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  • 1.
    Abbas, Khizra
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Autonomous Gate Drivers Tailored for Triangular Current Mode-Based Zero-Voltage Switching Two-Level Three-Phase Inverters for Electric Vehicle Drive Systems2024In: Energies, E-ISSN 1996-1073, Vol. 17, no 5, article id 1060Article in journal (Refereed)
    Abstract [en]

    The demand for highly efficient and dynamic electric vehicles (EVs) has increased dramatically. The traction inverter, a pivotal component in an EV powertrain, plays a crucial role. This study is dedicated to designing a traction inverter with focus on achieving high efficiency and elevated power density and mitigating electromagnetic interference (EMI) issues. To realize these objectives, autonomous gate drivers (AGDs) are proposed and designed using LTspice simulation software. The aim is to achieve zero voltage switching (ZVS) at both turn-on and turn-off through the utilization of triangular current mode (TCM) control on the gate driver. The AGDs implement a current modulation scheme by sensing the current and voltage and generating gate-source voltage signals with minimal delays. The implemented current modulation scheme by the AGDs results in an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only contribute to extending the motor lifespan by mitigating sharp-edge voltages but also bring advantages such as reduced switch stress, decreased EMI, and simplified thermal management.

  • 2.
    Abbas, Khizra
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Kostov, Konstantin
    RISE Research Institutes of Sweden, Department Smart Hardware, Stockholm, Sweden.
    Comprehensive Insight into the Operational Dynamics of TCM-Based Zero-Voltage Switching (ZVS) Two-Level Three-Phase Inverters for Electric Vehicle (EV) Motor-Drive Applications2024In: 2024 IEEE Texas Power and Energy Conference, TPEC 2024, Institute of Electrical and Electronics Engineers (IEEE) , 2024Conference paper (Refereed)
    Abstract [en]

    This paper introduces a novel triangular-current mode (TCM), zero-voltage switching (ZVS) two-level three-phase inverter, specifically designed to enhance the performance of the electric vehicle (EV) drive system. The primary objective is to enhance the inverter efficiency by minimizing turn-on and turn-off switching losses while mitigating electromagnetic interference (EMI) by generating sinusoidal output waveforms. The distinctive feature of this inverter lies in its gate driver, which executes the current modulation scheme. Achieving ZVS during turn-on involves the gate driver sensing the switch voltage and turning it on at zero voltage, utilizing TCM. For turn-off ZVS, the gate driver monitors the switch current, turning it off when it exceeds a predefined reference value. With a carefully placed snubber capacitor, turn-off ZVS is achieved. The implemented current modulation scheme yields an efficiency exceeding 99% for a 10 kW power rating. The sinusoidal output waveforms not only enhance motor lifespan by safeguarding against sharp-edge voltages but also offer benefits like reduced switch stress and simplified thermal management.

  • 3. Abdelhakim, A.
    et al.
    Blaabjerg, F.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Single-Stage Boost Modular Multilevel Converter (BMMC) for Energy Storage Interface2020In: 2020 22nd European Conference on Power Electronics and Applications, EPE 2020 ECCE Europe, Institute of Electrical and Electronics Engineers (IEEE) , 2020, article id 9215788Conference paper (Refereed)
    Abstract [en]

    Single-stage DC-AC power converters are gaining higher attention due to their simpler structure compared to the two-stage equivalent solution. In this paper, a single-stage DC-AC converter solution is proposed for interfacing a low voltage (LV) DC source with a higher voltage AC load or grid, where this converter has a modular structure with multilevel operation. The proposed converter, which is called boost modular multilevel converter (BMMC), comprises the boosting capability within the inversion operation, and it is mainly dedicated for interfacing LV energy storage systems, such as fuel cells and batteries, and it allows the use of LV MOSFETs (« 300 V), in order to utilize their low ON-state resistance, along with LV electrolytic capacitors. This converter is introduced and analysed in this paper, where simulation results using PLECS, considering a 10 kW three-phase BMMC, are presented in order to verify its functionality.

  • 4.
    Abedi, Amin
    et al.
    UNIGE, Inst Environm Sci, Geneva, Switzerland.;UNIGE, Comp Sci Dept, Geneva, Switzerland..
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Romerio, Franco
    UNIGE, Inst Environm Sci, Geneva, Switzerland.;UNIGE, Geneva Sch Econ & Management, Geneva, Switzerland..
    Adaptive robust vulnerability analysis of power systems under uncertainty: A multilevel OPF-based optimization approach2022In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 134, article id 107432Article in journal (Refereed)
    Abstract [en]

    With the growing level of uncertainties in today's power systems, the vulnerability analysis of a power system with uncertain parameters becomes a must. This paper proposes a two-stage adaptive robust optimization (ARO) model for the vulnerability analysis of power systems. The main goal is to immunize the solutions against all possible realizations of the modeled uncertainty. In doing so, the uncertainties are defined by some predetermined intervals defined around the expected values of uncertain parameters. In our model, there are a set of first-stage decisions made before the uncertainty is revealed (attacker decision) and a set of second-stage decisions made after the realization of uncertainties (defender decision). This setup is formulated as a mixedinteger trilevel nonlinear program (MITNLP). Then, we recast the proposed trilevel program to a single-level mixed-integer linear program (MILP), applying the strong duality theorem (SDT) and appropriate linearization approaches. The efficient off-the-shelf solvers can guarantee the global optimum of our final MILP model. We also prove a lemma which makes our model much easier to solve. The results carried out on the IEEE RTS and modified Iran's power system show the performance of our model to assess the power system vulnerability under uncertainty.

  • 5.
    Abedi, Amin
    et al.
    Institute for Environmental Sciences, University of Geneva, Switzerland.
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Romerio, Franco
    Institute for Environmental Sciences, University of Geneva, Switzerland.
    An ACOPF-based bilevel optimization approach for vulnerability assessment of a power system2021In: International Journal of Electrical Power & Energy Systems, ISSN 0142-0615, E-ISSN 1879-3517, Vol. 125, article id 106455Article in journal (Refereed)
    Abstract [en]

    This paper examines the effects of reactive power dispatch, losses, and voltage profile on the results of the interdiction model to analyze the vulnerability of the power system. First, an attacker-defender Stackelberg game is introduced. The introduced game is modeled as a bilevel optimization problem where the attacker is modeled in the upper level and the defender is modeled in the lower level. The AC optimal power flow (ACOPF) is proposed as the defender's tool in the lower-level problem to mitigate the attack consequences. Our proposed ACOPF-based mathematical framework is inherently a mixed-integer bilevel nonlinear program (MIBNLP) that is NP-hard and computationally challenging. This paper linearizes and then transforms it into a one-level mixed-integer linear program (MILP) using the duality theory and some proposed linearization techniques. The proposed MILP model can be solved to the global optimum using state-of-the-art solvers such as Cplex. Numerical results on two IEEE systems and Iran's 400-kV transmission network demonstrate the performance of the proposed MILP for vulnerability assessment. We have also compared our MILP model with the DCOPF-based approach proposed in the relevant literature. The comparative results show that the reported damage measured in terms of load shedding for the DCOPF-based approach is always lower than or equal to that for the ACOPF-based approach and these models report a different set of critical lines, especially in more stressed and larger power systems. Also, the effectiveness and feasibility of the proposed MILP model for power-system vulnerability analysis are discussed and highlighted. 

  • 6.
    Abolpour, Roozbeh
    et al.
    Shiraz Univ, Sch Elect & Comp Engn, Shiraz, Iran..
    Dehghani, Maryam
    Shiraz Univ, Sch Elect & Comp Engn, Shiraz, Iran..
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Inside-Ellipsoid Outside-Sphere (IEOS) model for general bilinear feasibility problems: Feasibility analysis and solution algorithm2023In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 147, p. 110738-, article id 110738Article in journal (Refereed)
    Abstract [en]

    This paper deals with general bilinear feasibility problems. A nonlinear transformation is introduced that reformulates a general bilinear feasibility problem as a Linear Matrix Inequality (LMI) problem augmented with a single non-convex quadratic constraint. The single non-convex quadratic constraint has a regular concave constraint function. Due to the LMI part of this formulation, it is easier to analyze, and we prove that the solution space of this formulation is located inside several ellipsoids and outside a sphere. This leads to our proposed Inside-Ellipsoid and Outside-Sphere (IEOS) model for general bilinear feasibility problems. Then, the feasibility analysis of our proposed IEOS model is performed. The related necessary feasibility conditions and sufficient feasibility conditions are theoretically developed. Moreover, an iterative algorithm for solving our IEOS model is also proposed.Two applications including matrix-factorization problem in control systems and power-flow prob-lem in power systems are considered to evaluate the practicality of our proposed approach. Both problems are formulated as IEOS models. It is shown that our proposed model can provide more accurate solutions to these problems as compared to previous competing approaches in the relevant literature.

