Analysis and Modeling of a New Coupled-Inductor Buck-Boost DC-DC Converter for Renewable Energy Applications

A new coupled-inductor buck-boost converter (CIBuBoC) is proposed in this article. In the proposed CIBuBoC, an ultra-high step-up/step-down voltage conversion ratio and step-up/step-down boundary adjustment are achieved compared to the other related buck-boost converters using two power switches with simultaneous operation along with a coupled inductor. This circuit has a simple structure with two cascade semistage and some features including ultra-extended output voltage, continuous input current with low ripple, positive polarity of the output voltage, and common ground. These features make the CIBuBoC more suitable for many applications such as photovoltaic systems. Moreover, the voltage stress across each power switch is much lower than the other buck-boost converters, which led to power mosfets selection with lower drain-source on-resistance (R-ds). Therefore, the proposed converter has also enough high efficiency. All steady-state and stress analysis, and also, comparisons with other related converters in continuous conduction mode are provided in detail. Also, using the state-space averaging technique, the low-frequency behavior of the proposed CIBuBoC is studied completely. Experimental results of a 100-W step-up 30-200 V and a 35-W step-down 30-22 V confirm the theoretical advantages of the proposed circuit.