Cascaded Current-Voltage H Repetitive Control - Control of Power Inverters in Renewable Energy and Smart Grid Integration - page 136

27% for the cascaded current-voltage H ∞

of the grid current was 2 . repetitive controller and

09% for the PR controller. In this experiment, the current-voltage H ∞ repetitive controller
outperformed the PR current- H ∞ voltage controller. Note that the grid was cleaner when the
PR current- H ∞ voltage controller was tested.

5 .

6.6.2.2 With a Resistive Load

The experimental results of the grid-connected inverter with the balanced resistive local load
connected to the system are shown in Figure 6.12 for the cascaded current-voltage H ∞
repetitive controller (left column) and the PR current- H ∞ repetitive voltage controller (right
column). When the resistive local load was connected, the recorded local load voltage THD
was 1

.

21% for the cascaded current-voltage H ∞ repetitive controller and 0

.

97% for the PR

. .

controller, while the grid voltage THD was 1 8% and 0 95% respectively. The grid current

THD was 2 24% for the

PR controller. The performance of both controllers remains almost unchanged in comparison
to the previous experiment without a local load. The cascaded current-voltage H ∞ repetitive
controller again outperformed the PR current- H ∞ voltage controller. Note that the grid was
cleaner again when the PR current- H ∞ voltage controller was tested.

. 32% for the cascaded current-voltage H ∞ repetitive controller and 5 .

6.6.2.3 With a Non-linear Load

The experimental results of the grid-connected inverter with a non-linear load connected to the
system are shown in Figure 6.13 for the current-voltage H ∞ repetitive controller (left column)
and the PR current- H ∞ repetitive voltage controller (right column). The recorded THD of
the local voltage was 2 22% for the cascaded current-voltage H ∞ repetitive controller and .

2 . 97% for the PR controller, while the grid voltage THD was 1 . 72% and 0 . 93% respectively.

The THD of the grid current was 5 97% respectively. The cascaded current-

voltage H ∞ repetitive controller again clearly outperformed the PR current- H ∞ voltage
controller.

. 35% and 7 .

6.6.2.4 With an Unbalanced Load

The inverter local load voltage, the filter inductor current and the grid current are shown
in Figure 6.14(a) for the current-voltage H ∞ repetitive controller (left column) and the PR
current- H ∞ repetitive voltage controller (right column). The spectra of the inverter local
load voltage and the grid current are shown in Figures 6.14(b) and 6.14(c), respectively, for
the current-voltage H ∞ repetitive controller (left column) and the PR current- H ∞ repetitive

voltage controller (right column). The recorded local load voltage THD was 1 . 09% in the

case with the current-voltage H ∞

repetitive controller and 1 . 00% in the case with the PR

controller, while the grid voltage THD was 1 . 77% and 0 . 92% respectively. The grid current

THD was 2 20% respectively. Both strategies injected balanced currents into the

grid although the local load was not balanced.

. 36% and 5 .