JP2013172562A - Inverter device, inverter system, and photovoltaic power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a ripple current inputted to a capacitor constituting an inverter circuit increases and this may cause an increase in electric energy loss in the capacitor.SOLUTION: An inverter device comprises: a capacitor group that has a first capacitor and a second capacitor connected in series to each other, is connected in parallel to a DC power supply, and in which a potential of a first connection point between the first capacitor and the second capacitor indicates a neutral potential; a first switch group that has a first switch and a second switch connected in series to each other, and is connected in parallel to the capacitor group; a third capacitor that has one terminal connected to a second connection point between the first switch and the second switch; and sinusoidal-voltage generating means that is connected to the third capacitor and outputs a sinusoidal voltage by chopping the DC voltage charged in the first capacitor and the second capacitor with the first switch group.

Description

  The present invention relates to an inverter device, an inverter system, and a photovoltaic power generation system.

A power conditioner is a device that converts DC power from a solar cell into AC power by turning on and off a plurality of switches that constitute an inverter circuit. Patent Literature 1 and Patent Literature 2 propose a power conditioner that improves the efficiency of conversion from DC power to AC power by reducing switching loss due to switches of the inverter circuit.
Patent Document 1 Japanese Patent Application Laid-Open No. 2010-220320 Patent Document 2 Japanese Patent Application Laid-Open No. 2010-220321

  In such a power conditioner, the ripple current generated by the switching operation of the switches constituting the inverter circuit increases, and the electrical energy loss in the capacitor constituting the inverter circuit may increase.

  An inverter device according to an aspect of the present invention includes a first capacitor and a second capacitor connected in series, and is connected in parallel to a DC power supply, and a first connection point between the first capacitor and the second capacitor. A capacitor group having a neutral potential, a first switch and a second switch connected in series, a first switch group connected in parallel with the capacitor group, a first switch and a second switch, A sine wave is obtained by chopping together with the first switch group a third capacitor having one end connected to the second connection point, and a DC voltage connected to the third capacitor and charged to the first capacitor and the second capacitor. Sine wave voltage generating means for outputting a voltage.

  The sine wave voltage generating means includes a third switch and a fourth switch connected in series, a second switch group connected in parallel with the third capacitor, and a fifth switch and a sixth switch connected in series. A third switch group in which a fourth connection point of the fifth switch and the sixth switch is connected to a third connection point of the third switch and the fourth switch, and is connected in parallel with the third switch group. A fourth capacitor, a seventh switch and an eighth switch connected in series, a fourth switch group connected in parallel with the fourth capacitor, a first switch, a second switch, a third switch, By turning on / off the 4 switch, the 5th switch, the 6th switch, the 7th switch, and the 8th switch, the DC voltage from the DC power source is converted into the AC voltage, and the 7th switch and the 8th switch 5 Comprising a switch controller for outputting an AC voltage from the attachment point, and a smoothing circuit for smoothing the pulse waveform of the AC voltage.

  In the above inverter device, the switch control unit turns on the first switch, turns off the second switch, turns off the third switch, turns on the fourth switch, turns off the fifth switch, and turns on the sixth switch. After alternately turning on and off the seventh switch and the eighth switch, the first switch is turned on, the second switch is turned off, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned on, and the sixth switch is turned on In an off state, the seventh switch and the eighth switch may be turned on and off alternately.

  In the above inverter device, the switch control unit turns on the first switch, turns off the second switch, turns on the third switch, turns off the fourth switch, turns on the fifth switch, and turns off the sixth switch. After alternately turning on and off the seventh switch and the eighth switch, the first switch is turned on, the second switch is turned off, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned off, and the sixth switch is turned on In the on state, the seventh switch and the eighth switch may be alternately turned on and off.

  In the above inverter device, the switch control unit turns on the first switch, turns off the second switch, turns on the third switch, turns off the fourth switch, turns off the fifth switch, and turns on the sixth switch. After alternately turning on and off the seventh switch and the eighth switch, the first switch is turned on, the second switch is turned off, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned on, and the sixth switch is turned on In an off state, the seventh switch and the eighth switch may be turned on and off alternately.

  In the above inverter device, the switch control unit turns on the first switch, turns off the second switch, turns on the third switch, turns off the fourth switch, turns on the fifth switch, and turns off the sixth switch. After alternately turning on and off the seventh switch and the eighth switch, the first switch is turned on, the second switch is turned off, the third switch is turned off, the fourth switch is turned on, the fifth switch is turned off, and the sixth switch is turned on In the on state, the seventh switch and the eighth switch may be alternately turned on and off.

  In the above inverter device, the switch control unit turns on the first switch, turns off the second switch, turns off the third switch, turns on the fourth switch, turns off the fifth switch, and turns on the sixth switch. After the seventh switch and the eighth switch are turned on and off alternately, the first switch is turned on, the second switch is turned off, the third switch is turned off, the fourth switch is turned on, the fifth switch is turned on, and the sixth switch is turned off. In this state, the seventh switch and the eighth switch may be turned on and off alternately.

  In the inverter device, the switch control unit turns on the first switch, turns off the second switch, turns off the third switch, turns on the fourth switch, turns on the fifth switch, and turns off the sixth switch. After the 7th switch and the 8th switch are turned on and off alternately, the first switch is turned off, the second switch is turned on, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned off, and the sixth switch is turned on In this state, the seventh switch and the eighth switch may be turned on and off alternately.

  In the above inverter device, the switch control unit turns off the first switch, turns on the second switch, turns on the third switch, turns off the fourth switch, turns off the fifth switch, and turns on the sixth switch. After alternately turning on and off the seventh switch and the eighth switch, the first switch is turned off, the second switch is turned on, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned on, and the sixth switch is turned on In an off state, the seventh switch and the eighth switch may be turned on and off alternately.

  In the above inverter device, the switch control unit turns off the first switch, turns on the second switch, turns on the third switch, turns off the fourth switch, turns on the fifth switch, and turns off the sixth switch. After the seventh switch and the eighth switch are alternately turned on and off, the first switch is turned off, the second switch is turned on, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned off, and the sixth switch is turned on In the on state, the seventh switch and the eighth switch may be alternately turned on and off.

