Browsing by Author "Celik, Dogan"

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An Advanced Control Strategy for Power Flow Management, Optimal Dc Capacitor Utilization and Compensating Harmonics in Fuel Cell Electric Vehicle Powertrain Converters
(Pergamon-elsevier Science Ltd, 2024) Celik, Dogan
Electric vehicles (EVs), particularly fuel cell electric vehicles (FCEVs) powered by hydrogen, are gaining significant attention due to their environmental benefits, minimal maintenance, and superior motor efficiency. However, the integration of power converters into EVs results in challenges related to power quality (PQ), including voltage and current harmonics, power factor, power losses, and DC-link ripples. This paper proposes a comprehensive control strategy to enhance power management through active-reactive power control, achieving unity power factor (UPF) operation, compensating for reactive power load demand, stabilizing DC-link voltage, and mitigating harmonics to meet IEEE standards in FCEV powertrain converters. This control strategy incorporates advanced techniques, including a multiple orthogonal vector (MOV)-based linear Kalman filter (LKF) for precise harmonic current extraction and a sliding mode-based proportional-integral (SM-PI) control approach for DC capacitor voltage regulation. These techniques ensure efficient operation, optimal DC capacitor utilization, and accurate DC-link voltage tracking, leading to improved system performance and stability. The proposed control method effectively compensates for reactive power, reducing the grid's burden compared to the conventional methods. The proposed control strategy significantly reduces total harmonic distortion (THD) in grid currents to between 0.30% and 0.85%, well below the 5% IEEE-519 standard, and improves the power factor to near unity (0.989-1.0) compared to the conventional method's 0.81-0.992. Additionally, DC-link voltage stability has been enhanced, with voltage ripple reduced from Delta v = 10.1 V to Delta v = 2.0 V, achieving faster response times under 50 ms, reduced overshoot, and improved PQ. Theoretical analyses and the proposed approach are validated through simulations and processor-in-the-loop (PIL) semi-experiments conducted on the digital signal processor (DSP) TMS320F2835 board, demonstrating enhanced reliability, efficiency, and compatibility with the grid for FCEV powertrain systems. This work contributes to the advancement of FCEV technology by addressing critical challenges in PQ and system efficiency.
Benchmarking Simulation and Theory of Various Plls Produce Orthogonal Signals Under Abnormal Electric Grid Conditions
(Springer, 2018) Meral, M. Emin; Celik, Dogan
The voltage or current harmonics and unbalancing have severe influence on control of various applications such as power quality devices, distributed generation systems, power converter devices, electric vehicle chargers and electric motors. Orthogonal d-q signals are significantly a part of controller for these applications. This paper proposes a new synchronization method based on integration average filter (AF) into conventional phase locked loop (PLL) in order to attenuate negative effect of voltage harmonics and unbalanced on orthogonal d-q signals for controller. Although some advanced techniques in the literature ensure good performances, uses of multiple filters reduce dynamic response and suffer from computational burden. The proposed improved AF-PLL has simple structure and implementation. It provides fast phase detection, fast dynamic response and removes ripple errors of voltage unbalance and harmonics. The performance of the filter-based PLL is evaluated in terms of balanced, unbalanced condition and harmonics distortion. The effectiveness and reliability of the proposed AF-PLL are demonstrated and discussed by means of comparative conventional PLL and advanced PLL in the literature. PSCAD/EMTDC is used for simulation and examination of all PLLs.
Comparison of Srf/Pi- and Strf/Pr-based Power Controllers for Grid-Tied Distributed Generation Systems
(Springer, 2018) Meral, M. Emin; Celik, Dogan
Grid-tied distributed generation (DG) system-based renewable energy sources such as wind, sun and hydrogen have recently gained a large attention due mainly to environmental issues. In this study, to provide energy for various loads, it is connected to the common direct current bus system after DG system-based fuel cell and solar cell are modeled and simulated. In order to synchronize DG system sources to utility grid, park transformation-based three-phase phase-locked loop technique is used, which is one of the most common methods in the literature. Power control method-based synchronous reference frame with proportional integral controller or stationary reference frame with proportional resonant current controller is used in the DG systems. The performances of two controllers are discussed in this study. Simulation results are obtained for various scenarios at the designed and created simulation model of DG + Grid + Load system. The system is modeled and simulated by using PSCAD/EMTDC software package.
