JP4442150B2 - Grid-connected inverter device - Google Patents

Description

  The present invention relates to a grid-connected inverter that converts DC power, such as a solar cell or a fuel cell, into AC power having a commercial frequency and injects power into the system.

  In a conventional grid-connected inverter, a resonant capacitor and a switching element are arranged on the primary side of a high-frequency transformer having a core gap, and a zero voltage switching operation of the switching element is realized to reduce loss and noise, The conduction time of the switching element is modulated so that the low frequency component of the output current waveform becomes a sine wave.

  FIG. 8 is a connection diagram showing a configuration of a grid-connected inverter that has been conventionally used. The output power of the DC power source 1 is converted into high frequency power by the first inverter 2 and then transmitted to the secondary side via a high frequency transformer 3 having a gap in the core. The high frequency power generated on the secondary side of the high frequency transformer 3 is converted into direct current or pulsating current by the rectifying means 4, converted into commercial AC power synchronized with the system 6 by the second inverter 5, and injected into the system 6. It is. Here, the first inverter 2 is composed of a high-frequency transformer 3, a switching element 8, and a resonance capacitor 7, and the second inverter 5 is composed of a full bridge with four switching elements Q1 to Q4.

The operation will be described below with reference to the waveform diagram of FIG. The first inverter 2 converts the power of the DC power source 1 into high frequency power. This is realized by the switching element 8 of the first inverter 2 being repeatedly turned on and off. Normally, when the switching element 8 is turned off, the excitation energy accumulated in the high frequency transformer 3 is charged / discharged to / from the resonance capacitor 7 so that the collector-emitter voltage of the switching element 8 has a resonance waveform as shown in FIG. It becomes. Next, zero voltage switching is realized by turning on the switching element 8 during a period in which the collector-emitter voltage becomes zero and a current flows through a diode connected in reverse parallel to the switching element 8. Here, the current flowing through the primary winding of the high frequency transformer is the same as the collector-emitter current when the switching element 8 is on, and the current flowing through the resonance capacitor 7 when the switching element 8 is off. This is a waveform in which a high frequency current component generated inside the first inverter 2 is superimposed on a low frequency current of double frequency. Therefore, the high frequency transformer 3 generates a magnetic flux having a plurality of frequencies substantially proportional to the winding current (see, for example, Patent Document 1).
JP 2000-32751 A

  However, in the above-described conventional configuration, the magnetic flux generated by the current flowing through the primary winding of the high-frequency transformer has a high-frequency component and a commercial double-frequency low-frequency component. Magnetic flux is transmitted through the housing of the magnetic material, and it is necessary to surround the outer periphery with a magnetic material such as iron to reduce the leakage magnetic field to the outside of the device, and there is a problem that there is a limit to miniaturization and weight reduction of the device Had.

  The present invention greatly reduces the low-frequency magnetic field generated from the high-frequency transformer with a simple configuration without adding any parts, even in the case of an inverter circuit configuration in which a commercial double-frequency low-frequency current flows through the high-frequency transformer. An object of the present invention is to provide a grid-connected inverter that can be reduced.

In order to achieve the above object, the grid-connected inverter of the present invention has a DC reactor connected between the input of the first inverter and the DC power supply and is surrounded by a primary winding current of a high-frequency transformer having a core gap. A significant noise reduction effect can be obtained by arranging the DC reactor so that the direction of the magnetic flux generated by the current flowing in the DC reactor is in the direction of canceling out the magnetic flux generated by the high-frequency transformer with respect to the direction of the generated magnetic flux. A grid-connected inverter as described above is provided.

  As described above, according to the present invention, a small and lightweight grid-connected inverter that does not restrict the material and thickness of the casing is provided by canceling out the magnetic fields generated by the DC reactor and the high-frequency transformer. be able to.

According to the first aspect of the present invention, a high-frequency transformer having a core gap for converting DC power to high-frequency power, a switching element connected to one end of the primary winding, and the primary winding are connected in parallel. A first inverter comprising a resonant capacitor, a rectifying means for the output of the secondary winding of the high-frequency transformer, a second inverter for converting the rectified power into power of commercial frequency, and an input of the first inverter and a DC power source A DC reactor connected between them to remove noise, a casing for housing the first inverter, the rectifier, the second inverter, and the DC reactor, and a commercial for generating the DC reactor and By setting the magnetic field having a multiple frequency and the commercial generated by the high-frequency transformer and the magnetic field having the multiple frequency to cancel each other, the first By using a grid-connected inverter device that reduces the low-frequency magnetic field generated from the inverter, magnetic flux leakage to the vicinity can be reduced, and there is no restriction on the material and thickness of the housing, so the overall weight of the device is reduced. Can also be achieved.

