Contactless Power Transmission System

Abstract

To provide a non-contact power transmission system that can perform appropriate power control and abnormality detection.SOLUTION: A non-contact power transmission system 1 comprises a power receiving unit 15, a received power conversion unit 16, a current sensor, and a control unit 17. The power receiving unit 15 includes a secondary-side coil that receives AC power transmitted from a primary-side coil of a power transmitting device 2 in a non-contact manner. The received power conversion unit 16 converts the AC power received by the power receiving unit 15 into DC power. The current sensor detects current output from the received power conversion unit 16. The control unit 17 acquires the mutual inductance Lm between the primary-side coil and the secondary-side coil on the basis of a detection value of current output from the current sensor, and controls the received power conversion unit 16 according to the mutual inductance Lm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a contactless power transfer system. [Background technology]

[0002] In recent years, research and development has been conducted into charging vehicles equipped with secondary batteries that contribute to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable and advanced energy. Conventionally, in a contactless power transfer system that supplies power from outside the vehicle to the vehicle by contactless power transfer, a system is known in which the coupling coefficient and transmission efficiency are adjusted by mechanically changing the relative positional relationship between an inductor on the power transmitting side and an inductor on the power receiving side (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-201867 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology for charging and supplying power to a vehicle equipped with a secondary battery, it is desirable to perform appropriate power control and abnormality detection when transmitting power to the vehicle in a non-contact manner. However, the ground height of the power receiving coil may change depending on, for example, the class of the vehicle on which the power receiving unit is mounted, the replacement or modification of the tires and suspension of each vehicle, and changes in the load capacity. The change in the gap between the power transmitting coil and the power receiving coil may change the power that can be supplied and may make it difficult to detect abnormalities.

[0005] An object of the present invention is to provide a contactless power transfer system capable of performing appropriate power control and abnormality detection, which in turn contributes to improving energy efficiency. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the above object, the present invention employs the following aspects. (1): A contactless power transfer system according to one aspect of the present invention (e.g., contactless power transfer system 1 in the embodiment) includes a power receiving unit (e.g., power receiving unit 15 in the embodiment) having a power receiving coil (e.g., secondary coil 15a in the embodiment) that receives AC power transferred contactlessly from a power transmitting coil (e.g., primary coil 8a in the embodiment) of a power transmitting device (e.g., power transmitting device 2 in the embodiment), a power conversion unit (e.g., receiving power conversion unit 16 in the embodiment) that converts the AC power received by the power receiving unit into DC power, a current sensor (e.g., current sensor 17a in the embodiment) that detects a current output from the power conversion unit, and a control device (e.g., control device 17 in the embodiment) that obtains a mutual inductance (e.g., mutual inductance Lm in the embodiment) between the power transmitting coil and the power receiving coil based on a detection value of the current output from the current sensor and controls the power conversion unit in accordance with the mutual inductance.

[0007] (2): In the contactless power transfer system described in (1) above, the control device may acquire the mutual inductance based on the detection value of the current output from the current sensor without regulating the output of the power conversion unit.

[0008] (3): In the contactless power transfer system described in (2) above, the control device may regulate the output of the power conversion unit when the mutual inductance is less than a predetermined threshold (e.g., a predetermined threshold Lth in an embodiment).

[0009] (4) In the contactless power transfer system described in (3) above, the control device may regulate the output of the power conversion unit by a short-circuiting operation for short-circuiting the power receiving coil. Effect of the Invention

[0010] According to (1) above, by providing a control device that controls the power conversion unit according to the mutual inductance obtained based on the detection value of the current, appropriate power control and abnormality detection can be performed even when the distance (gap) between the transmitting coil and the receiving coil changes.

[0011] In the case of (2) above, by acquiring the mutual inductance in a state of full output without regulating the output, it is possible to detect the change in mutual inductance with high accuracy.

[0012] In the above case (3), when the mutual inductance falls below a predetermined threshold value due to a moving body such as a vehicle equipped with a power receiving unit leaving the power transmission section or due to the occurrence of an abnormality, appropriate control can be performed by regulating the output of the power conversion unit.