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 EV Charging Topologies and Communication Protocols for Resilient Grid Integration and V2X Applications in Sustainable Energy Systems
(Elsevier, 2025) Khan, Muhammad Adnan; Celik, Dogan; Waseem, Muhammad; Meral, Mehmet Emin
The global shift towards eco-friendly refuelling infrastructure, driven by the electrification of vehicles, has catalyzed extensive research and development to enhance electric vehicle (EV) charging stations for cleaner production, sustainable development, and overall sustainability. Energy storage systems (ESSs) are pivotal in this transition, essential for harmonizing power generation and consumption, especially with the growing integration of renewable energy sources, smart technologies, and long-range EVs. By fostering synergies between transportation systems and electricity networks, these advancements are instrumental in advancing a net-zero energy system, promoting greater sustainability and energy efficiency. Power electronics converters (PECs) and their associated controls and optimizations are crucial for enhancing the value of battery ESSs by providing efficient and cost-effective technologies. This comprehensive review explores various papers and technical reports focused on EV charging topologies and methodologies, dissecting their benefits and analysing the challenges of PEC topologies, EV charging infrastructures, EV standards and protocols, and grid ancillary services, as well as providing a detailed analysis of diverse charging scenarios. Motivated by the potential of PECs and ESSs to enhance the efficiency and cost-effectiveness of EV charging for cleaner production, this paper comprehensively reviews existing literature and technical reports. Challenges and suggestions are centred around the impact of electric vehicle grid integration (EVGI) on the power grid, along with an exploration of the challenges and prospects for future EVGI development trends and EV charging technologies. Furthermore, the paper delves into the technical aspects, issues, and ongoing progress of state-of-the-art charging methods and control strategies in the EV charging system. The challenges and recommendations presented in this paper are closely aligned with the latest available technologies, encompassing academic research contributions and real-world EV charging station projects operational across the globe, all aimed at advancing cleaner production, sustainable development, and overall sustainability in the transport sector.
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.
Enhanced Control of Superconducting Magnetic Energy Storage Integrated Upqc for Power Quality Improvement in Ev Charging Station
(Elsevier, 2023) Celik, Dogan; Ahmed, Hafiz
Distribution-grid connected electric vehicle charging stations draw nonlinear current, which causes power quality issues including harmonic distortion, DC-link fluctuation etc. Recent literature found that a unified power quality conditioner with superconducting magnetic energy storage (UPQC-SMES) can alleviate charging induced power quality issues. However, the performance improvement can be greatly enhanced by suitably designed control strategy. In this paper, an effective control approach is proposed for the UPQC-SMES system. In the proposed method, an all-pass filter based quasi type-1 phase-locked loop is proposed, which can robustly detect voltage sag/swell for the control of UPQCs series converter. A robust sequence estimator based on exponential forgetting factor cost function is developed for nonlinear load current sequence estimation to be used inside UPQCs parallel converter control system. Finally, a nonlinear proportional-integral controller is applied to make the system fast responsive with lower DC-link ripple compared to a conventional linear proportional-integral controller. The combined use of SMES and nonlinear proportional-integral controller can significantly eliminate the voltage fluctuation in DC-link and reduce the size and cost of the DC-link capacitor, making the system more efficient. To enable grid-friendly charging operation, the proposed control strategy considers harmonic currents elimination, reactive power compensation, power factor improvement, restoring sags and swells of the grid voltage and mitigation of DC-link voltage fluctuations. Comparative verification results show that the total harmonic distortion by the proposed method always remained between 1.0 similar to 1.5% irrespective of the test cases, while the conventional approach could contain the distortion to less than 5% in some cases only.
Enhanced Upqc Control Scheme for Power Quality Improvement in Wave Energy Driven Pmsg System
(IEEE-Inst Electrical Electronics Engineers Inc, 2025) Ahmed, Hafiz; Celik, Dogan
This article focuses on enhancing power quality (PQ) in a wave energy-driven permanent magnet synchronous generator (PMSG) system with unbalanced and highly inductive nonlinear loads using a unified power quality conditioner (UPQC). Our proposed control system improves voltage quality, compensates for reactive power, and mitigates harmonics. It ensures constant voltage amplitudes during supply voltage faults, achieving harmonic rejection, reactive power compensation, and enhanced voltage quality through the UPQC's parallel converter. Compared to previous methods, we introduce a frequency-fixed second-order generalized integrator (FFSOGI) quasi-type-1 PLL for efficient load harmonics extraction and source voltage fault detection. Additionally, a robust nonlinear proportional-integral (N-PI) controller, with a feedforward term, regulates the DC-link voltage swiftly and mitigates fluctuations. Our approach ensures compliance with IEEE standards for source current and load voltage harmonics. Comprehensive PSCAD/EMTDC results, utilizing experimental torque and power data from a wave energy converter at the Australian Maritime College model test pool, highlight the advantages of our proposed approach over conventional methods.
