**2. Proposed Converter**

The proposed converter is derived from the noncascading I–IIA structure, which was introduced by Tse et al. in [32,33]. The structure, shown in Figure 1, relates two unidirectional ports (source and load), a bidirectional port (storage element, *C*1), and two general blocks (*A* and *B*), which are formed with basic switching DC-DC cells.

The development of a high-gain switching converter is based on the implementation of two basic switching cells. In block *A*, a boost cell is implemented with inverted output terminals, as shown in Figure 2a. This boost cell changes the voltage polarity in the storage element *C*1, which assures a negative voltage in the input port of block *B*. In turn, a buck-boost cell, as depicted in Figure 2b, provides a positive voltage in the output port of the I–IIA structure.

**Figure 2.** Nonisolated basic switching cells: (**a**) boost; (**b**) buck-boost.

The proposed quadratic buck-boost converter is shown in e Figure 3. This topology uses two active switches, *S*<sup>1</sup> and *S*3; two passive switches, *S*<sup>2</sup> and *S*4; two inductors, *L*<sup>1</sup> and *L*2; a storage element, *C*1; and an output capacitor, *C*2. Additionally, *E* represents a voltage source and the load is modeled by a resistance *R*.

**Figure 3.** Proposed quadratic buck–boost converter.

Notably, other topologies with high gain or quadratic voltage conversion ratio have been developed under this kind of noncascading structure for PV applications, as discussed in [34–36]. Nevertheless, different procedures exist to develop topologies with specific high voltage gain, as stated in [37].
