PUBLISHED JOURNAL ARTICLES INDEXED BY SCI, etc. by emre ozkop
IEEE Transactions on Industry Applications , 2022
This article investigates factors affecting the contributions of battery units to fault currents ... more This article investigates factors affecting the contributions of battery units to fault currents in grid-connected battery storage systems (BSSs). The work in this article is intended to examine the effects of the state-of-charge (SOC) on battery currents that are drawn due to faults. This article also examines the impacts of charger controller actions on the currents drawn from battery units to faults in grid-connected BSSs. The impacts of the SOC and charger controller on battery currents due to faults are examined for the lead-acid, lithium-ion, and nickel–cadmium battery units. Examination results show that the battery currents due to faults are directly dependent on the SOC. Moreover, these results show that actions of charger controller can support the battery terminal voltage, thus preventing the fast reduction of the SOC. The support of the battery terminal voltage helps in limiting the currents drawn from battery units during faults. The effects of the SOC and charger controller are verified using a 1-MW, 3ϕ grid-connected BSS, which has lead-acid battery units. Several faults have been created during charging and discharging operations, and at different values of SOC. Test results confirm the direct dependence of battery currents (due to faults) on the SOC. In addition, obtained results demonstrate the ability of charger controller to limit the currents drawn from battery units due to faults in different parts of a grid-connected BSS.
IEEE Transactions on Industry Applications, 2022
This article develops a survivability-based protection for three-phase induction motor drive ( 3ϕ... more This article develops a survivability-based protection for three-phase induction motor drive ( 3ϕ IMDs) systems against severe dynamic events. The developed protection is based on defining a survivability index ΓIMD , which is formulated in terms of the change in power created by a dynamic event experienced by a 3ϕ IMD. The determination of ΓIMD provides an accurate tool to detect, identify, and respond to unsurvivable dynamic events. The efficacy and validity of the survivability-based protection for 3ϕ IMDs are verified through simulation and experimental tests. These tests are conducted for 10 hp 3ϕ IMD under various types of dynamic events. Test results demonstrate the effectiveness of the survivability-based protection in responding to unsurvivable dynamic events to prevent damage to different components in a 3ϕ IMD
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2021
This article presents the implementation and performance testing of a bus-differential protection... more This article presents the implementation and performance testing of a bus-differential protection for buses, which interconnect battery storage systems (BSSs). The proposed bus-differential protection is based on employing the αβ0 components of the apparent powers flowing in all branches of the protected bus. The αβ0 components of the apparent powers are employed due to their ability to accommodate changes in the power flow direction in the branches connected to the protected bus. The apparent powers are determined using the measured voltage and currents in all branches connected to the protected bus. The proposed αβ0-based bus-differential protection is implemented and tested for internal and external faults, which are created during the charging and discharging of BSSs. Test results demonstrate the ability of the proposed αβ0-based bus-differential protection to initiate fast, accurate, and reliable responses to internal and external faults in the protected bus. Observed response features of the proposed protection are found to have minor sensitivity to the mode of operation of the BSS (charging and discharging), fault location (internal and external), and/or fault type.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2021
This article presents the development, implementation, and testing of a digital differential prot... more This article presents the development, implementation, and testing of a digital differential protection for three-phase (3φ) solid-state transformers (SSTs). The developed digital differential protection is designed to implement the ANSI 87 T protection function. The differential currents used by the developed protection are created by the dq0 components of the currents flowing in the high and low voltage sides of a 3φ SST. Internal faults are detected and identified using the energy contents of high-frequency subbands present in the dq0 differential currents. The desired high-frequency subbands are extracted using the phaselet transform that processes signals without sensitivity to nonstationary changes in their frequency and/or phases. Energy contents in the extracted high-frequency subbands allow accurate, fast, and reliable detection and identification of faults in any part of a 3φ SST. The proposed digital differential protection is implemented for performance testing using a laboratory 25-kVA 3φ SST. Performance results demonstrate accurate, fast, and reliable response to different fault and nonfault events. Furthermore, responses of the developed differential protection are found to be consistent regardless of the fault type, fault location, and/or loading level.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2021
