving power from the power transmission side using the other And a controller for controlling electric power.

  In the power receiving device according to the present invention, the first power converter includes a first mode in which the coil is short-circuited so as to cut off the power received by the coil, and a second mode for rectifying the power received by the coil. The second power converter can control an input / output voltage ratio and an input / output current ratio, and the controller can input and output an input / output voltage ratio of the second power converter. The transmission efficiency is controlled by controlling the output current ratio, and the operation mode of the first power converter is switched between the first mode and the second mode so that desired received power can be obtained. It is preferable.

  In the power receiving device according to the present invention, the first power converter includes a first mode in which the coil is short-circuited so as to cut off the power received by the coil, and a second mode for rectifying the power received by the coil. The second power converter is capable of controlling an input / output voltage ratio and an input / output current ratio, and the controller sets an operation mode of the first power converter to the first power converter. The transmission efficiency is controlled by switching between the second mode and the second mode, and the input / output voltage ratio and the input / output current ratio of the second power converter are controlled so as to obtain a desired received power. It is preferable.

  In order to solve the above-described problem, a power receiving device according to the present invention is connected to a coil that receives AC power from a power transmission side by wireless power transmission using a magnetic field or an electric field, and the AC voltage received by the coil is converted into a DC voltage. And a controller that controls the transmission efficiency of power to and from the power transmission side and the received power from the power transmission side using the power converter.

  In the power receiving device according to the present invention, the power converter includes a first mode in which the coil is short-circuited so as to cut off the power received by the coil, and a second mode in which the power received by the coil is rectified. And the controller operates the power converter in the first mode at a frequency slower than a resonance frequency of a resonance circuit including the coil so as to obtain a desired received power, and the desired power receiving In a period other than a period in which the power converter is operated in the first mode in accordance with control for obtaining power, the operation mode of the power converter is changed to the first mode in synchronization with the resonance frequency. It is preferable to control the transmission efficiency with the power transmission side by switching between the second mode.

  The power receiving device according to the present invention preferably further includes a capacitor connected to the coil.

  According to the power receiving device of the present invention, it is possible to achieve both efficiency control and desired power control in wireless power transmission only on the power receiving side.

1 is a diagram illustrating a schematic configuration of a wireless power transmission system according to a first embodiment of the present invention. It is a figure which shows the structural example of the power receiving apparatus shown in FIG. FIG. 3 is a circuit diagram illustrating a configuration example of the power receiving device illustrated in FIG. 2. FIG. 4 is a circuit diagram illustrating another configuration example of the power receiving device illustrated in FIG. 2. It is a figure which shows the flow of the electric current in the power converter 22 shown in FIG. It is a figure for demonstrating the operation mode of the power converter 21 shown in FIG. It is a figure for demonstrating the operation example 1 of the power receiving apparatus shown in FIG. FIG. 4 is a diagram for describing an operation example 2 of the power receiving device illustrated in FIG. 3. It is a circuit diagram which shows the structural example of the power receiving apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the waveform of the output voltage of the power converter shown in FIG. It is a figure for demonstrating operation | movement of the power receiving apparatus shown in FIG. It is a figure which shows an example of the waveform of the control signal by the controller shown in FIG.

  Embodiments of the present invention will be described below.

(First embodiment)
First, an outline of the present invention will be described.

  FIG. 1 is a diagram showing an overview of a wireless power transmission system 1 according to the first embodiment of the present invention.

  A wireless power transmission system 1 shown in FIG. 1 receives power from a power transmission device 10 and transmits power to a load 23 using a magnetic field or an electric field in response to power supply from an AC power supply 11. And a power receiving device 20 to be supplied.

The power transmission device 10 is equivalently provided with a resonance circuit configured by connecting an internal resistance R ₁ , a capacitor C _1, and a coil L ₁ in series, and an AC power supply 11 is connected to the resonance circuit. . Note that the capacitor C ₁ is not an essential configuration, and even if only the coil L ₁ is used, power can be transmitted by wireless power transmission using a magnetic field or an electric field.

The power receiving device 20 is equivalently provided with a resonance circuit configured by connecting an internal resistance R ₂ , a capacitor C _2, and a coil L ₂ in series, and a load 23 is connected to the resonance circuit. Note that the capacitor C ₂ is not an essential component, and even the coil L ₂ alone can receive power by wireless power transmission using a magnetic field or an electric field. However, by providing the capacitor C ₂ , the efficiency can be further improved by resonance.