  • 7.
    Abolpour, Roozbeh
    et al.
    Shiraz Univ, Sch Elect & Comp Engn, Shiraz 7134851154, Iran..
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Dehghani, Maryam
    Shiraz Univ, Sch Elect & Comp Engn, Shiraz 7134851154, Iran..
    A New Power Flow Model With a Single Nonconvex Quadratic Constraint: The LMI Approach2022In: IEEE Transactions on Power Systems, ISSN 0885-8950, E-ISSN 1558-0679, Vol. 37, no 2, p. 1218-1229Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose a new mathematical model for power flow problem based on the linear and nonlinear matrix inequality theory. We start with rectangular model of power flow (PF) problem and then reformulate it as a Bilinear Matrix Inequality (BMI) model. A Theorem is proved which is able to convert this BMI model to a Linear Matrix Inequality (LMI) model along with One Nonconvex Quadratic Constraint (ONQC). Our proposed LMI-ONQC model for PF problem has only one single nonconvex quadratic constraint irrespective of the network size, while in the rectangular and BMI models the number of nonconvex constraints grows as the network size grows. This interesting property leads to reduced complexity level in our LMI-ONQC model which in turn makes it easier to solve for finding a PF solution. The non-conservativeness, iterative LMI solvability, well-defined and easy-to-understand geometry and pathwise connectivity of feasibility region are other important properties of proposed LMI-ONQC model which are discussed in this paper. An illustrative two-bus example is carefully studied to show different properties of our LMI-ONQC model. We have also tested our LMI-ONQC model on 30 different power-system cases including four ill-conditioned systems and compared it with a group of existing approaches. The numerical results show the promising performance of our LMI-ONQC model and its solution algorithm to find a PF solution.

  • 8.
    Abolpour, Roozbeh
    et al.
    Shiraz Univ, Sch Elect & Comp Engn, Shiraz, Iran..
    Javanmardi, Hamidreza
    Shiraz Univ, Sch Elect & Comp Engn, Shiraz, Iran..
    Dehghani, Maryam
    Shiraz Univ, Sch Elect & Comp Engn, Shiraz, Iran..
    Hesamzadeh, Mohammad Reza
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Optimal frequency regulation in an uncertain islanded microgrid: A modified direct search algorithm2022In: IET Renewable Power Generation, ISSN 1752-1416, E-ISSN 1752-1424, Vol. 16, no 4, p. 726-739Article in journal (Refereed)
    Abstract [en]

    This paper presents a methodology for frequency regulation in a microgrid involving renewable energy sources (RES) using a dynamic controller, which is an output feedback controller (OFC). The parameters of OFC are tuned by searching the design space of the controller. Since the RES model is not exactly known, the uncertain model is derived and the OFC is considered for it. The goal of controller tuning is to find appropriate parameters of the controller such that the norm of frequency deviations, even in presence of uncertainties in the RES parameters is minimized. An algorithm based on searching the controller design space is suggested to find the suitable controller gains. The algorithm assumes the controller parameters lie in a convex space and searches the space systematically such that an appropriate solution is found. The method is proved mathematically and two theorems are mentioned, accordingly. Finally, a simulated model of a RES is utilized for algorithm evaluation and the results demonstrate the algorithm capability in optimal frequency regulation.

  • 9.
    Acquaviva, Alessandro
    et al.
    Chalmers Univ Technol, Div Elect Power Engn, S-41296 Gothenburg, Sweden..
    Wallmark, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Grunditz, Emma Arfa
    Chalmers Univ Technol, Div Elect Power Engn, S-41296 Gothenburg, Sweden..
    Lundmark, Sonja Tidblad
    Chalmers Univ Technol, Div Elect Power Engn, S-41296 Gothenburg, Sweden..
    Thiringer, Torbjorn
    Chalmers Univ Technol, Div Elect Power Engn, S-41296 Gothenburg, Sweden..
    Computationally Efficient Modeling of Electrical Machines With Cooling Jacket2019In: IEEE TRANSACTIONS ON TRANSPORTATION ELECTRIFICATION, ISSN 2332-7782, Vol. 5, no 3, p. 618-629Article in journal (Refereed)
    Abstract [en]

    Modeling of electrical machines is a multiphysics problem. Depending on the phenomena of interest and the computational time constraint, this can be done at different levels of detail. In this article, the main approaches to model the thermal behavior of electrical machines with a liquid cooled casing around the stator (often referred to as cooling jacket) are analyzed and a novel approach is presented. The proposed method aims at creating computationally efficient 3-D multiphysics models of electrical machines with liquid cooled jacket. This model is based on the assumption of a fully developed flow in the cooling jacket which allows to scale the computational fluid dynamics (CFD) simulation to 1-D. The slot with a two layer concentrated winding and potting material is modeled using a composite material comprising of both the conductors and slot filler. Similarly, a unified material is used to model the end-windings. Experimental results on a traction machine for vehicle applications are presented showing good agreement with the simulations. Also, a comparison with a 3-D CFD is presented to verify the pressure drop in the pipe bend. Finally, the model is used to simulate a dynamic load cycle, which would be computationally extremely demanding with combined 3-D CFD and thermal FEA of the machine and its cooling.

  • 10.
    Agredano Torres, Manuel
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Xu, Qianwen
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Zhang, Mengfan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Cornell, Ann M.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering, Applied Electrochemistry.
    Dynamic power allocation control for frequency regulation using hybrid electrolyzer systems2023In: 2023 IEEE Applied Power Electronics Conference And Exposition, APEC, Institute of Electrical and Electronics Engineers (IEEE) , 2023, p. 2991-2998Conference paper (Refereed)
    Abstract [en]

    The increase in hydrogen production to support the energy transition in different sectors, such as the steel industry, leads to the utilization of large scale electrolyzers. These electrolyzers have the ability to become a fundamental tool for grid stability providing grid services, especially frequency regulation, for power grids with a high share of renewable energy sources. Alkaline electrolyzers (AELs) have low cost and long lifetime, but their slow dynamics make them unsuitable for fast frequency regulation, especially in case of contingencies. Proton Exchange Membrane electrolyzers (PEMELs) have fast dynamic response to provide grid services, but they have higher costs. This paper proposes a dynamic power allocation control strategy for hybrid electrolyzer systems to provide frequency regulation with reduced cost, making use of advantages of AELs and PEMELs. Simulations and experiments are conducted to verify the proposed control strategy.

  • 11. Aguilera, M.
    et al.
    Vanfretti, L.
    Gómez, Francisco José
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Experiences in power system multi-domain modeling and simulation with modelica & FMI: The case of gas power turbines and power systems2018In: 2018 Workshop on Modeling and Simulation of Cyber-Physical Energy Systems, MSCPES 2018 - Held as part of CPS Week, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 1-6, article id 8405397Conference paper (Refereed)
    Abstract [en]

    The turbine-governor models that are currently used in studies of power systems include over-simplifications of turbomachinery elements. Due to the growing need to support intermittent energy resources with other energy sources like gas turbines, more detailed models including an explicit representation of the physical dynamics are attractive. In this paper, the advantages of the Modelica language and the FMI standard are considered to carry out modeling and multi-domain simulation of gas turbines with power grids, which can be used to evaluate scenarios of power variability. The work gathers preliminary results of the potential that FMUs offer to promote the exchange of turbine models by manufacturers and to conduct multi-domain simulations in several tools.

