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Research Publications (Engineering and Built Environment)

Permanent URI for this collectionhttp://ir-dev.dut.ac.za/handle/10321/215

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Author: search.filters.author.Buraimoh, ElutunjiHas files: Yes

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    Performance evaluation of percentage differential relays on power transformer and reliability assesment in HVDC grid protection scheme
    (IEEE, 2022-08-22) Ngema, Philani; Davidson, Innocent Ewaen; Buraimoh, Elutunji
    Percentage differential relays remain the most sensitive protection tool applied as backup protection on power transformers, busbar, and generators. Relays sometimes do mis-operate with the current transformer being affected by external fault leading to saturation, and the subsidence current present after clearing external faults. The cause of misoperation of percentage differential relays cannot be ignored that it entirely depends on magnitudes more than directionality for tripping decisions. This paper covers evaluating differential element performance, analysis of transformer inrush current, internal faults, external faults, and overexcitation conditions. The accurate computing of current transformers is also included. This protection only applies to 10MVA and above on transformers; however, it is not limited to transformers, but also transmission lines, busbars, and generators. The balance of the paper is on reliability assessment based on the HVDC grid protection scheme operation
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    Contactless palmprint recognition system : a survey
    (Institute of Electrical and Electronics Engineers (IEEE), 2022) Alausa, Dele W.S.; Adetiba, Emmanuel; Badejo, Joke A.; Davidson, Innocent E.; Obiyemi, Obiseye; Buraimoh, Elutunji; Abayomi, Abdultaofeek; Oshin, Oluwadamilola
    T Information systems in organizations traditionally require users to remember their secret pins (password), token, card number, or both to confirm their identities. However, the technological trend has been moving towards personal identification based on individual behavioural attributes (such as gaits, signature, and voice) or physiological (such as palmprint, fingerprint, face, iris, or ear). These attributes (biometrics) offer many advantages over knowledge and possession-based approaches. For example, palmprint images have rich, unique features for reliable human identification, and it has received significant attention due to their stability, reliability, uniqueness, and non-intrusiveness. This paper provides an overview and evaluation of contactless palmprint recognition system, the state-of-the-art performance of existing works, different types of "Region of Interest" (ROI) extraction algorithms, feature extraction, and matching algorithms. Finally, the findings obtained are presented and discussed
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    Advanced distributed cooperative secondary control of Islanded DC Microgrids
    (MDPI AG, 2022-05-28) Aluko, Anuoluwapo; Buraimoh, Elutunji; Oni, Oluwafemi Emmanuel; Davidson, Innocent Ewean
    In an islanded DC microgrid with multiple distributed generators (DGs), the droop control is employed to realize proportional current sharing among the DGs in the microgrid. The action of the droop control causes a deviation in the DC bus voltage which is exacerbated by the line impedance between the DG and the DC bus. In this paper, an advanced distributed secondary control scheme is proposed to simultaneously achieve accurate voltage regulation and cooperative current sharing in the islanded DC microgrid system. The proposed distributed secondary controller is introduced in the cyber layer of the system, and each controller shares information with neighbouring controllers via a communication network. The distributed technique maintains the reliability of the overall system if some part of the communication link fails. The proposed controller uses the type-II fuzzy logic scheme to adaptively select the secondary control parameters for an improved response of the controller. The sufficient conditions to guarantee the stability of the proposed controller are derived using the Lyapunov method. Comprehensive tests under different operating scenarios are conducted to demonstrate the robustness of the proposed control scheme.
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    Enhancing the performance of Eskom’s Cahora Bassa HVDC Scheme and Harmonic Distortion Minimization of LCC-HVDC Scheme using the VSC-HVDC link
    (MDPI AG, 2022-04-20) Davidson, Innocent Ewean; Oni, Oluwafemi Emmanuel; Aluko, Anuoluwapo; Buraimoh, Elutunji
    Cahora Bassa, a thyristor-based High Voltage Direct (HVDC) link, transmits 1920 MW of power from a hydro-power plant in Zambezi River, north of Mozambique, to Apollo Substation in Johannesburg, South Africa. The high degree of harmonics distortion that is transferred into the AC side of the transmission network and the continuous increase in the rate at which commutation failure occurs during systems disturbance are both flaws in the utilization of this HVDC converter technology. AC and DC filters with rugged controllers are often used to minimize this effect but are limited in scope. Modern converter technology, such as the Voltage Source Converter (VSC), was proposed in this study to reduce harmonics content level, increase power transfer capabilities, enhance network stability, and reduce the rate of commutation failure occurrence. This paper, therefore, evaluates the performance analysis of the Cahora Bassa HVDC link and its level of harmonic distortion in the line commutated converters. A proposed method of utilizing VSC HVDC is provided as a suitable solution using three modular-level voltage source converter technology. Current and voltage waveform characteristics during a three-phase short circuits fault were analyzed, and the latest developments in the area of VSC HVDC were discussed. The results show a lower total harmonics distortion with the usage of VSC HVDC converter technology at the inverter station. The continuous occurrence of commutation failure was minimized by implementing a new converter architecture. The network simulation and analysis were carried out using the DIgSILENT PowerFactory engineering software tool.
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    Modeling of double stage photovoltaic inverter system with fast delayed signal cancellation for fault ride-through control application in microgrids
    (MDPI AG, 2022-02) Buraimoh, Elutunji; Davidson, Innocent E.