  The invention described in claim 2 particularly cancels out magnetic flux generated in the vicinity by making the inner circumference of the DC reactor larger than the outer circumference of the high frequency transformer and covering the high frequency transformer with the DC reactor in the invention described in claim 1. The effect can be enhanced.

  The invention described in claim 3 particularly effectively cancels out the magnetic flux generated from the primary winding by disposing the DC reactor in the vicinity of the primary winding of the high-frequency transformer in the invention described in claim 1. be able to.

  In the invention described in claim 4, in particular, in the invention described in claims 1-3, the non-magnetic material is disposed in the gap between the DC reactor and the high-frequency transformer, so that the high-frequency leakage magnetic flux generated from the high-frequency transformer can be reduced. Therefore, it is possible to reduce the loss of the apparatus.

  The invention described in claim 5 is the DC / DC converter according to any one of claims 1 to 4, in which a magnetic substance is disposed in a gap between one or both of a DC reactor and a high-frequency transformer and the casing. It is possible to prevent the low-frequency magnetic flux that does not cancel out between the magnetic flux generated from the reactor and the high-frequency transformer from leaking outside the apparatus.

  In the invention described in claim 6, in particular, in the inventions described in claims 1 to 5, each of the windings of the DC reactor and the windings on the primary side of the high-frequency transformer are made the same by the low-frequency current. Since the generated magnetic flux density can be made closer, the effect of reducing the low-frequency leakage magnetic flux can be enhanced.

  In the invention described in claim 7, in particular, in the inventions described in claims 1 to 6, the DC reactor core and the high-frequency transformer core are made of the same material, so that each is generated by a low-frequency current. The magnetic flux density can be made substantially equal, and the effect of reducing the low-frequency leakage magnetic flux can be further enhanced.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, in particular, the core gap of each of the direct current reactor and the high frequency transformer where the leakage magnetic flux is concentrated is arranged in the vicinity, so that the low frequency and the high frequency are arranged. In both cases, the leakage magnetic flux can be efficiently reduced.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

Example 1
This embodiment relates to claims 1 and 2. FIG. 1 is a block diagram showing a circuit configuration of a first embodiment of the present invention. Here, the DC power generated by the DC power supply 11 is converted into high-frequency power by the first inverter 12 and then transmitted to the secondary side via the high-frequency transformer 13. The high-frequency power generated on the secondary side of the high-frequency transformer 13 is converted into direct current or pulsating current by the rectifier 14, converted into commercial AC power synchronized with the system 16 by the second inverter 15, and injected into the system 16 It is. Here, the primary winding of the high-frequency transformer 13 and the switching element 18 are connected in series to the input voltage. The second inverter 15 is constituted by a full bridge of four switching elements Q1 to Q4. A DC reactor 19 is connected between the DC power supply 11 and the first inverter 12 to limit the high-frequency current flowing through the DC power supply 11.

  The operation of the grid interconnection inverter configured as described above will be described with reference to the waveform diagram of FIG. 2 and the conceptual diagram of FIG. In the first inverter 12, in one cycle of the switching element 18, the Qa collector-emitter current gradually increases when it is on, and transmits power to the secondary side of the high-frequency transformer 13. When the switching element 18 is turned off, the excitation energy accumulated in the high-frequency transformer 13 charges and discharges the resonance capacitor 17, so that the collector voltage of the first switching element 18 becomes a resonance waveform. Next, the collector voltage reaches zero, the diode disposed in antiparallel with the first switching element 18 is turned on, and the collector voltage is maintained at zero for a certain period. During the period, the first switching element 18 is turned on to perform zero voltage switching. Here, the current flowing through the primary winding of the high-frequency transformer 13 is the same as the collector-emitter current when the switching element 8 is on, and the current flowing through the resonance capacitor 17 when the switching element 8 is off. This is a waveform in which a high frequency current component generated inside the first inverter 2 is superimposed on a commercial double frequency low frequency current. On the other hand, the DC reactor 9 has a waveform in which a high frequency component is superimposed on a commercial double frequency low frequency current. Here, the low-frequency currents flowing through the high-frequency transformer 13 and the DC reactor 19 are substantially the same, and in addition to the high-frequency, the same level of commercial double-frequency magnetic flux is generated. Thus, by either reversing the direction of the windings or arranging them in the vicinity so that the direction of current flow is reversed, the magnetic flux generated from each is effectively canceled out. In addition, it cannot be overemphasized that the cancellation effect of magnetic flux can be heightened by arrange | positioning so that the direct current | flow reactor 19 may cover the whole high frequency transformer 13 as shown in FIG.