[0013] In the case of (4) above, the power received by the power receiving unit can be regulated by short-circuiting the power receiving coil, and the current in the power transmitting device can be throttled, allowing independent power control by the power receiving unit and the power control unit. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram showing a configuration of a contactless power transmission system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing details of the configuration of a contactless power transfer system according to an embodiment of the present invention. [Diagram 3] 1 is a diagram showing the configuration of a power transmitting unit and a power receiving unit in a contactless power transfer system according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing a T-type equivalent circuit in the contactless power transfer system according to the embodiment of the present invention. [Diagram 5]4 is a graph showing an example of the correspondence relationship between the distance between the coils on the power transmitting side and the coils on the power receiving side (the distance in a direction perpendicular to the opposing direction) and mutual inductance in the contactless power transfer system according to the embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a contactless power transfer system according to an embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 and Fig. 2 are diagrams showing the configuration of a contactless power transfer system 1 according to an embodiment. Fig. 3 is a diagram showing the configurations of a power transmitting unit 8 and a power receiving unit 15 of the contactless power transfer system 1 according to an embodiment. A contactless power transfer system 1 according to the embodiment supplies power to a moving body such as a vehicle from outside the moving body by contactless power transfer. The vehicle is, for example, an electrically-driven vehicle such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle.

[0016] (Non-contact power transmission system) 1 and 2, a contactless power transfer system 1 according to an embodiment includes, for example, a power transmitting device 2 installed on a vehicle's running path or the like, and a drive control device 3 and a power receiving device 4 mounted on a moving body such as a vehicle. Note that the contactless power transfer system 1 according to an embodiment may include at least only components mounted on the moving body (for example, the drive control device 3 and the power receiving device 4), or contactless power transfer may be performed by combining components external to the moving body (for example, the power transmitting device 2) with the contactless power transfer system 1 mounted on the moving body.

[0017] The power transmission device 2 includes, for example, a power supply unit 6, a power transmission power conversion unit 7, and a power transmission unit 8. Note that the power transmission device 2 may include at least a plurality of power transmission units 8 in a predetermined power transmission section on a road on which the vehicle runs, for example. The power supply unit 6 includes, for example, an AC power supply such as a commercial power supply, an AC-DC converter that converts the AC power into DC power, and a power smoothing capacitor. The power supply unit 6 converts the AC power supplied from the AC power supply into DC power by the AC-DC converter.

[0018] The transmission power conversion unit 7 includes, for example, an inverter that converts DC power into AC power. The inverter of the transmission power conversion unit 7 includes, for example, a bridge circuit formed by a plurality of switching elements and rectifying elements that are bridge-connected in two phases, and a voltage smoothing capacitor. Each switching element is, for example, a transistor such as a SiC (Silicon Carbide) MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The multiple switching elements are high-side arm and low-side arm transistors 7a and 7b that form a pair in each phase. The rectifying element is, for example, a free wheel diode connected in parallel to each of the transistors 7a and 7b. A voltage smoothing capacitor 7c is connected in parallel to the bridge circuit.

[0019] The power transmitting unit 8 transmits power by changing a high-frequency magnetic field, for example, by magnetic field coupling such as magnetic resonance or electromagnetic induction. As shown in Fig. 3, the power transmitting unit 8 includes a resonant circuit formed by a primary coil 8a, a primary resistor 8b, and a primary capacitor 8c connected in series. The power transmitting unit 8 includes a sensor such as a current sensor that detects a current It flowing through the resonant circuit.

[0020] For example, the power transmitting device 2 transmits power to the power receiving device 4 of a moving body such as a vehicle by controlling the on (conducting) and off (cutting) switching of each switching element of the transmission power conversion unit 7 in accordance with a preset driving frequency or information on a required frequency received from the power receiving device 4.