This article presents the performance evaluation of the frame-angle-based (FAB) direct torque con... more This article presents the performance evaluation of the frame-angle-based (FAB) direct torque controller (DTC) for 3 phi induction motor drives (IMDs), which are fed by 3 phi six-pulse wavelet-modulated (WM) dc-ac power electronic converters (PECs). The tested DTC is designed to adjust the d(e)- and q(e)-axis components of the voltages (v(ds)(e) and v(qs)(e)) applied to a 3 phi IMD. The adjustments in v(ds)(e) and v(qs)(e) are created in response to changes in the load torque, command torque, drive speed, and/or system parameters. Desired adjustments in v(ds)(e) and v(qs)(e) are set by regulating the angle. of the frame created by v(ds)(e) and v(qs)(e). This frame produces reference modulating signals that are required to generate WM switching pulses for operating the 3 phi dc-ac PEC in the IMD. The complete IMD system, incorporating the FAB-DTC, is implemented for a 10-hp IMD system for performance evaluation. Tests of the FAB-DTC for the 10-hp IMD are conducted for various changes in the load torque, command torque, drive speed, and system parameters. Simulation and experimental test results demonstrate fast, accurate, reliable, and dynamic responses with minor sensitivity to variations in system parameters.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2020
This article presents and tests the performance of a digital differential protection for three-ph... more This article presents and tests the performance of a digital differential protection for three-phase (3 phi) converter transformers. The proposed digital differential protection is developed to comply with the ANSI 87T protection procedure. The presented protection is featured with fault detection based on the energy contents of the high-frequency subbands of the d-q axis components of differential currents. Desired energy contents are extracted using the phaselet transform (PHT), which can process signalswithout sensitivity to the variations in their phase shifts. Energy contents of the high-frequency subbands offer accurate, fast, and reliable detection, and identification of internal faults in any part of a 3 phi converter transformer. The d-q PHT-based digital differential protection is implemented for performance evaluation using different 3 phi converter transformers, when feeding controlled rectifier units. Performance results demonstrate accurate, fast, and reliable detection, and response to different types of fault, and nonfault events. Response features of the developed differential protection are complimented with simple implementation, reduced computations, and minor sensitivity to phase shifts, fault location, and loading levels.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2020
This article presents a method to include fault currents in the reliability analysis of motor dri... more This article presents a method to include fault currents in the reliability analysis of motor drives. The presented method is based on formulating a fault current matrix (FCM), the elements of which are values of the currents flowing in all parts of a motor drive. The FCM is processed using the principal component analysis (PCA) to determine the pattern of variations in all currents due to any failure event. The output of the PCA is used to determine the failure rates for all parts of a motor drive. Determined failure rates can provide a tool to set an adequate action (mitigation, maintenance, or shutdown) to ensure a reliable and safe operation during and post any failure events experienced by the motor drive. The validity and accuracy of the PCA-FCM method are verified by employing it in the reliability analysis of different motor drives with different ratings. Results demonstrate the advantages of including fault currents in setting adequate actions in response to possible failure events.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2020
This article develops, implements, and tests a method for selecting the locations and sizes of ba... more This article develops, implements, and tests a method for selecting the locations and sizes of battery storage systems (BSSs) for power systems with distributed power generation. The developed method is based on calculating the coherency index for each bus to determine its contribution to the frequency of the center of inertia (COI) during and post a transient event. Once the coherency index is calculated for all buses, the principle component analysis (PCA) is used to identify the buses with consistent low values of the coherency index. These buses are considered as candidate locations for BSSs. In addition, the lowest values of the coherency index are used to determine the required sizes of BSSs to be connected at the buses with low contributions to the frequency of the COI. The performance of the PCA with COI (PCA-COI) method is evaluated for the Barbados power system for various transient events. Performance results show that BSSs (selected using the proposed method) can effectively improve the frequency stability with minor sensitivity to the levels of distributed power generation, loading levels, and/or type or location of transient events.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2020