  In the above inverter device, the switch control unit turns off the first switch, turns on the second switch, turns on the third switch, turns off the fourth switch, turns off the fifth switch, and turns on the sixth switch. After the seventh switch and the eighth switch are alternately turned on and off, the first switch is turned on, the second switch is turned off, the third switch is turned off, the fourth switch is turned on, the fifth switch is turned on, and the sixth switch is turned on In an off state, the seventh switch and the eighth switch may be turned on and off alternately.

  The inverter device further includes a voltage measuring unit that measures the voltage of the DC power source and a second voltage measuring unit that measures the AC voltage of the system power source, and the switch control unit includes the voltage of the DC power source and the AC power of the system power source. A period during which the second switch and the third switch are turned on may be determined based on the voltage.

  The inverter device further includes a third voltage measuring unit that measures a voltage of the third capacitor, and the switch control unit turns the third switch from off to on and the fourth switch from on to off, and then turns the third switch on. The period from turning on to off and turning on the fourth switch from off to on may be determined based on the voltage of the third capacitor.

  The inverter device further includes a fourth voltage measurement unit that measures the voltage of the fourth capacitor, and the switch control unit turns the first switch and the fourth switch from on to off, and the second switch and the third switch from off to on. Then, a period from when the first switch and the fourth switch are turned on to off and when the second switch and the third switch are turned on from off may be determined based on the voltage of the fourth capacitor.

  In the inverter device, the first connection point may be a reference potential.

  The inverter system which concerns on 1 aspect of this invention is connected in parallel with respect to the 1st inverter apparatus which is the said inverter apparatus, and the positive side of a 1st capacitor | condenser, and the negative side of a 2nd capacitor | condenser, a 1st capacitor | condenser and a 2nd capacitor | condenser The second inverter device and the third inverter device that output a sine wave voltage by chopping the DC voltage charged to the first inverter device, and the respective outputs of the first inverter device, the second inverter device, and the third inverter device are starred. Connect by wire connection and output three-phase AC.

  The inverter system which concerns on 1 aspect of this invention is connected in parallel with respect to the 1st inverter apparatus which is the said inverter apparatus, and the positive side of a 1st capacitor | condenser, and the negative side of a 2nd capacitor | condenser, a 1st capacitor | condenser and a 2nd capacitor | condenser And a second inverter device that outputs a sine wave voltage by chopping the DC voltage charged to each other, the outputs of the first inverter device and the second inverter device are connected by V connection, and the connection point of V connection Are connected to the first connection point of the first inverter device, and the connection point of the V connection is set as a reference potential, thereby outputting a three-phase alternating current.

  The photovoltaic power generation system which concerns on 1 aspect of this invention is equipped with a solar cell and said inverter apparatus which converts the DC voltage from a solar cell into an alternating voltage.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is a figure which shows the circuit structure of the power conditioner which concerns on this embodiment. It is a time chart which shows the ON / OFF state of each switch, and the figure which shows the mode of the change of the voltage on the circuit which comprises a power conditioner. It is a figure which shows the condition of the ON / OFF of each switch in each period, and the voltage of the 5th connection point in each period. It is a figure which shows the relationship between the voltage of DC power supply, and the effective current value input into a 3rd capacitor | condenser. An example of the inverter system at the time of applying the power conditioner which concerns on this embodiment to the three-phase four-wire type power supply is shown. An example of the inverter system at the time of applying the power conditioner which concerns on this embodiment to the three-phase three-wire type power supply is shown.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a diagram illustrating a circuit configuration of a power conditioner 100 according to the present embodiment. The power conditioner 100 is used for a solar power generation system, for example. The power conditioner 100 is an example of an inverter device. The power conditioner 100 is connected to a DC power supply 110 and a system power supply 120. The DC power source 110 is a solar cell, for example. The power conditioner 100 converts a DC voltage from the DC power supply 110 into an AC voltage, and performs a grid-operated operation with the system power supply 120. In the present embodiment, the power conditioner 100 is applied to a single-phase two-wire power source. However, the power conditioner 100 can be applied to a single-phase three-wire system, a three-phase three-wire system, or a three-phase four-wire power source.

  The power conditioner 100 includes a capacitor group 10, a first switch group 20, a third capacitor 30, a second switch group 40, a third switch group 50, a fourth capacitor 60, a fourth switch group 70, and a smoothing circuit 80. . Capacitor group 10 includes a first capacitor 12 and a second capacitor 14 connected in series. The capacitor group 10 is connected in parallel with the DC power source 110 and smoothes the DC voltage from the DC power source 110. One end of the first capacitor 12 is connected to the positive electrode of the DC power supply 110, and the other end of the first capacitor 12 is connected to one end of the second capacitor 14. The other end of the second capacitor 14 is connected to the negative electrode of the DC power supply 110. Furthermore, the potential at the first connection point 16 between the first capacitor 12 and the second capacitor 14 is a neutral potential. A first connection point 16 between the first capacitor 12 and the second capacitor 14 is connected to a ground that is a reference potential. The capacitor group 10 may be configured by connecting three or more capacitors in series. In this case, the capacitor group 10 preferably has a connection point indicating an intermediate potential of the voltage input to the power conditioner 100, and a ground is preferably connected to the connection point. A circuit including the second switch group 40, the third switch group 50, the fourth capacitor 60, the fourth switch group 70, and the smoothing circuit 80 generates a DC voltage charged in the first capacitor 12 and the second capacitor 14. This is an example of a sine wave voltage generating means for outputting a sine wave voltage by chopping together with the first switch group 20. The inverter circuit 300 including the first switch group 20, the third capacitor 30, the second switch group 40, the third switch group 50, the fourth capacitor 60, the fourth switch group 70, and the smoothing circuit 80 includes the first capacitor It is an example of an inverter device that outputs a sine wave voltage by chopping a DC voltage charged in a second capacitor.

