Predictive Control of Three Phase AC/DC Converters

ILd 1 sL+RSd - UDCUPd ULd
iload ic
14 CHAPTER 2. VOLTAGE SOURCE CONVERTER
U Lβ = L dI Lβ
dt
+ RI Lβ + U P β (2.16)
C dU DC
= 3 dt 2 (I LαS α + I Lβ S β ) − i load (2.17)
Equations (2.15)–(2.17) can be represented as a block diagram in stationary
coordinates as shown in Fig. 2.8.
2.2.3 VSC Model in Rotating Coordinates
Model in stationary coordinates presented in previous subsection, can be transformed
into a two phase model in synchronously rotating dq (App. A.2) coordinates.
After transformation, VSC model can be described as:
U Ldq = L dI Ldq
dt
+ RI Ldq + U P dq + jω L LI Ldq (2.18)
C dU DC
= 3 dt 2 R ( I Ldq S ∗ dq)
− iload (2.19)
where: U Ldq , I Ldq , U P dq , S dq are space vectors in rotating dq coordinates. Note
that, after transformation additional block appears in (2.18), where ω L is angular
frequency of line voltage.
After decomposition of space vectors into d and q components, one obtains:
1 sL+R ILq - UDCUPq ULq
1 sCUDC - ωLL -
Figure 2.9: Block scheme of VSC in rotating dq coordinates
32IDC
U Ld
+ RI Ld + U P d − ω L LI Lq
= L dI Lq
dt
+ RI Lq + U P q + ω L LI Ld
(2.20)
dt
= I Ld S d + I Lq S q − i load
U Lq
C dU DC
= L dI Ld
dt
Sq
Figure 2.9 presents block scheme of VSC in rotating dq coordinates.