三相多有源桥变换器的占空比控制

The interconnection of multiple dc grids is experiencing a growing demand for the integration of renewable power supplies. For this purpose, multi-port converters are an excellent option due to their inherent modularity, while minimizing the amount of hardware required to couple multiple dc grids. However, the control of such converters is challenging, especially when the modulation strategy should apply to any number of ports and be based on analytical equations to allow fast computation. Among the multi-port converters, the multi-active bridge is particularly interesting as it features soft-switching capability and galvanic isolation while coupling multiple dc grids with a single transformer stage, thus reducing losses and the number of components. However, under conventional single-phase-shift (SPS) operation, the multi-active bridge suffers from hard-switching at partial load, which causes an increase in electromagnetic emissions and switching losses. To address this issue, this article derives a partial-load modulation scheme from model-based analytical equations. The proposed duty-cycle control introduces an additional degree of freedom, which allows for an extension of the soft-switching area and a reduction in rms currents. Measurements on a modular hardware prototype validate the effectiveness of the proposed method.