  In the power conditioner 100 according to the present embodiment, the first connection point 16 is connected to the ground, and one end of a capacitor connected to the negative electrode of the DC power supply 110 is connected to the ground. It differs from the power conditioner described in Patent Document 2. Further, the switch conditions of the first switch group 20 and the second switch group 40 are different from the power conditioners described in Patent Document 1 and Patent Document 2. Thereby, according to this embodiment, the ripple current input into the 3rd capacitor | condenser 30 can be decreased compared with the power conditioner described in patent document 1 and patent document 2. FIG. Therefore, for example, the capacity of the third capacitor 30 can be reduced as compared with the power conditioners described in Patent Document 1 and Patent Document 2. Thereby, size reduction or cost reduction of the power conditioner 100 can be achieved. Furthermore, since electric energy loss in the third capacitor 30 can be suppressed, heat generation in the third capacitor 30 can be suppressed. Since the present embodiment is an example in which the power conditioner 100 is connected to a single-phase two-wire power source, the first connection point 16 is connected to the ground that is the reference potential. However, when the power conditioner 100 is connected to a three-phase three-wire power source or a three-phase four-wire power source, the first connection point 16 may not be connected to the ground that is the reference potential.

  The first switch group 20 includes a first switch 22 and a second switch 24 connected in series. The first switch group 20 is connected in parallel with the capacitor group 10. The first switch 22 and the second switch 24 include, for example, switch elements such as a MOS field effect transistor and an insulated gate bipolar transistor (IGBT). The first switch 22 and the second switch 24 include a diode connected in antiparallel to the switch element. One end of the first switch 22 is connected to one end of the first capacitor 12, and the other end of the first switch 22 is connected to one end of the second switch 24. The other end of the second switch 24 is connected to the other end of the second capacitor 14.

  One end of the third capacitor 30 is connected to a second connection point 26 between the first switch 22 and the second switch 24. The second switch group 40 includes a third switch 42 and a fourth switch 44 connected in series. The second switch group 40 is connected in parallel with the third capacitor 30. The third switch 42 and the fourth switch 44 include, for example, switch elements such as a MOS field effect transistor and an insulated gate bipolar transistor (IGBT). The third switch 42 and the fourth switch 44 include a diode connected in antiparallel to the switch element.

  The third switch group 50 includes a fifth switch 52 and a sixth switch 54. A fourth connection point 56 between the fifth switch 52 and the sixth switch 54 is connected to a third connection point 46 between the third switch 42 and the fourth switch 44. The fifth switch 52 and the sixth switch 54 include, for example, switch elements such as a MOS field effect transistor and an insulated gate bipolar transistor (IGBT). The fifth switch 52 and the sixth switch 54 include a diode connected in antiparallel to the switch element.

  The fourth capacitor 60 is connected in parallel with the third switch group 50. The fourth switch group 70 is connected in parallel with the fourth capacitor 60. The fourth switch group 70 includes a seventh switch 72 and an eighth switch 74 connected in series. The seventh switch 72 and the eighth switch 74 include switch elements such as a MOS field effect transistor and an insulated gate bipolar transistor (IGBT), for example. The seventh switch 72 and the eighth switch 74 include a diode connected in antiparallel to the switch element.

  The switch control unit 90 controls on / off of the first switch 22, the second switch 24, the third switch 42, the fourth switch 44, the fifth switch 52, the sixth switch 54, the seventh switch 72, and the eighth switch 74. Thus, the DC voltage from the DC power supply 110 is converted into an AC voltage, and the AC voltage is output from the fifth connection point 76 between the seventh switch 72 and the eighth switch 74. The smoothing circuit 80 includes a coil 82 and a fifth capacitor 84. One end of the coil 82 is connected to the fifth connection point 76, and the other end of the coil 82 is connected to one end of the fifth capacitor 84. One end of the fifth capacitor 84 is connected to the positive electrode of the system power supply 120. The other end of the fifth capacitor 84 is connected to the ground.

  The first voltage sensor 32 measures the input voltage input to the power conditioner 100, that is, the voltage Vd1 of the DC power supply 110. The second voltage sensor 34 measures the AC voltage output from the power conditioner 100. The third voltage sensor 36 measures the voltage Vd2 of the third capacitor 30. The fourth voltage sensor 38 measures the voltage Vd3 of the fourth capacitor 60. The switch control unit 90 is based on voltage information acquired from the first voltage sensor 32 and the second voltage sensor 34, and the first switch 22, the second switch 24, the third switch 42, the fourth switch 44, and the fifth switch 52. By controlling on / off of the sixth switch 54, the seventh switch 72, and the eighth switch 74, the DC voltage from the DC power supply 110 is changed to an AC voltage synchronized with the phase of the reference AC voltage output from the system power supply 120. Convert it.

  FIG. 2 is a time chart showing the on / off state of each switch and how the voltages V1, V2, V3a, V3b, and V4 change at a plurality of points on the circuit constituting the power conditioner. In FIG. 2, the curves indicated by reference numerals 200 and 202 indicate the voltage waveform of the reference AC voltage that the power conditioner 100 should output. FIG. 3 is a diagram showing the on / off conditions of each switch in each period and the voltage V4 at the fifth connection point 76 in each period.

  In each of the period T1 to the period T10 as illustrated in FIG. 2, the switch control unit 90 performs the first switch 22, the second switch 24, the third switch 42, and the fourth switch 44 according to the on / off condition as illustrated in FIG. The fifth switch 52, the sixth switch 54, the seventh switch 72, and the eighth switch 74 are turned on / off to convert the DC voltage from the DC power supply 110 into an AC voltage.

  In the period T1, the switch controller 90 turns on the first switch 22, turns off the second switch 24, turns off the third switch 42, turns on the fourth switch 44, turns off the fifth switch 52, and turns on the sixth switch 54. In a state in which is turned on, the seventh switch 72 and the eighth switch 74 are alternately turned on and off. Here, the first switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned off, the fourth switch 44 is turned on, the fifth switch 52 is turned off, and the sixth switch 54 is turned on. When the seventh switch 72 is on and the eighth switch 74 is off, the potential at the fifth connection point 76 is the voltage Vd3 of the fourth capacitor 60. On the other hand, the seventh switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned off, the fourth switch 44 is turned on, the fifth switch 52 is turned off, and the sixth switch 54 is turned on. When the switch 72 is off and the eighth switch 74 is on, the potential at the fifth connection point 76 is the ground voltage GND. Therefore, in the period T1, a voltage having a pulse waveform that alternately repeats the voltage Vd3 of the fourth capacitor 60 and the ground voltage GND is output from the fifth connection point 76.

