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1.
  • Chen, Peiyuan, 1983, et al. (author)
  • Stochastic evaluation of maximum wind capacity in a radial distribution network
  • 2011
  • In: IEEE PES Innovative Smart Grid Technologies Conference Europe. 2011 2nd IEEE PES International Conference and Exhibition on Innovative Smart Grid Technologies, ISGT Europe 2011, Manchester, 5 - 7 December 2011. - 9781457714214
  • Conference paper (peer-reviewed)abstract
    • This paper proposes an optimization algorithm to find the maximum wind installation in a radial distribution network. The algorithm imposes a limit on the amount of wind energy that can be curtailed annually. The algorithm implements the wind turbine reactive power control and wind energy curtailment using sensitivity factors. The optimization is integrated with Monte Carlo simulation to account for the stochastic behavior of load demand and wind power generation. The proposed algorithm is tested on a real 20 kV Danish distribution system in Støvring. It is demonstrated that the algorithm executes reactive compensation and energy curtailment sequentially in an effective and efficient manner.
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2.
  • Nursebo, Shemsedin, 1983, et al. (author)
  • Maximizing Wind Power Integration in Distribution System
  • 2011
  • In: 10th International Workshop on Large-Scale Integration of Wind Power into Power Systems as well as on Transmission Networks for Offshore Wind Power Plants. - 9783981387032
  • Conference paper (peer-reviewed)abstract
    • Due to the location of favorable wind sites and lower connection costs associated with installing wind power in a distribution system, there is a need to know the hosting capacity of a distribution system so that it can be used effectively for injecting wind power into the power system. Therefore this paper presents a methodology to investigate the wind power hosting capacity of a distribution system. Stochastic nature of wind power and customer loads is taken into account using copulas. Hence it is possible to investigate various levels of correlation among customer loads. A simple algorithm is proposed for selecting the connection points of wind power in the network. The effectiveness of active management strategies such as wind power curtailment and reactive power compensation are thoroughly investigated. The analysis shows that allowing a curtailment level of as low as 0.2% with power factor (PF) control of wind turbines could boost the hosting capacity by 118%.
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3.
  • Nursebo, Shemsedin, 1983, et al. (author)
  • On Coordinated Control of OLTC and Reactive Power Compensation for Voltage Regulation in Distribution Systems With Wind Power
  • 2016
  • In: IEEE Transactions on Power Systems. - 0885-8950 .- 1558-0679. ; 31:5, s. 4026-4035
  • Journal article (peer-reviewed)abstract
    • Active management strategies such as coordinated on load tap changer (OLTC) voltage control and reactive power compensation (RPC) are frequently suggested for voltage regulation in a distribution system with a high level of distributed generation (DG). This paper proposes a control and coordination algorithm for these two active management strategies. Voltage control through OLTC is achieved by using state estimation (SE) to determine the voltage in the network. To lower the implementation cost of the proposed control strategy, pseudo-measurements are used together with real-time measurement data in the SE. Moreover, the deadband of the automatic voltage control (AVC) relay is relaxed so that the AVC relay acts on the network's maximum or minimum voltage obtained through the SE. This is found to be simpler to realize than adjusting the set point of the AVC relay. Voltage control through RPC is actualized by using integral controllers implemented locally at the wind turbine site. Furthermore, RPC from the local wind turbine is also used to mitigate an overvoltage at a remote bus on the same feeder when the remote wind turbine reaches its regulation limit. The applicability of the proposed voltage regulation algorithm is successfully demonstrated using a case study system
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4.
  • Nursebo, Shemsedin, 1983, et al. (author)
  • Optimizing Wind Power Hosting Capacity of Distribution Systems Using Cost Benefit Analysis
  • 2014
  • In: IEEE Transactions on Power Delivery. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8977 .- 1937-4208. ; 29:3, s. 1436-1445
  • Journal article (peer-reviewed)abstract
    • The penetration of wind power into the electricity grid is growing significantly. A significant portion of this wind power is being installed in distribution systems, of which most are passively operated. Under this operating practice, wind power can only be admitted based on minimum load and maximum generation consideration. This severely limits the wind power hosting capacity of the system. Hence, the use of active-management strategies (AMSs) has been proposed to increase the hosting capacity of distribution systems. This paper incorporates AMSs into two optimization models whose objectives are to maximize the net benefit of distribution system operator and wind farm owner, respectively. The AMSs considered are wind energy curtailment, coordinated on-load tap changer voltage control, and reactive power compensation. The models development is based on a typical medium-voltage distribution system in Sweden although it can easily be adapted to other cases. The application of the model to a distribution system in Sweden shows an increase in hosting capacity of the distribution system by 78% with mere 2.6% curtailed energy. That is, the hosting capacity of the distribution system has almost been doubled by using AMSs.
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5.
  • Nursebo, Shemsedin, 1983, et al. (author)
  • The Effect of Wind Power Integration on the Frequency of Tap Changes of a Substation Transformer
  • 2013
  • In: IEEE Transactions on Power Systems. - 0885-8950 .- 1558-0679. ; 28:4, s. 4320 - 4327
  • Journal article (peer-reviewed)abstract
    • As the capacity of wind power installed in a radial distribution system (DS) increases, there is a concern that it may introduce more frequent tap change operations in substation transformers. The increase in the frequency of tap changes (FTC) can accelerate the wear and tear of the tap changers. As a result, the introduction of wind power to DSs may be hindered. Hence the aim of this paper is to investigate the effect of wind power integration on the FTC in a radial DS. A case study shows that the changes on the FTC in DSs connected to relatively strong external grid is negligible up to significant level of penetration. But in DSs connected to a relatively weak external grid, a significant increase in the FTC has been observed as wind power penetration increases. Hence a further investigation is carried out to limit the FTC by using reactive power from local wind turbines. The results have shown that the methodology is very effective.
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6.
  • Nursebo, Shemsedin, 1983, et al. (author)
  • USING REACTIVE POWER FROM WIND TURBINES FOR LOSS REDUCTION IN DISTRIBUTION SYSTEM
  • 2014
  • In: CIRED Workshop - Rome.
  • Conference paper (other academic/artistic)abstract
    • Considering the majority of the power losses occur indistribution systems, it is worthwhile to investigate the use of reactive power compensation (RPC) from wind turbines installed in the distribution system for loss reduction. Therefore, this paper analyses the effectiveness of the RPC for loss reduction under different system conditions. These include power factor of the system load, X/R ratio of the cables, and the electrical location of the wind turbines. The result of the analysis shows that the effectiveness of RPC for loss minimization mainly depends on the power factor of theload followed by the location of the wind turbine in thesystem. In this regard, in a system where the average load power factor is around unity, e.g. 0.98, RPC is not attractive for loss reduction. However, when the average power factor of the load is around 0.90, RPC is able to decrease the system loss by around 20%. Though the 2/3 rule can be applied to site wind turbine for maximum loss reduction through the use of RPC, the overall sitting problem of the wind turbine is more likely to be dependent on its active power output rather than RPC. The X/R ratio of the cable, on the other hand, has very little impact on the effectiveness of the approach.
