Bi-Directional Converter System for Light Load by Heterogeneous Combined Type Reactor

Abstract

In this paper, we propose a new type of smoothing reactor using different types of reactors with different magnetic flux saturation to construct a DC-DC converter with low current ripple under the light load of the bidirectional DC-DC converter. Reduction of current ripple at light load in the limited hybrid reactor can greatly reduce the inrush current ripple of DC-Grid at light load, which is a weakness of existing bidirectional DC-DC converters and is considered to contribute to DC-Grid stabilization. Experiments were conducted to prove the feasibility of the proposed system and hybrid reactor.

Current Ripple Reduction Employing the Reactor of DC–DC Converter to Have Variable Inductance through Magnetic Saturation

“…The proposed combination of two reactors has a large inductance at a low current where the magnetic flux does not saturate and a small inductance at a large current where the magnetic flux saturates. Therefore, if this reactor is used for a DC-DC converter in a DCdistribution network, it dramatically reduces current ripple at light loads [49].…”

“…Case 1 is constructed using the same magnetic material. A magnetic circuit is built by arranging the distance between the outer and inner magnetic materials to be larger than the air gap [49]. The outside reactor has a large air gap, and the inside reactor has a small air gap.…”

“…Relationship between magnetic flux, current, and inductance for a reactor with a large air gap, a reactor with a small air gap, and the case of connecting the two reactors in series; (a) ideal and (b) practical [49].…”

“…Case 1: Two Magnetic Circuits in One MMF Circuit. Figure 10 shows the design drawing and prototype photo of the reactor to which the Case 1 concept was applied [49]. Case 1 reactor uses UU core composed of the same magnetic material.…”

“…FIGURE 1: Bidirectional DC-DC converter structure and current ripple according to duty ratio, (a) Converter structure applicable to the DC distribution grids with different voltage levels and (b) current ripple according to the duty ratio[49].…”