*5.2. Experimental Results*

The inverter line to ground, line to line, line to neutral, line to center and center to ground outputs are shown in Figure 10. For *Ma* = 1.3, the waveforms for *Vag*, *Vbg* and *Vcg* have six symmetric voltage levels with the highest value of 100 V, as shown in Figure 10a. It should be addressed that the experimental results are presented following the RGB color format, which means all the waveforms of phase *a* are represented by red color, while the waveforms of phase *b* and phase *c* are represented by a green and blue color, respectively.

The waveforms of *Vab*, *Vbc* and *Vca* are composed of 11 voltage steps with a peak value of 100 V, as depicted by Figure 10b. In Figure 10c, the inverter line to neutral *VaN* reached its peak value of 63 V with 16 voltage steps, while the waveform of *Vao* attained the peak voltage of 80 V producing nine voltage levels as shown in Figure 10d. From Figure 10e, four different voltage values are taken from inverter mid-point to ground *Vog*, with the peak value of 80 V. Then, within a full cycle of *Vag*, a repetition occurs three times. In Figure 10f,g, the proposed MLI's line to line output voltage at modulation index, *Ma* = 1.15 and 0.98 are depicted, respectively. The performance of the proposed MLI becomes the same as that of a traditional two-level inverter when *Ma* = 0.8, as shown in Figure 10h. The harmonic spectrum for the waveforms of inverter line to line voltage and load current at *Ma* = 1 are depicted in Figure 11.

**Figure 8.** Laboratory setup of the hardware prototype.

**Figure 9.** Control block diagram.

**Figure 10.** For *Ma* =1.3, the MLIs are: (**a**) line to ground voltages, (**b**) line to line voltages, (**c**) line to neutral voltage, (**d**) line to mid-point voltage and (**e**) line to ground and mid-point ground voltages, (**f**) For *Ma* =1.15, line to line voltages, (**g**) For *Ma* = 0.98, line to line voltages, (**h**) For *Ma* = 0.8, line to line voltages. **Figure 10.** For *Ma* =1.3, the MLIs are: (**a**) line to ground voltages, (**b**) line to line voltages, (**c**) line to neutral voltage, (**d**) line to mid-point voltage and (**e**) line to ground and mid-point ground voltages, (**f**) For *Ma* =1.15, line to line voltages, (**g**) For *Ma* = 0.98, line to line voltages, (**h**) For *Ma* = 0.8, line to line voltages.

The waveforms of *Vab*, *Vbc* and *Vca* are composed of 11 voltage steps with a peak value of 100 V, as depicted by Figure 10b. In Figure 10c, the inverter line to neutral *VaN* reached its peak value of 63 V with 16 voltage steps, while the waveform of *Vao* attained

According to Figure 11, both spectrums do not contain any triplen harmonics such as 3rd, 9th and 15th harmonics. Furthermore, all even harmonics are eliminated because

ure 10e, four different voltage values are taken from inverter mid-point to ground *Vog*, with the peak value of 80 V. Then, within a full cycle of *Vag*, a repetition occurs three times. In Figure 10f,g, the proposed MLI's line to line output voltage at modulation index, *Ma* = 1.15 and 0.98 are depicted, respectively. The performance of the proposed MLI becomes the same as that of a traditional two-level inverter when *Ma* = 0.8, as shown in Figure 10h. The harmonic spectrum for the waveforms of inverter line to line voltage and

load current at *Ma* = 1 are depicted in Figure 11.


**Figure 11 Figure 11.** Harmonic spectrum of load current (yellow) and line to line voltage (green).

According to Figure 11, both spectrums do not contain any triplen harmonics such as 3rd, 9th and 15th harmonics. Furthermore, all even harmonics are eliminated because the MLI's output voltage and load current have obtained symmetry. %THD for the load current is only 5.8%, while the THD for MLI's line to line voltage is 12.3%.
