Browsing by Author "Meral, Mehmet Emin"

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Automation of Ball Mills Using in Mine Concentration Plants and Efficiency Analysis
(2014) Baykan, Erdinç; Meral, Mehmet Emin
Maden işleme tesisleri, ticari değer taşıyan cevherleri kaynağından alarak hammadde olarak kullanılabilir hale getiren endüstriyel tesislerdir. Cevher işlemenin önemli aşamalarından biri de öğütmedir. Öğütme, kısaca boyut küçültme olarak tanımlanabilir ve değirmenler vasıtasıyla gerçekleştirilir. Bu çalışmada örnek bir Bakır Konsantrasyon Tesisi Öğütme Ünitesinde kullanılan bir bilyalı değirmenin Programlanabilir Lojik Kontrolör (PLC ) ve Uzaktan Kontrol ve Gözleme Sistemi ( SCADA) ile otomasyon tasarımı gerçekleştirilmiştir. Otomasyonlu çalışma ile otomasyonsuz çalışma arasında karşılaştırmalar yapılarak verimlilik analizleri yapılmıştır. Bilyalı değirmenin verimli çalışması, fabrikanın maliyetleri açısından kritiktir. Bilyalı değirmenin uygun değerlerde en verimli şekilde çalınmasının sağlanması ve tüketilen elektrik enerjisinden mümkün olduğunca tasarruf edilmesi, değirmenin kontrollü çalışmasına fazlasıyla bağlıdır. Bu da ancak oldukça iyi tasarlanmış ve programlanmış PLC ve SCADA sisteminin kullanılması ile mümkün olabilmektedir. PLC olarak SIEMENS S7 300 serisi ve Operatör panel (HMI) olarak SIEMENS MP 277 tipi panel kullanılmıştır. Gerçekleştirilen verimlilik analizleri sonucu, bilyalı değirmen için iyi tasarlanmış bir otomasyon sistemi ile verimlerin yükseldiği ve birim maliyetlerin düştüğü görülmüştür. Tasarlanan otomasyon sistemi geliştirilmeye ve bazı yeniliklerle benzer tesislerde de kullanıma uygundur.
A Comprehensive Survey on Control Strategies of Distributed Generation Power Systems Under Normal and Abnormal Conditions
(Pergamon-elsevier Science Ltd, 2019) Meral, Mehmet Emin; Celik, Dogan
High energy demand, low cost requirements and higher reliability requirements increase the importance of distributed generation power systems (DGPSs). The large capacity DGPSs requires high performance control algorithms and synchronization techniques based positive-negative sequence (PNS) extractors to fulfil system reliability and power quality requirements under not only during normal operating conditions, but also under unbalanced grid conditions. The power quality problems caused by voltage unbalances, voltage sag/swell, voltage fluctuations, phase faults and harmonic distortions have critical influences on control of power converter devices interfaced DGPSs. In literature studies, novel control strategies with phase locked loops (PLLs) techniques based PNS extractors are used to overcome these problems. In this paper, a comprehensive review on various advanced control strategies and PNS extractors for interlinking three phase inverter in the DGPSs are comprehensively investigated and discussed under normal and abnormal conditions. Several PNS extractors have been overviewed to produce the sequences components required for reference current generation (RCG). The theoretical assessment of the RCG based flexible control strategies and overcurrent limitation control are also comprehensively analysed, surveyed and compared in detail to deal with power quality problems. Comparative analyses for PNS extractors, voltage current regulation controllers and RCG based control strategies have been detailed presented and analysed. The presented detailed overview can be useful to researchers studying impact of normal and abnormal conditions on various control strategies with or without any using PLLs based PNS extractors for three-phase inverters interfaced DGPSs. (C) 2018 Elsevier Ltd. All rights reserved.
