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  • 1.
    Bollen, Math H J
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah K
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Schwanz, Daphne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Eirgrid, Dublin, Ireland.
    Nakhodchi, Naser
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Harmonics and Wind Power Installations2021In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution, IEEE, 2021, p. 648-652, article id 0028Conference paper (Refereed)
  • 2.
    Busatto, Tatiano
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Estimation of the Consumer Electronics Capacitance for Harmonic Resonance Studies by a Non-Invasive Measurement Method2018In: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018, , p. 6Conference paper (Refereed)
    Abstract [en]

    Harmonic resonances in distribution systems are mainly between network inductances and shunt capacitances from capacitor banks and consumer loads. In this paper, particular attention is devoted to the evaluation of capacitances from domestic equipment, serving as a reference for resonance frequency studies. The assessment is performed by simulation and measurements of common low power electronic loads. From the analysis of EMI filters topologies used in AC/DC converters, a non-invasive capacitance measurement estimation method is presented. The method is verified after correlating capacitances with the resonance frequencies obtained from a frequency sweep method. From experimental measurements, the results show that the equivalent shunt capacitances for a set of 24 LED lamps are between 10 and 135 nF.

  • 3.
    Busatto, Tatiano
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Measurements on an experimental laboratory setup with PV Inverters and a Large Number of LED Lamps2018Report (Other academic)
  • 4.
    Busatto, Tatiano
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math H. J.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Meyer, Jan
    Institute of Electrical Power Systems and High Voltage Engineering, Technische Universität Dresden, Dresden, Germany.
    Experimental Harmonic Analysis of the Impact of LED Lamps on PV Inverters Performance2019In: 2019 Electric Power Quality and Supply Reliability Conference (PQ) & 2019 Symposium on Electrical Engineering and Mechatronics (SEEM), IEEE, 2019Conference paper (Refereed)
    Abstract [en]

    It is known for instance that voltage waveform distortion and network impedance have a significant impact on PV inverter current emissions. Because this, much research is still required to better understand their behavior and impact when multiple common household devices are placed to operate together in the same low-voltage installation. In particular, this paper addresses the harmonic impact of LED lamps on PV inverters performance considering different technologies and number of lamps. The analysis has been carried out with different scenarios considering two types of LED lamps, with and without power factor correction feature, and three different PV inverter technologies. The evaluation of the impacts is simply performed by frequency and time domain analysis, establishing the correlation between the devices current harmonics. The results obtained from the experiments have shown that LED lamps are prone to add a significant impact on the PV inverter current harmonics, and this impact is mainly dependent on the devices used technology.

  • 5.
    Busatto, Tatiano
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Meyer, Jan
    Electric Power Engineering, Technische Universität Dresden.
    Deviations between the commonly-used model and measurements of harmonic distortion in low-voltage installations2020In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 180, article id 106166Article in journal (Refereed)
    Abstract [en]

    Harmonic analysis studies of modern power systems commonly employ Norton and Thévenin equivalents at harmonic frequencies for the nonlinear devices. This approach neglects the so-called nonlinear interaction phenomenon. This paper addresses the difference between the results from the commonly-used model and the actual harmonic distortion measured in a low-voltage installation. A number of indices are introduced to quantify the nonlinear interaction. These indices allow a quantification of the extent to which the commonly-used model is also to predict harmonic voltages and currents in a modern low-voltage installation. The proposed model and the subsequent mathematical analysis are illustrated through measurements from different combinations of PV inverters and LED lamps using different technologies. The results show that deviation is dependent on the used technology, network impedance, and source voltage waveform. Other findings are that nonlinear interaction happens mainly in the low harmonic orders and impacts are more perceived on the harmonics phase angle. Possible explanations for these observations are discussed.

  • 6.
    de Oliveira, Roger Alves
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Deep Learning For Pattern Recognition Of Interharmonics In Time-Series And Spectrograms2021In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution, 2021, p. 738-741Conference paper (Refereed)
    Abstract [en]

    This work applies an unsupervised deep feature learning to finding patterns of interharmonics. The main objectives of this work are to provide an additional graphical tool to handle two distinct data inputs: (a) individual interharmonics components in time-series; (b) broadband spectrum by employing spectrograms. Both data inputs are analysed employing an autoencoder based on convolutional neural networks followed by clustering. The application of the method results in the most common patterns in time-series or spectrograms. Two study cases are presented by applying the method to measurements from solar installations in Finland and Sweden. The results show the usefulness of the method to recognize interharmonics in a single frequency and broadband spectrum.

