JP2016127647A - Power transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit target electric power using more appropriate frequency and duty.SOLUTION: An initial frequency fst is set in accordance with a coupling coefficient (k) based on output impedance Zs of an inverter (S130) and defined as predetermined duty (S140). Processes (S150 and S160) for changing a frequency (f) by a minute frequency Δf until transmission of target electric power and a process (S170) for reducing the duty just by a decrease amount Δd are repeated until an output current Is in timing for turning off a switching element of the inverter when transmitting the target electric power is settled within a range between a threshold Iref of a negative value and a value 0. Electric power transmission is then performed using the obtained frequency (f) and duty. At such a time, since a current phase θ is settled within a predetermined range at a lag side with respect to the output voltage, no recovery current flows to a diode of the inverter. As a result, target electric power can be transmitted using more appropriate frequency and duty.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a power transmission device, and more particularly to a power transmission device that transmits power to a power receiving device in a contactless manner.

  Conventionally, as this type of technology, an alternating current corresponding to the drive frequency is output from the inverter to the power transmission coil, the power transmitted from the power transmission coil is received by the power reception coil by magnetic coupling, and the received power is converted to DC power. A non-contact power feeding system that converts and charges a battery has been proposed (see, for example, Patent Document 1). In this system, the drive frequency of the inverter is feedback-controlled based on the output voltage and output current to the battery and the charge power command to the battery.

JP 2014-207795 A

  In many cases, a power transmission device in a non-contact power transmission system includes an inverter that is driven by pulse width modulation (PWM) control in order to adjust the frequency and power of AC power for power transmission. In this case, the inverter is generally composed of four switching elements Q91 to Q94 and four diodes D91 to D94 connected in parallel to the switching elements Q91 to Q94 in the reverse direction, as shown in FIG. Is done. Two switching elements Q91 to Q94 are arranged in pairs so as to be on the source side and the sink side with respect to the positive electrode bus and the negative electrode bus, respectively, and a power transmission coil is connected to each connection point of the paired switching elements. Are connected to each other.

  In a power transmission device including such an inverter, the phase of current may advance (advance) with respect to an alternating voltage by PWM control. FIG. 9 shows an example of the relationship between the on / off states of switching elements Q91 to Q94 and the output voltage and current states of the inverter. In “Inverter output voltage and current” in the figure, the solid broken line indicates the output voltage, and the solid line sine curve indicates the current when the current phase is advanced with respect to the voltage phase. Consider a case where the switching element Q91 shifts from an off state to an on state. At time T1 when switching element Q91 is off, the inverter output voltage has a value of 0, but the current has a positive value because the phase has advanced. At this time, as shown in FIG. 10A, the current flows from the lower power line on the power transmission coil side to the on-state switching element Q94, the on-state switching element Q93, the diode D93, and the power transmission coil side. It flows in the order of the power lines. At time T2 immediately after the switching element Q91 is turned on, the inverter output voltage has a positive value, and the current maintains a positive value. At this time, as shown in FIG. 10 (b), the current flows from the positive bus (upper bus) to the power line on the power transmission coil side via the switching element Q91 in the ON state, and at the power transmission coil side. Flows from the lower power line to the negative bus (lower bus) via the switching element Q94 in the on state. A forward bias is applied to the diode D93 at time T1 when the switching element Q91 is in the OFF state, and a reverse bias is applied at time T2 immediately after the switching element Q91 is turned on. For this reason, due to the recovery characteristics of the diode, a recovery current flows through the diode D93 as shown by the thick arrow in FIG. Since this recovery current is a short-circuit current, it may cause a malfunction or failure of the power transmission device.

  In order to transmit the target power, it is necessary to adjust the duty of the alternating voltage by PWM control. Even if it can be adjusted so that the phase of the current does not advance with respect to the alternating voltage by PWM control, if the duty of the alternating voltage by PWM control is changed, the rising of the alternating voltage is changed. As a result, the phase of the current also changes. For this reason, in order to transmit the target power, it is necessary to appropriately adjust the duty of the alternating voltage and the phase of the current. The inventor has obtained knowledge that the phase of the current with respect to the alternating voltage is changed by changing the frequency of the alternating voltage by PWM control. Therefore, in order to transmit the target power, it is only necessary to appropriately adjust the duty and frequency of the alternating voltage.