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7.
  • Siano, Pierluigi, et al. (author)
  • Optimal Allocation of Wind Turbines in Active Distribution Networks by Using Multi-Period Optimal Power Flow and Genetic Algorithms
  • 2012
  • In: Modeling and Control of Sstainable Power Systems : Towards Smarter and Greener Electric Grids. - 9783642229039 ; , s. 20-
  • Book chapter (other academic/artistic)abstract
    • In order to achieve an effective reduction of green house gas emissions, the future electrical distribution networks will need to accommodate higher amount of renewable energy based on distributed generation such as Wind Turbines. This will require a re-evaluation and most likely a revision of traditional methodologies, so that they can be used for the planning and management of future electrical distribution networks. Such networks evolve from the current passive systems to active networks and smart grids, managed through systems based on Information Communication Technology.This chapter proposes a hybrid optimization method that aims of maximizing the Net Present Value related to the Investment made by Wind Turbines developers in an active distribution network. The proposed network combines a Genetic Algorithm with a multi-period optimal power flow. The method, integrating active management schemes such as coordinted voltage control, energy curtailment and power factor control is demonstrated on a 69-bus 11kV radial distribution network.
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8.
  • Yunus, Kalid, 1983, et al. (author)
  • ARIMA-based frequency-decomposed modelling of wind speed time series
  • 2016
  • In: IEEE Transactions on Power Systems. - 0885-8950 .- 1558-0679. ; 31:4, s. 2546-2556
  • Journal article (peer-reviewed)abstract
    • In this article, a modified ARIMA (Auto RegressiveIntegrated Moving Average) modelling procedure that can capture time correlation and probability distribution of observed wind speed time series data is presented. The procedure introduces frequency decomposition (splitting the wind speed data into HF(High Frequency) and LF(Low Frequency) components), shifting and limiting in addition to differencing and power transformation which are used in the standard ARIMA modelling procedure. The modified modelling procedure is applied to model 10 minute average measured wind speed data from three locationsin the Baltic Sea area and the results show that the procedure can capture time correlation and probability distribution of the data. In addition, it is shown that, for 10 minute average wind speed data in the Baltic Sea area, it could be sufficient to use ARIMA(6,0,0) and ARIMA(0,1,6) to model the HF and the LF components of the data, respectively. It is also shown that, in the Baltic Sea area, a model developed for an observed wind speeddata at one location could be used to simulate wind speed data at a nearby location where only the average wind speed is known.
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9.
  • Yunus, Kalid, 1983, et al. (author)
  • Modelling spatially and temporally correlated wind speed time series over a large geographical area using VARMA
  • 2017
  • In: IET Renewable Power Generation. - : Institution of Engineering and Technology (IET). - 1752-1424 .- 1752-1416. ; 11:1, s. 132-142
  • Journal article (peer-reviewed)abstract
    • This study presents a modified vector auto-regressive moving average (VARMA) modelling procedure to model spatially and temporally correlated wind speed time series over wide geographical areas. The standard VARMA is normally used to model stationary time series with Gaussian distribution. However, wind speed is non-stationary (mean and variance varies over time) and non-Gaussian. Hence, a method that can be used to transform wind speed data into a stationary and Gaussian time series is introduced in the modified procedure. To show the applicability of the procedure for different scenarios, six cases are investigated in the North and the Baltic Sea. The results show that the procedure can be used to model spatially and temporally correlated wind speed over a large geographical area. In addition, the resulting model can capture probability distribution and periodic characteristics of the wind speed data. Furthermore, based on the investigated case, it is shown that a vector auto-regressive model of order three is a reasonable model structure which can be used to model spatially and temporally correlated wind speed in the North and the Baltic Sea area provided that the power transformed wind speed data is normalised by its monthly mean value and its variance.
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10.
  • Chen, Peiyuan, 1983, et al. (author)
  • Analysis of Energy Curtailment and Capacity Over-Installation to Maximize Wind Turbine Profit Considering Electricity Price-Wind Correlation
  • 2018
  • In: 2018 IEEE POWER & ENERGY SOCIETY GENERAL MEETING (PESGM). - 1944-9925. - 9781538677032
  • Conference paper (peer-reviewed)abstract
    • This paper proposes a strategy of using wind energy curtailment and capacity over-installation to increase the profit of wind turbine (WT) installations in a local grid, accounting for the correlation between the local wind power production and system electricity price. It is demonstrated that the market value of a local wind power production in Denmark would be overestimated by 11% if the average electricity price is used without considering the price-wind correlation. A first-order relation is developed to quantify the correlation between the electricity price and local wind power production to evaluate the market value and the expected revenue of the wind power. Furthermore, in the analyzed cases of a local WT installation, compared to the case with no curtailment, the profits are increased by up to 46% through 29% of energy curtailment and 113% of capacity over-installation, when the slope of the price-wind relation is 100 €/MWh. It is also verified that the approximated analytical solutions give accurate results of the optimal curtailment level.
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11.
  • Chen, Peiyuan, 1983, et al. (author)
  • Analysis of Energy Curtailment and Capacity Overinstallation to Maximize Wind Turbine Profit Considering Electricity Price-Wind Correlation
  • 2017
  • In: IEEE Transactions on Sustainable Energy. - : Institute of Electrical and Electronics Engineers (IEEE). - 1949-3029 .- 1949-3037. ; 8:4, s. 1406-1414
  • Journal article (peer-reviewed)abstract
    • This paper proposes a strategy of using wind energy curtailment and capacity overinstallation to increase the profit of wind turbine (WT) installations in a local grid, accounting for the correlation between the local wind power production and system electricity price. It is demonstrated that the market value of a local wind power production in Denmark would be overestimated by 11% if the average electricity price is used without considering the price-wind correlation. A first-order relation is developed to quantify the correlation between the electricity price and local-wind power production to evaluate the market value and the expected revenue of the wind power. Furthermore, in the analyzed cases of a local WT installation, compared to the case with no curtailment, the profits are increased by up to 46% through 29% of energy curtailment and 113% of capacity overinstallation, when the slope of the price-wind relation is 100 (sic)/MWh. It is also verified that the approximated analytical solutions give accurate results of the optimal curtailment level.
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12.
  • Chen, Peiyuan, 1983 (author)
  • Day-ahead Reserve Capacity Procurement based on Mixed-Integer Bilevel Linear Programming
  • 2016
  • In: IEEE Power and Energy Society General Meeting. - 1944-9925 .- 1944-9933. - 9781509041671 ; 2016-November, s. 5-
  • Conference paper (peer-reviewed)abstract
    • This paper models the the reserve capacity procurement problem in Denmark to account for the sequential clearing of the reserve availability market and the energy market, and the forecast error of system wind power and demand. The problem is modeled as a stochastic mixed-integer bilevel linearing programming problem. A real case of Western Denmark is studied. In the case analyzed, the EENS induced by the forecast error reduces from 312.4 MWh to 0 when 40 MW reserve capacity is procured. It is also shown that procuring more reserve capacity does not necessarily reduce the EENS.
