Asymmetrical Bidirectional DC–DC Converter With Limited Reverse Power Rating in Smart Transformer

The increasing penetration of distributed generators in low-voltage distribution grids may lead to distribution transformers, also a smart transformer, experiencing the reverse power flow, which is less as compared to the forward power flow in the current electric grid. This article proposes an asymmetrical bidirectional dc-dc (AB-DC/DC) converter, which has two partial-scale rectifiers of an active bridge and a diode bridge connected in parallel at the secondary side, with less cost of power semiconductors and the capability of bidirectional operation to satisfy the realistic condition. The proposed AB-DC/DC converter works as a single active bridge under forward power flow condition, while it works as a dual active bridge under reverse power flow condition. The solutions to share the active power under forward operation and suppress the circulating power under reverse operation are proposed, respectively. The simulation and experimental results both clearly validate the effectiveness and feasibility of the proposed AB-DC/DC converter.