[0021] 1 and 2, a drive control device 3 of a moving body such as a vehicle includes, for example, a power storage device 11, a power conversion unit 13, and a rotating electric machine 14. A power receiving device 4 of the moving body includes, for example, a power receiving unit 15 and a received power conversion unit 16. The drive control device 3 and the power receiving device 4 include, for example, a common control device 17.

[0022] The power storage device 11 is connected to a power conversion unit 13 and a receiving power conversion unit 16, which will be described later. The power storage device 11 is charged by power transmitted in a non-contact manner from a power transmission device 2 outside the vehicle. The power storage device 11 exchanges power with a rotating electric machine 14 via the power conversion unit 13. The power storage device 11 includes a battery, such as a lithium ion battery, a current sensor that detects the current of the battery, and a voltage sensor that detects the voltage of the battery.

[0023] The power conversion unit 13 is connected to a rotating electric machine 14. The power conversion unit 13 includes, for example, a power converter that converts between DC power and AC power. The power converter includes, for example, a second element module and a voltage smoothing capacitor. The second element module includes, for example, a second bridge circuit formed by a plurality of switching elements and rectifier elements bridge-connected in three phases. Each switching element is, for example, a transistor such as a SiC MOSFET. The plurality of switching elements are high-side arm and low-side arm transistors 13a and 13b that form a pair in each phase. The rectifier elements are, for example, freewheeling diodes connected in parallel to each of the transistors 13a and 13b. A voltage smoothing capacitor 13c is connected in parallel to the second bridge circuit.

[0024] The second element module controls the operation of the rotating electric machine 14 by receiving and transmitting electric power. For example, when the rotating electric machine 14 is powered, the second element module converts DC power input from the positive and negative DC terminals 13p, 13n into three-phase AC power and supplies the three-phase AC power from the three-phase AC terminals 13d to the rotating electric machine 14. The second element module generates a rotational driving force by sequentially commutating the current to the three-phase stator windings of the rotating electric machine 14. For example, during regeneration of the rotating electric machine 14, the second element module converts the three-phase AC power input from the three-phase stator windings into DC power by driving the switching elements of each phase to be on (conductive) and off (cutting) in synchronization with the rotation of the rotating electric machine 14. The second element module can supply the DC power converted from the three-phase AC power to the power storage device 11.

[0025] The rotating electric machine 14 is, for example, a three-phase AC brushless DC motor provided for driving a vehicle. The rotating electric machine 14 includes a rotor having a permanent magnet for a field, and a stator having a three-phase stator winding that generates a rotating magnetic field that rotates the rotor. The three-phase stator winding is connected to three-phase AC terminals 13d of the power conversion unit 13. The rotating electric machine 14 generates a rotational driving force by performing a power running operation using the electric power supplied from the electric power conversion unit 13. For example, if the rotating electric machine 14 can be connected to the wheels of a vehicle, the rotating electric machine 14 generates a driving force for traveling by performing a power running operation using the electric power supplied from the electric power conversion unit 13. The rotating electric machine 14 may generate electric power by performing a regenerative operation using rotational power input from the wheel side of the vehicle. If the rotating electric machine 14 can be connected to an internal combustion engine of the vehicle, the rotating electric machine 14 may generate electric power using the power of the internal combustion engine.

[0026] The power receiving unit 15 is connected to the receiving power conversion unit 16. The power receiving unit 15 receives power by a change in a high-frequency magnetic field transmitted from the power transmitting unit 8, for example, by magnetic field coupling such as magnetic resonance or electromagnetic induction. As shown in Fig. 3, the power receiving unit 15 includes a resonant circuit formed by, for example, a secondary side coil 15a, a secondary side resistor 15b, and a secondary side capacitor 15c connected in series. The power receiving unit 15 includes a sensor such as a current sensor that detects a current Ir flowing through the resonant circuit.

[0027] 1 and 2 is connected to the power conversion unit 13. The receiving power conversion unit 16 includes a so-called full-bridgeless (or bridgeless and totem-pole) power factor correction (PFC) circuit that converts AC power into DC power. The so-called bridgeless PFC is a PFC that does not include a bridge rectifier made of multiple bridge-connected diodes, and the so-called totem-pole PFC is a PFC that includes a pair of switching elements of the same conductivity type that are connected in series in the same direction (totem-pole connection).

