Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Reexamination Certificate
2001-11-19
2003-11-25
Sterrett, Jeffrey (Department: 2838)
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
C363S132000, C363S137000, C363S141000
Reexamination Certificate
active
06654260
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power converter system which is constituted by semiconductor power converter apparatuses each employing self-arc-suppressing semiconductor devices.
2. Description of the Related Art
As for the recent typical self-arc-suppressing semiconductor devices, there are Insulated Gate Bipolar Transistors (the so-called IGBTs) and Injection Enhanced Gate Transistors (the so-called IEGTs), both of which are classified as gate voltage driving semiconductor devices, and Gate Commutated Turn-off Thyristors (the so-called GCTs) which are classified as a gate current driving semiconductor device. In the case where such self-arc-suppressing semiconductor devices are accommodated together with diodes which are connected in anti-parallel therewith, in the same package, with a reverse conduction function, they are sometimes called reverse conduction power devices.
For example, with respect to the IEGTs, as described in EPE '99-Lausanne “HIGH POWER (4.5 kV, 4 kA turn off) IEGT”, a plurality of IEGT chips and a plurality of diode chips can be accommodated in the same package to be used as one reverse conduction type power device. With respect to the IEGT having the collector current of 1.5 kA described in that article, the total number of chips which are accommodated in one package is 42, and these chips are broken down into the 30 IEGT chips and 12 diode chips.
In addition, in an article of TOSHIBA REVIEW Vol. 55, No. 7,2000 “High-Power Device IEGTs For Power Electronics”, there is described an IEGT which has a collector current of 750 A and which is different in outside dimension of the package from the above-mentioned IEGT.
The total number of chips which are accommodated in one package is 21, and these chips are broken down into the 15 IEGT chips and the 6 diode chips. With respect to these chips, the total number of chips which are accommodated in the package is changed to make the collector currents different from one another. With respect to the semiconductor power converter apparatus employing the IEGT, a three-level inverter having a rated capacity of 8 MVA is described in an article of TOSHIBA REVIEW Vol. 55, No. 7,2000 “High-Voltage Inverters Employing IEGTs for Industrial Motor Drives”.
On the other hand, with respect to the GCT, as described in an article of ABB REVIEW 5/1998 “GIST-a new, emerging technology for high-power, low-cost inverters”, the reverse conduction type power device in which the GCT region and the diode region are formed on the same silicon wafer and accommodated in one package has been realized as a product. In this article, the three GCTs are different in outside package dimension from one another. In this case, the area of the silicon wafer which is accommodated in the package is changed to change the controllable ON-current.
In addition, a power converter system, as shown in
FIG. 15
, a semiconductor power converter apparatus in which electric power is to be rectified, i.e., in a rectifier mode is larger than when the electric power is to be inverted, i.e., in an inverter mode, and a semiconductor power converter apparatus in which electric power is to be rectified is smaller than when the electric power is to be inverted, are connected in parallel with each other through a D.C. capacitor, is disclosed in JAPANESE PATENT APPLICATION LAID OPEN No. 288780 of 1986.
In this connection, the term forward-conversion means power conversion from A.C. to D.C., while the term reverse-conversion means power conversion from D.C. to A.C.
In
FIG. 15
, reference numeral
24
indicates a single-phase converter, reference numeral
25
indicates a three-phase inverter, reference numeral
26
indicates a D.C. capacitor, reference numeral
27
indicates a single-phase A.C. power source, and reference numeral
28
indicates an induction motor.
The two single-phase converters
24
, which are connected in parallel with each other, are applied to a semiconductor power converter apparatus in which electric power to be rectified is larger than the electric power to be inverted, while the three-phase inverter
25
is applied to a semiconductor power converter apparatus in which the electric power to be rectified is smaller than the electric power is to be inverted. In addition, the two single-phase converters
24
and the three-phase inverter
25
are connected in parallel with each other through the D.C. capacitor
26
, and the single-phase A.C. power source
27
is connected to an output terminal of the single-phase converter
24
.
Also, an induction motor
28
for driving an electric railway system, for example, is connected to an output terminal of the three-phase inverter
25
. When subjecting the induction motor
28
to the running power, the two single-phase converters
24
are operated in the forward conversion manner, while the three-phase inverter
25
is operated in the reverse conversion manner. In this case, the two single-phase inverters
24
need to input the driving electric power of the induction motor
28
and the electric power losses of all of the semiconductor power converter apparatuses
24
and
25
through the single-phase A.C. power source
27
.
In addition, when subjecting the induction motor
28
to regenerative operation, the three-phase inverter
25
is operated in the forward conversion manner, while the two single-phase converters
24
are operated in the reverse conversion manner. The forward conversion electric power of the three-phase inverters
25
in the regenerative operation is necessarily reduced as compared with the forward conversion electric power of the single-phase converter
24
in the power operation. This results because there is electric power loss in the semiconductor power converter apparatuses
24
and
25
, and electric power loss in the induction motor
28
, and also the operating electric power is smaller than the regenerative operating power in the induction motor
28
.
In the case where the conventional reverse conduction type power devices are accommodated in the package having the same fixed size, only the power devices, each of which has only the collector current or the controllable ON-current, are present. For example, in the IEGTs, the number of IEGT chips and the number of diode chips to the total number of chips is determined, and also in the GCTs, the occupancy ratio of the GCT region and the diode region to the total area of the silicon wafers is also determined.
Therefore, as long as the semiconductor power converter apparatus is constituted by using the reverse conduction type power devices having packages with the same electrode area, it may have the one and only forward convertable electric power and reverse convertable electric power. In other words, in order that the semiconductor power converter apparatus for forward conversion electric power and reverse convertable electric power, which are different from each other, may be constituted by using the conventional reverse conduction type power devices, the reverse conduction type power devices which are accommodated in the packages having different electrode areas and which are different in the collector current or the controllable ON-current from each other need to be applied to the semiconductor power converter apparatus.
In addition, since the reverse conduction power devices having different electrode areas must be cooled using different heat sinks or cooling fins, there arises the problem that it is impossible that the structures which are physically identical to one another are applied thereto to construct the semiconductor power converter apparatus, and hence the cost of the power converter system is increased.
In addition, in the case where the motor is driven by the semiconductor power converter apparatus employing the conventional reverse conduction type power devices, there arises the problem that the maximum capacity of the drivable motor is reduced.
This problem will now be described in detail while quoting the power converter system employed as adjustable speed
Fujii Toshiyuki
Okayama Hideo
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
Sterrett Jeffrey
LandOfFree
Asymmetrical power converting apparatus employing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Asymmetrical power converting apparatus employing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Asymmetrical power converting apparatus employing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3181836