  • 12.
    Ahlfors, Charlotta
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Weekly planning of hydropower in systems with large volumes of varying power generation2022Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Hydropower is the world’s largest source of renewable electricity generation. Hydropower plants with reservoirs provide flexibility to the power systems. Efficient planning techniques improve the flexibility of the power systems and reduce carbon emissions, which is needed in power systems experiencing a rapid change in balance between power production and consumption. This is due to increasing amount of renewable energy sources, such as wind and solar power. Hydropower plants have low operating costs and are used as base power. This thesis focuses on weekly planning of hydropower in systems with large volumes and varying power generation and a literature review and a maintenance scheduling method are presented.

    The topic of hydropower planning is well investigated and various research questions have been studied under many years in different countries. Some of the works are summarized and discussed in literature reviews, which are presented in this thesis. First, some reviews are presented, which covers several aspects of hydropower planning. Literature reviews for long term, mid term and short term planning, respectively, are described.

    Maintenance scheduling in power systems consists of preventive and corrective maintenance. Preventive maintenance is performed at predetermined intervals according to a prescribed criteria. This type of maintenance is important for power producers to avoid loss in electricity production and loss in income. The maintenance scheduling for hydropower plants prevent these phenomena since spill in the reservoirs and wear on the turbines can be avoided. Usually, the maintenance in hydropower plants is performed on the turbines or at the reservoir intake. A deterministic and a stochastic method to solve a mid term maintenance scheduling problem formulated as a Mixed Integer Linear Programming using dynamic programming is presented. The deterministic method works well in terms of computational time and accuracy. The stochastic method compared to the deterministic method yields a slightly better result at the cost of a need for larger computational resources.

    Download full text (pdf)
    fulltext
  • 13.
    Ahlfors, Charlotta
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Amelin, Mikael
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Weekly planning of hydropower in systems with large volumes and varying power generation: A literature review2021In: 2021 IEEE Madrid PowerTech, PowerTech 2021 - Conference Proceedings, Institute of Electrical and Electronics Engineers (IEEE) , 2021, article id 9495058Conference paper (Refereed)
    Abstract [en]

    Hydropower is the world's largest source of renewable electricity generation and hydropower plants with reservoirs provide flexibility to the power systems. Efficient planning techniques improve the flexibility of the power systems and reduce carbon emissions, which is needed in power systems exposed to a rapid change. Renewable energy sources, such as wind and solar power, are increasing in the power systems. Hydropower plants have low operating costs and are used as base power. This paper reviews hydropower planning in different time frames and specifically focuses on weekly planning, i.e. hydropower planning for 1 to 3 weeks. Main conclusions in this study are that the term weekly planning is seldom used and the definitions in earlier studies of short term, mid term and long term planning, respectively, varies. The authors propose that weekly planning should belong to mid term planning.

  • 14.
    Ali, Muhammad Taha
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems. KTH Royal Institute of Technology.
    Analysis of Sub-Synchronous Oscillations in Wind Power Plants2020Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The modern power system is moving towards the high integration of renewable energy sources at a fast pace. The integration of wind power in the power system raises many challenges along with the benefits. One of the recent challenges is the sub-synchronous oscillation (SSO) that occurs in doubly-fed induction generator (DFIG) based wind farms. This oscillation is caused by sub-synchronous control interaction (SSCI). The SSCI condition occurs when the DFIG-based wind farm is radially connected to a series compensated transmission line. The aim of this thesis is to investigate and study the circumstances and causes of SSCI, and to develop the techniques that could mitigate this condition from the system. A mathematical model of DFIG-based power system is designed and an eigenvalue analysis is performed. The eigenvalue analysis shows that out of many factors, the level of series compensation play major role in inflicting SSCI in the system. The eigenvalue sensitivity analysis is performed on all the controller parameters of DFIG converters. It is shown that the proportional parameter of the rotor-side converter (RSC) is the most sensitive parameters and the stability of the system is highly dependent on its value. Moreover, the participation factors of the system are also computed to understand the phenomenon better. SSCI is also explained through the internal impedance of induction generator, as seen from the stator terminal. It is shown that the presence of RSC controller enables the occurrence of SSCI, by increasing the negative resistance of the rotor, and its proportional parameters adds up to the negative resistance.

    Two mitigation techniques are presented in this thesis. In the first technique a power oscillation damper (POD) is designed and tuned. The proper placement of a tuned POD in the DFIG converter can eliminate the SSCI from the system using a local signal. In the second technique, the boomerang effect of the most sensitive control parameter is presented and it is proposed that the proper selection of control parameters can eliminate the risk of SSCI from the system, even for higher series compensation levels. Along with linearized and non-linear simulations, the sensitivity analysis and the mitigation of SSCI through proper selection of control parameters is validated experimentally using an actual 7.5 kW DFIG system. The analysis of SSCI is also carried out in a multi-machine two-area system and the mitigation techniques are successfully implemented. The influence of synchronous generator on SSCI is also studied, and the mitigation of SSCI using PSS in the synchronous generator is presented. It is shown that by implementing all the mitigation techniques simultaneously, the multi-machine systems can be made immune to SSCI for any realistic level of series compensation.

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    Analysis of Sub-Synchronous Oscillations in Wind Power Plants
  • 15.
    Ali, Muhammad Taha
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Ghandhari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Harnefors, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Optimal tuning and placement of POD for SSCI mitigation in DFIG-based power system2019In: 2019 IEEE Milan PowerTech, PowerTech 2019, Institute of Electrical and Electronics Engineers (IEEE), 2019, article id 8810891Conference paper (Refereed)
    Abstract [en]

    The phenomenon of sub-synchronous control interaction (SSCI) in doubly-fed induction generators (DFIGs) is investigated and the optimal tuning and placement of a power oscillation damper (POD) for its mitigation is proposed in this paper. The effect of the POD on the DFIG system is studied by placing it at all the summation junctions of rotor-side converter (RSC) and grid-side converter (GSC) controllers, turn by turn. Five local signals are examined as different input signals to the POD out of which three local signals gave promising results. These signals include the DFIG's active power, the magnitude of the DFIG's apparent power, and the magnitude of the current through the transmission line. Residues are calculated for each POD placement and for each input to the POD. The calculated residues are studied along with the root-locus plots to see the effect of the POD on the mitigation of SSCI and the stability of the DFIG-based system.

  • 16.
    Ali, Muhammad Taha
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Zhou, Dao
    Song, Yipeng
    Ghandari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Harnefors, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Blaabjerg, Frede
    Analysis and Mitigation of SSCI in DFIG Systems With Experimental Validation2020In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 35, no 2, p. 714-723Article in journal (Refereed)
    Abstract [en]

    Sub-synchronous oscillations (SSOs) in doubly-fed induction generator (DFIG)-based series compensated power systems are mainly caused by sub-synchronous control interaction (SSCI). SSCI is the most recently found type of sub-synchronous resonances. In this article, SSCI is elaborated and investigated by performing eigenvalue analysis on a mathematically modeled DFIG system. The occurrence of SSCI is observed and the results of eigenvalue analysis are validated through a down-scaled 7.5-kW experimental setup of a grid-connected DFIG. Based on the analysis, the proportional control parameters of the rotor-side converter (RSC) are found to be very sensitive towards the sub-synchronous modes of the system. The results obtained from both the simulation and the experimental analysis show that if the sensitive proportional parameters of the RSC are tuned properly, then the DFIG system can become immune to the SSCI for any level of series compensation.