[0028] The receiving power conversion unit 16 includes, for example, a third bridge circuit formed by a plurality of switching elements and rectifying elements bridge-connected in two phases, and a voltage smoothing capacitor. Each switching element is, for example, a transistor such as a SiC MOSFET. The plurality of switching elements are high-side arm and low-side arm transistors 16a, 16b that form a pair in each phase. The rectifying element is, for example, a free wheel diode connected in parallel to each of the transistors 16a, 16b. The voltage smoothing capacitor 16c is connected in parallel to the third bridge circuit.

[0029] For example, a power receiving device 4 equipped with a power receiving unit 15 and a power receiving power conversion unit 16 receives power transmitted from the power transmitting device 2 by controlling the on (conducting) and off (cutting) switching of each switching element of the power receiving power conversion unit 16 in accordance with information on the frequency of power transmission by the power transmitting device 2.

[0030] The control device 17 comprehensively controls, for example, the drive control device 3 and the power receiving device 4 of a moving body such as a vehicle. The control device 17 is a software function unit that functions by a processor such as a CPU (Central Processing Unit) executing a predetermined program. The software function unit is an ECU that includes a processor such as a CPU, a ROM (Read Only Memory) that stores programs, a RAM (Random Access Memory) that temporarily stores data, and electronic circuits such as a timer. At least a part of the control device 17 may be an integrated circuit such as an LSI (Large Scale Integration).

[0031] The control device 17 generates, for example, control signals indicating the timing for driving each switching element on (conducting) and off (cutting), and generates gate signals for actually driving each switching element on and off based on the control signals. For example, the control device 17 controls the switching of each switching element of the power receiving device 4 to rectify the AC power received from the power transmitting device 2 into DC power, while improving the power factors of the input voltage and the input current. For example, the control device 17 controls the switching operation of multiple switching elements of the receiving power conversion unit 16 based on a detection value of a current output from a current sensor 17a that detects a current output from the receiving power conversion unit 16 and a detection value of a voltage output from a voltage sensor 17b that detects a voltage output from the receiving power conversion unit 16.

[0032] For example, the control device 17 controls the output according to the target output by a synchronous rectification operation that synchronously drives a plurality of switching elements of the power receiving device 4 to be turned on and off, and a short-circuit operation that short-circuits the secondary coil 15a. For example, the control device 17 controls the synchronous rectification operation according to the magnitude and phase of a current generated in the power receiving unit 15 by the power transmitted from the power transmitting device 2, i.e., a current Ir flowing through the secondary coil 15a. The control device 17 controls the multiple switching elements of the power receiving power conversion unit 16 by soft switching of so-called zero voltage switching (ZVS). In zero voltage switching (ZVS), each switching element is turned on (switched from an off state to an on state) after the voltage across both ends is made zero by discharging the output capacitance (parasitic capacitance) in the off state during the dead time period of each phase.

[0033] For example, the control device 17 controls the short-circuit operation by turning on only the low-side arm of each phase while continuing the synchronous rectification operation of zero voltage switching (ZVS) in the high-side arm of each phase of the receiving power conversion unit 16. The control device 17 increases the secondary impedance when the secondary-side power receiving device 4 is seen from the primary-side power transmitting device 2 by shorting the secondary-side coil 15a, thereby reducing the primary-side current (power transmission current: current It flowing through the primary-side coil 8a). The control device 17 controls the current of the primary-side power transmitting device 2 by the secondary-side power receiving device 4, thereby performing independent power control such as stopping power transmission on the power receiving device 4 side.

