JP2018121464A - Conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of a problem caused by higher harmonics while suppressing a device being large-sized and increase in a cost.SOLUTION: A conversion device of the embodiment, a conversion device for converting three-phase AC voltage output from an AC power supply to single-phase AC voltage, comprises: a plurality of transformers to which the three-phase AC voltage is input; a plurality of converters for converting AC output from the converters to DC; and a plurality of single-phase full-bridge circuits to which DC voltage output from the converters is input. At least two of the transformers have output voltage having voltage values differing from each other. At least two of the transformers have output voltage having phases differing from each other At least two of the single-phase full-bridge circuits have supplied DC voltage having voltage values differing from each other. At least two of the single-phase full-bridge circuits have ignition phases differing from each other. Respective output of the single-phase full-bridge circuits is connected in series in multiple stages. Single-phase AC voltage is output from both ends of the respective output connected in series.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a conversion apparatus.

  In the future, demand for single-phase inverters is expected to increase mainly in the high-frequency field such as non-contact power supply to electric vehicles. When generating the DC voltage supplied to the single-phase inverter from the three-phase AC voltage, a three-phase converter is required. With these three-phase converter and single-phase inverter, the three-phase AC voltage is converted into a single-phase AC voltage. A conversion device for conversion is configured.

  In such a configuration, there is a concern that inductive interference due to harmonics, radio interference, or the like becomes a problem. At present, various countermeasures are being devised for the problem due to such harmonics, but most of those countermeasures are to remove the harmonic voltage by the action of the filter. If an attempt is made to remove harmonics having a relatively low frequency (for example, fifth-order or seventh-order harmonics) due to the action of the filter, the circuit elements constituting the filter become large. Problems such as an increase in cost occur.

JP 2011-036063 A JP 2013-158064 A

  Therefore, a conversion device is provided that can suppress the occurrence of problems due to harmonics while suppressing the increase in size and cost of the device.

  The conversion device of the present embodiment is a conversion device that converts a three-phase AC voltage output from an AC power source into a single-phase AC voltage, a plurality of transformers to which the three-phase AC voltage is input, and those A plurality of converters that convert alternating current output from the plurality of transformers into direct current, and a plurality of single-phase full bridge circuits to which direct current voltages output from the plurality of converters are input. At least two of the plurality of transformers have different output voltage values. At least two of the plurality of transformers have different output voltage phases. At least two of the plurality of single-phase full bridge circuits have different voltage values of the DC voltage supplied to each other. At least two of the plurality of single-phase full bridge circuits have different firing phases. Outputs of a plurality of single-phase full bridge circuits are connected in series in multiple stages. A single-phase AC voltage is output from both ends of each output connected in series.

The figure which shows typically the structure of the non-contact electric power feeder containing the converter concerning one Embodiment A diagram schematically showing the line voltage on the output side of the transformer Diagram showing phase current on the output side of the transformer The figure which shows the waveform of the voltage output from each inverter part typically The figure which shows typically the voltage waveform of each part of a single phase inverter, and the waveform of the voltage and current which appear on the secondary side of a transformer

Hereinafter, an embodiment will be described with reference to the drawings.
A conversion device 1 shown in FIG. 1 is a device that performs conversion from three phases to a single phase, and converts, for example, a three-phase AC voltage output from an AC power source 2 that is a commercial power source into a single-phase AC voltage. The conversion device 1 constitutes a non-contact power supply device 5 together with a transformer 3 and a low-pass filter 4 (hereinafter referred to as LPF 4). The non-contact power supply device 5 is used, for example, for applications that perform non-contact power supply to an electric vehicle.

  Converter 1 includes transformers 6 to 9 to which three-phase AC voltage output from AC power supply 2 is input, converters 10 to 13 that convert AC output from transformers 6 to 9 into DC, and a converter And a single-phase inverter 14 that converts a DC voltage output from 10 to 13 into a single-phase AC voltage.

  The transformers 6 to 9 are three-phase power transformers that input and output three-phase alternating current. The transformers 6 and 7 have a “Y-Δ” connection system in which the primary side is Y-connected and the secondary side is Δ-connected. The transformers 8 and 9 have a “YY” connection system in which the primary side and the secondary side are both Y-connected.

