Overview of Voltage Balancing Schemes in Bipolar DC Microgrids

Driven by the ongoing development of the energy Internet and the evolution of power systems, bipolar dc microgrids (BDCMGs) have gained attention for their flexibility, reliability, and strong adaptability. However, factors including load imbalance, asymmetrical renewable energy generation, and inconsistencies in transmission line parameters lead to bus voltage imbalance, which can result in severe power quality degradation and operational issues in BDCMGs. This article compares three structures of bipolar dc distribution and quantitatively analyzes the impact of load imbalance on voltage imbalance. Solutions to the voltage imbalance issue in BDCMGs are comprehensively summarized from the perspectives of voltage balancing converters, multi-input integrated converters, coordinated control of distributed power sources, intelligent loads, and automatic commutation switches. Finally, five voltage-balancing schemes are compared and analyzed, with an evaluation of voltage balancing converters and multi-input integrated converters in terms of passive components count, semiconductors count, switching voltage stress, and voltage gain.