  Subsequently, in the period T1, the switch control unit 90 turns on the first switch 22, turns off the second switch 24, turns off the third switch 42, turns on the fourth switch 44, turns off the fifth switch 52, and After the sixth switch 54 is turned on, the seventh switch 72 and the eighth switch 74 are alternately turned on and off, and then in the period T2, the first switch 22 is turned on, the second switch 24 is turned off, and the third switch 42 is turned on. The seventh switch 72 and the eighth switch 74 are alternately turned on and off with the fourth switch 44 turned off, the fifth switch 52 turned on, and the sixth switch 54 turned off. With the first switch 22 on, the second switch 24 off, the third switch 42 on, the fourth switch 44 off, the fifth switch 52 on, and the sixth switch 54 off, the seventh switch 72 Is ON and the eighth switch 74 is OFF, the potential of the fifth connection point 76 is half the potential Vd1 of the DC power source 110, that is, the potential of one end of the first capacitor 12 connected to the positive electrode of the DC power source 110. The voltage is Vd1 / 2. On the other hand, the seventh switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned on, the fourth switch 44 is turned off, the fifth switch 52 is turned on, and the sixth switch 54 is turned off. When the switch 72 is off and the eighth switch 74 is on, the potential at the fifth connection point 76 is a voltage Vb1 / 2−Vb3 obtained by subtracting the voltage Vb3 of the fourth capacitor 60 from the voltage Vd1 / 2. Therefore, a voltage having a pulse waveform that alternately repeats the voltage Vd1 / 2 and the voltage Vb1 / 2−Vb3 is output from the fifth connection point 76 in the period T2.

  In the period T2, the switch control unit turns on the first switch 22, turns off the second switch 24, turns on the third switch 42, turns off the fourth switch 44, turns on the fifth switch 52, and turns on the sixth switch. In the state where 54 is turned off, the seventh switch 72 and the eighth switch 74 are alternately turned on and off, and then in the period T3, the first switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned on, With the fourth switch 44 turned off, the fifth switch 52 turned off, and the sixth switch 54 turned on, the seventh switch 72 and the eighth switch 74 are turned on and off alternately. With the first switch 22 on, the second switch 24 off, the third switch 42 on, the fourth switch 44 off, the fifth switch 52 off, and the sixth switch 54 on, the seventh switch 72 Is on and the eighth switch 74 is off, the potential at the fifth connection point 76 is a voltage Vb1 / 2 + Vd3 obtained by adding the voltage Vb3 of the fourth capacitor 60 to the voltage Vd1 / 2. On the other hand, the seventh switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned on, the fourth switch 44 is turned off, the fifth switch 52 is turned off, and the sixth switch 54 is turned on. When the switch 72 is off and the eighth switch 74 is on, the potential at the fifth connection point 76 is the voltage Vd1 / 2. Therefore, in the period T3, a voltage having a pulse waveform that alternately repeats the voltage Vb1 / 2 + Vd3 and the voltage Vd1 / 2 is output from the fifth connection point 76.

  Further, the switch control unit 90 turns on the first switch 22, turns off the second switch 24, turns on the third switch 42, turns off the fourth switch 44, turns off the fifth switch 52, and turns off the sixth switch 52 in the period T3. In a state where the switch 54 is turned on, the seventh switch 72 and the eighth switch 74 are alternately turned on and off, and then in the period T4, the first switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned on, With the fourth switch 44 turned off, the fifth switch 52 turned on, and the sixth switch 54 turned off, the seventh switch 72 and the eighth switch 74 are alternately turned on and off. With the first switch 22 on, the second switch 24 off, the third switch 42 on, the fourth switch 44 off, the fifth switch 52 on, and the sixth switch 54 off, the seventh switch 72 Is turned on and the eighth switch 74 is turned off, the potential of the fifth connection point 76 becomes the voltage Vd1 / 2. On the other hand, the seventh switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned on, the fourth switch 44 is turned off, the fifth switch 52 is turned on, and the sixth switch 54 is turned off. When the switch 72 is turned off and the eighth switch 74 is turned on, the potential at the fifth connection point 76 becomes a voltage Vb1 / 2−Vb3 obtained by subtracting the voltage Vb3 of the fourth capacitor 60 from the voltage Vd1 / 2. Therefore, in the period T4, a voltage having a pulse waveform that alternately repeats the voltage Vd1 / 2 and the voltage Vb1 / 2-Vb3 is output from the fifth connection point 76.

  In the period T4, the switch control unit 90 turns on the first switch 22, turns off the second switch 24, turns on the third switch 42, turns off the fourth switch 44, turns on the fifth switch 52, and After the switch 54 is turned off, the seventh switch 72 and the eighth switch 74 are alternately turned on and off, and then in the period T5, the first switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned off, With the fourth switch 44 turned on, the fifth switch 52 turned off, and the sixth switch 54 turned on, the seventh switch 72 and the eighth switch 74 are alternately turned on and off. With the first switch 22 on, the second switch 24 off, the third switch 42 off, the fourth switch 44 on, the fifth switch 52 off, and the sixth switch 54 on, the seventh switch 72 Is turned on and the eighth switch 74 is turned off, the potential of the fifth connection point 76 becomes the voltage Vb3. On the other hand, the seventh switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned off, the fourth switch 44 is turned on, the fifth switch 52 is turned off, and the sixth switch 54 is turned on. When the switch 72 is turned off and the eighth switch 74 is turned on, the potential at the fifth connection point 76 becomes the ground voltage GND. Therefore, in the period T <b> 5, a voltage having a pulse waveform that alternately repeats the voltage Vb <b> 3 and the voltage GND is output from the fifth connection point 76.