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13.
  • Chen, Peiyuan, 1983, et al. (author)
  • Time-Series Based Cable Selection for a Medium Voltage Wind Energy Network
  • 2012
  • In: IEEE Transactions on Sustainable Energy. - 1949-3029 .- 1949-3037. ; 3:3, s. 9-473
  • Journal article (peer-reviewed)abstract
    • This paper analyzes various factors that influence the cable selection for delivering wind energy to an electrical network. It also investigates when the thermal and voltage limit become the dominant limiting factor in order to obtain the correct economical loading range (ELR) and load reach of a cable. In addition, the influence of power factor setting and capacity factor of wind turbines on cable sizing are also presented. To account for the stochastic behavior of wind power and electricity price, time series measurements are employed to evaluate the cost of energy losses in a cable. Procedures are summarized to illustrate the cable selection for a wind energy network. The illustration is performed on a 20 kV wind energy network in Sweden. The results indicate that electricity price, discount rate and wind turbine capacity factor affect the ELR of the cable significantly. On the other hand, when the number of evaluation year is reduced from 40 years to 20 years, the ELR does not vary significantly. Furthermore, in the case of no voltage violation, the cable length does not affect the ELR. Moreover, the power factor setting of wind turbines does not affect ELR, but has a significant influence on the load reach of a cable. For the case network with 28 MW wind installation, 8% savings are obtained when using the selected economical cables instead of the thinnest cables; 2% savings are obtained when using the optimal power factor instead of the unity power factor. The cable selection method proposed in this paper can be used by both wind farm designers and network operators to select cables for their wind energy collection grids.
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14.
  • Chouhy Leborgne, Roberto, 1972, et al. (author)
  • Using PQ-monitor and PMU for voltage sag extended-characterization
  • 2006
  • In: IEEE PES Transmission and distribution Conference and Exposition Latin America. - 9781424402878 ; , s. 17-22
  • Conference paper (peer-reviewed)abstract
    • This paper deals with a broad investigation on the voltage sag extended-characterization. All types of faults are generated in a scaled network model and a power quality-monitor and a PMU (phasor measurement unit) are used to obtain the voltage sag indices. The sag indices are also obtained through time-domain fault simulations using PSCAD/EMTDC. The measurement results are compared with the fault simulation. Several load conditions are tested. The analysis provides an overview of how accurate the voltage sag extended-characterization is when applying the usual simulation tools. Moreover, the results of the measurements obtained by the power quality-monitor and the PMU are compared.
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15.
  • Fürst, Kristoffer, 1990, et al. (author)
  • Hierarchical LSTM-Based Classification of Household Heating Types Using Measurement Data
  • 2024
  • In: IEEE Transactions on Smart Grid. - 1949-3053 .- 1949-3061. ; 15:2, s. 2261-2270
  • Journal article (peer-reviewed)abstract
    • A lack of knowledge of the heating systems used by electricity consumers impedes distribution system operators in developing a sound grid upgrade plan and estimating potential demand flexibility from these consumers. The large-scale rollout of smart meters for electricity consumers provides an excellent opportunity to identify end users’ heating types. This paper proposed a hierarchically structured deep-learning framework for identifying heating types of individual electricity consumers. The main contributions of the paper are: (a) We propose an effective framework based on long short-term memory (LSTM) that offers an effective automatic feature learning from sequential electricity consumption data and weather conditions. (b) We apply the proposed deep-learning architecture for household heating type classification which is among the first few successful reports on this application. We evaluate the performance using hourly measurement data collected over four years from one and two-family dwellings with either district heating, exhaust air heat pumps or direct electric heating as the heating type. Good performance was shown from the test results using the proposed framework, with an average test accuracy of 94.2%. Comparisons with four existing machine learning algorithms using handcrafted features and a single-layer LSTM-based deep-learning algorithm have shown marked improvement of the proposed method.
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16.
  • Fürst, Kristoffer, 1990, et al. (author)
  • Improved Peak Load Estimation from Single and Multiple Consumer Categories
  • 2020
  • In: IET Conference Publications. - : Institution of Engineering and Technology (IET). - 2515-0855. ; 2020:CP767, s. 178-181
  • Conference paper (peer-reviewed)abstract
    • Velander’s formula and coincidence factors have traditionally been used to estimate peak load for new connections in the distribution grid. By re-evaluating their underlying assumptions, this paper proposes two improved models for aggregated peak load estimation (PLE). For single-category load aggregation, the proposed coincidence factor model, by incorporating an average correlation coefficient, improves the model fitting by 76%–96% as compared to the standard Rusck model. For multiple-category load aggregation, the proposed joint Gaussian regression model reduces the PLE bias from 3%–34% to 0.2%–3% compared to the traditional approach. (see the full paper in 4 pages)
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17.
  • Fürst, Kristoffer, 1990, et al. (author)
  • Support vector machine for classification of households' heating type using load curves
  • 2023
  • In: IET Conference Proceedings. - 2732-4494. ; 2023:6, s. 3884-3888
  • Conference paper (peer-reviewed)abstract
    • The distribution system operator lacks the knowledge of the heating system used by their customers to make sound grid planning decisions. Energy declaration from buildings and the large-scale rollout of smart meters provides an excellent opportunity to classify the heating system used. This paper proposes a machine-learning-based approach using a support vector machine (SVM) with daily load curves (mean and standard deviation of consumption) extracted from smart meter measurements. Three heating types are analysed: district heating, exhaust air heat pump, and direct electric heating. The performance was compared among the classifiers using daily load curves extracted over one year, for each month, each week, and each day of the year. The highest average accuracy of 92.6% was obtained for the SVM classifier using daily load curves extracted for each week of a year as features. Furthermore, the classifier showed a higher performance than using an ensemble of SVM or random forest classifiers (90.6%/90.5%) proposed in the literature. Lastly, an error analysis of the misclassification was carried out, including building characteristics and geographical analysis.
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18.
  • Gustafsson, Magnus, 1965, et al. (author)
  • Internalising a threshold concept - what languages and channels are called for?
  • 2018
  • In: Proceedings från 6:e UTVECKLINGSKONFERENSEN för Sveriges ingenjörsutbildningar. - 9789188041111 ; , s. 87-93
  • Conference paper (peer-reviewed)abstract
    • We offer an example from Chalmers university of technology of how the landscape of English-medium instruction (EMI) might enable or hinder enhanced learning of crucial aspects like a threshold concept (TC) in an educational programme. The study is part of a larger 3-year study focussed on observing EMI-learning contexts to investigate whether or not the hypothesis of incidental language proficiency holds. The main focus of this pilot-level sub-project is to study how talk about specific threshold concepts and the degree of content expertise are reflected in student conversations. Both quantative analysis and qualitative analysis by the disciplinary faculty suggest that the two threshold concepts studied are not mastered as well as the faculty have assumed. The pilot study has resulted in revision of course design and exaplanatory models.
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19.
