Power converter device

Details Power converter device Power converter device

2002-12-11

2004-06-08

Riley, Shawn (Department: 2838)

Electric power conversion systems

Current conversion

Using semiconductor-type converter

C363S141000

Reexamination Certificate

active

06747884

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a power converter device such as an inverter device for driving a motor at a variable speed, an uninterruptible power supply unit, or the like.
BACKGROUND ART
FIG. 11
is a view showing a configuration of an inverter device as a power converter device according to the related art.
In
FIG. 11
, reference numeral
30
is an AC power supply, reference numeral
31
is an inverter device, reference numeral
32
is a converter portion for converting the AC power into the DC power, and reference numeral
33
is a capacitor for smoothing the DC voltage. Also, reference numeral
34
is an inverter portion for inverting the DC power into the AC power that has the variable frequency and the variable voltage, the inverter portion having output power elements, which has self turnoff elements (referred to as “switching elements” hereinafter) Tr1, Tr2, Tr3, Tr4, Tr5, Tr6 and free wheeling diodes D1, D2, D3, D4, D5, D6. Also, Vuo is a potential of a connection point u between the switching elements Tr1 and Tr2, Vv0 is a potential of a connection point v between the switching elements Tr3 and Tr4, and Vw0 is a potential of a connection point w between the switching elements Tr5 and Tr6.
Also, reference numeral
35
is a control portion for ON/OFF-controlling the switching elements of the inverter portion
34
, and reference numeral
36
is a motor such as the induction motor that is driven at a variable speed as a load.
Also, reference numeral
40
is a CPU as an arithmetic circuit for receiving various commands such as an operation command, a speed command, etc. and various set values such as an accelerating/decelerating time, a V/f pattern, etc. as input signals, calculating an output frequency and an output voltage, and outputting switching signals Su1, Su2, Sv1, Sv2, Sw1, Sw2 to turn the switching elements ON/OFF. Also, reference numeral
41
is a memory as a storing means for storing various data such as the accelerating/decelerating times, a relational expression between the output frequency/output voltage, etc.
Also, reference numeral
42
a
to
42
f
are driving portions for amplifying the switching signals Su1, Su2, Sv1, Sv2, Sw1, Sw2, which are output from the control portion
35
, up to base signals having amplitudes that can drive the switching elements Tr1, Tr2, Tr3, Tr4, Tr5, Tr6.
As this output voltage controlling system, there are the pulse width modulation (abbreviated to “PWM” hereinafter) and the pulse amplitude modulation (abbreviate to “PAM” hereinafter). With reference to the example of the PWM system that the output voltage is controlled by changing time periods during which the switching elements Tr1, Tr2, Tr3, Tr4, Tr5, Tr6 of the inverter portion
34
are turned ON, explanation will be described hereinafter.
The CPU
40
receives various commands (not shown) such as the operation command, the speed command, etc. and various set values such as the accelerating/decelerating time, the V/f pattern, etc. stored in the memory
41
as the input signals, calculates the output frequency and the output voltage, and outputs the switching signals Su1, Su2, Sv1, Sv2, Sw1, Sw2 to turn the switching elements ON/OFF.
FIG. 12
is a view showing various waveforms of the inverter device in the PWM system according to the related art, wherein (a) is a view showing relationships between command voltage waveforms Vur, Vvr, Vwr in a U phase, a V phase, a W phase and a carrier wave Vtri, (b) is a view showing a command voltage waveform Vu at a connection point u between the switching elements Tr1 Tr2, (c) is a view showing a command voltage waveform Vv at a connection point v between the switching elements Tr3 and Tr4, (d) is a view showing a command voltage waveform Vw at a connection point w between the switching elements Tr5 and Tr6, and (e) is a view showing an inverter output voltage waveform Vuv=Vu−Vv.
The CPU
40