  In the period T5, the switch control unit 90 turns on the first switch 22, turns off the second switch 24, turns off the third switch 42, turns on the fourth switch 44, turns off the fifth switch 52, and turns on the sixth switch 54. In a state in which the seventh switch 72 and the eighth switch 74 are alternately turned on and off, in the period T6, the first switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned off, and the fourth switch is turned on. With the switch 44 turned on, the fifth switch 52 turned on, and the sixth switch 54 turned off, the seventh switch 72 and the eighth switch 74 are alternately turned on and off. With the first switch 22 on, the second switch 24 off, the third switch 42 off, the fourth switch 44 on, the fifth switch 52 on and the sixth switch 54 off, When ON and the eighth switch 74 is turned OFF, the potential of the fifth connection point 76 becomes the ground voltage GND. On the other hand, with the first switch 22 on, the second switch 24 off, the third switch 42 off, the fourth switch 44 on, the fifth switch 52 on, and the sixth switch 54 off, When 72 is turned off and the eighth switch 74 is turned on, the potential of the fifth connection point 76 is a voltage −Vd3 indicating the potential of the other end of the fourth capacitor 60. Therefore, in the period T <b> 6, a voltage having a pulse waveform that alternately repeats the voltage GND and the voltage −Vd <b> 3 is output from the fifth connection point 76.

  In the period T6, the switch control unit 90 turns on the first switch 22, turns off the second switch 24, turns off the third switch 42, turns on the fourth switch 44, turns on the fifth switch 52, and turns on the sixth switch 54. After the seventh switch 72 and the eighth switch 74 are turned on and off alternately in the off state, the first switch 22 is turned off, the second switch 24 is turned on, the third switch 42 is turned on, and the fourth switch is turned on in the period T7. With the switch 44 turned off, the fifth switch 52 turned off, and the sixth switch 54 turned on, the seventh switch 72 and the eighth switch 74 are alternately turned on and off. With the first switch 22 off, the second switch 24 on, the third switch 42 on, the fourth switch 44 off, the fifth switch 52 off, and the sixth switch 54 on, the seventh switch 72 When the eighth switch 74 is turned off, the potential of the fifth connection point 76 is a voltage obtained by adding the voltage Vd3 of the fourth capacitor 60 to the voltage −Vd1 / 2 indicating the potential of the other end side of the second capacitor 14. −Vd1 / 2 + Vd3. On the other hand, the seventh switch 22 is turned off, the second switch 24 is turned on, the third switch 42 is turned on, the fourth switch 44 is turned off, the fifth switch 52 is turned off, and the sixth switch 54 is turned on. When the switch 72 is turned off and the eighth switch 74 is turned on, the potential of the fifth connection point 76 becomes a voltage −Vd1 / 2 indicating the potential on the other end side of the second capacitor 14. Therefore, in the period T7, a voltage having a pulse waveform that alternately repeats the voltage −Vd1 / 2 + Vd3 and the voltage −Vd1 / 2 is output from the fifth connection point 76.

  In the period T7, the switch control unit 90 turns off the first switch 22, turns on the second switch 24, turns on the third switch 42, turns off the fourth switch 44, turns off the fifth switch 52, and turns on the sixth switch 54. In a state in which the seventh switch 72 and the eighth switch 74 are alternately turned on and off, in the period T8, the first switch 22 is turned off, the second switch 24 is turned on, the third switch 42 is turned on, In a state where the switch 44 is turned off, the fifth switch 52 is turned on, and the sixth switch 54 is turned off, the seventh switch 72 and the eighth switch 74 are alternately turned on and off. With the first switch 22 off, the second switch 24 on, the third switch 42 on, the fourth switch 44 off, the fifth switch 52 on, and the sixth switch 54 off, the seventh switch 72 Is turned on, and the eighth switch 74 is turned off, the potential of the fifth connection point 76 becomes the voltage −Vd1 / 2. On the other hand, the seventh switch 22 is turned off, the second switch 24 is turned on, the third switch 42 is turned on, the fourth switch 44 is turned off, the fifth switch 52 is turned on, and the sixth switch 54 is turned off. When the switch 72 is turned off and the eighth switch 74 is turned on, the potential of the fifth connection point 76 is the voltage −Vd1 / subtracting the voltage −Vd3 indicating the potential of the other end of the fourth capacitor 60 from the voltage −Vd1 / 2. 2-Vd3. Therefore, in the period T8, a voltage having a pulse waveform that alternately repeats the voltage −Vd1 / 2 and the voltage −Vd1 / 2−Vd3 is output from the fifth connection point 76.

  In the period T8, the switch controller 90 turns off the first switch 22, turns on the second switch 24, turns on the third switch 42, turns off the fourth switch 44, turns on the fifth switch 52, and turns on the sixth switch 54. In the state in which the seventh switch 72 and the eighth switch 74 are alternately turned on and off, in the period T9, the first switch 22 is turned off, the second switch 24 is turned on, the third switch 42 is turned on, and the fourth switch is turned on. With the switch 44 turned off, the fifth switch 52 turned off, and the sixth switch 54 turned on, the seventh switch 72 and the eighth switch 74 are alternately turned on and off. With the first switch 22 off, the second switch 24 on, the third switch 42 on, the fourth switch 44 off, the fifth switch 52 off, and the sixth switch 54 on, the seventh switch 72 When the eighth switch 74 is turned off, the potential of the fifth connection point 76 becomes a voltage −Vd1 / 2 + Vd3 obtained by adding the voltage Vd3 to the voltage −Vd1 / 2. On the other hand, the seventh switch 22 is turned off, the second switch 24 is turned on, the third switch 42 is turned on, the fourth switch 44 is turned off, the fifth switch 52 is turned off, and the sixth switch 54 is turned on. When the switch 72 is turned off and the eighth switch 74 is turned on, the potential at the fifth connection point 76 becomes the voltage −Vd1 / 2. Therefore, in the period T <b> 9, a voltage having a pulse waveform that alternately repeats the voltage −Vd1 / 2 + Vd3 and the voltage −Vd1 / 2 is output from the fifth connection point 76.

