The top and bottom switches are working in a complementary mode; for example, if the
top switch S
At
is on, then the corresponding bottom switch S
Ab
is off, and vice versa.
Considering that the value 1 is assigned to the ON state of the top switch, and value 0 is
assigned to the ON state of the bottom switch, the switching vector [a, b, c]
T
can be
defined. Creating of such vector allows for numerical definition of all possible switching
states. Phase-to-phase voltages can then be expressed in terms of the following states:
Equation 29
where U
DCBus
is the instantaneous voltage measured on the DC-bus.
Assuming that the motor is completely symmetrical, it is possible to write a matrix
equation, which expresses the motor phase voltages shown in
Equation 30
In a three-phase power stage configuration (as shown in
), eight possible
) are feasible. These states, together with the
resulting instantaneous output line-to-line and phase voltages, are listed in
.
Table 2-8. Switching patterns
A B C
U
a
U
b
U
c
U
AB
U
BC
U
CA
Vector
0 0 0
0
0
0
0
0
0
O
000
1 0 0
2U
DCBus
/3
-U
DCBus
/3
-U
DCBus
/3
U
DCBus
0
-U
DCBus
U
0
1 1 0
U
DCBus
/3
U
DCBus
/3
-2U
DCBus
/3
0
U
DCBus
-U
DCBus
U
60
0 1 0
-U
DCBus
/3
2U
DCBus
/3
-U
DCBus
/3
-U
DCBus
U
DCBus
0
U
120
0 1 1
-2U
DCBus
/3
U
DCBus
/3
U
DCBus
/3
-U
DCBus
0
U
DCBus
U
240
0 0 1
-U
DCBus
/3
-U
DCBus
/3
2U
DCBus
/3
0
-U
DCBus
U
DCBus
U
300
1 0 1
U
DCBus
/3
-2U
DCBus
/3
U
DCBus
/3
U
DCBus
-U
DCBus
0
U
360
1 1 1
0
0
0
0
0
0
O
111
The quantities of the direct-
α
and the quadrature-
β
components of the two-phase
orthogonal coordinate system, describing the three-phase stator voltages, are expressed
using the Clark transformation, arranged in a matrix form:
Chapter 2 Algorithms in detail
GMCLIB User's Guide, Rev. 2, 10/2015
Freescale Semiconductor, Inc.
37
Содержание DSP56800E
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