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  • 1.
    Baradar, Mohamadreza
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Modeling of Multi Terminal HVDC Systemsin Power Flow and Optimal Power Flow Formulations2013Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Nowadays, due to lack of a strong interconnection between electric power systems within EU, there is a concern about the restricted power exchange. On the other hand, one of the factors which results in necessity of improving the level of power exchange is development of renewable energy sources such as offshore wind farms.

    Multi-terminal HVDC (MTDC) systems are supposed to be one of the cost-effective ways to aggregate a huge amount of renewable energies on one side and on the other side connect it to the main AC system through a common DC network.

    Possibility of such connections has led to the proposition of a meshed DC grid which connects several renewable energy sources and large AC systems.

    In order to fully take advantages of such AC-DC systems in the realsize power systems, extensive research has to be carried out to reveal their steady state and dynamic behavior. This thesis addresses different steady state aspects of such hybrid AC-DC systems.

    In the first part of thesis, we develop a multi-option power flow approach for hybrid AC-DC grids. The main contribution of this approach is that only one additional state variable is added to the AC and DC variables for each slack converter to handle the slack converter losses. Doing so, all AC, DC and converter equations are solved simultaneously. This makes the power flow algorithm much simpler than the sequential approaches where one external iterative loop is assigned to compute the converter losses. Such a high number of iterative loops in the sequential approaches makes the algorithm not only complicated and time consuming, but also unreliable.

    In the second part of thesis, given the nonconvex nature of Power Flow Optimisation (OPF) problem, a convex OPF formulation for AC grids with embedded DC networks based on the new Line Flow Based (LFB) variablesand in the form of Second Order Cone Programming (SOCP) is developed. SOCPs are a general form of linear programming accompanied by nonlinear constraints in the form of convex cones which can be efficiently solved through Interior Point methods (IPMs).

     

  • 2.
    Baradar, Mohamadreza
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    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 Devices2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 3.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Afsharnia, Saeed
    University of Tehran.
    Sanaye-Pasand, Majid
    University of Tehran.
    A Fast Method for Fault Section Identification in Series Compensated Transmission Lines2010Ingår i: 2010 9th International Conference on Environment and Electrical Engineering (EEEIC), IEEE, 2010, s. 483-486Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a novel and fast method for fault section identification in compensated series transmission lines based on the high frequency traveling wave has been proposed. The method uses the relation of magnitude and polarity between wavefronts of high frequency travelling waves induced by fault. For accurately and fast extracting polarity and magnitude of travelling wave, wavelet transform and modulus maxima are used. Validation of this method is carried out by PSCAD/EMTP and MATLAB simulations for typical 400 kV power system faults. Simulation results reveal high performance of the method.

  • 4.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Ghandhari, Mehrdad
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    A Multi-Option Unified Power Flow Approach for Hybrid AC/DC Grids Incorporating Multi-Terminal VSC-HVDC2013Ingår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 28, nr 3, s. 2376-2383Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper proposes a multi-option power flow approach for hybrid AC/DC grids. A unified AC-DC unit is introduced which can be used in two different cases: case a) AC grids with embedded VSC-based MTDC grids, and case b) asynchronous AC grids connected via a common VSC-based MTDC grid. In the proposed method for each MTDC grid (regardless of the number of converters), a new state variable is introduced to handle any kind of converter loss models. For the case (b), the AC-DC unit can be used in two different analyses, namely, a1) the separated analysis and a2) the integrated analysis. Both a1) and a2) can be used in the practical analysis of the real-size power systems. However, it is shown that the separated analysis not only offers a shorter computational time but it is also very suitable for the future connection between large existing AC systems and other AC systems or remote renewable energy sources through the DC grids. The proposed methodology is implemented in MATLAB software and verified using commercial software SIMPOW.

  • 5.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Ghandhari, Mehrdad
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Van Hertem, Dirk
    Electrical engineering.
    The Modeling Multi-Terminal VSC-HVDC in Power Flow Calculation Using Unified Methodology2011Ingår i: Innovative Smart Grid Technologies (ISGT) Conference, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, a new unified method for power flowcalculation in AC grids with embedded multi-terminal HVDCsystems based on voltage source converter is proposed. In thismethod all DC and AC equations are solved simultaneously inthe same iteration while there is no need to rely on resultsobtained from other iterative loops unlike the other methods.The method can be applied for any number of converters,any DC network configuration and any converter loss model.The algorithm is implemented in MATLAB and to validate theresults, they are compared to results obtained from the simulationsoftware SIMPOW.

