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arXiv · 1901.04566

Optimal Power Flow with Step-Voltage Regulators in Multi-Phase Distribution Networks

Mohammadhafez Bazrafshan·Nikolaos Gatsis·Hao Zhu
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Abstract

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.

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Mohammadhafez Bazrafshan, Nikolaos Gatsis, Hao Zhu. 2019-01-14. Optimal Power Flow with Step-Voltage Regulators in Multi-Phase Distribution Networks. https://arxiv.org/abs/1901.04566

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