  • 17.
    Alikhani, Parnian
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Bertling, Lina
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Astner, Linda
    Port Gävle, Gävle, Sweden..
    Donnerstal, Pontus
    Port Gävle, Gävle, Sweden..
    Forecasting the Electrical Demand at the Port of Gavle Container Terminal2021In: 2021 IEEE PES INNOVATIVE SMART GRID TECHNOLOGY EUROPE (ISGT EUROPE 2021), Institute of Electrical and Electronics Engineers (IEEE) , 2021, p. 806-811Conference paper (Refereed)
    Abstract [en]

    The port industry is transforming into a smart port thanks to technological advancements and environmental expectations. Developing a sustainable maritime transportation system and its beneficial electrification as a proven approach in emissions reduction are gathering momentum due to technological growth. Global containerization leads to high electricity demand at container terminals, and the electricity demand is highly dynamic and dependent on different operation processes. The approach of this paper is to forecast the hourly peak load demand and short-term electricity demand profile in a container terminal. The correctly forecasted electricity demand profile is crucial for less expensive and reliable power operation and planning. First, Artificial Neural Network (ANN) method is used to predict the container terminal baseload demand. Second, worst-case simultaneous peak load is estimated. Third, the day-ahead load profile is modeled based on the handling operation scheduled for the day. The approach is implemented at the container terminal in Port of Gavle, and the results, including the baseload forecasting, the peak power demand, and the hourly load profile modeling by 2030, have been used in dialogue with the local energy company for the future predicted need of load.

  • 18.
    Alikhani, Parnian
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Bertling, Lina
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Astner, Linda
    Gävle Hamn AB.
    Donnerstål, Pontus
    Gävle Hamn AB.
    Forecasting the Electrical Demand at the Port of Gävle Container Terminal2021Conference paper (Refereed)
    Abstract [en]

    The port industry is transforming into a smart port thanks to technological advancements and environmental expectations. Developing a sustainable maritime transportation system and its beneficial electrification as a proven approach in emissions reduction are gathering momentum due to technological growth. Global containerization leads to high electricity demand at container terminals, and the electricity demand is highly dynamic and dependent on different operation processes. The approach of this paper is to forecast the hourly peak load demand and short-term electricity demand profile in a container terminal. The correctly forecasted electricity demand profile is crucial for less expensive and reliable power operation and planning. First, Artificial Neural Network (ANN)method is used to predict the container terminal baseload demand. Second, the worst-case simultaneous peak load is estimated. Third, the day-ahead load profile is modeled based on the handling operation scheduled for the day. The approach is implemented at the container terminal in Port of Gävle, and the results, including the baseload forecasting, the peak power demand, and the hourly load profile modeling by 2030, have been used in dialogue with the local energy company for the future predicted need of load.

  • 19.
    Alikhani, Parnian
    et al.
    Institute of Engineering, University Grenoble Alpes, Grenoble, France.
    Mrad, Abeer
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Louie, Henry
    Seattle University.
    Bertling, Lina
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    On the Reliability and Life Cycle Cost Analyses of Small-scale Standalone Solar Systems in Rural Areas2021In: 2021 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT), Institute of Electrical and Electronics Engineers (IEEE), 2021, p. 5-Conference paper (Refereed)
    Abstract [en]

    In this paper, a three-step optimization approach is presented in order to obtain the optimal sizing of Standalone Photovoltaic (SPV) system. The main aim is to weigh the cost against the reliability of the system to make a smart design decision. The optimization approach has two objective functions to be minimized, Annual Lost Load (ALL) and Annual Life Cycle Cost (ALCC). The proposed method includes battery lifetime estimation, which is based on the active Depth of Discharge (DOD) of micro-cycles on the battery operation. The method has been applied to a remote area in Zambia. The results indicate that the introduced framework is capable of optimizing the system while satisfying the operational and economical requirements.

  • 20.
    Alkeaid, Majed Mohammed G
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems. KTH, School of Industrial Engineering and Management (ITM).
    Study of NEOM city renewable energy mix and balance problem2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It is important for NEOM management in the contemporary world to put in place NEOM projects using the available resources. The region in which the NEOM project is spacious and vast with conditions suited to generate energy from solar and wind. The NEOM projectis expected to be set up in the very resourceful state of Saudi Arabia. The purpose of the study is to assist in setting up a sustainable city through the exploitation of solar and wind energy. The aim of the study was to assist in the generation of more than 10 GW renewable energy to replace approximately 80,000 barrels of fossil energy. The problem of coming up with renewable and sustainable energy from the unexploited sources is addressed. The renewable city is expected to be a technological hub based on Green Energy with 100% renewable energy, which is correspond to 72:4GW. Freiburg and Masdar as renewable cities are used as case studies in the research. NEOM power generation capacity is capable to cover Saudi Arabia power generation capacity (approximately 71GW), which is more than enough for a city. The study reveals that the total power generation from wind farms, tidal farms, solar stations, and solar power tower stations are 9:1373GW, 4:76GW, 57:398GW and 1:11GW respectively. Saudi Arabia has plans to set up 16 nuclear plants (17 GW each) for energy purposes (total of 272 GW), which will be part of Saudi Arabia national grid and will be more than enough to cover NEOM electricity demand in case NEOM does not reach demand capacity. In case NEOM energy does not meet the demand, electricity generation from 16 Nuclearpower plants generating 17GW each, and 6 Natural underground batteries with a capacity of 120MW each are recommended. The study results can be applied in NEOM Institute of Science and Technology for further research on renewable energy. The findings can also be used for research extension of HVDC transmission lines between NEOM and Saudi Arabia main grid, Egypt, and Jordan.

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  • 21.
    Almas, Muhammad Shoaib
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Vanfretti, Luigi
    Rensselaer Polytech Inst, Elect Comp & Syst Engn, Rensselaer, NY USA..
    Singh, Ravi Shankar
    Tech Univ Eindhoven, Dept Elect Engn, Eindhoven, Netherlands..
    Jonsdottir, Gudrun Margret
    Univ Coll Dublin, Sch Elect & Elect Engn, Dublin, Ireland..
    Vulnerability of Synchrophasor-based WAMPAC Applications' to Time Synchronization Spoofing2018In: 2018 IEEE POWER & ENERGY SOCIETY GENERAL MEETING (PESGM), IEEE , 2018Conference paper (Refereed)
  • 22.
    Almulla, Youssef
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis.
    Ramirez Gomez, Camilo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Pegios, Konstantinos
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Korkovelos, Alexandros
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy Systems Analysis. World Bank, 1818 H St NW, Washington, DC 20433 USA..
    Strasser, Lucia de
    United Nations Econ Commiss Europe UNECE, Bur S411, CH-1211 Geneva 10, Switzerland..
    Lipponen, Annukka
    United Nations Econ Commiss Europe UNECE, Bur S411, CH-1211 Geneva 10, Switzerland..
    Howells, Mark
    Loughborough Univ, Sch Social Sci & Humanities, Dept Geog, Epinal Way, Loughborough LE11 3TU, Leics, England.;Imperial Coll London, Fac Nat Sci, Ctr Environm Policy, 16-18 Princes Gardens, London SW7 1NE, England..
    A GIS-Based Approach to Inform Agriculture-Water-Energy Nexus Planning in the North Western Sahara Aquifer System (NWSAS)2020In: Sustainability, E-ISSN 2071-1050, Vol. 12, no 17, article id 7043Article in journal (Refereed)
    Abstract [en]

    The North Western Sahara Aquifer System (NWSAS) is a vital groundwater source in a notably water-scarce region. However, impetuous agricultural expansion and poor resource management (e.g., over-irrigation, inefficient techniques) over the past decades have raised a number of challenges. In this exploratory study, we introduce an open access GIS-based model to help answer selected timely questions related to the agriculture, water and energy nexus in the region. First, the model uses spatial and tabular data to identify the location and extent of irrigated cropland. Then, it employs spatially explicit climatic datasets and mathematical formulation to estimate water and electricity requirements for groundwater irrigation in all identified locations. Finally, it evaluates selected supply options to meet the electricity demand and suggests the least-cost configuration in each location. Results indicate that full irrigation in the basin requires similar to 3.25 billion million m(3)per year. This translates to similar to 730 GWh of electricity. Fossil fuels do provide the least-cost electricity supply option due to lower capital and subsidized operating costs. Hence, to improve the competitiveness of renewable technologies (RT) (i.e., solar), a support scheme to drop the capital cost of RTs is critically needed. Finally, moving towards drip irrigation can lead to similar to 47% of water abstraction savings in the NWSAS area.

