A Coupled Inductor Based High Boost Inverter with Sub-unity Turns-Ratio Range

Abstract

Voltage source inverter cannot provide an output voltage higher than its input and needs a dead-time scheme for its switches to prevent dc-link short circuit due to spurious turn-on of switches by electromagnetic interference (EMI). Impedance source inverters have eliminated these disadvantages by providing boost functionality with improved EMI immunity. Coupled inductor-based impedance source inverters provided increased gain at the expense of increased coupled inductor turns-ratio. In this paper, a coupled inductor based high gain inverter is proposed, which achieves higher gain by increasing the coupled inductor turns-ratio (n = n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ) within a very narrow turns-ratio range of 0 ≤ n <; 1, which is a major improvement over the other coupled inductor based high boost impedance source inverters. The proposed inverter, named Improved Trans-Current-Fed Switched Inverter, is described along with its equivalent operating states and relation between its input and output variables are derived. The steady-state inverter waveforms are shown using PSpice simulations. The operation of the inverter is validated by the experimental results, which show strong correlation with the theoretical analysis. A 110-V RMS ac output is obtained from 26-V dc input using a coupled inductor with turns-ratio of 0.33 to demonstrate its high-boost operation.