In this paper, an improved hybrid current modulation (iHCM) method for bidirectional power flow operation of dual active bridge (DAB) ac/dc converter is proposed. In this method, trapezoidal (TZM) and triangular (TRM) current modulations are performed together in a grid period to obtain distortionless grid current with forming minimum RMS current in the transformer of DAB. This study put forward a detailed analysis of the mode changing instants (between TRM and TZM), RMS and peak current values of the transformer and required magnetic core sizes. Furthermore, the iHCM is compared in analysis and simulations by the variable switching frequency dual phase shift modulation (VSF DPSM) method that have small RMS current advantage in the vicinity of nominal output power. According to the analysis, the iHCM, unlike the VSF DPSM, can operate over a wide range of transformer turn ratio (or over the wide range of ac peak voltage/reflected dc voltage, λ) without increasing the size of transformer, and can provide small RMS currents at light loads as it has no nonactive (circulating) current. The theoretical analysis is validated with a downsized 250 W experimental prototype.

本文提出了一种改进的混合电流调制（iHCM）方法，用于双有源桥（ACB / ACB）双向交流电的双向潮流运行。在这种方法中，梯形（TZM）和三角形（TRM）电流调制在电网周期内一起执行，以在DAB变压器中形成最小RMS电流的情况下获得无失真的电网电流。这项研究对变压器的模式转换瞬间（TRM和TZM之间），RMS和峰值电流值以及所需的磁芯尺寸进行了详细分析。此外，在分析和仿真中通过可变开关频率双相移调制（VSF DPSM）方法对iHCM进行了比较，该方法在标称输出功率附近具有较小的RMS电流优势。根据分析，iHCM与VSF DPSM不同，λ）而不会增加变压器的尺寸，并且由于它没有无效（循环）电流，因此可以在轻负载下提供较小的RMS电流。理论分析已通过缩小的250 W实验原型进行了验证。