  The main purpose of the power transmission device of the present invention is to transmit target power using a more suitable frequency and duty.

  The power transmission device of the present invention employs the following means in order to achieve the main object described above.

The power transmission device of the present invention is
A power transmission device that transmits power to a power receiving device in a contactless manner,
An inverter having a plurality of switching elements and a plurality of diodes, and converting DC power derived from an external power source into AC power;
A power transmission unit that transmits AC power from the inverter to a power reception unit of the power reception device;
Control means for adjusting the AC power by switching control of a plurality of switching elements of the inverter;
With
The control means calculates a coupling coefficient between the power reception unit and the power transmission unit, sets a frequency different from the operating point frequency as an initial frequency based on the coupling coefficient, and moves from the initial frequency to the operating point frequency side. The target power is transmitted so that the current phase of the output current to the power transmission unit falls within a predetermined range on the retard side with respect to the output voltage by changing the frequency of the power and the duty of the AC power Is a means to determine the frequency and duty.
It is characterized by that.

  In the power transmission device of the present invention, the coupling coefficient between the power receiving unit and the power transmission unit is calculated, and a frequency different from the operating point frequency is set as the initial frequency based on the calculated coupling coefficient. Subsequently, by changing the frequency from the initial frequency toward the operating point frequency and changing the duty of the AC power, the current phase of the output current to the power transmission unit is within a predetermined range on the retard side with respect to the output voltage. The frequency and the duty are obtained so that the target power is transmitted within the range. Then, the inverter is controlled using the frequency and the duty thus obtained to transmit power. Thereby, electric power can be transmitted with a more suitable frequency and duty. Here, the operating point frequency means a design frequency in power transmission / reception between the power reception unit and the power transmission unit. The predetermined range on the retarded side is a retarded range that allows the current phase to be regarded as the same as the output power, and can be determined as appropriate.

  In such a power transmission device of the present invention, the control means may be means for setting, as the initial frequency, a frequency at which the current phase is retarded with respect to an output voltage. By so doing, the frequency is changed from the state where the current phase is retarded with respect to the output voltage, and therefore it is possible to suppress the flow of the recovery current.

  In the power transmission device of the present invention, the control unit may transmit the target power by changing the frequency of the AC power to a predetermined duty with the frequency of the AC power as the initial frequency and a relatively large duty. And the step of reducing the duty, and the target power is transmitted within the predetermined range of the current phase, thereby making the frequency suitable for transmitting the target power. It may be a means for obtaining the duty. By so doing, it is possible to transmit the target power such that the current phase is within a predetermined range on the retard side with respect to the output voltage.

  Further, in the power transmission device according to the present invention, the control means may be configured such that the current phase is the output voltage when the current at the on or off timing of any one of the plurality of switching elements is within a predetermined current range. It is good also as what determines with being in the predetermined range at the retard angle side.

  Moreover, the power transmission apparatus of this invention WHEREIN: The said control means is good also as a means which calculates the said coupling coefficient based on the output impedance of the said inverter. This is because the output impedance of the inverter can be regarded as a function of the coupling coefficient. In this case, the control means determines that the output coefficient is a function of the self-inductance of the power transmitting unit, the self-inductance of the power receiving unit, the impedance of the power receiving device excluding the power receiving unit, and the coupling coefficient. It may be a means for calculating. Further, in this case, the control means may be means for calculating the coupling coefficient by treating the self-inductance of the power receiving unit and the impedance behind the power receiving unit of the power receiving device as constants. This is because when the power receiving device is standardized and the self-inductance of the power receiving unit and the impedance behind the power receiving unit are not changed, these can be treated as constants. Here, the impedance of the power receiving device excluding the power receiving unit means the impedance behind the power receiving unit. In addition, the control means, the self-inductance of the power receiving unit and the impedance of the power receiving device excluding the power receiving unit, or the ratio of the self inductance of the power receiving unit and the impedance behind the power receiving unit of the power receiving device, It is good also as what is acquired from the said power receiving apparatus, and is a means to calculate the said coupling coefficient. In this way, even when the power receiving apparatus is not standardized, the output impedance can be calculated more accurately, and the coupling coefficient can be calculated more accurately. Note that the ratio between the self-inductance of the power receiving unit and the impedance behind the power receiving unit may be obtained because the output impedance is proportional to the self inductance of the power receiving unit and inversely proportional to the impedance behind the power receiving unit. Because.

