Composite generation and transmission expansion planning with second order conic relaxation of AC power flow

Because of the non-convex AC power flow, power system expansion planning used traditionally DC power flow which approximates to AC power flow. This paper proposed a novel method for power system expansion planning with AC power flow. In order to mathematically optimize AC power flow, a second order conic relaxation method of branch AC power flow equations has been proposed. A second order programming for optimal power flow is formulated and is compared with local optimization method (e.g. interior point method). Then, by adding the integer decision variables, composite generation and transmission expansion planning has been formulated for mixed integer second order conic programming (MICP), which can be solved by mature optimization software. Expansion planning the paper proposed has considered voltage limit and network loss. Finally, standard numerical cases have been studied to illustrate the effectiveness of conic relaxation of AC power flow and we have compared power system expansion planning with conic relaxation of AC power flow to that of DC power flow.