  • 6.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Ghandhari, Mehrdad
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Van Hertem, Dirk
    Electrical engineering, Katholieke Universiteit Leuven, Heverlee, Belgium.
    Kargarian, Amin
    Electrical and Computer Engineering, Mississippi State University.
    Power flow calculation of hybrid AC/DC power systems2012Ingår i: Power and Energy Society General Meeting, 2012 IEEE, IEEE , 2012, s. 6343958-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Multi-terminal HVDC systems have recently become an attractive option for interconnection of isolated AC systems such as offshore wind farms and oil platforms to asynchronous large AC systems. This paper deals with power flow calculation (PFC) of hybrid AC/DC power systems where several asynchronous AC systems are interconnected via a common multiterminal VSC-HVDC system. This paper proposes a unified AC-DC approach for PFC of a hybrid AC/DC power system. The proposed approach is then employed for two different analyses, namely a) the separated analysis where the entire hybrid AC/DC system is divided into two groups. The first group (named external AC system) comprises all asynchronous AC systems which are not directly connected to the slack convertor of the DC network, and the second group comprises an AC/DC system where the selected AC system is directly connected to the slack convertor. In this method, a PFC is firstly performed for the the first group, and its relevant obtained results will be used for PFC of the second group. b) the integrated analysis where the entire hybrid system is considered as a unit. Both a) and b) can be used in the practical analysis of the real-size power systems. However, due to practical issues and computational costs the separated analysis may be a more acceptable method. The simulations have been performed using MATLAB, and the obtained results have been compared with those obtained in SIMPOW.

  • 7.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Hesamzadeh, Mohammad
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Ghandhari, Mehrdad
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Ohmic loss minimization in AC transmission systems with embedded DC grids2013Ingår i: 39th Annual Conference of the IEEE Industrial Electronics Society, IECON, IEEE conference proceedings, 2013, s. 2117-2120Konferensbidrag (Refereegranskat)
    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.

  • 8.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Hesamzadeh, Mohammad R.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    A Stochastic SOCP Optimal Power Flow With Wind Power Uncertainty2014Ingår i: 2014 IEEE PES General Meeting | Conference & Exposition, IEEE Computer Society, 2014, s. 6939790-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recent research shows that non-convex AC OPF problem can be recast as a convex Semidefinite (SD) problem or Second Order Cone Programming (SOCP) problem. This paper presents a stochastic SOCP OPF (SSOCP-OPF) model for power systems connected to the wind farms. This is performed by reformulating the original non-convex OPF problem using more practical parameters of the power system. Finally, we obtain a convex optimization problem through some wellknown approximations and an exact relaxation incorporating the stochastic nature of wind power. One of the advantage of convex SOCP problems, which are a general form of linear problems, is that they can be efficiently solved through Interior PointMethods (IPMs). The proposed OPF model takes advantage of both DC-OPF models (solution efficiency) and full AC-OPF models (solution accuracy). As an application of SSOCP-OPF model, we study the impact of wind power uncertainty on the transmission loss in the power systems. To evaluate the proposed stochastic model modified IEEE 30-bus test system is used. The optimization problem is coded in GAMS platform and solved using its embedded interior point optimizer MOSEK.

  • 9.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Hesamzadeh, Mohammad R.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Calculating Negative LMPs from SOCP-OPF2014Ingår i: ENERGYCON 2014 - IEEE International Energy Conference, IEEE Computer Society, 2014, s. 1461-1466Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recent research shows that non-convex OPF problem can be recast as a convex Semidefinite Programming (SDP) problem or Second Order Cone Programming (SOCP) problem. However, in the most SOCP OPF problems, there are some cases that conic relaxation results in a miscalculation of negative Local Marginal Prices (LMPs). This paper reviews the SOCP formulation of the optimal power flow problem proposed in [1] and then proposes one way of generating negative Locational Marginal Prices, LMPs, using this SOCP formulation. The proposed model is coded in GAMS and its built MOSEK solver and tested on a modified version of IEEE-30 test system.

  • 10.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Hesamzadeh, Mohammad R.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Transmission Loss Minimisation in Power Systems with Embedded Smart-Grid Technologies2013Ingår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679Artikel i tidskrift (Övrigt vetenskapligt)
  • 11.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Hesamzadeh, Mohammad R.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Ghandhari, Mehrdad
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Second-order cone programming for optimal power flow in VSC-type AC-DC grids2013Ingår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 28, nr 4, s. 4282-4291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a second order cone programming (SOCP) formulation of the optimal power flow problem for AC-DC systems with voltage source converter (VSC) technology. Approximation techniques have been used to derive the SOCP formulation of the AC-DC OPF problem. Later, the SOCP formulation can be solved using the interior point method (IPM) by considering the limits on AC-DC grid. The accuracy of SOCP formulation of AC OPF has been proven with numerical examples using IEEE 14-bus, IEEE 30-bus, and IEEE 57-bus example systems. The results of the SOCP formulation are compared with available commercial software. Then a DC system with VSC technology is modeled in the IEEE 30-bus example system. The SOCP formulation of AC-DC OPF is applied to the modified IEEE 30-bus example system and the results are discussed. The limitations of derived SOCP formulation are also discussed.