[0034] For example, the control device 17 obtains the mutual inductance Lm between the primary coil 8a and the secondary coil 15a based on the detection values ​​output from the current sensor 17a and the voltage sensor 17b, and controls the receiving power conversion unit 16 according to the mutual inductance Lm. FIG. 4 is a diagram showing a T-type equivalent circuit in the contactless power transfer system 1 of the embodiment. As shown in FIG. 4, the T-type equivalent circuit of the contactless power transfer system 1 is described, for example, by the voltage Vt of the AC voltage source 21, the capacitance Ct, internal resistance Rt, self-inductance Lt, and current It of the power transmitting unit 8, the mutual inductance Lm, the capacitance Cr, internal resistance Rr, self-inductance Lr, and current Ir of the power receiving unit 15, and the voltage Vr and load resistance RL of the load resistor 22. The load resistance 22 corresponds to, for example, the receiving power conversion unit 16 and a load resistance A connected between the DC terminals (positive and negative poles) of the receiving power conversion unit 16. The load resistance A is, for example, the drive control device 3.

[0035] As shown in the voltage equation shown in the following formula (1), the current It of the power transmitting unit 8, and the current Ir and voltage Vr of the power receiving unit 15 are expressed by the frequency ω 0 , the mutual inductance Lm, the resistance values ​​Rt, Rr, RL, and the voltage Vt of the power transmitting unit 8.

[0036]

number

[0037] As shown in the following formula (2), for example, when the voltage Vt of the power transmitting unit 8 and the voltage Vr of the power receiving unit 15 are set to be the same as each other to ensure efficient power transmission, the load resistance value RL is determined based on the above formula (1) by the frequency ω 0 , the mutual inductance Lm, and the internal resistance values ​​Rt and Rr.

[0038]

number

[0039] In the load resistor 22, the receiving power conversion unit 16 operates to convert (step down) the voltage Vr to the voltage V1 of the load resistor A, so that the load resistance value RL' of the load resistor A seen from the transmitting side when the waveform of the current Ir is averaged is described based on the voltage V1 and current Irdc of the load resistor A, as shown in the following formula (3). For example, the current Irdc of the load resistor A is detected by the current sensor 17a, and the voltage V1 of the load resistor A is detected by the voltage sensor 17b.

[0040]

number

[0041] As shown in the above formula (3), the load resistance value RL′ is calculated based on, for example, the voltage V1 and the current Irdc of the load resistor A, by multiplying the load resistance value RL′ by a predetermined coefficient k (for example, k=π 2 / 8) and the power transmission frequency ω 0 , the mutual inductance Lm, and the internal resistance values ​​Rt and Rr. For example, a given coefficient k (e.g., k=π 2 / 8) is set based on the fact that when the voltage V1 is clamped (fixed) by the connection of the power storage device 11 and the waveform of the current Ir is sinusoidal, an averaged current is output from the receiving power conversion unit 16. The predetermined coefficient k is, for example, a coefficient according to a smoothing ratio when the current is averaged. The predetermined coefficient k may be changed as appropriate according to, for example, a current waveform other than a sinusoidal waveform corresponding to an individual device or the like.

[0042] The control device 17 acquires the mutual inductance Lm based on the detection values ​​output from the current sensor 17a and the voltage sensor 17b and the above formula (3) in a full output section other than the section in which the output of the power receiving power conversion unit 16 is regulated by a short-circuiting operation that shorts the secondary coil 15a among the predetermined power transmission sections. The control device 17 controls the power transmission by grasping the relative positional relationship between the power transmitting unit 8 and the power receiving unit 15 according to the mutual inductance Lm.

[0043] FIG. 5 is a graph showing an example of the correspondence relationship between the distance between the coils on the power transmitting side and the coils on the power receiving side (the distance in the direction perpendicular to the opposing direction) and the mutual inductance Lm in the contactless power transfer system 1 of the embodiment. 5, when the inter-coil distance between the primary coil 8a and the secondary coil 15a is in the range from zero to a predetermined threshold distance Dth, the control device 17 executes full-wave rectification with full-open output that does not restrict the output by, for example, a synchronous rectification operation of the receiving power conversion unit 16. The predetermined threshold distance Dth corresponds to, for example, a predetermined threshold Lth of the mutual inductance Lm, and specifies the range in which the efficiency of power transmission is 85% or more.