This article develops and tests a controller for residential electric water heaters (EWHs). The d... more This article develops and tests a controller for residential electric water heaters (EWHs). The developed controller is operated to maximize the energy stored in EWHs during off-peak-demand times, in order to reduce their power demands during peak-demand times. Desired control actions aim to adjust the minimum temperature settings of EWHs using the unit commitment (UC). In order to eliminate the need for a direct measurement of EWH power demands, the bus-split (BS) aggregation method is employed. The BS method is employed due to its ability to extract the power demands of an EWH from household power meter readings. The UC is formulated using the energy stored in a EWH as a cost function, which is to be maximized during the off-peak-demand time. The solution of the UC problem is obtained using the Lagrange relaxation method that can offer fast convergence and reduced computations. The BS-UC controller is implemented for performance testing using power meter readings that are collected from 150 residential households during the fall, winter, spring, and summer seasons. Test results demonstrate the ability of the BS-UC controller to provide accurate and effective control of EWHs, which are complimented by a minor sensitivity to the number controlled EWHs, hot water consumption, and seasonal variations in residential load power demands.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2020
Three-phase power transformers can have their windings configured to create local neutral points,... more Three-phase power transformers can have their windings configured to create local neutral points, which can be connected to ground. The grounding of a 3 phi power transformer is intended to limit ground currents (including fault currents) and limit ground potentials. These objectives can be translated into the resistive grounding that is usually designed based on system ratings and transformer parameters. The resistive grounding, however, can impact the flow of the harmonic components present in the exciting currents of a3 phi power transformer. As a result, undesired harmonic components are induced in primary and secondary voltages. This article presents the design and performance of a frequency-selective grounding that can achieve the objectives of grounding a 3 phi power transformer. The developed grounding is designed to provide a resistive path for low-frequency currents (faults), and to create a low impedance path for high-frequency currents (harmonics). The frequency-selective grounding is experimentally tested for a 3 phi power transformer with different primary and secondary winding configurations, different fault types, and source grounding. Test results show that the developed grounding can reduce the ground potential, harmonic distortion in primary and secondary voltages, and ground fault currents with a minimum interference with ground fault protective devices.
IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, 2019
Solid-state transformers (SSTs) have diverse designs and constructions that make them suitable fo... more Solid-state transformers (SSTs) have diverse designs and constructions that make them suitable for various industrial applications, including distributions systems. This new breed of transformers has been developed to support the typical functionalities of core-type distribution transformers, along with new functionalities, such as controlling power flows, integrating dc distribution systems, utilizing distributed generation and storage units, supporting load-side voltage/frequency control, and improving the power quality. As SSTs become candidates for distribution systems, their deployment can pose challenges for distribution systems. Such challenges include the cost, protection, size and weight, efficiency, and adequate grounding designs. This article discusses some of the challenges that face the deployment of SSTs in distribution systems. In addition, this article provides a comparison between core-type and SST transformers for applications in distribution systems. The comparison between the transformers is made in terms of their efficiency, cost, and weight. Finally, this article makes several recommendations for future works that can further facilitate the deployment of SSTs in distribution systems.
IEEE Transactions on Industry Applications, 2019
IEEE Transactions on Industrial Electronics, 2018
This paper presents the development and performance evaluation of a compact-converter-based power... more This paper presents the development and performance evaluation of a compact-converter-based power supply for plasma dielectric barrier discharge (DBD) devices. The developed power supply is designed to meet weight and size requirements for applications in aeronautical systems. Multistage and multilevel switch-mode converters are employed to construct the power supply. The multistage part of the power supply is constructed from multiple dc-dc boost converters that have their inputs fed by rechargeable batteries. The outputs of the dc-dc converters are used to feed different levels of a single phase cascaded H-bridge (CHB) multilevel dc-ac converter. The switching signals for the CHB dc-ac converter are generated to facilitate the adjustments of the magnitude and/or frequency of the output voltage. Such adjustments are set to allow manipulating the generated plasma body force. A prototype for the multistage multilevel power supply is constructed for performance evaluation using a fiberglass DBD device. Performance results show an effective generation and control of plasma body force, which can be achieved by a modular, lightweight, and compact size power supply.
