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Modelling of multi-terminal HVDC systems in optimal power flow formulation
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
2012 (English)In: 2012 IEEE Electrical Power and Energy Conference, EPEC 2012, IEEE , 2012, 170-175 p.Conference paper, Published paper (Refereed)
Abstract [en]

The multi-terminal HVDC systems and their embedded DC networks are considered as smart grids technology which improve economic efficiency of the power system. This technology allows better voltage profile in the power system by better allocation of the generation sources. Also, it can help in improving the economic efficiency of the system by substituting the high-cost generation with low-cost generation. In order to assess the technical benefit of this smart grids technology, this paper presents an optimal power flow formulation for AC grids with embedded DC networks built from multi-terminal HVDC systems. The objective function of this AC-DC OPF formulation is the total active dispatch costs. The constraints consist of (a) AC grid constraints, (b) constraints from multi-terminal HVDC systems, and (c) DC grid constraints. The formulated AC-DC OPF is a mixed-integer nonlinear optimisation problem. The formulation is coded in GAMS platform and tested on IEEE 30 Bus system.

Place, publisher, year, edition, pages
IEEE , 2012. 170-175 p.
Keyword [en]
Economic Efficiency, Multi-terminal HVDC systems, Optimal Power Flow
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-121221DOI: 10.1109/EPEC.2012.6474944ISI: 000317098400029Scopus ID: 2-s2.0-84875621012ISBN: 978-146732080-1 (print)OAI: oai:DiVA.org:kth-121221DiVA: diva2:617687
Conference
2012 IEEE Electrical Power and Energy Conference, EPEC 2012; London, ON; Canada; 10 October 2012 through 12 October 2012
Note

QC 20130424

Available from: 2013-04-24 Created: 2013-04-24 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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