Multi-Objective Mixed-Integer Convex Programming Method for the Siting and Sizing of UPFCs in a Large-Scale AC/DC Transmission System
Weikun Liang, Shunjiang Lin, Jie Liu, Ping Dong, Mingbo Liu
Abstract
To solve the problem of uneven distribution of power flow and limited transfer capability for the transmission section in a large-scale AC/DC transmission system, a multi-objective mixed-integer convex programming method for the siting and sizing of unified power flow controllers (UPFCs) in an AC/DC transmission system is proposed. Considering the four objectives of the annual equivalent investment and operation cost, bus voltage deviation, transfer capability of the transmission section, and renewable energy accommodation, a multi-objective optimization model is established. By using the convex relaxation method, the original mixed-integer nonlinear programming model is transformed into a mixed-integer second-order cone (SOC) programming model to improve the computational efficiency. Furthermore, a successive inscribed polygon method is proposed to tighten the relaxation gap for the SOC constraints in the optimization model and improve the calculation accuracy. In addition, a direct and fast method for solving the compromise optimal solution of the multi-objective optimization model is proposed. Finally, the effectiveness of the proposed method is demonstrated by an actual 8733-bus large-scale AC/DC transmission system and the modified IEEE-39 bus AC/DC system.