Parallel-Connected Modular-Type Converter for Online Battery Impedance Measuring and DC-Link Regulation Using AC Current Compensation

The safety and reliability of batteries have become increasingly critical due to the rise in fire accidents. The online measurement of AC resistance in batteries is recognized as an important indicator for detecting potential fault conditions. A DC–DC converter used for battery charging and discharging can enable the dual functionality of power conversion and online AC resistance measurement. However, the injection of AC perturbation required for resistance measurement degrades DC-link voltage regulation and reduces power conversion efficiency. This paper investigates the degradation of DC-link regulation resulting from online AC resistance measurement in battery cells. To address this issue, a parallel-connected DC–DC converter with an AC current compensation algorithm is proposed to improve DC-link stability. The operational principle and control strategy are analyzed to minimize AC current fluctuations during AC resistance measurement. Experimental results using a prototype system validate the effectiveness of the proposed AC current compensation method in enhancing DC-link regulation.