  In the period T9, the switch control unit 90 turns off the first switch 22, turns on the second switch 24, turns on the third switch 42, turns off the fourth switch 44, turns off the fifth switch 52, and turns on the sixth switch 54. In the state in which the seventh switch 72 and the eighth switch 74 are alternately turned on and off, in the period T10, the first switch 22 is turned on, the second switch 24 is turned off, the third switch 42 is turned off, the fourth switch With the switch 44 turned on, the fifth switch 52 turned on, and the sixth switch 54 turned off, the seventh switch 72 and the eighth switch 74 are alternately turned on and off. With the first switch 22 on, the second switch 24 off, the third switch 42 off, the fourth switch 44 on, the fifth switch 52 on, and the sixth switch 54 off, the seventh switch 72 Is turned on, and the eighth switch 74 is turned off, the potential of the fifth connection point 76 becomes the ground voltage GND. On the other hand, with the first switch 22 on, the second switch 24 off, the third switch 42 off, the fourth switch 44 on, the fifth switch 52 on, and the sixth switch 54 off, When the switch 72 is turned off and the eighth switch 74 is turned on, the potential at the fifth connection point 76 is the voltage −Vd3. Therefore, in the period T <b> 10, a voltage having a pulse waveform that alternately repeats the voltage GND and the voltage −Vd <b> 3 is output from the fifth connection point 76.

  As described above, the switch control unit 90 turns on / off each switch under the on / off condition of each switch in each period, thereby causing a voltage V4 whose potential changes stepwise as indicated by reference numeral 204 in FIG. Is output from the fifth connection point 76. The smoothing circuit 80 smoothes the voltage V4 whose potential changes stepwise.

  The power conditioners described in Patent Document 1 and Patent Document 2 input a ripple current to the third capacitor 30 in a total of six periods of a period T2, a period T3, a period T4, a period T7, a period T8, and a period T9. On the other hand, the power conditioner 100 according to the present embodiment inputs a ripple current to the third capacitor 30 in a total of four periods of the period T1, the period T5, the period T6, and the period T10. That is, according to the present embodiment, the ripple current input to the third capacitor 30 can be reduced as compared with the power conditioners described in Patent Document 1 and Patent Document 2. Therefore, since the ripple current input to the third capacitor 30 can be reduced, the capacity of the third capacitor 30 can be reduced, and the electric energy loss can be reduced as a whole of the power conditioner 100. Moreover, according to this embodiment, since the 3rd capacitor | condenser 30 can be reduced in size, the power conditioner 100 can be reduced in size.

Here, the switch control unit 90 sets the switching timing of each period to the voltage Vd1 of the DC power source 110 measured by the first voltage sensor 32 and the voltage Vd2 of the third capacitor 30 measured by the third voltage sensor 36. , And the voltage Vd3 of the fourth capacitor 60 measured by the fourth voltage sensor 38. The switch control unit 90 sets a period σ1 from when the third switch 42 is turned on to off and the fourth switch 44 is turned on from off to when the third switch 42 is turned on from off to when the fourth switch 44 is turned off. This is determined based on the voltage Vd1 of the DC power supply 110. The period σ1 indicates a total period of the period T2, the period T3, and the period T4, and a total period of the period T7, the period T8, and the period T9. Similarly, the switch control unit 90 switches from turning on the first switch 22 and turning off the second switch 24 from turning on to turning on the first switch 22 from off to turning on the second switch 24 from on to off. The period σ2 is determined based on the voltage Vd1 of the DC power supply 110. Here, the period σ2 indicates the total period of the period T7, the period T8, and the period T9, and has the same length as the period σ1. And period (sigma) 1 and period (sigma) 2 are calculated by Formula (1).

  In Expression (1), Vs represents a reference AC voltage to be output by the power conditioner 100, that is, an effective value of the AC voltage of the system power supply 120.

  In the present embodiment, the first off period of the first switch 22 (the total period of the period T7, the period T8, and the period T9) is a point of the negative peak voltage of the reference AC voltage in one cycle of the reference AC voltage. The period corresponding to half of the period σ2 is assigned to the time in the front-rear direction. Further, the second ON period of the third switch (the total period of the period T2, the period T3, and the period T4) is centered on the point of the peak voltage on the positive side of the reference AC voltage in one cycle of the reference AC voltage. This corresponds to a period in which half the period σ1 is allocated in the front-rear direction. Further, the third ON period of the third switch (the total period of the period T7, the period T8, and the period T9) is centered around the point of the negative peak voltage of the reference AC voltage in one cycle of the reference AC voltage. This corresponds to a period in which half the period σ1 is allocated in the front-rear direction.

  The switch control unit 90 calculates the period σ1 and the period σ2 based on the voltage Vd1 of the DC power supply 110 and the AC voltage effective value of the system power supply 120. Then, the switch control unit 90 creates a voltage command value indicating the voltage waveform of the reference AC voltage to be output by the power conditioner 100 based on the AC voltage of the system power supply 120 measured via the second voltage sensor 34. . Further, the switch control unit 90 refers to the created voltage command value, and the midpoint of the period σ1 matches the time point corresponding to the positive peak voltage of the reference AC voltage in one cycle of the reference AC voltage, The period σ1 and the period σ2 are assigned so that the midpoint between the period σ1 and the period σ2 matches the time point corresponding to the negative peak voltage of the reference AC voltage. Thereby, the switch control part 90 can determine the timing of switching of each period. For example, the switch control unit 90 assigns the period σ1 and the period σ2 in one cycle of the reference AC voltage, so that the switching timing from the period T1 to the period T2 is based on the voltage Vd1 and the AC voltage effective value of the system power supply 120. Can be determined. In other words, the switch control unit 90, based on the voltage Vd1 of the DC power supply 110 and the AC voltage effective value of the system power supply 120, the period T2, the period T3, and the period in which the third switch 42 is on and the fourth switch is off. The period σ1 that is the total period of the period T4 and the period σ2 that is the total period of the period T7, the period T8, and the period T9 in which the first switch 22 is off and the second switch 24 is on are expressed by Equation (1). Can be determined. Note that the switch control unit 90 turns off the third switch 42, turns off the fourth switch 44, turns off the third switch 42, and turns off the fourth switch 44. The period σ1 and the period σ2 from when the second capacitor is turned on may be determined based on the voltage Vd2 of the third capacitor 30. The switch control unit 90 turns on the first switch 42 and the fourth switch 44 from on, turns off the second switch 24 and the third switch 42, and turns on the first switch 22 and the fourth switch 44 from off. The period σ2 from when the second switch 24 and the third switch 42 are turned off to off may be determined based on the voltage Vd3 of the fourth capacitor. The switch control unit 90 determines a target voltage to be applied to the third capacitor 30 and the fourth capacitor 60 based on the reference AC voltage. Therefore, the switch control unit 90 may feedback control the period σ1 and the period σ2 so that the voltage Vd2 of the third capacitor 30 and the voltage Vd3 of the fourth capacitor 60 become the respective target voltages.