[0044] For example, when the mutual inductance Lm is less than a predetermined threshold Lth as the inter-coil distance becomes greater than a predetermined threshold distance Dth, the control device 17 stops full-wave rectification by full-open output of the receiving power conversion unit 16. For example, the control device 17 causes the power receiving device 4 to transition to a standby state by a short-circuit operation of the receiving power conversion unit 16, and controls the current of the primary-side power transmission device 2, such as by reducing the output or stopping power transmission. In addition, the control device 17 detects the occurrence of an abnormality when the mutual inductance Lm falls below a predetermined threshold value Lth, for example, when damage such as cracks or chips occurs in the core member made of a magnetic material provided together with the secondary coil 15a of the power receiving unit 15 due to vehicle body vibration or the like.

[0045] As described above, according to the embodiment of the contactless power transmission system 1, by controlling the receiving power conversion unit 16 according to the mutual inductance Lm obtained based on the detection value of the current output from the receiving power conversion unit 16, appropriate power control and abnormality detection can be performed even when the distance (gap) between the primary coil 8a and the secondary coil 15a changes. By acquiring the mutual inductance Lm in a state of full output where the output is not restricted, the change in the mutual inductance Lm can be detected with high accuracy.

[0046] When a moving body such as a vehicle carrying a power receiving device 4 leaves the power transmission section or an abnormality occurs, etc., and the mutual inductance Lm falls below a predetermined threshold value Lth, appropriate control can be performed by regulating the output of the receiving power conversion unit 16. By short-circuiting the secondary coil 15a, the power received by the power receiving section 15 can be regulated, the current of the power transmitting device 2 can be reduced, and independent power control can be performed by the power receiving device 4 on the secondary side.

[0047] (Modification) In the above-described embodiment, the contactless power transmission system 1 is provided with a voltage sensor 17b that detects the voltage output from the receiving power conversion unit 16, but this is not limited to this, and may be provided with other voltage sensors that detect voltages in various devices on the power receiving side, such as the drive control device 3, and the voltage output from the receiving power conversion unit 16 may be obtained from the output of the other voltage sensors.

[0048] In the above-described embodiment, the contactless power transfer system 1 may include a storage voltage converter that converts input and output power of the power storage device 11 in the case of a hybrid vehicle or the like that is driven by the power storage device 11 and an internal combustion engine as a power source.

[0049] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents as described in the claims, as well as the scope and spirit of the invention. [Explanation of symbols]

[0050] Reference Signs List 1...non-contact power transfer system, 2...power transmission device, 3...drive control device, 4...power receiving device, 6...power supply unit, 7...transmission power conversion unit, 8...power transmission unit, 8a...primary coil (transmission side coil), 11...energy storage device, 13...power conversion unit, 14...rotating electric machine, 15...power receiving unit, 15a...secondary coil (receiving side coil), 16...received power conversion unit (power conversion unit), 17...control device, 17a...current sensor, 17b...voltage sensor.

Claims

1. a power receiving unit having a power receiving coil for receiving AC power transmitted in a non-contact manner from a power transmitting coil of a power transmitting device; a power conversion unit that converts the AC power received by the power receiving unit into DC power; a current sensor for detecting a current output from the power conversion unit; a control device that acquires a mutual inductance between the power transmitting coil and the power receiving coil based on a detection value of the current output from the current sensor, and controls the power conversion unit in accordance with the mutual inductance; Equipped with The control device includes: The mutual inductance is obtained based on a detection value of the current output from the current sensor in a state where the output of the power conversion unit is not regulated. Contactless power transmission system.

2. The control device includes: The contactless power transfer system according to claim 1 , wherein an output of the power conversion unit is regulated when the mutual inductance is less than a predetermined threshold value.

3. The control device includes: The output of the power conversion unit is regulated by a short-circuit operation for short-circuiting the power receiving coil. The contactless power transfer system according to claim 2 .

Images