It is a block diagram which shows the outline of a structure of the non-contact power transmission / reception system 10 provided with the power transmission apparatus 130 of an Example. It is a block diagram which shows the outline of a structure of the non-contact power transmission / reception system 10 provided with the power transmission apparatus 130 of an Example. 3 is a configuration diagram illustrating an example of a configuration of an inverter 142. FIG. 5 is a flowchart illustrating an example of frequency / duty adjustment processing executed by a power transmission ECU 170. It is explanatory drawing which shows an example of the map for frequency adjustment. It is explanatory drawing which shows an example of the time change of the on-off state of the switching elements Q1-Q4 of the inverter 142, and the output voltage and output current of the inverter 142. FIG. It is explanatory drawing which shows the electric current which flows into an inverter at time T1, T2 of FIG. It is a block diagram which shows an example of a structure of the inverter of a prior art example. It is explanatory drawing which shows an example of the on-off state of the switching elements Q91-Q94 of an inverter of a prior art example, and a time change of an inverter output voltage and electric current. It is explanatory drawing which shows the electric current which flows into an inverter at time T1, T2 of FIG.

  Next, the form for implementing this invention is demonstrated using an Example.

  FIG. 1 and FIG. 2 are block diagrams showing an outline of a configuration of a non-contact power transmission / reception system 10 including a power transmission device 130 as one embodiment of the present invention. As shown in FIGS. 1 and 2, the non-contact power transmission / reception system 10 according to the embodiment includes a power transmission device 130 installed in a parking lot or the like and a power reception device 30 that can receive power from the power transmission device 130 in a contactless manner. And an automobile 20.

  The power transmission device 130 includes a power transmission unit 131 connected to an AC power source 190 such as a household power source (for example, 200 V, 50 Hz), and a power transmission electronic control unit (hereinafter referred to as “power transmission ECU”) 170 that controls the power transmission unit 131. And comprising. The power transmission device 130 includes a communication unit 180 that communicates with the power transmission ECU 170 and performs wireless communication with a communication unit 80 (described later) of the automobile 20.

  The power transmission unit 131 includes an AC / DC converter 140, an inverter 142, a filter 144, and a power transmission resonance circuit 132. The AC / DC converter 140 is configured as a well-known DC / DC converter that converts AC power from the AC power supply 190 into DC power having an arbitrary voltage. As illustrated in FIG. 3, the inverter 142 includes four switching elements Q1 to Q4, four diodes D1 to D4 connected in parallel to the switching elements Q1 to Q4 in the reverse direction, and a smoothing capacitor C. ing. As the four switching elements Q1 to Q4, for example, MOSFET (a kind of field-effect transistor: metal-oxide-semiconductor field-effect transistor) can be used. The switching elements Q1 to Q4 are arranged in pairs so as to be on the source side and the sink side with respect to the positive electrode bus and the negative electrode bus, respectively, and transmit power to each connection point of the paired switching elements. Both terminals of the power coil are connected. The inverter 142 converts the DC power from the AC / DC converter 140 into AC power having a desired frequency by pulse width modulation (PWM) control for switching control of the switching elements Q1 to Q4. The filter 144 is configured as a well-known filter that removes high-frequency noise due to a capacitor and an inductor, and removes high-frequency noise of AC power from the inverter 142.

  The power transmission resonance circuit 132 includes, for example, a power transmission coil 134 installed on a floor surface of a parking lot, and a capacitor 136 connected in series to the power transmission coil 134. The power transmission resonance circuit 132 is designed such that the resonance frequency is a predetermined frequency Fset (several tens to several hundreds kHz). Therefore, the inverter 142 basically converts the DC power from the AC / DC converter 140 into AC power having a predetermined frequency Fset.

  Although not shown, power transmission ECU 170 is configured as a microprocessor centered on a CPU, and includes a ROM for storing processing programs, a RAM for temporarily storing data, an input / output port, and a communication port in addition to the CPU. . The power transmission ECU 170 is input with the following current and voltage through the input port. An output current Is from the current sensor 150 that detects the current (output current) Is of the AC power converted by the inverter 142. A voltage Vs from the voltage detection unit 152 that detects the AC voltage from the inverter 142 by converting it into a DC voltage. A current Itr of the power transmission resonance circuit 132 from the current sensor 154 that detects an alternating current flowing in the power transmission resonance circuit 132. A voltage (transmission voltage) Vtr between terminals of the resonance circuit for power transmission 132 from the voltage detection unit 156 that detects the AC voltage between the terminals of the resonance circuit for power transmission 132 by converting it into a DC voltage. The voltage detection units 152 and 156 have a rectifier circuit and a voltage sensor. Further, the power transmission ECU 170 outputs a control signal to the AC / DC converter 140, a control signal to the inverter 142, and the like via an output port.