A Coordinated Virtual Impedance Control Scheme for Three Phase Four Leg Inverters of Electric Vehicle To Grid (V2g)
(Pergamon-elsevier Science Ltd, 2022) Celik, Dogan; Meral, Mehmet Emin
The three-phase four-leg (3p4L) inverter can be utilized to interface electric vehicles (EVs) with the distribution networks. Vehicle to grid (V2G) inverters are employed to charge EVs from the utility grid as well as compensating harmonics and unbalanced voltages & currents on demand. Motivated by this scenario, this paper proposes a coordinated virtual impedance control scheme for a vehicle to grid three phase four leg (V2G 3p4L) inverter. The proposed control scheme achieves simultaneously multifunctional objectives consisting of effective and good harmonic rejection capability, power sharing among V2G 3p4L inverter units with a smaller error, reactive power/voltage support during load power changes and balanced/unbalanced voltage sag conditions. An independently neutral current control approach is proposed for the fourth leg of the V2G 3p4L inverter to regulate the DC-link along with neutral current control capability. Besides, the proposed control scheme achieves grid connected mode (GCM) or standalone mode (SAM) operation capability as well as fulfilling smooth transition between operation modes without reconstructing control structure. Compared to well-known control schemes in the literature, synchronization during operation modes is also achieved without transients in voltage and current. Comprehensive tests under various scenarios validate the excellence of the proposed control scheme over existing methods.(c) 2022 Elsevier Ltd. All rights reserved.
Current Control Based Power Management Strategy for Distributed Power Generation System
(Pergamon-elsevier Science Ltd, 2019) Celik, Dogan; Meral, Mehmet Emin
The integration of renewable energy sources (RES) based distributed generation (DG) systems into electric grid has many challenges such as synchronization, control, power management (PM) and power quality problems. This paper proposes a references current generator (RCG) based PM strategy to control three phase inverter and manage power flow among the DG energy sources, electric grid and load demand under balanced and unbalanced grid conditions. The amplitudes of active and reactive power oscillations are also eliminated and controlled through only one flexible control parameter (FCP) under grid faults and harmonic distortions. Compared with previous similar studies, one of the important contributions is capable to inject maximum active power and minimum reactive power into electric grid and load at inverter power capacity under grid faults Another contribution is to extract the positive and negative sequence (PNS) voltage and current components with the improved fast and robust dual adaptive filters based phase locked loop (DAF-PLL). Fractional order proportional integral (FOPI) is selected as an attractive solution for AC current regulation to exhibit fast transient response and to achieve zero steady-state errors as compared with conventional current regulation controllers in synchronous or stationary frames.
Development of a New High Voltage Detector Compatiblewith Scada
(2022) Gerehan, Kadir; Meral, Mehmet Emin
Bu tez kapsamında IEC 61243-5 ve TS-EN 61243-5 standartları ile özellikleri belirlenmiş Kapasitif Gerilim Göstergesi (GAS) olarak çalışabilen bir cihaz tasarlanmış, modellenmiş ve gerçekleştirilmiştir. Yüksek gerilim kapasitif göstergeleri, kapasitif gerilim bölücüler aracılığıyla baradan aldığı gerilim bilgisini işleyerek sistemde gerilimin olup olmadığı hakkında görsel olarak uyarı verebilen cihazlardır. GAS cihazlarının kontaklı tipleri, kapasitif mesnet izolatörlerinden aldığı gerilim sinyalini hem görsel hem sayısal (dijital) bilgi olarak verebilen cihazlardır. Aynı zamanda Kontaklı Gerilim Göstergeleri yardımcı beslemeye ihtiyaç duyarlar. Bu cihazlar üç faz için ayrı ayrı sayısal(dijital) bilgi üretmemektedirler. Bu tez çalışmasında 3 faz için ayrı ayrı bağımsız dijital çıkış verebilen ve yardımcı besleme ile çalışabilen bir Yüksek Gerilim Algılayıcı tasarlanmıştır. Tasarlanıp geliştirilen bu cihazla her faz için yüksek gerilimin ölçüm ve takibinin yapılabilmesinin yanı sıra sistem ve can güvenliği hedeflenmiştir. Geliştirilen cihazın hassas ölçüm alabilmesi için kapasitif mesnet izolatörlerinden alınan L1, L2 ve L3 fazları ile birlikte sisteme ait toprak ucunun da cihaza bağlanması gerekmektedir. Hem yardımcı besleme hem de toprak bağlantısından dolayı, bu iki sistemin izole edilmemesi durumunda bu tip bir cihazda kaçak akıma sebep olur. Bu nedenle, cihaz için ayrıca izole bir şekilde çalışabilen Anahtarlamalı Güç Kaynağı (Switch Mode Power Supply-SMPS) devresi tasarlanmıştır. Anahtar kelimeler: Faz algılayıcı, Gerilim göstergesi, Kapasitif gerilim bölücü, SCADA, Yüksek gerilim.
