Predictive Control of Three Phase AC/DC Converters

3.4. DIRECT POWER CONTROL WITH SPACE VECTOR MODULATOR 27
(a)
1.5
From: P ref
To: P 0
System: PQ_PI
I/O: P{ref} to P0
Peak amplitude: 1.41
Overshoot (%): 41.1
At time (sec): 0.000849
(b)
1.5
System: PQ_PI
I/O: P{ref} to P0
Peak amplitude: 1.07
Overshoot (%): 7.19
At time (sec): 0.00148
From: P ref
To: P 0
1
1
0.5
System: PQ_PI
I/O: P{ref} to P0
Rise Time (sec): 0.000316
System: PQ_PI
I/O: P{ref} to P0
Settling Time (sec): 0.00247
0.5
System: PQ_PI
I/O: P{ref} to P0
Rise Time (sec): 0.000699
System: PQ_PI
I/O: P{ref} to P0
Settling Time (sec): 0.00201
0
0 0.5 1 1.5 2 2.5 3 3.5
x 10 −3
0
0 0.5 1 1.5 2 2.5 3 3.5
x 10 −3
Figure 3.12: Step response of active power control loop in DPC-SVM: (a) without
prefilter, (b) with prefilter
(a)
1.5
Discretized Step Response From:P ref
to P 0
(b)
1.5
Discretized Step Response From:P ref
to P 0
1
1
0.5
0.5
0
1 1.0005 1.001 1.0015 1.002 1.0025 1.003 1.0035
Time (sec)
0
1 1.0005 1.001 1.0015 1.002 1.0025 1.003 1.0035
Time (sec)
Figure 3.13: Step response of discretized active power control loop in DPC-SVM:
(a) without prefilter, (b) with prefilter
For DC-link voltage controller design, inner active power control loop can be
represented as a first order transfer function where VSC time constant T I depends
on inner power control loop.
T I = 4τ t (3.26)
Practical control implementation requires additional low pass filter T fUDC on
measured DC-link voltage, which reduces voltage pulsations caused by transistors
switching.
T fUDC = 0.003[s] (3.27)
Control loop can be modeled as shown in Fig. 3.14. Symmetry optimum (SO)
design method has been used for controller parameters calculation, which gives:
K P U =
C
2(T I + T fUDC )
(3.28)