The transformation ratio (turn ratio) of the transformers 6 and 7 is “1: 1”. The transformation ratio (turn ratio) of the transformers 8 and 9 is “1: 3 ^1/2 / 2”. In the following description, “3 ^1/2 ” is also expressed as “√3”. The three-phase (U-phase, V-phase, W-phase) outputs of transformers 6-9 are input to converters 10-13, respectively.

With such a configuration, the U-phase to V-phase line voltage, the V-phase to W-phase line voltage, and the W-phase to U-phase line voltage of the transformers 6 and 7 (hereinafter collectively referred to as line-to-line). Voltage Eac1), U-phase to V-phase line voltage, V-phase to W-phase line voltage, and W-phase to U-phase line voltage of transformers 8 and 9 (hereinafter collectively referred to as line) (Referred to as inter-voltage Eac2) is represented by the following equation (1).
Eac1: Eac2 = 1: √3 / 2 (1)

  Thus, in the present embodiment, the transformers 6 and 7 and the transformers 8 and 9 have different output voltage (line voltage) voltage values. Also, as shown in FIG. 2, the line voltage Eac1 of the transformers 6 and 7 and the line voltage Eac2 of the transformers 8 and 9 have a phase difference of 30 °. In other words, in the present embodiment, the transformers 6 and 7 and the transformers 8 and 9 are different from each other in the phase of the output voltage (line voltage).

Further, with the above configuration, the line current Iac1 of the transformers 6 and 7 and the line current Iac2 of the transformers 8 and 9 have the relationship of the following equation (2).
Iac1: Iac2 = 1: 2 / √3 (2)

  Further, as shown in FIG. 3, the line current Iac1 of the transformers 6 and 7 and the line current Iac2 of the transformers 8 and 9 have a phase difference of 30 °. In FIG. 3, each period marked with “S1, S2,... S6” has a switch corresponding to that sign among the six switches S1 to S6 (described later) constituting the converters 10-13. Represents the period of on time.

  Converters 10 to 13 all convert three-phase alternating current into direct current, and have the same circuit configuration. Therefore, here, the configuration of converter 10 will be described, and the configurations of converters 11 to 13 will be denoted by the same reference numerals as those of converter 10 and description thereof will be omitted.

  The converter 10 includes a rectifier circuit 15, a DC reactor 16, and a capacitor 17. The rectifier circuit 15 has a configuration in which six switches S1 to S6 are connected to form a three-phase full bridge, and full-wave rectifies the three-phase alternating current output from the transformer 6. As the switches S1 to S6, for example, semiconductor switching elements such as power MOSFETs and IGBTs can be used. ON / OFF of the switches S1 to S6 is controlled by the switch control unit 18.

  A series circuit of switches S1 and S2, a series circuit of switches S3 and S4, and a series circuit of switches S5 and S6 are connected between the output power lines 19 and 20 of the rectifier circuit 15, respectively. The interconnection node Nu of the switches S1 and S2 is connected to the U-phase output terminal of the transformer 6. The interconnection node Nv of the switches S3 and S4 is connected to the V-phase output terminal of the transformer 6. The interconnection node Nw of the switches S5 and S6 is connected to the U-phase output terminal of the transformer 6.

  One terminal of the DC reactor 16 is connected to the output power supply line 19, and the other terminal is connected to the output power supply line 20 via the capacitor 17. The DC reactor 16 and the capacitor 17 smooth the pulsating DC voltage output from the rectifier circuit 15. A voltage between terminals of the capacitor 17, that is, a DC voltage output from the converter 10 is supplied to the single-phase inverter 14.

