Power Flow Optimization of Bipolar DC Distribution Network Considering Voltage Unbalance

The True Bipolar DC (TBDC) distribution network has the capability to supply two voltage levels. Because of high power supply reliability, large transmission capacity and easy access to distributed power supply and DC load, it has become a research focus in recent years. Firstly, the fundamental components and topological structure of the TBDC distribution network are analyzed to optimize power flow, minimize line loss, and reduce the imbalance between positive and negative pole voltages. Then, a power flow optimization model is proposed by modifying the droop coefficient of each DC/DC converter, adjusting the energy storage output, and controlling the load power. The model can absorb the distributed photovoltaic, adjust the voltage of each node to the allowable range, reduce the voltage imbalance between positive and negative poles, as well as decrease the overall line loss of the DC distribution network. Finally, A 5-node and a modified IEEE 69-node TBDC distribution network are built to validate the effectiveness and applicability of the optimization model proposed. The ultra-short term optimal dispatching simulation of the modified IEEE 14 node network is carried out to verify the superiority and energy-saving effect.