  The vehicle 20 is configured as an electric vehicle, and includes a traveling motor 22, an inverter 24 for driving the motor 22, and a battery 26 that exchanges electric power with the motor 22 via the inverter 24. A system main relay 28 is provided between the inverter 24 and the battery 26. In addition, the automobile 20 communicates with a power receiving unit 31 connected to the battery 26, a vehicle electronic control unit (hereinafter referred to as “vehicle ECU”) 70 that controls the entire vehicle, and communication with the power transmission device 130. And a communication unit 80 for performing wireless communication with the unit 180.

  The power reception unit 31 includes a power reception resonance circuit 32, a filter 42, and a rectifier 44. The power receiving resonance circuit 32 includes, for example, a power receiving coil 34 installed on the bottom surface (floor panel) of the vehicle body, and a capacitor 36 connected in series to the power receiving coil 34. The power receiving resonance circuit 32 is designed such that the resonance frequency becomes a frequency (ideally, the predetermined frequency Fset) near the predetermined frequency Fset (resonance frequency of the power transmission resonance circuit 132). The filter 42 is configured as a well-known filter that removes one-stage or two-stage high-frequency noise due to a capacitor and an inductor, and removes high-frequency noise of AC power received by the power receiving resonance circuit 32. The rectifier 44 is configured as, for example, a known rectifier circuit using four diodes, and converts AC power received by the power receiving resonance circuit 32 and from which high-frequency noise has been removed by the filter 42 into DC power. The power receiving unit 31 can be disconnected from the battery 26 by a relay 48.

  Although not shown, the vehicle ECU 70 is configured as a microprocessor centered on a CPU, and includes a ROM for storing a processing program, a RAM for temporarily storing data, an input / output port, and a communication port in addition to the CPU. . Data necessary for drive control of the motor 22 is input to the vehicle ECU 70 via an input port. The vehicle ECU 70 also includes a received current Ire from the current sensor 50 that detects the current (received current) Ire rectified by the rectifier 44 and a voltage sensor that detects the voltage (received voltage) Vre of the DC power. The power reception voltage Vre from 52 is input via the input port. From the vehicle ECU 70, a control signal for switching control of a switching element (not shown) of the inverter 24 to drive the motor 22, an on / off signal to the system main relay 28, and the like are output via an output port. The vehicle ECU 70 determines the storage ratio SOC of the battery 26 based on the battery current Ib detected by a current sensor (not shown) attached to the battery 26 and the battery voltage Vb detected by a voltage sensor (not shown) attached to the battery 26. Is calculated.

  Next, the operation of the power transmission device 130 in the non-contact power transmission / reception system 10 configured as described above, particularly the operation when adjusting the frequency of the inverter 142 and the duty of the AC power will be described. FIG. 4 is a flowchart illustrating an example of frequency / duty adjustment processing executed by the power transmission ECU 170.

  When the frequency / duty adjustment process is executed, the power transmission ECU 170 first inputs the output current Is of the inverter 142 from the current sensor 150 and the voltage Vs from the voltage detection unit 152 (step S100), and outputs the output current Is. Based on the output voltage Vs, the output impedance Zs from the inverter 142 is calculated (step S110). Here, an effective value is used as the output current Is when the impedance Zs is calculated. Then, a coupling coefficient k is obtained based on the output impedance Zs (step S120). The output impedance Zs can be expressed as a function of the coupling coefficient k as shown in the following equation (1). In Equation (1), “ω” is an angular frequency, “L1” is the self-inductance of the power transmission coil 134, “L2” is the self-inductance of the power reception coil 34, and “RL” is behind the power reception resonance circuit 32 (filter). 42 side impedance). Here, the self-inductance L2 of the power receiving coil 34 and the impedance RL behind the power receiving resonance circuit 32 (on the filter 42 side) can be treated as constants. Since the power receiving device 30 is mounted on the automobile 20, the specifications thereof may be different. However, in order to maintain good power transmission / reception efficiency, the power receiving device 30 of a certain standard needs to be used. For this reason, considering the standardized power receiving device 30, the self-inductance L2 and the impedance RL can be treated as constants. In the contactless power transmission / reception system 10 according to the embodiment, the power reception device 30 and the power transmission device 130 communicate with each other through the communication unit 80 and the communication unit 180. Therefore, the power transmission device 130 includes the self-inductance L2 and the impedance RL (or self The ratio of the inductance L2 and the impedance RL (L2 / RL)) may be acquired from the automobile 20 by communication.