In the above configuration, the relationship between the DC voltage value (first voltage value Edc1) output from the converters 10 and 11 and the DC voltage value (second voltage value Edc2) output from the converters 12 and 13 is as follows. The relationship between the line voltage Eac1 of the transformers 6 and 7 and the line voltage Eac2 of the transformers 8 and 9 is the same as that of the following equation (3).
Edc1: Edc2 = 1: √3 / 2 (3)

The relationship between the output current Idc1 of the converters 10 and 11 and the output current Idc2 of the converters 12 and 13 is similar to the relationship between the line current Iac1 of the transformers 6 and 7 and the line current Iac2 of the transformers 8 and 9. In other words, the following equation (4) is satisfied.
Idc1: Idc2 = 1: 2 / √3 (4)

  The single-phase inverter 14 includes a plurality of inverter units INV1 to INV4. Each of the inverter units INV1 to INV4 is configured as a single-phase full bridge circuit, and converts an input DC voltage into an AC voltage and outputs the AC voltage. In the present embodiment, the inverter units INV1, INV2, INV3, and INV4 correspond to a first full bridge circuit, a second full bridge circuit, a third full bridge circuit, and a fourth full bridge circuit, respectively.

  A DC voltage having a first voltage value Edc1 supplied from the converter 10 via the power supply lines 21 and 22 is input to the inverter unit INV1. The inverter unit INV1 includes four switches S11 to S14. As the switches S11 to S14, for example, semiconductor switching elements such as power MOSFETs and IGBTs can be used.

  A series circuit of switches S11 and S12 and a series circuit of switches S13 and S14 are connected between the power supply lines 21 and 22. The interconnection node N1a of the switches S11 and S12 is an output node on the high potential side of the inverter unit INV1, and the interconnection node N1b of the switches S13 and S14 is an output node on the low potential side of the inverter unit INV1.

  A DC voltage of the first voltage value Edc1 supplied from the converter 11 via the power lines 23 and 24 is input to the inverter unit INV2. The inverter unit INV2 includes four switches S21 to S24. As the switches S21 to S24, the same configuration as the switches S11 to S14 can be adopted.

  A series circuit of switches S21 and S22 and a series circuit of switches S23 and S24 are connected between the power supply lines 23 and 24. The interconnection node N2a of the switches S21 and S22 is an output node on the high potential side of the inverter unit INV2, and the interconnection node N2b of the switches S23 and S24 is an output node on the low potential side of the inverter unit INV2.

  A DC voltage of the second voltage value Edc2 supplied from the converter 12 via the power lines 25 and 26 is input to the inverter unit INV3. The inverter unit INV3 includes four switches S31 to S34. As the switches S31 to S34, the same configuration as the switches S11 to S14 and the like can be adopted.

  Between the power lines 25 and 26, a series circuit of switches S31 and S32 and a series circuit of switches S33 and S34 are connected. The interconnection node N3a of the switches S31 and S32 is an output node on the high potential side of the inverter unit INV3, and the interconnection node N3b of the switches S33 and S34 is an output node on the low potential side of the inverter unit INV3.

  A DC voltage of the second voltage value Edc2 supplied from the converter 13 via the power lines 27 and 28 is input to the inverter unit INV4. The inverter unit INV4 includes four switches S41 to S44. As the switches S41 to S44, the same configuration as that of the switches S11 to S14 can be adopted.

  A series circuit of switches S41 and S42 and a series circuit of switches S43 and S44 are connected between the power supply lines 27 and 28. The interconnection node N4a of the switches S41 and S42 is an output node on the high potential side of the inverter unit INV4, and the interconnection node N4b of the switches S43 and S44 is an output node on the low potential side of the inverter unit INV4.

  Thus, the inverter units INV1 and INV2 and the inverter units INV3 and INV4 have different voltage values of the DC voltage supplied to each other. Specifically, the first voltage value Edc1 that is the voltage value of the DC voltage supplied to the inverter units INV1 and INV2, and the second voltage value Edc2 that is the voltage value of the DC voltage supplied to the inverter units INV3 and INV4, Is the relationship of the above-mentioned formula (3).

  The switch control unit 18 controls on / off of each switch of the inverter units INV1 to INV4. Although detailed timings of ON / OFF of each switch will be described later, the ignition phases of the inverter unit INV1 and the inverter unit INV2 are different from each other. Moreover, the ignition phase of inverter part INV3 and inverter part INV4 becomes the same ignition phase. Moreover, the ignition phases of the inverter unit INV1 and the inverter units INV3 and INV4 are different from each other. Moreover, the ignition phases of the inverter unit INV2 and the inverter units INV3 and INV4 are different from each other.