Development of Inverter Control Methods for Microgrid Applications
(2020) Çelik, Doğan; Meral, Mehmet Emin
Yenilenebilir enerji kaynakları (YEK) güç elektroniği elemanları vasıtasıyla yüke ve elektrik şebekesine daha fazla bağlanmasıyla birlikte, mikro şebekeler (microgrid-MG) aktif ve reaktif güç salınımları, aktif ve reaktif güç paylaşımı, arıza sonrası katkı yeteneği ve aşırı akım problemi gibi çeşitli zorluklarla başa çıkmak için yeterli düzeyde yardımcı hizmetleri sağlamalıdır. Bu yüzden mikro şebekeler için tek veya paralel çalışan yenilenebilir enerji kaynaklı güç elektroniği cihazları kontrolü önemli bir araştırma konusu haline gelip ve kritik öneme sahip olmaktadır. Bu bağlamda, bu tez çalışmasının amacı MG uygulamalarında ada modunda ve şebekeye bağlı tek üç fazlı evirici ve paralel üç fazlı evirici topolojileri için kontrol stratejilerini geliştirmektir. Bu tez çalışmasında, i) evirici topolojilerinin şebeke ile etkileşiminin iyileştirilmesi, ii) güç/akım kalitesinin artırılması, iii) gerilim kararlılığının artırılması, iv) akım, gerilim ve frekans kontrolünün yapılması, v) aşırı akım korumasının sağlanması, vi) aktif ve reaktif güç salınımlarının elimine edilmesi, vii) gerilim desteğinin sağlanması, viii) reaktif güç desteğinin sağlanması ve ix) eviriciler arasında güç paylaşımının sağlanmasına yönelik; esnek kontrol, gerilim destekli kontrol, sıralı bileşenler tabanlı düşüm kontrolü ve öngörülü akım kontrol gibi çeşitli kontrol stratejileri önerilmiştir. Önerilen kontrol stratejilerinin etkinliği ve doğruluğu PSCAD/EMTDC ve MATLAB yazılım programları kullanılarak detaylı benzetim çalışmaları ve numerik analizler ile desteklenmiştir. Ayrıca DSP tabanlı PIL kullanılarak önerilen yöntemlerin etkinliği gerçek zamanlı sonuçlarla doğrulanmıştır.
Dsogi-Pll Based Power Control Method To Mitigate Control Errors Under Disturbances of Grid Connected Hybrid Renewable Power Systems
(Vsb-technical Univ Ostrava, 2018) Meral, Mehmet Emin; Celik, Dogan
The control of power converter devices is one of the main research lines in interfaced renewable energy sources, such as solar cells and wind turbines. Therefore, suitable control algorithms should be designed in order to regulate power or current properly and attain a good power quality for some disturbances, such as voltage sag/swell, voltage unbalances and fluctuations, long interruptions, and harmonics. Various synchronisation techniques based control strategies are implemented for the hybrid power system applications under unbalanced conditions in literature studies. In this paper, synchronisation algorithms based Proportional-Resonant (PR) power/current controller is applied to the hybrid power system (solar cell + wind turbine + grid), and Dual Second Order Generalized Integrator-Phase Locked Loop (DSOGI-PLL) based PR controller in stationary reference frame provides a solution to overcome these problems. The influence of various cases, such as unbalance, and harmonic conditions, is examined, analysed and compared to the PR controllers based on DSOGI-PLL and SRF-PLL. The results verify the effectiveness and correctness of the proposed DSOGI-PLL based power control method.