  When the coupling coefficient k is obtained, the initial frequency fst of AC power from the inverter 142 is determined based on the coupling coefficient k (step S130). In the embodiment, for the initial frequency fst, when the coupling coefficient k is equal to or greater than a predetermined value, a frequency (for example, Fset-α) that is smaller than the predetermined frequency Fset is set as the initial frequency fst until the power factor becomes very bad. When the coefficient k is less than a predetermined value, a frequency (for example, Fset + α) that is larger than the predetermined frequency Fset until the power factor becomes very bad is set as the initial frequency fst. FIG. 5 shows an example of the relationship among the coupling coefficient k, the frequency f, and the current phase θ. When the coupling coefficient k is large, the current phase θ is retarded as the frequency f decreases. On the other hand, when the coupling coefficient k is small, the current phase θ is retarded as the frequency f increases. Therefore, the reason why the initial frequency fst is set as described above is that when the duty is increased, the current phase θ is retarded with respect to the output voltage and almost no power can be transmitted. When the initial frequency fst is determined, the switching elements Q1 to Q4 are subjected to switching control so that the AC power from the inverter 142 becomes the initial frequency fst.

  Here, the reason why the phase (current phase) θ of the output current from the inverter 142 is advanced or retarded with respect to the output voltage will be described. The power transmission resonance circuit 132 of the power transmission device 130 is designed so that the resonance frequency becomes the predetermined frequency Fset, and the resonance frequency of the power reception resonance circuit 32 of the power reception device 30 mounted on the automobile 20 also becomes the predetermined frequency Fset. Designed to. For this reason, if there is no manufacturing error of parts, and if the power transmission resonance circuit 132 and the power reception resonance circuit 32 at the time of power transmission / reception are accurately in the design position, the current phase θ advances with respect to the output voltage. There is no corner or delay. However, there are manufacturing errors in the components of the power transmission resonance circuit 132 and the power reception resonance circuit 32, and the frequency / phase characteristics vary depending on the individual. For this reason, the phase θ of the output current Is is advanced or retarded with respect to the output voltage. In addition, the positions of the power transmission resonance circuit 132 and the power reception resonance circuit 32 at the time of power transmission / reception are determined by the parking of the automobile 20, and thus are often not designed positions. If the power transmission resonance circuit 132 and the power reception resonance circuit 32 are displaced during power transmission and reception, the coupling coefficient k and the inductance change, and the frequency / phase characteristics change. For this reason, the phase θ of the output current Is is advanced or retarded with respect to the output voltage. Further, when the inverter 142 is converted to AC power by pulse width modulation control, the rising timing of the output voltage changes due to the change of the duty, and thus the output voltage is not changed even though the current waveform has not changed at all. In some cases, the current phase θ is advanced. As for the inconvenience when the phase θ of the output current from the inverter 142 is advanced with respect to the output voltage, as described in detail in “Problems to be Solved by the Invention” in this specification, the inverter 142 is This is because a recovery current flows through the diode D <b> 3 that constitutes a short-circuit current, which may cause a malfunction or failure of the power transmission device 130. Therefore, by determining the initial frequency fst in step S130 such that the current phase θ is retarded with respect to the output voltage, the phase θ of the output current advances with respect to the output voltage when the frequency f and the duty are changed. Inconveniences that may be caused by cornering can be avoided.

  When the initial frequency fst is determined in this way, the duty of the AC power from the inverter 142 is then increased to a predetermined duty (step S140). As the predetermined duty, in the embodiment, a duty slightly smaller than the maximum duty is used. Since the initial frequency fst is determined so that the power factor becomes very bad, almost no power is transmitted even with a large duty.