A power transmitting device 10 side of the coil L ₁ (primary coil) and the power receiving device 20 side of the coil L ₂ (the secondary coil) is against phase utilizing electromagnetic induction between the coil L ₁ and a coil L ₂ Power is exchanged.

The power transmission efficiency η in the wireless power transmission and the received power P ₂ of the power receiving device 20 are respectively obtained by the following equations (1) and (2) using circuit equations. L _m represents the mutual inductance between the coil L ₁ and the coil L ₂ , R _L represents the resistance value (load resistance value) of the load 23, ω ₀ represents the resonance angular frequency, and V ₁₀ represents the AC power source 11. The fundamental wave component of the output voltage V ₁ (AC voltage) is shown.

As can be seen from the equations (1) and (2), if the apparent load resistance value R _L is determined, the transmission efficiency η and the received power P ₂ are determined. The load resistance value R _L can be controlled by the received voltage (voltage V ₂ ) of the coil L ₂ .

  FIG. 2 is a diagram illustrating a configuration example of the wireless power transmission system 1. In FIG. 2, the resonance circuits of the power transmission device 10 and the power reception device 20 are shown as equivalent circuits.

  The power receiving device 20 illustrated in FIG. 2 includes power converters 21 and 22, a load 23, and a controller 24. The power converter 21 is a first power converter, and the power converter 22 is a second power converter.

In response to power supply from the AC power supply 11 provided in the power transmission device 10 to the coil L ₁ , power is transferred between the coil L ₁ and the coil L ₂ by electromagnetic induction (the coil L ₂ receives power). To do). The power converter 21 is an AC / DC converter, and rectifies (converts) the received voltage (voltage V ₂ ) of the coil L ₂ , which is an AC voltage, into a DC voltage. For example, a PWM (Pulse Width Modulation) converter can be used as the power converter 21.

  The power converter 22 is a DC / DC converter or a DC / AC converter, converts the DC voltage rectified by the power converter 21 into an arbitrary DC voltage or AC voltage, and outputs it to the load 23. Whether the power converter 22 is a DC / DC converter or a DC / AC converter depends on the type of the load 23. Further, when the power converter 22 is a DC / DC converter, a step-up converter, a step-down converter, a step-up / step-down converter, or the like can be used according to a necessary voltage.

  Examples of the load 23 include a battery, a motor, and a constant power load that are operated by DC power or AC power supplied from the power converter 22.

The controller 24 controls the operation of the power converters 21 and 22 and controls the transmission efficiency η and the received power P ₂ .

  FIG. 3 is a circuit diagram illustrating a configuration example of the wireless power transmission system 1. FIG. 3 shows an example in which the power converter 22 is configured by a DC / DC converter.

  First, the configuration of the power transmission device 10 will be described.

  A power transmission device 10 illustrated in FIG. 3 includes switches 111 to 114 configured by switching switching elements such as IGBTs (Insulated Gate Bipolar Transistors) and diodes in antiparallel connection, and a DC power supply 115. The switches 111 to 114 and the DC power supply 115 constitute the AC power supply 11.

  The switch 111 and the switch 112 are connected in series, and the switch 113 and the switch 114 are connected in series. A series body of the switch 111 and the switch 112 and a series body of the switch 113 and the switch 114 are connected in parallel to the DC power source 115. In addition, a connection point between the switch 111 and the switch 112 and a connection point between the switch 113 and the switch 114 are respectively connected to one end and the other end of the resonance circuit related to wireless power transmission of the power transmission device 10.

  Since the switches 111 to 114 are general inverters, a detailed description of the operation is omitted, but the DC power output from the DC power supply 115 is controlled by controlling the on / off of the switches 111 to 114. The electric power is converted into AC power and supplied to the resonance circuit of the power transmission device 10.

In response to the supply of AC power to the resonance circuit of the power transmission device 10, power is received by the coil L _{2 on the} power reception device 20 side and supplied to the power converter 21 by electromagnetic induction.

  Next, the configuration of the power converter 21 will be described.

  The power converter 21 illustrated in FIG. 3 includes switches 211 to 214 configured by connecting switching elements such as IGBTs and diodes in antiparallel.