    This research presents a secondary control for a grid-supporting microgrid with photovoltaics sources to guarantee grid code compliance and ancillary services. The secondary control accomplishes the fault ride-through, which implements a delayed signal cancellation (DSC) algorithm for negative sequence detection. Without mode switching, the proposed control strategy meets grid code requirements and ensures voltage regulation at the secondary level, which is active and more salient throughout the transient period of host grid disturbances. This control also ensures a constant supply of the microgrid’s sensitive local load while adhering to grid code requirements. Similarly, active power injection into the main grid is limited by progressively altering the MPPT operating point dependent on the depth of voltage sag to optimize reactive power injection to sustain grid voltage sag. The recommended secondary control is triggered by utilizing the DSC process’s detection algorithm to identify the occurrence of a fault in a tiny fraction of a half-cycle in a grid fault. Consequently, while satisfying microgrid load needs, the devised technique guaranteed that increases in DC-link voltage and AC grid current were controlled. MATLAB Simscape ElectricalTM and OPAL-RT Lab are used to do time-domain simulations of the model using the recommended secondary control systems.
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    A new technique for improvement differential relay performance in power transformers
    (IEEE, 2022-01-25) Ngema, Philani; Buraimoh, Elutunji; Davidson, Innocent
    Transformer protection devices are often used to identify internal or external transformer problems and act to either prevent damage or unnecessarily disconnect power transformers. This study proposes a new differential element that combines harmonic restraint, security, and reliability with harmonic blocking speed to improve the relay performance in a power transformer. Under high load, a negative-sequence differential element adds more sensitivity for internal turn-to-turn failures. External fault detection monitoring enhances security in an external problem involving current transformer (CT) saturation. Furthermore, overcurrent elements may be configured to vary dynamically in operation is provided. This element enhances protection coordination for various operating conditions without requiring modifications to the transformer group settings. The balance of the paper discusses the use of an under-load tap changer using a time-synchronized phasor monitoring system to reduce loop current and losses in parallel transformer applications.
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    Decentralized fast delayed signal cancelation secondary control for low voltage ride-through application in grid supporting grid feeding microgrid
    (Frontiers Media SA, 2021-04-15) Buraimoh, Elutunji; Davidson, Innocent E.; Martinez-Rodrigo, Fernando
    In this study, a distributed secondary control is proposed alongside the conventional primary control to form a hierarchical control scheme for the Low Voltage Ride-Through (LVRT) control and applications in the inverter-based microgrid. The secondary control utilizes a fast Delayed Signal Cancelation (DSC) algorithm for the secondary control loop to control the reactive and active power reference by controlling the sequences generated. The microgrid consists of four Distributed Energy Resources (DER) sources interfaced to the grid through interfacing inverters coordinated by droop for effective power-sharing according to capacities. The droop also allows for grid supporting application for microgrid’s participation in frequency and voltage regulation in the main grid. The proposed decentralized fast DSC performance is evaluated with centralized secondary and traditional primary control using OPAL-RT Lab computation and MATLAB/SIMULINK graphical user interface for offline simulations and real-time digital simulator verification. This study presents and discusses the results.
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    Overview of fault ride-through requirements for photovoltaic grid integration, design and grid code compliance
    (IEEE, 2020-09-27) Buraimoh, Elutunji; Davidson, Innocent E.
    The integration of photovoltaic systems into the power grid and their dynamics through grid faults became an essential concern in grid codes' emerging requirements. Accordingly, fault ride-through of the grid-connected PV system functionality and regulation became the most critical grid codes considerations. Countries have come up with several stringent requirements for grid integration of renewable energy sources. This paper identified many FRT stipulations under grid fault conditions in various grid codes. The study examines the impact of PVs on the grid code development, offering a detailed and classified viewpoint on the FRT regulations and providing valuable details about the FRT capabilities of a common grid code to be used and referred. Consequently, this work proposes several grid-level design considerations to fulfill FRT requirements.
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    Modeling and assessment of the fault ride-through capabilities of grid supporting inverter-based microgrids
    (IEEE, 2020-03) Buraimoh, Elutunji; Davidson, Innocent E.
    Grid-connected micro-grids are subject to grid disturbances. This has undesirable effects on system operation. Riding through fault conditions is a crucial technical challenge. Evolving grid codes require micro-grids to possess fault ridethrough capabilities and support the grid voltage recovery to imitate the behavior of the traditional electrical power systems. The paper proposes two models of a grid supporting inverterbased microgrid; the first controlled as a current source with a parallel impedance suitable for grid feeding applications; the second regulated as a voltage source with a virtual impedance suitable for grid forming applications. The main objective of these two systems is to achieve controlled power delivery to the grid using grid voltage and frequency regulation. This paper discusses power interaction under steady states and transient conditions. Grid voltage parameters, such as amplitude, phase angle, and frequency, are estimated using a synchronization system, as these are necessary for precise active and reactive power control. Results obtained provide an understanding of grid fault impact on grid supporting systems and fault ridethrough compliance and evaluates the impacts of the virtual impedances on fault ride through and power interaction.
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    Short-term wind variability analysis of Afe Babalola University
    (IEEE, 2020-03) Ayamolowo, Oladimeji Joseph; Omo-Irabor, Benedict; Buraimoh, Elutunji; Davidson, Innocent E.
    The increasing damaging effect of fossil fueled generators has necessitated the need for diversification into renewable energy sources. However, these abundant renewable sources are limited by their variability at various seasons which often results in stochastic output power. In this paper, short term variability analysis of wind resource in Afe Babalola University is presented from January 2018 to December 2018. Wind speed data were collected using the anemometer at various times and sites within this period and used to estimate the potential of wind resource in ABUAD. The results showed that the wind energy resource is higher between the months of April to September, but insufficient to meet the energy need of ABUAD, hence necessitating the need of a hybrid generating system. An optimized hybrid system comprising of one, 1650kW wind turbine, 2000kW PV panels, 1900kW Diesel generator, 2000kW Converter, and one Trojan T-105 battery was obtained from HOMER software, with levelized cost of energy (COE) of 0.414$/yr and Net Present Cost(NPC) of $41,353,948.