Optimum Operation of Low-Voltage AC/DC Distribution Areas with Embedded DC Interconnections under Three-Phase Unbalanced Compensation Conditions

This paper presents an optimal operation method for embedded DC interconnections based on low-voltage AC/DC distribution areas (EDC-LVDA) under three-phase unbalanced compensation conditions. It can optimally determine the transmission power of the DC and AC paths to simultaneously improve voltage quality and reduce losses. First, considering the embedded interconnected, unbalanced power structure of the distribution area, a power flow calculation method for EDC-LVDA that accounts for three-phase unbalanced compensation is introduced. This method accurately describes the power flow distribution characteristics under both AC and DC power allocation scenarios. Second, an optimization scheduling model for EDC-LVDA under three-phase unbalanced conditions is developed, incorporating network losses, voltage quality, DC link losses, and unbalance levels. The proposed model employs an improved particle swarm optimization (IPSO) two-layer algorithm to autonomously select different power allocation coefficients for the DC link and AC section under various operating conditions. This enables embedded economic optimization scheduling while maintaining compensation for unbalanced conditions. Finally, a case study based on the IEEE 13-node system for EDC-LVDA is conducted and tested. The results show that the proposed optimal operation method achieves a 100% voltage compliance rate and reduces network losses by 13.8%, while ensuring three-phase power balance compensation. This provides a practical solution for the modernization and upgrading of low-voltage power grids.