A Method for Detecting DC Bias in Transformer of Dual Active Bridge DC-DC Converter

A potential concern with the isolation transformer in a dual active bridge DC-DC converter (DAB) unit is the DC bias of magnetization. With the influence of DC bias, the loss of the transformer increases, and the lifespan decreases. However, it is difficult to accurately measure the small DC component mixed in a large (>10A peak), high-frequency AC current, which makes it difficult to eliminate DC bias. A novel sensor is proposed to solve this problem. The proposed sensor is based on the principle of single-core fluxgate and current transformer. Compared with an ordinary Hall effect sensor, the proposed sensor significantly improves the DC current measurement accuracy and sensitivity. This paper presents the working principle and basic structure of the sensor, and the experimental result that measuring the small DC component mixed in a large, high-frequency AC current is also be demonstrated.