The switches 211 and 212 are connected in series, and the switch 213 and the switch 214 are connected in series. A connection point between the switch 211 and the switch 212 and a connection point between the switch 213 and the switch 214 are respectively connected to one end and the other end of the resonance circuit of the power receiving device 20. The series body of the switch 211 and the switch 212 and the series body of the switch 213 and the switch 214 are connected in parallel to the smoothing capacitor _CDC .

Since the switches 211 to 214 are general converters (AC / DC converters), detailed description of the operation is omitted, but the on / off time width of each of the switches 211 to 214 is controlled. Thus, the voltage V ₂ that is an AC voltage can be rectified (converted) to a DC voltage. The DC voltage obtained by the power converter 21 is supplied to the power converter 22 via the capacitor _CD .

  Next, the configuration of the power converter 22 will be described.

The power converter 22 illustrated in FIG. 3 includes switches 221 and 222 configured by switching switching elements such as IGBTs and diodes in anti-parallel connection, an inductor L _load , an internal resistance R _load, and a capacitor C _load. .

The switch 221 and the switch 222 are connected in series, the connection point between the switch 221 and the switch 222, the internal resistance R _load of the inductor L _load and the inductor L _load is connected to one end of series body that are connected in series Yes. A capacitor C _load and a load 23 are connected in parallel to the other end of the series body of the inductor L _load and the internal resistance R _load .

Since the switches 221 and 222, the inductor L _load , the internal resistance R _load and the capacitor C _load are configured by a general converter (DC / DC converter), a detailed description of the operation thereof is omitted, but the switch 221 is omitted. on, by controlling the off voltage V _DC across the capacitor C _DC is converted into a DC voltage of any level, it is supplied to the load 23.

  Note that as described above, the load 23 may be operated by AC power, such as a motor. In this case, a DC / AC converter is used as the power converter 22. FIG. 4 is a diagram illustrating a configuration example of the power receiving device 20 when a DC / AC converter is used as the power converter 22.

  The power converter 22 illustrated in FIG. 4 includes switches 221 to 224 configured by connecting switching elements such as IGBTs and diodes in antiparallel.

The switch 221 and the switch 222 are connected in series, and the switch 223 and the switch 224 are connected in series. A series body of the switch 221 and the switch 222 and a series body of the switch 223 and the switch 224 are connected in parallel to the capacitor _CDC . The connection point between the switch 221 and the switch 222 and the connection point between the switch 223 and the switch 224 are connected to one end and the other end of the load 23, respectively.

Since the switches 221 to 224 are configured by a general inverter (DC / AC converter), a detailed description of the operation is omitted. However, by controlling the on / off of the switches 221 to 224, a direct current can be obtained. The voltage _VDC, which is a voltage, is converted into an AC voltage and supplied to the load 23.

  Next, the operation of the power receiving device 20 according to this embodiment will be described.

As described above, the controller 24 uses the power converter 21 and the power converter 22 to control the transmission efficiency η (efficiency control) and the received power P ₂ (desired power control). Here, in the present embodiment, the controller 24 performs efficiency control using the power converter 22 (so that the transmission efficiency η is maximized), and performs desired power control using the power converter 21 ( An operation (operation example 1) of obtaining a desired received voltage or an operation (operation example 2) of performing efficiency control using the power converter 21 and performing desired power control using the power converter 22 is performed. . Hereinafter, each of the operation examples 1 and 2 will be described. Hereinafter, the case where the power converter 22 is a DC / DC converter (FIG. 3) will be described as an example.

  First, the operation example 1 will be described.

As described above, the transmission efficiency η is given by Equation (1). From equation (1), it can be seen that the transmission efficiency η is determined if the load resistance value R _L is determined. Therefore, if the load resistance value R _L is optimized, the transmission efficiency η can be maximized. In the operation example 1, the load resistance value R _L is optimized by controlling the voltage _VDC by the power converter 22.

The voltage V _DC η _max that maximizes the transmission efficiency η can be expressed by the following equation (3) from the equation (1).

The controller 24 controls the power converter 22 so that the voltage V _DC becomes the voltage V _DC η _max . Specifically, the controller 24 controls the on / off of the switch 221 so that the voltage V _DC becomes the voltage V _DC η _max .

When the switch 221 is turned on and the switch 222 is turned off, current flows from the capacitor _CD to the inductor L _load and the load 23 as indicated by the solid line arrow in FIG. As a result, the voltage _VDC decreases. On the other hand, when the switch 221 is turned off and the switch 222 is turned on, a current flows through the load 23 only by the energy accumulated in the inductor L _load as shown by the solid line arrow in FIG. As a result, the voltage V _DC increases.

