Extendable Bidirectional DC–DC Converter With Improved Voltage Transfer Ratio and Reduced Switch Count

Abstract

Bidirectional dc-dc converter (BDC) plays an important role in battery-based applications. This paper 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> MOSFETs, 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">$\widehat{\boldsymbol{v}}_{\boldsymbol H}/\widehat{\boldsymbol d}_{\boldsymbol H}$</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">$\widehat{\boldsymbol{v}}_{\boldsymbol L}/\widehat{\boldsymbol d}_{\boldsymbol L}$</tex-math></inline-formula> for both the 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 (XSG), 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 MOSFETs is significantly improved compared to the other converters which achieve the quadratic VTR. Each extended stage requires a single MOSFET along with 4 passive components.