A Flexible Control Strategy With Overcurrent Limitation in Distributed Generation Systems
(Elsevier Sci Ltd, 2019) Celik, Dogan; Meral, Mehmet Emin
Distributed Generation (DG) systems are typically interfaced with distribution lines by modern power converter devices, which their controllers and dynamic behaviours are significantly influenced by unbalanced grid faults. The active and reactive power control with positive-negative sequences (PNS) is one of fundamental of power converter control under grid fault conditions. This paper proposes a reference current generator (RCG) based flexible power control strategy to enable regulation of active and reactive power with minimizing active and reactive power oscillations. Current limitation control is embedded into the RCG in order to keep maximum current injection in safety limitation for overcurrent protection under grid faults and harmonic distortions. The proposed control strategy has been also accomplished maximum active power and minimum reactive power transfer capability to electric grid. The analytical expression of active and reactive power oscillations depending on flexible control parameters are comprehensively investigated as theoretically and examined with simulations. Fractional order proportional integral (FOPI) controller is preferred to minimise steady state error of AC current regulation and provide faster processing time instead of conventional PI and proportional resonant (PR) controllers. An important contribution for similar previous studies is that PNS voltage and current components are separated by dual average filter based phase locked loop (DAPLL) which is firstly proposed in this paper. The performance of proposed controller is compared with multiple complex-coefficients filter (MCCF-PLL) based controller. Theoretical analysis and simulation results verify the correctness and effectiveness of the proposed solution.
An Improved Sequence Based Control Strategy for Three Phase Grid Interfaced Inverter Systems
(Ieee, 2019) Celik, Dogan; Meral, Mehmet Emin
Power electronic devices are critical components for interfacing renewable energy sources (RES) to the utility grids. The safe and proper operation of the grid-connected inverter (GCI) becomes a substantial challenging under grid fault conditions. For this purpose, this paper presents a sequence based control strategy to enhance the dynamic behavior of the GCI under unbalanced grid voltages. The main contribution to existing methods, dual adaptive filter based sequence extraction method is proposed to fast separate positive and negative sequence of unbalanced three phase signals. The proposed sequence extractor reduces settling time significantly, which is less than one cycle time delay. This novelty of the improved sequence extractor is also compared to another extractor based on fast Fourier transform (FFT). A set of simulation results has been presented to verify the effectiveness of the proposed sequence based control strategy.
Improvement of Current and Voltage Problems Occurring on Solid State Transformer Components
(2025) Adam, Khalil Youssouf; Meral, Mehmet Emin
Dağıtım sistemi ve yenilenebilir enerjinin yaygınlaşması sonucu; güç kalitesi, ters ve geri güç akış problemleri gibi birçok zorluklarla karşılaşılmaya başlanmıştır. Bu tez çalışması, Kademeli H-Köprü Tabanlı Katı Hal Transformatörlerinin (SST) katlarında ve bileşenlerinde meydana gelen akım ve gerilim problemlerini incelemeyi amaçlamaktadır. SST'lerin katları arasında AC/DC dönüştürücü katı, çift aktif köprü katı ile çift aktif köprünün merkezinde bulunan yüksek frekanslı transformatör katı ve bileşenleri arasında H-köprüsü modülleri, güç elektroniği dönüştürücüleri, yüksek frekanslı transformatör ve kontrol sistemleri bulunmaktadır. Bu bileşenlerde meydana gelen problemler; dengesiz akımlar, harmonikler ve aşırı yükleme gibi akım problemlerinin yanı sıra gerilim dalgalanmaları ve gerilim düşmeleri, aşırı gerilim ve gerilim dengesizliği şeklinde sıralanabilirler. Bu çalışmadaki devrelerin modellenmesi ve benzetimi için PSCAD/EMTDC programı kullanmıştır. Akım ve gerilim problemlerinin iyileştirilmesi amacıyla farklı anahtarlama ve denetleyicileri kullanılarak analizler ve karşılaştırmalar yapılmış ve öneriler sunulmaya çalışılmıştır.