  In the above configuration, the output node N1b on the low potential side of the inverter unit INV1 is connected to the output node N2a on the high potential side of the inverter unit INV2. The output node N2b on the low potential side of the inverter unit INV2 is connected to the output node N3a on the high potential side of the inverter unit INV3. The output node N3b on the low potential side of the inverter unit INV3 is connected to the output node N4a on the high potential side of the inverter unit INV4.

  Then, an AC voltage output from between the output node N1a on the high potential side of the inverter unit INV1 and the output node N4b on the low potential side of the inverter unit INV4 is applied to the primary winding 3a of the transformer 3. That is, in the single-phase inverter 14 having the above-described configuration, the outputs of the inverter units INV1 to INV4 are connected in series in multiple stages, and an alternating voltage is output from both ends of the serially connected outputs.

  A single-phase AC voltage output from the single-phase inverter 1 is applied to the primary winding 3 a of the transformer 3. In the present embodiment, the transformation ratio of the transformer 3 is “1: 1”, for example. The AC voltage Ehf output from the secondary winding 3b of the transformer 3 is input to the LPF 4. The LPF 4 is configured as an L-type or π-type LC filter including an inductor and a capacitor, for example.

  The LPF 4 is designed so as to block components of the higher order harmonics included in the AC voltage Ehf. In this case, although details will be described later, the lowest order of the harmonics included in the AC voltage Ehf is “11”. Therefore, in the present embodiment, the LPF 4 is designed so as to block higher-order 11th-order harmonic components included in the AC voltage Ehf. The output voltage of the LPF 4 is supplied to a load (not shown) to be fed.

  Next, the operation of the above configuration will be described with reference to FIGS. 4 and FIG. 5, the start point of one cycle of the AC voltage output from the single-phase inverter 14 is set to 0 °, and the end point is set to 360 °. In addition, the vertical axis in FIG. 5 indicates each voltage divided by the voltage Edc1, that is, each voltage normalized by the voltage Edc1.

[1] Operation of Inverter Unit INV1 In one cycle of the AC voltage, on / off of the switches S11 to S14 of the inverter unit INV1 is controlled as follows. That is, from 0 ° to 120 °, the switches S11 and S14 are turned on and the switches S12 and S13 are turned off. In addition, all the switches S11 to S14 are turned off at 120 ° to 180 ° and 300 ° to 360 °. Further, at 180 ° to 300 °, the switches S11 and S14 are turned off and the switches S12 and S13 are turned on.

  By controlling the switches S11 to S14 as described above, an AC voltage as shown in FIG. 4A appears between the output nodes N1a and N1b of the inverter unit INV1. That is, the AC voltage output from the inverter unit INV1 is + Edc1 at 0 ° to 120 °, 0 at 120 ° to 180 °, −Edc1 at 180 ° to 300 °, and 0 at 300 ° to 360 °. .

[2] Operation of Inverter Unit INV2 In one cycle of the AC voltage, on / off of the switches S21 to S24 of the inverter unit INV2 is controlled as follows. That is, all the switches S21 to S24 are turned off at 0 ° to 60 ° and 180 ° to 240 °. Further, at 60 ° to 180 °, the switches S21 and S24 are turned on and the switches S22 and S23 are turned off. Further, at 240 ° to 360 °, the switches S21 and S24 are turned off and the switches S22 and S23 are turned on.

  By controlling the switches S21 to S24 as described above, an AC voltage as shown in FIG. 4B appears between the output nodes N2a and N2b of the inverter unit INV2. That is, the AC voltage output from the inverter unit INV2 is 0 at 0 ° to 60 °, + Edc1 at 60 ° to 180 °, 0 at 180 ° to 240 °, and −Edc1 at 240 ° to 360 °. .

