Fully distributed planning method for coordinated distribution and urban transportation networks considering three-phase unbalance mitigation

Electric vehicles (EVs) are regarded as one of the silver bullets for addressing the global climate warming issue due to their zero‑carbon emission. However, the proliferation of EVs increases the demand on distribution network (DN), which already face challenges due to three-phase asymmetrical loads and impedance mismatches. The combination of charging demand and traditional three-phase loads aggravated the nodal voltage imbalance within DN. To tackle these issues, this paper presents a coordinated planning model for a three-phase unbalanced distribution network (TUDN) and urban transportation network (UTN). The model optimizes the placement of fast charging stations (FCS), line expansions, and road enhancements, using a distribution network reconfiguration (DNR) strategy to improve charging traffic flow (CTF) and reduce voltage imbalances. To ensure privacy encryption, a fully distributed framework using the alternating direction method of multipliers (ADMM) is designed to solve this problem, where a two-layer iterative process (TIP) is further developed to improve the convergence of ADMM, taking into account the integer variables in the model. Numerical simulations on a modified IEEE 34-bus system and a real-world system in China demonstrate the model’ s effectiveness, achieving a 43.84 % reduction in maximum voltage imbalance and outperforming other algorithms in iteration count and computation time. •The temporal-space relationship between EV traffic flow and TCL are characterized in the proposed planning model.•DNR and charging flow optimization are coordinated and optimized to manage voltage imbalances effectively.•A distributed framework utilizing an improved ADMM algorithm is developed to solve the proposed planning problem.•The effectiveness of the proposed model and distributed framework is validated using real-world networks in China.