  • Hartvigsson, Elias, 1986, et al. (author)
  • Dataset for generating synthetic residential low-voltage grids in Sweden, Germany and the UK
  • 2021
  • In: Data in Brief. - : Elsevier BV. - 2352-3409. ; 36
  • Journal article (peer-reviewed)abstract
    • Assessing grid capacity on national and local levels is important in order to formulate renewable energy targets, calculate integration costs of distributed generation (such as residential solar PV and electric vehicles). Currently, 70–96% of the residential solar PV installations in Germany and Italy are found in the low-voltage grid. Previous grid assessments have relied on grid data from individual low-voltage grids, making them limited to a few cases. This article presents synthetic low-voltage grid data from a reference network model. The reference network model generates synthetic low-voltage grids using publicly available data and national regulations and standards. In addition, the article presents data of residential solar photovoltaic hosting capacity in low-voltage grids. The datasets are high-resolution (1 × 1 km) and contains data on electricity peak demand, share of population living in apartments and important grid metrics such as transformer capacity, maximum feeder length and estimations of residential solar photovoltaic hosting capacity. Datasets on grid components are rare and the dataset can be used to assess grid impacts from other residential end-use technologies, and function as baseline for other reference network models.
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20.
  • Hartvigsson, Elias, 1986, et al. (author)
  • Estimating national and local low-voltage grid capacity for residential solar photovoltaic in Sweden, UK and Germany
  • 2021
  • In: Renewable Energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 171, s. 915-926
  • Journal article (peer-reviewed)abstract
    • The electric grid's available capacity to accommodate solar photovoltaic on national scales is currently uncertain. This makes decisions about grid capacity expansion, which can be very costly for local grid operators, difficult to make. Yet, knowledge of national solar photovoltaic grid capacity is central in order to formulate realistic solar PV targets and strategies. We present a methodology based on publicly available data to estimate the grid's hosting capacity of residential solar photovoltaic at both the national and local scale. The model is applied to Sweden, Germany and the UK and shows that low-voltage grid capacity for residential solar photovoltaic is very large, 33 (+5/-7) GW (Sweden), 248 (+5/-24) GW (Germany) and 63 (+1/-14) GW UK, and similar to current total generation capacity. Based on our estimations, we find that with the capacity of the present grid Sweden can supply 24%, Germany 60% and UK 21% of their current annual net electricity consumption from residential solar photovoltaic. In addition, we find that the grid-supported individual solar PV system sizes increase as population density decreases. Finally, our work highlights the importance of implementing sizing incentives for customers when installing their solar PV systems.
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21.
  • Hartvigsson, Elias, 1986, et al. (author)
  • Generating low-voltage grid proxies in order to estimate grid capacity for residential end-use technologies: The case of residential solar PV
  • 2021
  • In: MethodsX. - : Elsevier BV. - 2215-0161. ; 8
  • Journal article (peer-reviewed)abstract
    • Due to data restrictions and power system complexity issues, it is difficult to estimate grid capacity for solar PV on regional or national scales. We here present a novel method for estimating low-voltage grid capacity for residential solar PV using publicly available data. High-resolution GIS data on demographics and dwelling dynamics is used to generate theoretical low-voltage grids. Simplified power system calculations are performed on the generated low-voltage grids to estimate residential solar PV capacity with a high temporal resolution. The method utilizes previous developments in reference network modelling and solar PV hosting capacity assessments. The method is demonstrated using datasets from Sweden, UK and Germany. Even though the method is designed to estimate residential solar PV grid capacity, the first block of the method can be utilized to estimate grid capacity or impacts from other residential end-use technologies, such as electric heating or electric vehicle charging. This method presents: • A method for estimating peak demand based on population density and dwelling type. • Generation of low-voltage grids based on peak demand. • Sizing of transformers and cables based on national low-voltage regulations and standards.
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22.
  • Hodel, Henrik, 1995, et al. (author)
  • Which wind turbine types are needed in a cost-optimal renewable energy system?
  • 2024
  • In: Wind Energy. - 1099-1824 .- 1095-4244. ; 27:6, s. 549-568
  • Journal article (peer-reviewed)abstract
    • Previous research has indicated that wind power plants can be designed to have less-variable power generation, thereby mitigating the drop in economic value that typically occurs at high wind power penetration rates. This study investigates the competitiveness of adapted turbine design and the interplay with other flexibility measures, such as batteries and hydrogen storage, for managing variations. The analysis covers seven turbine designs for onshore and offshore wind generation, with different specific power ratings and hub heights. Various flexibility measures (batteries, hydrogen storage and transmission expansion) are included in the optimization of investment and dispatch of the electricity system of northern Europe. Three driving forces for turbine design selection are identified: (1) lowest cost of electricity generation; (2) annual wind production per land area and (3) improved generation profile of wind power. The results show that in regions with good wind resources and limited availability of variation management, it is cost-efficient to reduce the variability of wind power production by adapting the turbine design. This remains the case when variation management is available in the form of batteries, hydrogen storage and transmission system expansion. Moreover, it is more cost-effective to improve variability by changing the specific power rating rather than the turbine hub height.
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23.
  • Hurtig, Oskar Nordlander, et al. (author)
  • Drivers and Barriers to Deploy Microgrid in Sweden
  • 2022
  • In: IEEE PES Innovative Smart Grid Technologies Conference Europe. - 9781665480321 ; 2022-October
  • Conference paper (peer-reviewed)abstract
    • This paper aims to identify drivers and barriers of microgrid deployment in Sweden for gaining insights on the upscaling potential of microgrid adoption in the country. Furthermore, two real-life distribution grids in southern Sweden are used to dimension the energy storage system (ESS) needed to enable island operation of the grids through power balance analysis. The results have also shown the benefit of interconnecting two adjacent distribution grids to form an interconnected microgrid. Through interconnection, the size of ESS can be reduced by around 23% as compared to operating two microgrids separately on their own. The analysis has also shown a potential to further reduce the ESS size if the weather information is considered.
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24.
  • Imgart, Paul, 1990, et al. (author)
  • Effective Inertia Constant: A Frequency-Strength Indicator For Converter-Dominated Power Grids
  • 2023
  • In: 2023 IEEE Belgrade PowerTech, PowerTech 2023.
  • Conference paper (peer-reviewed)abstract
    • The system inertia constant is the predominant indicator for power system frequency strength, but fails to account for non-inertial contributions such as fast frequency response. In this paper, the effective inertia constant is proposed as a new indicator to account for the contribution from both synchronous generators and power-electronic interfaced sources. Time-domain simulations show that the effective inertia constant is a better indicator for frequency nadir than the conventional inertia constant.
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25.
  • Imgart, Paul, 1990, et al. (author)
  • Evaluation of the System-Aggregated Potentials of Inertial Support Capabilities from Wind Turbines
  • 2019
  • In: Proceedings of 2019 IEEE PES Innovative Smart Grid Technologies Europe, ISGT-Europe 2019.