[3] Operation of Inverter Unit INV3 In one cycle of the AC voltage, on / off of the switches S31 to S34 of the inverter unit INV3 is controlled as follows. That is, all the switches S31 to S34 are turned off at 0 ° to 30 ° and 150 ° to 210 °. Further, at 30 ° to 150 °, the switches S31 and S34 are turned on and the switches S32 and S33 are turned off. Further, at 210 ° to 330 °, the switches S31 and S34 are turned off and the switches S32 and S33 are turned on.

  By controlling the switches S31 to S34 as described above, an AC voltage as shown in FIG. 4C appears between the output nodes N3a and N3b of the inverter unit INV3. That is, the AC voltage output from the inverter unit INV3 is 0 at 0 ° to 30 °, + Edc2 at 30 ° to 150 °, 0 at 150 ° to 210 °, and −Edc2 at 210 ° to 330 °. It is 0 at 330 ° to 360 °.

[4] Operation of Inverter Unit INV4 In one cycle of the AC voltage, ON / OFF of the switches S41 to S44 of the inverter unit INV4 is controlled as follows. That is, all the switches S41 to S44 are turned off at 0 ° to 30 ° and 150 ° to 210 °. Further, at 30 ° to 150 °, the switches S41 and S44 are turned on and the switches S42 and S43 are turned off. Further, at 210 ° to 330 °, the switches S41 and S44 are turned off and the switches S42 and S43 are turned on.

  By controlling the switches S41 to S44 as described above, an AC voltage as shown in FIG. 4D appears between the output nodes N4a and N4b of the inverter unit INV4. That is, the AC voltage output from the inverter unit INV4 is 0 at 0 ° to 30 °, + Edc2 at 30 ° to 150 °, 0 at 150 ° to 210 °, and −Edc2 at 210 ° to 330 °. It is 0 at 330 ° to 360 °.

[5] Overall Operation When the inverter units INV1 and INV2 perform the operation as described above, a voltage as shown in FIG. 5A appears between the nodes N1a and N2b. That is, the voltage Ehf1 between the nodes N1a and N2b is 1 at 0 ° to 60 °, 2 at 60 ° to 120 °, 1 at 120 ° to 180 °, −1 at 180 ° to 240 °, 240 It becomes -2 at 300 ° to 300 °, and -1 at 300 ° to 360 °.

  Further, when the inverter units INV3 and INV4 perform the operation as described above, a voltage as shown in FIG. 5B appears between the nodes N3a and N4b. That is, the voltage Ehf2 between the nodes N3a and N4b is 0 at 0 ° to 30 °, √3 at 30 ° to 150 °, 0 at 150 ° to 210 °, and −√3 at 210 ° to 330 °. , 330 ° to 360 ° is zero.

In this case, the effective value of the voltage Ehf1 and the effective value of the voltage Ehf2 are equal to each other as shown in the following equation (5).
Ehf1: Ehf2 = 1: 1 (5)
As shown in FIG. 5 (c), the AC voltage output from the single-phase inverter 14 and the AC voltage Ehf output from the secondary winding 3b of the transformer 3 are steps obtained by combining the voltage Ehf1 and the voltage Ehf2. It becomes a waveform. That is, the AC voltage Ehf is 1 at 0 ° to 30 °, 1 + √3 at 30 ° to 60 °, 2 + √3 at 60 ° to 120 °, 1 + √3 at 120 ° to 150 °, 150 It becomes 1 in the case of ° to 180 °. The AC voltage Ehf is −1 at 180 ° to 210 °, −1 + √3 at 210 ° to 240 °, −2 + √3 at 240 ° to 300 °, and −1 + √ at 300 ° to 330 °. 3 and 1 at 330 ° to 360 °.

  Further, the current Ihf flowing through the secondary winding 3b of the transformer 3 has a waveform in which the waveform of the AC voltage Ehf is blunted by the action of the LPF 4. That is, the current Ihf has a sinusoidal waveform as shown in FIG.

