Electric power conversion systems – Current conversion – Having plural converters for single conversion
Reexamination Certificate
1999-05-19
2001-01-16
Han, Jessica (Department: 2838)
Electric power conversion systems
Current conversion
Having plural converters for single conversion
C323S906000
Reexamination Certificate
active
06175512
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention is related to a power system which converts DC output from a DC power source such as a solar cell and a fuel cell to AC output by an inverter and supplies to a load, and is intended for an efficient operation of the inverter.
2. Description of Prior Art
A solar power generating system which uses solar cells becomes popular as a clean power system.
FIG. 5
is a schematic view illustrating a conventional solar power generating system for domestic use. DC sources
101
comprising of a plurality of solar cells are placed on a house roof. DC output from the plurality of DC sources is accumulated and flowed into a connection box
102
. The DC output from the connection box
102
is converted to AC output by an inverter
103
, and is supplied to a load
105
as home electric appliance through a panelboard
104
. Electricity can be also supplied to the loads
105
from a commercial power supply
106
. When electricity runs short, for example at night, electric power is supplied from the commercial power supply
106
.
In the meanwhile, efficiency of an inverter dips sharply at a time of low output. To solve the problem, Patent Abstracts of Japan, publication number 06165513, for example, provides a method for operating a plurality of inverters in parallel and determining how many inverters should be operated by judging a total output current of inverters.
SUMMARY OF THE INVENTION
The conventional procedure determines merely how many inverters should be operated on a basis of output current and does not take into consideration about which inverters should be operated. Accordingly, particular inverters work at a time of low output and the others work only at a time when output is increased. The particular inverters are operated longer than the other, resulting in shorter service life of that particular inverters than the others.
In addition, in a case where the above-mentioned particular inverters among the plurality of inverters become out of work, the total system can not work.
The present invention was made to overcome this drawback.
A device for operating inverters in the present invention comprises a plurality of inverters connected in parallel to a DC source, means for determining the number of inverters to be operated on a basis of AC output from the plurality of inverters or DC output from the DC source, and selection means for selecting the determined number of inverters to be operated among the plurality of inverters at random.
The selection means includes a random number generation unit for calculating data on an inverter to be selected on a basis of information from the random number generation unit.
The inverters are connected to the DC source through switches. The selection means controls the switches to turn ON or OFF.
As above described, inverters to be operated can be selected at random from the plurality of inverters by selecting an inverter to be added or cut off among the plurality of inverters on a basis of the random number, preventing a particular inverter from working for a long period of time.
A device for operating inverters in the present invention comprises a plurality of inverters connected in parallel to a DC source, means for determining the number of inverters to be operated on a basis of AC output from the plurality of inverters or DC output from the DC source, and selection means for selecting the determined number of inverters to be operated with less operating time among the plurality of inverters.
The selection means includes storage means for storing data on the inverters' operating time and selects inverters to be operated by referring data in the storage means.
The inverters are connected to the DC source through switches. The selection means controls the switches to turn ON or OFF.
Inverters to be operated with less operating time are selected from the plurality of inverters. By selecting in such a manner, the determined number of inverters with less operating time are selected on a basis of operating time of each inverter among the plurality of inverters. Therefore, the operating time of each inverter becomes approximately equal, resulting in the prolonged service life of the power system.
A device for operating inverters in the present invention comprises a plurality of inverters connected in parallel to a DC source, means for determining the number of inverters to be operated on a basis of AC output from the plurality of inverters or DC output from the DC source, and selection means for selecting the determined number of inverters to be operated with less output amount among the plurality of inverters.
The selection means includes storage means for storing data on the inverters' output amount and selects inverters to be operated by referring data in the storage means.
The inverters are connected to the DC source through switches. The selection means controls the switches to turn ON or OFF.
Inverters to be operated with less output amount are selected from the plurality of inverters. By selecting in such a manner, the determined number of inverters with less output amount are selected among the plurality of inverters. Therefore, the frequency of operating each inverter becomes approximately equal, resulting in the prolonged service life of the power system.
A power system in the present invention having a DC source, a plurality of inverters connected in parallel to a DC source comprises means for determining the number of inverters to be operated on a basis of AC output from the plurality of inverters or DC output from the DC source, and selection means for selecting the determined number of inverters to be operated among the plurality of inverters at random, and DC output from the DC source is converted to AC output to yield the AC output.
As above described, the determined number of inverters to be operated can be selected at random from the plurality of inverters. It can prevent a particular inverter from working for a long period of time and achieve a prolonged service life of the power system.
A power system in the present invention having a DC source and a plurality of inverters connected in parallel to the DC source comprises means for determining the number of inverters to be operated on a basis of AC output from the plurality of inverters or DC output from the DC source, and selection means for selecting the determined number of inverters to be operated with less operating time among the plurality of inverters, and DC output from the DC source is converted to AC output to yield the AC output.
As above described, the determined number of inverters to be operated with less operating time can be selected among the plurality of inverters. Therefore, operating time of each inverter becomes approximately equal, resulting in a prolonged service life of the power system.
A power system in the present invention having a DC source and a plurality of inverters connected in parallel to a DC source comprises means for determining the number of inverters to be operated on a basis of AC output from the plurality of inverters or DC output from the DC source, and selection means for selecting the determined number of inverters to be operated with less output amount among the plurality of inverters, and DC output from the DC source is converted to AC output to yield the AC output.
As above described, the determined number of inverters to be operated with less output amount can be selected from the plurality of inverters. Frequency of operating each inverter becomes approximately equal, resulting a prolonged service life of the power system.
In addition, a power system according to the present invention is provided with failure judging means for judging a failure in each of the plurality of inverters. The determined number of inverters are selected from the plurality of inverters on a basis of a signal from the failure judging means. The power system according to the present invention is also provided with an alarm for giving the output result from the failure judging means.
I
Hagihara Ryuzo
Ishida Takeo
Uchihashi Kenji
Arent Fox Kintner & Plotkin & Kahn, PLLC
Han Jessica
Sanyo Electric Co,. Ltd.
LandOfFree
Device for operating inverter and power system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for operating inverter and power system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for operating inverter and power system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2445782