Improving Voltage Quality With D-Statcom in Distributionnetworks
(2018) Çakmak, Fevzi; Meral, Mehmet Emin
Bu tez çalışmasında, dağıtım şebekelerinde D-STATKOM ile gerilim kalitesinin iyileştirilmesi üzerine çalışmalar yapılmış olup, D-STATKOM' un denetim algoritması için sabit parametreli Oransal + İntegral (PI) ve Paralel Rezonans (PR) denetleyiciler kullanılmıştır. Her iki model performansları PSCAD/EMTDC benzetim programı karşılaştırılmıştır. Elde edilen teorik ve benzetim çalışması sonuçlarına göre, şebekeye paralel olarak bağlanan D-STATKOM' un hem PI yöntemi, hem de PR yöntemi ile sistemde arıza veya herhangi bir başka sebeple oluşan kısa süreli gerilim düşümlerine (gerilim çukuru) çok kısa bir sürede tepki verdiği ve bara geriliminin anma değerlerine yakın değerlere çıkmasını sağladığı, böylece gerilim çökmesinden dolayı oluşacak aksamaları giderdiği ve PI ile PR denetleyici kullanan DSTATKOM' ların birbirine göre kısmi avantaj ve dezavantajları bulunduğu sonucuna varılmıştır.
Investigation and Analysis of Effective Approaches, Opportunities, Bottlenecks and Future Potential Capabilities for Digitalization of Energy Systems and Sustainable Development Goals
(Elsevier Science Sa, 2022) Celik, Dogan; Meral, Mehmet Emin; Waseem, Muhammad
Taking into consideration of substantial role of energy system and sustainable development goals (SDGs) in modern society, it is critical to analyse current situation and forthcoming renewable energy development strategies under the impact of COVID-19. For this purpose, this paper provides significant new insights to assess effective approaches, opportunities, challenges and future potential capabilities for the development of energy systems and SDGs under on-going pandemic and in case of a future global crisis. The digital energy systems with Industry 4.0 (I4.0), which provide noteworthy solutions such as enhancing energy efficiency policy, providing clean, secure and efficient energy and achieving SDG targets, has been discussed and evaluated. Integration of the smart grid (SG) architecture with blockchain-Internet of Things (IoT)-based technologies is also offered. Alongside the various discussions, short-term, mid-term and long-term plans have been suggested in determining the well-defined renewable energy development and SDGs targets, struggling with climate change, transition to a more sustainable energy future and reaching global net-zero emissions. To achieve SDGs and provide more strong and sustainable energy systems under the continuing pandemic and in case of potential risk of forthcoming global crisis, this paper reveals significant perceptions that inform politicians and legislators in performing successful policy decisions.
Kalman Filter-Based Super-Twisting Sliding Mode Control of Shunt Active Power Filter for Electric Vehicle Charging Station Applications
(Ieee-inst Electrical Electronics Engineers inc, 2023) Celik, Dogan; Ahmed, Hafiz; Meral, Mehmet Emin
Electric vehicle (EV) charging stations draw nonlinear currents, which makes the distribution network unbalanced, distorted, and results in power quality (PQ) issues. These PQ issues are mitigated in this work through high-performance control of the shunt active power filter (SAPF). In the proposed method, a linear Kalman filter (LKF) has been applied to grid voltage and load current signals for harmonic and disturbance robust estimation purpose. Unlike the conventionally used orthogonal vector model, in this work, phase angle vector model together with a simple to tune phase-locked loop (PLL) has been considered for the LKF implementation. DC-link voltage regulation and charging of the DC-link capacitor has been obtained by proposing a Luenberger observer-based super twisting sliding mode control (ST-SMC), which has fast dynamic response and lower voltage ripples compared to similar other existing control methods. This results in significant reduction in size, cost and loss together with lifetime enhancement of the DC-link capacitor. Rigorous sensitivity analysis is conducted to analyze the robustness of the developed method. The proposed control technique achieves fast response time and satisfy the harmonic requirements as specified in the IEEE Std. 519 under various grid and load disturbances. Comparative quasi-real time validation results are presented by using digital signal processor (DSP) based processor-in-the-loop (PIL) with another recently proposed control strategy to verify the performance enhancement by the developed method.
