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Ohmic loss minimization in AC transmission systems with embedded DC grids
KTH, School of Electrical Engineering (EES), Electric Power Systems.
KTH, School of Electrical Engineering (EES), Electric Power Systems.
KTH, School of Electrical Engineering (EES), Electric Power Systems.ORCID iD: 0000-0002-6431-9104
2013 (English)In: 39th Annual Conference of the IEEE Industrial Electronics Society, IECON, IEEE conference proceedings, 2013, 2117-2120 p.Conference paper, Published paper (Refereed)
Abstract [en]

The HVDC systems built based on the voltage source converters (VSC) can bring several benefits to the AC power systems. Better voltage profile, increasing power flow controllability, lower ohmic loss, and higher transfer capability are some major benefits of such systems. This paper investigate the impact of VSC-type DC grids installed in the AC power systems on the ohmic network losses. This is done by formulating a convex optimization problem which minimises the ohmic losses (both in AC and DC grids) subject to the technical constraints of both AC and DC system. The formulated optimisation problem is a conic optimisation problem which can be solved using the commercially available optimisation softwares. The conic AC-DC optimal power flow, CAD-OPF, is coded in GAMS platform and solved using the MOSEK solver. The IEEE 30-bus example system is modeled and studied.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2013. 2117-2120 p.
Series
IEEE Industrial Electronics Society. Annual Conference. Proceedings, ISSN 1553-572X
Keyword [en]
High Voltage DC Grids (HVDC), Ohmic loss, Voltage Source Converter (VSC)
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-143163DOI: 10.1109/IECON.2013.6699458ISI: 000331149502013Scopus ID: 2-s2.0-84893555488ISBN: 978-147990224-8 (print)OAI: oai:DiVA.org:kth-143163DiVA: diva2:705821
Conference
39th Annual Conference of the IEEE Industrial Electronics Society, IECON 2013; Vienna; Austria; 10 November 2013 through 14 November 2013
Note

QC 20140318

Available from: 2014-03-18 Created: 2014-03-17 Last updated: 2015-05-21Bibliographically approved
In thesis
1. On the Efficiency and Accuracy of Simulation Methods for Optimal Power System Operation: Convex Optimization Models for Power System Analysis, Optimal Utilization of VSC-type DC Wind Farm Grids and FACTS Devices
Open this publication in new window or tab >>On the Efficiency and Accuracy of Simulation Methods for Optimal Power System Operation: Convex Optimization Models for Power System Analysis, Optimal Utilization of VSC-type DC Wind Farm Grids and FACTS Devices
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recently, significant changes in electric power systems such as rapid developmentof smart grid and electricity market and integration of non-dispatchablesources have added more complexity to the Power Flow Scheduling (PFS) andPower Balancing (PB) models. For instance, non-dispatchable sources introducean increasing level of uncertainty in the electricity market and power system operation.One of the solutions for handling these uncertainties in the power systemoperation is the improvement of system flexibility through a more efficient operationof power systems. On the other hand, efficient operation can be achieved bywell capturing variable behavior of uncertain sources such as wind power sourceswhich in turn demands efficient and robust PFS/PB models. This way, a moreflexible system, capable of efficiently accommodating higher levels of wind powerchanges, can be achieved. All these factors increase a need for PFS/PB models suchas Power Flow (PF) and Optimal Power Flow (OPF) models which can addressthese new challenges in an efficient, reliable, and economic way while supportingthe power system operation and control. In this regard, various solution methodshave been developed for solving different forms of PF/OPF formulation. The difficultyof solving OPF problems increases significantly with increasing network sizeand complexity. One of these complexities is how to model advanced controllable devices such as HVDC grids and Flexible AC Transmission Systems (FACTS) devices.Accurate handling of these complexities has limited the use of OPF in manyreal-world applications mainly because of its associated computational challenges.The main reasons behind computational challenges are nonlinearity and especiallynon-convexity of constraints representing power system and its components. Inthis regard, OPF problems are classified into two main groups. In the first group,researchers adopt Nonlinear programming (NLP) approach to fully represent thenonlinearity of the power system for the sake of accuracy but with the cost of complexityin the model. Computational and theoretical challenges associated withNLP approaches are then used as a motivation towards developing a more simplifiedOPF model, leading to the second group of OPF models known as LinearProgramming (LP) based OPF models. LP approaches are fast, reliable, and especiallyconvex, and therefore guarantee a global optimum to the simplified OPFproblem. The problem of LP approach to OPF is that the LP solution of OPF may not even be a feasible solution of original nonlinear OPF at all. Another issueassociated with LP models is that complex power system devices such as HVDClinks are difficult to be incorporated. These limitations have restricted the applicationof LP approaches for many OPF problems. According to the mentionedadvantages and disadvantages of NLP and LP based OPF models, what we seeks isan OPF model which can have main advantages of both LP OPF models (Efficientnumerical solvers) and full AC OPF models (Results accuracy). In this thesis, wedevelop convex optimization problems which can be adopted as both PF and OPFmodels which are capable of catching the nonlinear nature of power systems asmuch as possible while can be solved by efficient solution methods such as InteriorPoint Methods (IPMs). These OPF models can incorporate HVDC links, windfarm Multi Terminal HVDC (MTDC) grids, and shunt FACTS devices.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xiv, 97 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2015:022
National Category
Engineering and Technology
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-166383 (URN)978-91-7595-573-5 (ISBN)
Public defence
2015-06-09, H1, Teknikringen 33, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150521

Available from: 2015-05-21 Created: 2015-05-07 Last updated: 2015-05-21Bibliographically approved

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Ghandhari, Mehrdad

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