基于Zeta拓扑的单级单相交流链路通用逆变器

Single-phase inverters are widely used in numerous applications such as residential photovoltaic (PV) systems. These types of inverters are mostly realized by a two-stage dc/dc/ac conversion. Specifically, in the low-power grid-connected residential PV applications, the dc-side voltage level is typically lower than the ac grid peak voltage, which necessitates the employment of an additional step-up dc–dc converter. This requirement increases the converter’s overall cost and reduces the power density. More importantly, this type of two-stage conversion utilizes a bulky electrolytic capacitor, which suffers from critical reliability and lifetime issues, as an intermediate dc-link between the input and output stages. This article proposes a novel single-phase article, named Zeta-based ac-link universal inverter, which is derived from the conventional dc–dc Zeta topology. The proposed converter is capable of providing an adjustable step-up/down voltage gain ratio with variable frequency, all in an indirect single stage of power conversion. It uses a small series film capacitor and a small parallel inductor as the ac-link elements. The presented topology offers several advantages over the conventional two-stage structure, such as higher reliability and longer lifespan due to eliminating the large electrolytic dc-link capacitor and less overall component count, as well as higher power density and compactness due to using small high-frequency passive components. Besides, as the proposed converter features a high-frequency link network, a compact high-frequency transformer can be employed at the link for isolation purposes, which further shows the superiority of this topology. The proposed topology and corresponding control principles are discussed in this article, and its performance is verified through simulations and experiments.