Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Reexamination Certificate
2003-04-17
2004-05-04
Vu, Bao Q. (Department: 2838)
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
C363S034000, C363S072000
Reexamination Certificate
active
06731522
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a power generation apparatus using a permanent-magnet generator and more particularly to control of a power converter.
The power generation apparatus using the permanent-magnet generator uses a gas turbine, a hydropower, wave power or the like as a power source to rotate the permanent-magnetic generator. AC power generated by the permanent-magnet generator is converted into DC power by a first converter and the DC power produced by the first converter is converted into AC power by a second converter again to supply the AC power.
As a control method of the power generation apparatus using the permanent-magnet generator, JP-A-2000-345952 discloses “a wind power multipole generator and a wind power generation method” in which an active power command value is decided on the basis of the rotation speed of a multipole generator to control output power of a variable speed inverter. Further, JP-A-5-22938 discloses “a control circuit of a power conversion system” in which a power converter is controlled to make a terminal voltage of a permanent-magnet generator fixed.
In order to utilize energy obtained from the power source effectively, it is desirable to make the power generation apparatus using the permanent-magnet generator have robust characteristics with high efficiency.
In the prior art, since the active power command value is decided on the basis of the rotation speed of the power generator to control active power, measures for adjusting a power factor of the power generator are not provided and operation taking the efficiency into consideration as a power generation system is not always performed. Further, when the constant terminal voltage is maintained, a large reactive current is supplied in order to increase the terminal voltage in the area where the rotation speed of the power generator is low, so that a potential difference between the terminal voltage and an internal induced voltage of the power generator is increased to make a phase difference between the terminal voltage and the current large and consequently reduce the power generation efficiency.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a power generation apparatus using a permanent-magnet generator or a power generation system using the same having robust characteristics with high efficiency within a wide variable speed range in a capacity of a converter by means of control of reactive power or a voltage of a first converter.
The power generation apparatus using the permanent-magnet generator according to the present invention, includes a permanent-magnet generator for generating AC power, a first converter for converting the AC power generated by the generator into DC power, and a second converter for converting the DC power produced by the first converter into AC power. The first converter includes means for controlling active power of the AC power of the generator and means for controlling reactive power of the AC power of the generator, and the second converter includes means for producing the active power.
In the power generation apparatus using the permanent-magnet generator according to the present invention, the first converter includes means for calculating a reactive power command value on the basis of an active power command value and a rotation speed of the generator and the first converter controls reactive power of the AC power of the generator on the basis of the active power command value and the rotation speed of the generator.
In the power generation apparatus using the permanent-magnet generator according to the present invention, the first converter includes means for controlling active power of the AC power of the generator, means for controlling a voltage of the AC power of the generator, and means for calculating a voltage command value on the basis of an active power command value and a rotation speed of the generator and the first converter controls a terminal voltage of the generator on the basis of the active power command value and the rotation speed of the generator.
A setting method of the power generation apparatus using the permanent-magnet generator according to the present invention, including means for calculating a reactive power command value on the basis of an active power command value and a rotation speed of the generator and means for calculating a voltage command value on the basis of the active power command value and the rotation speed of the generator, comprises setting up the reactive power command value or the voltage command value so that a phase difference between an output current of the generator and an internal induced voltage of the generator is equal to zero in accordance with the active power command value until a rotation speed at which a terminal voltage of the generator reaches a rated value is reached and setting up the reactive power command value or the voltage command value so that the terminal voltage is fixed in accordance with the active power command value in the area where the rotation speed is increased.
In the setting method of the power generation apparatus using the permanent-magnet generator according to the present invention, the first converter includes means for controlling active power of the AC power of the generator, means for controlling a voltage of the AC power of the generator, and means for calculating a voltage command value on the basis of an active power command value or the rotation speed of the generator, and the first converter controls a terminal voltage of the generator on the basis of the active power command value or the rotation speed of the generator.
The setting method of the power generation apparatus using the permanent-magnet generator according to the present invention, including means for calculating the voltage command value on the basis of the active power command value or the rotation speed of the generator, comprises setting up the voltage command value so that the terminal voltage is fixed in accordance with the active power command value or the rotation speed of the generator.
With the above configuration, there can be provided the power generation apparatus using the permanent-magnet generator having the robust characteristics with high efficiency while utilizing the converter capacity effectively.
Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings.
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Futami Motoo
Kawazoe Hironari
Kikuchi Akira
Crowell & Moring LLP
Hitachi , Ltd.
Vu Bao Q.
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