Electric power conversion systems – Current conversion – With condition responsive means to control the output...
Reexamination Certificate
2001-09-25
2002-12-10
Sterrett, Jeffrey (Department: 2838)
Electric power conversion systems
Current conversion
With condition responsive means to control the output...
C323S906000
Reexamination Certificate
active
06493246
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a power converting apparatus, control method thereof, and generator and, more particularly, to a power converting apparatus such as an inverter used for a solar power generation apparatus and a control method thereof.
BACKGROUND OF THE INVENTION
Power generated by a solar battery for generating power in accordance with sunlight is small in the morning/evening or in a cloudy/rainy day. If the generated power is small, an inverter in the solar power generation apparatus connected to a commercial electric power system (to be simply referred to as a “system” hereinafter) may be repeatedly activated and stopped. For this reason, an operation method for suppressing unnecessary stop of the inverter is required. Such operation methods are disclosed in, e.g., Japanese Patent No. 2509187 in which when the direct current input voltage of an inverter is equal to more than a threshold value, the inverter is activated after the elapse of a predetermined time, and Japanese Patent Laid-Open No. 2000-23367 in which when the direct current input voltage of an inverter is less than a threshold value, the inverter is stopped after the elapse of a predetermined time.
As shown in
FIG. 1
, when a direct current input voltage V of an inverter abruptly drops, input power P
1
also abruptly drops together. When power (to be sometimes referred to as “non-load power” hereinafter) necessary for, e.g., the control circuit of the inverter is supplied from the load side of the inverter, such as a system, a period from when the input voltage V becomes lower than a threshold voltage V
1
at which the inverter should be stopped, and the inverter is stopped after the elapse of a predetermined time may include a period when power consumed by the inverter become larger than power output from the inverter, i.e., power is wasted.
As shown in
FIG. 2
, if the input voltage V fluctuates near the threshold voltage V
1
, the operation of the inverter may not be stopped, and power may be wasted.
If the predetermined time is shortened to suppress wasteful power consumption, activation and stop of the inverter may be repeated at high probability.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-described problems individually or altogether, and has as its object to suppress wasteful power consumption of a power converting apparatus.
It is another object of the present invention to suppress unnecessary stop of a power converting apparatus.
In order to achieve the above objects, according to a preferred aspect of the present invention, a power converting apparatus comprising a power converter, arranged to convert direct current power to alternating current power, a measurement unit, arranged to measure input or output power of said power converter and calculate integrated power for every predetermined period on the basis of the measured power; and a controller, arranged to stop conversion operation of said power converter when the integrated power is less than a predetermined value is disclosed.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.
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Suzui Masaki
Takehara Nobuyoshi
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