  • Conference paper (peer-reviewed)abstract
    • The increasing shift from synchronous towards converter interfaced generation and consumption changes the mechanical inertia in power systems. Thus it is of great importance for system operators to estimate the potentials of inertial support from the wind turbines connected to their systems. This paper utilizes metereological re-analysis data in conjunction with a wind turbine database in a novel way to estimate the inertial support capabilities of all wind turbines in Sweden. Using the wind speed profile across the country for the years 2010 - 2015, a linear relation between energy production and inertial support capability of 1.3 W s / W is shown for the investigated inertial support approach. Furthermore, the results show that the 7.48 GW installed converter-interfaced wind turbines in Sweden can provide, on average, kinetic energy of 2.72 GWs and inertial support power of 0.27 GW, which is equivalent to 19.3% of the Nordic system dimensioning fault.
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26.
  • Inamdar, Shoaib Salim, 1991, et al. (author)
  • On Benefits and Challenges of Nested Microgrids
  • 2019
  • In: Asia-Pacific Power and Energy Engineering Conference, APPEEC. - 2157-4847 .- 2157-4839. ; 2019-December
  • Conference paper (peer-reviewed)abstract
    • Nesting of microgrids enhances supply reliability, operational efficiency. and ancillary service support by optimizing distributed energy resource utilization. The availability of local reserve capacity within the nested microgrids (NMGs) enhances the local black start capability and can provide extra ancillary services to the main grid. However, NMG requires complex control and multiple communication layers, which makes it more vulnerable to control instability and cyber-attacks. Coordination of multivendor MGs is another challenge. This paper reviews the structure of a NMG, its associated benefits, challenges, and measures to assess its potential for large-scale application.
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27.
  • Kermani, Mostafa, 1986, et al. (author)
  • A comprehensive optimal energy control in interconnected microgrids through multiport converter under N−1 criterion and demand response program
  • 2022
  • In: Renewable Energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 199, s. 957-976
  • Journal article (peer-reviewed)abstract
    • Nowadays, the local distribution grids have been facing technical, economic, and regulatory challenges, because of the increased integration of renewable energy sources (RESs) and electrification of vehicles. The traditional solutions to the grid expansion, e.g., to build an additional power line, are utility-centered solutions, i.e., the distribution grid operators (DSOs) are the only party involved to tackle grid issues. The DSOs have to engage grid users with technology providers to develop innovative solutions that tackle one problem and overcome several cost-effectively. This paper presents a holistic solution to optimally control cross-sectoral energy flow between interconnected microgrids (MGs) consisting of different RESs, hydroelectric power plant (HPP) and wind turbines (WTs) to meet electric vehicles (EVs), residential, commercial and industrial demands with the main grid contribution. This issue will provide the advantages of community-based MGs for local energy trading which causes for an active and engaged system, however, an adequate control strategy for proper operation is required. The proposed solution is based on a new interconnection line between two MGs through a multiport converter (MPC) with the techno-economic consideration of newly installed components such as MPC, cables and the required battery energy storage system (BESS). The proposed case study is evaluated under three different conditions e.g., load increment, demand response (DR) and N-1 criterion in separate, interconnect and island modes. The CPLEX solver of GAMS software is employed to solve the mixed-integer linear programming model. The results show that the applied interconnection line for MGs compared to the separated operation mode can decrease the system's total costs, reduce the applied peak to the upstream grid, and enhance the system's reliability under different conditions. Furthermore, the applied solution provides the ability for MGs operation even in island mode under different conditions for a full day (24 h).
  •  
28.
  • Kermani, Mostafa, 1986, et al. (author)
  • Optimal Energy Control, Hosting BESS and EVs through Multiport Converter in Interconnected MGs
  • 2022
  • In: 2022 IEEE International Conference on Environment and Electrical Engineering and 2022 IEEE Industrial and Commercial Power Systems Europe, EEEIC / I and CPS Europe 2022.
  • Conference paper (peer-reviewed)abstract
    • This paper presents an optimal solution for energy control in interconnected microgrids (MGs) consisting of hydroelectric power plant (HPP) and wind turbines (WTs). The goal is to meet electric vehicles (EVs), residential, commercial, industrial and electric boiler demands with main grid contribution. The proposed solution is a new interconnection between MGs through a multiport converter (MPC) with the techno-economic evaluation for new components, e.g., MPC, cables and battery energy storage system (BESS). The system is investigated under different conditions e.g., load increment, demand response (DR) and N-1 criterion in separate, interconnect and island conditions. The results show that the proposed solution can decrease the total costs as well as peak demand and enhance reliability under different conditions.
  •  
29.
  • Khayat, Yousef, 1989, et al. (author)
  • Accurate power control of grid forming power converters for improving large-signal stability
  • 2023
  • In: IET Conference Proceedings. - 2732-4494. ; 2023:6, s. 3362-3366
  • Journal article (peer-reviewed)abstract
    • In modern power systems, fossil-fuel powered synchronous generators are being replaced by renewable generators with power electronic converters. This has raised concerns on the stability of the power system, of which grid operators have started to establish new requirement on power converters for providing grid-forming (GFM) functionalities. In particular, for large signal disturbances in the grid, GFM power converter needs to remain synchronized to the grid and provides support to the grid according to the requirement. This paper first uses phase portrait analysis to illustrate the transient stability of a gridconnected converter with GFM control during large-signal disturbances. A simple yet effective fault-ride-through (FRT) stabilizing control scheme is proposed to improve the synchronization stability of converter. In the proposed scheme, the active power reference for the active power control loop is proportionally adjusted with respect to the grid voltage, whereas an additional reactive power is injected to the grid with respect to the absolute value of active power unbalance. In the end, time-domain simulation is conducted to illustrate the effectiveness of the proposed FRT scheme for enhancing the transient stability of the gridconnected converters with GFM control.
  •  
30.
  • Khayat, Yousef, 1989, et al. (author)
  • FRT Capability of Grid-Forming Power Converters: an Anti-Windup Scheme
  • 2024
  • In: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 39:10, s. 12842-12855
  • Journal article (peer-reviewed)abstract
    • Fault ride-through requirements by grid codes necessitate grid-forming (GFM) power converters to operate stably during large grid disturbances such as voltage dips, voltage phase jumps, and rapid frequency changes. Nevertheless, the limited overcurrent capability of power converters deteriorates the transient synchronization stability during faults. To this end, this paper suggests an anti wind-up (AW) scheme from the hard current limiter block toward the active power loops (APL). In this way, the outer APL can recognize that the converter is in the saturated mode and that reference power exceeds the power limit injection that grid conditions allow; and therefore, the control effort should be modified in accordance with the allowable capacity. The proposed mechanism is first explained by presenting phase-portrait analysis through a nonlinear complex phasor model of the system; it is then shown a good correlation between the phasor domain and time domain findings. Finally, the effectiveness of the proposed method is shown through EMT simulations and experimental results.
  •  
31.