According to this embodiment described above, the following effects can be obtained.
A voltage output from a general single-phase inverter has a rectangular waveform. Such a rectangular wave output voltage includes a large number of harmonic components. In order to remove such a harmonic voltage, a filter having a specification for removing low-order harmonics is necessary, which causes problems such as an increase in the size of the apparatus and an increase in cost. Therefore, the single-phase inverter 1 of the present embodiment includes four inverter units INV1 to INV4 having a configuration similar to that of a general single-phase inverter, and DC voltages supplied to at least two of the inverter units INV1 to INV4. And the ignition phases of at least two of the inverter units INV1 to INV4 are different from each other. The outputs of the four inverter units INV1 to INV4 are connected in series in multiple stages, and an alternating voltage is output from both ends of the serially connected outputs.

  The AC voltage output from the single-phase inverter 1 having such a configuration is a waveform obtained by combining the output voltages of the inverter units INV1 to INV4 shown in FIGS. 4 (a) to 4 (d). It becomes a step-like waveform as shown in c). Such a step-like voltage waveform is a waveform closer to a sine wave than a rectangular wave-like voltage waveform, so that the harmonic component contained therein is reduced. Accordingly, as the LPF 4, a small and inexpensive filter can be used as compared with a filter for removing harmonic components contained in a rectangular wave voltage. Therefore, according to the present embodiment, it is possible to obtain an effect that it is possible to suppress the occurrence of problems due to harmonics while suppressing the increase in size and cost of the apparatus.

The effect of reducing the harmonic component of the AC voltage output from the single-phase inverter 14 becomes more prominent as the number of pulses p of the voltage waveform is increased. The number of pulses p corresponds to the number of commutations that do not occur simultaneously during one cycle of the AC voltage. The harmonic order n included in the AC voltage is expressed by the following equation (6). However, m is a positive integer.
n = p × m ± 1 (6)

Further, the generation amount En of harmonics included in the AC voltage is expressed by the following equation (7), where the magnitude of the fundamental wave is 1.
En = 1 / n (7)

  As is apparent from the above equation (7), when the number of pulses p is 12, the harmonic order n included in the AC voltage is “11, 13, 23, 25,. Harmonics are not included. As is clear from the above equation (3), the generation amount In of the fifth and seventh harmonics is larger than the generation amount En of higher harmonics.

  Therefore, in this embodiment, the voltage value of the DC voltage supplied to the inverter units INV1 to INV4 and the ignition phase of the inverter units INV1 to INV4 are set so that the number of pulses p is 12. Specifically, in this embodiment, the voltage value Edc1 of the DC voltage supplied to the inverter units INV1 and INV2 and the voltage value Edc2 of the DC voltage supplied to the inverter units INV3 and INV4 satisfy the above expression (3). It is set as follows.

  In this embodiment, when the ignition phase of the inverter unit INV1 is used as a reference, the ignition phase of the inverter unit INV2 is delayed by 60 °, and the ignition phases of the inverter units INV3 and INV4 are delayed by 30 °. Thereby, the pulse number p of the AC voltage output from the single-phase inverter 14 becomes 12, and the AC voltage does not include fifth and seventh harmonics. Therefore, the lowest order harmonics included in the AC voltage output from the single-phase inverter 14 is the 11th order, and the LPF 4 only needs to be able to block the 11th order harmonic components. A small and inexpensive filter can be used as compared with a filter capable of blocking seventh-order harmonic components.

  The single-phase inverter 14 includes four inverter units INV1 to INV4 having a configuration similar to that of a general single-phase inverter, and is configured to obtain a desired output by connecting them in series in multiple stages. Therefore, the capacity of each of the inverter units INV1 to INV4 may be about 1/4 of the capacity of a general single-phase inverter that can obtain the same output as the single-phase inverter 14. Therefore, according to the present embodiment, it is possible to obtain the effect of reducing the above-described harmonics without increasing the size of the device or significantly increasing the cost compared to the conventional general single-phase inverter.

  It is also conceivable to employ PWM control as drive control of the switches S11 to S44 of the single-phase inverter 14 in anticipation of the effect of reducing harmonics. However, when PWM control is used, the switching loss may increase. Since the single-phase inverter 14 of this embodiment does not use PWM control, the above-described harmonic reduction effect can be obtained without causing an increase in switching loss.