  FIG. 4 is a diagram showing the relationship between the voltage Vd1 of the DC power supply 110 and the effective current value input to the third capacitor 30. As shown in FIG. A curve 210 shows the relationship between the voltage Vd1 and the effective current value in the power conditioner 100 according to the present embodiment. On the other hand, the curve 212 shows the relationship between the voltage Vd1 and the effective current value in the power conditioners described in Patent Document 1 and Patent Document 2 in which one end of the capacitor connected to the negative electrode of the DC power supply 110 is connected to the ground. Show. According to the present embodiment, when the voltage Vd1 (input voltage to the power conditioner 100) of the DC power supply 110 is, for example, 800V, the effective current value input to the third capacitor 30 is Patent Document 1 and Patent Document 2. The value of the current effective value in the case of the power conditioner described in (1) is 1/2. In the case of 640 V, the effective current value input to the third capacitor 30 is 1/3 of the effective current value in the case of the power conditioners described in Patent Document 1 and Patent Document 2. The equivalent series resistance (ESR) loss of a capacitor increases in proportion to the square of the current. Therefore, when the voltage Vd1 of the DC power supply 110 is, for example, 640V, the ESR loss generated in the third capacitor 30 is reduced to 1/9 compared with the power conditioners described in Patent Document 1 and Patent Document 2. Can be reduced.

  FIG. 5 shows an example of an inverter system 500 when the power conditioner 100 is applied to a three-phase four-wire power source. The inverter system 500 includes a first inverter device 101, a second inverter device 102, and a third inverter device 103 connected to the three-phase power sources 120R, 120S, and 120T by star connection. The first inverter 101 includes a capacitor group 10 including a first capacitor 12 and a second capacitor 14 connected in series, and an inverter circuit 300 connected to both ends of the capacitor group 10. The inverter circuit 300 includes a first switch group 20, a third capacitor 30, a second switch group 40, a third switch group 50, a fourth capacitor 60, a fourth switch group 70, and a smoothing circuit 80 shown in FIG. May be the same. That is, the first inverter 101 may be the same as the power conditioner 100. The second inverter device 102 and the third inverter device 103 have the same circuit as the inverter circuit 300. The second inverter device 102 and the third inverter device 103 are connected in parallel to the positive side of the first capacitor 12 and the negative side of the second capacitor 14, and the direct current charged in the first capacitor 12 and the second capacitor 14. A sine wave voltage is output by chopping the voltage. Inverter system 500 connects the outputs of first inverter device 101, second inverter device 102, and third inverter device 103 by star connection, and outputs a three-phase alternating current. According to such a configuration, even if the connection point 122 of the star connection and the first connection point 16 of the first inverter device are not connected, each switch is controlled by the on / off condition as shown in FIG. By chopping the DC voltage charged in the capacitor 12 and the second capacitor 14, the potential at the connection point 122 of the star connection and the potential at the first connection point 16 of the first inverter device become the same potential (ground potential). . Therefore, the first connection point 16 need not be connected to the ground.

  FIG. 6 shows an example of an inverter system 600 when the power conditioner 100 is also applied to a three-phase three-wire power source. Inverter system 600 includes first inverter device 101 and second inverter device 102 connected to three-phase power supplies 120R and 120S by V connection. The first inverter device 101 and the second inverter device 102 output a sine wave voltage by chopping the DC voltage charged in the first capacitor 12 and the second capacitor 14. The inverter system 600 connects the outputs of the first inverter device 101 and the second inverter device 102 by V connection, connects the connection point 124 of the V connection and the first connection point 16 of the first inverter device 101, In addition, a three-phase alternating current is output by setting the connection point 124 of the V connection to a reference potential.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

10 capacitor group 12 first capacitor 14 second capacitor 16 first connection point 20 first switch group 22 first switch 24 second switch 26 second connection point 30 third capacitor 32 first voltage sensor 34 second voltage sensor 36 second 3 voltage sensor 38 4th voltage sensor 40 2nd switch group 42 3rd switch 44 4th switch 46 3rd connection point 50 3rd switch group 52 5th switch 54 6th switch 56 4th connection point 60 4th capacitor 70 4th 4 switch group 72 7th switch 74 8th switch 76 5th connection point 80 Smoothing circuit 90 Switch control part 100 Power conditioner 110 DC power supply 120 System power supply

Claims (18)

