Current Proportional–Integral Control - Control of Power Inverters in Renewable Energy and Smart Grid Integration - page 243

5 5

i ref i a i ref i a

2.5 2.5

0 0

−2.5 −2.5

−5 −5

1.5 1.5

e i e i

1 1

0.5 0.5

0 0

−0.5 −0.5

−1 −1

−1.5 −1.5

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Time [s] Time [s]

(a) Grid output current , its reference and current tracking error

5 5

THD of i a =4.76% THD of i a =4.38%

4 4

3 3

2 2

1 1

0 0

0 5 10 15 20 25 30 0 5 10 15 20 25 30

Harmonics order Harmonics order

(b) Spectra of the grid output current

Figure 15.3 Experimental results for a PI controller without a local load implemented in the dq frame
(left column) and its equivalent in the abc frame (right column)

5 5

i ref i a i ref i a

2.5 2.5

0 0

−2.5 −2.5

−5 −5

1.5 1.5

e i e i

1 1

0.5 0.5

0 0

−0.5 −0.5

−1 −1

−1.5 −1.5

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08

Time [s] Time [s]

(a) Grid output current , its reference and current tracking error

5 5

THD of i a =5.7% THD of i a =4.94%

4 4

3 3

2 2

1 1

0 0

0 5 10 15 20 25 30 0 5 10 15 20 25 30

Harmonics order Harmonics order

(b) Spectra of the grid output current

Figure 15.4 Experimental results for a PI controller with a balanced resistive local load implemented
in the dq frame (left column) and its equivalent in the abc frame (right column)