  The conversion device 1 of the present embodiment includes transformers 6 to 9 and converters 10 to 13 as a configuration for generating a DC voltage to be supplied to the single-phase inverter 14 from a three-phase AC voltage output from the AC power supply 2. I have. In order to obtain the above-described effect by the single-phase inverter 14, it is necessary to vary the voltage values of the DC voltages supplied to at least two of the inverter units INV1 to INV4. Specifically, the voltage value Edc1 of the DC voltage supplied to the inverter units INV1 and INV2 and the voltage value Edc2 of the DC voltage supplied to the inverter units INV3 and INV4 satisfy the relationship of the above expression (3). There is a need to.

  Therefore, by setting specifications such as the wiring method and the transformation ratio of the transformers 6 to 9 as described above, the voltage values of the output voltages of the transformers 6 to 9 are made different from each other, and at least 2 The phases of the output voltages are different from each other. Specifically, in the present embodiment, the line voltage Eac1 of the transformers 6 and 7 and the line voltage Eac2 of the transformers 8 and 9 satisfy the relationship of the above formula (1), and the line voltage Eac1 and line voltage Eac2 have a phase difference of 30 °.

  By doing so, the DC voltage output from the converters 10 and 11, that is, the voltage value Edc1 of the DC voltage supplied to the inverter units INV1 and INV2, and the DC voltage output from the converters 12 and 13, that is, the inverter unit. The voltage value Edc2 of the DC voltage supplied to INV3 and INV4 is a value that satisfies the relationship of the above expression (3).

Further, the harmonic order n included in the current flowing in the AC power supply 2 is expressed by the following equation (8).
n = p × m ± 1 (8)

Furthermore, the harmonic generation amount In contained in the current flowing in the AC power supply 2 is expressed by the following equation (9), where the magnitude of the fundamental wave is 1.
In = 1 / n (9)

  Therefore, in this embodiment, the voltage values and phase shifts of the output voltages (line voltages Eac1, Eac2) of the transformers 6 to 9 are set so that the number of pulses p is 12. If it does in this way, the synthetic | combination current of the primary side of the transformers 6-9 will become a waveform similar to the conventional 12 pulse rectifier circuit. Therefore, according to this embodiment, not only the harmonics on the output side of the converter 1 can be reduced, but also the harmonics on the input side of the converter 1 can be reduced.

(Other embodiments)
The converter 1 is not limited to the use for performing non-contact power feeding to the electric vehicle exemplified in the above embodiment, and can be used for various purposes such as induction heating. That is, the present invention can be applied to all conversion devices that convert a three-phase AC voltage into a single-phase AC voltage. Therefore, the transformer 3, LPF 4 and the like may be provided as necessary.

  In the above embodiment, the outputs of the inverter units INV1 to INV4 are connected in series in multiple stages, and an AC voltage obtained from both ends of the serially connected outputs is applied to the primary side winding 3a of the transformer 3, that is, Although the configuration of multiplexing on the primary side of the transformer 3 was adopted, four transformers having inputs of the outputs of the inverter units INV1 to INV4 are provided, and the outputs (secondary side) of these four transformers are multistage. The configuration may be changed to a configuration in which they are connected in series, that is, a configuration in which they are multiplexed on the secondary side of the transformer.

  The voltage value of the DC voltage supplied to the inverter units INV1 to INV4 and the ignition phase of the inverter units INV1 to INV4 are not limited to those shown in the above embodiment, and the AC voltage output from the single-phase inverter 14 is What is necessary is just to set suitably so that the desired stepped waveform and by extension, the pulse number of an alternating voltage may turn into a desired number. In other words, the voltage values of the DC voltages supplied to at least two of the inverter units INV1 to INV4 may be set different from each other, and at least two firing phases of the inverter units INV1 to INV4 may be set to be different from each other. .

  The inverter units INV3 and INV4 can be replaced with one inverter unit. However, the inverter unit to be replaced requires twice the capacity of the inverter units INV3 and INV4. Further, as the voltage value of the DC voltage supplied to the inverter unit, a voltage value (= √3) twice the voltage value Edc2 of the DC voltage supplied to the inverter units INV3 and INV4 is required. Therefore, in order to cope with such a change, specifications such as the connection method and the transformation ratio of the transformers 6 to 9 may be changed accordingly.