  • 7.
    de Oliveira, Roger Alves
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah K.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math H.J.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Deep Learning Method With Manual Post-Processing for Identification of Spectral Patterns of Waveform Distortion in PV Installations2021In: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 12, no 6, p. 5444-5456Article in journal (Refereed)
    Abstract [en]

    This paper proposes a deep learning (DL) method for the identification of spectral patterns of timevarying waveform distortion in photovoltaic (PV) installations. The PQ big data with information on harmonic and/or interharmonics in PV installations is handled by a deep autoencoder followed by feature clustering. Measurements of voltage and current from four distinct PV installations are used to illustrate the method. This paper shows that the DL method can be used as a starting point for further data analysis. The main contributions of the paper include: (a) providing a novel DL method for finding patterns in spectra; (b) guiding the manual post-processing based on the patterns found by the DL method; and (c) obtaining information about the emission from four PV installations.

  • 8.
    Espin Delgado, Angela
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Summation law for supraharmonic currents (2–150 kHz) in low-voltage installations2020In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 184, article id 106325Article in journal (Refereed)
    Abstract [en]

    The development of methods to study the propagation of supraharmonics in LV and even MV grids is a current research topic among the power quality community, which has been motivated by the efforts to establish limits for non-intentional supraharmonic emissions and planning levels. The assessment of how much distortion a bulk use of power electronics devices can inject into the grid is necessary before stating emission limits and planning levels for supraharmonics. To address this issue, the development of suitable models that can predict the supraharmonic emission from a low-voltage installation as a whole is required. This article presents a comparison of models for the summation of supraharmonics. An improved model for the summation of supraharmonics is proposed, which is validated experimentally. It is shown that by using the proposed model, predictions of supraharmonic propagation can be accomplished. Furthermore, it is demonstrated experimentally that, with the increasing number of supraharmonic emitting devices, the supraharmonic current distortion injected into a grid by an installation increases up to a maximum value and then decreases due to the capacitive nature of power electronics appliances existing in low-voltage networks.

  • 9.
    Espín-Delgado, Angela
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah K.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Meyer, Jan
    Power Quality Research Group, Technische Universität Dresden, Dresden, Germany .
    Evaluation of Supraharmonic Propagation in LV Networks Based on the Impedance Changes Created by Household Devices2020In: Proceedings of 2020 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe) 26-28 October, 2020, IEEE, 2020, p. 754-758Conference paper (Refereed)
    Abstract [en]

    This paper investigates the characteristics of emission in the frequency range 2-150 kHz (supraharmonics) in time and frequency domain and how it propagates under different scenarios posed by the customer connections and changes in the grid. The analysis is based on measurements performed in a low-voltage installation, considering the simultaneous operation of a set of PV inverters and LED lamps in order to create changes in both impedance and emissions. The results confirm that supraharmonics tend to interact with nearby devices in the customer installation. As the number and constellation of emitting devices change so does the propagation of the supraharmonics. The propagation towards the grid can either increase or decrease with the increasing number of connected devices depending on the ratio between the impedances of the device and the grid impedance. Devices’ technology plays an important role in defining supraharmonic characteristics, emission levels and propagation. Finally, a qualitative analysis of the individual devices’ impedance and discussion of some of the practical aspects is provided.

  • 10.
    Löfgren, Isabelle
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Energy Engineering, Dalarna University, Falun, Sweden.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Interharmonics under Fundamental Frequency Variations2021In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution, IEEE, 2021, p. 658-662, article id 0048Conference paper (Refereed)
  • 11.
    Nakhodchi, Naser
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Application of Transfer Function Method in a Wind Park for Harmonic Study2021In: CIRED 2021 - The 26th International Conference and Exhibition on Electricity Distribution, Institution of Engineering and Technology , 2021, p. 723-727, article id 0135Conference paper (Refereed)
    Abstract [en]

    Harmonic emission from a wind park to the grid and the interaction between individual turbines within a wind park are among the power quality challenges that have been studied for many years, as part of the connection of wind parks to the grid. Different methods are proposed and various simulation models are developed under some assumptions. This paper presents the results from a transfer function based model for an existing wind park, and investigates the impact of LV load modelling (residential customers) and MV cable capacitance on the interaction between turbines and between turbines and the grid. It is shown that LV loads and MV cable capacitance can have significant impact on the interactions between turbines and grid while it has only limited impact on interactions between turbines.