As described above, the case where the switch 221 is turned on and the switch 222 is turned off (FIG. 5A) and the case where the switch 221 is turned off and the switch 222 is turned on (FIG. 5B) are repeated. Therefore, the average values of the input current and the input voltage (voltage V _DC ) of the power converter 22 fluctuate, and therefore, if the output current and output voltage of the power converter 22 are constant, the switches 221 and 222 are turned on and off. By switching the input / output current ratio, the input / output current ratio and the input / output voltage ratio of the power converter 22, that is, the impedance of the power converter 22 can be controlled.

Then, the switch 221 is switched on and off, and the input / output current ratio and the input / output voltage ratio of the power converter 22 are controlled, so that the voltage V _DC can be the voltage V _DC η _max .

When the load resistance value R _L is determined (when control is performed so that the transmission efficiency η is maximized), the received power P ₂ is also uniquely determined from Equation (2). However, in the present embodiment, the desired received power P ₂ is obtained by controlling the operation of the power converter 21.

When the switches 211 and 213 are turned on, the coil L ₂ is short-circuited, and the positive half wave of the received current (current I ₂ ) of the coil L ₂ is represented by the switch 211, as indicated by the solid line arrow in FIG. It flows to the coil L ₂ side via 213. 6A, the negative half wave of the current I ₂ flows to the coil L ₂ side via the switches 213 and 211. That is, when the switches 211 and 213 are turned on, the coil L ₂ is short-circuited, the current I ₂ is circulated in the power converter 21, and power is not supplied to the rear stage side (the power converter 22 and the load 23).

On the other hand, when the switches 211 and 214 are turned off and the switches 212 and 213 are turned on, the positive half wave of the current I ₂ flows to the rear stage side via the switch 212 as shown by the solid line arrow in FIG. Then, it flows from the rear stage side to the coil L ₂ side via the switch 213. In addition, when the switches 211 and 214 are turned on and the switches 212 and 213 are turned off, the negative half wave of the current I ₂ is transferred to the rear stage side via the switch 214 as shown by a one-dot chain line arrow in FIG. The current flows from the rear stage side to the coil L ₂ side via the switch 211. That is, in the case of FIG. 6B and FIG. 6C, the current I ₂ is rectified and supplied to the subsequent stage side.

Hereinafter, as shown in FIG. 6A, the current I ₂ circulates in the power converter 21, and the operation mode in which power is not supplied to the rear stage side (power is cut off) is referred to as short mode (first mode). The operation mode in which the current I ₂ is rectified and supplied to the subsequent stage as shown in FIGS. 6B and 6C is referred to as a rectification mode (second mode). In this embodiment, by turning on the switch 211 and 213, a coil L ₂ is short-circuited, (the operation mode of the power converter 21 and short mode) in which power in the subsequent stage to not be supplied but is not limited to this, by turning on the switch 212, the coil L ₂ is short-circuited, it is possible to power on the rear stage side to not be supplied.

As described above, in the short mode, power supply to the subsequent stage is interrupted, and in the rectification mode, power is supplied to the subsequent stage. Therefore, the operation mode of the power converter 21 is switched between the short mode and the rectification mode, and the average (Duty ratio) between the period in which the short converter mode operates in the predetermined period and the period in which the rectifier mode operates (Duty ratio) The received power P ₂ can be controlled.

When the period operating in the short mode is T _s and the period operating in the rectification mode is T _r , the duty ratio D is expressed by the following equation (4).

_Assuming that the received power in the short mode is P _2s and the received power in the rectification mode is P _2r , P _2s = 0. _Therefore , the average received power is expressed by the following equation (5).

The transmission power P _{1s in the} short mode is very narrow, but it is a loss (P _1r >> P _1s ). Therefore, the average efficiency is expressed by the following formula (6).

FIG. 7 is a diagram showing temporal changes in voltage V ₂ , current I ₂ , load resistance R _L , received power P ₂ , transmission efficiency η, and desired power P _L ′.

The controller 24 switches the operation mode of the power converter 21 between the rectification mode and the short mode at a duty ratio D corresponding to the desired power P _L ′. Electric power is received in the period T _r , and no electric power is received in the period T _s . Therefore, by controlling the duty ratio D, the average value of the received power P ₂ can be set to the desired power P _L ′.