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.
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.
Lyapunov Based Harmonic Compensation and Charging With Three Phase Shunt Active Power Filter in Electrical Vehicle Applications
(Elsevier Sci Ltd, 2022) Celik, Dogan
With the increasing proliferation of high-tech loads and electrical vehicle (EV) charging stations, shunt active power filters (SAPFs) are contemplated to play a growingly substantial role in power distribution and delivery. In this regard, this paper proposes a Lyapunov based harmonic compensation and charging with the operation of three-phase SAPF as interface EV applications and the electric grid. The proposed control algorithm provides effective harmonics mitigation capability under various non-linear loads (NLLs) groups and grid disturbances. A noteworthy contribution of this paper is that a Lyapunov based proportional integral with anti-windup (PI with AW) control is proposed to regulate oscillations of the DC-link voltage without increasing DC-link capacitor size. The proposed control algorithm offers comprehensive solutions with several improvements, novelties and features as: (i) keeping the total harmonic distortion (THD) of source currents below recommended IEEE-519 limits, (ii) extraction of reference current and voltage signals based on Lyapunov estimator (LE) with effective and good harmonic rejection capability, (iii) achieving good dynamic performance with utilizing a Lyapunov based PI with AW control for the DC-link capacitor voltage and (iv) eliminating the necessity of any high-pass or low-pass filters with utilizing LE based orthogonal signal generation (OSG). Besides, comparative analyses with previous studies are handled to examine improvements provided by the proposed control algorithm. The feasibility and effectiveness of the proposed control algorithm are confirmed by PSCAD/EMTDC environment and DSP based PIL quasi-real time results.
Microgrid Stability: a Comprehensive Review of Challenges, Trends, and Emerging Solutions
(Elsevier Sci Ltd, 2025) Khosravi, Nima; Celik, Dogan; Bevrani, Hassan; Echalih, Salwa
Microgrids (MGs) are increasingly vital in modern power systems, enabling localized energy management with high penetration of renewable energy sources (RESs) and distributed generation (DG). However, ensuring voltage and frequency stability in MGs remains a critical challenge due to the intermittent nature of RESs, fluctuating load demands, DG variability, and grid interaction disturbances. This comprehensive review systematically examines the causes of instability, advanced control strategies, and emerging trends in MG stability management. Key challenges, including RES intermittency, load variations, and fault-induced disruptions, are analyzed across operational modes (grid-connected and islanded), time scales (short-and long-term dynamics), and disturbance scales (small and large). The study evaluates control strategies for voltage stability such as reactive power management, generator control, load shedding, and distributed energy resource coordination and frequency stability, including classical PI/PID controllers, non-integer controllers, model-based, and model-free
Minimisation of Power Oscillations With a Novel Optimal Control Strategy for Distributed Generation Inverter Under Grid Faulty and Harmonic Networks
(inst Engineering Technology-iet, 2020) Emin Meral, Mehmet; Celik, Dogan
The increasing penetration of distributed generation (DG) inverters supplying power to the networks bring challenges to the power system under the grid faulty and harmonic grid since negative sequence components lead to double oscillations. Reference current generation (RCG)-based flexible control strategies ensure solutions to mitigate oscillations on the control signals and to maintain a more stable, secure and reliable power system operation. In this direction, this study proposes an RCG-based optimal control strategy that reduces oscillations of active and reactive power at optimal control parameter values and ensures minimum harmonic contents at the grid side under an unbalanced and harmonic distortion grid. The main cause of the power oscillations is comprehensively demonstrated, optimised and examined with numerical studies and theoretically. Control parameters are accurately selected by the courtesies of optimisation function to minimise power oscillations. A fast and robust third-order sinusoidal signal integrator (TOSSI) extracts positive-negative sequence components for the calculation of the RCG. To provide a fast transient response and achieve almost current tracking errors at a zero level, proportional complex integral (PCI) current regulation controller is selected. Various case studies have been performed to show the validity and availability of the proposed entire system, including flexible control, optimisation, TOSSI and PCI.
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.
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.