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  • 12.
    Ravindran, Vineetha
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Time-varying Waveform Distortion in Low voltage network2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The progressive advancement in new technologies has introduced new types of equipment into the grid. Some of these devices, which have gained significant popularity in the last few decades are photovoltaic (PV) systems and wind power systems from the generation side, and energy-efficient lighting i.e. LED lamps and energy-efficient transportation via electric vehicles from the consumption side. All these equipment essentially consist of different kinds of power electronic converters with their associated control systems. There is always feasibility of mutual interactions between these non-linear power electronic devices with the grid as well as with other grid-connected equipment placed electrically close to each other, where the control loops can face new system dynamics. Adverse interactions can cause interferences and in the worst-case lead to instability issues. A mapping of the potential interactions, in the form of emission is needed to understand interferences at the device level and system level. The overall aim of this work is to enhance the existing knowledge about the power quality aspects of the different non-linear power electronic devices that are being increasingly connected to the grid especially in low voltage networks. The conclusions derived from this study can be extended to a broader scale where there is the feasibility of multiple non-linear power electronic-based devices operating together at medium and high voltage levels.

    The main contributions of the work are classified into three main parts: 

    In the first part, an in-depth study of interharmonics in PV systems is carried out. Different sets of field measurements and measurements from controlled but realistic laboratory environments are investigated for interharmonic existence, persistence, and propagation. To ensure the genuinity of the observed interharmonics and to address the different challenges associated with their estimation, combinations of methods are applied and results compared. The possible reasons for their origin are systematically established through a comprehensive study. The potential system impacts which it could create in the grid and to other grid-connected equipment are investigated. The possibility for aggregation of interharmonics when multiple sources are connected to the same point of common coupling is explored via a statistical approach.

    In the second part, initially harmonic interactions in wind parks, and between PV and LED lamps, are first discussed. The time-varying harmonic interaction phenomenon is studied in detail with the help of a mathematical model as well as with the help of analysis of field measurements at multiple locations of a wind park. The outcome of this study contributes to the yet challenging problem of harmonic contribution estimation in twofold. (a) A method is developed from long-term field measurements with which one could potentially identify which source of emission dominates in the analysis period, and (b) Limitations of the extended mathematical model are identified and inferences from field measurements are linked to further improve the mathematical model. Further, some specific cases of harmonic interactions between PV and LED lamps are illustrated. These examples could be a guidance for power electronic designers to increase individual device immunity subjected to harmonic interferences.

    Additionally in the same part, the impact of PV induced voltage variations on different topologies of LED lamps are investigated. The considered voltage variations are distinguished as overvoltage, undervoltage, rapid voltage changes, and voltage steps due to fast-moving cloud transients, due to inverter operation itself, and due to voltage regulations caused by load tap changing operations of distribution transformers. Due to PV induced voltage variations, LED lamps are impacted in various ways. LED lamps are either potential victims of these voltage variations or LED lamps to act as sources of increased grid distortions. As potential victims, the studied LED lamps have shown changes in the light output, instability issues, and degradation in the driver efficiency. As potential sources of grid distortion, LED lamps have exhibited increased harmonic and interharmonic emissions. The difference in impact has been linked to the topology of the lamps.

    In the third part, the application of a deep leaning based unsupervised machine learning method to extract waveform distortion patterns in big data for enhancing power quality knowledge is illustrated. Specifically, signal processing of interharmonics with precise frequency and amplitude estimation needs the processing of data of large volume for a higher resolution. Thus, the interharmonics analysis in long-term measurements evidences the need for an automatic tool to assist the experts. In this work, a deep learning method for the identification of spectral patterns of time-varying waveform distortion in photovoltaic installations is proposed. The PQ big data with information on harmonic and/or interharmonics in PV installations is handled by a deep autoencoder followed by feature clustering. Measurements of voltage and current from four distinct PV installations are used to illustrate the method. The proposed method accelerates the process of manual interpretation and is a starting point to determine how to proceed further with the data analysis.

    Download full text (pdf)
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  • 13.
    Ravindran, Vineetha
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Comparison of a non-parametric and parametric method for interharmonic estimation in PV systems2019In: 2019 IEEE Milan PowerTech, IEEE, 2019Conference paper (Refereed)
    Abstract [en]

    A comparative analysis of ‘Desynchronized processing technique’ (non-parametric) and ‘Sliding window ESPRIT method’ (parametric) for interharmonic estimation in PV systems is carried out. Both methods were applied to field measurements and semi-measured signals to test their feasibility under different conditions. In Desynchronized processing technique, in the second stage of estimation, a Short-term Fourier transform was used to address the time-varying nature of interharmonics. In Sliding window ESPRIT method, the signal subspace dimension was fixed in all analysed cases. An adaptive algorithm was used to find the best rank of the Hankel matrix and apt order of the filter to ensure stability. A set of critical parameters affecting the performance of these methods in interharmonic estimation are identified. This paper emphasizes the significance of using appropriate methods for accurate interharmonic estimation and also demonstrates through the illustrated results that different inferences can be drawn for the same measurements analysed using different methods.