IEEE Transactions on Industry Applications, 2018
This paper presents the application of the multiframe digital interconnection protection for coge... more This paper presents the application of the multiframe digital interconnection protection for cogeneration systems. The multiframe digital interconnection protection is constructed from two frequency main frames; one frame to detect islanding events and the other frame to detect faults on either side of the pointof-common-coupling (PCC). Islanding events are detected based on the wavelet packet transform high-frequency subband, which is extracted from the d-q-axis components of the instantaneous 3φ apparent powers determined at PCC. The detection of faults, on either side of PCC, is achieved by extracting the magnitudes and phases of the high-frequency contents present in PCC currents. The high-frequency contents present in PCC currents are extracted by a phaselet filter bank that is composed of six digital high-pass filters, which are designed to implement six phaselet subframes. The multiframe digital interconnection protection is experimentally tested on a 3.6 kVA cogeneration system for islanding events, different faults on both sides of PCC, and nontransient conditions. Test results demonstrate the ability of the proposed interconnection protection to initiate accurate, fast, and reliable responses to various types of transient disturbances.
IEEE Transactions on Industry Applications, 2017
This paper presents the online implementation and performance evaluation of the phaselet-based me... more This paper presents the online implementation and performance evaluation of the phaselet-based method for detecting electric faults in induction motor drives (IMDs). The online implementation of tested fault detection method is achieved using a digital signal-processing board, where the inputs are the 3φ stator currents and the output is a trip signal. The desired fault feature is extracted using six digital high-pass filters, whose coefficients have been obtained using phaselet basis functions that are generated by the biorthogonal 2.1 scaling function. The performance of the phaselet-based fault detection method is tested for two different IMDs that are fed across-the-line and through a frequency drive system, when operated at different loading levels. Experimental test results show accurate, reliable, and fast fault detection, along with negligible sensitivity to the speed, loading levels, IMD ratings, and fault type.
IEEE Transactions on Industry Applications, 2017
This paper presents the analysis and development of a new method for electric fault detection in ... more This paper presents the analysis and development of a new method for electric fault detection in induction motor drives. The proposed method is based on extracting the magnitudes and phases of the high-frequency subband (HFSB) contents present in the d - q-axis components of the stator currents (i d and i q ) in an induction motor. The desired magnitudes and phases are extracted by processing id and iq using phaselet frames that are realized by a modulated filter bank. This filter bank is designed using six digital high-pass filters, whose coefficients are determined by biorthogonal phaselet basis functions. Extracted HFSB contents provide signature information that can offer accurate and fast detection of faults. The phaselet-based electric fault detection method has been made into a procedure for digital implementation. The performance of the proposed method is evaluated offline for collected stator currents from two different induction motor drives under different operating conditions. Offline test results show accurate, reliable, and fast detection of electric faults, with minor sensitivity to the ratings, loading levels, and type and location of faults.
IEEE Transactions on Power Electronics, 2017
This paper presents the implementation and performance evaluation of a coordinated antiislanding ... more This paper presents the implementation and performance evaluation of a coordinated antiislanding protection for systems with multiple distributed generation units (DGUs). The proposed coordinated antiislanding protection is structured to process the d - q-axis components of the instantaneous three phase apparent powers (sd and sq) determined at the point-of-common coupling for each DGU. The processing of sd and sq, for each DGU, is carried out by the wavelet packet transform (WPT) in order to extract their low-and high-frequency subband contents. The contents of WPT low-and high-frequency subbands offer signature information that can facilitate detecting the islanding condition and identifying the islanded DGU(s). The coordinated antiislanding protection is implemented in real time for experimental testing on a laboratory collector system that has three different DGUs. Experimental results reveal fast and accurate responses to islanding events, accurate identification of islanded DGUs, and negligible sensitivity to the type or ratings of protected DGUs. In addition, test results show that the d - q WPT-based coordinated antiislanding protection can accurately distinguish between islanding and nonislanding events, including faults, step changes in power delivery to the grid, unintentional loss of grid connection, low-voltage ride through, and sudden harmonic distortion on the grid side.