compares the command voltage waveforms Vur, Vvr, Vwr shown in (a) with the carrier wave Vtri, and then brings the switching elements into their ON state if the command voltage waveforms are larger than the carrier wave, and brings the switching elements into their OFF state if the command voltage waveforms are smaller than the carrier wave, as shown in (b), (c), (d).
Next, an operation of the inverter device according to the related art will be explained hereunder.
When the power supply is turned ON, the converter portion
32
converts the AC power of the AC power supply
30
into the DC power and smoothes this DC power by the capacitor
33
.
Also, the control portion
35
receives various commands such as the operation command, the speed command, etc. and various set values such as the accelerating/decelerating time, the V/f pattern, etc. as the input signals, calculates the output frequency and the output voltage, and outputs the switching signals Su1, Su2, Sv1, Sv2, Sw1, Sw2 to turn the switching elements ON/OFF.
Also, the inverter portion
34
converts the DC power into the AC power having the variable frequency and the variable voltage by ON/OFF-controlling the switching elements Tr1, Tr2, Tr3, Tr4, Tr5, Tr6 based on the switching signals Su1, Su2, Sv1, Sv2, Sw1, Sw2 output from the control portion
35
.
The AC power having the variable frequency and the variable voltage is supplied to the motor
36
, whereby this motor
36
can be driven at a variable speed.
FIG. 13
is a view showing output voltages of the inverter device according to the related art, wherein (a) is a view showing the voltage waveform Vu0 at the connection point u, (b) is a view showing the voltage waveform Vv0 at the connection point v, (c) is a view showing the voltage waveform Vw0 at the connection point w, and (d) is a view showing the voltage waveform of the output voltage Vuv0 (=Vu0−Vv0).
In
FIG. 13
, E is a command voltage, Vuo is a potential waveform of the connection point u between the switching elements Tr1 and Tr2, Vv0 is a potential waveform of the connection point v between the switching elements Tr3 and Tr4, Vw0 is a potential waveform of the connection point w between the switching elements Tr5 and Tr6, and VTr1_ON, VTr2_ON, VTr3_ON, VTr4_ON, VTr5_ON, VTr6_ON are saturation voltages, respectively when the switching elements (Tr1, Tr2, Tr3, Tr4, Tr5, Tr6) are turned ON.
As shown in
FIG. 13
, in the ON/OFF control of the switching elements (Tr1, Tr2, Tr3, Tr4, Tr5, Tr6), the saturation voltages (VTr1_ON, VTr2_ON, VTr3_ON, VTr4_ON, VTr5_ON, VTr6_ON) are present when the switching elements (Tr1, Tr2, Tr3, Tr4, Tr5, Tr6) are turned ON. Therefore, the potential Vu0 at the connection point u has an amplitude of E-VTr1_ON~VTr2_ON as shown in (a), the potential Vv0 at the connection point v has an amplitude of E-VTr3_ON VTr4_ON as shown in (b), and the potential Vw0 at the connection point w has an amplitude of E-VTr5_ON~VTr6_ON as shown in (c).
For this reason, the output voltage Vuv0 when the switching elements Tr1, Tr4 are turned ON is given as not Vuv0=E−0=E, but
Vuv0
=
(
Vu0
-
Vv0
)
=
(
E
-
VTr1_ON
)
-
VTr4_ON
=
E
-
(
VTr1_ON
+
VTr4_ON
)
.
In contrast, the output voltage Vuv0 (=Vu0−Vv0) when the switching elements Tr2, Tr3 are turned ON is given as not Vuv0=0−E=−E, but
Vuv0
=
(
Vu0
-
Vv0
)
=
VTr2_ON
-
(
E
-
VTr3_ON
)
=
(
VTr2_ON
+
VTr3_ON
)
-
E
.
In the inverter device according to the related art, the command voltage is supplied to the inverter as the input voltage as it is. Therefore, the amplitude of the output voltage does not have the amplitude of the command voltage E~−E, but the amplitude of the actual output voltage is in the range of
E
−(
VTr
1
—
ON+VTr
4
—
ON
)~
E
+(
VTr
2
—
ON+VTr
3
—
ON
),
whereby the part of the saturation voltages becomes the error.
It is possible to get the smooth output, in which the low order harmonics contained in the output voltage of the inverter is reduced by the PWM system. However, the command voltage is supplied to the inverter as the input voltage as it is, and thus the saturation vo

Affiliated with

Also associated with

Rating

Power converter device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Power converter device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power converter device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3357664