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Due to the extensive role of nonisolated high step-up dc–dc converters (NHSDC)s in industrial applications and academic research works, many of these pulsewidth modulation converters have been presented in recent years. For each of these NHSDCs, some claims are introduced to verify its capabilities and features, which have been investigated in some review papers with different frameworks. Dissimilar to previous review papers, which have focused on the classification and derivation of voltage boosting techniques, this article aims to evaluate the converters from various topological and operational points of view and determine the superiority of each technique and converter according to applications. Some of these metrics are voltage gain, stresses, ripple, cost, power density, weight, size, control complexity, and components count, which lead to a comprehensive comparative study. Then, as the main purpose of this article, the effectiveness of these metrics is assessed to show how well they can lead us to fair comparison results. Moreover, some new figures of merit are proposed in this article to provide a helpful guideline in power electronic converters comparison studies. Finally, the feasibility discussion of single- and multiobjective figures of merit is followed by a general practical conclusion and outlook about the NHSDC structures.

The complicated resonant operations of class ${\Phi} _{2}$ topology bring challenges for accurate design and performance optimization, hindering the full utilization potential of converters. Considering the narrow design freedom in traditional methods with almost fixed duty cycle $D$, this article widens the design options of push–pull class ${\Phi} _{2}$ converters through frequency-harmonic analysis. A full selection freedom of $D\in (0,0.5)$ is discussed analytically, providing ample space for optimization based on any required performance indices. From 1.98E5 analytical results, we found six numerical equations that fully decouple the interconnected relations between each circuit parameter and $D$. The proposed numerical method allows rapid circuit design and component selection with a high accuracy regardless of the system power or load voltage. Parasitic effects are discussed and incorporated into the design approach as correction steps. Finally, we introduce performance analysis based on an example wireless power transfer (WPT) system, providing in-depth studies on the optimization regarding efficiency, power output capability, and component selection. Experimental results validate the accuracy and efficiency of the proposed design method based on a 100-W WPT system at 6.78 MHz frequency. Both inverter and rectifier present load-independent soft-switching operations, with converter efficiency over 93%. The system provides 83% dc–dc efficiency at full load.