*2.2. Description of Topologies*

The PV system considered was built based on two different approaches: on the 2L QZSI (Figure 2) and on the 3L NPC QZSI (Figure 3). The 2L QZSI proposed in Reference [5] is described in detail as a three-phase application for PV systems. The main parts of the topology include the QZS network represented by L1, D1, C1, L2, and C2; the FB 2L inverter based on MOSFET switches S1, S2, S3, and S4; and the output filter LF1, CF, and LF2 feeding the load or connected to the grid. Detailed discussions and explanations on the 2L QZSI for a single-phase PV application as well as the control approaches, including SBC, MBC, constant boost control and their modifications, are provided in [31,33–35]. In this study, SBC was used for generating the ST states.

**Figure 2.** The 2L QZS inverter.

The 3L NPC QZSI (Figure 3) was proposed and discussed in detail as a single-phase application in Referene [6]. The study also provides the main design guidelines and the experimental results. The main parts of the topology include the QZS network, which in this case was divided by a neutral point into two symmetrical parts, represented by L1, C1, D1, L2, C2 and L3, C3, D2, L4, and C4; an FB 3L inverter with switches S1, S2, S3, S4, S5, S6, S7, and S8; clamping diodes D3, D4, D5, and D6; and an output filter LF1, CF, and LF2 feeding the load or connected to the grid.

The topology was proved as an efficient PV converter [37–39], including maximum power point tracking (MPPT) implementation along with continuous input current [37] and operation in the grid-connected mode [38,39]. The implementation of this topology under different control approaches is discussed in detail in References [6,7,32,38,39]. In our study, the SBC approach was used for generating the ST states.

**Figure 3.** The 3l NPC QZS inverter.