  • Mademlis, Georgios, 1992, et al. (author)
  • Design of Maximum Power Point Tracking for Dynamic Power Response of Tidal Undersea Kite Systems
  • 2020
  • In: IEEE Transactions on Industry Applications. - 0093-9994 .- 1939-9367. ; 56:2, s. 2048-2060
  • Journal article (peer-reviewed)abstract
    • The Tethered-Undersea-Kite (TUSK) represents a new electric power generation concept for harvesting energy from tidal currents, with higher power density compared to traditional static tidal turbines. However, the power and rotating speed of the turbine fluctuate periodically depending on the kite's motion in the sea creating an additional challenge for the speed control of the generator. The mathematical model of the system's power generation is developed. Two alternative Maximum-Power-Point-Tracking (MPPT) algorithms suitable for this application are designed. The electrical torque of the generator is controlled directly or a more accurate closed-loop speed controller is used. The turbine inertia creates an error between the optimal-reference power and the actual generated power. This error is evaluated experimentally for both MPPT-algorithms when fluctuating mechanical torque typical for the TUSK-system is applied on the generator. Experimental results on a 35kVA laboratory emulator are presented, where an accurate representation of the system dynamics and inertia are implemented.
  •  
32.
  • Mademlis, Georgios, 1992, et al. (author)
  • Generator Speed Control and Experimental Verification of Tidal Undersea Kite Systems
  • 2018
  • In: 2018 23rd International Conference on Electrical Machines (ICEM). - 2381-4802. - 9781538624777 ; , s. 1531-1537
  • Conference paper (peer-reviewed)abstract
    • Tethered-UnderSea-Kites (TUSK) represent a new electric power generation concept for harvesting the energy of the tidal current. A TUSK system has the advantage of increasing the extracted power from the tidal flow compared to a traditional static tidal turbine of the same size. This paper deals with the modeling and control of a TUSK tidal generator in order to estimate the energy production of such a system. A model of the generator drive mounted on a TUSK is presented in this paper. The produced power is periodically variating depending on the kite's motion into the sea and a suitable Maximum-Power-Point-Tracking (MPPT) algorithm for controlling the generator speed has been developed in order to maximize the power production. The developed control strategy of the drive has been experimentally verified with a 35kVA laboratory emulator of the TUSK and experimental results of several power production profiles are shown.
  •  
33.
  • Mazidi, Mohammadreza, 1987, et al. (author)
  • A Pure Data-Driven Method for Online Inertia Estimation in Power Systems Using Local Rational Model Approach
  • 2023
  • In: IEEE Transactions on Industry Applications. - 0093-9994 .- 1939-9367. ; 59:5, s. 5506-5516
  • Journal article (peer-reviewed)abstract
    • This paper presents an online data-driven method to estimate the inertia constant of synchronous generators (SGs) and the virtual inertia of converter-based resources (CBRs), which enables time-dependent inertia tracking in the normal operation of a power system. The proposed method is based on continuous monitoring of frequency response functions (FRFs) of SGs and CBRs, which are identified by ambient wide-area measurements of phasor measurement units (PMUs). To identify FRFs, a novel non-parametric approach, namely the local rational model (LRM), is used which does not require correct model order selection. LRM approach has a low computational burden and requires a short window of data, both of which are essential for estimating time-dependent inertia using ambient data. The applicability of the proposed method is evaluated in the IEEE 39-bus system and an actual system. The results demonstrate the accuracy, robustness to noise, and effectiveness of the proposed method in estimating the time-dependent inertia of power systems.
  •  
34.
  • Mohanty, Rabindra, 1989, et al. (author)
  • Challenges in Protection of Converter Dominated Medium-Voltage Microgrids
  • 2019
  • In: Proceedings of 2019 IEEE PES Innovative Smart Grid Technologies Europe, ISGT-Europe 2019. ; 2019
  • Conference paper (peer-reviewed)abstract
    • This paper presents a comprehensive review of major challenges in protection of medium-voltage microgrids with large amount of converter interfaced distributed generations (DGs). The challenges are mainly due to the limited fault current contributed by the DGs during the fault. This paper focuses on key issues with overcurrent protection schemes with various configurations of DGs and connection points. It was found that the current magnitude based conventional overcurrent relays would fail to operate in islanded operation of microgrids, while in grid-connected mode, the relays would operate but with extended time delay or would not operate for certain fault locations with high penetration of DGs. Overrated converter interfaced DGs would cause problems such as relay blinding and sympathetic tripping. The problems are examined and discussed in cases with DGs interfaced by rated and overrated converters in islanded and grid-connected operations, as well as in cases of different connection points of DGs, energy storage system and fault locations in the microgrid. The paper also attempts to suggest and discuss a number of protection solutions to the presented issues considering cost and reliability aspects.
  •  
35.
  • Mohanty, Rabindra, 1989, et al. (author)
  • Current restrained undervoltage protection scheme of converter dominated microgrids
  • 2020
  • In: IET Conference Publications. - : Institution of Engineering and Technology. ; Accepted for presentation
  • Conference paper (peer-reviewed)abstract
    • This paper presents a current restrained undervoltage protection method for converter dominated microgrids. Current magnitude based conventional protection fails to detect a fault in converter dominated microgrid due to current limiting capability of converters. Fault detection becomes more complicated during islanded operation of such a microgrid. This is because, the current does not exceed the rated value and remains below pickup setting of overcurrent relay during the fault. One alternative is to use undervoltage relay. However, this may not function correctly in the case of a fault at the end of a long cable or a high impedance fault. The current restrained undervoltage based proposed method does not rely on communication and the selectivity can be achieved by using a blinder in a VI-plane. Subsequently, the operating time of the relay is calculated using the index obtained from change in current and voltage inside the blinder. The performance of the proposed method is tested at different fault types and locations with different fault resistance in a converter dominated microgrid.
  •  
36.
  • Mohanty, Rabindra, 1989, et al. (author)
  • Protection of converter dominated MV microgrid using changes in current's phase angle
  • 2022
  • In: IET Generation, Transmission and Distribution. - : Institution of Engineering and Technology (IET). - 1751-8687 .- 1751-8695. ; 16:4, s. 656-668
  • Journal article (peer-reviewed)abstract
    • Converter interfaced distributed generations in a microgrid feed the modulated current of limited magnitude during fault conditions. The protection design and its operation are thus challenging due to limited fault current which is further reduced by Petersen coil grounding in medium-voltage (MV) level. This paper aims to address this challenge by developing a current-only directional relay algorithm for the protection of converter dominated MV microgrid with Petersen coil grounding. The relay’s operating principle is based on the sign of the change in phase angle of the fault current with respect to the prefault which indicates the direction of fault. The negative and positive changes in current’s phase angle determine the fault in forward and reverse direction, respectively. The tripping decision is derived by comparing the binary output of the relay at both ends of the line segment under protection. This requires a simple, flexible and low bandwidth communication channel. Both theoretical analyses and simulation studies have been performed on a typical distribution grid intended to be operated as microgrid. The proposed protection method is suitable for microgrid having the converters with and without reactive power support. Various operating conditions are evaluated, including bidirectional power flow, high resistance fault, different fault types, loading conditions and signals with noise.
  •  
37.