  • 23.
    Andersson, Kjell
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Hagnestål, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    A Flexible Chain Proposal for Winch-Based Point Absorbers2019In: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001, Vol. 141, no 10, article id 102301Article in journal (Refereed)
    Abstract [en]

    Ocean wave power is a promising renewable energy source. It has, however, been difficult to find a cost-effective solution to convert wave energy into electricity. The harsh marine environment and the fact that wave power is delivered with large forces at low speed make design of durable mechanical structures and efficient energy conversion challenging. The dimensioning forces strongly depend on the wave power concept, the wave energy converter (WEC) implementation, and the actual power take-off (PTO) system. A WEC with a winch as a power take-off system, i.e., a winch-based point absorber (WBPA), could potentially enable a low levelized cost of energy (LCOE) if a low-cost, durable and efficient winch that can deal with peak loads can be developed. A key challenge for realizing such a winch is to find a force transmitting solution that can deal with these peak loads and that can handle up to 80 million cycles during its life. In this article, we propose a design solution for a force transmitting chain with elastomer bearings connecting the links of the chain. With this solution no sliding is present, and the angular motion is realized as elastic shear deformations in the elastomer bearings when the chain is wound onto the winch drum. The elastomer bearings were designed for low shear stiffness and high compression stiffness, and the links were designed primarily to minimize the number of joints in the chain. Thereby, the maximum allowed relative angle between the links when rolled up over the drum should be as large as possible within practical limits. Finite element-based topological optimization was performed with the aim to increase the link strength to weight ratio. A test rig for a first proof of concept testing has been developed, and preliminary test results indicate that this chain concept with elastomer bearings can be a potential solution for a durable chain and should be analyzed and tested further for fatigue and sea operations.

  • 24.
    Andersson, Kjell
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Hagnestål, Anders
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Sellgren, Ulf
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.).
    Design of a flexible chain for winch based point absorbers2018In: Proceedings of NordDesign: Design in the Era of Digitalization, NordDesign 2018, 2018Conference paper (Refereed)
  • 25.
    Antonello, Riccardo
    et al.
    University of Padova.
    Peretti, Luca
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Tinazzi, Fabio
    University of Padova.
    Zigliotto, Mauro
    University of Padova, Italy.
    Self-commissioning calculation of dynamic models for synchronous machines with magnetic saturation using flux as state variable2019In: The Journal of Engineering, E-ISSN 2051-3305, no 17, p. 3609-3613Article in journal (Refereed)
    Abstract [en]

    This paper deals with the non-linear modelling of synchronous machines by using the flux linkage as a state variable.The model is inferred from a conventional set of measurements where the relation between the currents and the flux linkages inthe rotating reference frame (also known as dq reference frame) are known by measurements or estimated through finite-element simulations. In particular, the contribution of this paper is twofold: first, it proposes a method to extract the non-linearmodel information which can be easily implemented in electric drives, without the need of offline post-processing of the data.Second, it mathematically demonstrates that the method converges to the final result in a stable way. An example based onexperimental measurements of the current-to-flux look-up tables of an 11-kW synchronous reluctance machine is shown,proving the feasibility of the proposed method.

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  • 26.
    Arevalo-Soler, Josep
    et al.
    UPC, CITCEA, Ave Diagonal 647, Barcelona, Spain..
    Nahalparvari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Prieto-Araujo, Eduardo
    UPC, CITCEA, Ave Diagonal 647, Barcelona, Spain..
    Gomis-Bellmunt, Oriol
    UPC, CITCEA, Ave Diagonal 647, Barcelona, Spain..
    Norrga, Staffan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Dynamic Converter Control Role Configuration in Grid of Grids2023In: 2023 25TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS, EPE'23 ECCE EUROPE, IEEE, 2023, article id 2024-03-19Conference paper (Refereed)
    Abstract [en]

    The control role of power converters conforming an HVDC link is generally static, i.e. changing the control role of the power converters is not considered in the power system operation. In this paper a lab-scaled demonstration on the control role reconfiguration while an AC/DC/AC link is in operation is presented.

  • 27.
    Arévalo-Soler, Josep
    et al.
    CITCEA-UPC, Barcelona, Spain.
    Nahalparvari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Prieto-Araujo, Eduardo
    CITCEA-UPC, Barcelona, Spain.
    Gomis-Bellmunt, Oriol
    CITCEA-UPC, Barcelona, Spain.
    Norrga, Staffan
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Dynamic Converter Control Role Configuration in Grid of Grids2023In: 2023 25th European Conference on Power Electronics and Applications, EPE 2023 ECCE Europe, Institute of Electrical and Electronics Engineers (IEEE) , 2023Conference paper (Refereed)
    Abstract [en]

    The control role of power converters conforming an HVDC link is generally static, i.e. changing the control role of the power converters is not considered in the power system operation. In this paper a lab-scaled demonstration on the control role reconfiguration while an AC/DC/AC link is in operation is presented.

  • 28.
    Asoodar, Mohsen
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Ciftci, Baris
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Mohanaveeramani, Aravind
    Hitachi-ABB Power Grids, Västeras, 72212, Sweden.
    Nahalparvari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    A Measurement-Based Method for Characterizing Parasitic Inductances in Power Electronic Circuits2021In: 2021 23rd European Conference on Power Electronics and Applications, EPE 2021 ECCE Europe, 2021Conference paper (Refereed)
    Abstract [en]

    This paper presents a new method of measuring parasitic inductances in various elements of power electronic circuits. The proposed solution features a low-cost design while providing accurate measurement results in a predefined range of stray inductances. The solution utilizes a unique parallel resonance circuit for extracting stray inductances in various circuits. Structural challenges as well as the analysis for the choice of circuit parameters are addressed in this study. Both simulation and experimental results are presented to exhibit the efficacy of the solution. Moreover, important design constraints that can affect the end results are explained and considered in the proposed experimental setup.

  • 29.
    Asoodar, Mohsen
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nahalparvari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Bakas, Panagiotis
    Hitachi Energy, Västerås, Sweden..
    Hasler, Jean-Philippe
    Hitachi Energy, Västerås, Sweden..
    Meng, Lexuan
    Hitachi Energy, Västerås, Sweden..
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    A Computationally Efficient Model for Large-Scale Energy Storage Systems With Active Voltage Balancing in Modular Multilevel Converters2023In: 2023 IEEE Applied Power Electronics Conference And Exposition, APEC, Institute of Electrical and Electronics Engineers (IEEE) , 2023, p. 2973-2978Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel method for modeling and simulation of large-scale energy storage systems (ESS) is provided. Specifically, the model is developed for large-scale series connected supercapacitors (SCs) intended for power electronic applications. This method is especially useful for high voltage applications where a large number of series connected energy storage units (ESUs) are required. The proposed solution reduces a multi-node string of series connected SCs-together with their corresponding voltage balancing circuit-to a single unit with two electrical nodes. The proposed model is connected to the dc link of a three phase grid-connected modular multilevel converter (MMC). In this system, the effectiveness of the proposed model and the proposed voltage balancing scheme is demonstrated for a string comprising ten thousand series connected ESUs. The efficacy of the proposed model and the balancing algorithm is proven by simulations in the MATLAB/Simulink environment.

  • 30.
    Asoodar, Mohsen
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nahalparvari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Danielsson, C.
    Hitachi Energy, Mäster Ahls gata 16, Vasterås, 72212, Sweden.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    A Condition Monitoring Scheme for Semiconductor Devices in Modular Multilevel Converters with Cascaded H-Bridge Submodules2022In: 24th European Conference on Power Electronics and Applications, EPE 2022 ECCE Europe, Institute of Electrical and Electronics Engineers Inc. , 2022Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel online semiconductor device monitoring scheme is presented. The condition monitoring (CM) scheme is based on measuring the ON-state voltage drop of semiconductor devices, and tracking the changes in their ON-state resistance. The proposed solution measures the ON-state voltage of semiconductor devices at a controlled and readily measurable temperature. This allows for accurate CM of semiconductors as it decouples temperature related and degradation related changes in the ON-state voltage. The temperature decoupling is achieved using natural switching redundancies available to modular multilevel converter systems. Hence, the proposed CM scheme does not interfere with the output voltages and currents generated by the converter. 

