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Emerging distribution systems with a proliferation of distributed energy resources are facing with new challenges, such as voltage collapse and power flow congestion in unsymmetrical network configurations. As a fundamental tool that could help quantify these new challenges and further mitigate their impacts on the secure and economic operation of distribution systems, effective AC optimal power flow (ACOPF) models and solution approaches are in urgent need. This study focuses on ACOPF of three‐phase four‐conductor configured distribution systems, in which neutral conductors and ground resistances are modelled explicitly to reflect practical situation. In addition, by leveraging the Kirchhoff's current law (KCL) theorem and the effect of zero injections, voltage variables of neutrals and zero‐injection phases can be effectively eliminated. The ACOPF problem is formulated as a convex semidefinite programming (SDP) relaxation model in complex domain. In recognising possible solution inexactness of SDP relaxation model, a Karush–Kuhn–Tucker condition based process is further proposed to effectively recover feasible solutions to the original ACOPF problem by calculating a set of computational‐inexpensive non‐linear equations. Numerical studies on a modified IEEE 123‐bus system show the effectiveness of the proposed SDP relaxation model with variable reductions and the feasible solution recovery process for three‐phase four‐conductor configured distribution systems.
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Reactive Power Optimization for Flat Voltage Profiles in Distribution Networks
This paper considers achieving flat voltage profiles in a distribution network based on reactive power optimization (RPO) through voltage regulation devices (VRD). These devices include capacitor banks, load-tap-changing and regulating transformers, whose statuses can only assume pre-determined integer value levels, making this a non-convex problem. Two RPO-based algorithms are proposed, which can be applied to any initial states, node priority, topology and load model types. The first algorithm focuses on finding a practical solution by ensuring the VRD constraints are observed at each step. The second one focuses on finding the globally optimal solution by applying a convex relaxation technique and solving the resulting problem with the barrier interior point method. Here, the gradients are computed numerically, thus requiring no analytical functions of voltages in terms of VRDs. Numerical results and their analysis are examined on two test networks: 1) single feeder; and 2) network with laterals.
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- Award ID(s):
- 1710944
- PAR ID:
- 10163319
- Date Published:
- Journal Name:
- 2019 North American Power symposium
- Page Range / eLocation ID:
- 1 to 6
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/NAPS46351.2019.9000354