  Subsequently, the frequency f is changed to the predetermined frequency fset side by a minute frequency Δf until the target power is transmitted (steps S150 and S160). When the frequency f is changed to the predetermined frequency fset side, the current phase θ is advanced and approaches the phase of the output voltage, so that the power factor is improved and electric power is transmitted. Therefore, the processing in steps S150 and S160 is to change the frequency f by a minute amount Δf and transmit the target power.

  When the target power is transmitted, the output current Is is detected from the inverter 142 when the switching element Q1 is turned on (step S170), and the output current Is is set by a negative threshold value Iref and a value 0. It is determined whether it is within the current range (step S180). FIG. 6 shows an example of ON / OFF states of the switching elements Q1 to Q4 of the inverter 142 and temporal changes in the output voltage and output current of the inverter 142. In “Inverter output voltage and current” in the figure, the solid broken line indicates the output voltage, the solid line sine curve indicates the current when the current phase θ is advanced with respect to the output voltage, and the dashed sine curve. Indicates the current when the current phase θ is retarded with respect to the output voltage. As shown in the figure, at time T2 when the switching element Q1 is turned on, when the current phase θ is advanced with respect to the output voltage, the output current Is has a positive value, and the current phase θ is When the angle is retarded, the output current Is takes a negative value. Therefore, the output current Is within the predetermined current range means that the current phase θ is within the predetermined range on the retard side with respect to the output voltage. When the current phase θ is advanced with respect to the output voltage, a solid sine curve state of FIG. 6 is obtained, and current flows as described with reference to FIG. 10 in the “problem to be solved by the invention” in this specification. . That is, current flows as shown in FIG. 10A at time T1 immediately before switching element Q1 (Q91 in FIG. 9) is turned on in FIG. 6, and switching element Q1 (Q91 in FIG. 9) is turned on. Immediately after time T2, a current flows as shown in FIG. A forward bias is applied to the diode D3 (D93 in FIG. 10) at a time T1 immediately before the switching element Q1 is turned on, and a reverse bias is applied at a time T2 immediately after the switching element Q1 is turned on. Therefore, due to the recovery characteristics of the diode, a recovery current flows through the diode D3 (D93 in FIG. 10) as indicated by the thick arrow in FIG. When the current phase θ is retarded with respect to the output voltage (in the case of the sine curve of the broken line in FIG. 6), the current flows as follows. In the time T1 immediately before the switching element Q1 is turned on in FIG. 6, the current is switched from the power line on the power transmission coil side to the on-state switching element Q3, as shown in FIG. It flows through the element Q4 and the diode D4 to the lower power line on the power transmission coil side. In time T2 immediately after the switching element Q1 is turned on in FIG. 6, the current is supplied from the power line on the power transmission coil side via the switching element Q1 in the on state, as shown in FIG. 7B. And flows from the negative bus on the power supply side to the lower power line on the power transmission coil side via the switching element Q4 and the diode D4 in the on state. Since the reverse bias is applied to the diode D3 both at the time T1 immediately before the switching element Q1 is turned on and at the time T2 immediately after the switching element Q1 is turned on, no recovery current flows. Therefore, when the current phase θ is within a predetermined range on the retard side with respect to the output voltage, no recovery current flows through the diode D3, and there is no inconvenience due to this.

  When it is determined in step S180 that the output current Is is not within the predetermined current range, the duty is decreased by the decrease amount Δd (step S190), and the frequency f is set to the predetermined frequency fset side until the target power is transmitted. The process returns to the process of changing the minute frequency Δf (steps S150 and S160). While repeating such processing, if it is determined in step S180 that the output current Is is within the predetermined current range, it is determined that the frequency f and duty at that time are the frequency f and duty suitable for power transmission. The process ends. When such frequency / duty adjustment processing is completed, transmission of target power using the frequency f and duty at that time is continued.

  In the power transmission device 130 in the non-contact power transmission and reception system 10 of the embodiment described above, the output impedance Zs of the inverter 142 is calculated, and the coupling coefficient k is obtained based on the output impedance Zs. Then, the initial frequency fst is set based on the coupling coefficient k, and the duty is set to a predetermined duty. Then, the target power is transmitted through the process of changing the frequency f to the predetermined frequency fset by the minute frequency Δf and the process of reducing the duty by the decrease amount Δd until the target power is transmitted. When the switching element Q1 is turned on, the output current Is of the inverter 142 is repeated until it falls within a predetermined current range set by the negative threshold Iref and the value 0. Then, power transmission is performed using the obtained frequency f and duty. At this time, since the current phase θ is within a predetermined range on the retard side with respect to the output voltage, it is possible to prevent the recovery current from flowing through the diode D3 at the timing when the switching element Q1 is turned on. Thus, the target power can be transmitted using a more appropriate frequency and duty.