  • 31.
    Asoodar, Mohsen
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems. KTH Royal Inst Technol, Sch Elect Engn & Comp Sci, Stockholm, Sweden..
    Nahalparvari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Danielsson, Christer
    Hitachi Energy, Master Ahls Gata 16, S-72212 Västerås, Sweden..
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    A Condition Monitoring Scheme for Semiconductor Devices in Modular Multilevel ConvertersWith Cascaded H-Bridge Submodules2022In: 2022 24Th European Conference On Power Electronics And Applications (EPE'22 ECCE EUROPE), IEEE , 2022Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel online semiconductor device monitoring scheme is presented. The condition monitoring (CM) scheme is based on measuring the ON-state voltage drop of semiconductor devices, and tracking the changes in their ON-state resistance. The proposed solution measures the ON-state voltage of semiconductor devices at a controlled and readily measurable temperature. This allows for accurate CM of semiconductors as it decouples temperature related and degradation related changes in the ONstate voltage. The temperature decoupling is achieved using natural switching redundancies available to modular multilevel converter systems. Hence, the proposed CM scheme does not interfere with the output voltages and currents generated by the converter.

  • 32.
    Asoodar, Mohsen
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nahalparvari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Danielsson, Christer
    Hitachi ABB Power Grids, Master Ahls Gata 16, S-72212 Vasteras, Sweden.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Temperature Considerations for Online Health Monitoring of DC-Link Capacitors in Modular Multilevel Converters2021In: 2021 23rd European Conference on Power Electronics and Applications, EPE 2021 ECCE Europe, Institute of Electrical and Electronics Engineers Inc. , 2021Conference paper (Refereed)
    Abstract [en]

    In this paper, the effect of temperature on online heath monitoring of dc capacitors in modular multilevel converters (MMCs) is studied. The submodule capacitance value is considered as the main indicator of health. Both self heating and ambient temperature are considered as sources of temperature variation. The study is conducted on a single phase MMC with full-bridge submodules. However, a similar analysis can be used for half-bridge MMCs and multiphase MMCs as well. The thermal behaviour of the capacitors is explained analytically and simulated using a simplified Cauer model. The effect of temperature on the estimated capacitance values is shown, and a method for reducing this effect is proposed. The results are verified using simulations in MATLAB/Simulink.

  • 33.
    Asoodar, Mohsen
    et al.
    Hitachi ABB Power Grids, S-72212 Västerås, Sweden..
    Nahalparvari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Danielsson, Christer
    Hitachi ABB Power Grids, S-72212 Västerås, Sweden..
    Söderström, Rasmus
    Hitachi ABB Power Grids, FACTS Unit, S-72212 Västerås, Sweden..
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Online Health Monitoring of DC-Link Capacitors in Modular Multilevel Converters for FACTS and HVDC Applications2021In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 36, no 12, p. 13489-13503Article in journal (Refereed)
    Abstract [en]

    This article presents an online health monitoring scheme for dc capacitors in modular multilevel converters (MMCs). The health monitoring algorithm is based on detecting changes in the dc capacitance value over time. The proposed algorithm only utilizes measurements that are typically available in flexible alternating current transmission systems and high-voltage direct current applications. Hence, in the proposed estimation method, no additional sensors are used. The estimation scheme considers the presence of noise in voltage and current measurements, and utilizes a recursive least square estimator in conjunction with a special low-pass filter to minimize the estimation errors. Simulation results of a hardware replica, as well as experimental results on a low-power MMC prototype show that the proposed scheme can identify the dc-link capacitance value with a maximum error of 1%.

  • 34.
    Asoodar, Mohsen
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nahalparvari, Mehrdad
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Zhang, Yi
    Aalborg Univ, DK-9220 Aalborg, Denmark..
    Danielsson, Christer
    Hitachi Energy, Västerås, Sweden..
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Blaabjerg, Frede
    Aalborg Univ, DK-9220 Aalborg, Denmark..
    Accurate Condition Monitoring of Semiconductor Devices in Cascaded H-Bridge Modular Multilevel Converters2023In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 38, no 3, p. 3870-3884Article in journal (Refereed)
    Abstract [en]

    This article presents an online condition monitoring (CM) scheme for semiconductors used in modular multilevel converters (MMCs) that comprise cascaded H-bridge submodules. The CM algorithm is based on detecting changes in the ON-state resistance of the semiconductors over time. The proposed method is shown to successfully perform a curve tracing of semiconductors in MMCs while the semiconductor junction remains at a temperature that is readily measurable and undergoes minute changes during the measurement process. The ON-state resistance value is estimated from the measured ON-state voltage drop of the semiconductors and the measured arm current. Measuring the ON-state resistance at known temperatures allows for separating temperature-dependent variations of the ON-state resistance from age-dependent variations of this parameter. Suitable methods for reducing the effect of noise on the curve-traced data are proposed, and a recursive least square estimator is used to extract the optimum ON-state resistance from the traced v(CE) - i

  • 35.
    Astapov, Victor
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems. Tallinn Univ Technol, Sch Engn, Tallinn, Estonia.
    Astero, Poria
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    The Potential of Distribution Grid as an Alternative Source for Reactive Power Control in Transmission Grid2018In: PROCEEDINGS OF THE 2018 19TH INTERNATIONAL SCIENTIFIC CONFERENCE ON ELECTRIC POWER ENGINEERING (EPE), Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 64-69Conference paper (Refereed)
    Abstract [en]

    Nowadays, the global trend in the energy sector is the spreading use of renewable energy, especially wind generators and solar panels. The high concentration of such sources in distribution grid increases the voltage in case of small load demands and high production which effects the voltage at connection point and, in turn, in transmission grid. To regulate voltage and control reactive power, system operators install costly equipment in transmission grids. This paper considers alternative way of voltage and reactive power managing and discovers possibilities of PV converters in MV and LV grids with different type of control to solve this problem.

  • 36.
    Astero, Poria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems. State University of New York, USA.
    Choi, Bong Jun
    Liang, Hao
    Söder, Lennart
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Transactive Demand Side Management Programs in Smart Grids with High Penetration of EVs2017In: Energies, E-ISSN 1996-1073, Vol. 10, no 10, article id 1640Article in journal (Refereed)
    Abstract [en]

    Due to environmental concerns, economic issues, and emerging new loads, such as electrical vehicles (EVs), the importance of demand side management (DSM) programs has increased in recent years. DSM programs using a dynamic real-time pricing (RTP) method can help to adaptively control the electricity consumption. However, the existing RTP methods, particularly when they consider the EVs and the power system constraints, have many limitations, such as computational complexity and the need for centralized control. Therefore, a new transactive DSM program is proposed in this paper using an imperfect competition model with high EV penetration levels. In particular, a heuristic two-stage iterative method, considering the influence of decisions made independently by customers to minimize their own costs, is developed to find the market equilibrium quickly in a distributed manner. Simulations in the IEEE 37-bus system with 1141 customers and 670 EVs are performed to demonstrate the effectiveness of the proposed method. The results show that the proposed method can better manage the EVs and elastic appliances than the existing methods in terms of power constraints and cost. Also, the proposed method can solve the optimization problem quick enough to run in real-time.

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  • 37.
    Astero, Poria
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Improvement of RES hosting capacity using a central energy storage system2017In: 2017 IEEE PES Innovative Smart Grid Technologies Conference Europe (ISGT-Europe), Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    High penetration of renewable energy sources (RESs) in distribution systems leads to reverse active power and voltage rise in low voltage (LV) grids, which limits the hosting capacity. Energy storage systems (ESSs) have been used to improve the hosting capacity by decreasing the reverse active power in some literature. ESSs can still improve the hosting capacity more by providing reactive power. The reactive power shows a little effect in existing researches, because they have mostly simulate LV grids without modeling transformers. However, the high reactance of the transformer magnifies the effectiveness of the reactive power control even more than the active power in some buses. This paper develops an optimal method for placement, sizing, and active and reactive power control of a central ESS to improve the hosting capacity. The simulation results in highly RES penetrated grids at Germany show the effectiveness of the proposed method.