  As described above, according to the present embodiment, the low frequency magnetic flux that is particularly difficult to remove noise can be obtained by arranging the DC reactor and the high-frequency transformer generated in the commercial and multiple-frequency magnetic fields to cancel each other. Since an effect can be obtained with an inexpensive configuration against leakage, the material and thickness of the housing are not restricted, and the entire apparatus can be reduced in size and weight.

(Example 2)
This embodiment relates to claim 3. FIG. 4 is a conceptual diagram in the second embodiment of the present invention. 4 is different from the configuration of FIG. 3 in that a DC reactor is disposed in the vicinity of the high-frequency transformer primary winding. Components other than those described above are the same as those in the first embodiment, and a description thereof will be omitted.

  The operation of the grid-connected inverter configured as described above will be described with reference to the conceptual diagram of FIG. The current flowing in the primary winding of the high-frequency transformer 13 has a commercial double frequency component superimposed on the direct current, and only the high-frequency component current flows in the secondary winding. Therefore, the primary winding of the high frequency transformer 13 is a source of the low frequency magnetic field. Therefore, a DC reactor 19 is arranged near the primary winding of the high-frequency transformer 13 to cancel the magnetic flux.

  As described above, according to this embodiment, by arranging the DC reactor in the vicinity of the primary winding of the high-frequency transformer, the low-frequency magnetic flux from the high-frequency transformer can be canceled even with a small DC reactor having a small winding length. Therefore, it is possible to reduce the leakage of the low-frequency magnetic flux with a cheaper configuration.

(Example 3)
This embodiment relates to claim 4. FIG. 5 is a block diagram showing a circuit configuration in the third embodiment of the present invention. 5 is different from the configuration of FIG. 4 in that a nonmagnetic material 20 is disposed in the gap between the high-frequency transformer 13 and the DC reactor 19. Components other than those described above are the same as those in the second embodiment, and a description thereof will be omitted.

  The operation of the grid-connected inverter configured as described above will be described with reference to the conceptual diagram of FIG. Of the magnetic flux generated from the high-frequency transformer 13, most of the high-frequency magnetic flux having a relatively short wavelength generates an eddy current in the non-magnetic body 20 when passing through a non-magnetic body 20 such as aluminum disposed in the vicinity. Since the magnetic flux generated by the eddy current generated in the non-magnetic body becomes a magnetic flux in the direction opposite to the magnetic flux generated from the high-frequency transformer 13, they cancel each other. Therefore, the non-magnetic body 20 prevents the magnetic flux generated by the high-frequency transformer 13 from interlinking with, for example, a magnetic body including iron or a copper winding constituting the DC reactor 19.

  As described above, according to the present embodiment, by disposing a non-magnetic material between the DC reactor and the high-frequency transformer, the leakage of the high-frequency magnetic flux from the device is reduced and a loss is generated in the DC reactor. It is possible to provide a high-efficiency grid-connected inverter without any noise.

Example 4
This embodiment relates to claim 5. FIG. 6 is a block diagram showing a circuit configuration in the fourth embodiment of the present invention. 6 is different from the configuration of FIG. 5 in that a magnetic body 21 is disposed between the DC reactor 19 and the housing 22. Components other than those described above are the same as those in the third embodiment, and a description thereof will be omitted.

  The operation of the grid interconnection inverter configured as described above will be described with reference to the conceptual diagram of FIG. The low-frequency magnetic flux generated by the DC reactor 19 and the high-frequency transformer 13 generally cancels each other. However, since both shapes and geometrical arrangements are usually different, there is a magnetic flux that reaches the vicinity of the housing 22 instead of being completely zero. To do. Here, the magnetic body 21 is arranged between one or both of the DC reactor 19 and the high-frequency transformer 13 and the housing 22, a magnetic path is formed in the vicinity of the housing 22, and a low frequency is formed outside the housing 22. Prevents magnetic flux from leaking.

  As described above, according to the present embodiment, the magnetic material is disposed in the gap between one or both of the DC reactor and the high frequency transformer and the housing, thereby generating the magnetic flux generated from the DC reactor and the high frequency transformer. The low frequency magnetic flux leaking outside the apparatus can be reduced without canceling out with the magnetic flux.