Mitigation of Dc-Link Voltage Oscillations To Reduce Size of Dc-Side Capacitor and Improve Lifetime of Power Converter
(Elsevier Science Sa, 2021) Meral, Mehmet Emin; Celik, Dogan
Voltage and current oscillations have become a primary power quality issues for DC and AC systems. In this respect, this paper presents a new control scheme for analytical implementation of reference current generator (RCG) based power control strategies to eliminate oscillations both DC and AC sides. Benchmarking of the RCG based power control strategies are examined in terms of elimination of the power oscillations, reducing DC-link voltage oscillations, avoiding DC-side overvoltage and preventing AC-side overcurrent. Compared to the existing strategies, controlling reference active power is provided with a closed-loop control system. A noteworthy contribution of this paper is to eliminate active power oscillations, which is an effective method to suppress the DC-link voltage oscillations resulting in third-order harmonic at the grid side. This helps to reduce the size of the DC-side capacitor and also improves the lifetime of the inverter, safety and stability of the grid connected primary energy resources (PERs). Detailed comparative analysis with the most recent strategies have been performed for state of the art proposed control scheme. Finally, various case studies are presented to support the proposed control scheme can mitigate the DC-link voltage oscillations, effectively.
Modified Sliding-Mode Controller for the Line-Commutated Converters of Back-To HVDC Systems
(Springer Heidelberg, 2025) Sular, Adem; Meral, Mehmet Emin
Line-commutated converter (LCC) high-voltage direct current (HVDC) systems are currently the most attractive valve converter topology for large-scale HVDC networks due to their high efficiency, low initial installation cost, low power loss, high system stability, and high reliability. This study presents a detailed study of LCC back-to-back HVDC converter stations, identifies the major components of such systems for parameter calculations and supports them with mathematical operations, explains the control methods of the rectifier and inverter units, and proposes a new controller structure. To elucidate its advantages, the proposed controller structure for LCC-HVDC converter stations is compared with other controller structures, namely, the classical proportional-integral (PI) controller and the anti-windup PI controller. The simulation results are obtained from the PSCAD/EMTDC software package. The comparison of the system results, such as settling times and maximum and minimum values for the three controllers, indicates that the proposed modified sliding-mode-based controller (MSMBC) outperforms the two other controllers in all aspects. Therefore, the proposed MSMBC makes highly important contributions to LCC-HVDC converter systems and is superior to other controllers due to its significant advantages.
Multi-Objective Control Scheme for Operation of Parallel Inverter-Based Microgrids During Asymmetrical Grid Faults
(inst Engineering Technology-iet, 2020) Celik, Dogan; Meral, Mehmet Emin
The growing interest in connecting more distributed generation (DG) units to the utility grid, microgrids deal with the various challenges to satisfy a sufficient level of ancillary services such as active power oscillations (APOs), reactive power oscillations (RPOs), fault ride-through (FRT) capability, and overcurrent problem. Hence, for parallel operated grid-connected inverters (GCIs) based MG, this study presents a multi-objective control scheme that simultaneously ensures elimination of the collective APOs/RPOs at point of common coupling (PCC), overcurrent protection and reactive power injection. One of the significant parts of this study compared with similar existing studies is that provides reactive power support capability to fulfil the FRT requirements of the grid-connected multi-DG units and to remain grid-connected during asymmetrical grid faults. A current restraining control is also presented to ensure the safe operation of the MG system and to avoid overcurrent. The cancellation of the collective APOs and RPOs at the PCC for parallel operation of the GCIs has been achieved by using adjustable control coefficients and demonstrated with theoretical analyses in detail. Extensive case studies are presented and discussed to demonstrate the performance of the proposed ideas and to meet the shortcomings of the previous studies.