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    Accepted version
  • 38.
    Astero, Poria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Improving Hosting Capacity of Rooftop PVs by Quadratic Control of an LV-Central BSS2017In: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. PP, no 99, p. 1-1Article in journal (Refereed)
    Abstract [en]

    High integration of rooftop photovoltaic (PV) plants in distribution systems leads to new technical challenges: reverse-active power and voltage rise in low-voltage (LV) and medium-voltage (MV) grids. These challenges limit the maximum amount of power can be produced by PVs in LV and MV grids, called the hosting capacity (HC). Battery storage systems (BSSs) have been used in many studies to decrease the reverse power and improve the HC by controlling the active power. However, the influence of a central BSS on the HC can be greatly improved by using a quadratic power control, simultaneous active and reactive power control, and by selecting of the optimal battery size, the converter size, and the place of the central BSS. The effectiveness of the quadratic power control was not seen in previous works due to the fact that grids with one level of voltage without modeling of MV/LV transformers were simulated. This paper develops a method to select the optimal size of the battery and converter unit as well as the optimal place of an LV-central BSS having an optimal quadratic power control. The simulation results show considerable effects of the optimal selection of an LV-central BSS on the HC improvement.

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  • 39.
    Astero, Poria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Improving PV Dynamic Hosting Capacity Using Adaptive Controller for STATCOMs2019In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 34, no 1, p. 415-425Article in journal (Refereed)
    Abstract [en]

    High penetrations of renewable energy sources (RES) in distribution grids lead to new challenges in voltage regulation. These challenges are not just limited to the steady-state voltage rise, but they are extended to rapid voltage changes due to wind speed variations and moving clouds, casting shadows on photovoltaic panels. According to EN50160 in low-voltage (LV) grids, the steady-state voltage should not exceed 1.1 pu (static characteristic), and rapid voltage changes should be kept less than 0.05 pu (dynamic characteristic). These two characteristics may limit the maximum amount of RES that can be installed in LV grids, called, respectively, the static hosting capacity (SHC) and dynamic hosting capacity (DHC). Although existing research just evaluated SHC in distribution grids, high-penetrated RES grids can be faced with such large voltage changes, which cause a smaller DHC than the SHC. This paper studies both SHC and DHC in distribution grids and proposes an adaptive controller for static synchronous compensators to regulate the steady-state and dynamic voltage while avoiding the unnecessary increase in the reactive power. The simulation results in some German distribution grids show considerable effects of the proposed adaptive controller on improving both SHC and DHC.

  • 40.
    Astero, Poria
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Improving PV Hosting Capacity of Distribution Grids Considering Dynamic Voltage Characteristic2018In: 2018 POWER SYSTEMS COMPUTATION CONFERENCE (PSCC), Institute of Electrical and Electronics Engineers (IEEE) , 2018Conference paper (Refereed)
    Abstract [en]

    Since the penetration of renewable energy sources is rapidly increasing in distribution grids, the hosting capacity (HC) of distribution systems becomes the main concern. According to EN 50160, in LV grids, the mean value of voltage cannot exceed 1.1 pu (static characteristic) and voltage rapid changes should be kept less than 0.05 pu (dynamic characteristic). Existing researches evaluated the HC of distribution grids just based on the static characteristic. However, wind speed variations and rapid moving cloud, casting shadow on solar panels, can cause rapid voltage changes in LV grids. This paper studies the rapid voltage change by modeling the moving cloud shadow and compares the HC from perspective of both dynamic and static characteristic, which is not done before. Since voltage dynamic characteristic could be more restrictive than the static characteristic, as shown in a German distribution grid, a static synchronous compensator (STATCOM) is proposed and controlled to regulate dynamic voltage profile and to improve the HC.

  • 41.
    Atzarakis, N.
    et al.
    School of Electrical and Computer Engineering , National Technical University of Athens , Greece.
    Kouveliotis Lysikatos, Iasonas
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Palaiogianis, F.
    School of Electrical and Computer Engineering , National Technical University of Athens , Greece.
    Vasilakis, A.
    School of Electrical and Computer Engineering , National Technical University of Athens , Greece.
    Tsekeris, D.
    School of Electrical and Computer Engineering , National Technical University of Athens , Greece.
    Hatziargyriou, N.
    School of Electrical and Computer Engineering , National Technical University of Athens , Greece.
    SMART energy communities: A case study for Greece2020In: IET Conference Publications, Institution of Engineering and Technology (IET) , 2020, no CP767, p. 136-139Conference paper (Refereed)
    Abstract [en]

    In this study, the authors investigate the economic feasibility of an energy community investing in renewable energy sources (RES). The estimation is based on the optimisation of the total annual average electricity costs of a typical study case that uses historical load and RES generation data and follows the directives of the Greek recent legislation for energy communities. The operation of a local energy market is compared with other available RES pricing mechanisms, such as self-consumption, feed-in-tariff and net metering.

  • 42.
    Augustin, Tim
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Enhanced Active Resonant DC Circuit Breakers for HVDC Grids2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    High-voltage DC (HVDC) grids are considered promising for the electricity grid expansion required to integrate renewable energy sources into the existing infrastructure. DC fault currents increase rapidly and lack a current zero crossing. Therefore, HVDC grids require complex DC circuit breakers (DCCBs) capable of interrupting faster than AC circuit breakers to protect against DC faults. Being complex, DCCBs can offer functionality in addition to interruption. Most DCCBs can be categorized as current-injection DCCBs or hybrid DCCBs. Hybrid DCCBs feature more functionality than current-injection DCCBs. Nevertheless, the power semiconductors used in hybrid DCCBs are expensive. The enhanced active resonant (EAR) DCCBs studied in this work are an intermediate solution with the functionality of hybrid DCCBs and the interruption mechanism of current-injection DCCBs. The core of EAR DCCBs are discharge closing switches, which are simple, robust and available for high current and high voltage.

    Like all HVDC DCCBs, EAR DCCBs need a fast mechanical switch. A Thomson-coil actuator with active damping is used to open and close the mechanical switch fast. A novel Thomson-coil driver recycling energy during actuation simplifies the Thomson-coil actuator system. Experimental results demonstrate the open-close and open-close-open operation of the Thomson-coil actuator. Extensive experimental studies investigate the DC interruption capability and functionality of a prototype EAR DCCB in a specialized DCCB test circuit. The tests results show that the prototype EAR DCCB can interrupt up to 1.2 kA, abort proactive commutation, and auto-reclose. The studies of the discharge closing switch used find that its minimum voltage is not a serious limitation and that the discharge can become unstable after commutationat low currents. An alternative commutation technique allows EAR DCCBs with less components to operate reliably at all currents.

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    Enhanced Active Resonant DC Circuit Breakers
  • 43.
    Augustin, Tim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Magnusson, Jesper
    ABB Corporate Research, Västerås.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Parekh, Mrunal
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    System Design of Fast Actuator for Vacuum Interrupter in DC Applications2018In: 2018 28th International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV), Institute of Electrical and Electronics Engineers (IEEE), 2018, Vol. 2, p. 527-530Conference paper (Refereed)
    Abstract [en]

    One of the major challenges of DC circuit breakers is the required fast mechanical actuator. In this paper, a Thomson coil actuator system for a vacuum interrupter is designed. Active damping is used to decelerate the moving contacts. Challenges are discussed, especially concerning the power supply needed for the Thomson coil actuator. The design philosophy is explained and FEM simulation results are presented. The results indicate that a wide range of combinations of drive circuit capacitance and voltage fulfill the requirements for armature acceleration. However, active damping requires a very careful selection of drive circuit voltage and timing of applied damping.

    Download full text (pdf)
    fulltext
  • 44.
    Augustin, Tim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Advanced Test Circuit for DC Circuit Breakers2018In: 20th European Conference on Power Electronics and Applications (EPE'18 ECCE EUROPE), 2018Conference paper (Refereed)
    Abstract [en]

    In future HVDC systems, many DC circuit breakers (DCCBs) will be required. In this paper, an advanced test circuit for DCCBs is described. A DC source is combined with a capacitor bank. In contrast to other test circuits, the proposed test circuit allows to replicate constant DC and temporary faults. In addition to conventional faults, this enables testing of auto-reclosing, proactive commutation, and complex test sequences combining all of these modes. The test circuit is easy to setup and also suitable for smaller research facilities. Experimental results from a down-scaled mock-up are included to demonstrate the capabilities of the test circuit.