  • 12.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Hesamzadeh, Mohammad Reza
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    AC Power Flow Representation in Conic Format2015Ingår i: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 30, nr 1, s. 546-547Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This letter presents a second-order cone formulation for AC power flow problem. The power flow equations are first derived as functions of more practical variables of power systems and then placed in a second-order cone programming (SOCP) problem. The proposed conic power flow (CPF) model can be solved efficiently through IPMs, and at the same time, it has a very good accuracy as compared to the full AC power flow model. Also, the proposed CPF can efficiently handle the ill-conditioned networks. The numerical efficiency and good accuracy of the model are shown by simulating various case studies.

  • 13.
    Baradar, Mohamadreza
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Hesamzadeh, Mohammad Reza
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Ghandhari, Mehrdad
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Modelling of multi-terminal HVDC systems in optimal power flow formulation2012Ingår i: 2012 IEEE Electrical Power and Energy Conference, EPEC 2012, IEEE , 2012, s. 170-175Konferensbidrag (Refereegranskat)
    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.

  • 14. Kargarian, A.
    et al.
    Falahati, B.
    Fu, Y.
    Baradar, Mohamadreza
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Multiobjective optimal power flow algorithm to enhance multi-microgrids performance incorporating IPFC2012Ingår i: Power and Energy Society General Meeting, 2012 IEEE, IEEE , 2012, s. 6345605-Konferensbidrag (Refereegranskat)
    Abstract [en]

    The idea of connecting some adjacent microgrids and making a multi-microgrid (MMG) have recently attracted attention among power system researchers. It helps better operate, control and manage the power system. This paper presents a multiobjective optimal power flow (MOPF) algorithm for improving the performance of MMGs incorporating interline power flow controller (IPFC). The proposed MOPF simultaneously minimizes MMG operating cost and total energy loss, as well as voltage profile deviation of all buses in the system. The proposed multiobjective nonlinear constraint optimization problem is formulated considering the control variables of IPFC. Also, the proposed algorithm guarantees that the final system operating point has a suitable security margin from the voltage instability point. A typical MMG system is used to demonstrate the effectiveness and proficiency of the algorithm.

  • 15.
    Nazari, Mohammad
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Baradar, Mohamadreza
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Hesamzadeh, Mohammad Reza
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    Ghandhari, Mehrdad
    KTH, Skolan för elektro- och systemteknik (EES), Elektriska energisystem.
    On-line control of multi-terminal HVDC systems connected to offshore wind farms using the POF-based multi-agent approarch2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Multi-terminal HVDC systems are an attractive option to connect offshore wind farms to onshore grids. Although scheduling the multi-terminal HVDC system is based on forecasted wind power, the forecasted values may differ from their real time ones. This paper presents a new controller based on multi-agent system which optimally tries to follow the variations of real time wind power outputs. Since a fast optimal power flow algorithm is needed, a convexified AC-OPF model which can be efficiently solved through interior point methods (IPMs) is embedded into the proposed online controller. Simulations are carried out and validated using GAMS platform and MATLAB/Simulink.

  • 16.
    Siavashi, Ehsan M
    et al.
    University of Western Ontario.
    Baradar, Mohamadreza R
    Facualty of Electrical and Computer Engineering , University of Tehran, Tehran, Iran.
    Afsharnia, Saeed
    University of Tehran.
    Tavakoli Bina, M
    Novel method for fault section identification2009Ingår i: 2009 2nd International Conference on Power Electronics and Intelligent Transportation System (PEITS), 2009, s. 179-184Konferensbidrag (Refereegranskat)
    Abstract [en]

    From stability point of view fault section identification is an important task for a transmission systems. In this paper, a novel method for section identification using extended Kalman filter (EKF) has been proposed. Subsynchronous frequency as indicator of fault section identification is estimated by EKF algorithm. Several tests as different fault locations have been performed to show performance of the method. Simulation results reveal high performance of the method. In all tests, the proposed algorithm detects accurately presence of subsynchronous frequency.

1 - 16 av 16
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