Bi-directional hybrid DC-DC converter with large conversion ratio for microgrid DC busses interface

Abstract

This paper proposes a bi-directional DC-DC converter used as interface between the battery stack and the DC bus in a microgrid application, highlighting its main feature that permits a large conversion rate, with a low number of semiconductors and without using transformers. Analytical descriptions, design aspects, digital simulation and preliminary experimental results are presented, in order to check its operation in both power flow modes, emphasizing the transition between step-up and step-down regimes. It is proved that a simple hysteresis controller is able to assure the stability and a smooth transition between battery charging and discharging modes. The transistors driving signals are complementary which gives the advantage of using a single PWM control.