Interleaved bi-directional Dual Active Bridge DC-DC converter for interfacing ultracapacitor in micro-grid application

Abstract

Ultracapacitor in microgrid requires a high power and galvanic isolated bi-directional converter to interface and control power flow with load. In this paper, an interleaved bi-directional Dual Active Bridge (DAB) DC-DC converter is proposed for interfacing ultracapacitor in microgrid application. By using interleaved scheme in the converter, the input/output ripple frequency is increased by n times and the ripple magnitude is reduced to 1 over n times where the n is the number of the converters in parallel or series. This can significantly reduce the filter size and thus increase the power density. To avoid the inrush current in the start up time, a soft-start scheme is also proposed. Furthermore, a cascaded control loop is implemented to achieve the voltage regulation as well as to balance power distribution among the modules. A 4.8kW interleaved input parallel output series DAB converter is proposed and simulations are carried out to verify the proposed scheme.