33 research outputs found
Optimal Power Flow with Step-Voltage Regulators in Multi-Phase Distribution Networks
This paper develops a branch-flow based optimal power flow (OPF) problem for
multi-phase distribution networks that allows for tap selection of wye,
closed-delta, and open-delta step-voltage regulators (SVRs). SVRs are assumed
ideal and their taps are represented by continuous decision variables. To
tackle the non-linearity, the branch-flow semidefinite programming framework of
traditional OPF is expanded to accommodate SVR edges. Three types of
non-convexity are addressed: (a) rank-1 constraints on non-SVR edges, (b)
nonlinear equality constraints on SVR power flows and taps, and (c) trilinear
equalities on SVR voltages and taps. Leveraging a practical phase-separation
assumption on the SVR secondary voltage, novel McCormick relaxations are
provided for (c) and certain rank-1 constraints of (a), while dropping the
rest. A linear relaxation based on conservation of power is used in place of
(b). Numerical simulations on standard distribution test feeders corroborate
the merits of the proposed convex formulation.Comment: This manuscript has been submitted to IEEE Transactions on Power
System
Convex Relaxations and Linear Approximation for Optimal Power Flow in Multiphase Radial Networks
Distribution networks are usually multiphase and radial. To facilitate power
flow computation and optimization, two semidefinite programming (SDP)
relaxations of the optimal power flow problem and a linear approximation of the
power flow are proposed. We prove that the first SDP relaxation is exact if and
only if the second one is exact. Case studies show that the second SDP
relaxation is numerically exact and that the linear approximation obtains
voltages within 0.0016 per unit of their true values for the IEEE 13, 34, 37,
123-bus networks and a real-world 2065-bus network.Comment: 9 pages, 2 figures, 3 tables, accepted by Power System Computational
Conferenc