Voltage Balancing for Bipolar DC Distribution Grids: A Power Flow based Binary Integer Multi-Objective Optimization Approach

Benjamin Si Hao Chew, Yan Xu*, Qiuwei Wu

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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The re-emergence of 2-phase bipolar DC distribution network, which utilizes the neutral wire for efficient distribution, has spurred research interest in recent years. In practice, system efficiency (power loss) and voltage unbalance are major concerns for the planning and design of the 2-phase DC bipolar network. While most of the existing methodologies are power electronics solutions, there are very few works on resolving the problem from the power system perspective. This paper proposes a model based optimization method by firstly formulating the power flow model for 2-phase DC bipolar network using the single line modeling technique and nodal analysis. Secondly, a binary integer load distribution model is proposed to consider the redistribution of unipolar loads across the two unipolar distribution poles. Together with the power flow model, the system power loss and system voltage unbalance indices are formulated as a binary integer quadratic model. Thirdly, a multi-objective optimization model is formulated and solved using the weighted sum approach. The proposed method is applied to a DC LED lighting system design which considers both voltage unbalance and power loss. Using a 15 bus single source and a 33 bus multi-source network as case studies, the developed power flow model is validated with very high accuracy. Compared to existing iterative methods, the proposed model-based approach is able to
significantly improve the voltage balancing across the distribution system. 
Original languageEnglish
JournalI E E E Transactions on Power Systems
Issue number1
Pages (from-to)28 - 39
Publication statusPublished - 2018


  • 2-phase DC network modeling
  • Binary integer
  • DC bipolar distribution system
  • DC LED lighting system
  • Optimal load distribution
  • Voltage unbalance

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