**6. Modulation Techniques**

Modulation techniques typically involve a carrier signal and a modulator waveform with different waveform parameters. By adjusting the characteristics of a carrier signal using a reference signal, modulation can be used to control the switching time of the switches in the MLIs. Harmonic reduction and switching losses, both of which can be controlled by modulation methods, are two of the things that affect the overall efficiency of a multilevel inverter. The modulation index plays an important role in all control systems. The THD fluctuates with a modulation ratio (either too much or too little). There are a variety of methods in the literature that may be used based on the switching frequency, whether fundamental or high frequency. Figure 27 shows several MLI modulation control techniques.

**Figure 27.** Multilevel inverter modulation control techniques.

Table 10 provides a comprehensive study of conventional MLI topologies; Table 11 offers the merits and demerits of new multilevel inverter topologies; Table 12 provides the applications of MLI topologies; and Table 13 provides information on a comprehensive examination study of traditional and new multilevel inverter topologies.

**Table 10.** The advantages of switched-capacitor multilevel inverters (SC-MLIs) over conventional multilevel inverters.



#### **Table 10.** *Cont*.

#### **Table 11.** Benefits and restrictions of new multilevel inverter topologies.



#### **Table 11.** *Cont*.

#### **Table 12.** Applications of MLI topologies.



#### **Table 12.** *Cont*.

**Table 13.** Comprehensive examination study of traditional and new multilevel inverter topologies (*nlevel* = number of levels in phase voltage).



**Table 13.** *Cont*.

(' ∗ ' indicates the multiplication operation).