  • 14.
    Ravindran, Vineetha
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Meyer, Jan
    Technische Universität Dresden, Germany.
    Characterization of interactions between PV systems and energy efficient lighting (LED)2019In: CIRED 2019 Proceedings, AIM , 2019, Vol. -, article id 237Conference paper (Refereed)
    Abstract [en]

    The possible interactions between grid-tied power-electronic based PV systems and energy efficient LED lighting systems in terms of current and voltage, for different combinations of the inverter and LED lamp types under different grid conditions, are studied in a laboratory environment. In this paper, the interactions are characterized in terms of the power quality disturbances like harmonics, interharmonics, supraharmonics, overvoltage, undervoltage, and rapid voltage changes.

  • 15.
    Ravindran, Vineetha
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah K.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Meyer, Jan
    Technische Universitaet Dresden, Dresden, Germany.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Time-Varying Interharmonics in Different Types of Grid-Tied PV Inverter Systems2020In: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208, Vol. 35, no 2, p. 483-496Article in journal (Refereed)
    Abstract [en]

    Widely existing circuit topologies and inverter control strategies for photovoltaic (PV) systems allow customer flexibility but also introduce different kinds of interharmonics into the grid. A complete understanding of interharmonics from PV systems, with reasons behind their origin, remains needed. In addition, the time-varying nature of interharmonics and the potential impacts on other equipment are yet to be understood. In this paper, laboratory and field measurements of seven different inverter types at multiple locations are presented. A comprehensive analysis is performed to understand the existence, persistence, and propagation of interharmonics in PV systems on the dc side as well as grid side for different power levels. The origins of the interharmonics are established with experimental evidence and through a comparative analysis. A rural low voltage six customer network, with two different impedance profiles caused by the installation of PV, is considered to show the potential impact on customer voltage. To address the time-varying nature of interharmonics, a sliding window ESPRIT method is preferred over fast fourier transform (FFT)-based methods.

  • 16.
    Ravindran, Vineetha
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Nakhodchi, Naser
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math H. J.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Assessing time-varying harmonic interactions in a wind park2021In: IEEE Access, E-ISSN 2169-3536, Vol. 9, p. 68151-68160Article in journal (Refereed)
    Abstract [en]

    The harmonic interaction mechanism in a wind park is examined in this paper. The paper investigates the feasibility of a solution to the yet challenging harmonic contribution estimation from multiple sources in a wind park with limited available information, via an extension of a simple modeling approach as well as from detailed analysis of field measurements. The paper has two distinct objectives in assessing harmonic interactions (a) one to extend the classical Norton equivalent model to a multi-measurement wind park system and to suggest potential areas for further model developments from field measurement analysis, and (b) second to draw inferences from field measurements and to develop a new independent concept of analysis from long-term field measurements in the wind park. From practical experience, a new concept of analysis with a ‘harmonic interaction break-even point’ is introduced. With the help of it, one could identify whether the primary emission (emission from considered source) or secondary emission (emission from a distant source) dominates in the analysis period. In this way, the highest responsibility between different interacting time-varying harmonic sources is evaluated. It was concluded that from long-term measurements one can define a magnitude of power production where a certain harmonic order is canceled or reaches its lowest magnitude. If one finds this cancellation point, one can define a level of secondary/primary emission or at least a feasible range. This knowledge is a step forward towards harmonic contribution analysis.

  • 17.
    Ravindran, Vineetha
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Interharmonics in PV systems: A Review of analysis and estimation methods; considerations for selection of an apt method2019In: IET Renewable Power Generation, ISSN 1752-1416, E-ISSN 1752-1424, Vol. 13, no 12, p. 2023-2032Article, review/survey (Refereed)
    Abstract [en]

    A comprehensive reviewing of existing interharmonic analysis and estimation methodologies irrespective of application is carried out. The paper is enlisting the characteristics of an appropriate method to analyse and estimate interharmonics in PV systems, and linking these characteristics with the features of the reviewed methodologies. The distinctive characteristics of interharmonic emissions related to PV systems are therefore presented. The various methodologies are classified, summarized, and a checklist is prepared to emphasize the areas to be paid attention to while establishing an apt method for interharmonic analysis in PV systems. The priorities for selection of a method by a practicing engineer vary case by case. This paper will serve as a guideline for selection and further development of a suitable method for interharmonic analysis in a PV included power system.