(Example 5)
This embodiment relates to claims 6-8. FIG. 7 is a conceptual diagram showing the configuration of the fifth embodiment of the present invention. 7 is different from the configuration of FIG. 4 in that the number of turns and the core material of the high-frequency transformer 13 and the DC reactor 19 are the same, and the core gaps thereof are arranged close to each other. Components other than those described above are the same as those in the second embodiment, and a description thereof will be omitted.

  The operation of the grid-connected inverter configured as described above will be described with reference to the conceptual diagram of FIG. Since the low-frequency currents flowing through the DC reactor 19 and the high-frequency transformer 13 are substantially the same, the low-frequency magnetic flux generated from each of them is equivalent by making the number of turns and the core material the same. This enhances the cancellation effect and minimizes the low frequency magnetic flux leaking to the outside. Furthermore, since the magnetic flux leaks most in the vicinity of the core gap, the DC reactor 19 and the high-frequency transformer 13 are arranged so that the core gap positions are close to each other and shielded in a place where the magnetic flux density is high, so that the dependence on the respective external shapes To reduce the high frequency and low frequency magnetic flux.

As described above, according to the present embodiment , the number of turns and the core material are made identical and the core gap is arranged close to each other, so that the effect of canceling the magnetic flux generated from the DC reactor and the high frequency transformer is greatly improved, and the leakage magnetic flux is shielded. The effect can be enhanced.

The block diagram which shows the structure of the grid connection inverter which is 1st Example of this invention. The wave form diagram which shows each part operation | movement of the grid connection inverter which is 1st Example of this invention. The conceptual diagram which shows each part operation | movement of the grid connection inverter which is 1st Example of this invention. The conceptual diagram which shows each part operation | movement of the grid connection inverter which is 2nd Example of this invention. The conceptual diagram which shows each part operation | movement of the grid connection inverter which is the 3rd Example of this invention. The conceptual diagram which shows each part operation | movement of the grid connection inverter which is the 4th Example of this invention. The conceptual diagram which shows each part operation | movement of the grid connection inverter which is a 5th Example of this invention. Block diagram showing the configuration of a conventional grid-connected inverter Waveform diagram showing the operation of each part of a conventional grid-connected inverter

DESCRIPTION OF SYMBOLS 11 DC power supply 12 1st inverter 13 High frequency transformer 14 Rectification means 15 2nd inverter 16 System | strain 17 Resonance capacitor 18 Switching element 19 DC reactor 20 Nonmagnetic material 21 Magnetic material 22 Case

Claims (8)

A first inverter comprising a high-frequency transformer having a core gap for converting DC power to high-frequency power, a switching element connected to one end of the primary winding, and a resonant capacitor connected in parallel to the primary winding ; A rectifier for the output of the secondary winding of the high-frequency transformer, a second inverter for converting the rectified power into power at a commercial frequency, and a connection between the input of the first inverter and the DC power source to remove noise. A DC reactor, a housing that houses the first inverter, the rectifier, the second inverter, and the DC reactor, a commercial that the DC reactor generates, and a magnetic field that is a multiple of the frequency, and the high frequency Since the commercial generated by the transformer and the magnetic field of the multiple frequency thereof cancel each other, the low frequency generated from the first inverter is reduced. System interconnection inverter device for reducing waves magnetic field. The grid-connected inverter device according to claim 1, wherein an inner circumference of the DC reactor is made larger than an outer circumference of the high-frequency transformer, and the high-frequency transformer is covered with the DC reactor. 2. The grid-connected inverter device according to claim 1, wherein the DC reactor is disposed in the vicinity of the primary winding of the high-frequency transformer. The grid-connected inverter device according to any one of claims 1 to 3, wherein a non-magnetic material is disposed in a gap between the DC reactor and the high-frequency transformer. 5. The grid-connected inverter device according to claim 1, wherein a magnetic material is disposed in a gap between one or both of a DC reactor and a high-frequency transformer and the housing. The grid-connected inverter device according to any one of claims 1 to 5, wherein the number of windings of the DC reactor and the number of windings on the primary side of the high-frequency transformer are the same. The grid-connected inverter device according to any one of claims 1 to 6, wherein the core of the DC reactor and the material of the core of the high-frequency transformer are the same. The grid-connected inverter device according to any one of claims 1 to 7, wherein a core gap of the DC reactor and a core gap of the high-frequency transformer are arranged in the vicinity.

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