A Novel Control Strategy for Grid Connected Distributed Generation System To Maximize Power Delivery Capability
(Pergamon-elsevier Science Ltd, 2019) Celik, Dogan; Meral, Mehmet Emin
The energy sector is moving toward an extensive utilization of hybrid renewable energy resources (HRES), which are commonly interfaced to the utility grid through the inverters. Therefore, the proper operation of the grid connected inverter has brought major requirements under unbalanced grid faults. In this regard, this paper proposes a novel control strategy to maximize power delivery capability of the grid connected inverter interfaced distributed generation (DG) systems. The proposed control strategy achieves power flow and power sharing among DG units, the utility grid and load demand with a power management system. Minimization and controllability of active-reactive power oscillations are fulfilled with a flexible control parameter. An improved positive and negative sequence extractor (PNS) is proposed to separate sequence components for use in the reference current generator. The proposed PNS extractor provides a significant improvement in terms of response time as less than one period-(18 ms) compared to existing techniques. The proposed control strategy achieves also high performance with lower total harmonic distortion about 0.5%. Another novelty of this paper is that a current limitation control is inserted into the reference current generator for overcurrent protection. Comparative evaluation of the proposed control strategy is performed and confirmed under various cases. (C) 2019 Elsevier Ltd. All rights reserved.
A Novel Current Control Strategy for Grid Connected Renewable Energy Source Inverters
(Gazi Univ, Fac Engineering Architecture, 2020) Meral, Mehmet Emin; Celik, Dogan
Unbalanced grid voltages include positive and negative sequence (PNS) components. In particular, the negative sequence components that cause oscillations on the control signals, significantly affect the performance of the grid-connected renewable energy source inverters (RESI). In this study, proportional complex integrator (PCI) based current controller is proposed to deal with the disadvantages such as slow dynamic response, steady-state errors and complex structure of the proportional integral (PI) based dual current controller used for the control of grid connected RESI under non-ideal grid voltage conditions. The reference currents based on the active-reactive power reference signals, PNS components and the flexible control parameter are generated for use in control loops. The relationship between the active and reactive power oscillations, which are caused by non-ideal grid conditions, are comprehensively analysed and controlled with a flexible control parameter. An important contribution to similar previous studies is that the PNS voltage and current components required for the reference current generation are separated by the proposed fast and robust dual average filter based phase locked loop (DAPLL). The performance of the proposed PCI-based current control strategy is compared and tested with the PI-based dual current control strategy using various case studies.
Open Unified Power Quality Conditioner With Control Based on Enhanced Phase Locked Loop
(inst Engineering Technology-iet, 2013) Teke, Ahmet; Meral, Mehmet Emin; Cuma, Mehmet Ugras; Tumay, Mehmet; Bayindir, Kamil Cagatay
Open unified power quality conditioner (UPQC) offers different power quality levels with different electricity bill to their users. OPEN UPQC has more flexible modularity than traditional UPQC for field applications. OPEN UPQC consists of two controlled pulse-width modulated shunt and series inverters that have no common DC link. Shunt inverter eliminates current harmonics originating from non-linear load side and series inverter mitigates voltage sag/swell at the point of common coupling caused from faults on transmission system. In this study, controllers for both shunt and series inverters are based on enhanced phase locked loop (E-PLL) and non-linear adaptive filter. For the controller of shunt inverter, proportional integrator controller-based DC-link control strategy is adapted to E-PLL. A fast sag/swell detection method is also presented. Functionalities of OPEN-UPQC system is deeply analysed and tested through simulation studies with power system computer aided design/electromagnetic transients DC analysis program. The test results verify that OPEN UPQC achieves good performance for mitigating the effects of voltage sag/swell and suppressing the load current harmonics.
An Overvoltage and Undervoltage Prevention Control for Superconducting Magnetic Energy Storage Based Power Converter Connected To a Weak Grid
(Ieee, 2021) Celik, Dogan; Meral, Mehmet Emin
With the growing usage of primary energy resources (PERs), energy storage technologies have been required to fulfill a balance between supply and demand. Therefore, a control scheme combining superconducting magnetic energy storage (SMES) control and overvoltage and under-voltage prevention control is proposed for SMES based inverter connected to utility grid under various grid voltage disturbances. One of the contributions of this paper is to maximize positive voltage sequence and minimize negative voltage sequences to eliminate the voltage and current imbalances. Besides, the control of the SMES has been performed depending on the regulation of the DC-link capacitor voltage. Also, the voltage support guarantees the safe operation of the three phase inverter. Theoretical analysis and PSCAD/EMTDC based results are conducted to show the feasibility of the voltage and power quality improvement.