Predictive Control of Three Phase AC/DC Converters

010UP3
β
23
Figure 2.4: Representation of VSC AC-side voltage as space vector
111
110
10 CHAPTER 2. VOLTAGE SOURCE CONVERTER
AC-side voltage can be described as a complex space vector (2.3).
U P (i) =
{
2
3 U DC e j(i−1) π 3 for i = 1 . . . 6
0 for i = 0, 7
(2.3)
Active vectors correspond to phase voltage in relation 1 3 and 2 3
to the DC-link
voltage U DC . Zero vectors apply zero voltage at the AC-side of converter, because
all three branches are connected to positive or negative DC-link bus.
011
UP1 UDC UP4 α UP6 UP0,7 100 000
UP5
001
Voltage Source Converter (VSC) can be represented in different coordinate
systems. Figure 2.5 shows single phase representation of VSC where: U L is space
vector of line voltage, I L is space vector of line current, U
101
P is space vector of VSC
input voltage. The U P voltage is controllable, and depends on applied voltage
vector (see (2.3) and Fig. 2.4). Due to changes of U P magnitude and phase,
line current can be controlled by voltage drop on the input choke. As it can be
noticed, input choke is essential part of the converter, because it brings current
source character, and provides boost feature of converter.
Figure 2.5: Single phase representation of VSC
R
IL UP
Figure 2.6 presents general phasor diagrams for rectification and inverting mode
with and without unity power factor operation.
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