Extendable Bidirectional DC–DC Converter With Improved Voltage Transfer Ratio and Reduced Switch Count
V. Seshagiri Rao, S. Tapaswi, S. Kumaravel
Abstract
Bidirectional dc–dc converter (BDC) plays an important role in battery-based applications. This article presents an extendable BDC using 8+5 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> components, including 3+ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, where <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> is the number of stages. The detailed analysis of single stage of the proposed converter is discussed. The voltage transfer ratio (VTR) of the converter during the step-up and step-down modes is derived. The effect of parasitic elements on the VTR and the efficiency is discussed. The state-space model is derived, and the open-loop transfer functions, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\hat{\bm{v}}}}_{\bm{H}}/{{\hat{\bm{d}}}}_{\bm{H}}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\bm{\ }}\ {{\hat{\bm{v}}}}_{\bm{L}}/{{\hat{\bm{d}}}}_{\bm{L}}$</tex-math></inline-formula> for both modes are obtained. These transfer functions are validated using circuit-level simulation. The operating modes of the converter are validated using a 300 W, 650 V, and 50 kHz prototype, and the experimental results are presented. Using the derived transfer functions, the PI controllers are designed using Ziegler–Nichols method for step-up and step-down modes. Using the Xilinx system generator, the designed controllers are implemented, and the experimental closed-loop results are presented. The performance comparison shows that the VTR of the single-stage converter using four <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s is significantly improved compared to the other converters which achieve the quadratic VTR. Each extended stage requires a single <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> along with four passive components.