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    fulltext
  • 45.
    Augustin, Tim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. ABB Corporate Research, Västerås, Sweden.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Enhanced Active Resonant DC Circuit Breakers Based on Discharge Closing Switches2021In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 36, no 3, p. 1735-1743Article in journal (Refereed)
    Abstract [en]

    Direct current circuit breakers (DCCBs) have become a large research topic and are considered one of the critical components for future DC grids. Proposed DCCB concepts may be grouped into hybrid DCCBs and active resonant DCCBs. In this work, the enhanced active resonant (EAR) DCCB family is introduced. EAR DCCBs combine elements of hybrid and active resonant DCCBs. The EAR DCCB family consists of one unidirectional and six bidirectional concepts. All concepts feature proactive commutation. The main characteristic of the EAR DCCBs is that discharge closing switches are used instead of semiconductors with turn-off capability. Relevant discharge closing switch technology is reviewed, a laboratory prototype is explained, and experimental results are presented to demonstrate the feasibility of the proposed DCCB concepts.

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    fulltext
  • 46.
    Augustin, Tim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. ABB.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Experimental Study of Enhanced Active Resonant DC Circuit Breakers2022In: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 37, no 5, p. 5687-5698Article in journal (Refereed)
    Abstract [en]

    Enhanced active resonant (EAR) dc circuit breakers (DCCBs) are a novel type of DCCB that use a discharge closing switch as interruption medium. A technical limitation of discharge closing switches is the minimum voltage across the main gap required for successful triggering. A novel commutation process creating the minimum voltage internally is proposed, which allows to simplify the EAR DCCB configuration and to reduce its component count. In the prototype, the discharge closing switch is implemented with a TVG. Experiments show that the TVG can be triggered reliably down to a voltage of 50 V and that the discharge in the TVG is highly oscillatory at low current. The originally proposed EAR DCCB configuration has to be tuned such that the commutation to the TVG succeeds at low current. Conversely, the novel commutation process decouples the minimum voltage from the current level by adjusting the triggering delay. This allows reliable commutation irrespective of the operating conditions. It is shown that the novel commutation process does not adversely affect dc interruption. Proactive commutation operation and auto-reclosing strategies are demonstrated.

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    fulltext
  • 47.
    Augustin, Tim
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Parekh, Mrunal
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Magnusson, Jesper
    ABB.
    Becerra Garcia, Marley
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. ABB.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Thomson-Coil Actuator System for Enhanced Active Resonant DC Circuit Breakers2022In: IEEE Journal of Emerging and Selected Topics in Power Electronics, ISSN 2168-6777, E-ISSN 2168-6785, Vol. 10, no 1, p. 800-810Article in journal (Refereed)
    Abstract [en]

    Enhanced active resonant (EAR) dc circuit breakers (DCCBs) are a promising set of recently proposed DCCB concepts. As other DCCBs, EAR DCCBs still require a fast mechanical switch. The requirements on the actuator of the mechanical switch depend on the DCCB concept and the dc grid and are derived here for an EAR DCCB. Thomson-coil actuators (TCAs) can open and close mechanical switches sufficiently fast to satisfy the requirements. This work studies experimentally a TCA system with active damping for an off-the-shelf industrial vacuum interrupter used as mechanical switch in an EAR DCCB. The prototype is explained in detail, and extensive measurement results are presented, showing that active damping must be perfectly timed to be effective. A novel Thomson-coil (TC) driver is proposed and studied experimentally, which operates the TCA more efficiently by recycling energy during the actuation. Moreover, the novel TC driver reduces the capacitive storage by 50% and allows for faster recharging with lower charging current. Finally, the autoreclosing and proactive commutation operation of the TCA system and the interruption capability of the prototype EAR DCCB are demonstrated experimentally.

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    fulltext
  • 48.
    Azizi, Ali
    et al.
    Iran University of Science and Technology, Department of Electrical Engineering, Tehran, Iran.
    Jahromi, Mehdi Zareian
    Amirkabir University of Technology, Department of Electrical Engineering, Tehran, Iran.
    Dehghanian, Pooria
    Texas A&M University, Department of Electrical and Computer Engineering, College Station, TX, USA.
    Chamorro Vera, Harold Rene
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Mirez, Jorge
    Universidad Nacional de Ingeniería (UNI), Group of Mathematical Modeling and Numerical Simulations, Lima, Peru.
    Sood, Vijay K.
    Ontario Tech University, Department of Electrical, Computer and Software Engineering, Oshawa, ON, Canada.
    Decentralized Multi-Objective Energy Management With Dynamic Power Electronic Converters and Demand Response Constraints2023In: IEEE Access, E-ISSN 2169-3536, Vol. 11, p. 146297-146312Article in journal (Refereed)
    Abstract [en]

    Energy management plays a pivotal role in enhancing the economic efficiency of power systems. However, it is noteworthy that a substantial number of microgrids (MGs) exhibit inherent unbalances that impose a range of critical issues, including voltage instability, elevated losses, power quality violations, safety concerns, and inefficiencies in energy management. Fast-acting power electronic converters present a relevant and efficacious solution for balancing such complex networks. This paper investigates the application of such converters within the realm of 3-phase unbalanced networks, wherein the proposed algorithm not only ameliorates network imbalances but also yields substantial reductions in operational costs, power losses, voltage deviations, and emissions. Demand response (DR) program has been applied to the model to enhance the system efficiency. The uncertainty about electric demand and renewable energy sources is considered in the simulation model for precise results. By implementing DR programs and penetrating distributed generators (DGs), the proposed model has been shown to reduce network losses and operation costs by 23% and 80%, respectively. Also, the total up-to-down voltage deviation of the voltage profile has been significantly reduced by 400%.

  • 49.
    Azuatalam, Donald
    et al.
    Univ Sydney, Sch Elect & Informat Engn, Sydney, NSW, Australia..
    Paridari, Kaveh
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Ma, Yiju
    Univ Sydney, Sch Elect & Informat Engn, Sydney, NSW, Australia..
    Foerstl, Markus
    Tech Univ Munich, Inst Elect Energy Storage Technol, Munich, Germany..
    Chapman, Archie C.
    Univ Sydney, Sch Elect & Informat Engn, Sydney, NSW, Australia..
    Verbic, Gregor
    Univ Sydney, Sch Elect & Informat Engn, Sydney, NSW, Australia..
    Energy management of small-scale PV-battery systems: A systematic review considering practical implementation, computational requirements, quality of input data and battery degradation2019In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 112, p. 555-570Article, review/survey (Refereed)
    Abstract [en]

    The home energy management problem has many different facets, including economic viability, data uncertainty and quality of strategy employed. The existing literature in this area focuses on individual aspects of this problem without a detailed, holistic analysis of the results with regards to practicality in implementation. In this paper, we fill this gap by performing a comprehensive comparison of seven different energy management strategies, each with different levels of practicality, sophistication and computational requirements. We analyse the results in the context of these three characteristics, and also critique the modelling assumptions made by each strategy. Our analysis finds that using a more sophisticated energy management strategy may not necessarily improve the performance and economic viability of the PV-battery system due to the effects of modelling assumptions, such as the treatment of uncertainties in the input data and battery degradation effects.

  • 50.
    Babazadeh, Davood
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Hohn, Fabian
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Wu, Yimin
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Nordström, Lars
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Distributed Two-stage Network Topology Processor for HVDC Grid Operation2017In: 2017 IEEE POWER & ENERGY SOCIETY GENERAL MEETING, IEEE , 2017Conference paper (Refereed)
    Abstract [en]

    This paper presents the results of an analysis of distributed two-stage coordination of network topology processor for HVDC grids. In the first stage of the two-stage processor, the substation topology is analyzed locally using an automated graph based algorithm. Thereafter, a distributed algorithm is proposed to used the neighboring information to realize the grid connectivity. For distributed islanding detection, the connectivity problem is formulated as a set of linear equations and solved iteratively using successive-over-relaxation method. The performance of the proposed methods versus conventional one-stage method has been tested in an islandinv, scenario for a 5-terminal HVDC grid.

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