Current-Fed High-Conversion-Ratio Bidirectional DC-to-DC Converter with Coupled-Inductors and Switched-Capacitors

Abstract

Due to environmental consideration and increase of load demand renewable energy is widely used nowadays However its unreliable and intermittent characteristics cause problems of power supply reliability To solve the problem an energy storage system (ESS) may be used not only to improve the stability of distribution power system with renewable energy integrated but also relieve the intermittence of renewable energy Therefore used to coordinate power flow between ESS and distribution power system a bidirectional DC-to-DC converter becomes an important research topic A new current-fed high-conversion-ratio bidirectional DC-to-DC converter integrated coupled-inductors and switched-capacitors are proposed for the application in ESS With the current-fed configuration continuous low-ripple input current can be achieved which can avoid the use of input electrolytic capacitor to enhance the reliability of the whole system High-conversion-ratio is obtained by coupled-inductors and switched-capacitors In boost mode switches at high voltage side can achieve soft-switching The efficiency can thus be enhanced due to the reduction of conduction loss In buck mode each of the switches can have soft-switching Leakage energy on secondary side can be recycled by active-clamped circuit Thus the efficiency can be further improved as well Operation principles voltage stress analyses and design guidelines of components used in the proposed circuit are discussed in detail in the thesis Finally a 24V low-side voltage 400V high-side voltage and 200W rated prototype power circuit has been implemented in the thesis to verify its effectiveness According to the experimental results a maximal efficiency 95 5% and 92 3% at rated power are obtained while in boost mode In buck mode a maximal efficiency 93 2% and 87 7% at rated power are observed

Date of Award	2015 Aug 25
Original language	English
Supervisor	Hong-Tzer Yang (Supervisor)