**6. Comparative Study**

The section present a comparative table between NPC and CMLI schemes. As mentioned above, at present, FC-based topology is not generally used in PV applications. The comparison takes into account different aspects such as input voltage value, switching frequency, control strategy, efficiency and leakage current and only includes recent works. Other recent works establish different comparisons according to the topic they address. The authors in [112] show five control methods based on SMC, the comparison is made considering the topology, the modes of operation and the number of sensors required. Lee in [113], establishes a comparative analysis of recent topologies based on cascade inverters, which reveals that the *S*3*CM* proposed in the document achieves the reduction of the switch count.

It can be appreciated that the switching frequencies rarely exceed 15 kHz. Increasing the switching speed causes an increase in the system losses and the THD. There is a compromise between the number of output levels and the speed of the switches. Increasing the number of power levels imply slower switching frequency.

All the works presented comply with the two most important grid connection standards. These standards establish a maximum leakage current and THD of 300 mA and 5%, respectively. Compliance with standards largely depends on the strategy of modulation employed. From the data presented, it is observed that the SVPWM technique and its variants are the most recurrent when it is required to decrease the voltage in common-mode topologies.

Another element that is noted is the use of inverters with 3 output levels. The authors note a compromise between the number of levels and the number of elements in their topology. Generally, with 3 levels, satisfactory results are obtained, as showed in Table 13.


**Table 13.** Multilevel inverters used on PV applications.