As shown in FIG. 7, the desired power P _L 'after time t1 is greater than the desired power P _L ' from time t0 to time t1. For this reason, the controller 24 makes the duty ratio D after time t1 larger than the duty ratio D from time t0 to time t1. In this way, it is possible to increase the average value of the reception power P ₂ after time t1.

Further, by controlling the voltage _VDC so that the transmission efficiency η is maximized (the load resistance value R _L is the optimum value R _opt ), the transmission efficiency η is increased to the maximum value η _max during the period _Tr . It can be. Therefore, both efficiency control and desired power control can be achieved.

  Next, the operation example 2 will be described.

As described above, the voltage V _DC η _max that maximizes the transmission efficiency η can be expressed as in Expression (3).

The controller 24 controls the power converter 21 so that the voltage V _DC is equal to the voltage V _DC η _max obtained by Expression (3). Specifically, the controller 24 controls the ratio (Duty ratio) between the period T _r and the period T _s so that the voltage V _DC becomes the voltage V _DC η _max .

As described above, power is not supplied to the subsequent stage of the power converter 21 in the short mode. Therefore, as shown in FIG. 8, in the period T _s , the voltage V _DC decreases due to the power supply from the capacitor C _DC to the load 23. On the other hand, in the rectification mode, power is supplied to the subsequent stage of the power converter 21. Accordingly, as shown in FIG. 8, in the period T _r, if the transmission power by a wireless power transmission is sufficient for the load power, the power stored in the capacitor C _DC, a voltage V _DC increases.

Therefore, the controller 24 sets the upper limit value V _high voltage ^{_{V DC (= V DC * +}} ΔV) and the lower limit value ^{_{V low (= V DC * -ΔV}} ). V _DC ^* is a desired voltage V _DC , and ΔV is a hysteresis width.

The controller 24 operates the power converter 21 in the short mode when the voltage V _DC > the upper limit value V _high , and rectifies the power converter 21 when the voltage V _DC <the lower limit value V _low. Operate in mode. By doing so, as shown in FIG. 8, the voltage V _DC can be maintained within the range of the hysteresis width (ΔV) from V _DC ^* up and down. Therefore, by setting the voltage V _DC η _max calculated by the expression (3) to V _DC ^* and setting ΔV to an appropriate value (for example, 1 V), the voltage V _DC is substantially maintained at the voltage V _DC η _max . be able to.

The controller 24 sets the voltage V _DC to the voltage V _DC η _max , maximizes the transmission efficiency η, and controls the power converter 22 to perform desired power control. Figure 5 (a) and as shown in FIG. 5 (b), when turning on the switch 221, a current flows from the capacitor C _DC, if you turn off the switch 221, current flows only from the inductor L _load.

The state equations in the state where the switch 221 is turned on (FIG. 5A) and the state where the switch 221 is turned off (FIG. 5B) are respectively expressed by the following equations (7) and (8) from the circuit equation. The In Expressions (7) and (8), i _L (t) is a load current.

  The following equation (9) is obtained from the equations (7) and (8) by the state space averaging method.

Here, d (t) is a ratio of the ON state of the switch 221. Since this model is non-linear, i _L (t) and d (t) are defined as follows. Note that D ₁ is a ratio of ON / OFF of the switch 221.

  When the equation (9) is linearized around the equilibrium point using this definition, the following equation (10) is obtained.

Therefore, the transfer function ΔP _i (s) from Δd (s) to Δi _L (s) is expressed by the following equation (11).

From equation (11), the equilibrium point is obtained from equation (12) from the load current control command value I _L ^* corresponding to the desired received power and the restrictions of the DC / DC converter.

The controller 24 controls the duty ratio D of the power converter 21 so that the voltage V _DC becomes the voltage V _DC η _max, and the switch 221 is turned on with the duty ratio D ₁ obtained by the equation (12). OFF is controlled (the input / output current ratio and input / output voltage ratio of the power converter 22 are controlled). By doing so, the load current I _L can be matched with the command value I _L ^* , and the desired received power P ₂ can be obtained. Therefore, both efficiency control and desired power control can be achieved.

As shown in FIG. 4, a DC / AC converter can be used as the power converter 22. In this case also, to flow command value I _L ^* a load current I _L corresponding to that, by controlling ON switches 221 to 224, off, it is possible to obtain a desired received power.

