Tri-Level Robust Investment Planning of DERs in Distribution Networks With AC Constraints

Integration of distributed energy resources (DERs) has salient technical benefits such as improving power system resiliency, reducing transmission network losses, and regulating voltage in distribution networks. In addition to technical benefits, DERs bring remarkable economic profits for their investor. Accordingly, a comprehensive and accurate planning study is urgently needed by an investor who is to build DERs in a distribution network. In this paper, a tri-level investment planning model is proposed to maximize the net present value (NPV) of DERs in distribution networks. Robust optimization is utilized to cope with physical and financial data uncertainty in load demand, DERs output, and energy selling price. An effective decomposition strategy called column and constraint generation (C&CG) method is adapted to link the first and second levels of the proposed optimization problem. An iterative AC optimal power flow (AC-OPF) is presented to model the distribution grid circuit equations. The developed AC-OPF is solved in the third level through a modified Newton's method lied within a Benders decomposition framework. The proposed model is formulated as mixed-integer linear programming (MILP) problem and its effectiveness is illustrated by the IEEE 33-bus distribution test system.