  The single-phase inverter 1 includes four single-phase full-bridge circuits (inverter units INV1 to INV4), and each output is connected in series in multiple stages. However, the number of single-phase full-bridge circuits is 2 There may be three, three or more.

The specifications of the transformers 6 to 9 such as the connection method and the transformation ratio are not limited to those shown in the above embodiment, and the voltage values Edc1 and Edc2 of the DC voltage supplied to the single-phase inverter 14 are the desired voltage values. If it becomes, it can change suitably. For example, it is possible to change the primary side of the transformers 6 to 9 from the Y connection to the Δ connection. That is, the transformers 6 and 7 can be set to the “Δ-Δ” connection method, and the transformers 8 and 9 can be set to the “Δ-Y” connection method.
The six switches S1 to S6 of the converters 10 to 13 can be replaced with rectifying elements such as diodes.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  In the drawings, 1 is a conversion device, 2 is an AC power supply, 4 is a low-pass filter, 6 to 9 are transformers, 10 to 13 are converters, INV1 is an inverter unit (single-phase full-bridge circuit, first full-bridge circuit), INV2 Is an inverter unit (single phase full bridge circuit, second full bridge circuit), INV3 is an inverter unit (single phase full bridge circuit, third full bridge circuit), and INV4 is an inverter unit (single phase full bridge circuit, fourth full bridge circuit). Circuit).

Claims (5)

A conversion device that converts a three-phase AC voltage output from an AC power source into a single-phase AC voltage,
A plurality of transformers to which the three-phase AC voltage is input;
A plurality of converters for converting alternating current output from the plurality of transformers into direct current;
A plurality of single-phase full bridge circuits to which DC voltages output from the plurality of converters are input;
At least two of the plurality of transformers have different output voltage values,
At least two of the plurality of transformers have different output voltage phases from each other,
At least two of the plurality of single-phase full bridge circuits have different voltage values of the DC voltage supplied to each other,
At least two of the plurality of single-phase full bridge circuits have different firing phases from each other,
Each output of the plurality of single-phase full bridge circuits is connected in series in multiple stages,
A converter that outputs a single-phase AC voltage from both ends of each of the series-connected outputs. If the harmonic order is n, the number of pulses is p, and the positive integer is m,
The harmonic order n included in the current flowing in the AC power supply is expressed by the following equation: n = p × m ± 1
Assuming that the fundamental wave magnitude is 1 and the harmonic generation amount In contained in the current flowing in the AC power supply is expressed by the following formula: In = 1 / n
The converter according to claim 1, wherein a voltage value and a phase of the output voltage of the transformer are set so as to satisfy the above. If the harmonic order is n, the number of pulses is p, and the positive integer is m,
The harmonic order n included in the single-phase AC voltage is expressed by the following equation: n = p × m ± 1
Assuming that the fundamental wave size is 1 and the harmonic generation amount En included in the single-phase AC voltage is expressed by the following formula: En = 1 / n
The converter according to claim 1 or 2, wherein a voltage value of the DC voltage and the ignition phase are set so as to satisfy the above.   4. The conversion device according to claim 1, further comprising a low-pass filter that blocks a component of a harmonic higher than the lowest order included in the single-phase AC voltage. 5. The plurality of single-phase full bridge circuits are a first full bridge circuit, a second full bridge circuit, a third full bridge circuit, and a fourth full bridge circuit,
The voltage value of the DC voltage supplied to the first full bridge circuit and the second full bridge circuit is a first voltage value,
The voltage value of the DC voltage supplied to the third full bridge circuit and the fourth full bridge circuit is a second voltage value different from the first voltage value,
The firing phases of the first full bridge circuit and the second full bridge circuit are firing phases different from each other;
5. The conversion device according to claim 1, wherein the ignition phases of the third full bridge circuit and the fourth full bridge circuit are the same ignition phase. 6.

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