  • Motamed, Bardia, 1986, et al. (author)
  • Comparison of Primary Frequency Support Methods for Wind Turbines
  • 2013
  • In: IEEE POWERTECH 2013. - 9781467356695 ; , s. Art. no. 6652357-
  • Conference paper (peer-reviewed)abstract
    • This paper investigates and compares different methods of primary frequency control for wind power. The paper also identifies the models of hydro turbines and pitch regulated wind turbines. Short-term extra active power, inertia emulation and direct pitch angle regulation as a primary frequency control are evaluated when there is a power imbalance. In addition, the combinations of these three methods are evaluated. Simulation results show that the combination of temporary extra active power and inertia emulation method has the highest value of temporary minimum frequency. Although it is slower than other proposed methods and has second frequency drop. The advantage of using direct pitch angle regulation separately or in combining with the two other methods is that, the rotor speed does not decrease below the value that it has before the power imbalance happens.
  •  
38.
  • Narula, Anant, 1993, et al. (author)
  • Coordinated control of grid-forming converters and hydro generators to enhance frequency quality of future power system
  • 2022
  • In: Electric Power Systems Research. - : Elsevier BV. - 0378-7796. ; 212
  • Journal article (peer-reviewed)abstract
    • The aim of this paper is to propose a coordinated control strategy between grid-forming converters equipped with energy storage, and hydro generators to facilitate frequency support from the converters in future power systems. In this way, it is possible to take advantage of the fast dynamic properties of the converter system, and at the same time minimize the energy storage requirements associated with the converter system. The proposed tuning criterion for the frequency controller of the grid-forming converter facilitates a natural coordination between the converter system and hydro generators. The effectiveness of the proposed control strategy is compared against the conventional droop-based approach available in the literature. Finally, the analytical findings are validated using detailed time-domain simulation model in PSCAD.
  •  
39.
  • Narula, Anant, 1993, et al. (author)
  • Tuning and evaluation of grid-forming converters for grid-support
  • 2021
  • In: 2021 23rd European Conference on Power Electronics and Applications, EPE 2021 ECCE Europe.
  • Conference paper (peer-reviewed)abstract
    • Grid-forming converters interfacing renewable energy sources to the power system have emerged in recent years to account for the reduction of the conventional synchronous generators in the power system. This paper proposes a new structure and tuning approach for the active power controller of grid-forming converters. This is aimed at reducing the overshoot in the step-response of the active power controller, which is typically observed with other structures found in the literature. In order to ensure robustness of the proposed controller, the dynamic response of the active power injected by the converter is evaluated at various short-circuit ratio (SCR) of the grid. In addition, the performance of the converter system is investigated during parallel operation of converters in both grid-connected as well as islanded modes. Finally, the analytical findings are verified using detailed time-domain simulations in PSCAD.
  •  
40.
  • Persson, Mattias, 1984, et al. (author)
  • Frequency control by variable speed wind turbines in islanded power systems with various generation mix
  • 2017
  • In: IET Renewable Power Generation. - : Institution of Engineering and Technology (IET). - 1752-1424 .- 1752-1416. ; 11:8, s. 1101-1109
  • Journal article (peer-reviewed)abstract
    • This study presents the impact on power system frequency control in small power systems based on different generator topologies with a large penetration (50%) of variable speed wind turbines. The impact of a proposed controller is investigated versus various wind speeds. In particular, wind speeds with an average wind speed just below rated wind speed proves to cause the worst frequency fluctuations regardless of the type of backup generation topology investigated during 50% wind-penetration ratio. For this wind-speed session and a hydro-based system, the proposed control system improves the frequency duration outside of the specified range [49.9, 50.1]Hz from 81 to 53% while reducing its delivered energy by only 6%. Furthermore, the proposed control reduces the absolute value of requested reserve by 49% from the hydro unit responsible for primary frequency control.
  •  
41.
  • Persson, Mattias, 1984, et al. (author)
  • Frequency evaluation of the Nordic power system using PMU measurements
  • 2017
  • In: IET Generation, Transmission and Distribution. - : Institution of Engineering and Technology (IET). - 1751-8687 .- 1751-8695. ; 11:11, s. 2879-2887
  • Journal article (peer-reviewed)abstract
    • This study investigates the frequency behaviour in the Nordic power system (NPS) utilising phasor measurement units (PMUs) from different locations in the system. Different metrics are selected or proposed to quantify the system frequency response in case of major disturbances and of daily normal operations. Based on the collected PMU data, there are on average 17.5 major, generator disconnection related, disturbances per year. The maximum absolute rate of change of frequency exceeds 0.1 Hz/s for 20% of these disturbances. The average frequency nadir falls to 49.7 \Hz, and the average time to nadir is about 8.7 s. If wind turbines were to be requested to provide inertia support to the system, these four metrics indicate how often, how fast, for how much and for how long the wind turbines should act. Moreover, during daily normal operations, the system has in general longer duration of over-frequency (f > 50.1 Hz) than under-frequency (f
  •  
42.
  • Persson, Mattias, 1984, et al. (author)
  • Frequency Support by Wind Farms in Islanded Power Systems with High Wind Power Penetration
  • 2013
  • In: IEEE POWERTECH 2013. - 9781467356695 ; , s. Art. no. 6652361)-
  • Conference paper (peer-reviewed)abstract
    • The purpose of this paper is to investigate the frequency support in low inertia systems that could be provided by a wind farm during load mismatch. Temporary instant inertia support and inertia emulation support are evaluated and compared. An improved control strategy is presented giving quick power delivery even during low wind speeds. The proposed model can support a loss of generation of 0.1 pu with a wind power penetration of 20 % without violating the 49 Hz limit. The paper presents this as a solution to allow wind turbines to act on frequency deviations in the fast manner before other production units has caught up and started to produce in accordance to the new power level required. The temporary frequency drop for a wind penetration of 50 % was improved from 47.33 Hz, for the uncontrolled case, to 49.10 Hz utilizing the suggested adaption of inertia support.
  •  
43.
  • Persson, Mattias, 1984, et al. (author)
  • Inertia Support During Variable Wind Conditions
  • 2016
  • In: 2016 IEEE Electrical Power and Energy Conference, EPEC 2016. - 9781509019199
  • Conference paper (peer-reviewed)abstract
    • Wind variations are important to consider while designinginertia support strategies. A model has been evaluated butthe findings should reflect issues with several control strategiesutilizing a fixed inertia support pattern.Wind variability of 0.5 m/s from second to second is observedin real wind data. However, drastic changes in wind speed canoccur within the duration of inertia support.An improved inertia control algorithm has been presentedallowing a stable delivery of inertia support from variable speedwind turbines (VSWT) subjected to realistic wind conditions. Thecontroller improves the previously presented inertia algorithmand smoothly transitions from a locked operation window toMPPT-operation.The impact of the utilized wind speed filter is described andits impact on the simulation found to be of great importance.
  •  
44.
