Power Conversion Apparatus

• US 20080101101A1
• Filed: 02/21/2006
• Published: 05/01/2008
• Est. Priority Date: 02/25/2005
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Ito, Hiroshi, Yamada, Masaki, Iwata, Akihiko, Kawakami, Tomoyuki, Harada, Shigeki, Seto, Makoto
• Granted Patent: US 7,596,008 B2
• Time in Patent Office: Days
• US Class Current: 363/71
• CPC Class Codes: H02M 1/0077 Plural converter units whose outputs are connected in series
• CPC Class Codes: H02M 7/5387 in a bridge configuration

Abstract

A power conversion apparatus includes a first single-phase inverter that uses ask a DC power source a first DC voltage that is boosted from a solar light voltage by a boosting chopper circuit. The first single-phase inverter is arranged between two single-phase inverters that use second DC power sources that are supplied from the first DC power source. AC sides of the respective single-phase inverters are connected in series. A power conditioner thus configured provides an output voltage using the sum of the generated voltages of the respective single-phase inverters. Chopper circuits are connected between the first DC power source and the second DC power sources, and power is supplied to the second DC power sources from the first DC power source via switching devices in the single-phase inverters.

Claims

1. A power conversion apparatus comprising:

a plurality of single-phase inverters, each of the single-phase inverters including switching devices and having AC sides and DC sides, and converting DC power from a plurality of DC power sources to AC powers, the plurality of single-phase inverters being connected in series, wherein the apparatus produces an output voltage that is a sum of generated voltages from a combination of single-phase inverters selected from the plurality of single-phase inverters;

a DC-DC converter; and

first and second DC power sources that supply DC output voltages to first and second single-phase inverters of the plurality of single-phase inverters, wherein

the first and second single-phase inverters have their AC sides connected to each other via the DC-DC converter, and

the DC-DC converter supplies power from a first DC power source, having a relatively higher output voltage to a second DC power source having a relatively lower voltage, via the switching devices in the first and second single-phase inverters.

2. The power conversion apparatus according to claim 1, wherein the DC-DC converter includes a chopper circuit including a reactor, a rectifying device, and a switch.

3. The power conversion apparatus according to claim 2, wherein, during an operation period when the first single-phase inverter that receives a first DC voltage from a first DC power source as an input, turns on the switching devices that connect a positive electrode of the first DC power source to an AC output power line, the switch in the chopper circuit is turned on and off.

4. The power conversion apparatus according to claim 2, wherein

a maximum DC power source of the DC power sources produces the highest DC output voltage of the DC power sources and the highest DC output voltage is generated from a third DC power source, and the maximum DC power source is the first DC power source,

the first single-phase inverter includes two AC terminals respectively connected to respective second single-phase inverters, and

each of the respective second DC power sources includes a chopper circuit and is supplied with power from the first DC power source via the switching devices of the first and second single-phase inverters.

5. The power conversion apparatus according to claim 4, wherein output pulse width of the first single-phase inverter is adjusted, and total power fluctuation calculated by subtracting charging from discharging via the single-phase inverters of DC power sources other than the maximum DC power source is positive or zero.

6. The power conversion apparatus according to claim 5, wherein output pulse width of the first single-phase inverter is adjusted so that the total power fluctuation is reduced.

7. The power conversion apparatus according to claim 4, including a magnetic coupling core of a magnetic material magnetically coupling two reactors in the chopper circuits.

8. The power conversion apparatus according to claim 7, wherein the two reactors are include windings configured so that polarities of electromotive forces induced by the reactors are in the same direction.

9. The power conversion apparatus according to claim 7, wherein the two reactors include windings configured so that polarities of electromotive forces induced by the reactors are in opposite directions, and including a gap for adjusting the magnetic coupling and located in the magnetic coupling core.

10. The power conversion apparatus according to claim 2, wherein

the single-phase inverters are connected in ascending or descending order of DC output voltages of the DC power sources that supply the DC output voltages,

a maximum DC power source of DC power sources providing the highest output voltage of the plurality of DC power sources is generated from a third power source,

first and second DC power sources that supply DC output voltages to each pair of the first and second single-phase inverters having their AC sides connected to each other via respective chopper circuits, and

each of the chopper circuits supplies power from the first DC power source having a relatively higher voltage to the second DC power source having a lower voltage, of each pair of the first and second single-phase inverters, via the switching devices in the first and second single-phase inverters, so that each of the DC power sources, other than the maximum DC power source, is supplied with power.

11. The power conversion apparatus according to claim 10, wherein output pulse width of the first single-phase inverter is adjusted, and total power fluctuation calculated by subtracting charging from discharging via the single-phase inverters of DC power sources, other than the maximum DC powers source, is positive or zero.

12. The power conversion apparatus according to claim 1, wherein output pulse width of the first single-phase inverter is adjusted so that the total power fluctuation is reduced.

13. The power conversion apparatus according to claim 1, including a boosting circuit having a switch wherein

a maximum DC power source of the DC power sources produces the highest DC output voltage of the DC power sources,

the highest DC output voltage is generated from a third DC power source via the boosting circuit, and

when the voltage of the third DC power source exceeds a predetermined voltage, on-off operation of the switch in the boosting circuit is stopped to stop boosting.

14. The power conversion apparatus according to claim 13, including a bypass circuit that bypasses the boosting circuit and, when the voltage of the third DC power source exceeds a predetermined voltage, on-off operation of the switch in the boosting circuit is stopped to stop boosting and the boosting circuit is bypassed by the bypass circuit.

15. The power conversion apparatus according to claim 14, wherein the bypass circuit includes a relay.

16. The power conversion apparatus according to claim 1, wherein a predetermined AC voltage and AC current are output and supplied to a load.

17. The power conversion apparatus according to claim 1, wherein a predetermined AC output is connected in parallel with a system and linked to the system.