  In the power transmission device 130 in the non-contact power transmission / reception system 10 according to the embodiment, it is determined whether or not the output current Is from the inverter 142 when the switching element Q1 is turned on is within a predetermined current range. However, when the output current Is falls within the predetermined current range, it means that the current phase θ falls within the predetermined range on the retard side with respect to the output voltage. Therefore, the current phase θ is detected and the current phase is detected. It may be determined whether θ is within a predetermined range on the retard side with respect to the output voltage.

  In the power transmission device 130 in the non-contact power transmission / reception system 10 according to the embodiment, when the coupling coefficient k is greater than or equal to a predetermined value, a frequency smaller than the predetermined frequency Fset (for example, Fset-α) is set as the initial frequency fst, and the coupling coefficient k is predetermined. When the value is less than the value, a frequency higher than the predetermined frequency Fset (for example, Fset + α) is set as the initial frequency fst. However, the frequency / phase characteristics are slightly different due to individual differences and aging of the power transmission device 130 and the power reception device 30. For this reason, when the coupling coefficient k is in the vicinity of a predetermined value, the design frequency / phase characteristics may differ, and the output current Is from the inverter 142 when turning on the switching element Q1 in the frequency / duty adjustment process described above is A positive value may occur, and the current phase θ may advance with respect to the output voltage. In this case, the frequency / duty adjustment process may be executed again using the opposite frequency (Fset + α in the case of Fset−α, Fset−α in the case of Fset + α) as the initial frequency fst.

  In the embodiment, the power transmission device 130 in the contactless power transmission and reception system 10 including the power reception device 30 and the power transmission device 130 mounted on the automobile 20 has been described. However, the power reception device and power transmission mounted on a vehicle or a moving body other than the vehicle. It is good also as a form of the power transmission apparatus in the non-contact power transmission / reception system which has an apparatus, or a form of the power transmission apparatus in the non-contact power transmission / reception system which has a power reception apparatus and power transmission apparatus incorporated in facilities other than a moving body.

  As mentioned above, although the form for implementing this invention was demonstrated using the Example, this invention is not limited at all to such an Example, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

  The present invention can be used in the manufacturing industry of a power transmission device of a non-contact power transmission / reception system.

  DESCRIPTION OF SYMBOLS 10 Contactless power transmission / reception system, 20 Car, 22 Motor, 24 Inverter, 26 Battery, 28 System main relay, 30 Power receiving device, 31 Power receiving unit, 32 Power receiving resonance circuit, 34 Power receiving coil, 36 Capacitor, 42 Filter, 44 Rectifier, 48 relay, 50 current sensor, 52 voltage sensor, 70 vehicle electronic control unit (vehicle ECU), 80 communication unit, 130 power transmission device, 131 power transmission unit, 132 power transmission resonance circuit, 134 power transmission coil, 136 capacitor, 140 AC / DC converter, 142 inverter, 144 filter, 150 current sensor, 152 voltage detection unit, 154 current sensor, 156 voltage detection unit, 170 power transmission electronic control unit (power transmission ECU), 180 communication unit G, 190 AC power supply, C capacitor, D1-D4, D91-D94 diode, Q1-Q4, Q91-Q94 switching element.

Claims (1)

A power transmission device that transmits power to a power receiving device in a contactless manner,
An inverter having a plurality of switching elements and a plurality of diodes, and converting DC power derived from an external power source into AC power;
A power transmission unit that transmits AC power from the inverter to a power reception unit of the power reception device;
Control means for adjusting the AC power by switching control of a plurality of switching elements of the inverter;
With
The control means calculates a coupling coefficient between the power reception unit and the power transmission unit, sets a frequency different from the operating point frequency as an initial frequency based on the coupling coefficient, and moves from the initial frequency to the operating point frequency side. The target power is transmitted so that the current phase of the output current to the power transmission unit falls within a predetermined range on the retard side with respect to the output voltage by changing the frequency of the power and the duty of the AC power Is a means to determine the frequency and duty.
A power transmission device characterized by that.

Images