  • Persson, Mattias, 1984, et al. (author)
  • Kinetic energy estimation in the Nordic system
  • 2018
  • In: Proceedings of the 20th Power Systems Computation Conference. - 9781910963104
  • Conference paper (peer-reviewed)abstract
    • An algorithm for estimating the kinetic energy in the Nordic power system has been presented and compared to the TSOs’ estimation based on breaker status. The average error between the TSOs’ estimate and the proposed estimate is 0.83%. Furthermore, the standard deviation between the two estimates is 13 GWs, about 7% of the system average kinetic energy. The proposed estimate manages to capture the diurnal variation of the system kinetic energy with a correlation coefficient of 0.94. The total system kinetic energy in 2015 is estimated considering a possible contribution of kinetic energy from wind turbines during a large power imbalance. Lastly, the Nordic kinetic inertia is estimated for 2025, with and without possible contributions from wind, further increasing the released kinetic energy during a n-1 contingency with 22%.
  •  
45.
  • Siano, Pierluigi, et al. (author)
  • Strategic Placement of Wind Turbines in Smart Grids
  • 2012
  • In: International Journal of Emerging Electric Power Systems. - 1553-779X. ; 13:2, s. 23-
  • Journal article (peer-reviewed)abstract
    • This paper is to propose an optimization method that searches for the optimal installed capacity of wind turbines (WTs) in smart grids from the perspectives of both WTs developers and distribution network operator (DNO). The proposed hybrid optimization method combinesthe genetic algorithm and the multi-period optimal power flow analysis. The objective of the optimization is to maximize the net present value of the profits obtained by the WTs developers as well as that of the savings obtained by the DNO from network loss reduction. A 69 bus 11kV radial distribution network is used as a case study to demonstrate the proposed algorithm, with the implementation of different active management schemes. Simulation results show that the optimal WT capacity from the perspective of DNO differs from the optimal value deemed by the WT developers. The resulting economic benefits can be used by both DNO and WT developers to justify an increase in WT installation if desired. The two contrasting schemes see either the WTs developers or DNO benefiting at the expense of the other. As such, using tradeoff analysis it may be possible to find suitable compromises.
  •  
46.
  • Sunjaq, Ahmed Marwan Mousa, 1996, et al. (author)
  • Control and Sizing of Back-to-Back Converter in Interconnected Microgrids
  • 2023
  • In: IEEE PES Innovative Smart Grid Technologies Conference Europe. - 9798350396782 ; IEEE PES Innovative Smart Grid Technologies Europe, ISGT EUROPE 2023
  • Conference paper (peer-reviewed)abstract
    • This paper aims to investigate the interconnected microgrid solution through a back-to-back (B2B) converter for providing system services to grid operators and users without resorting to energy storage systems. A case study of a hydro-powered industrial microgrid interconnected to an adjacent community microgrid is analyzed. The sizing of the B2B converter for the interconnection accounts for the peak net load reduction, voltage regulation and island operation with smooth island transition. It is found that the utilization of the B2B converter is improved by value stacking grid-connected and island operation services. Furthermore, the requirement of the MW capacity has to be slightly larger for the port of the B2B converter controlling the dc-link voltage without losing control over the dc-link voltage.
  •  
47.
  • Sunjaq, Ahmed Marwan Mousa, 1996, et al. (author)
  • Evaluation of Efficient Frequency Control Strategies in a Wind-Hydro Dominated Power System
  • 2021
  • In: IEEE Power and Energy Society General Meeting. - 1944-9925 .- 1944-9933. ; 2021-July
  • Conference paper (peer-reviewed)abstract
    • This paper aims to investigate the possibility of providing a joint service of coordinated frequency support from hydro units and wind turbines (WTs) in a low inertia power system. While WTs can arrest the initial frequency dip (IFD) by providing fast support using their converter controllers, hydro turbines are capable of mitigating the second frequency dip (SFD) resulting from the restoration phase of WTs by increasing their production accordingly. Furthermore, a recently-issued grid-code for fast frequency reserve (FFR) provision in the Nordic synchronous area (NSA) is analysed and compared with the proposed method. Results show that the proposed coordinated frequency support strategy can mitigate both the IFD and the SFD with less energy requirements compared to the grid-code characteristics.
  •  
48.
  • Sunjaq, Ahmed Marwan Mousa, 1996, et al. (author)
  • Frequency control by BESS for smooth Island transition of a hydro-powered microgrid
  • 2024
  • In: IET Smart Grid. - 2515-2947. ; 7:1, s. 63-77
  • Journal article (peer-reviewed)abstract
    • This paper develops a frequency control strategy for a battery energy storage system to facilitate the smooth island transition of a hydro-powered microgrid during unplanned grid outages. The proposed frequency control strategy uses a PI-based droop controller, where the tuning of the controller accounts for the limitations in the power response of a hydro generator and the required frequency quality of the microgrid. The effectiveness of the frequency control strategy is verified in Simulink using phasor simulations, and it is further validated in laboratory tests. The results demonstrate that the proposed PI-based droop and its tuning strategy fulfill the desired frequency quality requirement of the hydro-powered microgrid without over-dimensioning the size of the storage capacity as compared to the traditional proportional droop controller.
  •  
49.
  • Tokat, Pinar, 1988, et al. (author)
  • Development of an Analytically Described Pitch Regulator for a Wind Turbine to Be Used for Grid Disturbance Studies
  • 2013
  • In: Journal of Energy. - : Hindawi Limited. - 2314-615X. ; 2013
  • Journal article (peer-reviewed)abstract
    • In this paper, a pitch controller for a variable-speed wind turbine to be used in the high wind speed region is derived. The pitch regulator parameters are determined using analytical expressions and are compared with numerical calculations. In order to derive the pitch regulated wind turbine model, blade element momentum theory is utilized and reformulated analytically. Appropriate simplifications are made and, finally, the analytically derived pitch regulated wind turbine model is tested under grid disturbances such as voltage dips and spinning reserve provision. From this work it was found that by linearizing the blade profiles, one can analytically derive a fully functioned pitch regulator. In spite of all nonlinearities, a single pitch controller setting which is valid for the whole operation region is shown to be sufficient. This system is tested under grid disturbances and it is proven that the system is capable of operating well during a 0% remaining voltage dip and also during the voltage recovery back to the rated voltage level. Accordingly, grid codes commonly referred to can be handled with this simply derived pitch regulator. Moreover, it is shown that the derived system works well for a spinning reserve application using a 90% spinning reserve ability and still maintains a robust turbine control.
  •  
50.
  • Ullmark, Jonathan, 1993, et al. (author)
  • Frequency control and synthetic inertia in energy systems modelling
  • 2020
  • Journal article (other academic/artistic)abstract
    • This study investigates how inclusion of frequency control constraints in electricity system modelling impacts the investment and dispatch in electricity generation and storage technologies for high-VRE futures. This is done using a linear cost-minimizing investment and dispatch model using historical load, wind and solar power conditions from Spain, Ireland, Sweden and Hungary for the year 2050. With an hourly time-resolution, constraints are added to ensure that, within each hour, sufficient inertial power and reserves are available to control the frequency. Comparing the results with and without these constraints show that nearly all impact on the results is in battery investments and operation. Furthermore, it is found that reserve requirements have a higher impact on system composition and operation than inertial power requirements.
  •  
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