As described above, according to this embodiment, the power receiving device 20 is connected to the coil L ₂ that receives AC power from the power transmission side by wireless power transmission using a magnetic field or an electric field, and the AC voltage received by the coil L ₂ is converted to DC. A power converter 21 that rectifies the voltage, and a power converter 22 that is connected to the power converter 21 and converts the DC voltage rectified by the power converter 21 into an arbitrary DC voltage or AC voltage and supplies the DC voltage to the load 23. And a controller 24 that controls the transmission efficiency η using one of the power converter 21 and the power converter 22 and controls the received power P ₂ using the other.

  Therefore, it is possible to achieve both efficiency control and desired power control in wireless power transmission only on the power receiving side.

(Second Embodiment)
In the first embodiment, one of the power converters 21 and 22 is used to control the transmission efficiency η and the other is used to control the received power P _2. However, the present invention is not limited to this. In addition, it is possible to achieve both efficiency control and desired power control with a single power converter. In the second embodiment of the present invention, a configuration example in which efficiency control and desired power control are compatible with one power converter will be described.

  FIG. 9 is a diagram illustrating a configuration example of the power receiving device 20a according to the second embodiment of the present invention. In FIG. 9, the same components as those in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted.

  The power receiving device 20a shown in FIG. 9 is different from the power receiving device 20 shown in FIG. 3 in that the power converter 22 is deleted and the controller 24 is changed to the controller 24a.

The power converter 21 is an AC / DC converter, rectifies the voltage V ₂ and supplies it to the load 23.

The controller 24 a uses the power converter 21 to control the transmission efficiency η and the received power P ₂ .

Also in this embodiment, a power converter 22 (DC / DC converter or DC / AC converter) may be provided between the capacitor _CDC and the load 23. Even in this case, the controller 24 a controls the transmission efficiency η and the received power P ₂ using only the power converter 21.

  Next, the control operation of the power converter 21 by the controller 24a will be described.

  First, control of transmission efficiency η (control for maximizing transmission efficiency η) will be described.

By operating the power converter 21 in synchronization with the resonance frequency of the resonance circuit including the coil L ₂ , the fundamental wave component V ₂₀ of the voltage V ₂ involved in power transmission is controlled, and the transmission efficiency η is maximized. be able to.

  FIG. 10 is a diagram illustrating a waveform of the output voltage of the power converter 21 when the power converter 21 is operated in synchronization with the resonance frequency.

When the power converter 21 is operated in synchronization with the resonance frequency, the output voltage of the power converter 21 has three states (a state of + V _DC , a state of 0 V, or a state of −V _DC ). Take. More specifically, the output voltage is 0 V in the period from the beginning of one cycle (the reciprocal of the resonance frequency (Resonant frequency)) to the lapse of α and the period from α before the end of one cycle to the end of one cycle. In other periods, it becomes + V _DC or -V _DC . Hereinafter, α is referred to as a phase angle.

FIG. 11 is a diagram in which voltage V ₂ and current I ₂ are superimposed on the output waveform of power converter 21 shown in FIG.

As described above, the output voltage is 0 V in the period from the beginning of one cycle to the passage of α and in the period from α before the end of one cycle to the end of one cycle. That is, in this period, even if the voltage V ₂ and the current I ₂ are input, the output voltage of the power converter 21 is 0 V. In other periods, the output voltage of the power converter 21 is + V _DC or −V _DC. It becomes. Therefore, it can be seen that the power transmission efficiency η in one cycle changes by controlling the length of the phase angle α.

When the waveform shown in FIG. 10 is Fourier series expanded and the fundamental wave component V ₂₀ of the voltage V ₂ is calculated, it is expressed by the following equation (13).

  The phase angle α at which the transmission efficiency η is maximized is obtained from the equation (13) by the following equation (14).

  As described above, the power converter 21 can operate in the short mode and the rectification mode. Therefore, the controller 24a controls the period during which the power converter 21 is operated in the short mode so that the phase angle α becomes a value at which the transmission efficiency η obtained by the equation (14) becomes maximum. By doing so, the transmission efficiency η can be maximized.

In addition, the controller 24a performs desired power control by the same control as in the first operation example of the first embodiment described above. That is, the controller 24a includes a period of operation in the short mode, by the ratio of the period of operating in the rectifier mode (Duty ratio), to control the reception power P _2. Here, the controller 24a, for the control of the reception power P ₂ is (switches between short mode and the rectification mode) for operating the power converter 21 at a frequency lower than the resonant frequency.

