Control circuit for multiphase inverter apparatus

Details Control circuit for multiphase inverter apparatus Control circuit for multiphase inverter apparatus

2001-11-05

2003-05-06

Sherry, Michael (Department: 2838)

Electric power conversion systems

Current conversion

With condition responsive means to control the output...

C363S131000, C318S768000, C318S801000, C318S806000

Reexamination Certificate

active

06560130

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control circuit for instantaneous waveform control power converting apparatus for controlling an instantaneous output current, the power converting apparatus being, for example, a sine wave voltage outputting inverter including a motor driving inverter, a high power factor converter, an active filter, and an LC filter. More specifically, the present invention relates to a control circuit including of a plurality of switching elements which perform a plurality of switching operations within one cycle.
2. Description of the Related Art
Referring now to drawings, a description will be made of a conventional control circuit used in a power converting apparatus.
FIG. 17
is a diagram for showing an arrangement of the conventional control circuit designed for a power converting apparatus, which is described in, for example, the Japanese publication entitled “CURRENT CONTROL TYPE PWM INVERTER CAPABLE OF SUPPRESSING HIGHER HARMONIC AND OF REALIZING HIGH-SPEED CURRENT RESPONSE” of Japanese Electric Institute Publication VOL. 12B, No. 2 (1986), on pages 9 to 16. It should be noted that the arrangement of
FIG. 17
is indicated by rewriting the construction of the conventional control circuit of the inverter described in the above-explained Japanese publication in a similar form to that of the present invention.
In
FIG. 17
, reference numeral
1
indicates a three-phase inverter main circuit, reference numeral
2
indicates a load such as a motor, reference numeral
4
represents a DC power supply, and symbols
10
U,
10
V;
10
W indicate current sensors for detecting an inverter current. Also, reference numeral
801
shows a three-phase sine wave current command generating circuit, reference numeral
802
shows a current deviation vector detecting circuit, reference numeral
803
is a back electromotive force predicting circuit for predicting back electromotive forces VBOU, VBOV, VBOW which are produced across the load, reference numeral
804
shows a PWM pattern table circuit, and reference numerals
851
U,
851
V,
851
W indicate adders/subtracters.
Also, in
FIG. 17
, reference numerals
21
U,
21
V,
21
W show internal inductances of the load
2
, and reference numerals
22
U,
22
V,
22
W show internal-induced voltages of the load
2
.
FIG. 18
is a diagram for representing the arrangement of the three-phase inverter main circuit
1
.
As indicated in
FIG. 18
, this three-phase inverter main circuit
1
is arranged by, for instance, a full-bridge circuit by employing switching elements S
1
to S
6
.
Next, operations of the conventional control circuit used in the power converting apparatus will now be explained with reference to drawings.
In
FIG. 17
, the control circuit is arranged as a current control loop for performing an instantaneous current control. The adders/subtracters
851
U,
851
V,
851
W calculate current deviations &Dgr;iU, &Dgr;iV, &Dgr;iW between current command values IAU*, IAV*, IAW*, and inverter currents IAU, IAV, IAW detected by the current sensors
10
U,
10
V,
10
W. The current command values correspond to outputs of the three-phase sine wave current command generating circuit
801
, and should be supplied by the inverter. The back electromotive force predicting circuit
803
predicts the back electromotive forces VBOU, VBOV, VBOW produced across the load from the current deviations &Dgr;iU, &Dgr;iv, &Dgr;iW so as to acquire a back electromotive force vector VB, and then, detects which region selected from a region [I] to a region [VI] indicated in
FIG. 19
this back electromotive force vector VB is present.
FIG. 19
is a diagram for showing the six regions [I] through [VI] which are segmented by
8
sorts of voltage vectors V
0
to V
7
, which are outputted in response to conditions of the switching elements of the inverter
1
.
The current deviation vector detecting circuit
802
obtains a current deviation vector &Dgr;I from the above-explained current deviations &Dgr;iU, &Dgr;iV, &Dgr;iW, and then, detects which region selected from regions (
1
) to (
7
) shown in
FIG. 20
this current deviation vector &Dgr;I is present.
For the sake of convenient explanations, circled numerals which are shown in the respective drawings are described as (1), (2), (3) etc., in this specification.
A predetermined allowable range which is defined based upon precision of a current control is set with respect to the current deviation vector &Dgr;I and the region (
7
) indicates that this current deviation vector &Dgr;I is located in the allowable range. The regions (
1
) to (
6
), which are located at an outer circumference of this region (
7
), represent that the current deviation vector &Dgr;I is located outside the allowable range.
The PWM pattern table circuit
804
selects switching modes k
0
to k
7
from both the region of the back electromotive force vector VB and the region of the current deviation vector &Dgr;I in accordance with a table of FIG.
22
. The PWM pattern table circuit
804
determines switching conditions of the six switching elements employed in the three-phase inverter
1
shown in
FIG. 21
based upon these switching modes k
0
to k
7
.
For instance, in such a case that the back electromotive force vector VB is present in the region [I], this PWM pattern table circuit
804
selects the switching mode k
1
when the current deviation vector &Dgr;I is located in either the region (
1
) or the region (
5
). Also, this PWM pattern table circuit
804
selects the switching mode k
3
when the current deviation vector &Dgr;I is located in either the region (
2
) or the region (
3
). Also, this PWM pattern table circuit
804
selects the switching mode k
0
or k
7
when the current deviation vector &Dgr;I is located in either the region (
4
) or the region (
6
). Also, the PWM pattern table circuit
804
selects a proper switching mode such that this switching mode is directly kept when the current deviation vector &Dgr;I is located in the region (
7
).
The three-phase inverter
1
turns ON/OFF the switching elements in response to the switching command of the PWM pattern table circuit
804
so as to control the inverter currents IAU, IAV, IAW.
Next, an explanation is made of how the current deviation vector &Dgr;I is transferred under the above-explained control operation.
For example, the following case will now be considered. That is, in
FIG. 19
, the back electromotive force vector VB is present at VL with the region [I]. Also, in
FIG. 20
, the current deviation vector &Dgr;I is present at &Dgr;Ia within the region (
1
).
From
FIG. 22
, the switching mode k
1
is selected under this condition, and the current deviation vector &Dgr;I is moved along the direction of VL
1
equal to a difference between VL and V
1
shown in
FIG. 19
, and then, is entered from &Dgr;Ia of
FIG. 20
into the region (
7
) within the allowable range.
However, in such a case that the current deviation vector &Dgr;I is located at &Dgr;Ib shown in
FIG. 20
, the switching mode k
1
is similarly selected, whereas the current deviation vector &Dgr;I is not entered into the allowable range, but is once moved to the region (
3
). Subsequently, since the switching mode k
3
is selected based upon both the region [I] and the region (
3
), the current deviation vector &Dgr;I is moved along the direction of VL
3
, and then is entered into the region (
7
) which is located in the allowable range.
In this case, if the switching mode k
3
is selected at such a time instant when the current deviation vector &Dgr;I is present at &Dgr;Ib, then the current deviation vector &Dgr;I is moved along a dotted line of FIG.
20
. As a result, it is most probably possible to enter the current deviation vector &Dgr;I into the region (
7
) in the allowable range by changing the switching mode one time.
The above-described conventional control circuit for the power converting apparatus has the following problem. That is, since there is such a

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