  • 18.
    Ravindran, Vineetha
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Inspection of Interharmonic emissions from a Grid-tied PV Inverter in North Sweden2018In: Proceedings of International Conference on Harmonics and Quality of Power, ICHQP, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2018Conference paper (Refereed)
    Abstract [en]

    The main objective of the paper is to investigate theexistence of interharmonic emissions from an MPPT drivengrid-connected PV inverter, identify their severity andpersistence. The presence of interharmonics in the measuredcurrent from a PV installation is linked to direct and diffusedsolar irradiation as well as a high ramping rate of theirradiation causing variations in both active and reactive power.The paper sets forth a set of observations and inferences, whichis an appendage to the ongoing research on the power qualityaspects of solar power. Three different case studies areevaluated in detail using signal processing tools like STFT andFFT.

  • 19.
    Ravindran, Vineetha
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Sakar, Selcuk
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Characterization of the impact of PV and EV induced voltage variations on LED lamps in a low voltage installation2020In: Electric power systems research, ISSN 0378-7796, E-ISSN 1873-2046, Vol. 185, article id 106352Article in journal (Refereed)
    Abstract [en]

    Photovoltaic (PV) systems, Electric vehicles (EV) and LED lamps have gained significant popularity in our current society. It is therefore common to find customer installations with all three operating together. PV and EV are known sources of voltage variations on the grid. The impact of these voltage variations on LED lamps situated in close proximity to PV or EV in a low voltage installation, in terms of overvoltage, undervoltage, and rapid voltage changes is systematically studied in a laboratory environment in this paper. Such variations can cause malfunctioning of the lamp based on its immunity and tolerance level or be disturbing to the end-user based on the intensity of variations and rate of recurrence of being subjected to such variations. In this work, the observed impacts on LED lamps are illustrated as 15 different cases. The scope of this work is to identify the possible impacts due to voltage variations induced by PV and EV systems on LED lamps and the potential problems that could happen long term due to recurrent subjection of such voltage variations.

  • 20.
    Ravindran, Vineetha
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Sudha Letha, Shimi
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Rönnberg, Sarah
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Time domain aggregation of interharmonics from parallel operation of multiple sourcesIn: IEEE Transactions on Power Delivery, ISSN 0885-8977, E-ISSN 1937-4208Article in journal (Refereed)
    Abstract [en]

    A model to analyze the probability distribution of the peak value of the interharmonics aggregating at the point of common connection is developed. With multiple sources of interharmonics, the fluctuations in the peak value of voltage or current matters. It is shown by virtue of Monte Carlo Simulations that the distribution of aggregated interharmonic peak value follows either a Gumbel distribution with random number of interharmonics or a normal distribution with constant number of interharmonics. Approximate mathematical expressions are formulated from the estimated parameters of the probability distribution functions to predict the highest probability of 95 percentile peak value occurence. The results from the model are verified using real data from a PV installation and a wind park with multiple converters. The significance of probabistic studies to understand the extremities due to interharmonic aggregation and also the analysis in time domain for evaluation of instantaneous aggregated peak value is emphasized in this paper

  • 21.
    Sudha Letha, Shimi
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Electrical Engineering Department, Punjab Engineering College (Deemed-to-be University), Chandigarh, 160012, India.
    Bollen, Math H. J.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Busatto, Tatiano
    Espin Delgado, Angela
    Mulenga, Enock
    Bakhtiari, Hamed
    Sutaria, Jil
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, Skellefteå, 97187, Sweden.
    Ahmed, Kazi Main Uddin
    Nakhodchi, Naser
    Sakar, Selçuk
    Ravindran, Vineetha
    Power Quality Issues of Electro-Mobility on Distribution Network—An Overview2023In: Energies, E-ISSN 1996-1073, Vol. 16, no 13, article id 4850Article, review/survey (Refereed)
    Abstract [en]

    The journey towards sustainable transportation has significantly increased the grid penetration of electric vehicles (EV) around the world. The connection of EVs to the power grid poses a series of new challenges for network operators, such as network loading, voltage profile perturbation, voltage unbalance, and other power quality issues. This paper presents a coalescence of knowledge on the impact that electro-mobility can impose on the grid, and identifies gaps for further research. Further, the study investigates the impact of electric vehicle charging on the medium-voltage network and low-voltage distribution network, keeping in mind the role of network operators, utilities, and customers. From this, the impacts, challenges, and recommendations are summarized. This paper will be a valuable resource to research entities, industry professionals, and network operators, as a ready reference of all possible power quality challenges posed by electro-mobility on the distribution network.

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