A capacitor having a first capacitor and a second capacitor connected in series, connected in parallel with a DC power supply, and having a neutral potential at the first connection point between the first capacitor and the second capacitor Group,
A first switch group having a first switch and a second switch connected in series, and connected in parallel with the capacitor group;
A third capacitor having one end connected to a second connection point between the first switch and the second switch;
Sine wave voltage generating means connected to the third capacitor and outputting a sine wave voltage by chopping the DC voltage charged in the first capacitor and the second capacitor together with the first switch group. Inverter device. The sine wave voltage generating means is
A second switch group having a third switch and a fourth switch connected in series, and connected in parallel with the third capacitor;
A fifth switch and a sixth switch are connected in series, and a fourth connection point of the fifth switch and the sixth switch is connected to a third connection point of the third switch and the fourth switch. A third switch group;
A fourth capacitor connected in parallel with the third switch group;
A fourth switch group having a seventh switch and an eighth switch connected in series, and connected in parallel with the fourth capacitor;
The DC power supply is controlled by turning on and off the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch. A switch control unit that converts the DC voltage from the AC voltage into an AC voltage and outputs the AC voltage from a fifth connection point of the seventh switch and the eighth switch;
The inverter device according to claim 1, further comprising a smoothing circuit that smoothes a pulse waveform of the AC voltage. The switch control unit
The seventh switch with the first switch on, the second switch off, the third switch off, the fourth switch on, the fifth switch off, and the sixth switch on And the eighth switch are alternately turned on and off, the first switch is turned on, the second switch is turned off, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned on, and The inverter device according to claim 2, wherein the seventh switch and the eighth switch are alternately turned on and off while the sixth switch is turned off. The switch control unit
The seventh switch with the first switch on, the second switch off, the third switch on, the fourth switch off, the fifth switch on, and the sixth switch off And the eighth switch are alternately turned on and off, then the first switch is turned on, the second switch is turned off, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned off, and The inverter device according to claim 3, wherein the seventh switch and the eighth switch are alternately turned on and off while the sixth switch is turned on. The switch control unit
The seventh switch with the first switch on, the second switch off, the third switch on, the fourth switch off, the fifth switch off, and the sixth switch on And the eighth switch are alternately turned on and off, the first switch is turned on, the second switch is turned off, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned on, and 5. The inverter device according to claim 4, wherein the seventh switch and the eighth switch are alternately turned on and off while the sixth switch is turned off. The switch control unit
The seventh switch with the first switch on, the second switch off, the third switch on, the fourth switch off, the fifth switch on, and the sixth switch off And the eighth switch are alternately turned on and off, the first switch is turned on, the second switch is turned off, the third switch is turned off, the fourth switch is turned on, the fifth switch is turned off, and The inverter device according to claim 5, wherein the seventh switch and the eighth switch are alternately turned on and off while the sixth switch is turned on. The switch control unit
The seventh switch with the first switch on, the second switch off, the third switch off, the fourth switch on, the fifth switch off, and the sixth switch on And the eighth switch are alternately turned on and off, the first switch is turned on, the second switch is turned off, the third switch is turned off, the fourth switch is turned on, the fifth switch is turned on, The inverter device according to claim 6, wherein the seventh switch and the eighth switch are alternately turned on and off while the six switches are turned off. The switch control unit
With the first switch on, the second switch off, the third switch off, the fourth switch on, the fifth switch on, and the sixth switch off, the seventh switch and After the eighth switch is alternately turned on and off, the first switch is turned off, the second switch is turned on, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned off, and the second switch is turned on The inverter device according to claim 7, wherein the seventh switch and the eighth switch are alternately turned on and off while six switches are turned on. The switch control unit
The seventh switch with the first switch off, the second switch on, the third switch on, the fourth switch off, the fifth switch off, and the sixth switch on And the eighth switch are alternately turned on and off, then the first switch is turned off, the second switch is turned on, the third switch is turned on, the fourth switch is turned off, the fifth switch is turned on, and The inverter device according to claim 8, wherein the seventh switch and the eighth switch are alternately turned on and off while the sixth switch is turned off. The switch control unit
The seventh switch with the first switch off, the second switch on, the third switch on, the fourth switch off, the fifth switch on, and the sixth switch off And the eighth switch alternately on and off, then the first switch off, the second switch on, the third switch on, the fourth switch off, the fifth switch off, and the The inverter device according to claim 9, wherein the seventh switch and the eighth switch are alternately turned on and off while the sixth switch is turned on. The switch control unit
The seventh switch with the first switch off, the second switch on, the third switch on, the fourth switch off, the fifth switch off, and the sixth switch on And the eighth switch are alternately turned on and off, then the first switch is turned on, the second switch is turned off, the third switch is turned off, the fourth switch is turned on, the fifth switch is turned on, and The inverter device according to claim 10, wherein the seventh switch and the eighth switch are alternately turned on and off while the sixth switch is turned off. A first voltage measuring unit for measuring a voltage of the DC power supply;
A second voltage measuring unit that measures the AC voltage of the system power supply,
The switch control unit
The inverter according to any one of claims 2 to 11, wherein a period during which the second switch and the third switch are turned on is determined based on the voltage of the DC power supply and the AC voltage of the system power supply. apparatus. A third voltage measuring unit for measuring the voltage of the third capacitor;
The switch control unit
A period from when the third switch is turned on to off, from when the fourth switch is turned on to off, until the third switch is turned on from off, and the fourth switch is turned off to on. The inverter device according to claim 12, which is determined based on A fourth voltage measuring unit for measuring the voltage of the fourth capacitor;
The switch control unit
The first switch and the fourth switch are turned on from off, the second switch and the third switch are turned on from off, and then the first switch and the fourth switch are turned off from on, the second switch and The inverter device according to claim 13, wherein a period until the third switch is turned off is determined based on the voltage of the fourth capacitor.   The inverter device according to any one of claims 1 to 14, wherein the first connection point is a reference potential. A first inverter device which is the inverter device according to any one of claims 1 to 14,
The first capacitor is connected in parallel to the positive side of the first capacitor and the negative side of the second capacitor, and outputs a sine wave voltage by chopping the DC voltage charged in the first capacitor and the second capacitor. 2 inverter devices and a third inverter device,
An inverter system that outputs three-phase alternating current by connecting the outputs of the first inverter device, the second inverter device, and the third inverter device by a star connection. A first inverter device which is the inverter device according to any one of claims 1 to 14,
The first capacitor is connected in parallel to the positive side of the first capacitor and the negative side of the second capacitor, and outputs a sine wave voltage by chopping the DC voltage charged in the first capacitor and the second capacitor. 2 inverter devices,
The respective outputs of the first inverter device and the second inverter device are connected by a V connection, the connection point of the V connection and the first connection point of the first inverter device are connected, and the V connection An inverter system that outputs three-phase alternating current by using the connection point as a reference potential. Solar cells,
A solar power generation system provided with the inverter apparatus as described in any one of Claims 1-17 which converts the direct current voltage from the said solar cell into alternating current voltage.

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