  FIG. 12 is a diagram illustrating a waveform of a control signal of the power converter 21 by the controller 24a.

As shown in FIG. 12, the controller 24a operates the power converter 21 in the short mode at predetermined time intervals so that the desired received power P ₂ can be obtained. Further, the controller 24a in the period other than the period T _s of operating a power converter 21 in the short mode to control the reception power P _2, switches the operation mode of the power converter 21 in the short mode and the rectification mode Thus, the transmission efficiency η is controlled. Here, the controller 24a switches the operation mode of the power converter 21 for control of the reception power P ₂ is carried out at a frequency lower than the resonant frequency. Further, the controller 24a operates the power converter 21 in synchronization with the resonance frequency in a period other than the period T _s in which the power converter 21 is operated in the short mode for controlling the received power P ₂ , and the phase The angle α is set so that the transmission efficiency η is maximized. By doing so, it is possible to achieve both efficiency control and desired power control using only the power converter 21.

According to this embodiment, the power receiving device 20a is connected to the coil L ₂ to obtain the AC power from the power transmission side by wireless power transmission using a magnetic field or an electric field, an AC power of voltage coil L ₂ is obtained Is converted to a DC voltage and supplied to the load 23, and the controller 24a is used to control the transmission efficiency η and the received power P ₂ using the power converter 21.

  Therefore, it is possible to achieve both efficiency control and desired power control in wireless power transmission using only one power converter 21 only on the power receiving side.

  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 variations or modifications based on the present disclosure. Therefore, it should be noted that these variations or modifications are included in the scope of the present invention. For example, functions included in each block or the like can be rearranged so that there is no logical contradiction, and a plurality of blocks can be combined into one or divided.

DESCRIPTION OF SYMBOLS 1 Wireless power transmission system 10 Power transmission apparatus 11 AC power supply 20 Power receiving apparatus 21, 22 Power converter 23 Load 24, 24a Controller 111-114, 211-124, 221-224 Switch 115 DC power supply

Claims (6)

A first power converter connected to a coil that receives AC power from a power transmission side by wireless power transmission using a magnetic field or an electric field, and rectifies the AC voltage received by the coil into a DC voltage;
A second power converter connected to the first power converter and converting the DC voltage rectified by the first power converter into an arbitrary DC voltage or AC voltage;
One of the first power converter and the second power converter is used to control power transmission efficiency with the power transmission side, and the other is used to control received power from the power transmission side. A controller to
A power receiving device comprising: The power receiving device according to claim 1,
The first power converter includes a first mode for short-circuiting the coil so as to cut off the received power of the coil, and a second mode for rectifying the received power of the coil,
The second power converter is capable of controlling an input / output voltage ratio and an input / output current ratio,
The controller controls the transmission efficiency by controlling an input / output voltage ratio and an input / output current ratio of the second power converter, and the first power conversion so as to obtain a desired received power. A power receiving device, wherein the operation mode of the device is switched between the first mode and the second mode. The power receiving device according to claim 1,
The first power converter includes a first mode for short-circuiting the coil so as to cut off the received power of the coil, and a second mode for rectifying the received power of the coil,
The second power converter is capable of controlling an input / output voltage ratio and an input / output current ratio,
The controller controls the transmission efficiency by switching an operation mode of the first power converter between the first mode and the second mode, so that the desired received power can be obtained. A power receiving apparatus that controls an input / output voltage ratio and an input / output current ratio of the power converter of No. 2. A power converter that is connected to a coil that receives AC power from a power transmission side by wireless power transmission using a magnetic field or an electric field, and that converts the AC voltage received by the coil into a DC voltage;
Using the power converter, a controller for controlling the power transmission efficiency with the power transmission side and the received power from the power transmission side,
A power receiving device comprising: The power receiving device according to claim 4,
The power converter includes a first mode in which the coil is short-circuited so as to cut off a received power of the coil, and a second mode in which the received power of the coil is rectified.
The controller operates the power converter in the first mode at a frequency slower than a resonance frequency of a resonance circuit including the coil so as to obtain a desired received power, and obtains the desired received power. The operation mode of the power converter is set to the first mode and the second mode in synchronization with the resonance frequency in a period other than a period in which the power converter is operated in the first mode according to control for A power receiving apparatus that controls transmission efficiency with the power transmission side by switching between modes. The power receiving device according to any one of claims 1 to 5,
The power receiving device further comprising a capacitor connected to the coil.