Predictive Control of Three Phase AC/DC Converters

Sector 2
54 CHAPTER 4. PREDICTIVE DIRECT POWER CONTROL
line voltage space vector position. The voltage plane is divided into twelve subsectors,
exactly the same as in case of ST-DPC, see Fig. 3.9. The smallest current
ripples can be achieved by application sequence of neighboring VSC vectors.
Figure 4.9 shows an example of vector selection. Line voltage space vector
is located in the first sector, so the switching sequence of U P is set to {1, 2, 7}.
Table 4.4 summarizes U P sequences for all sectors.
β
Sector 3
(110)
UP2
(000)
UP0
(111)
UP7
α
UL
(100)
UP1
(101)
1
Sector 11 Sector 12
UP6
Figure 4.9: Converter voltage vector U P selection in 1st sector
Figure 4.10 shows graphical representation of U P sequences for all sectors.
As it can be seen in Fig. 4.10, switching table (Tab. 4.4) has been constructed in
order to reduce transistors switching loses. Note that, the U P sequence has been
chosen in such way that VSC leg switchings do not happen during maximum line
current conduction, and there are only two switchings per sampling time T s .
4.6.4 Voltage Vectors Application Times
Taking into account (4.36) and constant switching frequency requirement, control
method has to determine t 1 , t 2 and t 3 voltage vectors application times.
The predicted power values at the end of sampling time P P 6 , Q P 6 are considered
as a referenced ones P ref , Q ref .
P ref = P P 6
Q ref = Q P 6
(4.37)