Current Deadbeat Predictive Control - Control of Power Inverters in Renewable Energy and Smart Grid Integration - page 261

Table 17.1 Comparison of current controllers in the grid-connected mode
without a local load

Controller Current i a THD [%] Grid voltage v ga THD [%]

H ∞ repetitive

1 . 03 1 . 57

PR 3 . 84 1 . 45

PI 4 . 38 1 . 52

DB 3 . 65 1 . 61

The current controllers discussed in Chapters 3 and 15-17 were compared and their cor-
responding values of THD of the grid current are listed in Table 17.2. It can be seen that the
current H ∞ repetitive controller considerably outperformed the other controllers.

17.3.1.3 With an Unbalanced Load

In this experiment, an unbalanced resistive local load with R A = 12 , R B =∞ and

was connected to the system. The grid output current reference I d was set at
2 A (after connecting the inverter to the grid) and the reactive power was set at 0 Var ( I q

R C = 12

0).
The output current i a , reference current i ref and the corresponding current tracking error e i in
the steady state are shown in the left column of Figure 17.4. The tracking performance of the
controller remained satisfactory.
The current controllers discussed in Chapters 3 and 15-17 were compared and their cor-
responding values of THD of the grid current are listed in Table 17.3. It can be seen that the
current H ∞ repetitive controller considerably outperformed the other controllers.

=

17.3.1.4 With a Non-linear Load

In this experiment, a three-phase uncontrolled rectifier loaded with an LC filter L = 150 μ H,

C was connected to the system. The grid output current

reference I d was set at 2 A (after connecting the inverter to the grid) and the reactive power
was set at 0 Var ( I q

= 1000 μ F and a resistor R = 20

0). The output current i a , reference current i ref and the corresponding
current tracking error e i in the steady state are shown in the right column of Figure 17.4. The
tracking performance worsened and the current THD increased considerably.
The current controllers discussed in Chapters 3 and 15-17 were compared and their cor-
responding values of THD of the grid current are listed in Table 17.4. The THD of the grid
current obtained by the current H ∞ repetitive controller is below one-third of those obtained
from the other current controllers.

=

Table 17.2 Comparison of current controllers in the grid-connected mode with a
resistive local load

Controller Current i a THD [%] Grid Voltage v ga THD [%]

H ∞ Repetitive 1 . 53 1 . 63

PR 5 . 79 1 . 41

PI 4 . 93 1 . 41

DB 5 . 8 1 . 59