A Coordinated Voltage Regulation Method for Low-Voltage Bipolar DC Distribution System Based on Modulus Line Drop Compensation

The low-voltage Bi-DCDS is capable of accommodating the steadily increasing penetration of DC sources and loads, comparing with other distribution architectures. However, the three-conductor supply structure suffers voltage unbalance issue between positive and negative ports under load-unbalanced conditions. To address this issue, this paper proposes a coordinated voltage mitigation method for the low-voltage Bi-DCDS based on MLDC. The advantage of MLDC over conventional LDC in voltage regulation, and the key considerations in parameter selection of MLDC are analyzed. According to the analysis, a set of performance indices are developed to evaluate voltage regulation effectiveness, and converter power-sharing balance under multi-terminal operation. Based on the indices, a multi-objective optimization model for MLDC parameters is formulated, and a Pareto optimal solution selection method based on adaptive weighting of objective function values is presented. Case studies demonstrate that the proposed MLDC approach can suppresses load-side voltage unbalance and maintaining converter port voltage imbalance within prescribed limits simultaneously. The proposed optimization framework achieves a balanced trade-off among the considered performance indices.