Prime-mover dynamo plants – Electric control – Engine control
Reexamination Certificate
2000-05-10
2002-02-19
Waks, Joseph (Department: 2834)
Prime-mover dynamo plants
Electric control
Engine control
C290S04000F
Reexamination Certificate
active
06348743
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a voltage control apparatus of an engine generator which controls an output voltage of an automatic voltage regulator (AVR) of an engine generator, and a control method thereof.
BACKGROUND OF THE INVENTION
An engine generator is widely used as a movable power source in a field of construction work or the like, an emergency power source in a building, a plant, a hospital or the like, or a permanent power source in an area where a commercial power source can not be obtained. In the engine generator, when a load suddenly increases due to a load input, an output of an engine driving the power generator can not follow an increase of the load, so that an engine rotational speed is largely reduced in a moment. Since this reduction of the engine rotational speed gives a bad influence to the load maintained in the power generator, it is defined so as to set a reduction rate with respect to a rated rotational speed and a time required after the rotational speed is reduced and before being returned to the rated rotational speed to be within a predetermined range.
When the load of the engine generator is suddenly increased, the engine rotational speed is reduced and a governor is operated in accordance therewith so as to increase a fuel injection amount. However, since the power generator is generally driven by an engine with a supercharger, an increase of a pressure of a supplied air is delayed in comparison with an increase of a fuel injection amount. Accordingly, a recovery of the engine rotational speed is delayed. Then, a lot of techniques for quickening a recovery of the engine rotational speed have been conventionally suggested. For example, in accordance with a technique disclosed in Unexamined Japanese Patent Publication No. 5-111298, an output voltage control for reducing an energizing current of an automatic voltage regulator only for a fixed time at a fixed rate so as to descend an output voltage thereof is performed as means for temporarily reducing a load applied to the power generator.
However, since the control in accordance with the technique mentioned above is performed by a load information in the power generator side such as the output current or the output power of the power generator and the like, an output current sensor, an output power detector and the like are required. Since the load of the power generator generally corresponds to a great energy, and the output voltage value and the output current value correspond to great values, the output current sensor, the output power detector and the like for detecting them are set to be a large scale having a great energy resisting amount. Accordingly, the control apparatus tends to be formed in a large scale, a structure thereof is complex and a cost therefor is increased. Further, a large space for placing the sensors and the control apparatus is required and it is hard to make the engine generator compact.
SUMMARY OF THE INVENTION
The present invention is made by taking the problems mentioned above in the prior art into consideration, and an object of the present invention is to provide a voltage control apparatus of an engine generator having a simple structure and capable of being made compact, and a control method thereof.
In order to achieve the object mentioned above, in accordance with a first aspect of the present invention, there is provided a method of controlling a voltage of an engine generator comprising the steps of:
detecting an actually measured value of an engine rotational speed at every predetermined time; and
controlling an output voltage of the power generator in accordance with a deviation value between a predetermined target value and the actually measured value when the actually measured value is equal to or less than the target value.
In accordance with the first aspect, since a degree of the load applied to the power generator is judged on the basis of the engine rotational speed and the output voltage of the power generator is controlled in accordance with the deviation value between the predetermined target value and the actually measured value of the rotational speed, that is, in accordance with a degree of change of the rotational speed, it is possible to reduce the output voltage in accordance with a magnitude of the sudden load change. Accordingly, since the control is not performed by detecting the output current, the output power or the like in the power generator side which is employed in the conventional art, it is possible to restrict a change width and a change time of the output voltage, the frequency and the like of the power generator to a minimum limit at a sudden load transient time so as to move to a stable operation by utilizing the rotational speed detector particularly in the case that an electronic governor is provided. In general, since the rotational speed detector has a small energy resisting amount and is compact, it is possible to manufacture the control apparatus in accordance with the voltage control method at a low cost and in such a manner as to be compact.
In accordance with a second aspect of the present invention, there is provided a method of controlling a voltage of an engine generator comprising the steps of:
detecting an actually measured value of a fuel injection amount of an engine and an actually measured value of a rotational speed at every predetermined time; and
controlling an output voltage of the power generator in accordance with a deviation value between a predetermined target value of the fuel injection amount with respect to the actually measured value of the rotational speed and the actually measured value of the fuel injection amount.
In accordance with the second aspect, since a degree of the load applied to the power generator is judged on the basis of the fuel injection amount of the engine and the output voltage of the power generator is controlled in accordance with the deviation value between the target value of the fuel injection amount with respect to the actually measured value of the rotational speed of the engine and the actually measured value of the fuel injection amount, that is, in accordance with a degree of change of the fuel injection amount, it is possible to reduce the output voltage in accordance with a magnitude of the sudden load change. At this time, since it is possible to control the output voltage of the power generator even when the actually rotational speed is higher than the target value of the rotational speed in the first aspect, that is, an engine rotational speed for starting control, it is possible to detect a load increase in the power generator at an early time so as to reduce the load. Accordingly, since the control is not performed by detecting the output current, the output power or the like in the power generator side which is employed in the conventional art, it is possible to restrict a change width and a change time of the output voltage, the frequency and the like of the power generator to a minimum limit at a sudden load transient time so as to move to a stable operation by utilizing the rotational speed detector and the fuel injection amount detecting means particularly in the case that an electronic governor is provided. In general, since the rotational speed detector and the fuel injection amount detecting means has a small energy resisting amount and is compact, it is possible to manufacture the control apparatus in accordance with the voltage control method at a low cost and in such a manner as to be compact.
In accordance with a third aspect of the present invention, there is provided a method of controlling a voltage of an engine generator comprising the steps of:
detecting an actually measured value of a rotational speed of an engine and an actually measured value of a fuel injection amount at every predetermined time;
controlling an output voltage of the power generator in accordance with a deviation value between a predetermined target value of the fuel injection amount with respect to the actually measured value of the rotational
Abe Norifumi
Sakasai Takashi
Komatsu Ltd.
Sidley Austin Brown & Wood
Waks Joseph
LandOfFree
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