Distributed Optimal Voltage Control and Berth Allocation of All-Electric Ships in Seaport Microgrids

Abstract

The uncoordinated berth allocation of all-electric ships (AES) will impose great challenges on voltage profiles in seaport microgrids. This paper proposes a distributed optimal voltage control and berth allocation strategy to mitigate voltage violations while balancing the benefits between microgrids and AES. The voltage control problem is formulated as a second-order cone program (SOCP) to minimize network power loss, while the berth allocation problem is formulated as a mixed-integer linear program (MILP) to minimize total service time. To build the bridge between microgrids and berthed-in AES, the power interaction model at the seaport is proposed. The proposed model introduces a time-cost factor to evaluate the economic cost of service time and also unifies the timescales between voltage control and berth allocation. Considering different system operators and objectives of microgrids and AES, this paper develops an alternating direction of multipliers (ADMM)-based distributed optimization algorithm to solve the problem. The method can help reach the convergence of ADMM in solving models with discrete variables. The proposed approach is tested on the EU 16-bus microgrid embedded with a seaport and simulation results verify the effectiveness both in mitigating voltage violations and maximizing the total benefits of microgrids and AES.