Renewable and Sustainable Energy Reviews, 2017
The purpose of this paper is to introduce the status of wave energy conversion (WEC) technologies... more The purpose of this paper is to introduce the status of wave energy conversion (WEC) technologies from a different perspective. Past studies based on WEC systems are summarized and classified in terms of WEC system components to clearly reveal the performance, efficiency and development of WEC technologies over the last two decades. It has been proved that the individual components of a WEC system, such as types of wave energy converter and generator motion, control methods and power electronic converter, have a close relationship with each other and that no single component can be optimized without considering the others. It can be helpful to divide into descriptive parts to provide a better understanding of the development process for WEC technologies so that studies based on WEC technologies are discussed by regarding types of wave energy converters, generators, control methods, controller applied sides, waves, power electronic converters and validations and publication year in this paper.
IEEE Transactions on Industry Applications, Jul 27, 2016
This paper presents a coordinated anti-islanding protection for collector systems with multiple d... more This paper presents a coordinated anti-islanding protection for collector systems with multiple distributed generation units (DGUs). The presented anti-islanding protection is established based on processing the d-q-axis components of the instantaneous three phase apparent powers (s d and sq) determined at the point-of-common-coupling using the wavelet packet transform (WPT). Processing s d and sq by using WPT allows the extraction of lowand high-frequency sub-band contents. The contents of the high-frequency sub-band are used to detect and distinguish islanding events, and contents of the lowand high-frequency subbands are employed to define a coordination index, which is used to identify the islanded DGU(s). The presented anti-islanding protection is implemented for off-line testing using data obtained from a laboratory collector with four different DGUs. Off-line test results demonstrate accurate, fast, and reliable responses to islanding and nonislanding event(s), and accurate identification of islanded DGUs along with negligible sensitivity to levels of power delivery to the collector system.
INTERNATIONAL JOURNAL OF ENGINEERING EDUCATION, 2016
The design and implementation of a Virtual Electric Power Transmission Line Lab for undergraduate... more The design and implementation of a Virtual Electric Power Transmission Line Lab for undergraduate curricula is introduced in this paper. The aim of the virtual laboratory is to enhance learning and teach students the basis and characteristics of the power transmission line model under different conditions in a virtual interface before entering the field. The user can realize various tests, such as short circuit, no-load, load and fault tests, to develop an understanding of the model behaviors, effects of changes in the model parameters, load and connections. The proposed Virtual Electric Power Transmission Line Lab is developed in the Matlab graphical user interface (GUI) environment. The proposed virtual lab has been implemented in the Power Systems Lab taught at the Department of Electrical and Electronics Engineering at Karadeniz Technical University as part of the undergraduate curriculum. A survey of the students who took the lab course has been conducted, and the responses are included in this paper.
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PUBLISHED JOURNAL ARTICLES INDEXED BY SCI, etc. by emre ozkop
Bu çalışmada, geçmişten günümüze elektrikli araç ve bisiklet hakkında bilgiler verilmektedir.
Şebeke bağlantısız tek fazlı transformatörsüz H6-II tipi eviricide SDGM tekniğinin kullanımının çıkıştaki yük akımında oluşan THB'nin iyileştirilmesinde pozitif etkisi olduğu ve yük akımı THB değerinin IEEE Std. 1547-2018 standardında belirtilenden daha küçük olduğu ve ayrıca tek fazlı sistemden ÜHEDGM tekniğini uygulanması ile çıkış gerilim dalga şekilde üçüncü harmonik bileşeni yok edemediği ve dalga şeklini sinüsoidal biçimden uzaklaştırdığı, buna rağmen çıkış geriliminin genliğini SDGM tekniği kullan H6-II tipi eviriciye göre daha da büyüttüğü tespit edilmiştir.
transformatörsüz H5 evirici topolojisine sahip sistemin benzetim performansını sunmaktadır. H5 evirici yapısı şebekeye daha kayıpsız ve güvenli güç akışı sağlamaktadır. Sistem denetimi, H5 evirici için referans gerilim dalga şeklinin elde edilmesi ve şebekeye aktarılacak akım miktarının belirlenmesi için kullanılan şebeke AA akımı ve DA giriş gerilimi içeren kaskad PI denetleyici yapısı ile gerçekleştirilmektedir. Sistem benzetim çalışması Matlab/Simulink ortamında gerçekleştirilmiş olup sistemin performansı; evirici çıkış gerilimi, şebeke akımı ve gerilimi, aktif ve reaktif güçler ve harmonik bozulma yönünden değerlendirilmektedir.