**2. Case Study System**

## *2.1. System Parameters and Specifications*

The PV system being considered for PV string application which could comprise 5 ... 10 PV panels with total power up to 1800 W. The PV panel SPR-200-BLK from SunPower was selected for the case study [41]. The main system and PV panels parameters are provided in Table 2 and typical P-V and I-V dependencies are shown in Figure 1. The operating power profile of the design solution according to the case study PV string is also depicted in Figure 1. In the input voltage range from 200 V to 400 V, the converter was assumed to operate with the rated input current of 5 A.

Depending on the operating conditions and the type of panels, the power conversion efficiency can vary, but is aimed to be in the range from 92% to 96%. The converter was aimed to operate at the rated (nominal) power of 1800 W, with its maximum efficiency of 97.1% in the nominal mode, which corresponds to the input voltage of 360 V. In this operating point, the converter has its highest CEC efficiency, which is over 96% for both topologies (2L QZSI and 3L NPC QZSI).


**Table 2.** Photovoltaic (PV) panel and system parameters.

**Figure 1.** PV string characteristics and system power profile.
